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 0.05–0.9 mM and 0.00625–0.6 mM 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 × 10−5 mM and 3.48 × 10−4 mM cholesterol respectively according to S/N = 3 ratios. Kinetic parameters, such as Km and Imax operational and storage stabilities, effects of pH and temperature were determined for both enzyme electrodes.