A Colorimetric Approach to Identifying Single-Nucleotide Mutations Using Gold-Based Magnetic Nanoparticles

Detection of single-nucleotide mutations (SNPs) in the genome of infectious agents is one of the ways to identify their drug-resistant strains. Antibiotic-resistant strains of Mycobacterium tuberculosis (MTB) impede advances in the fight against the spread of tuberculosis. Diagnostic tools exist for both MTB itself and its drug-resistant strains, most of which are technically complex, resource-intensive, and time-consuming. This paper presents the development of a colorimetric test system, requiring no expensive equipment, for the rapid and accurate determination of the SNPs associated with drug-resistant forms of MTB to fluoroquinolones in modeled DNA targets (198 bp). For this purpose, nanoconstructs based on gold nanoparticles (AuNPs) and hybrid magnetic Fe₃O₄@Au NPs were created, leveraging the advantages of each nanomaterial. The use of AuNPs provides a basis for colorimetric detection due to their high optical absorption. Fe₃O₄@Au NPs enable samples to respond to an external magnetic field. The study demonstrates the ability to reliably discriminate between wild-type and mutant-model DNA targets in the nanomolar concentration range within 15 min. Visual analysis and optical absorption spectroscopy were used to evaluate the detection results. The application of an external magnetic field allows for enhanced colorimetric distinction between wild-type target samples and those containing an SNP.