Graphene Directs Silk Nanofiber Growth

By growing silk nanofibers on graphene, a research team has produced a flexible, strong, conductive film that could serve as a scaffold for growing cells for biomedical research and as a biosensor for diagnostic testing (ACS Macro Lett. 2014, DOI: 10.1021/mz400639y). To make the nanocomposite, Raffaele Mezzenga of ETH Zurich and his colleagues added graphene oxide sheets to a solution of silkworm proteins. The researchers also added a drop of hydrazine to reduce the graphene oxide to graphene. Stirring the black suspension for six hours at 70 °C produced silk-covered graphene sheets. The 3.5-nm silk fibers closely resemble the structure of natural spider silk rather than reconstituted silkworm silk, leading the team to believe that graphene directs self-assembly of the proteins to form fibers in a new way. The silk-graphene sheets are 100 times as conductive and about 10 times as tough as the pure graphene oxide starting material. The researchers showed that the composite readily supports growth of human cervical cancer cells, outperforming pure graphene as a cell growth medium.