Studies On Preparation And Characterization Of Molecularly Imprinted Polymers/Membranes About Podophyllotoxin And Indirubin Based On New Functional Monomers

Molecular imprinting technique (MIT) is a technology developed on the basis of the bionic science, as well as the simulation of enzyme-substrate and antigen-antibody interactions in the nature. By introducing imprinting molecular recognition sites analogous to the natural effects of molecular recognition, a molecularly imprinted polymers/membranes (MIP/MIM) with spatial binding sites is artificially synthesized to achieve the specific selectivity to the target molecule (template molecule). With the development of the research and application concerning MIT, this technique has been widely used in many fields, such as the chiral separation, solid phase extraction, sensors, catalysis, organic synthesis, and so on. However, there are a number of unresolved problems in the MIP/MIM researches waiting for further efforts. One of them is that, while the template molecules are relatively diverse in terms of the types and structures, the number of available functional monomers is limited in the preparation of MIP/MIM. And there are few reports on the design and synthesis of new functional monomers up to now. Consequently, it is unable for the MIPs or MIMs to meet the requirements of recognition for template molecules with a wide range of molecular types and chemical structures.The goal of this paper is to design and synthesize a number of novel monomers applicable to molecularly imprinted systems by the non-covalent imprinting method, and use them to prepare MIPs/MIMs specific to target molecules including podophyllotoxin and indirubin. After optimizing the conditions of preparation and testing the performance, the optimum MIP or MIM with suitable functional monomer was finally selected and used in the enrichment and separation of active components in complex samples. The recognition mechanism of MIP/MIM was further speculated. This study laid a solid foundation for the applications of these new functional monomers in preparation of functional materials, as well as the applications of this group of MIP/MIM for the separation of complex samples. The details of this research work are as follows: Fourteen novel functional monomers belonging to three types, i.e. lactam functional monomer, chiral functional monomer, and functional monomer with β-keto ester structure or β-amino ester unit, were designed and synthesized for specific target molecules including podophyllotoxino, indirubin, etc. Their structures were identified by1HNMR and13CNMR spectra.The self-designed compounds (1-12) were synthesized and used as functional monomers for the preparation of MIPs for podophyllotoxin (PPT). The preparation methods and conditions of MIPs for podophyllotoxin were optimized. The optimal conditions for preparation of polymers are as follow: the compound2used as the functional monomer, chloroform as the porogenic solvent, ratio of template molecule to functional monomer to crosslinker as1:4:20. The equilibrium binding experiments show that the molecularly imprinted polymer prepared in chloroform (MIP14) has a larger adsorption capacity and higher imprinting factor. As a result, MIP14was successfully used as an adsorbent in the solid-phase extraction for PPT in the complex sample solution. In addition, a series of molecularly imprinted composite membrane (MICMs) for PPT were also prepared by the surface grafting method (surface imprinting method). The effects of the amounts of functional monomer and crosslinker, the type of base membrane, soaking-time and other factors on the adsorption properties of PPT were investigated. The equilibrium binding experiments indicated that the MICM2prepared using the functional monomer1-phenyl-3-methyl-4-methyl propylene acyl-5-Pyrazoline ketone (PMMP) has a higher adsorption capacity and imprinting factor. Permeation experiments showed that, in the presence of its analogue DMEP, the optimum membrane MICM2exhibited a good permeating selectivity to the template molecule PPT. Especially, it was found that MICM2has good pH sensitivity (pH-responsibility) in the permeating tests. The structural characteristic of MICM2was investigated by scanning electron microscopy (SEM) and nitrogen adsorption method. Finally, the separation and enrichment capacity of MICM2in PPT-and DMEP-methanol mixture and actual samples of methanol extracts of Himalayan mayapple was also examined by ultra-high performance liquid chromatography (UPLC) method. Compounds (1-12) were also used as the functional monomers for the preparation of MIPs for indirubin. The optimal experimental conditions of preparation of MIPs were determined as follow:Silica gel as sacrificial material, compound4as the functional monomer, THF as the porogenic solvent, ratio of template molecule to functional monomer to crosslinker as1:4:30. Moreover, methacrylic acid (MAA), acrylamide (AM) and4-vinylpyridine (4-VP) were used as functional monomer to prepareMIPs for indirubin, respectively. The equilibrium adsorption experimental studiesshowed that, compared with the general functional monomer MAA AM and4-VP, the MIP20prepared with the compound4as the functional monomer had a larger imprinting factor and adsorption capacity for indirubin. This implied that compound4is a suitable functional monomer for the template molecule indirubin. Using MIP20as sorbent in solid phase extraction micro-column (MISPE), indirubin was successfully separated and enriched from real sample solution. Amounts of functional monomer and crosslinker, the types of base membrane, soaking time duration and other factors were taken into account, a series of indirubin imprinted composite membrane (MICMs) and the control NICMs were also prepared. The selectivity of the optimum membrane (MICM20) in the standard mixture of indirubin and indigo, and in the sample solution of methanol extract of Radix Isatidis was investigated. The results of permeating experiments showed that MICM20is capable of enriching indirubin in complex solution.