Preparation and evaluation of poly(3‐hydroxybutyrate) microspheres containing bovine serum albumin for controlled release

The utility of the Poly(3‐hydroxybutyrate) (PHB) to encapsulate and control the release of bovine serum albumin (BSA), via microspheres, was investigated. Various preparing parameters, including polymer concentration in oil phase, emulsification concentration in external water phase, volume ratio of inner water phase to oil phase, and volume ratio of primary emulsion to external water phase were altered during the microspheres production. The effects of these changes on the morphological characteristics of the microspheres, size of the microspheres, drug loading, encapsulation efficiency, and drug release rates were examined. The diameter of the microspheres ranged from 6.9 to 20.3 μm and showed different degrees of porous structure depending on the different preparation parameters. The maximum and minimum BSA encapsulation efficiency within the polymeric microspheres were 69.8 and 7.5%, respectively, varying with preparation conditions. The controlled release characteristics of the microspheres for BSA were investigated in pH 7.4 media. The initial BSA burst release from 8.9 to 63.1% followed by constant slow release for 28 days was observed for BSA from BSA‐loaded microspheres and followed the Higuchi matrix model. So, the release behavior of microspheres showed the feasibility of BSA‐loaded microspheres as controlled release devices. Pristine BSA, pristine PHB microspheres, and BSA‐loaded microspheres were analyzed by Fourier transform infrared spectrophotometer, which indicated no interaction between BSA and PHB. Differential scanning calorimetry on BSA‐loaded microspheres indicated a molecular level dispersion of BSA in the microspheres. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008