Poster Presenter

Synthesis, Characterization and in vitro Mechanistic Release Study from Photocrosslinked Biodegradable
Noor Al-Salimy, Mariam Khaja, Nahla Jabr and Husam M. Younes
Qatar

Purpose: To report on the synthesis and characterization of a novel family of ultraviolet (UV) crosslinked biodegradable poly (alkylene tartarate) (PAT) elastomers and to study the effect of particle size, and polymer properties on the in vitro release of the water soluble drug, pilocarpine nitrate (PN) from this newly synthesized elastomer.

Methods: An aliphatic saturated polyester prepolymer was first synthesized via polycondensation reaction of L-tartaric acid with 1, 8 Octanediol at 140 ^oC for two hours under vacuum to form PAT prepolymer. The purified prepolymer was then reacted with acryloyl chloride to add vinyl groups at the prepolymer chains terminals. The pure acrylated poly (alkylene tartarate) (APAT) prepolymer was subjected to 5 minutes of UV crosslinking in the presence of biocompatible UV initiator to form the elastomer. The polymers prepared were characterized using chemical, thermal, and molecular weight analysis. For in vitro release studies, PN powder of three different particle sizes was mixed with APAT to achieve 10-15 % v/v loading. The mix was poured into Teflon tabular moulds and subjected to photocrosslinking for 5 minutes. Tablets prepared were used to conduct release studies in phosphate buffer saline of pH = 7.4 at 37 ^oC over 30 days period. Released PN was detected using UV analysis and percentage released of PN over one month period was plotted versus time.

Results: 1H-NMR and infrared analysis confirmed purity and formation of ester bonds in the polymer backbone. Thermal analysis showed that the prepolymer is of semicrystalline nature with a corresponding glass transition temperature (Tg) of -16 ^oC and a melting endotherm at 57 ^oC. Molecular weight analysis reported a weight average molecular weight of 1250 daltons. The final photocrosslinked PAT elastomers were reported to have Tg ranges from -10 to 0 ^oC. The release profiles showed that contrary to previous studies, tablets formulated with the same volumetric loading and smaller drug particle size released drug faster than tablets with a larger particle size. It was also shown that osmotic release was the predominant mechanism governing the linear release pattern of PN from those new PAT elastomers. The elastomers also followed bulk degradation mechanism with no significant weight loss during the studied period.

Conclusions: Novel biodegradable, photocrosslinked PAT elastomers were successfully prepared and characterized. Release studies demonstrated the suitability of this new family of polymers for implantable sustained release delivery of hydrophilic drugs.

Acknowledgements: Noor Al-Salimy and Mariam Khaja are recipients of Undergraduate Research Experience Program (UREP) award. This work was partially supported by UREP/Qatar Foundation.