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Chemical Engineering Seminar
Dr. Whitney Blocher McTigue
University of Illinois at Urbana-Champaign
Faculty Candidate Research
Polymer physics plays an important role in healthcare and energy. Here, I will discuss the utilization of polymers for biomolecule encapsulation and triggered depolymerization to answer questions surrounding biomimicry and depolymerization kinetics. To start, vaccines and other therapeutic cargoes are made, transported, and stored along a “cold chain,” a system designed to maintain their refrigeration. However, if the vaccine or therapeutic falls outside this cold chain, the standard procedure is to throw it out, as it is challenging to check efficacy at point of administration. As such, protein encapsulation strategies have garnered attention to decrease the reliance on the cold chain. Recent work has focused on purely aqueous techniques, with complex coacervation, a type of charged polymer solution, representing one promising route. Despite increased use of coacervates as protein encapsulants, there has been little headway in determining a set of design rules to engineer these materials. To optimize this, we explored the incorporation of three model proteins as a function of solution conditions, polymer properties, and the distribution of charges on both the protein and the polymers. Based on our results, we hypothesized that complex coacervation could help enhance thermal stability of protein cargo through a combination of physical crowding and “soft” chemical interactions that mimic the natural milieu of the cytosol. We tested this hypothesis using two model viruses and our results indicate the potential for using complex coacervation to enhance the shelf life of vaccines and biologics and set the stage for future efforts.
Still in the realm of polymer physics, our aims turned to another question surrounding polymer depolymerization. Polymers can be designed to undergo depolymerization and can help reduce the global accumulation of plastics in the environment as well as assist in triggerable defouling for applications such as redox flow batteries. One principal strategy to gain insight for both topics is to develop polymers with low ceiling temperatures, which can be reversibly deconstructed (depolymerized) to yield pure monomer following an applied stimulus. It is then possible to re-polymerize recycled materials from the recovered monomer. Here, we use a hybrid of Brownian Dynamics and Monte Carlo simulations to model the interaction of a polymer with a surface that can initiate depolymerization of linear polymers. This can occur either through subsequent “unzipping” events, successive chain scission events, or a combination of these. Informed by these simulations, we developed theoretical models to predict how depolymerization results from a competition of diffusive motion, unzipping, and intra-collision surface scission. This theoretical and computational advance represents a step toward resolving the molecular-level depolymerization kinetics inaccessible to our experimental collaborators.
Dr. Blocher McTigue earned her BS in Chemical Engineering at Clarkson University in 2015 and her PhD in Chemical Engineering from the University of Massachusetts Amherst in 2020. As a graduate student under Prof. Sarah Perry, she focused on using sequence-controlled polypeptide-based complex coacervates to stabilize encapsulated proteins for the thermo-stabilization of vaccines. The last year and a half, Dr. Blocher McTigue has worked under Prof. Charles Sing in the Department of Chemical & Biomolecular Engineering at the University of Illinois at Urbana-Champaign as a post-doctoral researcher investigating the simulation and modeling of polymers to better understand the kinetics and mechanisms of depolymerization. Her goal is to continue in academia as a professor combining her experimental expertise and newfound knowledge in utilizing polymers for biomedical applications.
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