To date, the nanolithography approach applied to inorganic crystals (semiconductors), has been very successful in the electronic industry. Even more successful, although scarcely under human control, are nanometer-scale growth bioprocesses that have reached an unparalleled level of complexity. The objective of the present project is to explore in depth this new and exciting field of science, enabling full exploitation of the properties of growth bioprocesses by the realization of opto- and microelectronic devices, including nanopatterned silica arrays, optical waveguides, and semiconductor field effect transistors, with the controlled linking of silicatein molecules to surfaces by micro- and nanopatterning.
Within the past several years, the capability of producing patterns of biological molecules with micrometer-level resolution has attracted increasing interest with respect due to their possible use in a wide number of applications. These applications include microarray technologies for genomics and proteomics, medical diagnostics, biological assays and sensors, molecular electronics, control of cellular adhesion, growth and functionality, and bacterial detection. To fabricate biomicropatterns, one can use photografting, inkjet printing, printing robots, and soft lithography. However, soft lithography is particularly suitable due to its experimental simplicity, low cost, and extreme flexibility in terms of the employable substrates, solvents, and deliverable molecules. Imprinting processes, microfluidic networks, and microcontact printing (µCP) have succeeded in achieving chemical contrast among different biomolecular monolayers. In particular, µCP, which was originally proposed to fabricate self-assembled monolayers (SAMs) of alkanethiolates onto gold, was soon applied to the synthesis of patterned proteins on surfaces.
Many uni- and multicellular organisms like diatoms and sponges, have an inorganic skeleton consisting of amorphous silica (biosilica). Siliceous sponges are unique in their ability to synthesize their silica skeleton enzymatically. The responsible enzymes, the silicateins which have been isolated from demosponges, have been described to polymerize alkoxide substrates to silica. The cDNAs and/or the genes encoding these enzymes, which belong the cathepsin subfamily of proteases, have been cloned from the marine sponges Tethia aurantium, Suberites domuncula and Petrosia ficiformis, and the freshwater sponge Lubomirskia baicalensis. The recombinant silicateins, silicatein-α and -β, are able to catalyze biosilica synthesis using tetraethoxysilane (TEOS) as substrate.
Other members of the cathepsin subfamily of proteases including human cathepsins do not precipate silica. In the sponge silicatein sequence, the cysteine residue of the catalytic triad of these cysteine proteases (consisting of the three amino acids Cys, His and Asn) is replaced by serine which is thought to be essential for the catalytic mechanism of the enzyme. In addition, a hydroxy amino acid (serine) cluster is present in the T. aurantium and S. domuncula molecules.
In this project, nature is used as a model for the structure-directed synthesis of amorphous silica (biosilica). Usually the synthesis of glass-like silica structures requires high temperature or high pressure processes limiting the possibility to built up functional biomolecule-silica composite structures. The new enzymes (silicateins patented by the consortium) will allow the controlled formation of silica patterns on surfaces and the construction of specifically designed nanostructures.