Synthesis and Characterization of Elastin-Mimetic Protein Gels Derived from a Well-Defined Polypeptide Precursor

Abstract

To elucidate the effects of uniformity of molecular architecture on gel properties, a protein polymer based on the elastin-mimetic repeat sequence [(Val-Pro-Gly-Val-Gly)4(Val-Pro-Gly-Lys-Gly)], 1 (Lys-25), was synthesized using genetic engineering and microbial protein expression. The regularly placed lysine residues in poly(Lys-25) underwent selective reaction with electrophilic cross-linkers under mild conditions in either dimethyl sulfoxide or aqueous phosphate buffer to afford solvent-swollen networks. Chemical derivatization and spectroscopic investigations of the cross-linking reaction indicated that approximately 85% of the lysine residues reacted with the cross-linker. The protein hydrogel exhibited reversible, temperature-dependent expansion and contraction with an estimated midpoint temperature for the phase transition at 35 °C. Scanning electron microscopy (SEM) investigations indicated profound differences in morphology between protein gels prepared in organic vs aqueous solution.