Preparation and characterization of chitosan microspheres as drug carrier for prednisolone sodium phosphate as model for anti-inflammatory drugs

Chitosan microspheres were prepared by a novel precipitation process using sodium sulfate as precipitant. Low, medium, and high molecular weight chitosan was chosen for the formulation of microspheres. The extent of precipitation was controlled by the concentration of sodium sulfate and monitored by turbidity measurement. The amount of sodium sulfate required for the preparation of the microspheres depended on the molecular weight of chitosan. The particle size was determined by photon correlation spectroscopy (PCS) and centrifugal sedimentation. The morphological characteristics were examined using a scanning electron microscope (SEM). The surface charge was measured by microelectrophoresis. After preparation the loading property with various anti-inflammatory drugs was investigated using spectrophotometry. The influence of surface adsorption on the drug modification was controlled by differential scanning calorimetry (DSC). Drug liberation was tested in vitro using side-by-side diffusion cells with a dialysis membrane made of cellulose acetate. The highest loading (up to 30.5% relative to the polymer mass) was achieved with prednisolone sodium phosphate (PSP). The adsorbed drug was present in an amorphous form. The drug release from the microspheres was dependent on the drug-polymer ratio.