Characterization andin vitrodegradation of salicylate-derived poly(anhydride-ester microspheres)

Abstract

The aim of this study was to investigate how glass transition temperature (Tg) influenced polymer microsphere formation and degradation of three chemically, similar novel salicylatebased poly(anhydride-esters): poly[1,6-bis(o-carboxyphenoxy)hexanoate] (CPH), Tg = 59 degrees C; poly[1,8-bis(o-carboxyphenoxy)octanoate] (CPO), Tg = 30 degrees C; and poly[1,10-bis(ocarboxyphenoxy) decanoate] (CPD), Tg = 27 degrees C. Microspheres of these polymers were prepared using a modified oil-in-water solvent evaporation method and processed by either resuspension or washed by centrifugation. 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. Residual polyvinyl alcohol apparently affected the drug release rates from the microspheres by a stabilization process that produced an 8 h lag time and a 5% decrease in the amount of drug released over a 7 day period compared to microspheres washed free of PVA. These results demonstrate that salicylate-based poly(anhydride-esters) with sufficiently high Tgs, can be processed into microspheres that release salicylate over a time period amenable for drug delivery applications.

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“…These polymers have been found to have T g s lower than physiological temperatures (12–34 °C),354, 356, 357 and are often copolymerized with traditional aromatic diacid monomers to improve mechanical properties 356, 358. Salicylic acid‐derived poly(anhydride ester)s and their composites have been fabricated into particles,357, 359 fibers,358 and films355, 356, 360, 361 for biomedical application. They have been used in the prevention of biofilm formation,360, 361 the prevention of bone resorption,356, 359 and the creation of a local anti‐inflammatory effect 356, 360…”

Stability of a salicylate-based poly(anhydride-ester) to electron beam and gamma radiation

“…The physicochemical properties of such polyanhydrides have been investigated over the last decade [5–14]. The ability to formulate these polymers into different geometries such as powders [6], disks [5, 9, 15], fibers [7], microspheres [10, 16], etc. contributes to their wide scope of applications.…”

Current literature in diabetes

“…Salicylic acid (SA)‐based poly(anhydride‐esters) ( 1 ) have been proven effective for controlling inflammation,17, 18 promoting bone growth,17, 19, 20 and preventing biofilm formation 18, 21. The polymers can easily be manipulated into different geometries including powders, fibers,22 microspheres,23 disks,9 films, and cardiac stents 24. Most of these polymers prepared for biomaterials indications have been designed to degrade within weeks to months 17, 18, 20, 24, 25…”