The potential of using biodegradable microspheres in retinal diseases and other intraocular pathologies

Abstract

Pathologies affecting the posterior segment of the eye are one of the major causes of blindness in developed countries and are becoming more prevalent due to the increase in society longevity. Successful therapy of diseases affecting the back of the eye requires effective concentrations of the active substance maintained during a long period of time in the intraocular target site. Treatment of vitreoretinal diseases often include repeated intravitreous injections that are associated with adverse effects. Local administration of biodegradable microspheres offers an excellent alternative to multiple administrations, as they are able to deliver the therapeutic molecule in a controlled fashion. Furthermore, injection of microparticles is performed without the need for surgical procedures. As most of the retinal diseases are multifactorial, microspheres result especially promising because they can be loaded with more than one active substance and complemented with the inclusion of additives with pharmacological properties. Personalized therapy can be easily achieved by changing the amount of administered microspheres. Contrary to non-biodegradable devices, biodegradable PLA and PLGA microspheres disappear from the site of administration after delivering the drug. Furthermore, microspheres prepared from these mentioned biomaterials are well tolerated after periocular and intravitreal injections in animals and humans. After injection, PLA and PLGA microspheres suffer aggregation behaving like an implant. Biodegradable microspheres are potential tools in regenerative medicine for retinal repair. According to the reported results, presumably a variety of microparticulate formulations for different ophthalmic therapeutic uses will be available in the clinical practice in the near future.

Processing and size range separation of pristine and magnetic poly( l -lactic acid) based microspheres for biomedical applications

“…PLLA microspheres can be produced by several physicochemical methods, including solvent extraction/evaporation from an emulsion, aggregation by pH adjustment or heat, coacervation (phase separation), interfacial polymerization, ionic gelation, electrospray and spray drying, among other techniques [2,[14][15][16]. Emulsionsolvent evaporation method is perhaps the most commonly used one [17].…”

“…The potential for application of neat or composite PLLA microspheres has been demonstrated in the treatment of ocular pathologies, namely in regenerative medicine for retinal repair or related intraocular pathologies [14] and drug delivery [7,[22][23][24].…”

Controlled and Extended Release of a Model Protein from a Microsphere-Hydrogel Drug Delivery System

“…Thus, consideration must be made to localize microspheres to prevent their movement as separate units in the vitreous. 11 We have achieved this by suspending the microspheres within an injectable hydrogel.…”

From Single Microparticles to Microfluidic Emulsification: Fundamental Properties (Solubility, Density, Phase Separation) from Micropipette Manipulation of Solvent, Drug and Polymer Microspheres

“…These formulations can deliver high added value in difficult and chronic treatments, by providing therapeutic quantities of an API for months of treatment in one injection. Especially retinal diseases and other intraocular pathologies can effectively be treated by using biodegradable microspheres [40]. One of the most well-known controlled-release microsphere systems is the commercially available Lupron depot [41], a synthetic gonadotropin-releasing hormone used in men to treat the symptoms of prostate cancer, and in women to treat symptoms of endometriosis or uterine fibroids.…”