Double-Enhancement Strategy: A Practical Approach to a Femto-Molar Level Detection of Prostate Specific Antigen-α1-Antichymotrypsin (PSA/ACT Complex) for SPR Immunosensing

Prostate specific antigen-α1-antichymotrypsin was detected by a double-enhancement strategy involving the exploitation of both colloidal gold nanoparticles (AuNPs) and precipitation of an insoluble product formed by HRP-biocatalyzed oxidation. The AuNPs were synthesized and conjugated with horse-radish peroxidase-PSA polyclonal antibody by physisorption. Using the protein-colloid for SPR-based detection of the PSA/ACT complex showed their enhancement as being consistent with other previous studies with regard to AuNPs enhancement, while the enzyme precipitation using DAB substrate was applied for the first time and greatly amplified the signal.