Fluorescence for the determination of protein with functionalized nano-ZnS

ZnS nanoparticles have been prepared and modified with sodium thioglycolate. The functionalized nanoparticles are water-soluble. They were used as fluorescence probes in the determination of proteins, which was proved to be a simple, rapid and specific method. In comparison with single organic fluorophores, these nanoparticle probes are brighter, more stable against photobleaching, and do not suffer from blinking. Under optimum conditions, linear relationships were found between the enhanced intensity of fluorescence at 441 nm and the concentration of protein in the range 0.1-4.0 mug mL(-1) for human serum albumin (HSA), 0.2-3.0 mug mL(-1) for bovine serum albumin (BSA) and 0.1-4.5 mug mL(-1) for gamma-globulin (gamma-G). The limits of detection were 0.015 mug mL(-1) for HSA, 0.024 mug mL(-1) and 0.017 mug mL(-1) for BSA and gamma-G, respectively. The method has been applied to the analysis of human serum samples collected from the hospital and the results were in good agreement with those reported by a hospital, indicating that the method presented here is not only sensitive and simple, but also reliable and suitable for practical application.