A TiO2 mesocrystals triggered signal amplification strategy of photoelectrochemical immunoassay for α-fetoprotein detection based on indirect competitive reaction

A versatile TiO 2 mesocrystals trigged signal amplification photoelectrochemical (PEC) sensing platform was designed for sensitive and accurate determination of α-fetoprotein (AFP). To construct such a biosensor, Bi 2 S 3 nanosheets with notable visible light photoactivity and biocompatibilities were employed as electron transfer mediator as well as a substrate for AFP antigen immobilization. Meanwhile, the Polyethylenimine (PEI) functionalized TiO 2 mesocrystals was used to anchor AFP antibody and the resulting composite Ab-TiO 2 -PEI was utilized as trace tag for signal amplification. The trace tag anchored onto the electrode interface via indirect competitive recognition between free target AFP and immobilized AFP to combine Ab-TiO 2 -PEI. As a result, a cascade structure of band-edge levels formed between TiO 2 mesocrystals and Bi 2 S 3 nanosheets, which notably promoted the photo-to-current conversion efficiency and enhance photocurrent response significantly. By merit of these, the concentration of AFP could be accurately determined through an indirect competitive reaction immunoassay . Upon the optimal condition, this PEC biosensor performed favorable sensitivity, selectivity and reproducibility. Hence, the designed indirect competitive PEC immunoassay possesses a potential application for clinical test and will inspire more development of simple and practical PEC sensor toward different biomolecules.