Fluid dynamics of bioreactors for tissue engineered cartilage

Various types of bioreactors have been investigated for use in producing tissue-engineered human cartilage. These include rotating-wall vessels, spinner flasks, perfusion and compression/perfusion bioreactors. In each type of reactor the flow of the culture medium causes the growing tissue to experience a different dynamic environment, potentially influencing the character of the final tissue. Laboratory measurements have been made in model systems that obey requirements for dynamic similarity to prototype reactors. Local measurements of the velocity field made using particle-image velocimetry (PIV) permit the determination of local shear stresses within the observation plane, particularly in the vicinity of the tissue-construct model. Computationally, simulations have been performed with the commercial package FLUENT; these are compared with results from the laboratory experiments. We shall describe laboratory and numerical experiments conducted for various types of bioreactors used for the production of cartilage, focusing on those flow characteristics most likely to play a role in tissue development.