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 similar to 12x increase in lysozyme dynamic binding capacity (similar to 12 mg mL(-1)) when compared to the native fiber phase (similar to 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, alpha-chymotrypsinogen A, cytochrome c and lysozyme were achieved using the nylon-COOH column. It was found that a 5x 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. (C) 2016 Elsevier B.V. All rights reserved.