Ultra-sensitive surface plasmon resonance based immunosensor for prostate-specific antigen using gold nanoparticle–antibody complex

Prostate-specific antigen (PSA) is a marker for prostate cancer and it has been identified as a potential marker for breast cancer in women. In order to early diagnose the prostate cancer in men and the breast cancer in women, an ultra-sensitive diagnostic tool be required. In this study, to improve the sensitivity of the immunosensor for PSA, signal enhancement of surface plasmon resonance (SPR) was done by means of the conjugation of gold (Au) nanoparticle–antibody complex. Biomolecular film on gold surface and the Au nanoparticle-conjugated antibody were fabricated. The fabrication of Au nanoparticle–protein complex was investigated through UV/vis spectroscopy. The surface structure of fabricated biosensing element was investigated by using SPR and scanning tunneling microscopy (STM). The plot of SPR angle difference versus PSA concentration shows the achievement of their linear correlation, and a limit of detection is 300 fM.