LIPOSOME UPTAKE BY HUMAN RETINAL-PIGMENT EPITHELIAL-CELLS IN CULTURE

Purpose. To examine the internalization of liposomes containing variou s phospholipids by human retinal pigment epithelial (RPE) cells in cul ture. The internalization was compared to that exhibited by macrophage s and fibroblast cells. Methods. The uptake into cells was monitored b y using a nondegradable, radioactive cholesterol-hexadecyl ether deriv ative and a pH-sensitive, water-soluble fluorescent dye. Variables tes ted to determine their effect on uptake included time, phospholipid co ncentration, the presence or absence of serum in medium and the presen ce or absence of cholesterol in the liposome bilayer. The most avidly ingested liposome was tested to determine its ability to deliver a lip osome-dependent drug. Results. Liposome uptake was time and concentrat ion dependent. Uptake for RPE was maximal in serum-free media, while t he opposite was true for the other cells tested. Cell survival followi ng exposure to fluoroorotic acid-containing liposomes correlated with the radioactive cholesterol-hexadecyl ether and fluorescent dye uptake data. Conclusions. No single liposome carrier or set of conditions te sted appeared to be optimum for the delivery of a cytotoxic agent to t hese three cell types. This bears consideration when designing strateg ies for the prevention and treatment of intraocular proliferative dise ases such as proliferative vitreoretinopathy (PVR).