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 H2O2 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 H2O2 of less than 10 s and an excellent linear relationship was obtained in the concentration range 0.20 mu mol L-1 -0.68 mmol L-1, with a detection limit of 0.078 mu mol L-1 (S/N = 3) under the optimum conditions. The response showed Michaelis-Menten behavior at larger H2O2 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.
Analytical and Bioanalytical Chemistry,
Vol. 390, no. 3 (Feb 2008), pp. 971-977