In situ generation of electron acceptor to amplify the photoelectrochemical signal from poly(dopamine)-sensitized TiO2 signal crystal for immunoassay

Abstract

A versatile photoelectrochemical immunoassay protocol was designed for quantitative monitoring of tumor markers by utilizing the poly(dopamine)-sensitized titanium dioxide (TiO₂) signal crystal with an ordered mesoporous carbon support. Poly(dopamine) was introduced to alter the optical properties of the TiO₂ signal crystal, thereby improving the visible light absorption and photoelectrical responses. More importantly, a new enzyme-like biomimetic catalyst was exploited as the signal amplifier to catalyze the reaction of hydroquinone. The generated product was deposited on the electrode surface and served as an efficient sacrificial electron acceptor, which could receive the photo-generated electrons of the excited semiconductor to assist the cathode photocurrent enhancement. Herein, a competitive-type immunosensor was achieved through the biomimetic catalyst labeled prostate specific antigen competing with the target antigen of different concentrations to react with the specific antibody anchored on the poly(dopamine)-sensitized TiO₂ signal crystal. Under optimal conditions, the photocurrent decreased with increasing target concentration in a dynamic working range from 1 × 10⁻⁶ ng mL⁻¹ to 50 ng mL⁻¹, which provided a new photoelectrochemical method for tumor markers analysis.