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

Photoelectrochemical (PEC) detection is a promising method for label-free immunoassay by reporting the specific biological recognition events with electrical signals. However, it is challenging to rationally incorporate immunosensing components with a photocurrent conversion interface, which generally necessitates multistep fabrication and careful tailoring of various components such as photoactive material and biological probe. For high detection reliability and reproducibility, it is highly desirable to rationally construct an efficient PEC interface with architecture as simple as possible. In this work, a novel yet simple PEC immunosensor based on bio-inspired polydopamine (PDA) thin film-coated zinc oxide (ZnO) nanorods was reported. In this PEC 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 10pgmL-1 and a dynamic range from 100pgmL-1 to 500ngmL-1. This work demonstrates intriguing electro-optical property and bioconjugation activity of PDA film and may pave the way toward advanced PEC immunoassays. Copyright Â