Preparation, characterization and pharmaceutical uses of biodegradable oxidized cellulose and its adduct with chitosan

Oxidized cellulose (OC) containing 3–25% (w/w) carboxyl groups represents an important class of biodegradable materials. OC containing 16–24% carboxyl groups is currently accepted for use in human as a hemostatic agent and to prevent the formation and reformation of postsurgical adhesions. Studies show that OC also serves as a good immobilizing matrix for amine drugs, proteins and enzymes.; In this research, OC products containing 8, 13 and 18% carboxyl content have been prepared in high yields (∼80%) by reacting cellulose with a mixture of HNO₃/H₃PO₄-NaNO₂, at room temperature, for different time periods. Different ratios of HNO ₃ and H₃PO₄ used in the reaction mixture had little effect on the carboxyl content and the yields of OC. In general, an increase in the reaction time increased the carboxyl content and slightly decreased the yield of the products. The new OC materials showed substantially reduced degrees of crystallinity and polymerization. The Fourier-transform infrared and Carbon-13 solid-state cross-polarization/magic angle spinning nuclear magnetic resonance spectroscopic results showed the new materials to be structurally similar to commercial oxidized cellulose.; Owing to the presence of carboxyl groups, OCs were found to readily react with chitosan (CA) and produce water insoluble interpolymer complexes. New OC-CA complexes were molded into a cylinder shape. The dried OC-CA complexes hydrated and degraded slowly in pH 6.0 and pH 7.4 phosphate buffer-saline solutions. To demonstrate its use in drug delivery, methotrexate (MTX), an antineoplastic drug, was entrapped in the complex by physically mixing the drug with the wet mass of the complex. The in vitro drug releases from powder, pellet, a semi-solid and cylindrical products were found to be affected by the drying method, drug loading and pH of the dissolution medium being used. The release data from various products showed a linear relationship between the drug released and t1/2, indicating a predominately diffusion controlled drug release process, involving polymer hydration, drug dissolution and diffusion. These results suggested that the OC-CA complexes might have the potential to be used as biodegradable sustained-release drug carriers.