Tuesday, 24 May 2005

This presentation is part of: Polymeric Biomaterials Posters

Microspheres Prepared from Salicylate-Based Poly(anhydride-esters)

Brian A. Yeagy, Robert Schmeltzer, Almudena Prudencio, Kathryn E. Uhrich, and Thomas J. Cook. Rutgers, The State University of New Jersey, Piscataway, NJ

The aim of this work was to investigate how glass transition temperature (Tg) influenced polymer microsphere formation and degradation of three biodegradable salicylate-based poly(anhydride-esters) that differed by the linking group: poly (carboxyphenoxyhexanoate) (CPH), Tg = 57C; poly (carboxyphenoxyoctanoate) (CPO), Tg = 30C; and poly (carboxyphenoxydecanoate) (CPD), Tg = 27C. These poly(anhydride-esters) are unique in that salicylic acid, an effective anti-inflammatory, is incorporated directly within the polymer backbone. Microsphere delivery systems prepared from these polymers would have a higher percentage of drug loading than standard biodegradable polymer systems. Microspheres of CPH, CPO and CPD were prepared using a oil-in-water solvent evaporation method and characterized for particle size and morphology, in vitro release properties and residual poly(vinyl alcohol) (PVA) content. Spherical microspheres in the 1-10 μm size range were successfully prepared. The morphology of the microspheres determined by scanning electron microscopy (SEM) revealed that an extra washing step appears to increase aggregation as the Tg decreases; whereas only limited aggregation occurred in the polymer with the lowest Tg, CPD, in those not washed by centrifugation. An additional washing step also effectively removed residual PVA by >90%. The PVA content appeared to affect the drug release rates producing an 8 hr lag time and a 5% decrease in the amount of drug released over a 7 day period compared to microspheres washed free of PVA. Based on these results, poly(anhydride ester) microspheres can be prepared from several different polymers and have potential use as controlled drug delivery systems for anti-inflammatory conditions.

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