Cellulose membrane-based enzymatic colorimetric biosensors based on -glucosidase immobilization via Schiff-base reaction for rapid screening of its inhibitors

This study constructed a cellulose membrane (CM)-based enzymatic colorimetric biosensor with high storage, long-term stability, and rapid screening. CM was oxidized by sodium periodate (OCM), and the C2-C3 position hydroxyl group (-OH) on the CMs was oxidized to the aldehyde group (-CHO). The amino group (-NH2) of alpha-glu and the -CHO on OCM immobilized alpha-glu reacted through a simple Schiff base reaction to obtain Schiff-based CM (SCM), which could screen AGIs rapidly within only 80 sec. The screening mechanism was that 4-Nitrophenyl alpha-D-glucopyranoside (PNPG) under the catalysis of alpha-glu produces yellow 4-Nitrophenyl (PNP), which through physical absorption immobilized on SCM immediately renders the SCM colorless to yellow. When acarbose was added, it was competitively bound to the active site of alpha-glu so that alpha-glu could not catalyze PNPG to produce PNP, thereby reducing the color intensity of SCM. SCM inherited CM's highly loose interpenetrating porous morphology was exhibited by FESEM results, providing many channels and sites for immobilizing alpha-glu. The VLOD of SCM is 5 x 10(-4) mM in the linear range of acarbose from 0 to 0.6 mM, and the IC50 was 16.77 mu M. After 120 days of storage at 4 degrees C, the color intensity was lost less than 10 %.