Ultrasensitive Porphyrin Organic Semiconductor-Sensitized CdS-Gated Organic Photoelectrochemical Transistor Biosensor for Rapid Detection of Tobramycin.

While organic semiconductor-sensitized inorganic semiconductors have garnered significant attention in traditional photoelectrochemical systems, their application in organic photoelectrochemical transistor (OPECT) gate electrodes remained largely unexplored. Herein, a novel grate electrode for enhancing the optoelectronic performance of the CdS photoelectrode was designed by compounding the porphyrin organic semiconductor material endocyclic tetrakis(4-carboxyphenyl) porphyrin onto the surface of CdS nanoparticles, a classical semiconductor material. The cDNA trigger of target tobramycin (TOB) was then combined with alkaline phosphatase (ALP)-labeled hairpin DNA for signal amplification by the biological strategy of hybridization chain reaction (HCR). Different concentrations of TOB were used to regulate the cDNA involved in the HCR and the concentration of ALP labeled on the hairpin DNA, resulting in different concentrations of ALP catalyzing the production of different concentrations of ascorbic acid from l-ascorbic acid-2-phosphate trisodium salt to enhance the photoelectrode photovoltaic conversion efficiency to different extents. By monitoring the corresponding channel current variations in poly(3,4-ethylenedioxythiophene):polystyrenesulfonate at specific drain voltages, a highly sensitive and specific biosensor was established for TOB detection, achieving a broad linear range (1.0 pM to 0.1 μM) with an ultralow detection limit of 25.5 pM. This work pioneers the synergistic integration of porphyrin organic semiconductor, OPECT technology, and HCR amplification for antibiotic monitoring, demonstrating the tremendous potential of organic semiconductors in advancing OPECT-based bioanalysis and providing new conceptual frameworks for developing next-generation OPECT biosensors. The successful implementation of this composite sensing strategy opens novel avenues for constructing high-performance photoelectrochemical biosensing platforms with enhanced sensitivity and specificity.