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

Abstract

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.