Electrospun silk-elastin-like fiber mats for tissue engineering applications

Protein-based polymers are present in a wide variety of organisms fulfilling structural and mechanical roles. Advances in protein engineering and recombinant DNA technology allow the design and production of recombinant protein-based polymers (rPBPs) with an absolute control of its composition. Although the application of recombinant proteins as biomaterials is still an emerging technology, the possibilities are limitless and far superior to natural or synthetic materials, as the complexity of the structural design can be fully customized. In this work, we report the electrospinning of two new genetically engineered silk-elastin-like proteins (SELPs) consisting of alternate silk- and elastin-like blocks. Electrospinning was performed with formic acid and aqueous solutions at different concentrations without addition of further agents. The size and morphology of the electrospun structures was characterized by scanning electron microscopy showing to be dependent of concentration and solvent used. Treatment with air saturated with methanol was employed to stabilize the structure and promote water insolubility through a time-dependent conversion of random coils into β-sheets (FTIR). The resultant methanol-treated electrospun mats were characterized for swelling degree (570-720%), water vapour transmission rate (1083 g/m2/day) and mechanical properties (modulus of elasticity of ~126 MPa). Furthermore, the methanol-treated SELP fiber mats showed no cytotoxicity and were able to support adhesion and proliferation of normal human skin fibroblasts. Adhesion was characterized by a filopodia-mediated mechanism. These results demonstrate that SELP fiber mats can provide promising solutions for the development of novel biomaterials suitable for tissue engineering applications.

This work was financially supported by the European Comission via the 7th Framework Programme project EcoPlast (FP7-NMP-2009-SME-3, collaborative project number 246176), by Portuguese funding from FEDER through POFC – COMPETE and PEst project C/BIA/UI4050/2011 (Portugal), PEST-C/FIS/UI607/2011 and PEST-C/QUI/UIO686/2011. By MICINN (MAT 2009-14195-C03-03, IT2009-0089, ACI2009-0890, MAT2010-15310 and MAT2010-15982), the JCyL (VA034A09, VA030A08 and VA049A11-2) and CIBER-BBN. E.C. (Spain). The authors also thank funding from Matepro –Optimizing Materials and Processes”, ref. NORTE-07-0124-FEDER-000037”, co-funded by the “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte), under the “Quadro de Referência Estratégico Nacional” (QREN), through the “Fundo Europeu de Desenvolvimento Regional” (FEDER). RM, AC, CMC and VS acknowledge FCT for SFRH-BPD/86470/2012, SFRH/BD/75882/2011, SFRH/BD/68499/2010 and SFRH/BPD/63148/2009 grants, respectively