POE and POE-PEG-POE triblock copolymeric microspheres for controlled protein delivery

Abstract

A model protein, BSA, was encapsulated inside POE, POE-PEG-POE and POE/PEG blend microspheres using W/O/W double emulsion method. Our results demonstrate that attaching a PEG block to POE polymer backbone yielded a more stable first emulsion (W/O) and a higher BSA encapsulation efficiency (EE). PEG content and microspheresa?? preparation conditions (BSA loading, polymer concentration, PVA concentration in the external aqueous phase) did not have significant influence on BSA EE due to the stable first emulsion. Protein release from the triblock copolymeric microspheres showed a biphasic pattern at low loading levels. POE-PEG(20%)-POE might possess a better compatibility between the POE and PEG blocks resulting in a relatively constant polydispersity index, molecular weight and a sustained weight loss. Protein release from POE-PEG(20%)-POE microspheres was able to sustain for nearly 20 days. We also found that PEG molecular weight did not have significant effect on release properties of BSA-loaded POE-PEG-POE microspheres. BSA release was much faster from POE-PEG-POE triblock copolymers with a more flexible POE composition. Blending of PEG with POE presents a powerful alternative, which is superior in terms of simplicity and low cost compared to copolymerization. By varying the PEG molecular weight and content, particle size distribution, surface and internal morphologies of the resultant microspheres could be changed, resulting in different BSA release profiles.