SYNTHESIS AND CHARACTERIZATION OF A NEW BIODEGRADABLE SEMISOLID POLY(ORTHO ESTER) FOR DRUG-DELIVERY SYSTEMS

Since the late 1970s, three families of poly(ortho esters) (POE) were synthesized to provide bioerodible carriers for drug delivery devices. The most recent POE is a semi-solid polymer with a viscous behavior a t room temperature. Polymer synthesis by a transesterification reactio n between a triol and a trialkyl orthoester is described. The structur e of the polymer was confirmed by conventional methods such as H-1-NMR , C-13-NMR and FT-IR. Information concerning average molecular weight and intrinsic viscosity was obtained respectively by GPC and viscosime try. Residual solvents in the polymer were determined using gas chroma tography. The chromatographic conditions were optimized to enable the quantification of the solvents in concentrations of a few percent. The mechanical behavior of the semi-solid POE was determined by rheometri c measurements. Hydrolysis of the polymer leads to the formation of th e original triol and the carboxylic acid derived from the trialkyl ort hoester used in the transesterification step. No toxicological problem s associated with these compounds are anticipated.