Research On Highly Selective Imprinted Separation-diagnosis Technique Of Chiral Environmental Pollutants

It is known that chiral pollutants bring latent hazards to biological growth and environmental sustainable development, which would directly or indirectly influence on the environment or break down the ecological balance. Chiral organic pollutants in environment have been arisen much considerable concerns, especially for their latent biological effects on carcinogenicity, mutagenicity, endocrine disorder, and poisonousness. When chiral organic molecules are adsorbed by the organisms in eco-system, different enantiomers would exhibit largely discrepancies from one to another in terms of activity, metabolism, and poisonousness etc. Nowadays, a certain amount of researches have already reported about the contamination of chiral molecules, which have also shown that the racemic molecule was considered as the single compound and was ignorant to different enantiomers. When chiral compounds exist in different chiral conditions, their corresponding enantiomers would show in distinct properties. Supposing different bioactivities of these enantiomers were caused by chiral molecules which were taken into accounts of the synthesis of origanics, as a consequence, the impairment to environment would be reduced. At the same time, it would be a better way to enhancel the treatment, manipulation, and management of the environment. Thus, the researches on highly separated enantioseparation in environmental front are extremely in high demands. In order to further explain the biological effect along with performance mechanism of various chiral organic molecules among enantiomers in the environment, it is high time to establish newly developed methods with high feasibility on separation as well as analysis to enrich the research work.Molecular imprinting technique(MIT) is known as its highly specific selectivity and recognition performance. The imprinting cavities will match with target molecules via recognizing structures, size and binding sites. However, when MIT has been applied into enantioseparation and recognition, the structure and shape of imprinted cavities may br changed, which may have certain interference on imprinted polymers recognition. The 3D structure of the imprinted cavities may be slightly changed and will weaken the recognition ability after the elution and rebinding. During the recognition process of enantiomers, they will exhibit in different bioactivities that may interfere with each other severely. The common molecule imprinted sensors for chiral molecules have restrictions on the recognition for those chiral molecules that have similar structure, resemble functional groups, and negligible difference in size. Therefore, the construction of chiral molecule imprinting technique in terms of stable structure that can directly recognize target molecules basing on widespread application and specific recognition of molecularly imprinted polymers, providing feasible separation analysis methods for chiral environment pollution research is extremely important.In the assay, imidazole, benzene ring, piperazine ring, and the chiral molecule without ring were exemplified according to the induced effect produced by electrostatic attraction of cyclodextrin(CD) derivative groups, the recognition of CD host-guest inclusion, synergy regulation function effect of metal and chiral derivatives, and the specific conformation through effect of embeded DNA respectively, so as to improve the structure of polymers and recognition structures of imprinted cavities. Four different chiral molecular imprinted recognition mechanisms were proposed, which possessed advantages of specific selectivity, highly dispersion, spatial orientation structure and conformation, highly sensitivity, and wide application, providing separation and analysis methods for chiral environmental problem scientifically.1) Taking CD derivatives as the chiral spatial orientated agents to induce the orientation of some functional groups in chiral molecules. The host-guest combination ability of CD’s hydrophobic cavity can orientate spatial condition of the whole chiral molecule, leading to the spatial orientation for chiral molecules in imprinted cavities in the process of recognition. The electrostatic induction of CD derivative groups induces and orientates chiral molecular space. And mono-2-HP-6-HS-β-CD as the chiral orientation inductive agent was synthesized, with benzene ring and electron donating groups. The benzene ring of levocetrizine dihydrochloride(LEVC) was orientated due to the clathration of hydrophobic cavity in β-CD. And the induced effect, resulting from electrondrawing group of chlorobenzene as the electron donating group in LEVC, is beneficial for benzene ring to get closer spontaneously to derivative groups of β-CD. LEVC and DEVC possess different chiral spatial orientation resulting from electrostatic attraction and steric hinerance effect of mono-2-HP-6-HS-β-CD derivative groups. According to the conformation, a novel technique based on chiral spatial orientation induction effect was proposed, combined with the special recognition of MIT, in order to improve selective recognition of imprinted polymers. The assay exhibiting highly recognition for LEVC was constructed based on orientation, combining with specific recognition of MIT. The research shows that The research shows this method was highly sensitive and selectivity for quantitative analysis of LEVC in concentrations ranged from 5.0 × 10-9 mol/L to 5.0 × 10-7 mol/L with a detection limit of 8.79× 10-10 mol/L. Comparing with LEVC, the intensity of response current for DEVC only 1.07 %. It demonstrated that LEVC as well as DEVC could be separated drastically through imprinted polymers and the sensor constructed by the recognition mechanism had highly sensitivity for the determination of LEVC and interference to enantiomers. Due to the orientation effect of CD derivative groups and immobilization of hydrophobic cavity in CD, the strategy should be used in separably and recognition chiral organic compound which can be combined by host-guest inclusion in CD.2) The chiral molecularly imprinted polymers membrane was constructed through chiral molecules as the ligand to chelate metal ion to form complex, which had more recognition sites, higher selectivity, and derivatization for target molecules. A novel chiral recognition method based on chiral molecularly imprinted polymers membrane was proposed, which can recognize more complicated chiral complexes and enantiomers that were hard to distinguish. By recognized chiral complexes with more complicated structure instead of recognized chiral enantiomers with same structure. Levomisole(LMS) as the ligand can chelate copper ion to form imdazole copper complex(Cu(Im)42+). And Cu(Im)42+ was chosen as the template molecule for constructing molecularly imprinted polymers, which was superior to common approach for constructing chiral molecularly imprinted polymers membrane in terms of accuracy, recognition ability, and enantioseparation of imprinted cavities. And then enantiomers were effectively separated. The result shows that this technique was quantitatively selectivity to LMS concentrations ranging from 5.0 × 10-10 mol/L to 1.0 × 10-7 mol/L with a detection limit of 2.31× 10-10 mol/L. For same concentration, the sensor response DMS was only 5.71 % to LMS, and the Im was only about 54.4 % to LMS. It means the sensor based on LMS as the target molecule has highly selectivity and sensitivity for the determination of LMS. Meanwhile, the sensor could efficiently separated LMS from raceme, while had no recognition ability for DMS at all. Due to The selectivy improved by improving overall structure recognition of the complexity by suing derivatization methods. This method could be applicable to recognize chiral organic compounds that work with metal ions coordination reaction.3) In order to improve the spatial orientation in the recognition process of chiral molecules, the “guide loop” was added in the imprinted cavities for the complex recognition. Because CD can incorporate complex’s hydrophobic group via host-guest combination, so CD as the “guide loop” can immobilize complex’s spatial orientation on the specific space on the sensor. LMS was chosen as the ligand for chelating copper to form Cu(Im)42+. And mono-6-SH-β-CD was self-assembled on the surface of Au electrode via Au-S bond. The host-guest recognition of the CD cavity can orientate the spatial orientation of chiral complex. Complex was chosen as the template molecule for constructing molecularly imprinted polymers membrane via electrochemical approach. The results demonstrated that there is a linear relationship between response currents and LMS concentration in range from 9.0 × 10-12 mol/L to 1.0 × 10-9 mol/L, and the detection limit is 4.47 × 10-12 mol/L. The decrease of strength for sensor response to DMS was 1.11 %. It has been shown that selectivity and sensitivity of the sensor based on the LMS as the target molecule have further improved with the help of induced loop. In this assay, the chiral molecularly imprinted polymers had increasingly accurate spatial orientation recognition for LMS, indicating that LMS and DMS could be effectively separated and recognized.4) A novel chiral molecularly imprinted technique based on chiral molecular orientation by double strand DNA(ds DNA) embedding mode. And ds DNA is able to not only combine with biomolecules through embedding mode, but have effect with base pairs consisting of double strand DNA. Due to different structure of base pairs, the cavity structure of every two base pairs in ds DNA is drastically different. Consequently, the conformations of biomolecules after embedding diversified cavities are also different. In this paper, DNA embedding mode induced and immobilized spatial orientation for chiral molecules. A widespread and highly specific enantioseparation approach was investigated based on highly specific selectivity of MIT. Take D-Carnitine, the chiral molecule, for example, ds DNA was first immobilized on a gold electrode via Au-S bond. And then D-carnitine molecule was embedded between the chains of the DNA for orientation recognition. After that, D-carnitine was chosen as the template molecule for constructing the molecularly imprinted polymers membrane. The finding indicated that the proposed technology exhibited linear response to the concentration of D-Carnitine in range of 3.0 × 10-16 mol/L to 4.0 × 10-13 mol/L, with a detection limit of 2.24 × 10-16 mol/L. The findings have shown that ds DNA consisting of AA-TT base pair had highly affinity for the embedding combination of D-Carnitine. The molecularly imprinted sensor based on the D-Carnitine complexes had remarkable selectivity to D-Carnitine and sensitive response to ultra-trace D-Carnitine. And the sensor had no selectivity to L-Carnitine resulting in the highly specific recognition and determination for D-Carnitine from raceme. In addition, the approach not only has no restriction in molecular structure and functional groups, but promising applications in environmental chiral analysis.