Poster C9 - Comparing the use of brain-derived and synthetic phosphatidylserine in lipid-polymer hybrid particles for modulating macrophage inflammation

Thursday, October 24, 2024

10:00 AM – 11:00 AM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Caroline Rucker

Undergraduate Researcher
University of South Carolina
Powhatan, Virginia, United States

Primary Investigator(s)

MG

Michael Gower

Associate Professor
University of South Carolina, United States

Co-Author(s)

KA

Kidochukwu Atube

Graduate Research Assistant
University of South Carolina, United States

Introduction: Macrophages are immune cells that respond to inflammatory stimuli throughout the body. Macrophage dysfunction contributes to many aspects of chronic inflammatory disease. Thus, macrophages are an important target for therapies to resolve chronic inflammation. In previous work, we successfully synthesized poly(lactide-co-glycolide) (PLG) particles surface-functionalized with phosphatidylserine (PS) (Fig. 1A). On the surface of cells undergoing apoptosis, PS functions as an “eat me” signal and a cue to resolve inflammation. Accordingly, macrophages bind and take up PS-bearing apoptotic cells through cell-surface receptors, and subsequently initiate an anti-inflammatory response. Likewise, we have shown that PS-presenting PLG (PS:PLG) particles are readily taken up by lipopolysaccharide (LPS)-inflamed bone marrow-derived macrophages (BMDMs) and decrease the secretion of inflammatory cytokines TNF-a and IL-6 while increasing the release of IL-10, an anti-inflammatory cytokine. However, for those studies, the PS used was derived from porcine brain, which is not recognized as safe by the FDA due to concerns involving the transmission of infectious encephalopathies such as mad cow disease. Hence, in this study, we sought to use 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS), a synthetically derived PS, and compare its efficacy to the porcine brain-derived PS.

Materials and

Methods: We fabricated DOPS-presenting PLG (DOPS:PLG) particles using an oil-in-water emulsion technique and compared their efficacy to porcine brain-derived PS-presenting PLG particles (B-PS:PLG) particles in targeting and modulating macrophage inflammation. Using transmission electron microscopy, we investigated the organization of PS on the particle surface. Furthermore, we quantified PS loading using nuclear magnetic resonance. Then, we evaluated the ability of these particles to target macrophages by measuring macrophage-particle interactions and particle uptake with flow cytometry. We also utilized ELISA to measure levels of inflammatory cytokines TNF-a and IL-6 and anti-inflammatory cytokine IL-10 secreted by bone-marrow derived macrophages (BMDMs) co-treated with lipopolysaccharide (LPS), an inflammatory stimulus, and either B-PS:PLG or DOPS:PLG particles. In this way, we measured the ability of each particle type to modulate macrophage inflammation.

Results, Conclusions, and Discussions: We observed that DOPS:PLG particles presented a unique flower-like morphology when compared to B-PS:PLG particles, which presented a spherical morphology (Fig. 1B). Despite this difference, DOPS:PLG particles achieved the same loading of PS. Importantly, we found that DOPS:PLG particles were able to target and modulate LPS-induced inflammation in BMDMs with the same efficacy as particles made with brain-derived PS (Fig. 1C,D). These findings advance the use phosphatidylserine-PLG hybrid particles as a potential therapeutic for patients with chronic inflammation. Future studies will investigate the use of these DOPS:PLG particles to deliver small-molecule drugs that can further modulate the anti-inflammatory effects of the particles.

Acknowledgements (Optional): The Office of Undergraduate Research at the University of South Carolina for providing funding through the Magellan Scholar Award.
The Barry Goldwater Scholarship and Excellence in Education Foundation for providing funding through the Goldwater Scholarship.