On-site alginate gelation for enhanced cell proliferation and uniform distribution in porous scaffolds.

High cell density and uniformity in a tissue-engineered construct is essential to expedite the formation of a uniform extracellular matrix. In this study, we demonstrated an on-site gelation approach to increase cellular population and uniformity through porous scaffolds using alginate as gelling material. The on-site gelation was triggered during cell seeding and was shown to effectively restrain the cells in the porous scaffold during subsequent cell cultivation. The initial demonstration of the effectiveness of this system was made with chondrocyte cells, targeted at functional restoration of damaged or dysfunctional cartilage. By limiting cellular mobility, cell population increased by 89% after 7 days of cell culture in scaffolds encapsulating alginate gel as opposed to a 36% increase in scaffolds without gel. The cell distribution throughout the gelled scaffold was found to be more uniform than in the nongelled scaffold. SEM analysis revealed that the cells exhibited typical chondrocytic morphology. Improved cellular functionality was verified by low levels of collagen type I gene expression and steady gene activity levels of collagen type II over 3 weeks of cell cultivation. Alternatively, cells seeded in scaffolds with the conventional cell-seeding method demonstrated increased levels of collagen type I gene expression, indicating the possibility of cell dedifferentiation over long-term cell culture. Success with the chitosan-alginate scaffold model suggested that this flexible on-site gelation method could be potentially applied to other cell and tissue types for enhanced tissue engineering development.