Multi-cascade signal amplification and structure modulation strategy for highly sensitive and selective detection of cysteine using bovine serum albumin-stabilized gold nanoflowers as signal mediator

A novel nanosensing system was constructed for highly sensitive and selective detection of cysteine (Cys) via the combination of the excellent optical properties of bovine serum albumin-stabilized gold nanoflowers (BSA-AuNFs), the high selectivity of the molecular structure regulation performance of cystine, and the high sensitivity of the multi-cascade signal amplification strategy. The sensing mechanism has been confirmed by UV–vis absorption spectroscopy, TEM, HRMS and 1 H NMR spectra titration analysis, which can effectively improve the sensitivity and selectivity of the detection of Cys. In addition, the molecular structure regulation performance of cystine (disulfide bond effect) further improved the selectivity of this analytical system. Moreover, it is worth noting that the BSA-AuNFs prepared by ultrafast synthesis procedure have a unique spatial structure, which can effectively prevent the interaction with large-sized biothiols (Cys, homocysteine (Hcy), glutathione (GSH)), achieving highly selective detection of Cys in human serum. This is unable to be achieved by using AuNFs prepared via the gold seed method (Gs-AuNFs) as the gold active sites of Gs-AuNFs are completely exposed. These results indicated that the cascade signal amplification sensing strategy with a clear response mechanism has good application prospects in physiological and pathological research.