Method for Measuring in Vivo Oxygen Transport Rates in a Bioartificial Organ

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Abstract
Oxygen transport is crucial for the proper functioning of a bioartificial organ. In many cases, the immunoisolation membrane used to protect the transplanted cells from the host's immune system can be a significant barrier to oxygen transport. A method is described for measuring the in vitro and in vivo oxygen transport characteristics of a planar immunoisolation membrane. The in vitro oxygen permeability of the membrane was found to equal 9.22 × 10−4 cm/sec and was essentially the same as the in vivo value of 9.51 × 10−4 cm/sec. The fact that the in vitro and in vivo membrane permeabilities are identical indicates that any fibrotic tissue adjacent to the immunoisolation membrane did not present a significant resistance to the transport of oxygen. The measured oxygen permeability was also found consistent with the solute permeabilities obtained in a previous study for larger molecules. Based on the oxygen permeability results, theoretical calculations for this particular membrane indicate that about 1,100 islets of Langerhans/cm2 of membrane area can be sustained at high tissue densities and only 660 islets/cm2 can be supported at low tissue densities.