CHBE Seminar: Dr. Whitney Blocher McTigue, Lehigh University
Friday, November 17, 2023
Room 2108 Chemical and Nuclear Engineering Building and Via Zoom
Polyelectrolyte Complexes: The Intersection of Vaccine Stability and Depolymerization
Abstract: Polymer physics plays an important role in a variety of aspects in the realms of health and energy. Here, I will discuss the utilization of polymers for biomacromolecule encapsulation and stabilization and polymer depolymerization to answer questions surrounding biomimicry and understanding complex mechanisms of depolymerization, while exploring the fundamentals of polymer physics. To start, vaccines and other therapeutic cargoes are made, transported, and stored along a “cold chain,” a system designed to maintain the refrigeration of these fragile cargoes. 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. To combat this, methods for decreasing the reliance of these cargoes on the cold chain have garnered attention, with many efforts focusing on protein encapsulation strategies. Recent work has focused on purely aqueous techniques, with complex coacervation, a type of charged polymer solution, representing one promising route to protein encapsulation. 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 protein uptake into coacervates. We explored the incorporation of three model proteins as a function of solution conditions, polymer properties, and the distribution of charges on the proteins. Overall, 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 geared towards understanding the specific ways in which the coacervate environment can affect protein and/or virus activity, including the potential for solvent removal.
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.
Bio: Dr. Blocher McTigue earned her B.S. in Chemical Engineering at Clarkson University in 2015 and her Ph.D. 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. She completed a postdoc under Prof. Charles Sing in the Department of Chemical & Biomolecular Engineering at the University of Illinois at Urbana-Champaign investigating the simulation and modeling of polymers to better understand the kinetics and mechanisms of depolymerization. Dr. Blocher McTigue is now an assistant professor in the Department of Chemical & Biomolecular Engineering at Lehigh University. Her goal is to combine her experimental expertise and newfound knowledge in utilizing polymers for biomedical applications in her new lab.