Fabrication Of Chiral Selectors On The Functionalized Magnetic Microspheres For Chiral Recognition Of Amnio Acids

Amino acids, as indispensable organic compounds of people and animals, play a crucial role in catalysis, immunity and metabolism and were applied in food additives, drug synthesis, agricultural chemicals, cosmetics, chemical industry and biological engineering. The two isomers (D-amino acids and L-amino acids) of amino acids have dramatic different bioactivity in stereo environments, sometimes with deleterious effects. Hence, the analysis and separation of amino acids is significantly important not only for people’s safety and health but also for others important areas, such as bioscience. Currently, a number of complicated methods are unusually limited to the analytical scale, cost and separation speed. The development of fast, low cost and efficient methods are important and urgent for the chiral separation of chiral compounds.Magnetic nanoparticles, as ideal carriers, was widely applied to a range of disciplines, including bioseparation, sample pretreatment, enzyme immobilization, environmental protection and drug delivery because of the remarkable advantages of their size, specific surface area, biocompatibility and magnetism. In this thesis, we are focusing on the preparation, characterization and application of chiral selector functionalized magnetic microspheres based on Fe3O4. A facile, fast and low cost analytical method for chiral recognition of amino acids was initially established, which will lay the foundation for online chiral separation based on combination of chiral selector functionalized magnetic microspheres and capillary electrophoresis. The major researcher works are as follows:(1) Fe3O4 magnetic microspheres prepared by hydrothermal synthesis was sequentially modified with SiO2 and N,N’-methylene bisacrylamide through Stober and ditillation precipitation polymerization approach. The chiral selector functionalized magnetic microspheres were prepared by grafting maleric anhydride-p-cyclodetrin (MAH-β-CD) onto the surface of the above magnetic microspheres. The chiral recognition ability of MAH-P-CD-modified magnetic microsphere was evaluated by interacting with amino acids and chiral drug. The experimental results indicated the prepared MAH-β-CD-modified magnetic microspheres show a three-layer structure, well dispersion, narrow diameter distribution, strong magnetic responsiveness and high immobilization amount. At the same time, the MAH-P-CD-modified magnetic microspheres could selectively interact with four chiral compounds and indicate some chiral discrimination ability, which are candidates for the future research on chiral separation.(2) β-CD-epichlorohydrin (P-CDEP) polymers were synthesized by the polymerization of β-CD with epichlorhydrin, which were added into hydrothermal synthesis reaction to prepare P-CDEP-modified Fe3O4 microspheres. The amount of β-CDEP and the reaction time were varied to investigate the formation mechanism of the functionalized magnetic microspheres. The results suggested that the P-CDEP polymers were as surfactants against particle agglomeration and promoted the growth of Fe3O4 crystalline grains. The P-CDEP-modified Fe3O4 microspheres were used to direct chiral selectively absorb DL-tryptophan solution. Under the optimum adsorption time and pH, the supernatant enantiomeric excess of DL-tryptophan was 44.2% after interaction with 300 mg P-CDEP-modified Fe3O4 microspheres. The β-CDEP-modified Fe3O4 microspheres have some chiral separation ability, which could be used as a stereoselective absorbent and easy for mass production.(3) Polyamidoamine dendrimer (PAMAM) was bonded onto the surface of magnetic microspheres with microwave irradiation. A novel chiral selector functionalized magnetic microspheres was prepared by immobilizing L-Valine (L-Val) onto the synthesized PAMAM-modified magnetic microspheres and used to directly chiral separate amino acid derivate. The interaction times and the amount of the novel functionalized magnetic microspheres were optimized. The analysis results indicated that the novel functionalized magnetic microspheres have clearly and regularly core-shell structure and the introduction of PAMAM onto the surface of magnetic microspheres could obviously improve the immobilization amount of L-Val. Moreover, the immobilization amount of L-Val increase with increasing of the PAMAM generation. The L-Val grafting on 3 generation PAMAM-modified magnetic microspheres selectively interact with dansyl DL-phenylalnine based on ligand exchange principle, which indicate that the novel functionalized magnetic microspheres possess well chiral separation ability. The experiment also lay the foundation for online chiral separation through fixing chiral selector functionalized magnetic microspheres onto the inner wall of fused-silica capillaries with the help of external magnetic field.