Pencil-drawn paper-based portable photoelectrochemical immunoassay of carbohydrate antigen 19-9 based on TiO2 hollow cube homogeneous junctions

Background The design of a fully paper-based photoelectrochemical sensing platform holds significant potential for comprehensive community cancer screening. Results A portable photoelectrochemical (PEC) immunoassay was constructed based on TiO 2 hollow cube (HTCs) homojunctions with efficient photoelectric conversion properties and a paper-based printed three-electrode system. The sensor leveraged the specific immune recognition of carbohydrate antigen 19-9 (CA19-9) to mediate horseradish peroxidase (HRP)-catalyzed conversion of 4-chloronaphthol (4-CN) into insoluble, low-conductivity 4-chloronaphthol dimer (4-CD), inducing characteristic photocurrent attenuation. Under flashlight excitation, signals were recorded using a portable nanoampere meter. The sensor exhibited a wide linear range of 0.001–50 U mL −1 for CA19-9 and an ultra-low detection limit of 0.37 mU mL −1 . Furthermore, recovery tests on clinical serum samples from potential cancer patients confirmed good accuracy, and t -test results showed no significant difference between the PEC method and clinical ELISA kits, accompanied by excellent anti-interference performance. Significance This study provides a highly sensitive and portable detection platform for CA19-9, laying a foundation for its point-of-care and home-based early screening.