Recombinant protein-based hydro-gels for biotech applications

Dissertação de mestrado em Genética Molecular ; Silk elastin-like protein (SELP) hydrogels are an example of protein-based materials that have gained interest in the past years for biomedical and biotechnological applications, due to their remarkable properties such as biocompatibility and biodegradability. SELPs are a class of recombinant proteins, typ ically composed of silk-like (GAGAGS) and elastin-like (VPGVG) blocks. In aqueous solutions, some of these polymers demonstrated the ability to self-assemble, through a temperature-mediated process, lead ing to the formation of a hydrogel. The mechanism behind the gelation of SELPs is thought to be driven by a combination of two factors, the crystallization of the silk-like blocks and the thermoresponsive behav iour of the elastin-like blocks, which aggregate and become insoluble after reaching a specific transition temperature (Tt). While several studies report the use of SELP-based hydrogels, the focus is usually on their applicability, lacking insights on the chemical structural and physical properties. Based on this, the main objective of this dissertation was to perform a thorough study on the effect of composition, concen tration and curing temperatures on the physical-chemical properties of SELP-based hydrogels. Three different SELP copolymers with similar molecular weights, namely SELP-59-A, SELP-520- A, and SELP-1020-A, were used, with differences in both the silk-to-elastin ratio and the length of each block. The SELPs used had their elastin block based on the pentamer VPAVG, which is known to confer an acute thermal hysteresis. The obtained results demonstrate the versatility of SELPs for the develop ment of hydrogels, since that, by using only three polymers and by varying their concentrations and cure temperatures, an assortment of different properties was obtained. The thermo-responsive behaviour was shown to be reversible at some extent coupled with an acute hysteresis behaviour, being dependent on both polymer concentration and composition. ...