Rich-color visual genotyping of single-nucleotide polymorphisms based on platinum nanoparticle–induced etching of gold nanorods

Abstract

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.