Single-step homogeneous photoelectrochemical aptasensing driven by NIR-excited Yb-Bi2S3/PMA arrays for ultrasensitive detection of tumor markers.

The accurate detection of tumor markers necessitates analytical platforms that balance operational simplicity with high sensitivity. Conventional photoelectrochemical (PEC) biosensors often face limitations due to multi-step protocols and inefficient near-infrared (NIR) light utilization, impeding their clinical translation. Herein, we report ytterbium-doped bismuth sulfide hybrids encapsulated with phosphomolybdic acid (Yb-Bi2S3/PMA) as NIR-808 nm-responsive electrode arrays. Yb3+ doping induces lattice distortion, enhancing NIR absorption and carrier separation, while PMA coating provides cascade electron transfer pathways and self-sufficient electron donors, collectively enabling efficient PEC sensing. Leveraging these attributes, we developed a homogeneous PEC (HPEC) aptasensor that requires only a single-step magnetic incubation/separation process. Target-induced steric hindrance directly modulates the photocurrent, eliminating the need for time-consuming immobilization and elution steps. This HPEC prototype achieves an ultralow detection limit of 0.35 pg mL-1 and broad linear range (0.001-80 ng mL-1) for carcinoembryonic antigen (CEA), with 96 %-108.1 % recovery in serum samples from healthy and cancer patients. Notably, the biosensor demonstrates superior reproducibility (RSD <2.5 %) and specificity (against 10-fold interferents) compared to conventional ELISA and electrochemical methods. This work not only advances NIR-driven PEC bioanalysis through function-reformed semiconductors, but also pioneers a homogeneous sensing paradigm for rapid, point-of-care cancer diagnostics.