Bifunctional strategy based on MoS2/N,S-CQDs/Bi2S3 nanocomposite photosensitive materials: Ultrasensitive detection of prostate antigens and preliminary design of a portable detector

In this work, a novel photoelectrochemical (PEC) immunosensor based on molybdenum disulfide (MoS₂)/nitrogen and sulfur co-doped carbon quantum dots (N,S-CQDs)/bismuth sulfide (Bi₂S₃) nanocomposites was designed for the quantitative detection of prostate-specific antigen (PSA) in human serum and urine. For the initial time, we used the synthesized N,S-CQDs as a Mo⁴⁺ and Bi³⁺ sulfur source. A one-step hydrothermal process was used to create highly photoactive MoS₂/N,S-CQDs/Bi₂S₃ nanoheterojunctions. Compared to pure MoS₂ and Bi₂S₃, MoS₂/N,S-CQDs/Bi₂S₃ exhibited better photoelectric activity and electron transfer efficiency. By the layer-by-layer assembly method, the specificity between PSA and prostate-specific antibody (Anti-PSA) was used to form an immune complex, which increased the spatial site resistance of MoS₂/N,S-CQDs/Bi₂S₃, leading to a decrease in photocurrent transmission efficiency, thus reaching the purpose of direct detection of PSA concentration. Under the optimized conditions, the photoelectric signal intensity of the MoS₂/N,S-CQDs/Bi₂S₃ PEC immunosensor showed a good linear relationship with the concentration of PSA in the range of 0.001 ng/mL to 50 ng/mL, and the limit of detection (LOD) was 0.35 pg/mL. Regarding quantitative PSA detection, the developed PEC immunosensor offers outstanding selectivity, sensitivity, and stability, which can provide an effective strategy for diagnosing and treating prostate cancer. In addition, to detect PSA and other biomarkers with speed and precision, a novel portable PEC detector model was proposed and designed in this study, and the construction of this model has great potential for application in clinical and other disease diagnosis.