The development of rapid and simple wall coating strategies for high resolution electrophoretic separation of DNA is of crucial importance for the successful implementation of miniaturized polymeric DNA analysis systems. In this report, we present and characterize five methods for the chemical modification of PMMA surfaces for application of wall coating polymers. PMMA surfaces are first oxidized with HNO3 or UV/ozone yielding hydrophilic surfaces containing hydrogen-bonding functionalities. An aqueous solution of wall coating polymer, namely 40DEA_60DMA, HPMC, and PVA, is subsequently flushed through the microchannel resulting in the spontaneous chemisorption of the polymer at the surface of the microchannel. Contact angle measurements of pristine and chemically modified PMMA surfaces were obtained to show a change in wettability of the modified surface. Fast and reproducible electrophoretic separations of a 400-base DNA ladder were performed in PMMA ??CE devices. All analyses were completed in less than 10 min, resulting in separation efficiencies as high as 7?~106 plates/m in a 7.7-cm long separation channel. The duration of UV/ozone treatment was found to have a considerable impact on separation performance. Furthermore, microchips irradiated with UV for 10 min and coated with PVA as well as microchips treated with HNO3 and coated with HPMC were found to have the best separation performance. These results demonstrate simple and robust methods for the surface modification enabling low-cost single use devices for electrophoretic DNA separations.
Pub Type: Journals
Microchip electrophoresis, microfluidic devices, PMMA, surface modification, wall coatings