Absorption and release of zinc and copper ions by chitosan fibers

Chitosan fibers were treated with aqueous solutions of ZnCl 2 and CuSO 4 ·5H 2 O to prepare zinc and copper containing fibers, respectively. Significant weight gains were obtained as the zinc and copper ions were absorbed onto the fibers through chelation with the primary amine groups. The fibers were then placed in contact with aqueous solutions containing NaCl and water soluble proteins, respectively, to assess the release of zinc and copper ions. Results showed that the release of zinc and copper ions were affected by the treatment temperature, time, and the composition of the contacting media. More metal ions were released when the fibers were in contact with aqueous protein solutions than in NaCl solution, indicating the binding abilities of the protein molecules for zinc and copper ions. The zinc and copper containing fibers were tested for their antimicrobial effects against several species of bacteria commonly found in wound and skin. Results showed that these metal containing chitosan fibers had much stronger antimicrobial properties than the original chitosan fiber.