A competitive photoelectrochemical aptasensor for thrombin detection based on the use of TiO2 electrode and glucose oxidase label

A novel competitive photoelectrochemical aptasensor for thrombin (TB) detection is proposed using TiO2 electrode coupled with TB-Au nanoparticles (AuNPs)–glucose oxidase (GOx) labels. To construct the aptasensor, chitosan was coated on the TiO2 surface for the further immobilization of TB aptamer that was bridged by the use of glutaraldehyde. TB detection was then performed based upon the competitive interaction of TB and TB-AuNPs-GOx bioconjugate with TB aptamer on the electrode. GOx could catalyze the glucose to produce H2O2, which acts as an effective electron donor to deplete the photogenerated holes located at the valence band of excited TiO2, resulting in the enhanced photocurrent response. Under the optimal conditions, the as-prepared PEC aptasensor exhibits excellent analytical property for detection of TB in the range from 1.0 × 10− 12 mol L− 1 to 1.0 × 10− 8 mol L− 1 with a detection limit of 1.9 × 10− 13 mol L− 1. Moreover, the aptasensor was also successfully applied for the determination of TB in human plasma. The present strategy provides a promising method for the future development of PEC aptasensor for advanced biochemical analysis.