Electroactive intercalators for DNA analysis on microchip electrophoresis

Abstract

Miniaturized analytical systems, especially microchip CE (MCE), are becoming a promising tool for analytical purposes including DNA analysis. These microdevices require a sensitive and miniaturizable detection system such as electrochemical detection (ED). Several electroactive DNA intercalators, including the organic dye methylene blue (MB), anthraquinone derivatives, and the metal complexes Fe(phen)3 2+ and Ru(phen)3 2+, have been tested for using in combination with thermoplastic olefin polymer of amorphous structure (Topas) CE-microchips and ED. Two end-channel approaches for integration of gold wire electrodes in CE-ED microchip were used. A 250 microm diameter gold wire was manually aligned at the outlet of the separation channel. A new approach based on a guide channel for integration of 100 and 50 microm diameter gold wire has been also developed in order to reduce the background current and the baseline noise level. Modification of gold wire electrodes has been also tested to improve the detector performance. Application of MCE-ED for ssDNA detection has been studied and demonstrated for the first time using the electroactive dye MB. Electrostatic interaction between cationic MB and anionic ssDNA was used for monitoring the DNA on microchips. Thus, reproducible calibration curves for ssDNA were obtained. This study advances the feasibility of direct DNA analysis using CE-microchip with ED.

MCE‐electrochemical detection for following interactions of ssDNA and dsDNA with methylene blue

“…The amperometric detector was situated in the waste reservoir (B) with a three-electrode configuration and was previously described [26]. Briefly, the reference (Ag/AgCl/ saturated KCl) and counter (Pt wire) electrodes were coupled in a 250 mL micropipette tip that was introduced in the detection reservoir for performing the measurements.…”

“…Here metal complexes [23], anticancer agents [22] or organic dyes [25] are used. All these kind of molecules have allowed the The interaction between ssDNA and methylene blue (MB) as ligand has been previously studied [26]. Among all possible redox-active ligands, MB is a commercial organic dye that presented an excellent electrochemical behavior.…”

New analytical portable instrument for microchip electrophoresis with electrochemical detection

“…Moreover, the possibilities offered by this new tool have been studied in clinical [6,7], environmental [8][9][10], and food [11][12][13][14][15] areas. However, the in situ analysis of real samples is far away from the actual state-of-art of MCE.…”

“…Nowadays, various polymeric materials [16] are used such as PDMS [17,18], PMMA [19,20], polycarbonate [21], poly(ethylenterephthalate) [22,23], thermoset polyester [24,25], and polyester toner [26,27], Zeonix/ Zeonor [28,29] or thermoplastic olefin polymer of amorphous structure [7,30,31].…”

Multiple‐point electrochemical detection for a dual‐channel hybrid PDMS‐glass microchip electrophoresis device

“…Elasticity of PDMS is very useful for the easy integration of working electrodes. In our group, 100-mm-diameter gold wires have been integrated for end-channel detection in glass [26] and Topas s [27] microchips. In both cases, the last part of one of the plates of the microchip is eliminated (this with the microchannel structure in the case of glass or the cover plate in the case of Topas) and the wire is aligned at the end of the microchannel.…”