Pre-concentration Of Biomacromolecule Based On Micro-nanofluidic Effect

As most important types of biomacromolecule, nucleic acid and protein have been the focus of the study in the life sciences. Preconcentration plays a substantial role in enhancing the detection capability of the existing methods. Nanofluidics provides a new route for the development of preconcentration methods. Particular attention has been drawn to the concentration polarization effect at the micro-nano interface due to its unique performance in on-line preconcentration of biomacromolecule from samples of limited amount.In the first chapter of this paper, ion transport phenomena in nanochannel, the concentration polarization theory, applications of the effects, particularly the latest development in the concentration of biomacromolecule were reviewed.In chapter Ⅱ, the influence of ionic strength on the concentration polarization of the negatively charged DNA at the fused silica capillary micro-nano interface was investigated by microscopic CCD imaging with two fluorescent probes-ethidium bromide (EB) and SYBR Green I. It was found that under low ionic strength (0.1×TBE) condition, the concentrated band could be steadly concentrated at the cathode; while under high ionic strength condition (1xTBE), the band could cross the interface to the anode side from time to time during the concentration process, as observed with the EB/SYBR Green I labeled DNA, FITC-BSA and small fluorescent probe molecules. The etched nanopore was also characterized by CCD imaging of the localized DNA concentration point. It was found that the etched "membrane" actually comprised of one nanopore most of the times, with few exceptions that two pores appeared at the same time. The concentration efficiency of DNA was measured by CCD imaging method. In40s, as high as105times of concentration was demonstrated for the SYBR Green I labeled2.0×10-13mol/L DNA test solution when the electric field was applied in the direction from outside to inside. In addition, concentration of DNA at the Nafion-based micro-nano interface was also demonstrated with good result.In chapter Ⅲ, DNA concentration efficiency under low ionic strength was studied by electroosmotic flow (EOF) transporting the concentration band to the laser induced fluorescence (LIF) detection window. Up to104times concentration was achieved with2.0×10-12mol/L DNA as the initial solution. Nafion-based micro-nano interface for the DNA concentration was also studied with the same method. In addition, the relationship between the resistance of the micro-nano interface and the concentration efficiency was preliminary discussed.This study showed that, the capillary-based micro-nanofluidic interface showed good concentration efficiency for both nucleic acid and protein, as characterized by fluorescent imaging and LIF detection. Therefore, the fused silica capillary based interfaces will find wide applications for the analysis of low abundance biomacromolecule from small sample.