Synthesis of methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) diblock copolymers and release behavior of albumin for implantable protein carriers

MPEG-PCL diblock copolymers consisting of methoxy poly(ethylene glycol) (MPEG) and ε-caprolactone (CL) as drug carriers were synthesized by ring-opening polymerization. MPEG-PCL diblock copolymers were characterized by X-ray diffraction and differential scanning calorimetry. After freeze milling of block copolymers and albumin bovine-fluorescein isothiocyanate (FITC-BSA) as model protein, the wafers loaded FITC-BSA were fabricated by direct compression method. The release profiles of FITC-BSA were examined using pH 7.4 PBS for 14 days at 37°C. The release amount was determined by fluorescence intensity by using the fluorescence spectrophotometer. The morphological change of wafers was observed by digital camera and scanning electron microscope. The release rate and initial burst of BSA increased with increasing PEG molecular weights and decreasing PCL molecular weights in the segments of MPEG-PCL diblock copolymers.