Ni(OH)2/NGQDs-based electrochemiluminescence immunosensor for prostate specific antigen detection by coupling resonance energy transfer with Fe3O4@MnO2 composites.

An efficient quenching electrochemiluminescence (ECL) immunosensor based on ECL resonance energy transfer (ECL-RET) was studied for sensitive analysis of prostate specific antigen (PSA). In this protocol, nitrogen-doped graphene quantum dots (NGQDs) which could produce excellent ECL emission, were loaded onto Ni(OH)2 with the three-dimensional (3D) hierarchical and stacked lamellar structure. Taking advantages of high conductivity and large specific surface area of Ni(OH)2, the better electrochemical and ECL behavior of Ni(OH)2/NGQDs were presented. As another part of immunosensor, the Fe3O4@MnO2 composites with wider ultraviolet absorption range were successfully assembled. The absorption spectra of Fe3O4@MnO2 precisely overlapped with the ECL spectra of NGQDs, leading to the significant decrement of ECL signal. Herein, the sandwich-type immunosensor was developed based on the quenching mechanism between NGQDs (ECL donor) and Fe3O4@MnO2 (ECL acceptor). The system was optimized to realize reliable determination of PSA concentration within the linear range of 10-5-10ng/mL and a detection limit of 5 fg/mL (S/N = 3). Eminently, the developed method was successfully applied in real serum samples with good recoveries in a range from 94.0% to 102%, indicating the good accuracy of the proposed method for PSA detection.