Diffusion of camptothecin immobilized with cationic surfactant into agarose hydrogel containing anionic carrageenan

Abstract Camptothecin (CPT) is a hydrophobic antitumor drug. Controlled release of CPT from hydrogel has not been satisfactorily achieved because of its poor compatibility and weak interaction with a hydrophilic hydrogel matrix. A new approach has been attempted in this work to solve these problems. In our approach, CPT was first solubilized in a micellar solution of cetyltrimethylammonium bromide (CTAB), a cationic surfactant. It was found that the solubility of CPT could be enhanced by CTAB (10 mM) to 0.17 mg/mL, which is 127 times higher than that in pure water, providing a great feasibility of drug loading. The micellar drug solution of CTAB‐CPT was subsequently used to prepare agarose hydrogels containing a small content (≤ 0.3 wt %) of κ‐carrageenan, an anionic water‐soluble polysaccharide. The release of CPT from so fabricated hydrogel‐surfactant systems has been investigated by varying the content of κ‐carrageenan in the hydrogel. It was observed that the presence of κ‐carrageenan in the hydrogel system resulted in a significant decrease in the release rate of the drug. This effect was ascribed to the ionic interaction between the positively charged surfactant micelles and the negatively charged κ‐carrageenan. The release profiles were fitted to two mathematic models of diffusion and the diffusion coefficients of the drug were obtained as a function of κ‐carrageenan content. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007