Enzyme-catalyzed high-performing reaction with in-situ amplified photocurrent on carbon-functionalized inorganic photoanode for immunosensing.

An enzyme-catalyzed high-performing reaction with in-situ amplified photocurrent was innovatively designed for the quantitative screening of carcinoembryonic antigen (CEA) in biological fluids by coupling with carbon-functionalized inorganic photoanode. A split-type photoelectrochemical (PEC) immunoassay was initially executed with horseradish peroxidase (HRP)-labeled secondary antibody on the capture antibody-coated microtiter. Then, the photocurrent of carbon-functionalized inorganic photoanode were improved through enzymatic insoluble product. Experimental results revealed that introduction of the outer carbon layer on the inorganic photoactive materials caused the amplifying photocurrent because of the improving light harvesting and separation of photo-generated e-/h+ pairs. Under optimum conditions, the split-type photoelectrochemical immunosensing platform displayed good photocurrent responses within the dynamic range of 0.01 - 80 ng mL-1 CEA, and allowed the detection of CEA as low as a concentration of 3.6 pg mL-1 at the 3Sblank level. The strong attachment of antibodies onto nano label and high-performing photoanode resulted in a good repeatability and intermediate precision down to 9.83%. No significant differences at the 0.05 significance level were encountered in the analysis of six human serum specimens between the developed PEC immunoassay and the commercially available CEA ELISA kits.