Preparation and degradation behavior of polyanhydrides nanoparticles

Polyanhydrides have been used in many drug delivery systems because of their biodegradability and biocompatibility. Their degradation pattern of surface erosion made them suitable for stable drug release applications. However, in nanoparticle systems, this degradation pattern may not hold, and the drug release kinetics will be different also. In this study, copolymers of 1,3-bis(p-carboxyphenoxy)propane (CPP) and sebacic acid (SA) were synthesized to investigate the different degradation patterns of disk and nanoparticle forms of polyanhydride, in addition to the study of the method of preparation of nanoparticles from these copolymers. By using oil-in-water emulsion and poly(vinyl alcohol) (PVA) as emulsifier, nanoparticles of the size 200-500 nm were prepared. The size of the particles can be controlled by varying polymer concentration or PVA concentration, but different SA:CPP ratio did not affect the particle size significantly. Degradation was followed by detecting the amount of monomers released to the medium. It was found that CPP and SA were released at approximately the same rate from nanoparticles; while in disk form, SA was released much faster than CPP. It was found that contrary to general trend in disks, higher CPP content, a more hydrophobic component than SA, in the copolymer actually accelerated the degradation of nanoparticles.