Release characteristics of three model drugs from chitosan/cellulose acetate multimicrospheres

Chitosan/cellulose acetate multimicrospheres (CCAM) loaded different model drugs were prepared by the method of w/o/w emulsion. Model drugs with different hydrophilicity were selected to investigate the delivery system, such as hydrophilic ranitidine hydrochloride (RT), amphoteric acetaminophen (ACP) and hydrophobic 6-mercaptopurine (6-MP). The size of CCAM loaded RT or ACP were almost the same of 200-280 mu m and the size of CCAM loaded 6-MP was only 50-80 mu m. With the increasing of hydrophobicity of drug, the holes in the appearance of microspheres became smaller and the loading efficiency increased. The loading efficiency of 6-MP was more than 30% whereas that of RT and ACP was only 10%. The CCAM system had good effect on the controlled release in vitro of all model drugs of different hydrophobicity. However, the release rate was affected by the hydrophobicity of model drug. It became slower with the increasing of hydrophobicity of drugs. The highest release rate was almost 60% during 48 h which was for the hydrophilic drug of RT and the release rate of hydrophobic drug (6-MP) was not more than 30% in the same time. (c) 2006 Elsevier B.V. All rights reserved.