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D. Barbosa-Alfaro, P. Checa-Casalengua, I. Bravo-Osuna, B. A. Tucker, M. J. Young, R. Herrero-Vanrell; Sterilization of GDNF-PLGA Microparticles for Intraocular Administration. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5979.
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Intraocular administration of glial-cell-line-derived neurotrophic factor (GDNF) is an interesting neuroprotective strategy in the treatment of retinal degeneration and glaucoma. All formulations destined to the intraocular route must be sterilized before administration, so the stability of the active compounds must be also guaranteed. The aim of this work was to evaluate the effect of an sterilization dose (25 kGy) of gamma radiation on the poly-(lactic-co-glycolic acid) (PLGA) microspheres loaded with GDNF.Materials: PLGA 50:50 (Resomer® 503) from Boehringer Ingelheim and GDNF from R&D.
MPs were prepared by the O/W emulsion-solvent evaporation technique. The O-phase consisted of 1ml of PLGA/CH2Cl2 solution 20%w/v in which 20µg of GDNF were added. Once prepared, the O-phase was emulsified in 5ml PVA 2%w/v at 5,000rpm for 1min. After 3h of hardening in 100ml PVA 0.1%w/v, MPs were recovered, washed with distilled water and frozen in MeOH/ice mixture. MPs were subsequently freeze-dried for 24h, and stored in dry conditions at 4ºC until use. The formulation was sterilized by using 60Co as the radiation source in the γ-radiation unit at Aragogamma S.A. (Barcelona, Spain). A γ-radiation dose of 25 kGy was employed to ensure effective sterilization. In vitro release studies were carried out for 9 weeks by suspending the MPs in 1.5ml of a release media composed by PBS (pH 7.4) isotonized with NaCl, 1%BSA and 0.02% Sodium Azide. At pre-set times (1h, 24h and once a week for 9 weeks) the release medium was collected and GDNF levels quantified using ELISA.
MP size distribution was in the 2-40µm range. A different initial burst effect (24h release assay) was observed between non-sterilized and sterilized MPs with values of 13.4±1.0ngGDNF/mgMPs and 10.3±1.1ngGDNF/mgMP respectively. Following initial burst release, 38.9±5.2pgGDNF/mgMPs/day (non-sterilized) and 33.7±1.3pgGDNF/mgMPs/day (sterilized) was detected for the 9 weeks of release test.
γ-radiation is a viable approach for sterilization of GDNF-PLGA MPs prior to intravitreal administration.
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