Biological Transformation of AgI on MOF-on-MOF-Derived Heterostructures: Toward Polarity-Switchable Photoelectrochemical Biosensors for Neuron-Specific Enolase

The sensitive detection of neuron-specific enolase (NSE) as a biomarker for lung cancer at an early stage is critical but has long been a challenge. The emergence of polarity-switchable photoelectrochemical (PEC) bioanalysis has opened up new avenues for developing highly sensitive NSE sensors. In this study, we present such a biosensor depending on the bioinduced AgI transition on MOF-on-MOF-derived semiconductor heterojunctions. Specifically, treatment of ZnO@In₂O₃@AgI by bioproduced H₂S can in situ generate the ZnO@In₂O₃@In₂S₃@Ag₂S heterojunction, with the photocurrent switching from the cathodic to anodic one due to the changes in the carrier transfer pathway. Linking an NSE-targeted sandwich immunorecognition with labeled alkaline phosphatase (ALP) catalyzed generation of H₂S, such a phenomenon was correlated to NSE concentration with good performance in terms of selectivity and sensitivity and a low detection limit of 0.58 pg/mL. This study offered a new perspective on the use of MOF-on-MOF-derived heterostructures for advanced polarity-switchable PEC bioanalysis.