Microparticles as Drug Delivery Systems for the Back of the Eye

Abstract

Treatment of vitreoretinal disorders often include repeated intraocular injections to achieve effective levels of the active substance in the target site. Intraocular drug delivery systems (IDDS) are considered an alternative to multiple injections as they release the encapsulated drug over long periods of time. Among them, biodegradable microparticles are very useful for intraocular administration because they can be injected as a conventional suspension without surgical procedures, to release the active substance over weeks or months. Microparticles can be loaded with different drugs useful to treat different pathologies affecting the back of the eye such as proliferative vitreoretinopathy, age-related macular degeneration, cytomegalovirus retinitis, diabetic retinopathy, endophthalmitis, glaucoma, herpes infection, macular edema, retinal vein occlusion, retinitis pigmentosa, and uveitis. Administration of microparticles can be performed by periocular, intravitreal, sub-retinal, or other intraocular routes to treat vitreoretinal disorders. Generally, microparticles are loaded with one active substance. Recently, biodegradable microparticles loaded with more than one drug ("combo microparticles") are being developed. Moreover, biodegradable microspheres are potential tools for retinal repair in combination with retinal progenitor cells.