The interaction of cationic nanoparticles with mouse capillary endothelial cells in situ and in vivo

We addressed the question of whether cationic nanoparticles of 50-300 nm diameter could cross the vascular capillary endothelium in a process similar to clearing transcytosis. This problem presents interest in the field of drug targeting by paniculate carriers. We used acrolein nanoparticles of 150-300 nm in diameter and colloidal gold of 50 nm, both coated with cationized ferritin. At 30 min after in situ perfusion of mice, acrolein nanoparticles appeared in punctual contact with the plasmalemma in heart and lung capillaries, with some particles in an incipient stage of internalization. Similar experiments with colloidal gold revealed a continuous layer of particles on the surface of heart and lung endothelium. However, there were no particles internalized in the endothelium or transported in the subendothelial space. In lung and heart tissue, at 3 and 24 hours after the intravenous injection, acrolein nanoparticles appeared isolated or in small groups of up to five particles, close to the endothelial luminal membrane or in contact with the endothelium, and very rarely attached to slight invaginations of the endothelial membrane. In lung we noticed acrolein nanoparticle aggregates (5-20 particles) internalized in leukocytes. Groups of 5-50 colloidal gold particles appeared internalized in endothelial cells of heart and lung at 24 h after injection in vivo. During the experiments no particles were detected in the subendothelial space.