Immobilization of bovine serum albumin on self-assembled monolayer modified dielectric film for biosensor application

For the first time, the sol-gel derived dielectric barium strontium titanate (BST) film has been explored as a transducer material for biosensor. Self-assembled monolayer (SAM) of monododecyl phosphate (DDPO₄) has been coated on the BST film from aqueous solution of the alkyl phosphate ammonium salts, resulting in a highly hydrophobic surface with water contact angle of 99.8 deg compared to the original contact angle of 40.8 deg for the bare BST surface. The microscopic features and the biosensing properties were characterized using atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) in the presence of [Fe(CN)₆]^3-/4- as a redox couple. AFM images revealed the well immobilized BSA on the SAM modified BST surface. The EIS results showed significant increase in the electron transfer resistance compared to all other electrical elements in the equivalent circuit. Specific binding of anti-BSA on the immobilized BSA surface was observed by AFM imaging and EIS measurements. It was found that the specific binding of anti-BSA can be sensitively detected by measuring the electron transfer resistance. The present investigation indicates the potential of dielectric BST for electrochemical biosensor applications