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European Journal of Pharmaceutical Sciences (18790720) 209
The efficacy of radiation therapy can decrease due to the inherent radioresistance of different tumor cells. Gadolinium shows significant potential as a radiosensitivity enhancer due to its high atomic number. In this study, a novel theranostic nanoprobe based on folic acid-conjugated gadolinium-loaded nanodroplets (FA-Gd-NDs) has been introduced for ultrasound imaging (USI)-guided radiation therapy of hepatocellular carcinoma. The ultrasound echogenicity evaluation of NDs, Gd release studies, biocompatibility test of Gd-NDs, colony assay, cellular uptake of NDs via fluorescence microscopy, and flow cytometry analysis were performed on Hepa1-6 cancer and L929 normal cell lines. Our results showed that synthesized NDs significantly enhanced ultrasound signal intensity in PBS solution and agarose gel phantom. MTT and clonogenic assays indicated that Gd-NDs substantially reduced the cell viability and also surviving fraction of Hepa1-6 cancer cells under US and X-ray exposure. Additionally, FA-Gd-NDs exhibited sensitization enhancement factor (SER) of 1.8 after concurrent exposure to US and X-ray. Fluorescence imaging demonstrated more internalization of FA-Gd-NDs into cancer cells in comparison with normal cells. According to flow cytometry results, the Gd-NDs and FA-Gd-NDs uptake by L929 cell line were 20 % and 28 %, respectively, while their uptake by Hepa1-6 cells was 60 % and 94 %, respectively. In conclusion, the synthesized novel theranostic nanoprobe shows great potential for enhancing the efficacy of radiation therapy and enabling ultrasound image-guided radiation therapy of cancers. © 2025
Wang, B. ,
Akteruzzaman, M. ,
Yu, S. ,
Ayatollahi mehrgardi, M. ,
Shannon, C. ,
Jin, C. ,
Fan, S. Talanta (00399140) 293
Glucose detection is vital for managing diabetes, monitoring metabolic disorders, and developing advanced biosensors. Electrochemical methods are widely used for glucose detection due to their sensitivity, portability, and low cost. However, these methods also have several limitations, such as interference from non-specific molecules, fouling of electrodes, and enzyme stability. Herein, to avoid external interference, we report a fast response cathodic electrochemiluminescence (ECL) glucose biosensor using a closed bipolar electrode (BPE) system with two separate cells (reporting cell and sensing cell). In this platform, Tris(2,2′-bipyridyl) ruthenium and K2S2O8 were used as the luminophore and co-reagent, respectively, to generate the cathodic ECL in the reporting cell, and a commercial test strip modified with GOx (glucose oxidase) and mediator served as the BPE anode to detect glucose in the sensing cell. The developed technique was able to determine glucose with a good correlation in the quantification of glucose in human serum samples with a fast response under a low potential, which avoided side reactions and was comparable to the commercial blood glucose meter. In addition, the sensing mechanism and working principle have been thoroughly studied, with the detailed discussion of the effect of oxygen and acetonitrile in influencing the ECL generation. Using this platform, glucose in the buffer was successfully quantified up to 18 mM, achieving a limit of detection of 3.8 mM and a linear concentration range between 4 and 12 mM. This electrochemical technique offers a simple and cost-effective strategy for point-of-care blood glucose testing without external interference, thereby opening up emerging opportunities in a broad range of sensing applications. © 2025 The Authors
Iranian Journal Of Science (27318095) 49(3)pp. 577-584
Fluorescent carbon dots (CDs) have attracted great attention for the biomedical applications as a new group of nanoparticles with high biocompatibility and interesting optical properties. In this study, the fluorescent CDs were synthesized by a biogenic hydrothermal method using Taxus baccata extract and ethylene diamine (EDA). The CDs, predominantly semi-spherical and smaller than 20 nm, exhibit high colloidal stability. They have a hydrodynamic size of 43.6 nm, a polydispersity index (PI) of 0.526, and a zeta potential of -56.7 mV. Their surface is rich in hydroxyl and carbonyl groups. They also exhibit fluorescence emission, with a quantum yield (QY) of 11.6% at 490 nm, when excited at 400 nm. The in vitro cytotoxicity assay on the human fibroblast (HFB) and umbilical vein endothelial (HUVEC) cells confirmed the biocompatibility of CDs. These CDs represent significant antibacterial effects on Staphylococcus aureus and Escherichia coli with the minimum inhibitory concentrations (MIC) of 40 and 160 μg mL− 1, respectively. The rapid and efficient uptake of CDs with E. coli and HFB cells was confirmed by the fluorescence imaging. Based on the results, the biogenic CDs can be a suitable alternative to the antibiotics against pathogenic bacteria and also for the staining and labeling of the microbial cells. © The Author(s), under exclusive licence to Shiraz University 2024.
Biosensors and Bioelectronics (18734235) 275
Emergence of recent pandemics/endemics e.g. COVID-19 and Dengue fever, demonstrated the necessity of development of strategies for swift adaptation of present biosensor for detection of the new emerging pathogens. However, development of a biosensor for a new target is time- and labor-consuming. In this study, we aimed to integrate the primer exchange reaction (PER), an isothermal technique that extends an initiator DNA with a user-defined single-stranded DNA tail, with bipolar electrochemistry. This integration led to the development of a universal biosensor, termed ViPER. We demonstrated the utility of the developed system to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomic RNA as a model. The genomic RNA was reverse transcribed to a short cDNA and was tailed with a universal tag, consequently, the tagged cDNA was applied to an electrochemiluminescence integrated bipolar electrochemical biosensor (BPE-ECL). ECL signals were recorded using a digital camera and analyzed by ImageJ. The platform demonstrated a linear response over a wide dynamic range of 10−7-10−17 M for the target nucleic acid with a detection limit of 2.31 × 10−17 M for synthetic targets. The biosensor could also successfully discriminate between biological RNA samples from infected and non-infected individuals. This study introduces the potential of DNA-based visual biosensors for detecting single-stranded RNAs in low-equipped environments, and it holds promises for further development of an ultrasensitive method for various human RNA-based viral pathogens. Moreover, we can design a platform with a predetermined DNA probe sequence for a vast variety of different targets, simply by changing the PER input. © 2025 Elsevier B.V.
Ayatollahi mehrgardi, M. ,
Mofidfar, M. ,
Li, J. ,
Chamberlayne, C.F. ,
Lynch, S.R. ,
Zare, R.N. Advanced Science (21983844) 11(38)
A straightforward nebulized spray system is designed to explore the hydrogenation of carbon dioxide (CO2) within water microdroplets surrounded by different gases such as carbon dioxide, nitrogen, oxygen, and compressed air. The collected droplets are analyzed using water-suppressed nuclear magnetic resonance (NMR). Formate anion (HCOO−), acetate anion (CH3COO−), ethylene glycol (HOCH2CH2OH), and methane (CH4) are detected when water is nebulized. This pattern persisted when the water is saturated with CO2, indicating that CO2 in the nebulizing gas triggers the formation of these small organics. In a pure CO2 atmosphere, the formate anion concentration is determined to be ≈70 µm, referenced to dimethyl sulfoxide, which has been introduced as an internal standard in the collected water droplets. This study highlights the power of water microdroplets to initiate unexpected chemistry for the transformation of CO2 to small organic compounds. © 2024 The Author(s). Advanced Science published by Wiley-VCH GmbH.
Proceedings of the National Academy of Sciences of the United States of America (10916490) 121(12)
Water microdroplets (7 to 11 µm average diameter, depending on flow rate) are sprayed in a closed chamber at ambient temperature, whose relative humidity (RH) is controlled. The resulting concentration of ROS (reactive oxygen species) formed in the microdroplets, measured by the amount of hydrogen peroxide (H2O2), is determined by nuclear magnetic resonance (NMR) and by spectrofluorimetric assays after the droplets are collected. The results are found to agree closely with one another. In addition, hydrated hydroxyl radical cations (•OH-H3O+) are recorded from the droplets using mass spectrometry and superoxide radical anions (•O2-) and hydroxyl radicals (•OH) by electron paramagnetic resonance spectroscopy. As the RH varies from 15 to 95%, the concentration of H2O2 shows a marked rise by a factor of about 3.5 in going from 15 to 50%, then levels off. By replacing the H2O of the sprayed water with deuterium oxide (D2O) but keeping the gas surrounding droplets with H2O, mass spectrometric analysis of the hydrated hydroxyl radical cations demonstrates that the water in the air plays a dominant role in producing H2O2 and other ROS, which accounts for the variation with RH. As RH increases, the droplet evaporation rate decreases. These two facts help us understand why viruses in droplets both survive better at low RH values, as found in indoor air in the wintertime, and are disinfected more effectively at higher RH values, as found in indoor air in the summertime, thus explaining the recognized seasonality of airborne viral infections. © 2024 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
Momtaz, F. ,
Momtaz, E. ,
Ayatollahi mehrgardi, M. ,
Momtaz, M. ,
Narimani, T. ,
Poursina, F. Scientific Reports (20452322) 14(1)
Packaging is very important to maintain the quality of food and prevent the growth of microbes. Therefore, the use of food packaging with antimicrobial properties protects the food from the growth of microorganisms. In this study, antibacterial nanocomposite films of polyvinyl alcohol/starch/chitosan (PVA/ST/CS) together with nickel oxide-copper oxide nanoparticles (NiO–CuONPs) are prepared for food packaging. NiO–CuONPs were synthesized by the co-precipitation method, and structural characterization of nanoparticles (NPs) was carried out by XRD, FTIR, and SEM techniques. Composites of PVA/ST/CS, containing different percentages of NPs, were prepared by casting and characterized by FTIR and FESEM. The mechanical properties, diffusion barrier, and thermal stability were determined. The nanoparticles have a round structure with an average size of 6.7 ± 1.2 nm. The cross-section of PVA/ST/CS film is dense, uniform, and without cracks. In the mechanical tests, the addition of NPs up to 1% improved the mechanical properties (TS = 31.94 MPa), while 2% of NPs lowered TS to 14.76 MPa. The fibroblast cells toxicity and the films antibacterial activity were also examined. The films displayed stronger antibacterial effects against Gram-positive bacteria (Staphylococcus aureus) compared to Gram-negative bacteria (Escherichia coli). Furthermore, these films have no toxicity to fibroblast cells and the survival rate of these cells in contact with the films is more than 84%. Therefore, this film is recommended for food packaging due to its excellent mechanical and barrier properties, good antibacterial activity, and non-toxicity. © The Author(s) 2024.
Scientific Reports (20452322) 14(1)
A simple, one-pot and green method is reported for hydrothermal synthesis of highly fluorescent and magnetic carbon dots (CDs) by using D-glucose, as the carbon source. CDs were fully characterized by the UV-Vis and fluorescence spectroscopy, DLS, FTIR, TEM, EDS, XRD, and VSM. The nitrogen doping of different diamines significantly improved the fluorescence quantum yield (QY) of CDs with the maximum effect obtained by using m-phenylenediamine (mPDA). Temperature and reaction time also affected the QY of CDs with the best results obtained at 150 °C for 3 h. The heteroatom doping by innovative use of different metal sulfates including FeSO4, MnSO4, CuSO4, MgSO4, and ZnSO4, further improved the optical properties of CDs. Interestingly, the magnetic and multicolor CDs with high colloidal stability and QYs of 17.7, 16.5, and 53.9% at 460, 490, and 515 nm, respectively, were synthesized by using 0.1 M of glucose, mPDA and MnSO4. The resulted Mn-, S-, N-doped CDs represented rapid uptake and high-quality fluorescence imaging of the human fibroblast and umbilical vein endothelial cells in vitro, without significant toxicity. The CDs also displayed high r1 relaxivity of 32.3 mM− 1 s− 1 and were used for high-contrast MR and fluorescence imaging of mouse tumor models, in vivo. © The Author(s) 2024.
ACS Applied Nano Materials (25740970) 7(7)pp. 6946-6957
The development of a theranostic platform that integrates multiple modalities into a single entity is a hopeful approach for effective cancer treatment but still a challenge. This study presents a smart and versatile theranostic nanoplatform for remarkably potent in vivo synergistic chemo-photothermal tumor treatment, guided by MR/fluorescence dual-mode imaging utilizing a pH-responsive strategy. We encapsulated Gd3+-based carbon quantum dots (GCDs) and doxorubicin (DOX) within hollow mesoporous Prussian blue nanoparticles (HMPB NPs). This innovative theranostic platform, named DOX/GCDs-HMPB NPs, facilitates targeted drug release and simultaneous MR/fluorescence imaging, specifically at the tumor site. At physiological pH, both GCDs and DOX molecules are encapsulated within the mesoporous hollow network of the nanoparticles, with the metal-ligand coordination bonding between Gd species and DOX molecules, to restrict water molecules’ access to the Gd3+ center, thus minimizing proton relaxivity. In the acidic tumor microenvironment, GCDs and DOX drug molecules are released simultaneously from the nanoparticles and enhance both MR contrast and fluorescence, leading to an increase in chemotherapeutic activities. This system reveals strong pH-switching theranostic performance for 4T1 cells, with high-efficiency chemotherapy and considerable photothermal conversion, indicating practical application for synergistic chemo-photothermal treatment of tumors. A promising strategy for developing a theranostic platform for cancer treatment and diagnosis is introduced. © 2024 American Chemical Society
Momtaz, M. ,
Momtaz, E. ,
Ayatollahi mehrgardi, M. ,
Momtaz, F. ,
Narimani, T. ,
Poursina, F. Scientific Reports (20452322) 14(1)
Food packaging with antibacterial properties has attracted much attention recently. In this study, nickel oxide nanoparticles (NiONPs) were synthesized by co-precipitation and then gelatin/chitosan polymer films (GEL/CS) with different percentages of NiONPs, bio-nanocomposites, were prepared by casting. Morphology, crystal microstructure, molecular interactions and thermal stabilities of the NPs and the composite films were characterized by FESEM, XRD, FTIR and TGA, respectively. The bio-nanocomposite films exhibited excellent barrier, thermal and mechanical properties by addition of an optimized content of NPs. For example, the tensile strength (TS) of the GEL/CS film without NPs was 23.83 MPa and increased to 30.13 MPa by incorporation of 1% NPs. The antibacterial properties and toxicity of the films were investigated. These films show good antibacterial behavior against Gram-positive (Staphylococcus aureus) bacteria compared to Gram-negative (Escherichia coli) bacteria. Furthermore, the films were found to be non-toxic to fibroblast cells that came into contact with the films, with a survival rate of more than 88%. Therefore, these films can be applied for food packaging due to their excellent mechanical, barrier, and antibacterial properties. © 2024, The Author(s).
Journal of the American Chemical Society (15205126) 146(46)pp. 31945-31949
Microbubbles, inside-out microdroplets, act as extraordinary microreactors to facilitate thermodynamically unfavorable reactions in bulk solutions of water. We explored the formation of hydrogen peroxide (H2O2) and its sustained regeneration at the interface of water-gas microbubbles. For this purpose, the chemiluminescence of luminol was recorded by a digital camera to map the intensity of blue light emission over the time of about 20 min. The formation and regeneration of hydrogen peroxide were also monitored by fluorescence microscopic imaging of a hydrogen peroxide probe. The microscopic images consistently show a stable glow around the microbubbles over time during which the formed hydrogen peroxide diffuses into the bulk solution. This observation confirms that the concentration of H2O2 at the interface is 30 times higher than that in the water solution bulk after several minutes, which can be attributed to its regeneration at the water-gas interface. These findings increase our understanding of why the chemistries of gas microbubbles in water and water microdroplets surrounded by gas are so distinct from those of bulk-phase water. © 2024 American Chemical Society.
Journal of the American Chemical Society (15205126) 146(27)pp. 18498-18503
Using real-time mass spectrometric (MS) monitoring, we demonstrate one-step, catalyst-free spontaneous oxidation of various alcohols (ROH) to key reactive intermediates for the formation of ROO- compounds on the surface of water microdroplets surrounded by alcohol vapor, carried out under ambient conditions. These organic peroxides (POs) can act as important secondary organic aerosols (SOA). We used hydrogen-deuterium exchange by spraying D2O instead of H2O to learn about the reaction mechanism, and the results demonstrate the crucial role of the water-air interface in microdroplet chemistry. We find that the formation of POs relies on electron transfer occurring at the microdroplet interface, which generates hydrogen atoms and hydroxyl radicals that lead to a cascade of radical reactions. This electron transfer is believed to be driven by two factors: (1) the emergence of a strong electrostatic potential on the microdroplet’s surface; and (2) the partial solvation of ions at the interface. Mass spectra reveal that the formation of POs is dependent on the alcohol structure, with tertiary alcohols showing a higher tendency to form organic peroxides than secondary alcohols, which in turn are more reactive than primary alcohols. © 2024 American Chemical Society.
Microchimica Acta (14365073) 190(4)
This review article comprehensively discusses the various electrochemical approaches for measuring and detecting oxidative stress biomarkers and enzymes, particularly reactive oxygen/nitrogen species, highly reactive chemical molecules, which are the byproducts of normal aerobic metabolism and can oxidize cellular components such as DNA, lipids, and proteins. First, we address the latest research on the electrochemical determination of reactive oxygen species generating enzymes, followed by detection of oxidative stress biomarkers, and final determination of total antioxidant activity (endogenous and exogenous). Most electrochemical sensing platforms exploited the unique properties of micro- and nanomaterials such as carbon nanomaterials, metal or metal oxide nanoparticles (NPs), conductive polymers and metal-nano compounds, which have been mainly used for enhancing the electrocatalytic response of sensors/biosensors. The performance of the electroanalytical devices commonly measured by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in terms of detection limit, sensitivity, and linear range of detection is also discussed. This article provides a comprehensive review of electrode fabrication, characterization and evaluation of their performances, which are assisting to design and manufacture an appropriate electrochemical (bio)sensor for medical and clinical applications. The key points such as accessibility, affordability, rapidity, low cost, and high sensitivity of the electrochemical sensing devices are also highlighted for the diagnosis of oxidative stress. Overall, this review brings a timely discussion on past and current approaches for developing electrochemical sensors and biosensors mainly based on micro and nanomaterials for the diagnosis of oxidative stress. Graphical abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Samani, R.K. ,
Maghsoudinia, F. ,
Asgari, M. ,
Atarod, M. ,
Ayatollahi mehrgardi, M. ,
Tavakoli, M.B. New Journal of Chemistry (11440546) 47(43)pp. 20193-20203
Recently, ultrasound-sensitive nanodroplets (NDs) have been developed as controlled-release drug delivery systems. However, the high pressure and frequency of ultrasound (US) waves were needed to induce acoustic droplet vaporization (ADV) for triggering drug release. In this study, folic acid (FA) targeted NDs with an alginate (Alg) shell containing methotrexate (MTX) as a chemotherapy drug and superparamagnetic iron oxide nanoparticles (SPIONs) as an ADV promotor and a magnetic resonance (MR) imaging contrast agent were successfully synthesized. The physicochemical properties of NDs including the size, morphology, ultrasound echogenicity, magnetic properties, MR relaxivity, and drug release patterns were evaluated. In vitro ultrasound imaging showed that NDs can generate highly echogenic microbubbles (MBs). Additionally, SPIONs/MTX ND with a relaxivity value of 87.59 mM−1 s−1 can act as a T2-weighted MRI contrast agent. Folate receptor-positive 4T1 cells and folate receptor-negative L929 cells were utilized. The cell experiments and blood cytotoxicity evaluations proved that SPIONs/MTX-FA NDs are highly biocompatible with no hemolytic activity. The cellular uptake of FA-functionalized NDs increased by 3.2-fold compared to that of non-functionalized NDs, and it was further enhanced, more than three times, after US exposure. The MTT assay demonstrated that the cell viability for ultrasound-exposed samples treated with SPIONs/MTX NDs was significantly decreased in comparison to blank NDs which is related to more drug release from NDs. It was concluded that SPIONs/MTX-FA NDs have significant potential as theranostic agents for dual-modal US/MRI-guided and acoustically-activated drug delivery. © 2023 The Royal Society of Chemistry.
Samani, R.K. ,
Maghsoudinia, F. ,
Mehradnia, F. ,
Hejazi, S.H. ,
Saeb, M. ,
Sobhani, T. ,
Farahbakhsh, Z. ,
Ayatollahi mehrgardi, M. ,
Tavakoli, M.B. Nanomedicine: Nanotechnology, Biology, and Medicine (15499634) 48
Chemoradiotherapy with controlled-release nanocarriers such as sono-sensitive nanodroplets (NDs) can enhance the anticancer activity of chemotherapy medicines and reduces normal tissue side effects. In this study, folic acid-functionalized methotrexate-loaded perfluorohexane NDs with alginate shell (FA-MTX/PFH@alginate NDs) were synthesized, characterized, and their potential for ultrasound-guided chemoradiotherapy of breast cancer was investigated in vitro and in vivo. The cancer cell (4T1) viabilities and surviving fractions after NDs and ultrasound treatments were significantly decreased. However, this reduction was much more significant for ultrasound in combination with X-ray irradiation. The in vitro and in vivo results confirmed that MTX-loaded NDs are highly biocompatible and they have no significant hemolytic activity and organ toxicity. Furthermore, the in vivo results indicated that the FA-MTX/PFH@alginate NDs were accumulated selectively in the tumor region. In conclusion, FA-functionalized MTX/PFH@alginate NDs have a great theranostic performance for ultrasound-controlled drug delivery in combination with radiotherapy of breast cancer. © 2023
Abbasi kajani, A. ,
Rafiee l., L. ,
Samandari, M. ,
Ayatollahi mehrgardi, M. ,
Zarrin, B. ,
Javanmard, S.H. RSC Advances (20462069) 12(51)pp. 32834-32843
Facile and sensitive detection and isolation of circulating tumor cells (CTCs) was achieved using the aptamer-targeted magnetic nanoparticles (Apt-MNPs) in conjugation with a microfluidic device. Apt-MNPs were developed by the covalent attachment of anti-MUC1 aptamer to the silica-coated magnetic nanoparticles via the glutaraldehyde linkers. Apt-MNPs displayed high stability and functionality after 6 months of storage at 4 °C. The specific microfluidic device consisting of mixing, sorting and separation modules was fabricated through conventional photo- and soft-lithography by using polydimethylsiloxane. The capture efficiency of Apt-MNPs was first studied in vitro on MCF-7 and MDA-MB-231 cancer cell lines in the bulk and microfluidic platforms. The cell capture yields of more than 91% were obtained at the optimum condition after 60 minutes of exposure to 50 μg mL−1 Apt-MNPs with 10 to 106 cancer cells in different media. CTCs were also isolated efficiently from the blood samples of breast cancer patients and successfully propagated in vitro. The isolated CTCs were further characterized using immunofluorescence staining. The overall results indicated the high potential of the present method for the detection and capture of CTCs. © 2022 The Royal Society of Chemistry.
Journal of the American Chemical Society (15205126) 144(17)pp. 7606-7609
Ultrapure N2gas was bubbled through water, and the humidified output containing undetectable concentrations of ozone filled a closed chamber in which 18 Mω-cm water was sprayed through a silica capillary to form microdroplets. Analysis of the collected microdroplets by NMR spectroscopy showed the presence of hydrogen peroxide at a concentration level ranging from 0.3 to 1.5 μM depending on the flow conditions. This was confirmed using a spectrofluorometric assay. We suggest that this finding establishes that when sprayed to form microdroplets, water has the ability to produce hydrogen peroxide by itself. When the N2gas is replaced by compressed air or O2gas, the concentration of hydrogen peroxide is found to increase, indicating that gas-surface interactions with O2in aqueous microdroplets promote the formation of hydrogen peroxide. © 2022 American Chemical Society. All rights reserved.
Bioelectrochemistry (15675394) 140
Regarding the cancer fatal consequences, early detection and progression monitoring are the most vital issues in patients’ treatment and mortality reduction. Therefore, there is a great demand for fast, inexpensive, and selective detection methods. Herein, a graphene-based aptasensor was designed for sensitive human breast cancer cell detection. A reduced graphene oxide-chitosan-gold nanoparticles composite was used as a biocompatible substrate for the receptor stabilization. The significant function of the aptamer on this composite is due to the synergistic effects of the components in improving the properties of the composite, including increasing the electrical conductivity and effective surface area. After the aptasensor incubation in MCF-7 cancer cells, the cell membrane proteins interacted specifically with the three dimensional-structure of the AS1411 aptamer, resulting in the cell capture on the aptasensor. The aptasensor fabrication steps were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The higher cell concentrations concluded to the higher captured cells on the aptasensor which blocked the Ferro/Ferricyanide access to the sensor, causing increases in the charge transfer resistances. This aptasensor shows a linear relationship with the cell concentration logarithm, high selectivity, a wide linear range of 1 × 101–1 × 106 cells/mL, and a low detection limit of 4 cells/mL. © 2021 Elsevier B.V.
Asgari, M. ,
Khanahmad, H. ,
Motaghi, H. ,
Farzadniya, A. ,
Ayatollahi mehrgardi, M. ,
Shokrani, P. Applied Physics A: Materials Science and Processing (14320630) 127(1)
A multifunctional-aptamer (APT) nanoprobe, TOV6 APT-superparamagnetic iron oxide nanoparticle-carbon dots (APT-SPION-CDs), for fluorescence and magnetic resonance targeted imaging (FI/MRI) of human ovarian cancer cells (OVCAR-3) is introduced. The SPION-CDs were synthesized and conjugated with TOV6 APT recognizing the stress-induced phosphoprotein 1 (STIP1) overexpressed on OVCAR-3 cells. The capability of the nanoprobe as a contrast agent for MRI and simultaneously as a fluorescent probe for fluorescence microscopy was studied. TOV6 APTs were adsorbed on SPION-CDs and were confirmed with Fourier transform infrared spectrometer. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed higher cytotoxic effects for APT-SPION-CDs compared to SPION-CDs on STIP1-negative HeLa cells. But on OVCAR-3, as STIP1-positive cells, the cytotoxic effect was negligible. The fluorescence microscopic images confirmed that APT-SPION-CDs specifically targeted ovarian cancer cells due to the tumor-targeting effect of TOV6 APT. High spin–spin relaxivity value (r2 = 308.5 mM−1 s−1) and the signal enhancement in T2-weighted MRIs confirmed the capability of the nanoprobe as a T2-based contrast agent. In vitro cellular uptake and signal enhancement of this multimodal FI/MRI nanoprobe demonstrated the potential application of APT-SPION-CDs as a contrast agent for MRI and as a fluorescent probe for fluorescence microscopic imaging. © 2021, Springer-Verlag GmbH Germany, part of Springer Nature.
Maghsoudinia, F. ,
Tavakoli, M.B. ,
Samani, R.K. ,
Motaghi, H. ,
Hejazi, S.H. ,
Ayatollahi mehrgardi, M. Journal of Drug Delivery Science and Technology (17732247) 61
In this study, single- and dual-targeted gadolinium-carbon dots (Gd-CDs) with Bevacizumab (BEV) and/or folic acid (FA) were developed as dual-modal fluorescence and magnetic resonance (FL/MR) imaging nanoprobes. Gd-CDs were prepared by a single-pot hydrothermal route using citric acid, ethylenediamine, and Gd-DO3A-butrol (Gadovist) as the starting materials. Mouse hepatocellular carcinoma (Hepa1-6) cell line was selected as cancer cells, while mouse fibroblast (L929) was used as a normal cell line. Gd-CDs, Gd-CDs-FA, Gd-CDs-BEV, and Gd-CDs-FA-BEV exhibited the high relaxivities (r1) of 7.98, 7.83, 7.61, and 6.03 mM−1 s−1, respectively, being considerably more than the clinical Gd-DO3A-butrol contrast agent (r1 = 4.01 mM−1 s−1). Moreover, they exhibited strong fluorescence with a fluorescence quantum yield (QY) of 49.94%, 61.22%, 82.5%, and 83.67%, respectively. MTT assays on cancer and normal cells showed that various synthesized Gd-CDs on both cell lines have low toxicity. Inductively coupled plasma optical emission spectrometry (ICP-OES) analysis revealed that Gd-CDs-FA-BEV uptake by Hepa1-6 cells was 5-fold as much as the non-targeted Gd-CDs after 24 h incubation. Functionalization of Gd-CDs with Bevacizumab and/or folic acid improves the diagnostic sensitivities and specificities, making them ideal contrast agents for MRI as well as ideal fluorophores for fluorescence imaging. © 2020 Elsevier B.V.
Nanomedicine (17486963) 16(8)pp. 627-640
Aim: To develop a novel theranostic nanoplatform for simultaneous fluorescent monitoring and stimuli-triggered drug delivery. Materials & methods: Different microscopic and spectroscopic techniques were used for the characterization of nanocarriers. MCF-7 and human umbilical vein endothelial cell lines were cultured and treated with different doses of doxorubicin-loaded nanocarriers. The cell viability and drug release were studied using MTT assay and fluorescence microscopy. Results: Biocompatible and mono-disperse nanocarriers represent hollow and mesoporous structures with the calculated surface area of 552.83 m2.g-1, high magnetic activity (12.6 emu.g-1), appropriate colloidal stability and high drug loading capacity (up to 61%). Conclusion: Taxane-based carbon dots act as the pH-responsive gatekeepers for the controlled release of doxorubicin into cancer cells and provide a fluorescence resonance energy transfer system for real-time monitoring of drug delivery. © 2021 Future Medicine Ltd.
Maghsoudinia, F. ,
Tavakoli, M.B. ,
Samani, R.K. ,
Hejazi, S.H. ,
Sobhani, T. ,
Mehradnia, F. ,
Ayatollahi mehrgardi, M. Talanta (00399140) 228
Dual-modal molecular imaging by combining two imaging techniques can provide complementary information for early cancer diagnosis and therapeutic monitoring. In the present manuscript, folic acid (FA)-functionalized gadolinium-loaded nanodroplets (NDs) are introduced as dual-modal ultrasound (US)/magnetic resonance (MR) imaging contrast agents. These phase-change contrast agents (PCCAs) with alginate (Alg) stabilizing shell and a liquid perfluorohexane (PFH) core were successfully synthesized via the nano-emulsion method and characterized. In this regard, mouse hepatocellular carcinoma (Hepa1-6) as target cancer cells and mouse fibroblast (L929) as control cells were used. The in vitro and in vivo cytotoxicity assessments indicated that Gd/PFH@Alg and Gd/PFH@Alg-FA nanodroplets are highly biocompatible. Gd-loaded NDs do not induce organ toxicity, and no significant hemolytic activity in human red blood cells is observed. Additionally, nanodroplets exhibited strong ultrasound signal intensities as well as T1-weighted MRI signal enhancement with a high relaxivity value of 6.40 mM−1 s−1, which is significantly higher than that of the clinical Gadovist contrast agent (r1 = 4.01 mM−1 s−1). Cellular uptake of Gd-NDs-FA by Hepa1-6 cancer cells was approximately 2.5-fold higher than that of Gd-NDs after 12 h incubation. Furthermore, in vivo results confirmed that the Gd-NDs-FA bound selectively to cancer cells and were accumulated in the tumor region. In conclusion, Gd/PFH@Alg-FA nanodroplets have great potential as US/MR dual-modal imaging nanoprobes for the early diagnosis of cancer. © 2021 Elsevier B.V.
ChemElectroChem (21960216) 7(16)pp. 3439-3444
In this study, a non-modified closed bipolar electrochemical system for ultrasensitive cancer cell detection by quantitative measurement of released hydrogen peroxide in the presence of ascorbic acid has been developed. This system includes two separate chambers (reporting and sensing), a piece of a gold archival CD (compact disc) as a bipolar electrode, and two platinum driving electrodes. By following the ECL (electrochemiluminescence) intensities of luminol oxidation in the reporting chamber, the hydrogen peroxide released by cancer cells in the presence of ascorbic acid was monitored. Under the optimum conditions, the biosensor delivers a wide linear range from 2.5×10−9 to 1×10−6 M, and a detection limit for hydrogen peroxide as low as 1.8×10−9 M. Also, this system can detect cancer blood cell concentrations (CCRF-CEM: T-lymphoblastic leukemia cell line) as low as 12 cells in 300 μL of cell suspension. The present bipolar electrode-electrochemiluminescence (BPE-ECL) system demonstrates a simple and low-cost device with excellent performance without any electrode surface modification for the detection of cancer cells based on different levels of released hydrogen peroxide by normal and cancer cells. The present biosensor can be applied as a promising alternative method for the detection of H2O2 in the field of pathology, cancer diagnosis, and environmental monitoring. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Samani, R.K. ,
Tavakoli, M.B. ,
Maghsoudinia, F. ,
Motaghi, H. ,
Hejazi, S.H. ,
Ayatollahi mehrgardi, M. European Journal of Pharmaceutical Sciences (18790720) 153
In the present study, the effect of functionalized gold nanoclusters (AuNCs) with trastuzumab (Herceptin®) and/or folic acid (FA) as a single and dual-targeted radiosensitizers for the enhancement of megavoltage radiation therapy efficacy was investigated. SK-BR3 breast cancer cells as human epidermal growth factor 2 (HER2) and folate overexpressing cell line and the murine fibroblast (L929) as a control cell line were selected. The cellular uptake was followed using inductively coupled plasma optical emission spectrometry (ICP-OES) that showed AuNCs-FA-HER uptake by SK-BR3 cells was 3 times more than the non-targeted AuNCs after 12 h incubation. MTT and clonogenic assays revealed that the viability and surviving fraction of cancer cells were significantly inhibited by treating with all AuNCs under radiation compared to treating with radiation alone. However, these effects in the dual-targeted AuNCs group (AuNCs-FA-HER) was significantly greater than non-targeted and single-targeted AuNCs groups. Also, apoptosis was evaluated using an Annexin V-FITC/propidium iodide (PI) kit in flow cytometry. All AuNCs, in combination with 4 Gy of photon beam, induced more apoptosis. By fitting the survival fraction data on the linear-quadratic model, the sensitization enhancement factor (SER) of AuNCs, AuNCs-FA, AuNCs-HER, and AuNCs-FA-HER, were obtained 1.17, 1.32, 1.48 and 1.77, respectively. SER for AuNCs-FA-HER was significantly higher than that non-targeted and single-targeted AuNCs (p-value < 0.05) that can be attributed to more internalization in the cancer cells. It was concluded that functionalized AuNCs with both folic acid and Herceptin could represent a promising strategy for increased cellular internalization that improved radiation therapy efficiency in SK-BR3 breast cancer cells. © 2020 Elsevier B.V.
Journal of Drug Targeting (10292330) 27(3)pp. 315-324
In the present study, alive attenuated Salmonella typhi Ty21a was introduced as a vehicle for smart delivery of gold nanoparticles to the tumours’ hypoxic regions. At the first step, the uptakes of gold nanoparticles with seven different decorations by S. typhi Ty21a was investigated using flow cytometry and inductively coupled plasma optical emission spectroscopy. The analyses demonstrated that folic acid functionalised gold nanoparticles (FA-GNPs) are the best candidates for producing the Golden Bacteria (GB). Subsequently, the GB and FA-GNPs efficacies for tumour targeting were investigated after intravenous injection to CT-26 tumour-bearing mice. The GB exhibited more GNPs delivery to the tumour in comparison with FA-GNPs. Moreover, GB injection causes more delivery of GNPs to the tumours’ central regions in comparison with tumours’ periphery. This trend is completely in reverse for FA-GNPs injected group. The ratios of peripheral to central regions’ gold concentration of the tumours were 1.95 ± 0.13 and 0.61 ± 0.10 for FA-GNPs and GB groups, respectively. This observation demonstrates higher accumulation of gold nanoparticles in the centre of the tumour due to their active delivery by the S. typhi Ty21a to the deeps of tumours. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.
Ayatollahi mehrgardi, M. ,
Shadman, S.M. ,
Daneshi, M. ,
Shafiei, F. ,
Azimimehr M. ,
Khorasgani M.R. ,
Sadeghian M. ,
Motaghi, H. ,
Shadman, S.M. ,
Daneshi, M. ,
Shafiei, F. ,
Azimimehr M. ,
Khorasgani M.R. ,
Sadeghian M. ,
Motaghi, H. ,
Ayatollahi mehrgardi, M. 2025 29th International Computer Conference, Computer Society of Iran, CSICC 2025 pp. 213-251
Electrochemical biosensors play an important role in the quantification of various targets that are of utmost importance for the environmental, medical, biological, and industrial applications. For the designing and fabrication of electrochemical biosensors, the surface of electrodes should be modified with biomolecules as recognition layers that can specifically interact with these analytes. Aptamers are short synthetic oligonucleotides or peptide molecules that can bind specifically to a broad range of targets, including heavy metal ions, antibiotics, neurotransmitters, nucleotides, pesticides, drugs, proteins, biomarkers, and finally whole cells. The capability of aptamers for specifically binding to various targets makes them as highly promising candidates for the recognition layers of electrochemical biosensors. In this chapter, the recent advances in the field of “aptamer-based electrochemical biosensors” have been reviewed. © 2019 Elsevier Inc. All rights reserved.
Kabirian-dehkordi, S. ,
Chalabi-dchar, M. ,
Mertani, H.C. ,
Le guellec, D. ,
Verrier, B. ,
Diaz, J. ,
Ayatollahi mehrgardi, M. ,
Bouvet, P. Nanomedicine: Nanotechnology, Biology, and Medicine (15499634) 21
G-rich oligonucleotide, AS1411, has been shown to interact with nucleolin and to inhibit cancer cell proliferation and tumor growth. This antiproliferative action is increased when AS1411 is conjugated to different types of nanoparticles. However, the molecular mechanisms are not known. In this work, we show in several cell lines that optimized AS1411-conjugated gold nanoparticles (GNS-AS1411) inhibit nucleolin expression at the RNA and protein levels. We observed an alteration of the nucleolar structure with a decrease of ribosomal RNA accumulation comparable to what is observed upon nucleolin knock down. However, the expression of genes involved in cell cycle and the cell cycle blockage by GNS-AS1411 are not regulated in the same way as that in cells where nucleolin has been knocked down. These data suggest that the anti-proliferative activity of GNS-AS1411 is not the only consequence of nucleolin targeting and down-regulation. © 2019 Elsevier Inc.
Analytical Chemistry (15206882) 91(9)pp. 6383-6390
A sensitive prostate-specific antigen (PSA) detection method using a visual-readout closed bipolar electrode (BPE) system has been introduced by integration of hydrogen evolution reaction (HER) in cathodic pole and electrochemiluminescence (ECL) of luminol loaded within the MIL-53(Fe)-NH 2 (L@MIL-53(Fe)-NH 2 ) in the anodic pole. The cathode of the BPE was electrochemically synthesized by 3D porous copper foam, followed by decorating with nitrogen-doped graphene nanosheet and ruthenium nanoparticles. As an alternative, we employed carboxylate-modified magnetic nanoparticles (MNPs) for immobilization of the primary antibody (Ab1) and utilized the L@MIL-53(Fe)-NH 2 conjugated to secondary antibody (Ab2) as a signaling probe and coreaction accelerator. After sandwiching the target PSA between Ab1 and Ab2, the MNP/Ab1-PSA-Ab2/L@MIL-53(Fe) were introduced to a gold anodic BPE. Finally, the resulting ECL of luminol and H 2 O 2 at the anodic poles was monitored using a photomultiplier tube (PMT) or digital camera. The PMT and visual (camera)-based detections showed linear responses from 1 pg mL -1 to 300 ng mL -1 (limit of detection 0.2 pg mL -1 ) and 5 pg mL -1 to 200 ng mL -1 (limit of detection 0.1 pg mL -1 ), respectively. This strategy provides an effective method for high-performance bioanalysis and opens a new door toward the development of the highly sensitive and user-friendly device. © 2019 American Chemical Society.
European Journal of Pharmaceutical Sciences (18790720) 130pp. 225-233
Gold nanoparticles (GNPs) radiosensitizing effect strongly depends on the tumor targeting efficacy. The aim of this study is to identify the most ideal targeting decoration for BSA-GNPs according to tumor targeting and biodistribution. Therefore, three well-known targeting agents (folic acid, glucose, and glutamine) were utilized for BSA-GNPs decoration. Glucose-BSA-GNPs, glutamine-BSA-GNPs, and folic acid-BSA-GNPs were synthesized and then, characterized by Fourier-transform infrared spectroscopy and UV-Spectrometry. Then, the GNPs were intravenously injected 10 mg/kg to 4T1 breast tumor-bearing mice to evaluate biodistribution and radiosensitizing effects. Folic acid and glutamine decorations could significantly increase tumor targeting efficacy of BSA-GNPs as 2.1 and 2.4 times increase of gold accumulation was detected in comparison with BSA-GNPs. They exhibited the highest radiosensitizing efficacy and caused about 33% decrease in tumors volume in comparison with BSA-GNPs after 6 Gy radiation therapy. All the GNPs were completely biocompatible. Although, glutamine-BSA-GNPs and folic acid-BSA-GNPs could significantly enhance the tumor targeting and radiosensitizing efficacy of BSA-GNPs, did not exhibit any significant advantage over each other. Therefore, glutamine and folic acid decoration of BSA-GNPs can significantly increase the tumor targeting and therapeutic efficacy as radiosensitizer. © 2019
Emergent Materials (2522574X) 2(3)pp. 351-361
Major technological challenges in point-of-care diagnostics are in the development of simple, fast, and inexpensive methods for high-throughput and multiplexed genotyping of single-nucleotide polymorphisms (SNPs). Herein, we develop a facile SNP detection platform based on platinum nanoparticles–induced etching of gold nanorods (AuNRs) by H2O2. The IVS-II-1 (G>A) β-thalassemia mutation, as one of the most prevalent mutations in the Middle East, was used as a model disease. In the presence of H2O2, ferrous ion (Fe2+) triggers a Fenton reaction with the catalytic decomposition of H2O2 into highly reactive hydroxyl (HO·) and hydroperoxyl (HOO·) radicals. These species etch AuNRs along the longitudinal axes to short AuNRs or even Au nanoparticles. For signaling SNPs, monobase-modified platinum nanoparticles (M-PtNPs) are hybridized to mutated sites of the duplex DNA. PtNPs catalyze the decomposition of H2O2 to water and oxygen, thus reducing the amount of H2O2 available for oxidative etching of AuNRs, and generating a series of distinct colors depending on the frequency of SNP in the target DNA. The frequency of SNP can be detected with the naked-eye or with UV-vis spectroscopy. The naked-eye detection limits of G–T and A–C mismatches are 17 and 15 pM, whereas UV-vis method responds linearly to these mismatches in the ranges from 10 to 200 pM and 5 to 120 pM with detection limits of 4 and 2 pM (3σ/slope), respectively. The present genosensor demonstrates a straightforward and easy-to-interpret method for naked-eye discrimination between PCR products of normal, heterozygous, and homozygous β-thalassemia-related mutation of β-hemoglobin. [Figure not available: see fulltext.] © 2019, Qatar University and Springer Nature Switzerland AG.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy (13861425) 206pp. 154-159
In the present manuscript, a new spectrofluorometric method for the genotyping of various single nucleotide polymorphisms (SNPs) using carbon dots (CDs) is investigated. For the construction of the assay, thiolated probe DNA is self-assembled on a gold surface via sulfur‑gold chemistry and afterward, the probe is partially hybridized with a longer target DNA strand. Subsequently, the unhybridized section of the target DNA is hybridized with a capture DNA to form the DNA double-helix self-assembled monolayer on the gold surface. Finally, CDs surface amine groups are covalently attached to the 5′ phosphate groups of various monobases (MB-CDs) using phosphoramidite chemistry. In this method, genotyping of SNPs is based on following the changes in fluorescence intensity of the MB-CDs suspensions before and after incubation with DNA modified gold surface. The assay is straightforward with no need for target labeling and is sensitive and low cost enough to genotype various SNPs independent of their position in a DNA double helix with an acceptable limit of detections in picomolar ranges. © 2018 Elsevier B.V.
Electrochemistry Communications (13882481) 88pp. 24-28
We report a sensor platform based on a closed bipolar electrochemical circuit employing electrochemiluminescence detection and square-wave excitation that allows signal averaging to achieve high sensitivity. The cell is comprised of a bipolar electrode fabricated using photolithography that spans sensing and reporting compartments constructed using a 3D printer. The square-wave technique allows an electroactive analyte to be regenerated by applying a reverse potential, thus allowing significant S/N gains by accumulating ECL signals over multiple measure-regenerate cycles. The working principles of the SW-BPE sensor were demonstrated using Fe(CN)63− as a representative analyte. Using DNA self-assembled monolayers as a model for the electrochemical proximity assay co-developed in our laboratories, we demonstrate the ability to detect ca. 300 fmol/cm2 of MB-conjugated DNA. The square wave ECL sensor described herein is capable of detecting a wide variety of analytes over broad concentration ranges, and shows great promise for a variety of analytical applications. © 2018 Elsevier B.V.
Journal of Chromatography A (00219673) 1564pp. 85-93
Aptamers, due to the inherently high selectivity towards target analytes, are promising candidate for surface modification of the nanoparticles. Therefore, aptamer-functionalized magnetic nanoparticles (AMNPs) was prepared and used to develop a magnetic solid-phase extraction procedure for clean-up of milk and dairy products samples before measuring the aflatoxin M1 (AFM1) contents by the high-performance liquid chromatography. The prepared sorbent was characterized by different instrumental methods such as FT-IR, FESEM, TEM, EDX and AGFM. The AMNPs was used in extraction and pre-concentration of ultratrace amounts AFM1 from local milk samples. The amount of sorbent, elution volume, extraction time, and salt addition were optimized. Based on the results, calibration plot is linear over the 0.3 to 1 ng·L−1 and 5 to 50 ng·L−1 AFM1 concentration ranges. The limits of detection of the developed method were obtained 0.2 ng·L−1 which is the smallest value that has been reported up to now. The results show that this new superior sorbent has a large potential to simplify the complex matrix of the samples and can used for detection, preconcentration and accurate determination of ultratrace amounts of the AFM1 from milk and dairy products. © 2018 Elsevier B.V.
Ghahremani, F. ,
Shahbazi-gahrouei, D. ,
Kefayat, A. ,
Motaghi, H. ,
Ayatollahi mehrgardi, M. ,
Javanmard, S.H. RSC Advances (20462069) 8(8)pp. 4249-4258
In the present study, AS1411 aptamer conjugated gold nanoclusters (GNCs) have been introduced as a targeted radiosensitizer for enhancing megavoltage radiation therapy efficacy. GNCs with an ultra-small gold core and a bovine serum albumin shell (BSA) as a versatile nano-platform were synthesized and conjugated to AS1411 aptamer (Apt-GNCs). Due to nucleolin overexpression in breast cancer cells and high affinity of the AS1411 aptamer to nucleolin, mouse mammary carcinoma cell line (4T1) was selected as the malignant cells and murine fibroblast (L929) was used as a normal cell line. Flow cytometry assessments reveal a significant increase in GNCs uptake by the cancer cells in the presence of the aptamer as the targeting agent. Inductively coupled plasma optical emission spectrometry (ICP-OES) measurements demonstrate 4 times more Apt-GNCs uptake by 4T1 cells than the normal cells at a concentration ratio of 1:40 (4 μM aptamer and 160 μM GNCs at 24 h incubation). Moreover, the combination of megavoltage radiation therapy and Apt-GNCs as radiosensitizer causes effective cancer cell death and a dose enhancement factor (DEF) of about 2.7 in clonogenic survival assay is obtained. © 2018 The Royal Society of Chemistry.
Ghahremani, F. ,
Kefayat, A. ,
Shahbazi-gahrouei, D. ,
Motaghi, H. ,
Ayatollahi mehrgardi, M. ,
Javanmard, S.H. Nanomedicine (17486963) 13(20)pp. 2563-2578
Aim: Herein, the AS1411 aptamer-targeted ultrasmall gold nanoclusters (GNCs) were assessed at different aspects as a radiosensitizer. Materials & methods: AS1411 aptamer-conjugated gold nanoclusters (Apt-GNCs) efficacy was evaluated at cancer cells targeting, radiosensitizing effect, tumor targeting, and biocompatibility in breast tumor-bearing mice. Results: Flow cytometry and fluorescence microscopy exhibited more cellular uptake for Apt-GNCs in comparison with GNCs. In addition, inductively coupled plasma optical emission spectrometry results demonstrated its effective tumor targeting as the tumors' gold content for GNCs and Apt-GNCs were 8.53 and 15.33 μg/g, respectively. Apt-GNCs significantly enhanced radiotherapy efficacy as mean tumors' volume decreased about 39% and 9 days increase in the mice survival was observed. Both GNCs and Apt-GNCs were biocompatible. Conclusion: The Apt-GNCs is a novel and efficient radiosensitizer. © 2018 2018 Future Medicine Ltd.
Biosensors and Bioelectronics (18734235) 118pp. 217-223
In the present manuscript, a closed bipolar electrode system integrated with electrochemiluminescence (ECL) detection has been introduced for sensitive diagnosis of human breast cancer cells (MCF-7). For sensitive and selective detection, the anodic pole of the bipolar electrode was modified with the AS1411 aptamer, a specific aptamer for the nucleolin, and treated by the secondary aptamer modified gold nanoparticles. The electrochemiluminescence of luminol was followed in the presence of hydrogen peroxide on the anode pole of bipolar electrode (BPE) as an analytical signal. Moreover, 3D printed microchannels were used for the fabrication of BPE systems to minimize the required amounts of sample. The present aptasensor offers low cost, sensitive and selective cancer cell detection with two acceptable linear ranges. The first linear section appears within 10–100 cells and the latter is found to be within 100–700 cells. The limit of detection was about 10 cells. © 2018 Elsevier B.V.
Abbasi kajani, A. ,
Bordbar, A. ,
Ayatollahi mehrgardi, M. ,
Zarkesh-esfahani, H. ,
Motaghi, H. ,
Kardi, M.T. ,
Khosropour, A.R. ,
Ozdemir, J. ,
Benamara, M. ,
Beyzavi, M.H. ACS Applied Bio Materials (25766422) 1(5)pp. 1458-1467
Carbon dots (CDs), as a new generation of fluorescent nanoparticles, have been greatly considered for different biomedical applications. In the present study, a one-pot hydrothermal method was developed for the synthesis of a series of carbon dots (CDs) for cancer imaging and therapy. Taxane diterpenoids were utilized as the carbon source, different diamines were used as the nitrogen source, and folic acid was used as a targeting agent. High-quality photostable and multicolor (blue and green) carbon nanocrystals with a hexagonal shape, a narrow size distribution of less than 20 nm, and high fluorescence quantum yield of up to 50.4% were obtained from taxanes in combination with m-phenylenediamine and folic acid to give the best results. The nanoparticles displayed a potent anticancer activity with IC50 values of 31.3 ± 2.7 and 34.1 ± 1.1 μg mL-1 for the human MCF-7 and HeLa cancer cell lines, respectively, and IC50 value of 120.5 ± 3.8 μg mL-1 on the normal human fibroblast cells. The flow cytometry studies determined apoptosis-mediated cell death as the main anticancer mechanism of CDs, and the molecular studies revealed the induction of both extrinsic and intrinsic apoptosis pathways. The overall results indicated the great potential of synthesized CDs for the simultaneous cancer imaging and therapy. Copyright © 2018 American Chemical Society.
Journal Of Biomedical Physics And Engineering (22517200) 8(3)pp. 357-364
Introduction: One class of magnetic nanoparticles is magnetic iron oxide nanoparticles (MIONs) which has been widely offered due to of their many advantages. Owing to the extensive application of MIONs in biomedicine, before they can be used in vivo, their cytotoxicity have to be investigated. Therefore, there is an urgent need for understanding the potential risks associated with MIONs. Materials and Methods: Firstly, gold-coated Fe3O4 nanoparticles (GMNP) were synthesized. The size, structure and spectroscopic properties of the nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometry (XRD) and UV-Visible spectrophotometer, respectively. Cytotoxicity of nanoparticles was studied with different concentrations ranging from 10 µg/mL up to 400 µg/mL and for different incubation times (12 hours and 24 hours) on MCF-7 and HFFF-PI6. Cytotoxicity study was performed by MTT assay. Results: XRD pattern confirmed the structure of GMNPs and TEM image shows that GMNPs are under 50 nm. For MCF-7 and HFFF-PI6 cells, at concentration of 300 and 400 µg/mL, Fe3O4 nanoparticles are toxic, respectively. Moreover, for both cells, cell viability for GMNPs is higher than %80, therefore, up to 400 µg/mL they are not toxic. Results show that for both cells, Fe3O4 nanoparticles have higher cytotoxicity than GMNPs. Conclusion: This finding suggests that gold coating reduces the toxic effects of uncoated Fe3O4 nanoparticles. Less toxicity of GMNP may be attributed to controlled release from Fe2+ ions in intracellular space. Moreover, cell toxicity increased with raise in dose (concentration) and incubation time. © 2018, Shiraz University of Medical Sciences. All rights reserved.
Biosensors and Bioelectronics (18734235) 100pp. 382-388
A sensitive electrochemiluminescence (ECL) aptasensor for aflatoxin M1 (AFM1) detection by a closed bipolar electrode (BPE) array has been introduced. The thiolated AFM1 aptamer was immobilized on gold nanoparticle-coated magnetic Fe3O4 nanoparticles (Apt-GMNPs). Luminol-functionalized silver nanoparticle-decorated graphene oxide (GO-L-AgNPs) participates in π-π interactions with the unpaired bases of the immobilized aptamer (Apt-GMNPs-GO-L-AgNPs). After the Apt-GMNPs-GO-L-AgNPs were introduced to a gold anodic BPE array, the individual electrodes were subjected to different concentrations of AFM1. Upon the interaction of AFM1 with the aptamers, the GO-L-AgNPs detach from the aptamer; the resulting ECL of luminol and H2O2 at the anodic poles is monitored using a photomultiplier tube (PMT) or smartphone, and the images are analyzed using ImageJ software. This process triggers thionine reduction at the cathodic poles. Under the optimal conditions obtained by a face-centered central composite design (FCCD), the PMT-based detection of the BPE-ECL aptasensor exhibit a linear response over a wide dynamic range from 5 to 150 ng mL−1, with a detection limit of 0.01 ng mL−1. Additionally, smartphone-based detection shows a linear relationship between the ECL image gray value and the logarithmic concentration of the AFM1 target over a range of 10–200 ng mL−1, with a detection limit of 0.05 ng mL−1. Furthermore, the BPE-ECL aptasensor was successfully used to detect AFM1 in milk complex media without any serious interferences with reliable reproducibility (average relative standard deviation (RSD = 2.3%)). This smartphone-based detection opens a new horizon for bioanalysis that does not require a trained technician to operate and is a promising technology for point-of-care testing. © 2017 Elsevier B.V.
Journal Of The Iranian Chemical Society (1735207X) 14(9)pp. 2007-2016
In this work, a sensitive electrochemical aptasensor for the detection of adenosine triphosphate (ATP) has been introduced. A simple and non-enzymatic signal amplification strategy is utilized using silver nanoparticle-decorated graphene oxide (AgNPs–GO) as a redox probe. The modified electrode surface was characterized by scanning electron microscopy, FTIR and UV–Vis spectroscopy, and electrochemical impedance spectroscopy. GO provides an excellent substrate for the presence of the large number of AgNPs, so the monitored oxidation signal of AgNPs has been amplified. ATP-specific DNA aptamer is split into two fragments (F1 & F2) in order to design a sandwich-type assay. For the construction of the sensor, the surface of a graphite screen-printed electrode is modified with electrodeposited gold nanoparticles followed by self-assembling a monolayer of 3-mercaptopropionic acid on the electrode surface. The first amino-labeled fragment, F1, is immobilized on the modified electrode via carbodiimide chemistry. The synthesized AgNPs–GO interacts with F1 via π- π stacking. In the presence of ATP, the second fragment of the aptamer, F2, forms an associated complex with the immobilized F1 and causes AgNPs–GO to leave the surface. Consequently, a remarkable decrease in the oxidation signal of the AgNPs is observed. The percentage of this decrease has been monitored as an analytical signal, which is proportional to ATP concentration, and delivers a linear response over the range of 10.0 (±0.6) to 850 (±5) nM with a detection limit of 5.0 (±0.2) nM. © 2017, Iranian Chemical Society.
Bioelectrochemistry (15675394) 117pp. 83-88
In the present study, a nanoporous gold platform was applied for the amplified detection of Hepatitis B virus (HBV) by an electrochemical DNA biosensor. Ferrocene as a redox reporter was covalently attached to the DNA probe and its electrochemical signal was recorded as the biosensor response. For real samples, DNA was firstly extracted from blood of patients and then amplified by polymerase chain reaction (PCR) for 5 cycles. Sensitivity of this biosensor was enhanced by using nanoporous gold electrode, therefore this sensor can discriminate the genome of HBV in real sample with low PCR cycles. By this strategy and signal amplification using nanoporous platform and covalently attached electroactive label, the biosensor can distinguish between healthy and HBV patients with limited PCR cycles. Moreover, the errors of PCR with large cycles can be disregarded. A linear dynamic range of 0.4 to 10 nmol of mutant DNA was achieved, with reliable reproducibility (RSD) 8.9%. © 2017 Elsevier B.V.
Bioelectrochemistry (15675394) 114pp. 24-32
The increasing demands for early, accurate and ultrasensitive diagnosis of cancers demonstrate the importance of the development of new amplification strategies or diagnostic technologies. In the present study, an aptamer-based electrochemical biosensor for ultrasensitive and selective detection of leukemia cancer cells has been introduced. The thiolated sgc8c aptamer was immobilized on gold nanoparticles-coated magnetic Fe3O4 nanoparticles (Apt-GMNPs). Ethidium bromide (EB), intercalated into the stem of the aptamer hairpin, provides the read-out signal for the quantification of the leukemia cancer cells. After introduction of the leukemia cancer cells onto the Apt-GMNPs, the hairpin structure of the aptamer is disrupted and the intercalator molecules are released, resulting in a decrease of the electrochemical signal. The immobilization of nitrogen-doped graphene nanosheets on the electrode surface provides an excellent platform for amplifying the read-out signal. Under optimal conditions, the aptasensor exhibits a linear response over a wide dynamic range of leukemia cancer cells from 10 to 1 × 106 cell mL− 1. The present protocol provides a highly sensitive, selective, simple, and robust method for early stage detection of leukemia cancer. Furthermore, the fabricated aptasensor was successfully used for the detection of leukemia cancer cells in complex media such as human blood plasma, without any serious interference. © 2016
Mousavi, M.F. ,
Mirsian, S. ,
Noori, A. ,
Ilkhani, H. ,
Sarparast, M. ,
Moradi, N. ,
Bathaie, S.Z. ,
Ayatollahi mehrgardi, M. Electroanalysis (15214109) 29(3)pp. 861-872
We report here a new electrochemical probe for the development of a sensitive, and selective sandwich-type electrochemical immunosensor for the detection of epidermal growth factor receptor (EGFR). The probe is a newly synthesized bovine serum albumin (BSA)-templated Pb nanocluster (PbNC@BSA). For fabrication of the immunosensor, we employed streptavidin-coated magnetic beads (MB) as a platform for immobilization of the biotinylated primary antibody (Ab1), and utilized the PbNC@BSA conjugated to secondary antibody (Ab2) as a signaling probe. After sandwiching the target protein between Ab1 and Ab2, we dissolved PbNC@BSA into an acid, and recorded square wave anodic stripping voltammetric (SWASV) signal of the Pb ions as an analytical signal for quantification of the EGFR. The immunosensor responded linearly towards EGFR within the range of 0.4 ng/mL to 35 ng/mL, with a detection limit of 8 pg/mL. The immunosensor displayed good sensitivity, selectivity, stability, and reproducibility, and proved suitable for direct measurement of EGFR in human serum samples. Moreover, we used the as-synthesized PbNC@BSA as a fluorescence label for in vitro cell viability analysis as well as bioimaging of cancerous HeLa and non-cancerous HUVEC cells. PbNC@BSA exhibited low cytotoxicity and high biocompatibility in living cells, and was a suitable fluorescent probe for live cell imaging, with potential therapeutic applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Scientific Reports (20452322) 7(1)
In the present study, a sensitive and selective signal-on method for aptamer based spectrofluorometric detection of cancer cells is introduced. AS1411, a nucleolin aptamer, is wrapped around water-soluble carbon dots and used as a probe for the detection of several types of cancer cells. Nucleolin, is overexpressed on the surface of cancer cells. Mouse breast 4T1, human breast MCF7, and human cervical HeLa cancer cells were selected as target cells, while human foreskin fibroblast cells HFFF-PI6 served as control cells. For the sensitive and selective spectrofluorimetric detection of target cancer cells in the presence of control cells, the cells were incubated in carbon dots-aptamer solutions, the cell suspensions were subsequently centrifuged and the fluorescence intensities were measured as an analytical signal. The specific targeting of cancer cells by AS1411 aptamers causes the release of carbon dots and enhances the fluorescence intensity. A calibration curve with a dynamic range between 10-4500 4T1 cells and detectability of roughly 7 cells was obtained. In addition, no significant change in the signal was detected by modifying the amount of human foreskin fibroblast control cells. Our results demonstrate similar responses to human MCF7 breast and cervical HeLa cancer cells. © 2017 The Author(s).
Analytical Methods (17599679) 8(39)pp. 7247-7253
In this work, a highly sensitive aptasensor for digoxin determination in biological samples has been introduced. The surface of a gold screen-printed electrode was modified by using electrodeposited gold nanoparticles (GNPs). A monolayer of 3-mercaptopropionic acid (MPA) was then self-assembled on the GNP surfaces. Subsequently, an amino-labeled digoxin specific aptamer was covalently bonded to the carboxylic groups of MPA on the GNPs through imide bond formation. The silver nanoparticle decorated graphene oxide (AgNPs-GO) interacted with the immobilized aptamer via π-π interaction and the oxidation signal of AgNPs was monitored. In the presence of digoxin, the hybrid left the electrode surface due to the specific interaction between the aptamer and digoxin, and the oxidation signal decreased. The proposed aptasensor delivered a linear dynamic range of 1 pM to 0.1 μM and a detection limit of 0.3 pM and was successfully utilized for digoxin determination in biological samples with good reliability. © The Royal Society of Chemistry 2016.
Journal Of Medical Signals And Sensors (22287477) 6(4)pp. 243-247
Early detection of breast cancer is the most effective way to improve the survival rate in women. Magnetic resonance imaging (MRI) offers high spatial resolution and good anatomic details, and its lower sensitivity can be improved by using targeted molecular imaging. In this study, AS1411 aptamer was conjugated to Fe3O4@Au nanoparticles for specific targeting of mouse mammary carcinoma (4T1) cells that overexpress nucleolin. In vitro cytotoxicity of aptamer-conjugated nanoparticles was assessed on 4T1 and HFFF-PI6 (control) cells. The ability of the synthesized nanoprobe to target specifically the nucleolin overexpressed cells was assessed with the MRI technique. Results show that the synthesized nanoprobe produced strongly darkened T2-weighted magnetic resonance (MR) images with 4T1 cells, whereas the MR images of HFFF-PI6 cells incubated with the nanoprobe are brighter, showing small changes compared to water. The results demonstrate that in a Fe concentration of 45 μg/mL, the nanoprobe reduced by 90% MR image intensity in 4T1 cells compared with the 27% reduction in HFFF-PI6 cells. Analysis of MR signal intensity showed statistically significant signal intensity difference between 4T1 and HFFF-PI6 cells treated with the nanoprobe. MRI experiments demonstrate the high potential of the synthesized nanoprobe as a specific MRI contrast agent for detection of nucleolin-expressing breast cancer cells. © 2016 Journal of Medical Signals and Sensors.
Electrochimica Acta (00134686) 222pp. 1483-1490
Although a monumental progress has been made in case of Human Immunodeficiency Virus researches, there are still more than 34 million people living with this viral disease. Therefore, the development of a fast and cost-effective protocol that can sensitively and selectively detect HIV gene sequence is essential. In the present study, a protocol for the molecular detection of HIV genome taking advantage of closed bipolar electrochemistry integrated with electrogenerated chemiluminescence detection is described. In this case, a closed split bipolar electrochemical cell is applied to detect the short specific oligonucleotide target of HIV1. Anthraquinone disulfonic acid, as a negative electroactive reporter, intercalates with hybridized double-strand DNA on the sensing site. By reduction of redox reporter (AQDS) on the cathodic pole, luminol is oxidized on the anodic pole and subsequent oxidized diazo product generates light that is followed using a photomultiplier tube. The experimental condition is optimized to obtain the highest sensitivity. The results demonstrate the high sensitivity and selectivity of this fast and economical method toward Human Immunodeficiency Virus genome detection in the range of 0.1 to 300 nM with the detection limit of 30 pM (S/N = 3). © 2016 Elsevier Ltd
Journal Of The Iranian Chemical Society (1735207X) 13(4)pp. 659-669
Cocaine, a powerful addictive stimulant drug, has a variety of adverse effects on the body, thus its sensitive detection is very important. Here, we report on a simple, label-free, and sensitive impedimetric sensor for determination of cocaine based on its affinity to form an inclusion complex with β-cyclodextrin (β-CD). First, we prepared nanostructured poly N-acetylaniline film via electropolymerization of its monomer on a glassy carbon electrode (PNAANI/GC), subsequently overoxidized it, and conjugated β-CD to the polymer backbone. The designed and synthesized nanostructured PNAANI film serves a dual function in the sensor: on one hand, it maintains a high effective surface area on a geometrically small electrode that significantly enhances the number of β-CD molecules immobilized on the electrode; on the other hand, it provides an upright-oriented β-CD conjugation to the polymer backbone, thus all the β-CD receptors are actively involved in responding to the target. Sensitivity of the sensor was further enhanced by preconcentration of cocaine on the modified electrode surface. We attributed the changes in the interfacial charge transfer resistance (R ct) of the electrode to cocaine concentration. Under optimized condition (pH 7.4, 5-min accumulation at an open circuit voltage), the sensor responded to cocaine concentration in the range of 100 nM-1.0 mM with a detection limit of 50 nM. Selectivity of the sensor for cocaine relative to some potential inferring compounds was also investigated, and the results were promising. The proposed approach exhibited an extended dynamic range, low detection limit, good sensitivity, and a desirable selectivity, which provides an efficient application prospect for on-field cocaine sensing. © 2015 Iranian Chemical Society.
Electroanalysis (15214109) 28(4)pp. 823-832
Scanning electrochemical microscopy (SECM) was employed for sensitive detection of single base mismatches (SBMs) in a sandwiched dsDNA. Ferrocenecarboxylic acid (Fc), covalently conjugated to the dsDNA, was oxidized to Fc+ via the DNA-mediated charge transfer from the underlying gold substrate, and reduced back to Fc by SECM tip generated ferrocyanide. The electrocatalytic oxidation of SECM tip-generated ferrocyanide was sensitive to presence, as well as the type of SBMs. Apparent standard rate constants (k0app) values for different SBMs, both near the electrode surface and far from it, were evaluated by SECM. The method can detect SBMs independent of their position in dsDNA. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
RSC Advances (20462069) 5(37)pp. 29285-29293
The main challenges in the construction of DNA biosensors for the genotyping of all the possible single-nucleotide polymorphisms (SNPs) are their sensitivity, speed and cost. The application of nanoparticle-modified monobases for the electrochemical genotyping of SNPs has been investigated in our previous study. In the present manuscript, that strategy was modified by applying a graphene-gold nanoparticle (GR-AuNPs) nanocomposite to achieve further amplification and higher sensitivity of SNPs genotyping. The present strategy shows a good potential for sensitively discriminating, quantifying and genotyping different SNPs. Taking the advantages of triple-amplification effects of AuNPs, GR and modified metal (Au and Ag) nanoparticles, this DNA biosensor exhibits highly sensitive responses for the genotyping of different SNPs and the detection of thermodynamically stable SNP (G-T) and A-C mismatch targets in the range of 10-1700 pM and 20-1200 pM with the detection limits of 2 and 10 pM (3σ) for G-T and A-C mismatch targets, respectively. The results demonstrate that when the surface coverage of DNA per unit area is just slightly increased, there is a dramatic increase in the active surface area, and the absolute loading amount of DNA on the surface would also be increased. This journal is © The Royal Society of Chemistry 2015.
Analytical Chemistry (15206882) 87(16)pp. 8123-8131
The development of simple, inexpensive, hand-held, user-friendly biosensor for high throughput and multiplexed genotyping of various single nucleotide polymorphisms (SNPs) in a single run experiment by a nonspecialist user is the main challenge in the analysis of DNA. Visualizing the signal and possibility to monitor SNPs by a digital camera opens a new horizon for the routine applications. In the present manuscript, a novel wireless electrochemiluminescence (ECL) DNA array is introduced for the visualized genotyping of different SNPs on the basis of ECL of luminol/hydrogen peroxide system on a bipolar electrode (BPE) array platform. After modification of anodic poles of the array with the DNA probe and its hybridization with the targets, genotyping of various SNPs is carried out by exposing the array to different monobase modified luminol-platinum nanoparticles (M-L-PtNPs). Upon the hybridization of M-L-PtNPs to mismatch sites, the ECL of luminol is followed using a photomultiplier tube (PMT) or digital camera and the images are analyzed by ImageJ software. This biosensor can detect even thermodynamically stable SNP (G-T mismatches) in the range of 2-600 pM. Also, by combining the advantages of BPE and the high visual sensitivity of ECL, it could be easily expected to achieve sensitive screening of different SNPs. The present biosensor demonstrates the capability for the discrimination between PCR products of normal, heterozygous, and homozygous beta thalassemia genetic disorders. © 2015 American Chemical Society.
The conjugation of biomolecules and nanostructured materials in the last decade has opened a promising horizon to many aspects of modern science. Considerable attention has been paid to the development of new nanomaterials with suitable hydrophilicity, high porosity, and large surface area for various biomolecule immobilizations. Nanostructured materials, in particular a nanoporous structure, could provide large surface area for high loading capacities for the biomolecules. A wide variety of biomolecules including proteins and nucleic acids have been employed in this field. Deoxyribonucleic acids (DNAs), Ribonucleic acids (RNAs), aptamers and aptazymes, whose functions are beyond the conventional genetic roles of nucleic acids, are collectively located in the nucleic acids (NAs) category. Also, various proteins including antibodies, enzymes, redox proteins, etc., have been applied as the recognition layer in nanoporous-based biosensors. Many approaches have been adopted for the surface functionalization of porous membranes, in which chemisorption of thiol compounds onto the surfaces of nanoporous gold (NPG) films takes place with high affinity. The NPG film modified electrodes have been used for the construction of novel label-free electrochemical immunosensors for ultrasensitive detection of cancer biomarker using specific antibodies. Nanoporous materials have made it possible to precisely immobilize enzymes and proteins while retaining or enhancing their activities and lifetimes, which is critical for enhancing biosensor performance. There is also an intriguing possibility to functionalize nanoporous materials with smart polymers in order to modulate biomolecular transport in response to either external (e.g., light and magnetic field) or internal stimuli (e.g., redox, enzymes and pH). These eff orts open up avenues to develop smart medical devices that respond to specific physiological conditions. By integrating the advantages of biomolecules with unique capabilities of NPGs such as biocompatibility and high surface activity, biomolecule functionalized nanoporous films (BM-NPG) can open the path to sophisticated design solutions for present scientific problems. The possibilities provided by BM-NPGs are enormous, and some emerging applications include diagnosis and sensing. © 2014 Scrivener Publishing LLC. All rights reserved.
Analyst (00032654) 139(20)pp. 5192-5199
In the present manuscript, a strategy to prompt the sensitivity of a biosensor based on the dual amplification of signal by applying a nanoporous gold electrode (NPGE) as a support platform and soluble graphene oxide (GO) as an indicator has been developed. By increasing the surface area of the biosensing platform and because of unique GO/ss-DNA interactions, the sensitivity for the detection of SNPs is enhanced. In the presence of SNPs, because of less effective hybridization of mutant targets compared to complementary targets, further GO could adsorb on mutant targets-modified NPGE via π–π interactions, causing a large increase in the charge transfer resistance (R ct) of the electrode. This protocol provides a cost-effective and fast method for the discrimination of different SNPs. Furthermore, this biosensor can detect thermodynamically stable SNP (G–T mismatches) in the range of 15–1600 pM. The present strategy is a label-free and sensitive protocol and does not require sophisticated fabrication. © 2014 the Partner Organisations.
ChemElectroChem (21960216) 1(4)pp. 779-786
Currently, construction of DNA biosensors for single-nucleotide polymorphisms (SNPs) genotyping is challenging, particularly in terms of speed and cost. We demonstrate a single platform for genotyping the SNPs by using electrochemical signals of modified nanoparticles (MNPs). To this end, silver and gold nanoparticles (AgNPs and AuNPs) are modified by using cysteine and cysteamine hydrochloride as linkers, respectively. The monobases are subsequently attached to the MNPs through their 5' phosphate group, forming a phosphoramidate bond with free amino groups of the linkers. Electrooxidation signals of AgNPs and/or 3, 4-diaminobenzoic acid (DABA) are monitored as analytical signals for SNP genotyping. In the presence of DNA polymeraseI (Klenow fragment), the coupling of monobase-conjugated MNPs (MMNPs) is induced to the mutant sites of duplex DNA, following the Watson-Crick base-pairing rule, which leads to a substantial change in the signal intensity of MMNPs. The method is able to distinguish complementary targets with a linear dynamic range of 20-1000pM and 50-1500pM of mutant DNA, with reliable reproducibility [relative standard deviation (RSD)=5.1% and stability (RSD=4.2%). In this study, an accurate, sensitive, fast, and cost-effective approach for SNP genotyping is introduced. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Bioelectrochemistry (15675394) 98pp. 64-69
In this manuscript, the electrocatalytic reduction of hydrogen peroxides on Prussian blue (PB) modified nanoporous gold film (NPGF) electrode is described. The PB/NPGF is prepared by simple anodizing of a smooth gold film followed by PB film electrodeposition method. The morphology of the PB/NPGF electrode is characterized using scanning electron microscopy (SEM). The effect of solution pH and the scan rates on the voltammetric responses of hydrogen peroxide have also been examined. The amperometric determination of H2O2 shows two linear dynamic responses over the concentration range of 1μM-10μM and 10μM-100μM with a detection limit of 3.6×10-7M. Furthermore, this electrode demonstrated good stability, repeatability and selectivity remarkably. © 2014 .
Analytical Chemistry (15206882) 86(10)pp. 4956-4960
Liver cancer is one of the most common cancers in the world and has no effective cure, especially in later stages. The development of a tangible protocol for early diagnosis of this disease remains a major challenge. In the present manuscript, an aptamer-based, label-free electrochemical biosensor for the sensitive detection of HepG2, a hepatocellular carcinoma cell line, is described. The target cells are captured in a sandwich architecture using TLS11a aptamer covalently attached to a gold surface and a secondary TLS11a aptamer. The application of TLS11a aptamer as a recognition layer resulted in a sensor with high affinity for HepG2 cancer cells in comparison with control cancer cells of human prostate, breast, and colon tumors. The aptasensor delivered a wide linear dynamic range over 1 × 102 to 1 × 10 6 cells/mL, with a detection limit of 2 cells/mL. This protocol provides a precise method for sensitive detection of liver cancer with significant advantages in terms of simplicity, low cost, and stability. © 2014 American Chemical Society.
Bioelectrochemistry (15675394) 94pp. 47-52
In spite of the promising applications of aptamers in the bioassays, the development of aptamer-based electrochemical biosensors with the improved limit of detection has remained a great challenge. A strategy for the amplification of signal, based on application of nanostructures as platforms for the construction of an electrochemical adenosine triphosphate (ATP) aptasensor, is introduced in the present manuscript. A sandwich assay is designed by immobilizing a fragment of aptamer on a nanoporous gold electrode (NPGE) and its association to second fragment in the presence of ATP. Consequently, 3, 4-diaminobenzoic acid (DABA), as a molecular reporter, is covalently attached to the amine-label of the second fragment, and the direct oxidation signal of DABA is followed as the analytical signal. The sensor can detect the concentrations of ATP as low as submicromolar scales. Furthermore, 3.2% decrease in signal is observed by keeping the aptasensor at 4. °C for a week in buffer solution, implying a desirable stability. Moreover, analog nucleotides, including GTP, UTP and CTP, do not show serious interferences and this sensor easily detects its target in deproteinized human blood plasma. © 2013 Elsevier B.V.
Electroanalysis (15214109) 25(7)pp. 1689-1696
The electrochemical behavior of cytochrome c (cyt-c) that was electrostatically immobilized onto a self-assembled monolayer (SAM) of captopril (capt) on a gold electrode has been investigated. Cyclic voltammetry, scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy were employed to evaluate the blocking property of the capt SAM. SECM was used to measure the bimolecular electron transfer (ET) kinetics (kBI) between a solution-based redox probe and the immobilized protein. In addition, the tunneling ET between the immobilized protein and the underlying gold electrode was calculated. A kBI value of (5.0±0.6)×108mol-1cm3s-1 for the bimolecular ET and a standard tunneling rate constant (k0) of 46.4±0.2s-1 for the tunneling ET have been obtained. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Analytical Methods (17599679) 5(22)pp. 6531-6538
In this study, a sandwich-type electrochemical DNA hybridization biosensor for the detection of single base mismatches (SBMs) has been described. 2,5-Dihydroxybenzoic acid (DHBA) is employed as a new redox probe in this study. For construction of the biosensor, thiolated capture DNA is self-assembled on a gold electrode surface and hybridized with one region of a target DNA sequence. Subsequently, a signaling amino-labeled probe DNA is hybridized to a second region of the target DNA to complete the DNA double-helix self-assembled monolayer (SAM). Finally DHBA is covalently attached to the signaling probe DNA using the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS) cross-linking reaction. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) are employed to characterize the modification steps. The electrochemical signal of DHBA was followed for studying different types of mismatches (GA, GT, TT, CA), both near the electrode surface (N-type) and far from it (F-type). The presence of a SBM leads to a considerable decrease in the electrochemical signal of DHBA compared to that of complementary DNA (cDNA), which makes the detection of mismatches (including thermodynamically stable GA mismatches) possible. The redox signal of DHBA was compared with that of methylene blue (MB) as a well-known and standard redox reporter in DNA biosensors. The results showed that for an N-type SBM, which is located between the electrode and the site of intercalation, the redox signal of MB switches off, whereas for an F-type SBM, which is located above the site of intercalation, electrons flow from the Au electrode to the intercalated MB, and hence the biosensor could not distinguish the presence and absence of an SBM. The proposed biosensor is straightforward with no need for target labeling, and is sensitive enough to detect SBMs independent of their position in DNA double helix. © 2013 The Royal Society of Chemistry.
Biosensors and Bioelectronics (18734235) 37(1)pp. 94-98
The capability of silver nanoparticles (SNP) as redox tag in the construction of an electrochemical aptasensor for the detection of adenosine triphosphate (ATP) is investigated in the present manuscript. To construct the aptasensor, a well-known ATP binding aptamer (ABA) splits into two segments. The first amino-labeled segment of the aptamer was covalently immobilized on 3-mercaptopropionic acid modified gold electrode surface by the formation of carbodiimide bond. The second segment was modified by SNPs and associated with the first segment in the presence of ATP. The direct oxidation signal of SNPs is followed as the analytical signal to detect ATP. The sandwich assay shows a suitable signal gain and importantly, a good response time. The sensor can detect the concentrations of ATP as low as micromolar scales with a desirable stability under optimum conditions. Furthermore, analog nucleotides including GTP, UTP and CTP, do not show serious interferences and this sensor readily detects its target in a complex media such as human blood plasma. © 2012 Elsevier B.V.
Biosensors and Bioelectronics (18734235) 33(1)pp. 184-189
The present manuscript describes a label free electrochemical aptasensor for the detection of sodium diclofenac (DCF). In order to construct the biosensor, the amino-functionalized diclofenac binding aptamer (DBA) was covalently immobilized on the surface of the glassy carbon electrode (GCE). The conformation of the DBAs on the surface of the electrode is changed when this is exposed to different concentrations of DCF. The introduction of DCF induces an alteration in the conformation of the surface immobilized DBA and causes a decrease in the charge transfer resistance of the aptasensor. However, the charge transfer resistance is increased by incubation of GCE/DBA/DCF in the secondary DBA. The changes in the charge transfer resistance have been monitored using the voltammetric and electrochemical impedance spectroscopic (EIS) techniques. The aptasensor shows two different linear dynamic ranges over 0-5.0μM and 10μM to 1mM, and the sensitivity of 15.7kΩμM -1 and detection limit of 2.7×10 -7M were obtained. The validity of the method and applicability of the aptasensor were successfully evaluated by detection of DCF in a blood serum sample without interference from the sample matrix. Furthermore, the aptasensor has shown good stability. © 2012 Elsevier B.V.
Advanced Materials Letters (discontinued) (09763961) 3(6)pp. 441-0
Biosensors and Bioelectronics (18734235) 38(1)pp. 252-257
The application of a nanoporous gold electrode (NPGE) in the fabrication of an electrochemical sensing system for the detection of single base mismatches (SBMs) using ferrocene-modified DNA probe has been investigated in the present manuscript. Ferrocene carboxylic acid is covalently attached to the amino-modified probe using EDC/NHS chemistry. By covalent attachment of the redox reporter molecules on the top of DNA, the direct oxidation of the ferrocene on the electrode surface is avoided. On the other hand, the electrochemical signals are amplified by anodizing the electrode surface and converting it to nanoporous form. By improving the sensitivity of the biosensor, the different SBMs including the thermodynamically stable G-A and G-T mismatches, can be easily distinguished. In this research, NPGE was prepared by anodization and chemical reduction of Au surface and used for signal amplification. Nanoporous electrode enhances the sensitivity of DNA biosensor and makes it capable to detect complementary target DNA in sub-nanomole scales. © 2012 Elsevier B.V.
Electrochimica Acta (00134686) 56(27)pp. 10264-10269
The present manuscript describes an electrochemical assay for detection of different types of single base mismatches (SBM) using 3,4-diaminobenzoic acid (DABA) as a new redox reporter. DABA is covalently attached to DNA, and its electrochemical response is followed. The present assay can overcome to two main problems of the hybridization biosensors, direct electron transfer of the redox reporter with the electrode surface and the positioning of the reporter before mismatch position. The introduced biosensor is able to discriminate complementary target and the targets including a single base mismatch even thermodynamically stable ones such as G-A and G-T. © 2011 Elsevier Ltd. All Rights Reserved.
Journal of Electroanalytical Chemistry (15726657) 650(2)pp. 214-218
In this manuscript, an electrochemical DNA hybridization biosensor which exploits long range charge transfer through double stranded DNA (ds-DNA) to copper-phthalocyanine tetrasulfonic acid - tetra sodium salt (CuPcS4) is described. Four negative charges of CuPcS4 make it a good choice to overcome two main problems of the biosensors: direct electron transfer with the electrode surface instead of charge transfer through DNA and positioning of the redox reporter before the mismatch position. The DNA recognition layer consisted of a self assembled monolayer of amino modified single stranded DNA (ss-DNA) on the surface of glassy carbon electrode (GCE). A significant increase of the peak current for CuPcS4 upon the hybridization process is observed. This biosensor can differentiate complementary target from non-complementary and also different types of single-base mismatch targets even thermodynamically stable G-A and G-T targets through diminution of voltammetric signal of CuPcS4. In addition, the position of the mismatch does not affect on the capability of the biosensor. © 2010 Elsevier B.V. All rights reserved.
Electrochimica Acta (00134686) 56(17)pp. 6224-6229
In the present manuscript, the electrochemical behavior of cytochrome c (cyt-c) immobilized onto a phenolic terminated self assembled monolayer (SAM) on a gold electrode is investigated using cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The tunneling electron transfer (ET) rate constant between the immobilized protein and the underlying electrode surface, and also the bimolecular ET rate constant between the immobilized protein and a probe has been obtained using approach curves that were obtained by SECM. The approach curves were recorded at different substrate overpotentials in the presence of various concentrations of ferrocyanide as a probe and various surface concentrations of cyt-c; then the standard tunneling ET and bimolecular rate constants are obtained as 3.4 ± 0.3 s-1 and (2.0 ± 0.5) × 107 cm3 mol-1 s-1, respectively. © 2011 Elsevier Ltd. All Rights Reserved.
Electrochimica Acta (00134686) 56(6)pp. 2725-2729
In this study, nanoparticle-functionalized nucleic acids were employed to improve the sensitivity of electrochemical DNA biosensors that make capable them to detect different types of single-base mismatches (SBMs), including thermodynamically stable ones. The present biosensor was constructed by the immobilization of platinum nanoparticles (Pt-NPs) on the surface of a carbon paste electrode (CPE) via SH-functionalized DNA. A redox probe of 2-mercapto-1-methyl imidazole (MMI), which has different electrochemical behavior on Pt-NP and CPE, was used. This behavior helps to overcome the pinhole effect in DNA hybridization biosensors. Additionally, in the present biosensor, the positioning of the redox probe under the SBM in DNA, which decreases the sensitivity of most DNA biosensors, did not contribute to the observed electrochemical signal. © 2010 Elsevier Ltd. All rights reserved.
Biosensors and Bioelectronics (18734235) 26(11)pp. 4308-4313
In this manuscript, a strategy for the amplification of the responses of an electrochemical DNA hybridization biosensor using silver nanoparticles (Ag-NPs) as redox reporters and its capability for the detection of a single base mismatches (SBM) including thermodynamically stable ones, is described. In this assay, Ag-NPs are immobilized on the top of recognition layer and their oxidation signals are followed. Differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) are used to monitoring the electrode response. Only for complementary target sequence, electron can transfer between Electrode surface and nanoparticles via DNA and Ag-NPs can be oxidized. Therefore this DNA biosensor could differentiate between complementary target and one containing either SBM or thermodynamically stable G-A and G-T targets through oxidation signal of Ag-NPs. This biosensor is able to detect SBM by overcome the direct electron transfer of redox reporter with electrode surface and positioning of it before the mismatch position. © 2011 Elsevier B.V.
Journal of Fluorescence (15734994) 21(4)pp. 1649-1658
In this work, binding of two water soluble Schiff base complexes: Bis sodium (5-sulfosalicylaldehyde) o- phenylendiiminato) Manganese (III) acetate (Salophen complex) and Bis sodium (5-sulfosalicylaldehyde) 1, 2 ethylendiiminato) Manganese (III) acetate (Salen complex) with calf thymus (ct) DNA were investigated by using different spectroscopic and electrometric techniques including UV-vis, Circular dichroism (CD) and fluorescence spectroscopy, viscommetry and cyclic voltammetry (CV). Both complexes have shown a hyperchromic and a small bathochromic shift in the visible region spectra. A competitive binding study showed that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by the addition of the two Schiff base complexes indicating that they displace EB from its binding site in DNA. Moreover structural changes in the CD spectra and an increase in the CV spectra with addition of DNA were observed. The results show that both complexes bind to DNA. The binding constants have been calculated using fluorescence data for two complexes also K b was calculated with fluorescence Scatchard plot for Salophen. Ultimately, the experimental results show that the dominant interactions are electrostatic while binding mode is surface binding then followed by hydrophobic interactions in grooves in high concentration of complexes. © Springer Science+Business Media, LLC 2009.
Electrochimica Acta (00134686) 56(2)pp. 896-904
Electron transfer (ET) kinetics through n-dodecanethiol (C12SH) self-assembled monolayer on gold electrode was studied using cyclic voltammetry (CV), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS). An SECM model for compensating pinhole contribution, was used to measure the ET kinetics of solution-phase probes of ferrocyanide/ ferricyanide (Fe(CN)64-/3-) and ferrocenemethanol/ ferrociniummethanol (FMC0/+) through the C12SH monolayer yielding standard tunneling rate constant (kET0) of (4 ± 1) × 10-11 and (3 ± 1) × 10-10 cm s-1 for Fe(CN)64-/3- and FMC0/+ respectively. Decay tunneling constants (β) of 0.97 and 0.96 -1 for saturated alkane thiol chains were obtained using Fe(CN)64- and FMC respectively. Also, it was found that methylene blue (MB) molecules are effectively immobilized on the C12SH monolayer and can mediate the ET between the solution-phase probes and underlying gold substrate. SECM-mediated model was used to simultaneously measure the bimolecular ET between the solution-phase probes and the monolayer-immobilized MB molecules, as well as tunneling ET between the monolayer-immobilized MB molecules and the underlying gold electrode, allowing the measurement of kBI = (5 ± 1) × 106 and (4 ± 2) × 107 cm3 mol-1 s-1 for the bimolecular ET and kET/MB0=(10.3) ×10-3 and (7 ± 3) × 10-2 s-1 for the standard tunneling rate constant of ET using Fe(CN)64-/3- and FMC0/+ probes respectively. © 2010 Elsevier Ltd. All rights reserved.
Journal of Electroanalytical Chemistry (15726657) 644(1)pp. 44-49
In this study, the electrochemical behavior of thianthrene (TH) and its application toward the electrocatalytic oxidation of guanosine (Gs) and DNA in a non-aqueous solution are investigated using different voltammetric techniques. Guanosine and DNA are adsorbed on the glassy carbon electrode (GCE) by applying a positive potential to the GCE. The rate constant of catalytic reaction between DNA and TH and also between Gs and TH were evaluated using chronoamperometry which gave rate constants of 2.41 × 106 cm3 mol-1 s-1 and 2.68 (±0.19) × 106 cm3 mol-1 s-1, respectively. Also the diffusion coefficient of TH was obtained using hydrodynamic voltammetry (3.17 × 10-5 cm2 s-1). Furthermore, using hydrodynamic voltammetry, a one-electron mechanism for oxidation of Gs is suggested. © 2010 Elsevier B.V. All rights reserved.
Russian Journal of Physical Chemistry A (00360244) 84(13)pp. 2284-2289
In the present study, at first, N,N'-bis(3,4-dihydroxyhenzylidene)-1,2- diaminobenzene (BDBDAB), has been synthesized by combination of 1,2-diaminobenzene and 3,4-dihydroxybenzaldehyde in a solvent system. These ligand containing ortho-quinone functional groups were characterized using UV-VIS and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and BDBDAB was investigated in 10 mM Tris-HCl buffer solution, pH 7.2, using UV-visible absorption and fluorescence spectroscopies, thermal denaturation technique, viscosity measurement, and cyclic voltametry. From spectrophotometric titration experiments, the binding constants of BDBDAB with double stranded DNA were found to be (0.9 ± 0.1) × 104 M -1. The magnitude of the interaction between the ligands and DNA can be quantified by using the Stern-Volmer equation. From the plot of I0/I versus [DNA]/[BDBDAB] the quenching constants (KSV) were obtained and found to be 5.6 ± 0.2. Thermal denaturation experiments represent the increasing of melting temperature of DNA (about 3.2°C) due to binding of BDBDAB. There is no increasing of viscosity was observed in addition of BDBDAB to DNA. The electroactivity of the quinone moiety in N,N'-bis(3,4- dihydroxybenzylidene)-1,2-diaminobenzene bound to DNA could be employed as cyclic voltametry to obtain binding constant. These results suggest that interaction with the grooves could be the principal mode of binding of BDBDAB to double stranded ct-DNA. © 2010 Pleiades Publishing, Ltd.
Electrochimica Acta (00134686) 54(20)pp. 4638-4646
The morphology and ion transport characteristics of polyaniline (PANI) films on a platinum electrode were investigated using scanning electrochemical microscopy method (SECM). An ultramicroelectrode (UME) tip was positioned close to the surface of a PANI-modified substrate electrode, and the current signal at the tip and substrate electrodes, during a substrate potential step or linear sweep were monitored simultaneously. Proton transport occurred on the PANI film at a pH of 6 during the first and second redox cycles of PANI was monitored at this pH. The chemical reaction pathway of PANI as a function of substrate potential was analyzed. Different species of degradation products were detected electrochemically at the SECM tip. Benzoquinone (BQ) was found to be the major product of anodic degradation of PANI. Chemical imaging of the anodic degradation of PANI was performed by SECM during applying different potential steps to the PANI. The anodic threshold of 0.75 V was suggested as the potential at which degradation of PANI begins. © 2009 Elsevier Ltd. All rights reserved.
Analytical Chemistry (15206882) 78(19)pp. 6959-6966
The electrochemical behavior of electrodes made by sealing carbon nanofibers in glass or with electrophoretic paint has been studied by scanning electrochemical microscopy (SECM). Because of their small electroactive surface area, conical geometry with a low aspect ratio and high overpotential for proton and oxygen reduction, carbon nanofiber (CNF) electrodes are promising candidates for producing electrode nanogaps, imaging with high spatial resolution and for the electrodeposition of single metal nanoparticles (e.g., Pt, Pd) for studies as electrocatalysts. By using the feedback mode of the SECM, a CNF tip can produce a gap that is smaller than 20 nm from a platinum disk. Similarly, the SECM used in a tip-collection substrate-generation mode, which subsequently shows a feedback interaction at short distances, makes it possible to detect a single CNF by another CNF and then to form a nanometer gap between the two electrodes. This approach was used to image vertically aligned CNF arrays. This method is useful in the detection in a homogeneous solution of short-lifetime intermediates, which can be electrochemically generated at one electrode and collected at the second at distances that are equivalent to a nanosecond time scale. © 2006 American Chemical Society.
Abbaspour, A. ,
Ayatollahi mehrgardi, M. ,
Noori, A. ,
Kamyabi, M.A. ,
Khalafi-nezhad, A. ,
Rad, M.N.S. Sensors and Actuators B: Chemical (09254005) 113(2)pp. 857-865
A new methodology for construction of a sensor array, to acquire signal patterns, is discussed in this article. This sensor is constructed by immobilizing an ionophore on a piece of paper (or porous material such as thin layer chromatography (TLC) plate) followed by charge coupled device (CCD) camera-based detection. This allows us to use non-transparent porous materials as a support for immobilization of ionophore. Changes in RGB values of color spots on pH paper or TLC strips create a pattern. The obtained pattern was analyzed using Microsoft Excel Solver. Full-range pH monitoring and speciation of ferric and ferrous ions in solution are discussed. A commercial multi-color pH strip was used as a typical prototype for full-range pH monitoring, and 4-methyl-2,6-bis (hydroxymethyl)phenol (or its halo-derivatives) and 1,10-phenanthroline were used as ionophores for determination of Fe(III) and Fe(II), respectively. Results of analyzed patterns showed a good correlation between predicted and true values of pH (r = 0.9986), Fe(II) (r = 0.9989) and Fe(III) (r = 0.9978) with acceptable relative standard error. © 2005 Elsevier B.V. All rights reserved.
Talanta (00399140) 67(3)pp. 579-584
The electrochemical behavior of Ce(III) ion in the presence of EDTA and their application for electrocatalytic oxidation of nitrite ion is described in this manuscript. The electrochemical properties of Ce(III)-EDTA complex as well as the two-electron oxidation of nitrite ion were investigated using cyclic voltammetry and hydrodynamic voltammetry methods. Kinetic parameters such as transfer coefficient, homogeneous rate constant for electrocatalytic oxidation of nitrite ion at the experimental conditions, were obtained. Also the possible mechanism for oxidation of nitrite ion using Ce(III)-EDTA complex is proposed. The detection limit of 4.8 × 10-6 M and dynamic linear range 1.0 × 10-5 to 1.0 × 10-2 M were obtained for determination of nitrite ion using electrocatalytic oxidation of this ion by Ce(III)-EDTA complex. © 2005 Elsevier B.V. All rights reserved.
Analytical Chemistry (15206882) 76(19)pp. 5690-5696
The electrochemical behavior of cobalt hexacyanoferrate complex adsorbed on a carbon paste electrode (CPE) and its application to the electrocatalytic oxidation of guanine and single-strand DNA (ss-DNA) in aqueous solution are investigated in this report The modification of CPE by the adsorption of this complex results in excellent amplification of the guanine oxidation response of ss-DNA. The effects of paste composition, scan rate, DNA, and guanine concentration were studied. The detection limits of 52 and 920 ng mL -1 were obtained for guanine and ss-DNA, respectively.
Journal of Electroanalytical Chemistry (15726657) 568(1-2)pp. 261-266
The utility of carbon paste electrodes (CPE) modified with cobalt(II) phthalocyanine for electrocatalytic oxidation of guanine and single strand DNA (ss-DNA) in aqueous solution is demonstrated. The modification of a CPE with this compound results in excellent amplification of the guanine oxidation response of ss-DNA. The electrochemical behavior of the modified electrode and the mechanism of the oxidation of guanine and ss-DNA were investigated using cyclic voltammetry and rotating disk electrode methods. The transfer coefficient (α) for electrocatalytic oxidation of guanine and the diffusion coefficient of this substance under the experimental conditions were investigated in this study. Detection limits of 85 and 280ng mL-1 were obtained for guanine and ss-DNA, respectively. © 2004 Elsevier B.V. All rights reserved.
Separation and Purification Technology (13835866) 33(1)pp. 95-101
A new adsorbent for preconcentration and separation of silver ion from aqueous sample solutions has been reported. Sodium dodecyl sulfate (SDS), as a surfactant, makes admicelle on the surface of substrate γ-alumina, which allows the metal complexing agent, 2-mercaptobenzothiazole (MBT), to be immobilized in its hydrocarbon cores. This assemble, as a chelating adsorbent, has made the separation and preconcentration of silver ion possible. Factors influencing the adsorption of μg/ml levels of silver ion concentration from solutions by the adsorbent have been investigated. A preconcentration factor of 100 has been found. An aqueous solution containing thiourea has been used in order to selectively desorb the adsorbed silver ion from the surface of the adsorbent, which is a new stripping technique that is introduced in solid-phase extraction methods. No serious interferences have been observed due to the presence of another species in the sample. The separation selectivity of the adsorbent for other cations was studied. To improve this, EDTA was added to the source solution before applying to the column. The method is simple and inexpensive. © 2003 Elsevier Science B.V. All rights reserved.
