A silver dagger in a silken sheath: A new hybrid biomaterial

(Nanowerk News) Hybrid materials are already a feature of our bodies. Our bones are built by the deposition of calcium containing salts onto organic templates. This combination of an organic and inorganic phase gives bone its strength and toughness. But Nature has limited itself to the use of only a few inorganic ions, such as calcium and iron. Now, genetic engineering gives us the chance to suggest new hybrid materials to Nature.
David Kaplan and his team at Tufts University have done just that, using genetic engineering techniques to produce a new material that combines the biocompatibility and toughness of silk with the anti-bacterial properties of silver ("Genetically Engineered Chimeric Silk–Silver Binding Proteins").
Using cloning techniques, they engineered a vector, which is a molecule of naked DNA that can be replicated within bacterial cells and used to express desired genes. They incorporated the nucleotide sequence that codes for a spider silk protein along with a sequence that codes for a silver-binding peptide. E. coli. cells were then used to express the chimeric protein.
The resulting material has the ability to nucleate silver ions from a silver nitrate solution, forming silver nanostructures, but could also be processed into films, fibres, and scaffolds due to the natural stability of the silk. The team found that the silk–silver protein films inhibit microbial growth of both Gram-positive and Gram-negative bacteria, highlighting the potential of the material in biomedical applications.
Source: By Hilary Gallagher, Wiley