Folate receptors detection based on the immobilization of folic acid onto Ti−W oxides thin film

The overexpression of folate receptors on cell surfaces is associated with abnormalities linked to epithelial cancers. This study reports on a capacitive biosensor that employs folic acid as a recognition molecule for the biosensing of folate receptors. The biosensor is composed of a thin film of Ti–W oxides conjugated with folic acid that serves as a working electrode in a three-electrode electrochemical cell configuration. The thin film of Ti–W oxides, featuring a mixture of TiO₂ anatase and rutile phases, was fabricated using the pulsed laser deposition method and subsequently functionalized with folic acid. Characterization of the thin film before and after functionalization was conducted using AFM, XPS, and contact angle measurements. The functionalization study confirmed a stable bond between folic acid and the surface of the thin film. The interaction between the functionalized transducer and the folate receptor was investigated by determining the electrochemical capacitance using an electrochemical capacitance spectroscopy setup. Folate receptor recognition assays demonstrated that the biosensor response signal, or chemical hardness (in terms of electrochemical capacitance), is selective and directly proportional to the folate receptor concentration, with a limit of detection of 200 pM (0.2 nM). These findings are promising for the application of this detector in the recognition of folate receptors, particularly for point-of-care analysis.