Biomimetic characterization by micro-computed tomography (μCT) of 3D hollow fibre membrane network bioreactors for...

Hollow Fiber Membrane Bioreactors (HFMBs) support mammalian cell culture at high cell density by enabling effective transport of nutrients, gases and metabolites to/from cells and by offering high membrane surface area-to-bioreactor volume ratios, scalability and flexibility in design. A recent study showed that shell-and-tube HFMBs with cells in the extracapillary space (ECS) for medicine may be designed to mimic the bone architecture for bone tissue engineering (TE). A more transport-efficient HFMB, the BRx-HFMB, consists of a 3D stack of alternating cross-woven mats of microporous and gas-permeable hollow fiber membranes with cells in the ECS and medium flowing inside the membranes. This design was shown to support the culture of a large mass of densely packed cells with high oxygen and nutrient metabolic demands similar to bone cells. Its biomimicry and rationale for good performance are poorly characterized, hindering exploitation of its characteristics for bone TE. Herein, we report the architectural and biomimetic characterization of pore/void distribution in the ECS of laboratory BRx-HFMBs using non-invasive non-destructive micro-computed tomography and advanced image analysis to minimize artifacts. The results suggest that the ECS pore architecture and specific surface area of BRx-HFMBs mimic those of bone tissue, favoring cell migration around, and adhesion on, membranes at clinical cell densities. The membrane network architecture enables cell perfusion with medium, and membranes act as spatially distributed oxygen sources promoting oxygen transport through the cell construct over longer distances than in static bioreactors. This supports the use of BRx-HFMBs to develop cellular models of bone tissue for drug testing and precision medicine.