Aqueous electrospinning of recombinant spider silk proteins

There has been a significant increase in the use of sensitive biological components, e.g., growth factors or enzymes, in implanted scaffolds/devices. To prevent diffusion away from the targeted area and to maximize access of the biological agent to the desired target, it is necessary to provide a supportive substrate to immobilize and protect biological agents from the environment. For this purpose, nanofiber fabrics are highly promising due to their high porosity, capacity for solution flow-through and high surface-to-volume ratio. However, electrospinning often requires harsh processing conditions, such as the use of volatile solutions, which can result in loss of activity of the incorporated biological components. In this study we developed a mild process for electrospinning of eADF4(C16), a recombinant spider silk protein. eADF4(C16) is non-cytotoxic, displays excellent stability against hydrolytic and enzymatic degradation and opens the opportunity for genetic addition of bioactive factors. Therefore, an aqueous spinning dope of eADF4(C16) was loaded with either green fluorescence protein (GFP) or the recombinant fusion protein GFP-eADF4(C16). The fluorescence activity of GFP is dependent on its proper folding, which does not occur in organic solvents, making it an attractive model protein. We were able to demonstrate the usability as well as the significance of the all-aqueous processing conditions for the activity of GFP in electrospun spider silk scaffolds.