Membrane bioreactors enhance microenvironmental conditioning and tissue development.

In membrane bioreactors the cells are isolated from the bulk medium through a semipermeable membrane. This concept, which is analogous to how the circulatory system supplies solid tissues with nutrients, allows the maintenance of cells at much higher densities than is possible in traditional cultures. The membrane-based microbioreactor described herein is easy to operate, requiring only a pipette to load and harvest cells.