Optical determination of glucose and hydrogen peroxide using a nanocomposite prepared from glucose oxidase and magnetite nanoparticles immobilized on graphene oxide

Fe3O4 nanoparticles were deposited on sheets of graphene oxide (GO) by a precipitation method, and glucose oxidase (GOx) was then immobilized on this material to produce a GOx/Fe3O4/GO magnetic nanocomposite containing crosslinked enzyme clusters. The 3-component composite functions as a binary enzyme that was employed in a photometric method for the determination of glucose and hydrogen peroxide where the GOx/Fe3O4/GO nanoparticles cause the generation of H2O2 which, in turn, oxidize the substrate N,N-diethyl-p-phenylenediamine to form a purple product with an absorption maximum at 550 nm. The absorbance at 550 nm can be correlated to the concentration of glucose and/or hydrogen peroxide. Under optimized conditions, the calibration plot is linear in the 0.5 to 600 mu M glucose concentration range, and the detection limit is 0.2 mu M. The respective plot for H2O2 ranges from 0.1 to 10 mu M, and the detection limit is 0.04 mu M. The method was successfully applied to the determination of glucose in human serum samples. The GOx/Fe3O4/GO nanoparticles are reusable.