Abstract: Ciprofloxacin loaded microspheres were prepared by spray drying technique, with bovine serum albumin as the natural biodegradable wall materials. The obtained microspheres, using aqueous system, were organic solvent-free. The diameters of the spherical microspheres were in the range of 1~5 μm. The drug entrapment of microspheres, formulated with different ciprofloxacin/albumin ratios as 1:1, 1:2 and 1:4, were 46.93%, 32.96% and 20.56% (n = 3). And the encapsulation efficiencies for ciprofloxacin during spray drying were higher than 90%. Thermal denaturation programs at different temperatures (100~120 °C) for different time intervals (3~6~12 h) were further processed to stabilize the spray-dried microspheres. The higher the extent for thermal denaturation, the slower the rate of ciprofloxacin released from microspheres in vitro. So the release rate of ciprofloxacin from microspheres can be controlled by modifing the conditions of thermal denaturation.

Key words: Spray drying, Microspheres, Ciprofloxacin, Thermal denaturation, Drug release in vitro