Supercritical solvent impregnation of poly(ɛ-caprolactone)/poly(oxyethylene-b-o...

• Author(s): Natu, Mădălina V. ; Gil, M. H. ; Sousa, Hermínio C. de
• Date: 2008
• Persistent ID: http://hdl.handle.net/10316/21651
• Origin: Estudo Geral - Universidade de Coimbra
• Subject(s): Supercritical solvent impregnation; Poly(ɛ-caprolactone) blends; Ophthalmic drug delivery systems
• Document Type: Article
• Language: English

Description

Poly(ɛ-caprolactone) blends were successfully impregnated with timolol maleate, an anti-glaucoma drug, using a supercritical solvent impregnation (SSI) technique. Supercritical fluid impregnation efficiency results suggested that the best impregnating conditions were obtained when a cosolvent was used and when specific drug–polymer interactions occurred as a consequence of different chemical structures due to polymer blending. Pressure can be either a favourable factor, when there is enough drug affinity for the polymers, or an unfavourable factor when weaker bonding is involved. In order to determine the relative hydrophilicity/hydrophobicity of the blends, contact angle analysis was performed, while crystallinity determination was also useful to understand the obtained release profiles. Drug loading, heterogeneous/homogeneous dispersion of drug inside the matrix, hydrophilicity, crystallinity, all seem to influence the obtained drug release rates. The “in vitro” release results suggested that a sustained drug release rate can be obtained by changing the SSI operational conditions and by modulating the composition of blends, as a mean to control crystallinity, hydrophilicity and drug affinity for the polymer matrix. After a first day burst release, all samples showed a sustained release profile (1.2–4 μg/(ml day), corresponding to a mass of 3–10 μg/day) which is between the therapeutic and toxic levels of timolol maleate, during a period of 1 month. These drug-loaded polymeric matrices can be a feasible alternative treatment modality for the conventional repeated daily administration of eye drops.