Facile fabrication of uniform silica films with tunable physical properties using silicatein protein from sponges.

We report an elegant and simple method to fabricate uniform silica films with controlled thickness, roughness, and hydrophilicity using nanogram quantities of silicatein, a protein involved in silica synthesis in sponges. The formation of uniform silica films was achieved by immobilization of silicatein on gold-coated surfaces that had been functionalized with amines. Specifically, the amines, cystamine and cysteamine having disulfide and thiol groups, respectively, were bound to surfaces and treated with a cross-linking agent, glutardialdehyde (GDA) before protein immobilization. Silica was formed on the silicatein bound surfaces under environmentally benign conditions using tetramethoxysilane (TMOS). The thickness (20-100 nm), roughness (1.2-5.2 nm), and water contact angle (48 degrees-16 degrees) of the silica films could be controlled by varying the amount of silicatein adsorbed (10-30 ng/cm(2)) and time of exposure of protein-coated surfaces (30-120 min) to silica precursors. The silicatein protein retained around 90% of its intrinsic activity when attached to the functionalized surfaces with similar activity being observed for silica films formed from TMOS or tetraethoxysilane (TEOS). This simple route to prepare silica films of controlled physical properties could have potential application in membrane fabrication, biomedical devices, biosensors, and next generation electronic components.