Silica is widely found in biological systems, where it supports and protects single-celled organisms, such as 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. What's more, it can self assemble to produce well-defined sheet-like structures.

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 composite nanomaterial with exceptional mechanical properties. The researchers found that the elliptically 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. In contrast their natural counterparts 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 control the silica morphology better in order to improve its mechanical properties further.