(337cz) Tyrosine Crosslinking of ELP Hydrogels for Tissue Engineering Applications

Research Interests . Biomaterials with tunable abilities and reliable mechanical characteristics are essential for many tissue engineering applications. Elastin like polypeptides (ELPs) are prominent candidates for designing biomaterials because of numerous reasons. They are genetically encodable, making them tunable and allows enormous control in their design. Also, they express high yields in a bacterial host like Escherichia coli (E. coli). Their LCST phase behavior can be easily taken advantage of and used in their purification process. Crosslinking of linear ELPs of general form (VPGXG)_n with guest residue ‘X’, results in gelation to form hydrogels with superior mechanical and biological properties. Gelation of these ELPs results in designing biocompatible and genetically modifiable biomaterials that includes ability to match the mechanical properties of target tissues, in addition to providing biophysical and biochemical cues that direct cell responses and physiological development. Tyrosine based crosslinking in the synthesis of ELP hydrogels can result in biomaterials that have higher level of mechanical and structural characteristics compared to other residues. Dityrosine crosslinks poses mechanical properties like elastic and young’s moduli that can be increased by controlling the number of dityrosine crosslinks as shown by studies with recombinant resilin and silk proteins. The mechanical properties of biomaterials with tyrosine crosslinks are found to be 2-fold higher and capable of holding any shape. Various crosslinkers (enzymatic, metallic, photo catalytic. Etc) were evaluated. Transition metal crosslinkers like Ru (II)bpy₃ ²⁺in the presence of blue light and Ni²⁺ complexed with tripeptide GGH as catalysts were very successful in forming mechanically stable hydrogels. But the presence of heavy metals made the in-vitro biocompatibility of the ELP hydrogel questionable compared to other techniques available in literature. Washing the hydrogels improved the in-vitro biocompatibility of the hydrogels. Compared to washing in batch, continuous flowing system improved the time and efficiency of heavy metal removal and improved biocompatibility. The mechanical and structural properties of the hydrogels were also studied. In- vitro biocompatibility of the hydrogels in after washing were shown to be effective and the hydrogels post-washing can be used directly in experimental studies as biomaterial for various tissue engineering applications.