A Reliable Photoelectrochemical Bioassay System Based on Cathodic Reaction at a Solid–Liquid–Air Joint Interface.

Photoelectrochemical (PEC) bioassay system based upon cathodic measurement of enzymatic product hydrogen peroxide (H2O2) is highly attractive for accurate analyte detection as it can naturally avoid interference signals arising from readily oxidizable species in biological solutions. However, its practical utilization is restricted due to the similar reduction potential of H2O2 and oxygen, whereas solution oxygen levels can fluctuate significantly. To this end, this restriction is addressed via developing a novel PEC bioassay system containing a bio‐cathode with a solid–liquid–air triphase interface constructed by assembling an oxidase layer on the surface of superhydrophobic single‐crystal TiO2 nanowire arrays. The triphase bio‐cathode enables oxygen rapidly diffusing from the air phase to the bioassay reaction zone, thereby providing a constant interfacial oxygen concentration. The cathodic measurement enables PEC bioassay system exhibiting remarkably high detection selectivity, and compared with a normal diphase solid–liquid PEC bioassay system a 100‐fold extended linear detection range. The rapid electron transport in the single‐crystal TiO2 nanowire arrays endows the bioassay system an 845‐fold enhanced sensitivity, and three orders of magnitude lower minimum detection limit compared with TiO2 nanoparticle–based ones. The detection principle is general and thus applicable for quantification of other bio‐species. A high performance PEC bioassay system based on cathodic reaction at a bio‐cathode possessing a solid–liquid–air triphase joint interface is designed and constructed by assembling an oxidase layer on a superhydrophobic single‐crystal TiO2 nanowire arrays. The triphase PEC bioassay simultaneously exhibits high detection selectivity, wide linear detection up limit, high sensitivity, and low minimum detection limit. [ABSTRACT FROM AUTHOR]