Self-associating block copolymer networks for microchip electrophoresis provide enhanced DNA separation via inchworm chain dynamics

摘要

We describe a novel class of DNA separation media for microchip electrophoresis, “physically crosslinked” block copolymer networks, which provide rapid (< 4.5 min) and remarkably enhanced resolution of DNA in a size range critical for genotyping. Linear poly(acrylamide-co-dihexylacrylamide) (LPA-co-DHA) comprising as little as 0.13 mol% dihexylacrylamide yields substantially improved electrophoretic DNA separations compared to matched molar mass linear polyacrylamide. Single-molecule videomicroscopic images of DNA electrophoresis reveal novel chain dynamics in LPA-co-DHA matrices, resembling inch-worm movement, to which we attribute the increased DNA resolution. Substantial improvements in DNA peak separation are obtained, in particular, in LPA-co-DHA solutions at polymer/copolymer concentrations near the interchain entanglement threshold. Higher polymer concentrations yield enhanced separations only for small DNA molecules (< 120 base-pairs). Hydrophobically crosslinked networks offer advantages over conventional linear polymers based on enhanced separation performance (or speed) and over chemically crosslinked gels because hydrophobic crosslinks can be reversibly broken, allowing facile microchannel loading.