A Reliable Photoelectrochemical Bioassay System Based on Cathodic Reaction at a Solid–Liquid–Air Joint Interface
Dandan Wang1, Liping Chen1, Jie Liu, Fengying Guan1, Ruize Sun2, Lei Jiang2,and Xinjian Feng1,*（封心建）
1 College of Chemistry,Chemical Engineering and Materials Science,Soochow University,Suzhou 215123, P. R. China
2 Beijing Advanced Innovation Center for Biomedical Engineering,School of Chemistry and Environment Beihang University,Beijing 100191, P. R. China
Adv. Funct. Mater. 2018, 1804410
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 biocathode 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.