(586a) High Modulus Thermoresponsive Elastin-like Polypeptide Gels As New Injectable Biomaterials

Injectable biomaterials have attracted a great deal of interest for facilitating minimally invasive medical procedures, enabling faster patient healing and lower medical costs. A major area of continued need is injectable materials that can achieve a very high modulus, greater than 1 MPa, in their hardened state, enabling their application in relatively stiff tissues such as cartilage. Here, we report a new high stiffness hydrogels generated from elastin-like proteins (ELPs) at 15-30 wt.% solids, in the range of the protein content in natural body tissue. Although ELP solutions are fluids below body temperature and typically form macrophase separated precipitates at high temperature, specific ELP sequences can instead form kinetically arrested macrophase separated structures that lead to the formation of extremely stiff gels upon heating to body temperature, enabling injection of a material that develops an ultimate modulus of more than 1 MPa with a rapid initial set in less than a minute. Small-angle neutron scattering and oscillatory shear rheology provide a detailed picture of the kinetically arrested microstructure and the time evolution of mechanical properties, and large amplitude oscillatory shear rheology is applied to provide insight into the way network structures break under larger deformation. Through simple oxidative chain extension to prepare very high molar mass proteins, the toughness of the gels may also be significantly increased, presumably due to the intertwining of single chains between many different kinetically aggregated domains within the gels. Finally, cell culture experiments performed using chondrocytes and mesenchymal stem cells demonstrate a high degree of biocompatibility and the potential of these materials as cell culture matrices for tissue engineering applications.