Transport characterization of membranes for immunoisolation

Area of Science:

• Biomaterials Science
• Membrane Transport
• Immunoisolation Technology

Background:

• Implantable bio-hybrid organs require effective immunoisolation to prevent rejection.
• Hollow fibre membranes are crucial for creating diffusion barriers in such devices.
• Accurate characterization of diffusive transport is essential for optimizing membrane performance.

Purpose of the Study:

• To characterize the diffusive transport properties of hollow fibre membranes.
• To determine mass transfer coefficients for a range of molecular weights (10^2–10^5 MW).
• To evaluate membrane performance for immunoisolatory applications in vivo.

Main Methods:

• Developed techniques to accurately determine mass transfer coefficients.
• Utilized a flowing dialysis-type apparatus for small-molecular-weight diffusants (e.g., glucose, vitamin B12).
• Employed a static diffusion chamber for large-molecular-weight markers (e.g., albumin, immunoglobulin G, dextrans).
• Applied a resistance-in-series model, accounting for boundary layer effects.

Main Results:

• Small-molecular-weight species (< 13,000 MW) exhibited diffusion coefficients 2-4 times lower in the membrane than in water.
• Large-molecular-weight species showed diffusion rates hindered several thousand-fold compared to their diffusion in water.
• Demonstrated effective immunoisolation of allografts and xenografts in vivo using the studied membrane type.

Conclusions:

• Hollow fibre membranes significantly impede molecular diffusion, with greater hindrance for larger molecules.
• These findings support the use of these membranes in immunoisolatory devices for bio-hybrid organs.
• The developed characterization techniques provide a robust method for evaluating membrane transport properties.