Externally triggered release of dye and drugs from liposomes into the eye. An in vitro and in vivo study.

Temperature-sensitive liposomes were made with carboxyfluorescein (CF) (100 mM) entrapped in the aqueous compartment. This liposome dye system was used in vitro to evaluate the feasibility of using microwaves as a triggering mechanism for the release of drugs in the anterior chamber of the eye. The in vitro study demonstrated that CF can be released from liposomes in response to a localized temperature rise induced by microwave irradiation. In an in vivo study in rabbits, CF and the antineoplastic agent, cytosine arabinoside, were administered intravenously and selectively released by increasing the temperature of the ciliary body with microwaves. In the eyes receiving liposome-encapsulated dye, the average concentration of CF in the anterior chamber of the heated eyes was 8.0 times higher than in the contralateral unheated control eyes. In the eyes receiving liposome-encapsulated drug, the average concentration of cytosine arabinoside in the aqueous of the heated eyes was 4.1 times higher than the concentration in the contralateral unheated control eyes. The importance of this finding lies in the potential for a new method of targeting the delivery of dyes and drugs to specific sites in the eye.