Biomimetic sandwich assay of proteins with a photoelectrochemical sensor using molecularly imprinted targeting and self-ratiometric signaling

A novel photoelectrochemical (PEC) sensor based on dual-molecularly imprinted polymer (MIP) and self-ratiometric strategy was developed for measuring disease marker. The human papillomavirus 16 (HPV16) L1 protein was selected as a target model. The sensing elements contain TiO2 @Au as the PEC material, the MIP film as the primary artificial recognizer, and the alkaline phosphatase-labelled MIP nanoparticles (ALP-nanoMIPs) as the secondary artificial recognizer. Both MIPs were fabricated with a tailored and controllable process using merely a tiny epitope of the target protein as the templates. With the addition of L1 protein, a sandwich structure was formed and based on the dual-MIPs recognition. Ascorbic acid as the electron donor was produced and promoted the transient photocurrent response. Meanwhile, the steady photocurrent response decreased, arising from hinderance effect of the target protein rebinding for MIP film. This MIP sensor exhibited superior limit of detection (∼0.1 pg mL−1) and a broad linear range (0.28 pg mL−1 to 28 ng mL−1) for L1 protein. Good performance in terms of robustness, stability, selectivity, and repeatability was also confirmed. The designed MIP sensor has significant potential in extensive fields of low-cost antigen marker tests and healthcare screening.