Photoelectrochemical determination of oxidase activity based on photoinduced direct electron transfer of protein by using a convenient photoelectrochemical detector

Abstract In order to fabricate the enzyme-labelled photoelectrochemical biosensor without redox mediators, a new method using chitosan to dissolve samples and transmit electrons was proposed to achieve the direct electron transfer between the oxidase and ZnO nanorods photoelectrode. Based on this strategy, activities of glucose oxidase and cholesterol oxidase were determined through using a novel photoelectrochemical detector matched with the method. Under optimized experimental conditions, the logarithm of photocurrent increase displayed a linear relationship to the logarithm of glucose oxidase or cholesterol oxidase concentrations in the range from 0.1–2.50 U/mL or from 0.1–4.00 U/mL, respectively, with correlation coefficients of 0.9976 and 0.9968, and the detection limits estimated by the correction curves were 0.05 and 0.08 U/mL. The results of the investigation further showed that the relative standard deviation was less than 5.8 % for the determination of commercial products with the recovery of 95 % ∼ 108 %. Besides peroxidase, the proposed method has a good selectivity for common biomolecules, and the relative standard deviation was less than 4.76 % for the repeated determinations.