Long term culture of epithelia in a continuous fluid gradient for biomaterial testing and tissue engineering

Epithelia perform barrier functions being exposed to different fluids on th e luminal and basal side. For long-term testing of new biomaterials as arti ficial basement membrane substitutes, it is important to simulate this flui d gradient. Individually-selected biomaterials can be placed in tissue carr iers and in gradient containers, where different media are superfused. Epit helia growing on the tissue carriers form a physiological barrier during th e whole culture period. Frequently however, pressure differences between th e luminal and basal compartments occur. This is caused by a unilateral accu mulation of gas bubbles in the container compartments resulting in tissue d amage. Consequently, the occurence of gas bubbles has to be minimized. Air bubbles in the perfusion culture medium preferentially acumulate at sites w here different materials come into contact. The first development is new sc rew caps for media bottles, specifically designed to allow fluid contact wi th only the tube and not the cap material. The second development is the se paration of remaining gas bubbles from the liquid phase in the medium using newly-developed gas expander modules. By the application of these new tool s, the yield of embryonic renal collecting duct epithelia with intact barri er function on a fragile natural support material can be significantly incr eased compared to earlier experiments.