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.