Abstract:

Sodium alginate-chitosan(AC) microcapsules are often used as the immobilization carriers for cell culture.  They are composed of porous gel as the core facilitating cell adhesion, and coated with polyelectrolyte complex membrane protecting cells and allowing selective mass transfer.  Therefore, the regulation and control of membrane properties can directly affect the growth and metabolism of cells in microcapsules.  Among many parameters, pH of chitosan solution is the important one.  In this paper, the formation of polyelectrolyte membrane, the degree of complex formation and protein diffusion at different pH values were directly observed in situ by using a confocal laser scanning microscope(CLSM).  The effect of pH on the properties of AC microcapsule membrane was discussed.  The optimal pH was determined in the preparation of AC microcapsules with different cells(animal and microbial cells).  It was demonstrated that the membrane thickness showed “high-low-high” shape, the swelling behavior of microcapsules “low-high-low” shape and the protein diffusion across the membrane “low-high-low” shape as a function of pH, the inflection points all appeared at pH=4.00 and 5.50.  Combining with the sensitivity experiment of different kinds of cells to environment pH, it was suggested that the optimal pH of chitosan solution for AC microencapsulated animal cells was 5.50, AC microencapsulated E.  coli cells 5.00, and AC microencapsulated yeast cells such as saccharomyces cerevisiae(S.  cere.) 4.50, respectively.

Key words: Chitosan; Alginate; pH; Microcapsule; Cell culture