OPTIMIZATION OF POLYLACTIDE MICROSPHERE COMPOSITION FOR CONTROLLED PROLONGED RELEASE OF BETAMETHASONE ACETATE
Abstract
The aim of this study is to optimize the composition of PLGA microspheres to increase BA loading and control the release rate. The solid-in-oil-in-water (S/O/W) multiple emulsion method and the oil-in-water (O/W) emulsification method with the addition of benzyl alcohol (BA) were used to increase BA loading. The concentration of BA in the organic phase was increased from 30 to 50 mg/mL. Microspheres were prepared based on PLGA (75:25, 42 kDa, carboxyl end groups, Novokhim LLC, Tomsk). As a result, both approaches allowed increasing BA loading from 4% to 30%. At the same time, in the case of the S/O/W method, the microsphere size increased from 53±13 мm to 85±16 мm, whereas in the case of the O/W method with the addition of benzyl alcohol, the microsphere size did not change. In addition, the effect of polymer composition (molecular weight 42 and 58 kDa, L/G ratio 50/50 and 75/25, end group COOH and COOR) on microsphere characteristics and the release rate of BA was investigated. All obtained microspheres had a size of 57–65 мm and a BA loading of 25 to 32%. It was noted that an increase in PLGA molecular weight from 42 to 58 kDa and the replacement of the COOH group with the COOR ester group led to a decrease in the BA release rate: the difference in release reached 44% (56% vs 12%) by day 65. However, the most uniform BA release rate was achieved from microspheres with the following composition: 58 kDa, L/G 75/25, -COOH group. Over 60 days, about 50% of BA was released. Thus, the optimized PLGA microsphere composition (58 kDa, L/G 75/25, -COOH group) with a BA loading of 30% and a size of 59±19 мm allowed controlled release of BA over 60 days. The obtained microspheres may open up the possibility for the development of a prototype long-acting form.
References
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