Dual Amplification on Coordination-Engineered Photogate for Sensitive Organic Photoelectrochemical Transistor Biosensing.

MicroRNA (miRNA) analysis using organic photoelectrochemical transistor (OPECT) biosensors is often limited by insufficient photoelectric transduction efficiency and weak signal amplification. Herein, we develop a coordination heterojunction photogate-enabled OPECT biosensor combined with enzyme-free catalytic hairpin assembly and hybridization chain reaction (CHA-HCR) cascade amplification for ultrasensitive detection of miRNA-122. Interfacial Cu+-alkyne coordination between Cu2O and Cu-1,4-diethylenylbenzene facilitates charge transfer and photogenerated carrier separation, leading to enhanced photogating efficiency. Meanwhile, target miRNA-122 initiates sequential CHA and HCR reactions, producing extended DNA chains that accumulate at the gate/electrolyte interface and modulate the local charge environment, thereby amplifying the transistor response. The synergistic integration of coordination photogating and nucleic acid cascade amplification significantly improves analytical sensitivity (an ultralow detection limit of 0.26 fM) and selectivity toward miRNA-122. This strategy provides an effective route for constructing high-performance OPECT biosensors and broadens their applications in cancer biomarker detection.