Sorbent Membranes: Device Designs, Evaluations and Potential Applications

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Abstract
For the biomedical application of sorbents in extracorporeal circulation, the system must be free of particle release and must be biocompatible. In addition, because of the wide range of biochemical abnormalities generally seen in the human disease state, the use of multiple sorbents should be possible. Based on these criteria, the Enka sorbent Cuprophan membranes have been selected for evaluation. Sorbent membranes are of 2 general types: sorption and sorption-dialysis. Coil parallel plate and capillar designs have been constructed and tested employing sorption-dialysis charcoal membranes of film and hallow fiber configurations. The results have indicated potential advantages. By design, the sorbent membranes prevent direct interaction of the sorbent with blood cells and prevent particle release, making chronic applications safe. Devices employing sorbent fibers are particularly suited to select applications where higher sorbent contents are required or ultrafiltration is not desired. To optimize the application of sorbents and the sorbent employed and the length of treatment, a general scheme for evaluation of sorbent systems has been established involving 3 phases: 1) equilibrium isotherm studies to determine the selectivity and capacity of the sorbent system for the solute, 2) kinetic studies to determine mass transfer properties of the sorbent system in the absence of fluid dynamic resistance and 3) device evaluation to determine overall mass transfer properties. In device designs, it is possible to separate the effects of sorption and fluid dynamics and to design around the limiting parameters.