Dense poly(ethylene glycol) coatings maximize nanoparticle transport across lymphatic endothelial cells and accumulate in the skindraining lymph nodes

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.

Targeting Lymphatics for Nanoparticle Drug Delivery

“…In addition to identifying optimum surface characteristics for lymphatic delivery, we also provided some of the first insight on the transport mechanisms involved in the transport of nanoparticles across lymphatic barriers. We found that both paracellular and transcellular transport mechanisms were key in crossing lymphatic barriers, with LECs relying on clathrinmediated endocytosis to mediate transport of PEGylated nanoparticles (McCright et al, 2020).…”

“…They found that the 30 nm formulations were transported into lymph nodes and taken up by CD8 + dendritic cells more effectively than 100 nm and 200 nm formulations of the solid lipid nanoparticles (Nakamura et al, 2020). Recent work by our group has also found that polyethylene glycol (PEG)-coated 40 nm nanoparticles were able to cross lymphatic barriers more efficiently than 100 nm PEG-coated nanoparticles (McCright et al, 2020).…”