Accumulation-Mode Organic Photoelectrochemical Transistor for Giant Panda Papillomavirus Sensing

Papillomavirus (PV), a transmissible oncogenic pathogen, has recently been identified in both healthy and diseased giant pandas, posing a critical threat to this endangered species and highlighting the need for sensitive diagnostics. Here, we present an accumulation-mode organic photoelectrochemical transistor (OPECT) immunosensor for the sensitive detection of giant panda PV. We cloned and expressed the codon-optimized E6 protein gene of giant panda PV to generate polyclonal antibodies. The sensor employs a crystalline C₄N photogate containing pyridinic nitrogen and graphitic nitrogen with a narrow bandgap (1.27 eV), broad ultraviolet-visible absorption, and high gating effect (a current gain of 10,000) for efficient charge separation and migration. This OPECT immunosensor achieves a detection limit of 40 fg mL^-1, a broad dynamic range from 0.1 pg mL^-1 to 161 ng mL^-1, and high specificity. It enables accurate analysis of giant panda clinical samples, offering a robust tool for PV surveillance in this vulnerable species.