A label-free gold nanocluster fluorescent probe for protease activity monitoring.

Water soluble BSA-stabilized gold nanoclusters (Au NCs) were synthesized with a simple one-pot procedure. The as-prepared Au NCs were able to emit intensive red fluorescence under the excitation of ultraviolet light, and the fluorescence could be quenched by enzymatic hydrolysis. In this contribution, BSA-stabilized Au NCs as novel fluorescent probes were successfully utilized for the detection and real-time monitoring of proteolytic activity of trypsin and chymotrypsin. High performance liquid chromatography-inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, and X-ray absorption fine structure were performed to investigate the quenching mechanism, and the results indicated that BSA scaffold degradation caused by enzymatic proteolysis led to the decrease in fluorescence intensity. Furthermore, this method would be potentially extended to the detection of other enzymes with Au NCs stabilized by different biomolecules.