Evaluation of synthesized lipid tethered ligands for surface functionalization of polypropylene capillary-channeled polymer fiber stationary phases

Abstract

Polypropylene (PP) capillary-channeled polymer (C-CP) fibers have been used in this laboratory as stationary phases for high performance liquid chromatography and solid phase extraction of proteins. Greater selectivity has been realized through the functionalization of the PP fibers through the physical adsorption of commercially available head group-modified poly(ethylene glycol) lipids (PEG-lipids), where the head group is chosen to affect affinity separations. We refer to this general surface modification methodology as lipid tethered ligands (LTLs). In this study, LTLs were synthesized by solid phase synthesis. In comparison to the commercial PEG-lipids, the synthesized LTLs contain no chemically labile phosphate groups. Instead of an ester linkage in the commercial lipids, amide functionality was used in the synthesized LTLs to attach the lipids and ligands. By use of fluorescence imaging of FITC-labeled LTLs, the synthesized LTL was shown to be superior to the commercial LTL in terms of the adsorption efficiency to PP C-CP fibers, the resistance to solvent wash from the PP C-CP fibers, and their chemical stability under acidic, neutral and basic conditions. The PP C-CP fibers functionalized with a synthesized LTL that was biotinylated at the head group are shown to be capable of capturing streptavidin from E. coli cell lysate more efficiently than the PP C-CP fibers functionalized with the commercial biotinylated PEG-lipid. The functionalization of PP C-CP fibers with the synthesized LTLs is a simple, but highly efficient, method to generate novel stationary phases with a variety of functionalities for solid phase extraction and liquid chromatography.

Polyethylenimine modified poly(ethylene terephthalate) capillary channeled-polymer fibers for anion exchange chromatography of proteins

“…This would seem to suggest that the formation of the PEI layer on PET does not follow a simple kinetic mode. The upper density value of ∼143 mol g −1 (48 mol m −2 ) is very much in line with the direct EDA treatment of PET [15], which only produces primary amines, and ∼2× the primary amine density present as end groups for native nylon 6 C-CP fibers [13].…”

“…To that end, we have recently reported use of ethylenediamine (EDA) to introduce functional ligands on PET C-CP fiber stationary phase [15], eventually adding biotin ligands to the surface. In that work, amine densities ranging from 13.9 to 60.0 mol m −2 were realized in the initial activation step.…”

“…The ninhydrin test method was used to determine the primary and secondary amine density on the fiber surfaces as previously described [13,15,37]. Each fiber sample (5-6 mg) was placed into a test tube containing 0.5 mL of 10% isopropanol, 0.5 mL of 10% pyridine and 1 mL of the ninhydrin solution composed of 2.325 mL propionic acid, 12.5 mL 2-methoxyethanol, 5.045 g sodium propionate, and 0.5 g ninhydrin, with the total volume adjusted to 25 mL with deionized water.…”

“…Likewise, a completely new family of ligands has been developed based on the high affinity for aliphatic chains for the hydrophobic PP fiber surfaces. Lipid tethered ligands (LTLs) having a variety of capture head groups readily adsorb at room temperature, and are immune from elution/leakage from the column under any sort of conditions common to biomolecule separations [14][15][16][17]. An example of covalent coupling involves the use of ethylenediamine as a means of activating PET C-CP fibers, yielding a surface rich with primary amines.…”

“…An example of covalent coupling involves the use of ethylenediamine as a means of activating PET C-CP fibers, yielding a surface rich with primary amines. These amines are then readily modified with capture ligands such as biotin for protein affinity separations [15].…”