A non-labeled DNA biosensor based on light addressable potentiometric sensor modified with TiO₂ thin film

Titanium dioxide (TiO₂) thin film was deposited on the surface of the light addressable potentiometric sensor (LAPS) to modify the sensor surface for the non-labeled detection of DNA molecules. To evaluate the effect of ultraviolet (UV) treatment on the silanization level of TiO₂ thin film by 3-aminopropyltriethoxysilane (APTS), fluorescein isothiocyanate (FITC) was used to label the amine group on the end of APTS immobilized onto the TiO₂ thin film. We found that, with UV irradiation, the silanization level of the irradiated area of the TiO₂ film was improved compared with the non-irradiated area under well-controlled conditions. This result indicates that TiO₂ can act as a coating material on the biosensor surface to improve the effect and efficiency of the covalent immobilization of biomolecules on the sensor surface. The artificially synthesized probe DNA molecules were covalently linked onto the surface of TiO₂ film. The hybridization of probe DNA and target DNA was monitored by the recording of I-V curves that shift along the voltage axis during the process of reaction. A significant LAPS signal can be detected at 10 μmol/L of target DNA sample.