Associate Professor Sarah Perry of the UMass Amherst Chemical Engineering (ChE) Department has been chosen as one of two national recipients of the 2024 American Chemical Society (ACS) Macro Letters/Biomacromolecules/Macromolecules Young Investigator Award. According to the ACS, “Professor Perry was selected for this award due to her important and insightful contributions to the field of polyelectrolyte self-assembly and the incorporation of proteins into these assemblies.” 

Perry and her fellow recipient, Professor Brett Fors of Cornell University, will be honored during an award symposium at ACS Fall 2024 in Denver, Colorado, from August 18 to 22.

Research in the Perry Group utilizes self-assembly, molecular engineering, and microfluidic technologies with a goal of understanding and mimicking biomaterials to address real-world challenges. As Perry explains, “My group works on self-assembling materials. We are interested in understanding how we can use different interactions between molecules to make and tune materials, and there is a huge range of interesting questions that we can pursue.” 

Much of the work that Perry has done has used electrostatic interactions. Polyelectrolyte complexation involves self-assembly driven by the interaction of oppositely charged polymers, surfactants, proteins, etc. 

According to Perry, “Polyelectrolyte complexes have been known for nearly a century. These materials are how your shampoos work. Industry has long used polyelectrolyte complexes to encapsulate flavors and fragrances. The assembly of these materials can even be used to mimic the texture and mouth feel of fats/oils in fat-free salad dressing.” 

Beyond the industrial applications, there are also significant parallels between polyelectrolyte complexes and a new class of organelles in living cells termed ‘membraneless organelles’ or ‘biomolecular condensates.’ These compartments form via liquid-liquid phase separation, in much the same way that oils form separate droplets in water, and have been shown to have a range of important functions. 

Important to the work in the Perry group, these condensates typically form as a complex between an intrinsically disordered protein (which Perry says, “looks an awful lot like a polymer”) and RNA. Researchers around the world are now looking to understand how the sequence of these disordered proteins allows them to function.

According to Perry, “While we are not studying the actual biology of these materials, we are trying to understand how polymer sequence and chemistry can affect assembly and the incorporation of guest proteins.” 

One good example of this work in Perry’s lab is how to address challenges in the temperature sensitivity of vaccines. “Biomolecular condensates are able to very specifically and selectively take up target proteins and keep them stable. We are working to understand and mimic that process, but using far simpler materials than cells do.”

Beyond this bioinspired work, Perry’s group is also working to understand and process liquid polyelectrolyte complexes into solid materials. “Most of the plastics that we use in our everyday lives are formed, coated, extruded, etc. into their final shape by either melting at high temperatures or by casting from an organic solvent,” Perry explains. “However, polyelectrolyte complexes can be processed from water. This represents an opportunity to transition to a more environmentally friendly way of making materials.”

One great example of this is work that Perry’s group has been pursuing in collaboration with ChE Professor Jessica Schiffman. As Perry explains, “The Schiffman lab [members] are experts in both natural polymers, which are commonly used in polyelectrolyte complexation, and in the use of electrospinning to create nanofibers. Together, we demonstrated the first example of electrospinning of polyelectrolyte complexes.” 

Researchers had tried to electrospin polyelectrolyte complexes before but had always needed to resort to indirect and complicated strategies. “Instead,” says Perry, “we were able to leverage our understanding of how these materials self-assemble, and how salt can be used to tune the liquid vs. solid state of polyelectrolyte complexes to enable direct spinning of the materials.”

Perry adds that her team has also been working more recently to understand how the act of changing parameters – such as the length of polymers, charge density, or adding various other chemistries – affects the strength, brittleness, and temperature sensitivity of polyelectrolyte complexes. 

For example, as Perry recalls, “Seven years ago, two undergraduate students in my lab had the idea of using polyelectrolyte complexation to create organic, solvent-free, nail polish. They made beautiful examples by incorporating food dye into their formulations. However, the ultimate material was so brittle that it would just flake off when touched.” 

However, explains Perry, “In the intervening time we have tested out a range of different polymers and polymer properties and can now do the same demonstration and create a very robust coating.” 

As Perry sums up her research goals, “We continue to push forward to understand how to make and use polyelectrolyte-complex materials. We are thinking about how patterns of charge and other chemistries affect the incorporation of proteins and viruses into our materials and how we can leverage this knowledge to improve formulation strategies for products like therapeutics, biocatalysts, and sensors.” (June 2024)

Article posted in Faculty