Sensitive enzymatic glucose detection by TiO2 nanowire photoelectrochemical biosensors

Abstract

Photoelectrochemical detection represents a unique signal transducing modality, where the photogenerated charge carriers are modulated by the redox reactions of molecular targets over the electrode surface. In this work, we report a novel glucose sensor based on hydrothermally-grown, single-crystalline TiO₂ nanowires with surface-functionalized glucose oxidase (GOx), which can oxidize glucose to gluconic acid. The key feature of this glucose sensor design is that the photogenerated holes over the TiO₂ anode are utilized to form O₂, which directly serves as an efficient electron shuttling mediator between the enzymatic redox center of GOx and the sensor surface, thus leading to an increase of the photocurrent. As a proof-of-concept, the GOx-functionalized TiO₂ (TiO₂–GOx) nanowires exhibit a high sensitivity of ∼0.9 nM in the detection of glucose in buffer. The capability of detecting glucose in mouse serum is also demonstrated. Our work suggests the potential of developing these nanowire-based photoelectrochemical biosensors for convenient, efficient and low-cost biomarker detection and disease diagnosis.