Three-dimensional donor-acceptor-type photoactive material/conducting polyaniline hydrogel complex for sensitive photocathodic enzymatic bioanalysis.

Herein, an innovative photocathodic enzymatic biosensor is proposed with poly {4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]-benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl} (PTB7-Th) as donor-acceptor-type photoactive material and three-dimensional (3D) polyaniline hydrogels (PAniHs) as both electron transfer layer and biomolecule carrier. Based on the enhancement effect of PAniHs on the charge separation and electron transfer of PTB7-Th and the competitive consumption of dissolved oxygen (O2) between the xanthine oxidase (XOD)-guanine catalytic reaction and O2-sensitive PTB7-Th/PAniHs, the proposed photocathodic enzymatic biosensor has been demonstrated to detect guanine with the advantages of low limit of detection (0.02 μM), wide linear range (from 0.1 to 80 μM), simple and convenient preparation process, satisfactory stability, and photochemical signal amplification independent of any exogenous electron donor/acceptor or sensitizer. Remarkably, the proposed photocathodic enzymatic biosensor can not only be extended to other aerobic enzymatic bioanalyses, but also pave a horizon for the application of environmentally friendly conductive hydrogel materials in photoelectrochemical bioanalysis.