A NOVEL SKELETAL DRUG-DELIVERY SYSTEM USING SELF-SETTING CALCIUM-PHOSPHATE CEMENT .3. PHYSICOCHEMICAL PROPERTIES AND DRUG-RELEASE RATE OF BOVINE INSULIN AND BOVINE ALBUMIN

A novel drug-deliver device based on a self-setting bioactive cement f ormed from tetracalcium phosphate and dicalcium phosphate has been dev eloped and tested in vitro using bovine insulin and bovine albumin as model polypeptide drugs. Equimolar mixtures of the calcium phosphate p owders containing bovine insulin and bovine albumin were transformed i nto a hydroxyapatite cement after being mixed with a dilute phosphoric acid solution. X-ray diffraction and FT-IR spectra results suggested that the raw materials transformed into lower crystallinity of hydroxy apatite as it hardened. In vitro drug release from cement pellets into a 0.1 mol/L phosphate buffer at pH 7.40 and 37 degrees C continued fo r more than 3 weeks. Release from the drug-loaded cements followed the Higuchi model equation.