No abstract

Microchips for integrated capillary electrophoresis systems were produced by molding a poly(dimethylsiloxane) (PDMS) silicone elastomer against a microfabricated master. The good adhesion of the PDMS devices on clean planar surfaces allows for a simple and inexpensive generation of networks of sealed microchannels, thus removing the constraints of elaborate bonding procedures. The performance of the devices is demonstrated with both fast separations of φX-174/HaeIII DNA restriction fragments labeled with the intercalating dye YOYO-1 and fluorescently labeled peptides. Detection limits in the order of a few zeptomoles (10(-)(21) mol) have been achieved for each injected DNA fragment, corresponding to a mass detection limit of ∼2 fg for the 603 base pair fragment. Single λ-DNA molecules intercalated with YOYO-1 at a base pair-to-dye ratio of 10:1 could be detected with an uncomplicated laser-induced fluorescence detection setup. High single-molecule detection efficiency (>50%) was achieved under electrophoretically controlled mass transport conditions in PDMS microchannels.

A micromachined chemical analysis device based on capillary electrophoresis has been successfully used for very fast size separation of a synthetic mixture of fluorescent phosphorothioate oligonucleotides ranging from 10 to 25 bases in length.The device consists of a channel system which has been formed in the surface of a glass plate by a standard photolithographicalprocess. An integrated volume-defined sample injector allowed for unbiased electrokinetic introduction of sample plugs of 150jum length (corresponding sample volume, 90 pL) into the separation channel. This well-defined injection procedure, in combination with the application of high electric fields of up to 2300 V/cm, resulted in size separation of single-stranded oligonucleotides in less than 45 s when a separation distance of 3.8 cm was used. Column efficiencies of up to 200 000 theoretical plates with an associated plate height of 0.2 ^m were obtained. Fast repetitive sample injection and analysis could be demonstrated with excellent reproducibilities for both migration time (<0.06%) and peak height (< 1.7%). The results might also be of relevance for DNA sequencing, where fast oligonucleotide analysis is of key importance. Moreover, they provide a route to "on-line" analysis of synthetic and natural oligonucleotides and possibly other classes of biopolymers.The feasibility of the integration of miniaturized separation techniques into compact devices by using standard photolithographic fabrication procedures has recently been demonstrated in a number of exemplary studies.1-3 In the case of electrical field driven separation techniques, functional models for high-speed capillary electrophoresis (CE),4-7 synchronized cyclic capillary electrophoresis (SCCE),1 2345678 and free flow electrophoresis (FFE)9 have been developed and their separation performance has been evaluated.

The Influence of different borate buffers as background electrolytes on the electrophoretic mobilities of underivatlzed mono-and oligosaccharides as well as glycosylated peptides In capillary electrophoresis Is Investigated. Electrophoretic mobilities of various carbohydrates are calculated, and some structural characteristics of sugar-borate complexes are deduced. Due to the fact that the addKIon of borate to aqueous solutions of mono-and olgosaccharides results In an Increase of absorbance at 195 nm, the sugars can be detected without derivatlzatlon. Additionally, resolution and efficiency were dramatically Improved by performing electrophoresis at elevated temperatures up to 60 °C. CE experiments of a hexapeptlde and Its glycosylated form confirm that not only does glucose complex with borate In the open-chain form but, under conditions of very high borate concentrations, the pyranose form also complexes with borate.

Integrated capillary electrophoresis (ICE) is emerging as a new analytical tool allowing fast, automated, miniaturized and multiplexed assays, thus meeting the needs of the pharmaceutical industry in drug development. The current state-of-the-art of ICE is described with an emphasis on the choice of the support material (glass or polymeric materials), electrokinetic fluid handling, and injection and detection issues. Strategies and chip designs for pre- or post-column derivatization, DNA sequencing, on-line PCR analysis, on-chip enzymatic sample digestion, fraction isolation, and immunoassays are presented. The review concludes with a brief outlook.