429616 Effect of Supercharging on Coacervation Between Proteins and Polyelectrolytes

Monday, November 9, 2015: 5:15 PM
251E (Salt Palace Convention Center)
Allie Obermeyer, Xuehui Dong, Carolyn Mills and Bradley D. Olsen, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA

The encapsulation of proteins in complex coacervate core micelles serves as a promising technology for protein drug delivery and patterning. However, most proteins do not form complex coacervate core micelles with ionic-neutral block copolymers. Unlike DNA or RNA, which possess a uniform negative charge, proteins have a relatively low charge density, a “patchy” charged surface, and a specific, globular fold. Chemical modification of proteins to generate a more uniformly supercharged species provides a simple strategy to generate protein based complex coacervate core micelles. However, the fundamental understanding of the principles of complex coacervation between proteins and ionomers is underdeveloped. Using mass spectrometry, we were able to quantify the formal charge distribution of modified proteins. A panel of proteins with varying charge densities was synthesized and their propensity to form complex coacervates with model polyelectrolytes was measured. While the model proteins studied do not readily form coacervates in their native state, the proteins all formed coacervates once they surpassed a critical ratio of negatively to positively charged residues. Additionally, as the protein charge density increased the proteins formed coacervates over an increasing range of polymer ratios. Finally, the charge ratio at maximum coacervation indicates a strong induced charging effect of the protein in the coacervate phase. These bulk coacervation studies were translated to the design of complex coacervate core micelles. The micelles were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM).

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See more of this Session: Charged and Ion-Containing Polymers
See more of this Group/Topical: Materials Engineering and Sciences Division