Novel Photoelectrochemical Biosensors for Cholesterol Biosensing by Photonic " Wiring" of Cholesterol Oxidase

In this study, a novel approach for constructing different very sensitive and efficient photoelectrochemical biosensors called as P(SNS-NH2)/ChOx/[Ru(bpy)(3)](2+) and ChOx/[Ru(bpy)(3)](2+), were fabricated by bonding ChOx covalently to P(SNS-NH2) modified electrode and bare thioaniline modififed gold slide, respectively, using gluteraldehyde and tethering the N-hydroxysuccinimidyl ester functionalized Ru(II)-trisbipryridine to the ChOx enzyme. In the presence of different concentrations of cholesterol, the photocurrents were obtained by irradiating of the photoelectrochemical cell containing P(SNS-NH2)/ChOx/[Ru(bpy)(3)](2+) or ChOx/[Ru(bpy)(3)](2+) electrode as the anode under air. The bipyridine complex [Ru(bpy)(3)](2+) was used to activate photoinduced electron-transfer reaction and it acted as a redox mediator to activate the bioelectrocatalytic functions of ChOx. Therefore, it was shown the photonic electron-transfer wiring of ChOx with the electrode. ChOx/[Ru(bpy)(3)](2+) and P(SNS-NH2)/ChOx/[Ru(bpy)(3))(2+) biosensors showed a very good linearity between 0.05-0.9mM and 0.00625-0.6mM for cholesterol respective. LOD values for P(SNS-NH2)/ChOx/[Ru(bpy)(3))(2+) and ChOx/[Ru(bpy)(3))(2+) electrodes were obtained as 9.86 x 10(-5) mM and 3.48 x 10(-4) mM cholesterol respectively according to S/N = 3 ratios. Kinetic parameters, such as K-m and I-max operational and storage stabilities, effects of pH and temperature were determined for both enzyme electrodes.