IN-VITRO PHAGOCYTOSIS OF POLYLACTIDE MICROSPHERES BY RETINAL-PIGMENT EPITHELIAL-CELLS AND INTRACELLULAR DRUG-RELEASE

We investigated phagocytosis of biodegradable microspheres containing a drug by retinal pigment epithelial (RPE) cells and drug release with in the cells to evaluate the potential usefulness of microspheres for intracellular drug delivery. The biodegradable polymers used were L-la ctic acid, and DL-lactic acid with different molecular weights or the copolymers of different monomer compositions. The microspheres contain ing a non-bioactive fluorescent dye (rhodamine 6GX) as a model drug, w ere prepared by a solvent evaporation method. The in vitro release of the dye from the microspheres was examined. Phagocytosis of the micros pheres by RPE cells was conducted to evaluate the extent of phagocytos is by phase-contrast microscopy and transmission electron microscopy. The RPE cells ingesting the microspheres at different stages were exam ined by fluorescent microscopy to estimate the intracellular release o f the dye. The dye was released with time from every microsphere and t he release was controlled by changing the type of polymers constitutin g microspheres. The microspheres containing the dye were phagocytosed by RPE cells and the dye was released intracellularly with time. The p resent study indicates that the drug incorporated in the microspheres was delivered into RPE cells by way of phagocytosis and released withi n the cells. It is concluded that this microsphere system is a promisi ng delivery form capable of drug targeting to RPE cells.