Liposomes for Retina and Posterior Segment Disease
Liposomes are bilayer vesicles composed of phospholipids, which can contain the non-lipophilic drugs to increase its bioavailability and to enter the posterior segment of the eye. These liposomes can be formulated in different sizes via these four basic steps: drying lipids from the organic solvent, dispersing the lipid within an aqueous media, purification, and analyzing the product. Majority of the liposome formulations are generally composed of poly(ethylene glycol) (PEG)-modified lipids, which have been proven to increase circulation time. This drug delivery method renders both active and passive mechanism, which are specific to the targeted area. Liposomes act as barriers when they come in contact with ocular surfaces and protect therapeutic agents from the metabolic enzymes found at the tear junction. However, there are some challenges that still have to be tackled, for instance, sterilization, short shelf life, and also other unknown consequences of their long-term in vivo use. Even with the above issues, liposomes offer a sustained drug release, which reduces the frequency of the intravitreal injections and thus their side effects.
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