Bifunctional polydopamine thin film coated zinc oxide nanorods for label-free photoelectrochemical immunoassay

In this work, a novel yet simple PEC immunosensor based on bio-inspired polydopamine (PDA) thin film-coated ZnO nanorods was reported. In this photoelectrochemical immunosensor, the PDA thin film serves simultaneously as a unique sensitizer for charge separation as well as a functional layer for probe antibody attachment. The photocurrent on this electrode under illumination decreases upon the immunoreaction on the surface, possibly due to the blocking effect of formed immunocomplexes on the access of reducing reagent to the photoelectrode, thus offering a simple and reliable platform for PEC label-free immunoassay. By using an antibody-antigen pair as a model, successful label-free immunoassay was achieved with a detection limit of 10 pg mL−1 and a dynamic range from 100 pg mL−1 to 500 ng mL−1. This work demonstrates intriguing electro-optical property and bioconjugation activity of PDA film and may pave the way toward advanced PEC immunoassays.118