**WINNER**
Student(s): Lillian Wu
Project: The Synergistic Activity of Positively Charged Liposomes and LL-37 on Bacteria | View Poster (PDF)
Major(s): Chemical Engineering (Biology minor)
Advisor(s): Angela Brown
Abstract
As antibiotic resistance presents a growing hazard to public health, novel antibiotics are an invaluable area of study. One promising possibility is LL-37, an antimicrobial peptide found in the human immune system that possesses significant, broad spectrum antibacterial activity, primarily through membrane disruption. Previous work in our lab showed an unexpected increase in the antibacterial activity of LL-37 when it was delivered in conjunction with liposomes composed of the cationic lipid, DOEPC. To explain this finding, we hypothesized that LL-37 and cationic lipids possess a synergistic mechanism against bacteria due to further membrane disruption by the cationic liposomes, causing increased LL-37 uptake. To test this, we studied bacterial growth under a constant, inhibitory concentration of LL-37 with varying concentrations of cationic liposomes, composed of varying ratios of neutrally or positively charged lipids. Neutrally charged POPC liposomes inhibited the activity of LL-37, with a positive correlation between higher liposome concentrations and bacterial growth. Conversely, positive DOEPC liposomes exhibited synergistic action with LL-37, demonstrating a negative correlation between higher concentrations of liposomes and bacterial growth. Additionally, the effect was dose-dependent, with intermediate effects observed in 50% DOEPC/50% POPC liposomes. The effect was observed in both Escherichia coli and Aggregatibacter actinomycetemcomitans. These results show a clear trend between increasing cationic lipid concentration and bacteria, suggesting the promise of cationic lipids to bolster the antibacterial action of LL-37. Current work focuses on further confirming this effect and elucidating the mechanism of the combined activity of antimicrobial peptides and cationic liposomes.
About Lillian Wu
Lillian Wu is a sophomore majoring in chemical engineering and minoring in biology. As a Clare Boothe Luce Fellow, she has been conducting research in Professor Angela Brown’s lab, investigating host defense peptide interactions with bacteria, in hopes of facilitating the development of novel, broad spectrum antibiotics to combat the growing challenge of antibiotic resistance. She is also a Global Social Impact Fellow, working on the CareAlert team to develop a pager system for appointment reminders, medication availability alerts, and healthcare infrastructure support. Lillian and the team intend to implement their technology in rural Sierra Leone to combat the high regional maternal mortality rate. After graduation, she hopes to complete graduate work before pursuing a career in biomedical research with the potential to alleviate inequity and promote social change. Lillian is originally from Oklahoma and enjoys outdoor recreation, horseback riding, reading, thrifting, and upcycling outside of the lab.