Bio-inspired MOF nanozyme-engineered biocatalytic precipitation strategy mediates electron transfer for ultrasensitive photoelectrochemical immunoassay

Enzyme-like nanomaterials (nanozyme) has been used to generate amplified response signals in biosensors instead of the bio-enzyme, on account of their higher stability and comparable catalytical activity. Especially the metal-organic framework (MOF) materials with ultra-high porosity and high specific surface area, which is more suitable for deriving superior nanozyme. In order to deal with the increasing demand of healthcare diagnostics and biomedical research, here we propose a novel approach for ultrasensitive photoelectrochemical (PEC) immunoassay. The bio-inspired MOF-derived nanozyme Hemin/BSA@ZIF-8 was introduced into the target biorecognition and sensing processes to accelerate the oxidization of substrate to produce insoluble precipitate, which will impede the electron transfer and lead to a significant reduction in photocurrent. The proposed PEC sensor exhibits a wide linear range of 0.1 pg mL−1 ~ 100 ng mL−1, and a low detection limit of 11.9 fg mL−1 for cardiac troponin I (cTnI) detection. This work brings a new insight of the bio-inspired MOF nanozyme-mediated PEC immunoassay designing, and offers a novel sensing strategy for accurate human biomarker analysis.