Sensitive trypsin sensor based on the regulation of microscale ionic current rectification by the selectivity hydrolysis of hydrogel filled in microchannel.

Filling the microchannel with negatively charged hydrogel can exhibit microsacle ion current rectification (ICR) behavior, which is attributed to the space negative charge and structural asymmetry of hydrogel. In this study, this character had been applied to develop a trypsin sensor for the first time. A hydrogel synthesized with bovine serum albumin (BSA) and glyoxal (BSAG hydrogel) was filled at the tip of microchannel firstly. Subsequently, the BSAG hydrogel-filled microchannel was immersed in a trypsin solution to hydrolyze the BSA within the BSAG hydrogel. This process changes the space charge density and pore size of the BSAG hydrogel-filled microchannel, leading to a change in microscale ICR, which can be used for quantifying trypsin. Then the key parameters affecting the sensing performance such as the concentration of BSA, strength of the electrolyte, pH and reaction time were optimized. The detection range was from 10.0 ng/mL to 100 μg/mL with a detection limit as low as 2.55 ng/mL (S/N = 3). Due to the distinctive three-dimensional pore structure of the hydrogel and the specificity of trypsin for BSA hydrolysis, the sensor exhibits high sensitivity and specificity, as well as remarkable reproducibility and stability. This sensor has been effectively used to measure trypsin levels in human serum samples.