Metabolic activity and proliferation of CHO cells in hydroxyethyl methacrylate-methyl methacrylate (HEMA-MMA) microcapsules

To better understand encapsulated cell behaviour, Chinese Hamster Ovary (CHO) fibroblasts were encapsulated in HEMA-MMA microcapsules and short-term (<2 wks) proliferation and changes in metabolic activity were investigated in vitro. CHO cells were observed to undergo rapid proliferation in the first week following encapsulation after which a growth arrest was obtained at approximately 3500 cells/capsule. The cell growth was localized in aggregates in the capsule core, resulting in high local cell density but low cell density in the whole capsule interior (approximately 10(7) cells/mL). The total metabolic activity, as determined by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium) assay, within the microcapsules increased in the first week, with no significant change afterwards. A broad variation in metabolic activity among the individual capsules was obtained. Supplementing the cell suspension with 20% Ficoll 400 during the encapsulation process resulted in significantly higher morphological uniformity among the individual capsules (with reduced capsule wall thickness and eccentricity); however, this did not change the extent of heterogeneity in metabolic activity. We conclude that viability and proliferation ability (at least to a limited extent) of CHO cells are maintained in HEMA-MMA microcapsules. The local cell growth and subsequent growth arrest remain issues to be addressed in order to obtain better utilization of the microcapsule core volume. Alternatively, small diameter (< 400 microns as opposed to the present approximately 750 microns diameter) capsules are necessary.