Development of a Highly Sensitive SPR Biosensor for BCR–ABL Gene Sequence Detection Using a Novel Gold Nanoparticle–Enhanced Sandwich Assay Format

SPR (surface plasmon resonance) biosensor–based analytical methods enable rapid, straightforward, and cost-effective detection of DNA oligonucleotides. However, the detection limits of currently available SPR biosensors for BCR–ABL gene oligonucleotides remain too high to reliably detect sub-nanomolar concentrations. This study presents a new signal-enhancement approach for SPR DNA biosensors based on a gold nanoparticle (AuNP) sandwich assay. In this work, we demonstrated that AuNP-modified oligonucleotides can serve as labels that significantly amplify the SPR biosensor response in a sandwich-type SPR DNA biosensor. The analytical characteristics of the developed AuNP-labeled biosensor for detection of BCR–ABL fusion gene oligonucleotides were studied. The AuNP-labeled biosensor exhibited a detection limit of 80 pM, which is significantly lower than that of a traditional label-free SPR biosensor (50 nM). The measurement error for BCR–ABL target detection was significantly lower with the AuNP-labeled biosensor than with the label-free SPR biosensor. The conditions of synthesis of AuNPs by citrate reduction of AuCl3 that allow the monodisperse size distribution and absence of AuNP aggregation were established as well. Based on the obtained data, we conclude that a sandwich assay employing AuNP-modified oligonucleotides as labels is a promising approach for the highly sensitive detection of genetic markers. The developed AuNP-labeled DNA biosensing approach can be adapted to enhance the signal in other DNA hybridization-based SPR biosensors.