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. The parallel ∼80 µm × 80 µm channels pass test solutions down the 30 mm film length via spontaneous wicking action, setting up the possibility for immobilizing different capture agents in the respective channels. The base-film modification process is divided into two steps: ultraviolet light treatment to improve hydrophillicity of the polypropylene substrate and the physical adsorption of a functionalized lipid tethered ligand (LTL) as a selective capture agent. The entire modification procedure is performed under ambient conditions in an aqueous solution without extreme pH conditions. In this demonstration, physical adsorption of a biotinylated-LTL onto the UV-treated PP surface selectively captures Texas Red-labeled streptavidin (SAv-TR) in the presence of enhanced green fluorescence protein (EGFP), which passes without retention in less than 5 s. In addition to the fluorescence imaging of the protein solutes, matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) was used to confirm the formation of the LTL-SAv conjugates on the channel surface as well as to demonstrate an alternative means of probing the capture step. The present effort sets the groundwork for further development of C-CP films as a parallel, multi-analyte LFA platform; a format that to-date has not been described.

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

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.