Scientists in the US have combined spider silk with biological silica to make an extremely strong composite nanomaterial that could be used in industrial and medical applications. The new nanomaterial, which has been made by David Kaplan at Tufts University in Massachusetts and colleagues, boasts the flexibility and tensile strength of silk and the toughness of silica (Proc. Natl. Acad. Sci. in press).
Silica is widely found in biological systems, where it supports and protects single-celled organisms, such as algae (diatoms). It also exists in the skeletons of some higher animals and even in plants. Spider silk, meanwhile, is a highly flexible material that has a high tensile strength. Moreover, it can self assemble to produce well-defined sheet-like structures.
In their new work, Kaplan and colleagues used genetic engineering to make a cloned spider silk protein that can form films and fibres. By mixing this material with biosilica — from the proteins of diatoms — in aqueous solution, the researchers were able to create a new composite nanomaterial with exceptional mechanical properties. The researchers found that the eliptically shaped silica particles attached themselves to the protein fibres, which as a result became “sticky”.
The silica particles were also found to form in a narrow range of sizes of between just 0.5 and 2 microns in diameter, unlike their natural counterparts, which vary over a broader range from 0.5 to 10 microns. According to Kaplan and co-workers, this ability to control the silica particle size could be used in industrial and biomedical applications, and to make new composites. An example is novel biomaterials for making artificial bone.
The researchers say that their technique might allow the production of other tough materials and composites that are difficult to fabricate using traditional industrial methods. The team will now try to better control the silica morphology to further improve its mechanical properties.
