(725h) Targeted Drug Delivery to Atherosclerotic Plaques By VCAM1-Functionalized Liposomal System

Atherosclerosis is the process of plaque formation within the arterial wall that may eventually cause hardening or even blocking of the artery. Despite the progress made in its prevention and pharmacological treatment atherosclerosis is still responsible for 1 out of every 8 deaths in the United States. Current clinical treatments are highly invasive, such as stent surgical procedure, or cause systemic drug toxicity, such as beta and calcium channel blockers. Therefore, there is a need for a more targeted and less invasive therapeutic option for atherosclerosis. The primary goal of this study is to design a surface modified liposomal system with the capability to deliver drug compounds selectively to the sites of arterial plaque in atherosclerosis with minimal systemic toxicity. High cholesterol levels associated with atherosclerosis have been shown to considerably increase vascular-cell adhesion molecule-1 (VCAM1) expression level on the surface of the vascular endothelium monolayer at the site of the plaque. Therefore, VCAM1 molecules have been chosen as the targeting motif for further in-vitro investigation in the current study.

The liposomal system used in this study was composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine, sphingomyelin, cholesterol, and phosphatidylethanolamine-polyethylene glycol (PEG)-cyanur (31.67:31.67:31.67:5 mol%) with a diameter of 357 ± 93 nm and a zeta potential of -17.9 ± 0.5 mV. Anti VCAM1 antibody was conjugated directly to the liposome surfaces in the presence of PEG by covalent binding. Antibody conjugation efficiency was measured at 57.8 ± 8.4%using an ELISA kit and corroborated by confocal microcopy. Cytotoxicity of the liposomes was evaluated using the MTS and Trypan blue assays. Liposomes did not show cytotoxicty in the human macrophage cell line (THP-1) and human umbilical vein endothelial cells (HUVEC). Lipopolysaccharide (LPS) treatment was used to induce high VCAM1 expression in HUVEC cells. Anti VCAM1-functionalized liposomes demonstrated more than a 1,000 times higher localization to the surface of the LPS-treated HUVEC cells compared to non-functionalized liposomes and more than 200 times higher localization compared to isotype-control functionalized liposomes as evidenced by confocal microscopy images under static culture conditions. This targeting was observed in both non-fixed and fixed HUVEC cells; however, non-fixed samples showed 66.37% higher localization of functionalized liposomes.

In summary, these findings demonstrate that functionalized liposomes can successfully target cells overexpressing VCAM-1 and might provide a potentially novel drug carrier for the treatment ofatherosclerosis. Current studies are focused on examining the efficiency of liposome targeting to HUVEC cells under shear flow.