August 20, 2007 ACS Meeting News Improving Dialysis Membranes Nanoporous alumina membrane mimics human kidneys better than current technology Carmen Drahl
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.
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