Fast and low-cost determination of prostate-specific antigen using paper-based immunodevice modified with Cu@CuS@Au NPs nanocages

In this study, the authors designed a paper-based electrochemical immunodevice modified with copper embedded in copper sulphide hollow nanocages wrapped with Au nanoparticles (Cu@CuS@Au NPs) for the specific detection of prostate-specific antigen (PSA), aiming to advance point-of-care testing. The large specific surface area of Cu@CuS nanocages enables efficient capture of biotin antibodies, leading to the direct amplification of the signal through the inhibition of electron transport in the redox process of Cu, eliminating the need for universal redox electron mediators. Additionally, Au NPs on the surface of Cu@CuS can accelerate charge transfer and conjugate with anti-PSA. The hierarchical morphology and structure of Cu@CuS nanocages were characterised using scanning electron microscopy and transmission electron microscopy. The fabrication process of the immunodevice was monitored using cyclic voltammetry and electrochemical impedance spectroscopy analyses. PSA was sensitively detected using differential pulse voltammetry on this proposed immunodevice within a linear range from 0 to 100 ng/ml (R² = 0.996), achieving a low detection limit of 0.077 ng/ml. In addition, the practicality of the developed immunosensor has been proven by successfully detecting PSA in human serum samples obtained from clinical settings. The integration of electrochemical sensors and microfluidic devices holds promise for developing cost-effective approaches in clinical immunoassays.