Ultrasensitive okadaic acid detection via DNA hydrogel-gated organic photoelectrochemical transistor biosensing platform.

The burgeoning organic photoelectrochemical transistor (OPECT) biosensor has ascended as a promising technology for the detection and analysis of biomolecules. In this endeavor, a novel DNA hydrogel ultramicro-change gated OPECT aptasensor was innovatively conceived. Specifically, SnO/CdS QDs photosensitive material was introduced onto the working electrode, which served for interface and light modulation and exhibited a high current gain. Unlike conventional biomolecular interfaces, a targeted DNA hydrogel layer was established at the interface through the actions of a catalyst and initiator. This DNA hydrogel obstructed the interfacial mass transfer between the gate interface and electrolyte solution, while simultaneously impeding the light absorption of SnO/CdS QDs, consequently diminishing the photocurrent and altering the response of OPECT device. Upon the introduction of target okadaic acid (OA), the DNA hydrogel experienced partial opening and collapse, resulting in an enhanced effective contact at the gate/electrolyte interface. The photoelectric response was highly elevated by the minute alterations of the target-responsive DNA hydrogel. This process significantly diminished the recombination efficiency of interface carriers, thereby enabling effective modulation of the organic semiconductor poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS), which can provide robust support for target recognition. In the absence of gate bias, the proposed OPECT biosensor demonstrated a remarkable sensitivity and commendable analytical capability for OA, achieving a detection limit of 7.5 pM. Given its potential application in detecting harmful algal toxins across various marine environments, it is anticipated to evolve into an exceptional quantitative approach for marine toxins.