Preparation of Porous Titania Sol−Gel Matrix for Immobilization of Horseradish Peroxidase by a Vapor Deposition Method

A new and facile vapor deposition method has been developed for the preparation of sol−gel matrix. This method was used to form a titania sol−gel thin film and to immobilize horseradish peroxidase (HRP) on a glassy carbon electrode surface for the production of an amperometric hydrogen peroxide biosensor. This process prevented the cracking of conventional sol−gel-derived glasses. The morphologies of both titania sol−gel and the enzyme membranes were characterized using scanning electron microscopy and proved to be chemically clean, porous, and homogeneous and to have a very narrow particle size distribution. The sol−gel-derived titania-modified electrode retained the enzyme bioactivity and provided for long-term stability of the enzyme in storage. In the presence of catechol as a mediator, the sensor exhibited a rapid electrocatalytic response (less than 5 s), a linear calibration range from 0.08 to 0.56 mM with a detection limit of 1.5 μM and a high sensitivity (61.5 μA mM-1) for monitoring of H2O2. Effects of pH and operating potential were also explored for optimum analytical performance by using the amperometric method. The apparent Michaelis−Menten constant of the encapsulated HRP was 1.89 ± 0.21 mM.