Immunosensor Enhanced with Silver Nanocrystals for On-Chip Prostate Specific Antigen Detection

An electrochemical immunosensor for the quantification of prostate specific antigens (PSA) using silver nanocrystals (AgNCs) is reported. The silver nanocrystals were synthesized using a conventional citrate reduction protocol. The silver nanocrystals were characterized using scanning electron microscopy (SEM) and field effect scanning electron microscopy (FESEM), x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, and small angle X-ray scattering (SAXS). The proposed immunosensor was fabricated on a glassy carbon electrode (GCE) sequentially by drop-coating AgNCs, the electro-deposition of EDC-NHS, the immobilization of anti-PSA antibody (Ab), and dropping of bovine serum albumin (BSA) to prevent non-specific binding sites. Each stage of the fabrication process was characterized by cyclic voltammetry (CV). Using square wave voltammetry (SWV), the proposed immunosensor displayed high sensitivity in detecting PSA over a concentration range of 1 to 10 ng/mL with a detection limit of 1.14 ng/mL and R2 of 0.99%. The immunosensor was selective in the presence of interfering substances like glucose, urea, L-cysteine, and alpha-methylacyl-CoA racemases (AMACR) and it showed good stability and repeatability. These results compare favourably with some previously reported results on similar or related technologies for PSA detection.