Role of fluorosurfactant-modified gold nanoparticles in selective detection of homocysteine thiolactone: Remover and sensor

In this article, we report a simple approach for the selective sensing of homocysteine thiolactone (HTL) using fluorosurfactant (FSN)-capped gold nanoparticles (AuNPs) as aminothiol removers and as sensors. We have shown that HTL did not bind to the surface of the FSN-AuNPs in the pH range of 4.0-10.0. In contrast, under these pH conditions, the FSN-AuNPs are aggregated upon the addition of homocysteine (HCys) and cysteine (Cys). On the basis of this feature, we have demonstrated that FSN-AuNPs are effective sorbent materials for HCys and Cys, but not for HTL. It is found that the FSN-AuNPs can remove of >98% of HCys and >99% of Cys from an aqueous solution. Thus, after the centrifugation of a solution containing AuNPs, HTL, and other aminothiols, only HTL remains in the supernatant. When NaOH is added to the supernatant, HTL is hydrolyzed to HCys, leading to the aggregation of the FSN-AuNPs. As a result, the selectivity of the probe is significantly higher for HTL in aqueous solutions than for other aminthiols. The sensitivity of FSN-AuNPs toward HTL can be further improved by optimizing the AuNP concentrations. Under optimum conditions, the lowest detectable concentration of HTL through this approach is 100 nM. We have validated the applicability of our method through the analyses of HTL in urine samples.