BPS2026 – Protease-driven coacervation of elastin-like polypeptides

Coacervates made from elastin-like polypeptides (ELPs) are promising biomaterials with applications in drug delivery and tissue engineering. Typical therapeutic delivery strategies for ELP coacervates leverage the temperature responsiveness of ELPs. In this approach, an ELP solution is heated above a sequence-dependent transition temperature to drive ELP coacervation. To enable novel strategies for delivering ELP coacervates, we designed “cleavable” ELPs that undergo protease-driven coacervation at constant temperature. Furthermore, we investigated how cleavable ELP sequences impact their hierarchical assembly and subsequent protease responsiveness.Cleavable ELPs comprise two ELP blocks with different hydrophobicities connected by a peptide sequence that is recognized and cleaved by a protease. One ELP block is enriched with hydrophobic amino acids to promote coacervation, whereas the other ELP block has more hydrophilic amino acids to promote solubility prior to proteolytic cleavage. Protease-driven coacervation proceeds upon liberation of the more hydrophobic product of proteolytic cleavage. Protease-driven coacervation is monitored by increased solution turbidity.Cleavable ELP variants with different hydrophilic block polarities were designed to characterize sequence impacts on cleavable ELP solubility and self-assembly. Increasing the polarity of the hydrophilic block generally increased the solubility of the cleavable ELP. Polarity additionally impacted the hierarchical assembly of cleavable ELPs. Temperature-resolved turbidity, dynamic light scattering, and microscopy demonstrate that cleavable ELPs with uncharged hydrophilic blocks undergo coacervation above their transition temperature. In contrast, cleavable ELP variants with charged hydrophilic blocks undergo micellization above their critical micelle temperature, as demonstrated using small-angle X-ray scattering and cryogenic electron microscopy. These ELP micelles retain their protease-responsive behavior and undergo protease-driven micelle-to-coacervate transitions. This presents exciting opportunities to leverage traditional micelle-based drug delivery strategies to deliver ELP coacervates to tissues with high protease expression.