Size and Shape Characterization of Thermoreversible Micelles of Three-Armed Star Elastin-Like Polypeptides

Three-armed star elastin-like polypeptides are shown to have the capability of self-assembling into micellar constructs at certain environmental conditions. Here, a study of the size distribution, shape, and molecular weight of these micelles at different salt concentrations and pH values is presented. Multiangle dynamic light scattering was used to study the formation, reversibility, and size of the micelles at different environmental conditions. On the basis of the salt concentration of the solution, two distinct size distribution regimes and a transition region were observed. Static light scattering was performed to study the molecular weight and geometrical anisotropy of the micelles in each regime. The anisotropic behavior and elongation of the particles were independently confirmed by depolarized dynamic light scattering, and a model for micelles at each regime was proposed. The size and molecular weight of the micelles were verified using viscosity measurements. The results of this study suggest that there is big jump in the size and molecular weight of the micelles from the first salt-dependent regime to the other, and the shape of the micelles changes from spheres to cylindrical micelles with a higher than 10:1 axis ratio.