Visual detection of protein adsorption onto electrochemically oxidized aluminum surfaces

Adsorption of proteins onto electrochemically oxidized aluminum surfaces by a simple visual observation was investigated. For this purpose, Ta and then A1 were sputtered onto glass slides (Al/Ta/glass slides). Al/Ta/glass slides were electrochemically oxidized in 0.4 M H3PO4 under the potentiostatic conditions. After the application of aqueous solutions of bovine, rabbit or human immunoglobulin onto the solid Al2O3 surfaces, a change in colour was monitored visually. It was found that all investigated proteins could successfully be adsorbed onto oxidized Al surfaces. This was manifested by a change in colour of the surface from tan to a purple or blue, depending on the concentration of proteins, coating time and degree of oxidation of the Al layer. Most importantly, when an aqueous solution of human IgG was applied on an anti-human IgG coated surface, a change in colour was also observed indicating that the adsorption process did not denature the molecular recognition sites. This type of antibody-antigen reaction was confirmed on the example of anti-human prothrombin--human prothrombin. It is believed that this technology may be useful in developing immunosensors for a variety of applications.