Studies On Selective Recognition Behaviour And Mechanism Of Environmental Endocrine Disruptors By Molecularly Imprinted Sensors Based On Fluorescent Monomers

With the expansion and development of industry and agriculture, the harmfulness from phenolic endocrine disruptors(PEDs) and Pyrethroid pesticides(PPs) for human and animal reproductive system, immune system and nervous system have become more and more serious, resulting in decreased reproductive function, low immunity, nervous system damage and endocrine disorders, and even induce malignant tumor. While PPs are used to control target biological pest, also produce toxic effects on non-target aquatic organisms, such as the honeybee, silkworm, insects, fish, shrimp, crab, shellfishs. In view of the environment, for the complex, similar structure, trace/ultra-trace PPs and PEDs, we need to explore new recognition method, improve the recognition efficiency and selectivity, enhance signal sensitivity, and establish a fast and sensitive detection mechanism.In this study, a novel recognition and detection technique of λ-cyhalothrin(LC) and 2,4,6-trichlorophenol(2,4,6-TCP) residues will be investigated, which contains selective recognition and analysis, by fitting Fluoresce Detection Technique(FDT) and Molecular Imprinting Technique(MIT) together in this project. Fluorescent dyes are attractive candidates as fluorophors in MIP system owing to their good photophysical properties, such as narrow emission spectrum and high quantum efficiency. Briefly, the highly selective fluorescent molecularly imprinted polymer(MIP) sensors will be fabricated as a rapid, sensitive and accurate detection model, and used to selectively recognize/detecte environment pollution residues.The main conclusions included the following items:(1) Synthesis and characterization of fluorescent dye monomersThree dye monomers functioned by allyl groups, whose names are allyl fluorescein, 7-allyloxycoumarin and 4-allyloxycoumarin respectly, have been prepared. And the structure and fluorescence properties of the three dyes are characterized. The results show that the structures of the three dyes are completely consistent with the expected, and have very strong fluorescence emission properties, which are conducive to the application of fluorescent molecular imprinting sensor.(2) Preparation of fluorescent molecular imprinting sensors used for fluorescence detection of LC and 2,4,6-TCP(a) A fluorescent molecularly imprinted polymer(FMIP) sensor is fabricated via precipitation polymerisation. The MIP sensor is prepared upon copolymerisation of acrylamide with a small quantity of allyl fluorescein in the presence of LC to form recognition sites. The as-synthesised microspheres exhibited spherical shape, high fluorescence intensity and highly selective recognition. Under optical conditions, polymer microspheres are successfully applied to selectively and sensitively detect LC, and a linear relationship described by the Stern-Volmer equation(I0/I) – 1 = 0.29·CC-0.00608 with a correlation coefficient of 0.9936. A lower limit of detection(LOD) is found to be 0.004 n M. The results of practical detection suggested that the developed method is satisfactory for determination of LC in honey samples. The FMIP sensor has certified that they can be reused for not less than 5 times without remarkably loss of signal intensity.(b) An approximately fluorescent sensor based on MIP is synthesized by precipitation polymerization using 2,4,6-TCP as template, 7-allyloxycoumarin as functional monomer. The resulting fluorescent molecularly imprinted sensors are monodispersed spheres and strongly blue fluorescence. This fluorescent sensor displays a quenching of fluorescence in the presence of 2,4,6-TCP in ethanol, even almost no effect is observed in the presence of its structural analogs, such as 2,4-dichlorophenol(2,4-DCP), 2,5-dichlorophenol(2,5-DCP) and 2,6-dichlorophenol(2,6-DCP). The fluorescence of the fluorescent sensor is quenched specifically by 2,4,6-TCP by solid fluorescence detection. The linear range described by the Stern-Volmer equation is(I0/I) – 1 = 0.01482·CC- 0.01022,R2 = 0.99859. LOD is 0.013 n M.(c) A FMIP sensor is prepared by precipitation polymerization using 2,4,6-TCP as template, 4-allyloxycoumarin as functional monomer. The FMIP sensors are monodispersed spheres and strongly blue fluorescence. This fluorescent sensor shows quenching of fluorescence toward 2,4,6-TCP in ethanol, even almost no effect is observed in the presence of its structural analogues, such as 2,4-DCP, 2,5-DCP and 2,6-DCP. The fluorescence of the fluorescent sensor is quenched specifically by 2,4,6-TCP by solid fluorescence detection. The linear range described by the Stern-Volmer equation is(I0/I) – 1 = 0.0096·CC- 0.0132,R2 = 0.99905. LOD is 0.072 n M. The results of practical detection suggested that the developed method is satisfactory for determination of LC in honey samples. The fluorescent MIP sensor has certified that they can be reused for not less than 5 times without remarkably loss of signal intensity.(3) Core-shell structure fluorescent surface molecular imprinting sensors and the application for fluorescence detection of LC and 2,4,6-TCP(a) Si O2@FMIP sensor based is fabricated via precipitation polymerisation and MIT for selective detection of ultra trace LC in honey. The sensor is prepared via copolymerization of acrylamide with allyl fluorescein in the presence of LC to form recognition sites. The experimental results showed the fluorescence quenching of Si O2@FMIPs for LC are much higher than that of the structurally analogue composite. In addition, a linear relationship described by the Stern-Volmer equation(F0/F) – 1 = 0.16037·C- 0.01611·C2- 0.00237 with a correlation coefficient of 0.99698. A lower limit of detection is found to be 0.05 n M.The results of practical detection suggested that the developed method is satisfactory for determination of LC in honey samples. This study therefore demonstrated the potential of Si O2@FMIPs sensor for the recognition and detection of LC in food. The Si O2@FMIPs sensor has certified that they can be reused for not less than 5 times without remarkably loss of signal intensity.(b) A highly selective and sensitive molecular imprinted polymer sensor suitable for fluorescence detection of LC samples has been successfully fabricated by atom transfer radical polymerization. The structure, sharp, photophysical properties are descripted detailed. The selective, interfere, range, LOD have been discussed. The linear relationship is described by the Stern-Volmer equation(I0/I)- 1 = 0.00322·Cc + 0.03223 with a correlation coefficient of 0.99698. LOD is found to be 0.0037 n M. Different analogue compounds existing are used to examine the selectivity of the as-fabricated sensor, and no obvious fluorescence change could be observed in these interferes and their mixtures. The excellent performance of the proposed sensor and satisfactory results of LC suggested that Si O2@FMIP sensor for the determination of LC will be a good candidate as a new technique.(c) The molecularly imprinted sensors were used to selectively detect 2,4,6-trichlorophenol(2,4,6-TCP) by solid fluorescence detection without dispersion solution. Moreover, the selectivity and interference abilities of Si O2@FMIPs sensor appease the desires of a fluorescent sensor. The novel fluorescent monomer introduced into MIP is on longer just as a fluorophor without recognizing analyte. The fluorescence intensity of Si O2@FMIPs showed a linear response to 2,4,6-TCP concentration range of 0 – 100 n M with a detection limit of 0.0534 n M. The linear relationship is described by the Stern-Volmer equation(F0/F)-1 = 0.01051·C + 0.00582, with a correlation coefficient of 0.99947.(d) The sensor was used to selectively detect 2,4,6-TCP by solid fluorescence detection without dispersion solution. Moreover, the selectivity and interference abilities of sensor appease the desires of a fluorescent sensor. The novel fluorescent monomer introduced into MIP is on longer just as a fluorophor without recognizing analyte. The linear relationship is described by the Stern-Volmer equation(F0/F)-1= 0.00918·C + 0.00522,R2 =0.99922,LOD = 0.0614 n M。.(e) A core-shell magneticthe Fe3O4@Si O2-MPS@MIP sensor is fabricated via a surface molecular imprinting technique for optical detection of trace LC on the surface of Fe3O4@Si O2-MPS. The fluorescent molecularly imprinted polymer shell is first prepared by copolymerization of AM with a small quantity of allyl fluorescein in the presence of LC to form recognition sites. The magnetic Fe3O4@Si O2-MPS@MIP exhibited paramagnetism, high fluorescence intensity, and highly selective recognition. Using fluorescence quenching as a detecting tool, Fe3O4@Si O2-MPS@MIP are successfully applied to selectively and sensitively detect LC, and a linear relationship could be described by the Stern-Volmer equation(I0/I)-1=0.01289·Cc – 0.02365 with a correlation coefficient of 0.9962. The experimental results of practical detection revealed that magnetic Fe3O4@Si O2-MPS@MIP as an attractive recognition element is satisfactory for determination of trace LC in honey samples. This study, therefore, demonstrated the potential of MIPs for detection of LC in food.