Recombinant Spider Silk Forms Tough and Elastic Nanomembranes that are Protein-Permeable and Support Cell Attachment and Growth

Biologically compatible membranes are of high interest for several biological and medical applications. Tissue engineering, for example, would greatly benefit from ultrathin, yet easy-to-handle, biodegradable membranes that are permeable to proteins and support cell growth. In this work, nanomembranes are formed by self-assembly of a recombinant spider silk protein into a nanofibrillar network at the interface of a standing aqueous solution. The membranes are cm-sized, free-standing, bioactive and as thin as 250 nm. Despite their nanoscale thickness, the membranes feature an ultimate engineering strain of over 220% and a toughness of 5.2 MPa. Moreover, they are permeable to human blood plasma proteins and promote cell adherence and proliferation. Human keratinocytes seeded on either side of the membrane form a confluent monolayer within three days. The significance of these results lays in the unique combination of nanoscale thickness, elasticity, toughness, biodegradability, protein permeability and support for cell growth, as this may enable new applications in tissue engineering including bi-layered in vitro tissue models and support for clinical transplantation of coherent cell layers.