The microchip capillary electrophoresis devices were fabricated by using poly(methyl methacrylate)(PMMA) plastic material via an injection-molding process. The molded devices were enclosed by utilizing a mixed organic solvent to another PMMA film. The channel structure was very well defined and the molded channel surfaces were very smooth. The transmissivity was in the range from 91% to 93%(at the wavelength of 400—1 000 nm). In comparison to glass microchannels, the electroosmotic flow(EOF) in native PMMA channels was low. DNA marker separation was demonstrated in these PMMA devices with a high-resolution separation of double-stranded DNA fragments, chip-to-chip and the run-to-run reproducibility was good, and the relative standard deviation(%) values were below 2.2% for run-to-run data and 2.3% for the chip-to-chip comparisons. The PCR amplification products and proteins were analyzed on the PMMA chips. Such devices lead to the production of low-cost, disposable chips suitable for a variety of separation applications, including DNA sizing, DNA sequencing, protein and medical analysis. The detection limits of Rhodamine 6G dye for the unmodified PMMA chip and the modified PMMA chips were 1.0×10 -10 and 6.67×10 -13 mol/L, respectively.
The interaction between domoic acid(DA) and 18-mer double-stranded DNA(dsDNA) was investigated by using microchip-based non-gel sieving electrophoresis. For the 18-mer dsDNA with a sequence of 3′-GCATTGGTTGACGTTGCA-5′, the amount of free dsDNA decreases with the increase of the added DA and also with the increase of reactive time. Meanwhile, the newly-produced two peaks were observed. The experimental results show that there is a strong interaction between DA and the 18-mer dsDNA. DA makes the degradation of the 18-mer dsDNA. The non-gel sieving electrophoresis on microchip is a rapid, convenient, highly sensitive method for studying the interaction between DNA and small molecules.
