Abstract
Lymphatic vessels have received considerable attention in recent years as delivery route for immune modulatory therapies to the lymph nodes. Lymph node targeting of immunotherapies and vaccines has been shown to significantly enhance their therapeutic efficacy. Lymphatics transport functions materials from peripheral tissues to the lymph nodes, including small 10 – 250 nm therapeutic nanoparticles. While size required to enter lymphatic vessels, surface chemistry is more poorly studied. Here, we probed the effects of surface poly(ethylene glycol) (PEG) density on nanoparticle transport across lymphatic endothelial cells (LECs). We differentially PEGylated model carboxylate-modified polystyrene nanoparticles to form either a brush or dense brush PEG conformation on the nanoparticle surfaces. Using an established in-vitro lymphatic transport model, we found that the addition of any PEG improved the transport of nanoparticles through lymphatic endothelial cells (2.5 - 2.6 ± 0.9% transport efficiency at 24 hours) compared to the unmodified PS-COOH nanoparticles (0.05 ± 0.05% transport efficiency at 24 hours). Additionally, we found that transcellular transport is maximized (4.2 ± 0.7% transport efficiency at 24 hours) when the PEG is in a dense brush conformation on nanoparticle surfaces, corresponding with a high grafting density (Rf/D = 4.9). These results suggest that PEG conformation has a crucial role in determining translocation of nanoparticles across LECs and into lymphatic vessels. Thus, we identified PEG density as a major design criteria for maximizing lymphatic targeting of therapeutic nanoparticle formulations that can be widely applied to enhance immunotherapeutic and vaccine outcomes in future studies.
Competing Interest Statement
The authors have declared no competing interest.
