Photoelectrochemical aptasensing of prostate-specific antigen using an engineered FeIn2S4/Bi2O2S heterojunction

Rational design of photoactive materials is crucial for advancing photoelectrochemical (PEC) biosensing. Herein, we report an engineered FeIn 2 S 4 /Bi 2 O 2 S heterojunction with a hierarchical flower-like morphology that affords broad visible-light absorption, efficient charge separation, and strong photocurrent response. This heterostructure serves as a robust photoelectrode for constructing an innovative PEC platform toward ultrasensitive prostate-specific antigen (PSA) detection. The platform adopts a spatially separated molecular recognition strategy, in which the sandwich-type reaction involving PSA, aptamer-functionalized magnetic spheres, and aptamer-modified Cu–MOF signal probes is conducted entirely in a centrifuge tube, physically isolated from the photoelectrode. After magnetic separation to remove unbound species, the Cu–MOF nanozyme catalyzes 3, 3′-diaminobenzidine (DAB) oxidation to produce insoluble indamine precipitates, which are subsequently transferred onto the heterojunction electrode, resulting in a significant attenuation of the PEC signal. This workflow effectively mitigates electrode fouling, reduces assay time, and enhances reproducibility, while allowing simultaneous processing of multiple samples. The resulting PEC biosensor exhibits a wide linear range from 0.05 to 500,000 pg mL −1 , an ultralow detection limit of 0.031 pg mL −1 (S/N = 3), and was applied to PSA detection in serum samples, underscoring the synergistic merits of heterojunction engineering and workflow innovation in PEC biosensing. In addition, the use of a screen-printed carbon electrode (SPCE) operated on a smartphone-controlled portable workstation enables low sample consumption and user-friendly operation, demonstrating strong potential for point-of-care testing (POCT). • A hierarchical FeIn 2 S 4 /Bi 2 O 2 S heterojunction was newly constructed, offering abundant interfaces for efficient charge transfer. • The heterostructure shows enhanced photoelectrochemical activity due to broadened light absorption and rapid carrier separation. • A spatially decoupled PEC sensing workflow separates molecular recognition from signal generation, effectively minimizing electrode fouling. • Transferable indamine deposition enables synergistic amplification, achieving an ultralow detection limit and a seven-order linear range for PSA detection. • A smartphone-operated SPCE platform enables portable, low-sample-volume, and user-friendly point-of-care diagnostics.