A wide variety of different biomate

A wide variety of different biomaterials are currently employed in medical applications throughout the world.Research towards the development of new biomaterials has traditionally focused on the preparation of functional materi- als capable of the simple adhesion of cells or the connection of tissues to metals and ceramics. However, there is a growing interest in the development of biomaterials involving the immobilization of growth factors, which would allow these artificial materials to regulate specific cellular functions, including the gene expression processes associated with cell growth and differentiation.[1] Although numerous studies have been reported pertaining to the use of metallic materials in medical devices such as artificial joints, dental implants andstents, there have been very few reports concerning the surface modification of metal or ceramic materials with biological agents.[2] A biomimetic approach inspired by mussel adhesive activity has recently been developed as a strategy for the surface modification of metals and ceramics with biological materials. Considering that the underwater adhesive protein secreted by mussels contains 3,4-dihydrox- yphenethylamine (DOPA) in its active site,[3] it is possible to incorporate proteins containing DOPA or one of its more simplified derivatives dopamine as a strategy for the surface modification of metals and ceramics.[4] Although numerous DOPA-containing peptides and macromolecules have been reported,[5] the site-specific incorporation of DOPA into proteins, such as growth factors, of which tertiary structure are important for the signal transduction activity, have not been reported. It is important to incorporate DOPA without disturbing the tertiary structure and active site of proteins. If such a protein is prepared, it should play a much greater regulatory role in cells, including gene expression for cellular growth and differentiation by binding on various materials. However, because DOPA is a non-canonical amino acid, it cannot be directly incorporated into a protein using conven- tional protein-engineering (recombinant DNA) techniques.