Thermotropic liquid crystals from engineered polypeptides
Liquid crystal (LC) can be defined as the “delicate phase of matter” and it lies in between the liquid and the solid state. Molecules in the liquid crystalline phase are ordered and oriented, as in crystals, but can flow like a liquid. The LC state is characteristic of many biological materials. The LCs described in this thesis are based on genetically engineered Elastin-Like Polypeptides (ELPs) derived from naturally occurring elastin proteins. The ELP based LCs were realized in absence of water, by electrostatic complex formation between the ELPs and surfactants with flexible alkyl chains. This fabrication procedure resulted in the formation of solvent-free thermotropic LCs with high thermal stability.
The lengths of the ELPs and surfactant alkyl chains were found to be extremely important in tuning the physical properties of the LCs. We also observed high elastic values for the liquid crystalline materials and their elastic moduli can be tuned conveniently by choosing the alkyl chain length or the molecular weight of the ELPs.Finally, we investigated how the pristine ELP material (without surfactant) interacts with mammalian cells. We observed enhanced cellular uptake correlated with the number of charges of ELP. At the same time, ELPs showed remarkably low cytotoxicity and resistance to degradation in the cell.
The results presented in the different chapters, dealing with the fabrication and properties of highly charged unfolded polypeptide structures and their various potential applications, qualify these bioinspired architectures as a new and exciting class of biomaterials with many prospect for the future.