Permeability and separation characteristics of polypeptide-functionalized polycarbonate track-etched membranes

The use of polypeptide-functionalized membranes with known porosity and uniform pore sizes allows a better understanding of the separation characteristics in nanodomains. A stimuli-responsive polypeptide, poly-L-glutamic acid (PLGA), was immobilized on a polycarbonate track-etched (PCTE) membrane. First, PCTE membrane was gold-coated under convective conditions, and a thiol, 3-mercapto 1,2-propanediol (MPD), was chemisorbed on the modified surface. Second, the MPD molecule was oxidized with sodium periodate to obtain an aldehyde functionality, which was further reacted with the amino group on the PLGA molecule, making possible a single point polypeptide attachment. The morphology of the modified membrane was analyzed by electron microscopy (SEM, TEM) imaging, confirming uniform structure. Modified membrane performances, with starting diameters of 30 and 100 nm, were evaluated in terms of solute (ionic and neutral) rejections and water permeability. Both solute and water transport through membrane were reversibly regulated by pH. The effective membrane charge was calculated using the extended Nernst-Plank equation coupled with Donnan equilibrium and electroneutrality conditions.