Understanding the Phase Behavior of a Multistimuli-Responsive Elastin-like Polymer: Insights from Dynamic Light Scattering Analysis

Abstract

Elastin-like polymers are a class of stimuliresponsive protein polymers that hold immense promise in applications such as drug delivery, hydrogels, and biosensors. Yet, understanding the intricate interplay of factors influencing their stimuli-responsive behavior remains a challenging frontier. Using temperature-controlled dynamic light scattering and zeta potential measurements, we investigate the interactions between buffer, pH, salt, water, and protein using an elastin-like polymer containing ionizable lysine residues. We observed the elevation of transition temperature in the presence of the common buffering agent HEPES at low concentrations, suggesting a "salting-in" effect of HEPES as a cosolute through weak association with the protein.Our findings motivate a more comprehensive investigation of the influence of buffer and other cosolute molecules on elastin-like polymer behavior.

Genetic Functionalization of Protein-Based Biomaterials via Protein Fusions

“…Because protein assembly is driven, at least initially, by noncovalent interactions, the physical and chemical environment can have a substantial impact on materials formation. Thus, phase behavior is an inherent property of self-assembling proteins, and a deeper understanding of how to add or eliminate the dependence of assembly on a particular parameter is needed to design new, sensitive protein systems and to enable their reliable use in many applications . In particular, a prominent characteristic of many ELPs is multiphase behavior, in which monomers respond to many stimuli and/or have multiple temperature transitions. − Because each phase transition is sequence-dependent, fusing two ELPs together, each with a different sequence, will create a protein with multiple transitions, and thus multiple phases .…”

“…Thus, phase behavior is an inherent property of self-assembling proteins, and a deeper understanding of how to add or eliminate the dependence of assembly on a particular parameter is needed to design new, sensitive protein systems and to enable their reliable use in many applications . In particular, a prominent characteristic of many ELPs is multiphase behavior, in which monomers respond to many stimuli and/or have multiple temperature transitions. − Because each phase transition is sequence-dependent, fusing two ELPs together, each with a different sequence, will create a protein with multiple transitions, and thus multiple phases . This idea is extended in artificial IDPs designed by the Chilkoti lab, which designed two proteins, one an artificial PGXG-repeat ELP, and the other a partially ordered polymers (ELP with polyalanine helices inserted within the sequence).…”

“…Such changes elicit structural transitions in first-generation materials. Second, many applications require predictable behavior, so that the materials only respond to a specific desired event (e.g., ligand binding), and not to other factors such as changes in pH, ion concentration, or electric potential that can occur in vivo . One answer to this design issue is to use unnatural amino acid incorporation to photo-cross-link the materials, thus trapping them in the preferred form …”