Exploring the properties of genetically engineered silk-elastin-like protein films

Free standing films of a genetically engineered silk-elastin-like protein (SELP) were prepared using water and formic acid as solvents. Exposure to methanol-saturated air promoted the formation of aggregated β-strands rendering aqueous insolubility and improved the mechanical properties leading to a 10-fold increase in strain-to-failure. The films were optically clear with resistivity values similar to natural rubber and thermally stable up to 180 °C. Addition of glycerol showed to enhance the flexibility of SELP/glycerol films by interacting with SELP molecules through hydrogen bonding, interpenetrating between the polymer chains and granting more conformational freedom. This detailed characterization provides cues for future and unique applications using SELP based biopolymers.This work was supported by FCT/MEC through Portuguese funds (PIDDAC) - PEst-OE/BIA/UI4050/2014 and by FCT I.P. through the strategic funding UID/BIA/04050/2013. The authors also thank support from the COST Action MP1206 "Electrospun Nano-fibres for bio inspired composite materials and innovative industrial applications" and MP1301 "New Generation Biomimetic and Customized Implants for Bone Engineering". Authors also acknowledge the Spanish Minister of Economy and Competitiveness (MAT2013-41723-R y MAT2013-42473-R, PRI-PIBAR-2011-1403, and MAT2012-38043) and Junta de Castilla y Leon-JCyL (VA049A11, VA152A12-2 and VA155A12-2), Spain. TC is thankful to the FCT for its support through Programa Ciencia 2008. RMachado, ACosta and VSencadas acknowledge FCT for SFRH-BPD/86470/2012, SFRH/BD/75882/2011 and SFRH/BPD/63148/2009 grants, respectively