A physicochemical study of the morphology of progesterone‐loaded microspheres fabricated from poly(D,L‐lactide‐co‐glycolide)

Abstract

Progesterone-loaded microspheres are fabricated by a solvent evaporation process from a poly(D,L-lactide-co-glycolide) (85/15 PLG) and from alpha-progesterone. Methylene chloride is used as solvent and polyvinyl alcohol and methylcellulose are used as surfactants. The microspheres are characterized by scanning electron microscopy, differential scanning calorimetry, and x-ray powder diagrams. Our study shows that the morphology and the thermal behavior of PLG microspheres can vary significantly with progesterone loading and sample thermal history. Below and at 16.5% loading the microspheres exhibit a smooth outer surface. Above 23% loading, the surface becomes rough, embedded by copolymer particles or well-defined crystals. Pores and cracks can also be observed. Below 35% the progesterone is molecularly dispersed. At 35% and above crystal domains of the steroid appear and two crystalline forms are found: alpha- and beta-progesterone. The physical state of progesterone and the nature of its crystal domains dispersed in the PLG matrix can change during storage. Also a progressive development of an endothermic peak at the Tg event of the copolymer is observed during storage. No well defined relationship of peak size to progesterone loading can be shown.

Induction of angiogenesis in tissue-engineered scaffolds designed for bone repair: A combined gene therapy–cell transplantation approach

“…There remain, however, three major challenges in factor delivery: (i) the sensitivity of growth factors to thermal processing and exposure to chemical solvents, (ii) the short half-life of growth factors in vivo (14), and (iii) the limited control over the spatial and temporal distribution of growth factors throughout the scaffolds.…”

Indomethacin-Dipalmitoylphosphatidylcholine Interaction. A Calorimetric Study of Drug Release from Poly(Lactide-co-glycolide) Microspheres into Multilamellar Vesicles

“…The exothermic process could be caused by the fraction of drug dispersed in microspheres as "amorphous," which can crystallize during the heating (exothermic peak) before melting (endothermic peak). The melting process is observed to be at a lower temperature with respect to the pure drug, probably because of the interaction between the drug and polymer (Bodmeier et al, 1989;Izumikawa et al 1991;Rosilio et al 1991). These results show that the amount of the drug loaded in the matrix system influences the nature of the dispersion: a lower indomethacin content (10.9%) leads to formation of a drug solid solution in the polymeric matrix, whereas a higher drug content (34.1%) leads to amorphous drug dispersion in the polymer.…”

“…Both morphological properties and amount of drug loaded affect drug release from microspheres (Le Corre et al 1994;Pradhan and Vasavada 1994;Rosilio et al 1991).…”

Biocompatibility of degradable polymers for tissue engineering

“…They concluded that due to the biocompatibility of the copolymer and the fl exibility in terms of the release kinetics, it has been approved for human use and is being investigated for mucosal immunisation because of its ability to protect the vaccine and enhance adsorption into associated tissues. In another study, progesterone was loaded in microspheres of poly(dl-lactide-co-glycolide) and it was found that variations in the progesterone loading affected the structural and thermal properties (Rosilio et al 1991).…”