Study Of Molecular Interaction And Preconcentration Based On Capillary Electrophoresis And Microfluidic Chip

Capillary electrophoresis (CE) and CE based microfluidic chip fit for the bioanalytical chemistry quite well by right of their unique characteristics of micromation, automation, high efficiency and portability. This work has done some meaningful exploration on some key problems within this field.Two double stranded DNA (dsDNA) with different central base pairs were designed to systematically investigate the binding affinity and sequence specificity of berberine with dsDNA by capillary zone electrophoresis (CZE). The data analysis with the Kenndler model proved only low affinity between dsDNA and berberine and suggested some weak binding preference of berberine for AATT-containing to GGCC-containing dsDNA. The binding constant, Ka, between berberine and the former one is about (1.0±0.7)×103L/mol. In addition, the separation of single-stranded DNA (ssDNA) from dsDNA under simple electrophoretic conditions enabled CZE to be a potentially alternative tool to check the extent of DNA annealing, which is usually done by the time-consuming and labor-intensive slab electrophoresis. Besides, we compared the electrophoretic behaviors of dsDNA in an uncoated capillary and in a linear polyacrylamide coated capillary and the results suggested that there was a strong adsorption of dsDNA to the inner wall of uncoated capillary. All these above prove that the coated capillary has a large advantage in analyzing samples of this kind.The characteristic of micromation has put forward a higher requirement to improve the detection sensitivity of microfluidic chip. One of the most effective methods is to carry out sample preconcentration before analysis. The polycarbonate membrane with nanochannels created by track-etch treatment (PCTE) was electroless plated with Au in order to reduce the nanochannel ID and change the charge condition of the membrane surface. SEM and TEM were used to characterize the morphologies of the membrane surface and theinner wall of the nanochannels after electroless plating, where cigar-shaped nanochannels were observed with bottlenecks at both ends but a large ID in the middle. After an hour of plating, the ends ID of the nanochannel, which were 100nm originally, were soon reduced to about 30nm and then slowed down. Photolithography and injection molding were employed to fabricate a microfluidic chip with a polydimethylsiloxane (PDMS) cover plate and a glass bottom plate and an electroless plated PCTE membrane sandwiched between them. This microfluidic chip was later used in preconcentrating the sample of allophycocyanin (APC). By combining the confocal laser induced fluorescence detector and simple bias switching method with the microfluidic chip, an enrichment factor of almost 80 was quickly obtained within 90s. Further experiments were also done to measure the influence of the eluting bias on the APC eluting peak, which proved a molecular size based enrichment mechanism.