DSC Studies of Crystalline Morphology and Drug/Polymer Interactions in Bioerodible Polyanhydrides
 

Brianne Dziadul, Elizabeth Shen, Robert Piszczek, and Balaji Narasimhan
Rutgers University
Department of Chemical Engineering
School of Engineering, 98 Brett Rd
Piscataway, NJ 08854-8058
bdziadul@eden.rutgers.edu
(732) 445-0315
 

The goal of this research is to synthesize bioerodible copolymers and characterize their morphology to outline a systematic engineering approach to design drug/vaccine delivery systems. Polyanhydrides based on carboxy-phenoxy-hexane (CPH) and sebacic acid (SA) have been synthesized by polycondensation and copolymer compositions spanning the entire range have been targeted.  Certain copolymer compositions reveal microphase separation due to hydrophobicity effects.  Morphological characterization of the copolymer systems has been carried out using differential scanning calorimetry (DSC) and wide angle X-ray diffraction.  In addition, annealing studies using DSC have been used to calculate the lamellar thickness of the crystallites.  Our results indicate that as the CPH content in the copolymer increases, the overall degree of crystallinity decreases, while the lamellar thickness of the crystallites increases.  Furthermore, drug/polymer interactions have been quantified by DSC studies of drug/copolymer systems.  Our hypothesis is that drugs thermodynamically partition depending on their hydrophobicity when loaded into a heterogeneous polymer.  Both hydrophobic (p-nitroaniline) and hydrophilic (brilliant blue) model drugs have been loaded into eroding polyanhydrides to study the role of thermodynamic partitioning of the drug.  It is observed that in hydrophilic copolymers, the hydrophobic drug acts as a diluent, while the hydrophilic drug forms a homogeneous solution, thus providing preliminary evidence of drug partitioning.  Implications for designing vaccine delivery systems based on these polyanhydrides are discussed.