V38 - Analyzing the Pharmacodynamics of Nerve-Targeting Polymersomes to Manage Pain Post Sciatic Nerve Injury

Saturday, October 11, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Megan Curto

Student
Clemson University, United States

Co-Author(s)

VL

Vivian LaChanse

Student
Clemson University, United States
KT

Kayleigh Trumbull

PhD Student
Northwestern University, United States
SF

Sophia Fetten

Student
Clemson University, United States
Noah Arnold

Phd candidate
Clemson University Chemical and Biomolecular Engineering
Seneca, South Carolina, United States
Vanessa Marahrens

Student
Clemson University
Savage, Minnesota, United States
OM

Olivia Myers

Student
Clemson University, United States
JT

Jeffery Twiss

Professor
University of South Carolina, United States

Primary Investigator(s)

Jessica Larsen

Associate Professor
Clemson University, South Carolina, United States

Introduction: : When a peripheral nerve is injured, typically by a traumatic crush or severance, the resulting damage is often permanent. In addition to functional loss, nerve injury gives rise to significant and persistent pain. This pain is driven by pathological changes within the nerve including inflammation and the spontaneous firing of injured neurons. These mechanisms are not unique to traumatic injury. They’re shared across a broad range of pain conditions, where sensitization of peripheral nerves contributes to the overall pain state. Since peripheral nerves serve as the origin of pain signals, they represent a key target for therapeutic intervention. Local nerve blocks, commonly achieved using agents such as lidocaine, silence activity at the source, offer a promising approach for broadly managing pain. However, their effectiveness is limited by the blood-nerve barrier (BNB). The BNB, composed of tight junctions, serves to protect the nerve by limiting harmful substances from entering via the bloodstream, in turn also preventing many potentially therapeutic agents from reaching the nerve. To bypass the BNB and enable non-invasive delivery, targeted nanoparticles called polymersomes have been developed to carry payloads of lidocaine and epinephrine directly to nerve post-injury, allowing for prolonged analgesic effects.

Materials and

Methods: : Polymersomes are vesicles made from amphiphilic block co-polymers. The backbone of our polymersome is polyethylene glycol (PEG, 1000 Da)-b-polylactic acid (PLA, 5000 Da) (PEG-PLA). A hydrophilic fraction of 25-40% leads to the formation of a vesicle (Figure 1), which contains a hydrophobic core, an aqueous center, and an exterior layer of PEG that shields the vesicle. Targeted delivery is achieved by attaching ligands to the exterior PEG layer. The ligands explored to enhance BNB bypassing were Apolipoprotein E3 (ApoE), to target inflammation, and Rabies virus glycoprotein-based peptide (RVG29), to target nicotinic acetylcholine receptors (nAchR) and neural cell adhesion molecules (NCAM). Polymersomes were created with and without tags. They were characterized using dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), and transmission electron microscopy (TEM). Ligand attachment was confirmed via protein assays. MTS assay was performed to determine their impact on cell viability. AlexaFluor647 (AF647), a near infrared dye, was encapsulated to track polymersomes after injection. Release of AF647 was performed using untagged and tagged polymersomes to confirm maintained release. A sciatic nerve injury (ScNI) was created in Sprague Dawley rats (AUP 2023-0215), followed by intranerve (IN) or intramuscular (IM) injection of 100 mM polymersomes with AF647. The animals were monitored for 48 hours, during which they were imaged using IVIS, and blood plasma samples were collected at 1, 4, 24, and 48 hours post-injection. After identifying pharmacokinetic properties of polymersomes, lidocaine and epinephrine were loaded during the formation of the polymersomes, prior to assessment of pain management in injured rats.

Results, Conclusions, and Discussions:: Polymersome formulations were fully characterized (Figure 1A-C) by narrow size distribution, low polydispersity index (PDI), and vesicular structure, confirming consistent particle formation. Successful ligand attachment was verified through changes in physical and surface properties. ApoE, a 299 amino acid protein, increased particle size and was visualized using TEM. RVG, a cationic molecule, shifted surface charge from negative to positive and increased size variability, both indications of successful binding. All formulations showed consistent release behavior and demonstrated no cytotoxicity in SH-SY5Y cells. These results confirm that untagged and tagged polymersomes are stable, biocompatible, and well-suited for targeted delivery to nerve tissue. Sprague Dawley (SD) rats underwent unilateral ScNI, followed by either an IN or IM injection of untagged, ApoE-tagged, or RVG-tagged (n=3 per route) polymersomes. In Figure 2, radiant efficiency of dye in the injury site was quantified via IVIS at 1, 4, 24, and 48 hours post injection. With IN injection, both ApoE and RVG-tagged polymersomes enabled high AF647 retention in the nerve at one hour. With IM injections, RVG enabled fluorescence at the nerve 1 h post-injection. RVG led to the highest detectable fluorescence, likely due to specificity toward neural receptors. For IM, reduced retention was expected due to the need to overcome the BNB. In post-mortem assessment of ScNI, the highest amount of AF647 was observed in rats injected IN with ApoE-tagged polymersomes (Figure 3), suggesting retention in the nerve for at least 48 h. Overall, ApoE enables longer nerve retention, while RVG improves nerve penetration. SD rats were euthanized, and organs were collected for post-mortem analysis. H&E staining confirmed healthy tissue. Lidocaine was encapsulated at an efficiency of 47.53 ± 12.86 [%]. Pain was assessed using behavioral measures including burrowing, grooming, body weight, Von Frey testing, and the Facial Grimace Scale.

Acknowledgements and/or References (Optional): :