An efficient colorimetric biosensor for glucose based on peroxidase-like protein-Fe3O4 and glucose oxidase nanocomposites

•Protein-magnetite nanoparticles possess enhanced peroxidase-like activity.•Glucose biosensor based on biocompatible protein-Fe3O4 nanocomposite is developed.•The biosensor exhibits an excellent performance toward glucose detection in a colorimetric way.

An efficient colorimetric biosensor for glucose based on peroxidase-like protein-Fe3O4 and glucose oxidase nanocomposites is reported in this work. Compared with bare MNPs, peroxidase-like casein-MNPs exhibit good catalytic properties, stability, dispersibility. Casein incorporated on MNPs notably improves the affinity toward both H2O2 and TMB, proved by variation in the determined kinetic parameters. As low as 0.2 μM H2O2 can be detected with a linear range from 0.5 μM to 200 μM H2O2. More importantly, the casein/MNP nanocomposite was further used to immobilize GOx and to construct a glucose biosensor for the one-step determination of glucose. This method is simple, inexpensive, highly sensitive, and selective for glucose detection, with a detection limit of 1.0 μM over a linear range from 3 μM to 1000 μM.