Properties of rapamycin solid lipid nanoparticles for lymphatic access through the lungs & part I: the effect of size.

Abstract

Background: Lymphangioleiomyomatosis (LAM)is characterized by growth of smooth muscle-like cells in the lungs that spread to other organs via lymphatic vessels. Current oral rapamycin treatment is limited by low bioavailability of approximately15%. Aim: The effect of inhaled rapamycin solid lipid nanoparticles (Rapa-SLNs) size on its penetration through the lymphatics. Method: Three Rapa-SLN formulations (200-1000nm) were produced and assessed for particle characteristics and further for toxicity and performance in vitro. Results: Rapa-SLNs of 200nm inhibited proliferation in TSC2-negative mouse embryonic fibroblast cells and penetrated the respiratory epithelium and lymphatic endothelium significantly faster compared with free rapamycin and larger Rapa-SLNs. Conclusion: Rapa-SLN approximately 200nm allows efficient entry of rapamycin into the lymphatic system and is therefore a promising treatment for LAMpatients.