Fabrication Of Acrylonitrile-based Glycopolymer/MWCNTs Nanofibers For Enzyme Immobilization

Glycopolymer refers to a sugar-based functional polymer by means of polymerization of a low molecular compound and a sugar-based unsaturated monomer. Because of the sugar composition contains abundant hydroxyl, which can improve the hydrophilicity, biocompatibility and biodegradability of polymers, glycopolymers have been more and more used in biological, pharmaceutical, etc. Introducing sugar group into hydrophobic materials can effectively improve their hydrophilicity, and then broaden their application areas.We chose glucose as a model in the thesis, developing a simple and convenient method for the preparation of glycopolymer nanofibers. Firstly, the acrylonitrile-based copolymer containing glucose Poly(AN-co-OVSEG) was prepared by enzymatic synthesis and water phase precipitation. The structure of the glycopolymer was confirmed by FT-IR and1H NMR. Then the Poly(AN-co-OVSEG) nanofibers and Poly(AN-co-OVSEG)/MWCNTs composite nanofibers were prepared by electrospun method. The nanofibers were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). And the biocompatibility of nanofibers was proved by water contact angle measurement and BSA adsorption experiment testing. On this basis, the nanofibers were used for studying behavior of enzyme immobilization. More in details are as follows:(1) Preparation of the acrylonitrile-based glycopolymerThe chemo-enzymatic method was introduced to synthesis glucose vinyl esters, and then the glycopolymer Poly(AN-co-OVSEG) was synthesized by a water phase precipitation polymerization process. Through studying of the initiator concentration, monomer concentration, reaction temperature, reaction time on the polymerization reaction, the polymerization conditions were optimized. The structure of product was characterized by infrared spectroscopy (FT-IR), nuclear magnetic resonance hydrogen spectrum (1H NMR,) methods. And molecular weight was confirmed by the gel permeation chromatography characterization.(2) Preparation of Poly(AN-co-OVSEG) nanofibersThe Poly(AN-co-OVSEG) nanofibers were prepared by electrospinning technique. Through the studying of the spinning conditions (solution concentration, applied voltage, receiving distance, speed) effect on the fiber morphology, the optimum electrospinning parameters are given as Poly(AN-co-OVSEG) concentration of30wt%, applied voltage of14KV, needle to collector distance of15cm,solution flow rate of0.5mL/h. The diameter and morphology of Poly(AN-co-OVSEG) nanofibers were characterized by scanning electron microscope, showing the fibers,which were obtained under the optimum conditions,were even thickness with an average diameter of146nm. The biocompatibility of nanofibers was proved by water contact angle measurement and BSA adsorption experiment testing. The experimental results show that with the increase of sugar content in the polymer, the contact angle of nanofibers reduced from65.5°of polyacrylonitrile nanofibers to49°; BSA adsorption capacity decreased from0.32g/m2to0.16g/m2. Through the above experiments we show that the biocompatibility of acrylonitrile-base glycopolymer has been improved.(3) Preparation of Poly(AN-co-OVSEG)/MWCNTs nanofibersUnder the optimum conditions, the Poly(AN-co-OVSEG)/MWCNTs composite nanofibers with different MWCNTs contents were prepared by electrospinning technique. The morphology of Poly(AN-co-OVSEG)/MWCNTs nanofibers was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The influences of MWCNTs content on the hydrophilicity and mechanical property of the composite nanofibers were studied. The experimental results showed that with the increase of MWCNTs content, the hydrophilicity of materials increased; The best mechanical property was appeared as the MWCNTs content of2%, next by was1%. SEM results show that when the MWCNTs content exceeds1%, there were obvious beaded structures taken place in the nanofibers. Thus, when the MWCNTs content was1%, the comprehensive performance of the nanofibers was best.(4) Immobilization of enzymeWith epichlorohydrin as the coupling agent, the catalases were fixed onto the Poly(AN-co-OVSEG) nanofibers and Poly(AN-co-OVSEG)/MWCNTs composite nanofibers. Immobilization of catalase was carefully studied, including the amount of immobilized catalase, the activity, the kinetic parameters and the stability. It was found that, the extremely high surface area to volume caused large amount of immobilized enzyme. Besides, carbon nanotubes have excellent electrical conductivity, as electron transfer media to effectively promote electron transfer. The filling of MWCNTs greatly enhanced the retention activity of the immobilized enzyme.