A new type of dialysis membrane made from nanoporous alumina may better approximate human kidneys’ ability to remove waste products from the bloodstream than the technology currently in use. Chemists Mark Schneider and Loyd Bastin of Widener University, in Chester, Pa., described the new membrane this week in the Division of Biological Chemistry at the American Chemical Society’s national meeting in Boston.

J. Med. Devices © 2007

SAFE PASSAGE Dialysis membrane made of alumina (scanning electron microscope image, left) has a more regular pore pattern than one made of polysulfone (right).

Dialysis membranes clear toxins such as urea from the blood and preserve water balance and serum protein levels in blood, all while leaving red and white blood cells intact. Aluminum oxide is a well-known nanostructured material, but it represents a complete departure from materials that traditionally make up membranes, such as cellulose and polysulfone. Alumina offers the advantage of easily controllable pore sizes and has a more regular pore pattern than polysulfone. The material’s pore properties could better maintain consistent blood flow through the dialyzer.

In Boston, Schneider and Bastin reported that an alumina dialysis membrane developed by Widener mechanical engineer Zhongping Huang has passed all of their initial biocompatibility tests.

Huang designed the thin-walled alumina membrane and previously demonstrated that it mechanically outperforms its predecessors (J. Med. Devices 2007, 1, 79). For example, the alumina membrane can handle double the flow rate of a polysulfone membrane, due in part to its regular pore structure. And alumina’s higher melting point renders the membrane more resistant to the heat used in sterilization procedures.

To test whether the alumina membrane could function in dialysis procedures, Schneider, Bastin, and Huang flowed bovine blood through the membrane for three hours—roughly the length of a typical dialysis session. Atomic absorption spectroscopy detected no aluminum leaching from the membrane into the blood and dialysate; leaching could pose a hazard to a patient. In addition, the total free hemoglobin protein content in the blood was constant during dialysis, indicating that red blood cells remained intact upon passage through the membrane. Serum protein levels also were consistent during dialysis.

The team plans to follow up the current work by assaying specific proteins that are abundant in blood, such as lactate dehydrogenase, to confirm that protein structure and function is conserved during alumina-membrane-mediated dialysis.