Nanobiotechnology gets a lesson from sea sponges
Silicon is an element widely used in field effect transistors (FETs), in particular for production of insulating thin films given its low electrical and thermal conductivity. Production of these films requires silicon polymerisation, or formation of long-chain molecules containing silicon, and subsequent patterning of these polymers into glass-like silica (silicon dioxide) structures. Conventional approaches to the production of silica structures require high temperature and pressure. These conditions are detrimental to organic or biomaterial, limiting their usefulness in the new area of formation of biomolecule-silica composite structures for application to nanobiotechnology. The ‘Biomineralization for lithography and microelectronics’ (BIO-LITHO) project was designed to mimic biosilica production by marine sponges as a cost-effective and novel approach to controlled formation of silica patterns on surfaces. The nature-based methodology has enormous potential for use in design of nanostructures for use in existing biotechnologies as well as in other areas seeking inexpensive silica deposition and patterning processes. Siliceous sponges synthesise their skeletons via protein enzyme action. Their specialised enzymatic proteins (silicateins) speed up silica polymerisation. When the proteins are assembled into filaments, they provide a catalytic scaffold of sorts that speeds up and directs the patterning of silica polymers. The researchers investigated two methods to produce large amounts of silicatein in the lab, for which they were awarded a patent. They then used soft lithography techniques to control the patterned deposition of the molecules on surfaces and the production of specially designed nanostructures to be employed as insulating layers in prototype transistor devices. In summary, the BIO-LITHO project successfully demonstrated the potential for biomineralisation processes, both cost-effective and safe for the environment, to be scaled up for industrial production. These processes should prove useful in meeting the enormous demand for lithographic and microelectronic production processes in the field of nanobiotechnology.