A novel impedimetric immunosensor based on sol-gel derived Barium Strontium Titanate composite film

We report the development of a novel impedimetric immunosensor based on sol-gel derived Barium Strontium Titanate (BST) composite film. On a platinum electrode, a layer of rough and porous BST composite film is deposited using sol-gel technique. A gold electrode is placed in parallel to the Pt electrode with a separating distance of 1 mm. 10 μL DI water is applied between the two electrodes as contact media. On the BST grain surface, water molecules dissociate into H⁺ and OH^-, which contribute to the charge transfer between the two electrodes when an electrical field is applied. When Bovine Serum Albumin (BSA) and anti-BSA molecules are immobilized onto the BST film surface, significant impedance increment between two electrodes is observed. This impedance increment is attributed to two factors. One, the BSA and antiBSA molecules that immobilized on the BST surface prevent the water molecules from contacting the BST grains and induce less water molecules to dissociate into mobile ions. Two, the immobilized BSA and anti-BSA molecules act as obstacle barriers to the electron transfer between the solid/liquid interfaces. Comparing to the conventional electrochemical immunosensor, our present sensor is promising with higher sensitivity. Good linear relationship between impedance change and logarithm of anti-BSA concentration in a wide range is obtained.