Bovine serum albumin-confined silver nanoclusters as fluorometric probe for detection of biothiols

Fluorescent bovine serum albumin-confined silver nanoclusters (BSA-AgNCs) were demonstrated to be a novel and environmentally friendly probe for the rapid detection of biothiols such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH). The sensing was ascribed to the strong affinity between the mercapto group of the biothiols and the silver nanoclusters. The fluorescence intensity of BSA-AgNCs was quenched efficiently on increasing the concentration of biothiol, corresponding with a red-shift in emission wavelength. However, the fluorescence of the silver nanoclusters was almost unchanged in the presence of other α-amino acids at 10-fold higher concentrations. By virtue of this specific response, a new, simple and rapid fluorescent method for detecting biothiols has been developed. The linear ranges for Cys, Hcy and GSH were 2.0 × 10^-6to 9.0 × 10^-5M (R²= 0.994), 2.0 × 10^-6to 1.2 × 10^-4M (R²= 0.996) and 1.0 × 10^-5to 8.0 × 10^-5M (R²= 0.980), respectively. The detection limits were 8.1 × 10^-7M for Cys, 1.0 × 10^-6M for Hcy and 1.1 × 10^-6M for GSH. Our proposed method was successfully applied to the determination of thiols in human plasma and the recovery was 94.83-105.24%. It is potentially applicable to protein-stabilized silver nanoclusters in a chemical or biochemical sensing system.