Regrowing bone requires a scaffold that is stiff, long-lasting and safe. With that in mind, David Kaplan of Tufts University and his colleagues decided to marry the protein that constitutes the drag lines of golden silk orb weaver spiders with the protein that helps diatoms--a subset of plankton--make silica, a glasslike compound. The spider-silk protein alone "just doesn't have the stiffness you want, that's why you need the glass," Kaplan says.
After splicing the two proteins together, the team then processed the resulting chimeric protein into both films and fibers and tested the result. As hoped, the films and fibers created dense silica coatings for themselves. By using electric current or varying conditions, the researchers could also control the size and shape of the resulting materials. "We were able to control and bring it down to two microns [wide]," adds team member Cheryl Wong Po Foo of Tufts. "We're going into the nanoscale range."
Initial tests of the nanomaterial's medical potential is being conducted in vitro, but the researchers hope to try it out in animals in the near future, using it to help guide the growth of a hip replacement, for example. The possibilities do not end there, however. The chimeric protein forms this material at low temperatures and without chemicals other than water. Current industrial practices for making silica require high heat and ionic extremes. "You can think of high performance materials made via an aqueous, room temperature, green chemistry," Kaplan notes. The research is being published online this week by the Proceedings of the National Academy of Sciences.