Study of cell seeding on porous poly(d,l-lactic-co-glycolic acid) sponge and growth in a Couette–Taylor bioreactor

In this study, porous poly(d,l-lactic-co-glycolic acid) (PLGA) sponges were fabricated by using a solvent-free supercritical CO2 gas-foaming technique. The sponges were then used as three dimensional scaffolds to culture rat bone marrow stroma (rBMS) cells. The rBMS cells were seeded on the scaffolds using a rocking shaker in three directions with different shaking speeds and times. The amount of cells attached onto the polymer sponges increased with the increase of initial cells amounts. A saturation level [Cellseeded max] was achieved when the initial seeded cells were above 6×104. The seeding curved followed closely to a mathematical model through which [Cellseeded max] and seeding affinity (k) can be calculated. A Couette–Taylor bioreactor was subsequently used to culture the cell-sponge constructs. The Taylor vortex flow patterns generated in the bioreactor were characterized by particle imaging velocimetry (PIV). Computation fluid dynamics simulations were performed to reconfirm the vortex flow characteristics and determine the distribution of shear rate and shear stress quantitatively. The results indicated that moderate shear stresses (0.02–0.19 Pa) generated in the bioreactor improved the proliferation of rBMS cells to around 1.3 times of the static control with well maintained calcium deposition ability of the cells. Relative larger shear stresses (0.24 Pa) helped to improve the calcium deposition ability of the cells but inhibited their proliferations. Larger shear stress (>0.24 Pa) inhibited the proliferation of the cells as well as weakened the ability of cell membrane to preserve calcium ions.