Characterization of cell growth and fluid flow distributions in hollow-fiber bioreactors using magnetic resonance micro-imaging and magnetic resonance spectroscopy

Large-scale Mammalian cell culture has received considerable attention in recent years owing to the demand for such biological products as monoclonal antibodies, hormones, vaccines, and as a result of bioartificial organ development. Hollow-fiber bioreactors (HFBR) are an important and widely used technology within these and other areas of biomedicine. The nature of HFBR's is that the cell culture growing within in subject to inhomogeneous concentrations of nutrients such as oxygen, glucose, high-molecular growth factors. Moreover, the environment experienced by the cells is thought to vary considerably in response to different modes of bioreactor operation. Optimization of these devices requires a non-invasive method of monitoring physical parameters such as fluid flow distributions existing within the bioreactor and the physiological response of the cells.; In this work ultra-high resolution NMR velocity imaging was used to map the axial fluid flow profiles in the extracapillary space (ECS) of a commercial hollow-fiber bioreactor. The results showed significant non-uniformity in the axial flow. The axial velocity distributions computed from the NMR data showed good correspondence with velocity distributions that were generated from a simple model that considers the ECS as an assemblage of tubes with distributed radii.; Experiments performed with hybridoma cell cultures showed that the non-uniformity in the ECS flow is a primary factor in determining the initial distribution of cells within the bioreactor following inoculation. Moreover, high-resolution (13 {dollar}mu{dollar}m in plane) diffusion weighted imaging showed that the non-uniform cell distribution could result in a significant redistribution of the hollow-fibers. Quantitative diffusion coefficient and T{dollar}sb2{dollar} maps showed that cell growth is probably diffusion limited and therefore optimal performance requires enhanced transmembrane mass transport.; The optimization of cryopreservation protocols for the long-term storage of native and engineered tissue is an important problem in biomedical engineering. The potential for using hollow-fiber bioreactors as a model system for such studies was investigated. It was demonstrated that cell volume changes resulting from exposure to dimethyl sulfoxide (a cryopreservation agent) could be monitored using a hollow-fiber bioreactor. In addition possible metabolic changes are discussed.