Numberical simulation of fluid flow and three-dimensional expansion of tissue engineering seed cells in large scale inside a novel rotating wall hollow fiber membrane bioreactor

Currently, RWVB (Rotating wall vessel bioreactor) combined with a microcarrier used for in vitro expansion revealed that the suspended cells attached on the microcarrier will collide with outer and inner cylinders of RWVB inevitably, which leads to harmful results to the cells. Considering this, hollow fiber (HF) membrane module treated as a cell carrier is adopted to combine with RWVB to form a novel rotating wall hollow fiber membrane bioreactor (RWHMB) to avoid aforementioned harmful collision, since the cells cultured inside this bioreactor will mainly adhere to large specific surface of hollow fiber membrane module. Prior to cell experiment, mathematical simulations concerned with flow field inside RWHMB are performed by CFD, which includes the distributions of the total pressure, velocity, and shear stress with the variation of rotating speeds and directions, as well as the radial location and diameter of hollow fiber membrane. To further confirm the feasible parameters getting from the simulation, this RWHMB is adopted to expand osteoblasts isolated from SD rats within its dynamic conditions. Cell expansion in T-flask is carried out as a negative control. The results showed that with the same rotating direction and speed of 10 rpm, inner and outer cylinders of RWHMB generated cyclical stress stimulus, which was acceptable to cell expansion and facilitated the secretion of extracellular matrix. Besides, hollow fiber membrane carrier with a diameter of 0.2 mm has an excellent biocompatibility and their radial locations presented a tiny influence on flow field inside the culture chamber.