One of the limitations engineers are faced with are those of materials. This is, in part, because our material processing techniques do not allow us to control the fine detail of how materials come together. In ceramics it has long been recognized that grain size and uniformity are key elements in creating a strong and non-brittle ceramic. However, we are only just beginning to understand the degree of control over construction details that go into biological materials. Understanding these processes allows for the development of new materials and new material processing techniques. A couple of candidates for learning about these techniques are biosilicates (i.e., skeletal structures made from sand) and spider's silk. Biosilicates stand out because sand is where we often demonstrate our prowess at building minute structures with tightly specified electronic properties, yet as far as material properties go, the biosilicates have us beaten.
Biosilicate structures are built by proteins that themselves become an intricate part of the structure. Thus fine control over the structure and its resulting properties are achieved. At this point it should be remembered that all of this happens in an environment you would feel not too uncomfortable in – room temperature, pressure and not highly acidic. Thus, researchers have been fairly enamored of biosilicates, the problem is controlling the proteins themselves to build the structures that are desired. Enter common spider's silk. Spider's silk is a reasonably strong and flexible protein but has the advantage that it can self assemble into sheets of material, thus through a combination of spinning and weaving pretty much any structure is possible. The researchers modified the gene responsible for producing the silk protein so that it included a modified version of the biosilicate producing protein as well. They then produced lots of the new protein which was spun into ropes or allowed to self assemble into mats. These were then placed under conditions for which the biosilicate protein would be expected to operate. They found that the protein still operated and became coated in silica beads.
The importance of this work lies in the control and conditions under which the control is obtained. The macroscopic structure is controlled by spinning and weaving of threads, which is something we have been doing for millenia. The silica structures are controlled by choosing the frequency at which the modified protein is inserted into the thread, thus we obtain macroscopic and microscopic control. The conditions are mild, life supporting conditions so this offers potential as a material which could be used to strengthen damaged skeletal tissue.