In vitro degradation study of polyester microspheres by a new HPLC method for monomer release determination

Citation
P. Giunchedi et al., In vitro degradation study of polyester microspheres by a new HPLC method for monomer release determination, J CONTR REL, 56(1-3), 1998, pp. 53-62
Citations number
26
Categorie Soggetti
Pharmacology & Toxicology
Journal title
JOURNAL OF CONTROLLED RELEASE
ISSN journal
01683659 → ACNP
Volume
56
Issue
1-3
Year of publication
1998
Pages
53 - 62
Database
ISI
SICI code
0168-3659(199812)56:1-3<53:IVDSOP>2.0.ZU;2-G
Abstract
Biodegradable polyesters have increasing importance as materials used for t he preparation of microspheres. The knowledge of their degradation process is important to prepare microparticulate delivery systems with suitable dru g release rates. In this work an in vitro degradation study of empty and dr ug loaded microspheres is described. Three different polyesters were used: two poly-D,L-lactides of different molecular weight and a poly-D,L-lactide- co-glycolide (50:50). Diazepam has been chosen as the model drug. Solvent e vaporation and spray-drying were used as preparation methods. To study the polymer degradation process, a new HPLC method is proposed for the direct a nd (in the case of the copolymer) simultaneous determination of the monomer (s): lactic acid (LA) and glycolic acid (GA). SEM and particle size analysi s highlight the different characteristics of the particles, depending on th eir preparation method: spray-dried spheres result to be always smaller wit h respect to particles obtained by solvent evaporation. The results obtaine d indicate in particular that: the preparation methods play an important ro le in determining the degradation behaviour of microspheres, as unloaded sp ray-dried particles are characterized by a higher monomer release fate with respect to microspheres obtained by solvent evaporation; PLGA spheres degr ade faster than PDLLA microparticles, according to the higher hydrophilicit y of the copolymer; the two monomers are released at a different rate in th e case of PLGA (faster for GA, slower for LA); the presence of diazepam inc reases the polymer degradation rate, with respect to empty particles. (C) 1 998 Elsevier Science BN. All rights reserved.