Hemolglobin encapsulation in chitosan/calcium alginate beads

A mild chitosan/calcium alginate encapsulation process, as applied to encapsulation of hemoglobin, was investigated. The first procedure consisted of adding dropwise a hemoglobin-containing sodium alginate mixture in a chitosan solution, then hardening the interior of capsules thus formed, in the presence of CaCl₂. In the second method, the droplets were directly pulled off in a chitosan–CaCl₂ mixture. Both procedures led to beads containing a high concentration in entrapped hemoglobin as more than 90% of the initial concentration (150 g/L) were retained inside the beads provided that the chitosan concentration was great enough. The molecular weight of chitosan (M̄_u 245,000 or 390,000) and the pH of its solution (2, 4, or 5.4) had only a slight effect, the best retention being obtained with beads prepared at pH 5.4. The hemoglobin release during the bead storage in water was found to depend on the conditions of their formation and especially on the chitosan molecular weight. The best retention during storage in water was obtained with beads prepared with the high M̄_u chitosan solution at pH 2. Considering the total loss in hemoglobin during the bead formation and after 1 month of storage in water, the best results were obtained by preparing the beads in an 8 g/L solution of a 390,000 chitosan at pH 4 (less than 7% of loss with regard to the 150 mg/L initial concentration). © 1994 John Wiley & Sons, Inc.