Synergistic electrocatalysis in a Ag2S@MoS2 nanocomposite enables an ultrasensitive label-free immunosensor of prostate specific antigen.

Early detection of cancer biomarkers is crucial for improving patient survival rates. Herein, a highly sensitive label-free electrochemical immunosensor for prostate-specific antigen (PSA) was constructed based on in situ grown Ag2S nanoparticle-decorated MoS2 nanosheets (Ag2S@MoS2). The Ag2S@MoS2 nanocomposite synergistically combined the large surface area of MoS2 with the high conductivity of Ag2S, significantly amplifying the electroactive surface area and enhancing electron transfer. Upon formation of the insulating PSA-antibody immunocomplex, electron transfer was hindered, leading to a measurable current decrease. Under the optimal conditions, the sensor demonstrated a wide logarithmic linear range from 0.5 pg mL-1 to 50 ng mL-1 and an ultralow detection limit of 0.17 pg mL-1 (based on 3σ/S). More importantly, the immunosensor demonstrated high selectivity, reproducibility, and, crucially, reliable accuracy in the detection of PSA in spiked human serum samples. This work not only provided a highly sensitive tool for PSA detection but also established a versatile and powerful sensing platform based on synergistic interface engineering, with broad potential for the detection of other disease biomarkers.