Optimization of the microenvironment for mammalian cell culture in flexible collagen microspheres in a fluidized-bed bioreactor.

Flexible, three-dimensional, collagen Microspheres have been developed to actively promote a natural, optimal microenvironment for large-scale tissue culture of mammalian cells. The transport of nutrients into and cell products out of the Microspheres is enhanced by forced convective flow, which is the result of the tumbling of Microspheres and the dynamic properties of media flow in the fluidized-bed bioreactor. The collagen Microspheres have important characteristics of composition and morphology essential for optimal cell-matrix and cell-cell interactions. These interactions lead to high cell density and productivity through the dynamic modification of the microenvironment by cell-derived extracellular constituents. The collagen and Microsphere/fluidized-bed system provides the means to control and optimize the diffusive and contact components of the cells' microenvironment. Adaptation of cells to this microenvironment often results in dramatic increases in cell-specific productivity. Production of biotherapeutics in this process can be routinely performed in serum-free media, often leading to high productivity and product quality.