Poly-adenine-thymine-mediated gold nanoparticle-based colorimetric and Tyndall effect dual-mode sensing of amoxicillin

The widespread use of amoxicillin plays an important role to treat numerous bacterial diseases, but has led to the risks and challenges to aquatic environment and human health. Therefore, an accurate, economical and efficient detection and quantification of amoxicillin is essential to trace it in environment. Herein, a colorimetric and Tyndall effect (TE)-based dual-mode sensing platform was developed to detect amoxicillin with gold nanoparticles (AuNPs) as the signaling labels. AuNPs conjugated with a triblock nucleotide composed of polyadenine (polyA), polythymine (polyT) and aptamer was designed as the probes. The folding of DNA aptamers towards amoxicillin enhanced the stability of AuNPs in salt solution while the AuNPs probes aggregated without target bound. Thus, the colorimetric and TE signals were generated by the aggregation/dispersion of AuNPs probes. Furthermore, the polyA and polyT design could facilitate the detection for amoxicillin by modulating the length of polyA and polyT blocks. The colorimetric mode allowed the screening of amoxicillin in the range of 25–400 nM with the limit of detection of 22.58 nM, and the TE mode supported the same quantitative detection range of amoxicillin but an improved limit of detection as 16.75 nM. Overall, this proposed dual-mode sensing technique not only enables reliable, robust detection and self-confirmation of detection results, but also provides great prospects to be extended for the analysis of other antibiotics.