A novel, simple, sensitive, and selective fluorometric method was developed for measuring trypsin in biological samples in this article. The method was based upon measuring the quenching of the fluorescence intensity of the bovine serum albumin (BSA) stabilized Au nanoclusters by enzymatic proteolysis. The calibration plot for trypsin was achieved over the concentration range 1-60 nmol L-1 with a correlation coefficient of 0.995 and a limit of detection of 0.6 nmol L-1. The method was also used satisfactorily for the assessment of the trypsin activity and the results showed that the Michaelis-Menten (Km) and catalytic (Kcat) constant values of trypsin for BSA-Au nanoclusters substrate were 1.6×10-5 mol L-1 and 3.8 s-1 at 37 ºC, respectively. This enzyme biosensor is of considerable interest due its promise for simple procedure and the established method has great potential in detection of other proteases in clinical diagnostics of various diseases.
BSA-Au nanoclusters; trypsin; fluorescence; enzyme activity
