Characterization of biodegradable poly( d,l-lactide-co-glycolide) polymers and microspheres

Characterization of biodegradable polymers used for controlled drug delivery is essential to ensure reproducibility of in vitro and in vivo performance. Selected characterization techniques established for poly( d,l-lactide-co-glycolide) (PLGA) copolymers included DSC to analyse thermal behavior, 13C-NMR to determine exact comonomer ratios and comonomer sequencing, cloud point titration to establish solubility, SEC to monitor molecular weight averages and polydispersity, SEM to observe surface morphology, BET gas adsorption to analyse surface area, tapped bulk density measurements to suggest internal pore structure and porosity and finally in vitro degradation to analyse degradation times and profiles. Comonomer ratios of 50:50 PLGAs were found to be closer to stated values for Boehringer Ingelheim polymers than for polymers from two other suppliers. Implementing such a characterization program for biodegradable polymers ensures the production of reproducible and reliable controlled drug delivery systems.