Microwave-assisted grafting polymerization modification of nylon 6 capillary-channeled polymer fibers for enhanced weak cation exchange protein separations

A weak cation exchange liquid chromatography stationary phase (nylon-COOH) was prepared by grafting polyacrylic acid on to native nylon 6 capillary-channeled polymer (C-CP) fibers via a microwave-assisted radical polymerization. To the best of our knowledge, this is the first study of applying microwave-assisted grafting polymerization to affect nylon material for protein separation. The C-CP fiber surfaces were characterized by attenuated total reflection (ATR) infrared spectroscopy and scanning electron microscope (SEM). The anticipated carbonyl peak at 1722.9 cm^-1 was found on the nylon-COOH fibers, but was not found on the native fiber, indicating the presence of the polyacrylic acid on nylon fibers after grafting. The nylon-COOH phase showed a ∼12× increase in lysozyme dynamic binding capacity (∼12 mg mL^-1) when compared to the native fiber phase (∼1 mg mL^-1). The loading capacity of the nylon-COOH phase is nearly independent of the lysozyme loading concentration (0.05-1 mg mL^-1) and the mobile phase linear velocity (7.3-73 mm s^-1). The reproducibility of the lysozyme recovery from the nylon-COOH (RSD = 0.3%, n = 10) and the batch-to-batch variability in the functionalization (RSD = 3%, n = 5) were also investigated, revealing very high levels of consistency. Fast baseline separations of myoglobin, α-chymotrypsinogen A, cytochrome c and lysozyme were achieved using the nylon-COOH column. It was found that a 5× increase in the mobile phase linear velocity (7.3-to-36.5 mm s^-1) had little effect on the separation resolution. The microwave-assisted grafting polymerization has great potential as a generalized surface modification methodology across the applications of C-CP fibers.

Parallel, open-channel lateral flow (immuno) assay substrate based on capillary-channeled polymer films

Presented here is a novel implementation of polypropylene capillary-channeled polymer (C-CP) films, functionalized for bioaffinity separations and implemented as a platform for lateral flow (immuno) assays.

Evidence for the Intercalation of Lipid Acyl Chains into Polypropylene Fiber Matrices

Headgroup-functionalized lipids are being developed as ligand tethers for high selectivity separations on polypropylene capillary-channeled polymer fiber stationary phases. Surface modification is affected under ambient conditions from aqueous solution. This basic methodology has promise in many areas where robust modifications are desired on hydrophobic surfaces. In order to understand the mode of adsorption of the lipid tail to the polypropylene surface, lipids labeled with the environmentally sensitive 7-nitro-2-1,3-benzoxadiazol-4-yl (NBD) fluorophore were used, with NBD covalently attached to the headgroup (NBD-PE) or the acyl chain (acyl NBD-PE) of the lipid. When modified with the acyl NBD-PE, fluorescence imaging of the fiber at excitation wavelengths increasing from 470 to 510 nm caused a 32 nm shift in emission toward the red edge of the absorption band, indicating that the NBD molecule (and thus the lipid tail) is motionally restricted. Fluorescence imaging on fibers modified with NBD-PE or the free NBD-Cl dye molecule yields no change in the emission response. The results of these imaging studies provide evidence that the acyl chain portions of the lipids intercalate into free volume of the polypropylene fiber structure, yielding a robust means of surface modification and the potential for high ligand densities.