Preparation Of Hyperbranched Polyamide Ester And Its Application For Modifying Polymer Microfluidic Chip

Microfluidic chip technology has become a research focus and frontier in the field of life science. Polymethyl methacrylate (PMMA) microfluidic chips based on their remarkable transmittance and low cost has widely used in bio-molecular analysis. But, the surface of PMMA microfluidic chips was extremely hydrophobic, which could adsorb bio-molecules and resulted in poor analysis results. In order to make up for defects of PMMA microfluidic chips, the chips were modified using hyperbranched polyamide ester based on its characteristics of three-dimensional spherical structure, a large number of active terminal hydroxyls and low viscosity. The purpose of the modification is to improve the hydrophilicity of the chips' surface, inhibit the adsorption of bio-molecules and thus improve the analytical performance of chips.The research content mainly includes the following aspects:(1) Synthesis and characterization of hyperbranched polyamide ester AB₂-type monomer containing one carboxylic group and two hydroxylic groups was prepared using succinic anhydride and diisopropanolamine via michael addition reaction, then the hyperbranched polyamide ester was synthesized via the polycondensation between the AB₂-type monomer and pentaerythritol as a core molecule. The products were characterized by IR, ¹³C-NMR, GPC, TGA, hydroxyl value measurement and viscosity analysis. The result showed that the hyperbranched polyamide ester synthsized had narrow molecular weight distribution and high degree of branching, a large number of terminal hydroxyls, low viscosity and good thermal stability, thus was was a promising modification-material.(2) Surface modification of PMMA microfluidic chipsThe surface of PMMA microfluidic chips were modified using hyperbranched polyamide ester via chemical bonding and physical coating. The contact angle of the chips after modification was measured. The surface morphology of modified chips was observed using SEM and stereo microscope. The electroosmotic flow and stability of hydrophilic coating were also investigated. The result showed that the surface of modified chips possessed a layer of dense, uniform, continuous hydrophilic coating. Hydrophilicity of the chip surface has been markedly improved. The contact angle of chips modified via the chemical bonding decreased from 89.9°to 29.5°. It was also found the hydrophilic coating was very stable.(3) Analysis of bio-molecules using PMMA microfluidic chips after modificationThe adenosine and L-lysine were separation and detection via PMMA microfluidic chips modified by chemical bonding and physical coating. Firstly, the optimal detection conditions were established. Phosphate buffer concentration 40mmol/L, pH4.8, separation voltage 8kV and detection wavelength 214nm. The result showed that the unmodified chips could't effectively separate two bio-molecules and the serious adsorption phenomenon occurred. Compared with unmodified chips, the modified chips successfully separated two bio-molecules. The two detection peaks obtained were separated clearly and the shape of the peaks was sharp. The separation efficiency of adenosine and L-lysine using the chips modified via chemical bonding was 8.44×10⁴Plates/m and 9.82×10⁴Plates/m, respectively and the resolution (Rs) was 5.31. The separation efficiency of two bio-molecules using the chips modified via physical coating was 7.19×10⁴Plates/m and 8.11×10⁴Plates/m, respectively and the resolution (Rs) was 4.03. The separation efficiency and resolution of modified chips were both much higher than the unmodified chips. It was also observed that the modified chips possessed good migration time reproducibility and long service life.