A Novel "Off-On-Off" Fluorescent Sensor Based On Inner Filter Effect For Ultrasensitive Detection Of Protamine/Trypsin And Subcellular Colocalization

Protease is an important physiological enzyme that can catalyze the hydrolysis of peptide bonds at specific sites and trypsin is a proteolytic enzyme present in the pancreas, the fluctuation of whom reflect dysfunction of body. Thus, it is necessary to develop sensitivity detections for protamine and trypsin. Herein, an "off-on-off" fluorescent sensor based on the inner filter effect was established for individually quantification of protamine and trypsin by using silicon quantum dots (SiQDs) and triangular silver nanoprisms (TSNPRs) based on the inner filter effect (IFE). The maximum absorption peak position of TSNPRs is 550 nm, which completely overlaps the emission peak (536 nm) of SiQDs and considerably improves sensitivity of the sensor. The proposed IFE-based sensor proved a good linearity from 0-30 ng/mL for protamine determination with detection limit of 5 ng/ mL. For trypsin detection, the constructed sensor displayed a liner detection range from 0 to 40 ng/mL with a detection limit of 8 ng/mL. Besides, the SiQDs have equipped with the excellent capability for subcellular colocalization, providing a promising potential for practical applications.