Liposomal drug delivery to the eye and lungs: a preliminary electron microscopy study

Colloidal gold was used as an electron-dense marker for multilamellar vesicles to study the mechanism of liposome drug delivery to the eye and lung. A gold labelled multilamellar vesicle could be seen in the conjunctiva but there was no evidence of vesicles adsorbed to the epithelial surface of cornea or conjunctiva. In the lung, a free gold particle was isolated in type 1 epithelial cells and many vesicular structures were observed in the alveolar spaces which were not gold labelled. Experiments performed so far indicate that adsorption and not endocytosis was the major mechanism of uptake of drug or marker for multilamellar vesicles except for conjunctiva.