An amperometric hydrogen peroxide biosensor based on immobilization of horseradish peroxidase on an electrode modified with magnetic dextran microspheres.

A new kind of magnetic dextran microsphere (MDMS) with uniform shape and narrow diameter distribution has been prepared from magnetic iron nanoparticles and dextran. Horseradish peroxidase (HRP) was successfully immobilized on the surface of an MDMS-modified glassy-carbon electrode (GCE), and the immobilized HRP displayed excellent electrocatalytic activity in the reduction of H(2)O(2) in the presence of the mediator hydroquinone (HQ). The effects of experimental variables such as the concentration of HQ, solution pH, and the working potential were investigated for optimum analytical performance. This biosensor had a fast response to H(2)O(2) of less than 10 s and an excellent linear relationship was obtained in the concentration range 0.20 micromol L(-1)-0.68 mmol L(-1), with a detection limit of 0.078 micromol L(-1) (S/N = 3) under the optimum conditions. The response showed Michaelis-Menten behavior at larger H(2)O(2) concentrations, and the apparent Michaelis-Menten constant K(M)(app) was estimated to be 1.38 mmol L(-1). Moreover, the selectivity, stability, and reproducibility of the biosensor were evaluated, with satisfactory results.