Integrated Biosensing Platform Based on Bi ₂ S ₃ /BiFeO ₃ Heterojunction and BiVO ₄ for Ultrasensitive Organic Photoelectrochemical Transistor and Colorimetric Dual-Mode Detection of Prostate-Specific Antig

Among recently emerged bismuth-based nanomaterials, Bi₂S₃/BiFeO₃ heterojunctions are promising candidates for improving biomarker detection by enhancing charge separation. Benefitting from this, we have developed a dual-mode system by taking advantage of the photoelectric properties of Bi₂S₃/BiFeO₃ and the peroxidase-like activity of BiVO₄, which integrates independent signal transduction for cross-validation and, thus, significantly enhanced the credibility of detection. The target prostate-specific antigen (PSA) was captured through an Ab₁-PSA-Ab₂ sandwich structure, and Ab₂ was modified with BiVO₄-alkaline phosphatase (ALP). In organic photoelectrochemical transistor (OPECT) mode, ALP reduces ascorbic acid 2-phosphate (AAP) to ascorbic acid and etches the electroplated MnO₂ film to restore the signal. BiVO₄ oxidizes 3,3,5,5-tetramethylbenzidin in H₂O₂ by virtue of its inherent peroxidase-like activity for the colorimetric signal. A linear response was received between signal response and PSA in which concentration ranged from 10 fg mL^-1 to 50 ng mL^-1 in OPECT mode and from 0.1 to 100 ng mL^-1 in colorimetric mode. The enhanced charge separation from the ferroelectric polarization of BiFeO₃ and the improved electrical conductivity from Bi₂S₃ explored the applications of bismuth-based nanomaterials in reliable high-performance bioanalysis.