Will Biomimetics Provide New Answers for Old Problems of Calcified Tissues

In the past few years biomimetics has come to calcified tissues. Biomimetics, a science based on biological recognition, is based on the idea that biological systems store and process information at the molecular level. It involves the development or fabrication of synthetic systems using information obtained from biological ones. Historically, biomimetics arose from the perception that patterned arrangements in bones, teeth, and shells, as well as fibrous proteins such as connective tissue collagens and spider webs, could be storehouses of information. Even before the term biomimetics developed, biomimetic techniques were applied to the development of artificial enzymes [1]. More recently, these techniques have been used to develop new materials [2] including liquid crystals [3], ceramic thin films [4–6], computer switches [7], and other so-called smart materials [8, 9]. In the area of calcified tissues there has been a proliferation of new ‘‘biomimetic’’ bone and dental implant materials [10–12] which incorporate synthetic polymers and peptides with naturally derived growth factors and cells. These materials seek to emulate the biological processes involved in formation of bone, dentin, enamel, and other mineralized tissues to serve as synthetic substitutes for their repair. Ideally they would have structures mimicking the porosity and orientation of the tissue into which they are implanted. The search for an ideal repair material is a long-standing one. Throughout history calcium salts, metals, and other inert materials have been used to fill bone and tooth defects. With the advancing understanding of cell biology, the new goal has become the development of materials providing a synthetic matrix which, when exposed to cells or implanted in vivo, create the same response as naturally occurring bone matrices. Synthesis of light-weight mineralized matrices with the mechanical strength of mineralized tissues may also eventually be useful in other fields. To date, none of the ‘‘bone biomimetics’’ has achieved this goal. This editorial suggests that important insights into the development of such materials can come from in vitro studies of biomineralization. Further, it is suggested that in the process of developing these new materials, many unanswered questions about mineralized tissue field may be answered. It is the unanswered questions about the critical events controlling the formation of organized mineralized matrices that pose the challenge in developing calcified tissue mimetics. Such questions include: Which extracellular matrix components direct the ordered deposition of matrix and mineral, which control the pattern formation, which govern modeling or maturation, and which structural features of these components are essential for these processes? The development of synthetic means of encouraging the formation of calcified tissues and the possibility of using these techniques to fabricate biological and nonbiological materials requires answers to these questions, many of which must be found in or derived from chemical and biological studies of biomineralization.