Poly(acrylamide-co-alkylacrylamides) for Electrophoretic DNA Purification in Microchannels

Abstract

We have created a family of water-soluble block copolymers of acrylamide and N-alkylacrylamides that are designed to selectively remove proteins from DNA via microchannel electrophoresis. It was hypothesized that the inclusion of hydrophobic subunits in the polymer chain, in sufficient concentration, could lead to protein adsorption due to hydrophobic interactions. A series of N-alkylacrylamide comonomers with varying alkyl chain lengths (C4, C6, C8) and also an N,N-dialkyl group (C6−C6) were synthesized via reactions between acryloyl chloride and the respective alkylamines. Copolymers were synthesized using an aqueous “micellar” polymerization technique, which involves dissolving acrylamide in the aqueous phase while hydrophobic monomers are solubilized in sodium dodecyl sulfate micelles. Copolymers comprising up to 4 mol % of a hydrophobic subunit (as verified by ¹H NMR) were synthesized. Polymer molecular weights were determined by tandem gel permeation chromatography−multiangle laser light scattering, and ranged from 1.5 × 10⁶ to 4.3 × 10⁶. Capillary electrophoresis analysis of bovine serum albumin and β-lactoglobulin migration in these matrixes revealed that the octylacrylamide and dihexylacrylamide copolymers show the most significant extent of protein adsorption while butylacrylamides show no noteworthy adsorption trend. All copolymer matrixes studied allowed the passage of a dsDNA digest, and displayed some DNA sieving ability at 0.5% (w/w) in TTE (50 mM Tris, 50 mM TAPS, 2 mM EDTA, pH 8.4) buffer. These matrixes are demonstrated in on-chip experiments to adsorb protein, in a step toward meeting the front-end processing goals of μ-TAS for genetic analysis applications.