Comparison of Effective Working Electrode Areas on Planar and Porous Silicon Substrates for Cholesterol Biosensor

Abstract

Porous silicon-based biosensors were originally developed to further stet the miniaturization of a host of devices. In this paper, we describe the relationship between the enlargement of an electrode's area and its sensitivity for the determination of cholesterol concentrations with covalent binding to immobilized enzymes. For comparison, we conducted a series of experiments using a planar silicon electrode and a porous silicon electrode. We determined the effective surface area of the electrodes using the Randles–Sevcik equation. The active surface area of the planar electrode was approximately 0.1608 cm2, and that of the porous electrode was approximately 0.5054 cm2. Cholesterol oxidase was covalently immobilized on each electrode by silanization. The sensitivities were 0.08567 µA/mM for the planar sensor and 0.2656 µA/mM for the porous sensor. The calculated effective surface area and sensitivity of the porous electrode were about 3.1-fold larger than those of the planar electrode.