Ru(phen)₃²⁺-Sensitized GaN-Gated Organic Photoelectrochemical Transistor for Sensitive and Selective Detection of Human Papillomavirus DNA

Benefiting from the well-matched energy levels between Ru(phen)₃²⁺ and GaN, and the ability of Ru(phen)₃²⁺ to intercalate into the grooves of double-stranded DNA (dsDNA), an innovative organic photoelectrochemical transistor (OPECT)-based biosensor has been developed for the detection of human papillomavirus 16 (HPV-16), which was chosen as a model target. Trigger DNA immobilized on the gold-coated GaN surface can initiate a hybridization chain reaction (HCR), generating long-stranded dsDNA, which can be used to load a large amount of Ru(phen)₃²⁺. The produced dsDNA can also serve as a π-π-stacked hole-transporting nanowire, enhancing the efficiency of the hole transport between GaN and Ru(phen)₃²⁺. Under light irradiation, efficient energy level matching between GaN and Ru(phen)₃²⁺ promotes the transport efficiency of photogenerated carriers, leading to a significant increase in the drain-source current (<i>I</i>_DS). In the presence of HPV-16, the CRISPR/Cas12a system is activated and the immobilized trigger DNA is cleaved, thereby preventing the formation of dsDNA through HCR. As a result, a smaller amount of Ru(phen)₃²⁺ is immobilized on the electrode surface, leading to a reduction in the output signal. The signal change exhibits a linear relationship with the target concentration in the range of 10.00 fM to 10.00 nM, achieving a detection limit as low as 2.88 fM, which is much better than that of the corresponding photoelectrochemical (PEC) biosensor. The system demonstrates excellent sensitivity and specificity in clinical sample analysis.