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Author ORCID Identifier

0000-0002-7809-6714

AccessType

Open Access Dissertation

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Chemical Engineering

Year Degree Awarded

2020

Month Degree Awarded

September

First Advisor

Sarah L. Perry

Subject Categories

Other Chemical Engineering

Abstract

Recent work in the area of protein encapsulation has turned away from traditional methods of sequestration toward gentler, purely aqueous techniques. Among them, complex coacervation has become a topic of discussion. Complex coacervation is an all-aqueous liquid-liquid phase separation phenomenon dominated by electrostatic interactions and entropic gains. The use of coacervates as protein encapsulants has garnered much attention, but there has been little headway in determining a set of design rules. We considered coacervation between two oppositely-charged polypeptides and a biomacromolecule cargo to investigate the effects of changing aspects of the coacervating polymers and/or various solution parameters. We characterized the level of encapsulation and partitioning of three different model proteins as a function of ionic strength, pH, polymer chain length, and polymer charge density. Our results highlighted the importance of electrostatic interactions in driving protein uptake into the coacervate phase. While intuitive effects such as increasing protein charge facilitating uptake and increased salt concentration decreasing uptake due to electrostatic screening effects, we determined that the net charge and the distribution of charges on both the protein and the polymers dominated protein incorporation. For example, the presence of a cluster of cationic residues on the surface of lysozyme resulted in several orders of magnitude higher protein incorporation than was observed for serum albumin and hemoglobin, which have a more isotropic distribution of charges. We confirmed this trend, comparing the encapsulation of two variants of caspase-6 with the variant with a cationic charge patch yielding a higher encapsulation efficiency than the other.

DOI

https://doi.org/10.7275/18409683

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