In vitro release of a water-soluble agent from low viscosity biodegradable, injectable oligomers

In vitro release of a water-soluble agent from low viscosity biodegradable, injectable oligomers
Received 14 June 2006; revised 14 September 2006; accepted 20 September 2006. Available online 28 September 2006.
Soroor Sharifpoora and Brian Amsden, a
European Journal of Pharmaceutics and Biopharmaceutics
Article in Press
ScienceDirect
Copyright ? 2006 Elsevier B.V. All rights reserved.
aDepartment of Chemical Engineering, Queen?s University, Kingston, Canada
Abstract
Low-molecular-weight poly(e-caprolactone-co-1,3-trimethylene carbonate) and poly(1,3-trimethylene carbonate) are potential vehicles for the regio-specific delivery of water-soluble agents. In this paper, the characteristics and the mechanism governing the in vitro release of a model water-soluble drug, vitamin B12, from these polymer vehicles were determined. The loading of vitamin B12 was kept to 1 w/w%. The oligomers examined ranged from amorphous, high viscosity to crystalline but low viscosity. The oligomers did not degrade appreciably in vitro. The total fraction of vitamin B12 released increased as the crystallinity of the oligomers decreased, reaching nearly total release only for the completely amorphous oligomers. The rate of release was fastest for the amorphous oligomers and dependent on their viscosity. Inclusion of a more osmotically active agent, trehalose, into the vitamin B12 particles through co-lyophilization resulted in enhanced total fraction released and a faster release rate. The results are consistent with an osmotically driven release mechanism.
Keywords: Vitamin B12; Biodegradable thermoplastic; Injectable; Local delivery; Trimethylene carbonate; e-Caprolactone; Osmotic release

Corresponding author. Department of Chemical Engineering, Queen?s University, 19 Division Street, Kingston, Ont., Canada K7L 3N6. Tel.: +1 613 533 3093; fax: +1 613 533 6637.
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