Enhanced photocatalysis on graphitic carbon nitride sensitized with gold nanoparticles for photoelectrochemical immunosensors

Photoelectrochemical (PEC) sensors are promising for monitoring the environment and in clinical diagnosis, but their point-of-use application requires portable systems and materials with high photocatalytic activity. In this work, we extend the use of a recent miniaturized PEC system to detect the breast cancer biomarker carbohydrate antigen 15-3 (CA15-3) with the enhanced catalytic activity of graphitic carbon nitride (CN) decorated with gold nanoparticles (Au NPs). The performance of the immunosensor was highly dependent on the size of the nano -particles and on the film architecture. Optimized sensing of CA15-3 was reached with electrodeposited 13.1 nm Au NPs linked to a long-chain mercapto (11-mercaptoundecanoic acid), which allowed for an effective adsorption of antibodies. CA15-3 could be detected from 0.1 fg mL-1 to 10 ng mL-1, with detection limit of 0.04 fg mL-1. As a demonstration of the viability of the PEC immunosensor, the biomarker CA15-3 was detected in human serum with recovery values between 98 and 109%.