Preparation and Characterization of Gentamicin Sulfate Loaded Poly(L-lactide-co-glycolide) Microspheres for the Treatment of Osteomyelitis

Controlled gentamicin sulfate (GS) releasing microspheres manufactured from biodegradable poly(L-lactide-co-glycolide) (PLGA, 75:25 by mole ratio) were prepared with an oil/oil solvent evaporation method for the treatment of osteomyelitis. The microspheres of different size (30∼350μm) were obtained with varying the experimental conditions, and the shape of microspheres was smooth and spherical. The efficiency of encapsulation was over 81%. The effects of the preparation conditions on the size of microspheres have been investigated. In vitro release studies showed that different release patterns and release rates could be achieved by simply modifying factors in the preparation conditions such as polymer concentration, surfactant concentration, molecular weight of PLGA and initial amount of loaded drug. PLGA microspheres with 20% of initial drug loading, 0.2% (w/w) of surfactant concentration and 50% (w/v) of PLGA concentration, were free from initial burst effect and a near-zero order sustained release was observed for over 60 days. Mechanisms of the prolonged sustained release from the larger GS/PLGA microspheres with over 100 μm medium size have been proposed.