NAMS 2002 Workshop - ICOM 2008

Membrane and Surface Modification III – 2
Friday July 18, 10:15 AM-10:45 AM, Honolulu/Kahuku
Development and Characterization of Ceramic Microfiltration Membrane
Devices for Biomolecule Separation
R. Malaisamy (Speaker), Howard University, Washington DC, USA - malaisamy@gmail.com
L. Lepak, Cornell University, Ithaca, New York, USA
M. Spencer, Cornell University, Ithaca, New York, USA
K. Jones, Howard University, Washington DC, USA
Conventional techniques for bioseparations are frequently being replaced by
membrane separation processes, owing to increased versatility and efficiency of
membranes. In this study, we are tailoring the surface properties of ceramic
(alumina) microfiltration membranes by spin coating thin layers of a protein,
collagen, for biomolecule separation applications. Commercial anodized alumina
membranes were sulfonated by heating in concentrated sulfuric acid for 15
minutes. A commercially available (US Biological) aqueous solution of 0.3%
bovine dermal collagen was spin deposited on the alumina membranes. Either 3
or 6 layers of collagen were spun and crosslinked into fibrils by immersing the
composite membrane in an aqueous solution of dilute glutaraldehyde for 10
minutes. The membranes were then rinsed by immersion in a series of dilute
aqueous buffers, and gradually dehydrated through immersion in a series of
dilutions of ethanol in preparation for critical point drying.
IR spectra were obtained for the modified dried membranes and confirmed the
presence of collagen protein on the substrate. When viewed by scanning
electron microscopy, the thin film composite membranes appeared to have
collagen fibrils spun uniformly on the alumina surface, covering the pores of the
alumina considerably. The water contact angle values for unmodified alumina
and sulfonated alumina membrane surfaces were measured to be 38±2° and
34±2° respectively, whereas the contact angle increased to 78±6° when collagen
was spun onto the membranes. The zeta potential (surface charge) of both pure
alumina and sulfonated alumina membranes at a pH of 5.5 using 1mM KCl
electrolyte solution was around 30 mV, where as it was around 20 mV for the
collagen modified membranes. The pure water permeability was found to lie
around 200 L/(m 2 .h.psi) for the sulfonated alumina base membrane, but declined
to 90 and 10 L/(m 2 .h.psi), when it was coated with 3 and 6 layers of collagen
respectively. The permeate flux value at 30 psi for sulfonated alumina was 5000
L/(m 2 .h), but the flux dropped by almost 50% for 3 layer coated membranes, and
was only 260 L/(m 2 .h) with 6 spun-on layers. These permeability and flux values
for the collagen coated membranes are comparable to ultrafiltration and loose
nanofiltration membranes, and are expected to be suitable for biomolecule
separation.