title: Surface modification of the channels of poly(dimethylsiloxane) microfluidic chips with polyacrylamide for fast electrophoretic separations of proteins.
abstract: The electrophoresis of proteins was investigated using poly(dimethylsiloxane) (PDMS) microfluidic chips whose surfaces were modified with polyacrylamide through atom-transfer radical polymerization. PDMS microchips were made using a glass replica to mold channels 10 microm high and 30 microm wide, with a T-intersection. The surface modification of the channels involved surface oxidation, followed by the formation of a self-assembled monolayer of benzyl chloride initiators, and then atom-transfer radical polymerization to grow a thin layer of covalently bonded polyacrylamide. The channels filled spontaneously with aqueous buffer due to the hydrophilicity of the coating. The resistance to protein adsorption was studied by open-channel electrophoresis for bovine serum albumin labeled with fluorophor. A plate height of 30 microm, corresponding to an efficiency of 33 000 plates/m, was obtained for field strengths from 18 to 889 V/cm. The lack of dependence of plate height on field strength indicates that there is no detectable contribution to broadening from adsorption. A 2- to 3-fold larger plate height was obtained for electrophoresis in a 50-cm polyacrylamide-coated silica capillary, and the shape of the electropherogram indicated the efficiency is limited by a distribution of species. The commercial capillary exhibited both reversible and irreversible adsorption of protein, whereas the PDMS microchip exhibited neither. A separation of lysozyme and cytochrome c in 35 s was demonstrated for the PDMS microchip.
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
authors.forename: Deqing
authors.initials: D
authors.lastname: Xiao
authors.forename: Thai Van
authors.initials: TV
authors.lastname: Le
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Wirth
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000818:Animals; D045304:Cytochromes c / Q000302:isolation & purification; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D046209:Electrophoresis, Microchip / Q000295:instrumentation / Q000379:methods*; D046210:Microfluidic Analytical Techniques; D009113:Muramidase / Q000302:isolation & purification; D011506:Proteins / Q000302:isolation & purification*; D013499:Surface Properties; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D045304:Cytochromes c; D004129:Dimethylpolysiloxanes; D009113:Muramidase; D011506:Proteins; D000099166:Polyacrylamides