| Uremia is one kind of diseases which threatens seriously the life of patients. when kidney failure occurs, there is a great deal of accumulations of uric acid in the blood. Via blood purification, the accumulation of uric acid can be removed effectively and alleviated the symptoms of patients. Except dialysis technique, hemoperfusion is another new technique to purify blood. The key of hemoperfusion technique is the adsorbent with high efficiency, great adsorption amount and blood compatibility. The main contents of this paper is preparing the uric acid imprinted materials which used a biocompatible cross-linked polyvinyl alcohol microspheres as a substrate,and researches the adsorption character and mechanism. With a view to the introduction of molecularly imprinted materials, which can provide an important reference and basis for the blood purification treatment.Crosslinked polyvinyl alcohol (CPVA) microspheres were prepared via direct crosslinking and balling reaction of polyvinyl alcohol with glutaraldehyde as crosslinker in a reverse phase suspension system. The graft polymerization of acrylonitrile on CPVA microspheres was performed in an acidic solution polymerization system by using cerium ammonium sulfate as initiator, and grafted microspheres PAN/CPVA were prepared. The chemical structure were adequately characterized with infrared spectrum (FTIR) and scanning electron microscope (SEM). The experimental results show that in the direct crosslinking and balling system, the used amount of disperser and the ratio of oil phase to water phase are two main factors which affects thegrain size of crosslinked microspheresCPVA. The radical graft polymerization of PAN on CPVA microspheres initiated by cerium salt can be realized smoothly because free radicals will be produced on the surface of CPVA microspheres by the cerium salt oxidation of hydroxyl groups on CPVA. The reaction temperature, the concentration of the initiator and the H+ concentration,all of them have obviously affects the graft degree of PAN. Under suitable conditions(T=45℃,the concentration of the initiator=6.7×10-3mol·L-1,H+ concentration=0.34mol·L-1),the grafted microspheres PAN/CPVA with a graft degree of 27g/100g can be obtained.The grafted PAN was converted into poly(amidoxime) (PAO) via amidoximation reaction with hydroxylamine hydrochloride as reagent, resulting in the functional microspheres PAO/CPVA. The chemical structure and physicochemistry characters of two kinds of microspheres were adequately characterized with infrared spectrum (FTIR), scanning electron microscope (SEM) and determining Zeta potential. The effects of main factors on the amidoximation transform reaction of the grafted PAN were researched with emphasis. The experimental results show that in the midoximation transform reaction of cyanogen groups, medium pH and reaction temperature are two main factors. For this system, the adequate pH value and temperature are 6-7 and 70℃. Under the fitting conditions, the conversion ratio of the cyanogen group of the grafted PAN reaches 72% for 4h.In order to lay the foundation for the implementation of uric acid in molecular imprinting, the adsorption capacity and adsorption mechanism of PAO/CPVA for uric acid is further studied. The experimental results show that the microspheres PAO/CPVA have strong adsorption ability for uric acid. The influence of various factors on adsorption capacity is studied, and the conclusion about the adsorption mechanism is: the adsorption driving force of PAO/CPVA towards uric acid should be the synergy of electrostatic interaction and hydrogen bonding. The isothermal adsorption is accorded with Freundlich equation, and the saturated adsorption amount is able to reach 95 mg·g-1. The pH value,the reaction temperature,and the concentration of Nacl can exert great effect on the adsorption property of PAO/CPVA. MIP-PAO/CPVA is prepared with uric acid as a template molecule and glutaraldehyde as crosslinking agent, and by right of the intermolecular hydrogen bond and electrostatic interactions between the grafted PAO macromolecules and uric acid molecules. The binding character of MIP-PAO/CPVA towards uric acid molecules was studied in depth with both batch and column methods and using guanine as a contrast compound whose chemical structure is similar with uric acid to a certain extent. The experimental results show that the surface-imprinted material MIP-PAO/CPVA has excellent binding affinity and recognition selectivity for the template molecule, uric acid. The selectivity coefficient of PAO/CPVA microspheres (non-imprinting material) for uric acid relative to guanine is only 1.2732, and very poor recognition selectivity for uric acid is displayed. However, after imprinting, the selectivity coefficient of MIP-PAO/CPVA in respect to guaninel is remarkably enhanced to 14.0035, displaying the excellent recognition selectivity and binding affinity of the surface imprinting material MIP-PAO/CPVA towards uric acid molecules. Besides, MIP-PAO/CPVA microspheres have fine desorption property.
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