An anti-fouling photoelectrochemical-electrochemical sensing platform with a zwitterionic interface and a photocurrent-polarity-switching strategy.

In this work, we have developed a photoelectrochemical-electrochemical (PEC-EC) dual-mode sensing platform consisting of a polydopamine (PDA)-poly(sulfobetaine methacrylate) (PSBMA) anti-fouling zwitterionic interface equipped with a photocurrent-polarity-switching strategy. The PSBMA-PDA copolymer anti-fouling layer was attached to a hydrogen bonded organic framework-101 (HOF-101)-Sb2S3 modified indium titanium oxide (ITO) electrode surface using a dopamine mediated coupling reaction. The attachment of the aptamer of the model analyte prostate specific antigen (PSA) was designed to trigger a hybridisation chain reaction that linked the bifunctional factor of thionine-modified hairpin H1 and hairpin H2 to the anti-fouling electrode surface. Thionine then induced a switch from a cathodic to an anodic photocurrent at the PSBMA-PDA-HOF-101-Sb2S3/ITO, while generating a large differential pulse voltammetric current. This PSBMA-PDA interface-based anti-fouling thus acts as a dual-mode sensing platform that not only offers good anti-fouling capability by reducing non-specific adsorption, but also sensitively detects PSA over a 10 fg mL-1 - 100 ng mL-1 linear range and a detection limit of 5.0 fg mL-1 PSA in the PEC mode, and a 50 fg mL-1 - 100 ng mL-1 linear range and a detection limit of 24.6 fg mL-1 in the EC mode. This anti-fouling PEC-EC dual-mode sensing platform is readily applicable to the highly sensitive and selective detection of various disease biomarkers by simply attaching the corresponding DNA aptamer, thereby offering a promising pathway for early clinical diagnosis and point-of-care testing.