Preparation And Application Of Molecularly Imprinted Polymers Based On Silica-coated Nanomaterials

This thesis is involved in the preparation and application of molecularlyimprinted polymers based on silica-coated nanomaterials. It consists of six chapters.In chapter one, the general introduction included the classification andchallenges of molecular imprinting technique （MIT）, MIT combined with thecharacteristics of nanomaterials and sol-gel technique. Additionally, the aim,significance and innovation of this thesis were also briefly presented.In chapter two, silica-coated molecularly imprinted polymer nanospheres for theselective analysis of sulfonamides in food samples were prepared. Themonodispersed SiO₂nanoparticles of diameter80nm were amino-modified byreaction with3-aminopropyltriethoxylsilane. The acryloyl monolayer was thengrafted onto the amine-modified SiO₂nanoparticles. Finally, the molecular imprintingpolymers （MIPs） films were coated onto the surface of SiO₂nanoparticles by thecopolymerization of the vinyl end groups with functional monomer, cross-linkingagent, initiator, and template molecule （sulfamethoxazole, SMO） to obtain MIPsnanoparticles for SMO （SiO₂@SMO-MIPs）. The resulted SiO₂@SMO-MIPs hadbetter site accessibility, faster binding kinetics, higher binding capacity and selectivitycompared with MIPs prepared by traditional bulk polymerization. The feasibility ofremoving SMO and sulfadiazine from food samples was proved by the use of spikedmilk and eggs. Using the SiO₂@SMO-MIPs materials as sorbents, a new off-linemolecular imprinting solid phase extraction-high performance liquid chromatographymethod was developed.In chapter three, carbon nanotubes （CNTs） functionalized with MIPs foradvanced removal of estrone were prepared. The obtained MIPs for estrone（CNTs@Est-MIPs） nanocomposites with a well-defined core-shell structure wereobtained using a semi-covalent imprinting strategy. The adsorption properties weredemonstrated by equilibrium rebinding experiments and Scatchard analysis. Theresults demonstrated that the CNTs@Est-MIPs possess favourable selectivity, highcapacity and fast kinetics for template molecule uptake. The synthetic process was quite simple, and the different batches of synthesized CNTs@Est-MIPsnanocomposites showed good reproducibility in template binding. The preparedCNTs@Est-MIPs nanocomposites exhibited high removal efficiency as a sorbent forestrone in water samples.In chapter four, molecularly imprinted polymers for triclosan on CNTs coatedwith silica （CNTs@TCS-MIPs） combining a surface molecular imprinting techniquewith a sol-gel process were prepared. The adsorption properties of the polymers weredemonstrated by a series of rebinding experiments. The prepared imprinted materialsexhibited fast kinetics, high capacity and favorable selectivity. Different batches ofCNTs@TCS-MIPs showed good reproducibility and the reusability of MIPs withoutany deterioration in capacity was demonstrated for at least six repeated cycles. TheMIPs developed could be used for the selective adsorption and determination oftriclosan from environmental matrices.In chapter five, molecularly imprinted polymers functionalized with magneticnanoparticles for the recognition and enrichment of protein were prepared. Themonodispersed Fe₃O₄nanoparticles of diameter200nm were prepared through amodified solvothermal reaction. Four proteins （bovine serum albumin （BSA, pI=4.9）,bovine hemoglobin （BHb, pI=6.9）, ribonuclease A （RNase A, pI=9.4） andlysozyme （Lyz, pI=11.2）） with different isoelectric points were chosen as thetemplates. The magnetic protein-MIPs were synthesized by combining surfaceimprinting with a sol-gel process based on covalent template immobilization on thesurface of Fe₃O₄. The adsorption ability of different magnetic protein-MIPs torelevant template proteins were all higher than for the other three proteins. Therefore,this general method studied in this paper was proven to be amenable to different kindsof proteins with different isoelectric points. The magnetic MIPs of BHb （Fe₃O₄@BHb-MIPs） showed the best imprinting effect and the highest adsorption capacity amongthe four proteins. The resulted Fe₃O₄@BHb-MIPs could not only selectively extract atarget protein from mixed proteins but also specifically capture the protein BHb froma real sample of bovine blood.In chapter six, thermosensitive molecularly imprinted polymers functionalizedwith magnetic nanoparticles of BSA for the recognition and enrichment of human serum albumin （HSA） were prepared. The main monomer N-isopropylacrylamidewas introduced as a thermosensitive element. BSA was chosen as dummy templatefor HSA. The MIPs films were coated onto the surface of Fe₃O₄by thecopolymerization of the vinyl end groups with functional monomer, cross-linkingagent （N, N-methylenebisacrylamide）, initiator （ammonium persulfate）, and templatemolecule to obtain MIPs of BSA （Fe₃O₄@BSA-MIPs）. The conditions ofpolymerization, adsorption and elution was systematically investigated. Fe₃O₄@BSA-MIPs possessed easy accessibility to the recognition sites and showed fastkinetics, high capacity and favorable selectivity. Fe₃O₄@BSA-MIPs could not onlyrespond to temperature and ionic strength, and achieve adsorption-desorption cyclesthrough changing the temperature, but also be successfully applicated in the selectiveenrichment of BSA or HSA from mixed proteins and bovine blood or human blood.