Acetylcholine esterase antibodies on BiOI nanoflakes/TiO2 nanoparticles electrode: a case of application for general photoelectrochemical enzymatic analysis.

To date, almost all the established photoelectrochemical (PEC) enzymatic biosensors require the surface-confinement procedure to immobilize enzyme as biorecogniton element for probing various analytes of interest. This Letter develops a novel example without such necessity. Specifically, we first prepared a BiOI nanoflakes (NFs)/TiO2 nanoparticles (NPs) p-n heterojunction as the photoelectrode, on the basis of which acetylcholine esterase (AChE) antibody was introduced via the bridging of protein A. In such a system, enzyme could keep its optimal state in the solution if in the absence of inhibitor; otherwise, the degree of enzyme inhibition would correlate closely with the concentration of inhibitor. After immunoreaction between AChE and its antibody, the inhibitor concentration could then be determined by the biocatalytic reaction-controlled PEC response. Integrated with other enzyme-based biosystems, this simple configuration could serve as a general method for assaying enzyme inhibition or activities.