tailieunhanh - Intraocular Drug DelIvery - part 6

Biodegradable Systems 177 Figure 3 Cumulative release GCV from the scleral plugs of PLA-70,000 and PLA-5000 (whose content ratio was 80:20) containing 25% of GCV. The values shown are mean Æ SD. The duration of GCV release was prolonged further compared with the plug made of PLGA (75/25)-121,000. Abbreviations: GCV, ganciclovir; PLA, polylactic acid; PLGA, polyglycolic acid. Source: From Ref. 4. weight: 5000) at weight ratios of 80/20. These plugs included 25% GCV. The highmolecular-weight PLA may play a substantial role in the framework of the device and restrict the degradation rate of the low-molecular-weight PLA. Also the lowmolecular-weight PLA may regulate drug. | Biodegradable Systems 177 Figure 3 Cumulative release GCV from the scleral plugs of PLA-70 000 and PLA-5000 whose content ratio was 80 20 containing 25 of GCV. The values shown are mean SD. The duration of GCV release was prolonged further compared with the plug made of PLGA 75 25 -121 000. Abbreviations GCV ganciclovir PLA polylactic acid PLGA polyglycolic acid. Source From Ref. 4. weight 5000 at weight ratios of 80 20. These plugs included 25 GCV. The high-molecular-weight PLA may play a substantial role in the framework of the device and restrict the degradation rate of the low-molecular-weight PLA. Also the low-molecular-weight PLA may regulate drug release by slowing pore formation during the diffusional phase. The degradation rate of other biodegradable devices such as microspheres and intrascleral implants is also controlled in a similar manner. Drug Delivery Systems General Overview Several different intraocular drug delivery systems using biodegradable polymers such as microspheres 5-9 intraocular implants 10-13 scleral plugs 3 4 14-22 and intrascleral implants 23 have been developed. Moritera et al. 5 first reported an intravitreal drug delivery system using biodegradable polymer microspheres. PLA microspheres containing doxorubicin hydrochloride 6 and PLGA microspheres containing retinoic acid 7 have been reported for the treatment of proliferative vitreoretinopathy PVR . GCV-loaded PLGA microspheres have been developed using a new oil-in-oil emulsion technique with fluorosilicone 8 . Interestingly after intravitreal injection of PLA nanoparticles with the mean size of 310 nm nanoparticles transversed the retina and reached the retinal pigment epithelium 9 . Targeted drug delivery to the retina and retinal pigment epithelium could be feasible using PLA nanoparticles. Surodex1 Oculex Pharmaceuticals Inc. is a PLGA rod containing dexamethasone which is implanted at cataract surgery for treatment of postsurgical inflammation 10 . In a multicenter randomized