Preparation And Properties Of Cis - Diol Molecularly Imprinted Polymers

Molecular imprinting technology (MIT) is a new field based on molecular recognition theory and has developed rapidly in recent years. Molecular imprinted polymer (MIP) prepared by the MIT is of high specific recognition ability for the target molecule, and has been successfully applied to the chromatographic separation、antibody and mimetics receptor solid phase extraction and biosensors and so on. Traditional Chinese medicine has complex system、low content of active substances, difficult extraction. The application of MIP on the extraction and separation of the active substance in traditional Chinese medicine becomes a hot research in the field of medicine.Cis-diol structure exists in many of the effective molecular structure of traditional Chinese medicine, such as, flavonoids, saponins, steroids and terpenoids and other substances. The conventional extraction method of these chemical substances are silica gel, macroporous resins, gels, chromatography in which Cis column is used as the stationary phase. However, these methods are time-consuming and have large consumption of solvents and through which many substances in low levels can not be obtained. In order to establish a efficient, simple separation method towards the cis-diol molecules, the preparation、performance characterization and the study of separation application of cis-diol structure MIP was carried out by MIT in this paper. The content of the study is divided into the following three parts.The first part:Naringin-reversible covalent MIP was prepared by using naringin (NG) as the imprinted molecule,4-vinylphenylboronic acid (VPBA) as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linking agent through bulk polymerization. The conditions when NG and VPBA was combined to form the prepolymer such as reaction time, temperature, and the reaction medium were discussed. The identification and selection properties of MIP were studied through static adsorption approach and the results showed that MIP had the identical specifical ability, while it showed poor ability to identify structural analogues. Scatchard analysis showed that MIP has formed a class of specific recognition sites and the adsorption equilibrium constant Kd=1.127mmol/L, the maximum adsorption capacity Qmax=104.66μmol/g. Kinetic studies showed that MIP in the1h reach to63%of the maximum binding capacity and reach to maximum adsorption equilibrium in3hours. The MIP was then utilized as a sorbent of solid phase extraction to extract and separate naringin from orange. The applying method, washing and elution conditions were optimized and the results showed that MIP could successfully isolate and purify naringin from the crude extracts of orange.The second part:Oridonin-reversible covalent MIP was prepared by using Oridonin as the imprinted molecule, VPBA as functional monomer, EDMA and divinylbenzene (DVB) as cross-linking agents through bulk polymerization. The synthesis conditions of preparering4-vinylphenylboronic acid ester of Oridonin such as reaction time, temperature, and the reaction medium were studied. The binding properties of MIP were studied by static adsorption method and the results showed that the MIP prepared using DVB as the cross-linking agent possessed better recognition performance than EDMA. Then, MIP was utilized as a SPE sorbent for the extraction and separation of Oridonin from rubescen and the applying、washing and elution conditions were optimized in this part. The results showed that MIP could successfully extract and isolate oridonin from crude extracts of Rubescens. The amount of Oridonin which was eluted down was74.7%of the overall adsorption amount and the purity was about96%.The third part:Two different spherical molecular imprinted polymers were prepared by utilizing naringin as imprinted molecule、VPBA as a functional monomer, EDMA as cross-linking agent by means of two methods of precipitation polymerization and living/controlled polymerization. The dosage and dosage and type of solvent of the reversible addition-fragmentation chain transfer agent were optimized. Particle sizes of MIP prepared by each polymerization method were compared through electron microscopy scanning. And the results showed that reversible covalent polymer molecules prepared by living/controlled polymerization had better adsorption performance than conventional precipitation polymerization.In this paper, Naringin and Oridonin reversible covalent imprinted polymers were prepared by bulk polymerization and exhibited stable performance, specific selectivities and identification properties to the template molecule. Moreover, those imprinted polymers had good separation effects in aqueous medium. As a new specific separation material, the MIP showed a great application value in aspects of extraction、separation and purification of the active ingredients of traditional Chinese medicine in aqueous medium. Naringin covalently imprinted polymer prepared by living/controlled polymerization exhibited better ability in adsorption than the conventional precipitation polymerization, while the great potention of it in separation application was to be studied.