Immunosensor for prostate-specific antigen using Au/Pd@flower-like SnO2 as platform and Au@mesoporous carbon as signal amplification

In the present work, a sandwich-type electrochemical immunosensor for ultrasensitive determination of prostate-specific antigen (PSA) was designed by using Au/Pd@SnO2 as sensing platform and gold@mesoporous carbon nanocomposites (Au@CMK-3) as signal amplification. In this work, Au@CMK-3 was prepared for immobilizing large amounts of redox probe-methylene blue (MB), horseradish peroxidase (HRP), and secondary antibodies (Ab2), leading to the formation of Au@CMK-3-MB-Ab2-HRP bioconjugate. Furthermore, Au/Pd@SnO2 was utilized as the biosensor platform to immobilize the primary antibodies (Ab1) leading a further enhancement in the sensitivity of immunosensor. With the synergistic effects among the Au/Pd@SnO2 platform, the Au@CMK-3 nanocarrier, the ultrafine Pd NPs electrocatalyst, and HRP enzymatic reactions, an almost doubled amplified detection signal was achieved in the presence of H2O2, so as to improve the detection limit of the proposed immunosensor effectively. The constructed immunosensor exhibited desirable performance for determination of PSA with a wide linearity in the range from 0.01 to 100 ng mL(-1) and a relatively low detection limit of 3 pg mL(-1). The proposed immunosensor was also used to determine PSA in human serum with satisfactory results, implying potential applications in immunoassays.