(113d) The Investigation of the Transition Temperature of Charged and Uncharged Elastin-like Polypeptides in Water and Salt Solutions By QCM-D

Synthetic elastin-like peptide (ELP) designs are based on repetitive amino acid sequences naturally found in the body and are well-known for their predictable stimuli-responsive properties, and biocompatibility which makes them attractive for many biotechnology applications including tissue engineering, drug delivery and protein purification. The inverse phase transition behavior of ELPs behind their stimuli-responsiveness consists of a reversible transformation where ELPs are soluble below their transition temperature (T_t) and insoluble above their T_t. The T_t of ELPs is dependent on the chain length, salt concentration, net charge, hydrophobicity, pH and amino acid content. While the T_t is well-characterized in solution, the same level of understanding does not exist for ELPs tethered to solid surfaces, limiting important surface-based applications in cell culture and sensing. However, measuring surface-based T_t is often challenging. Herein, we used a temperature-controlled quartz crystal microbalance with dissipation (QCM-D) and gold sensors to measure the surface-bound transition temperature of ELPs. Our results demonstrate that the transition temperature of ELPs with an ionic charge (hydrophilic) are higher than ELPs with no charge (hydrophobic) and that addition of salt decreases the T_t, as expected. We also discuss how surface-based T_t behaviors compare behavior in solution. Our results demonstrate that QCM-D is a reliable, accurate technique to measure surface-based T_t. We anticipate that QCM-D will be a pivotal tool in developing predictable models and understanding for surface-based elastin biotechnology applications.