Preparation And Application Of Magnetic Carbon Nanotubes Composite Carrier

Carbon nanotubes?CNTs?with unique hollow tubular structure and excellent property are widely used in mechanical,catalytic and environmental fields.With the deepening of researches,scientific researchers have committed to using CNTs as base material to produce multifunctional carbon nanotube composite materials by combining CNTs with other high-property materials,which brings new development and benefits to fields of environment,biology and medicine.Based on the magnetic property of magnetic materials,this paper mainly studied the preparation of magnetic carbon nanotubes composites and its application in enzyme immobilization and antimicrobial fields.?1?Magnetic carbon nanotubes?Fe₃O₄/CNTs?were prepared by modified hydrothermal method.The effects of oxidation time and hydrothermal reaction time on the morphology of Fe₃O₄/CNTs were investigated.And the property of Fe₃O₄/CNTs was studied by employing characterization methods of FT-IR,XRD,VSM etc.The experimental results showed that,under the optimum conditions of oxidation time 4 h and hydrothermal reaction time 12 h,Fe₃O₄/CNTs exhibited good dispersity and Fe₃O₄ in Fe₃O₄/CNTs had superparamagnetic and strong magnetic properties.?2?On that basis,Fe₃O₄/CNTs were modified with silane coupling agent to prepare silane coupling agent-modified magnetic carbon nanotubes composites?AP-Fe₃O₄/CNTs?and then the property of AP-Fe₃O₄/CNTs was studied by means of FT-IR,UV-vis,Mapping,XRD,XPS and VSM.In this paper,AP-Fe₃O₄/CNTs was selected as the immobilized enzyme carrier to immobilize horseradish peroxidase and applied to the biodegradation of phenol.The effects of glutaraldehyde concentration,glutaraldehyde activation time and enzyme cross-linking time on enzyme activity and loading rate were investigated.The experimental results showed that the immobilized enzyme had the optimum catalytic activity when glutaraldehyde concentration was 1%?to total system mass?,glutaraldehyde activation time0.5 h,and enzyme crosslinking time 1 h.Compared with the free enzyme,the AP-Fe₃O₄/CNTs immobilized enzyme prepared under the optimum process conditions was enhanced in temperature and pH durability.After the catalytic reaction had repeated six times,the enzyme activity was still up to 65%?initial enzyme activity?.When the AP-Fe₃O₄/CNTs immobilized enzyme was stored for 25 days,its enzyme activity still reached the initial 67%.?3?Based on its good adsorption performance and biocompatibility,chitosan was selected in the surface functionalization of Fe₃O₄/CNTs to prepare chitosan-modified magnetic carbon nanotube composite?CTS-Fe₃O₄/CNTs?which was applied to degradation of phenol by immobilized enzyme.The results indicated that the optimum conditions for immobilized enzyme were glutaraldehyde concentration 1%?to total system mass?,glutaraldehyde activation time 1 h,and immobilized enzyme cross-linking time 1 h.Due to the carrier's protection of enzyme active site,the CTS-Fe₃O₄/CNTs immobilized enzyme prepared under the optimum conditions was resistant to high temperatures,acid and alkali condition.After six times of catalytic reaction,the enzyme activity remained at the original80%.When the CTS-Fe₃O₄/CNTs immobilized enzyme was stored for 25days,the enzyme activity still maintained at the original 65%.The above results indicated that the storage stability of CTS-Fe₃O₄/CNTs immobilized enzyme was similar to that of the AP-Fe₃O₄/CNTs immobilized enzyme,while the CTS-Fe₃O₄/CNTs immobilized enzyme could maintain a relatively high enzyme activity after repeated catalysis for the same number of times.Therefore,CTS-Fe₃O₄/CNTs was more suitable as immobilized enzymes carrier.?4?Magnetic carbon nanotubes composite AP-Fe₃O₄/CNTs and CTS-Fe₃O₄/CNTs were used as the carriers to carry out loading experiment of tetracycline hydrochloride,respectively.The experimental results proved that the drug loading rate and entrapment efficiency of AP-Fe₃O₄/CNTs?20 mg?were 36.99±0.28%and 73.97±0.56%,while those of CTS-Fe₃O₄/CNTs?20 mg?were 35.45±0.49%and 70.89±0.98%,respectively.In the experimental study of drug release in vitro,the release of AP-Fe₃O₄/CNTs and CTS-Fe₃O₄/CNTs accounted for approximately 60%and 66%of the respective drug loading capacity.Thus,compared with AP-Fe₃O₄/CNTs,the drug loading rate of CTS-Fe₃O₄/CNTs was similar to its entrapment efficiency,and its drug release in vitro was more complete.In addition,the antibacterial effects of drug-loaded AP-Fe₃O₄/CNTs and drug-loaded CTS-Fe₃O₄/CNTs on gram-positive and gram-negative bacteria were studied by inhibition zone experiments.The results showed that both drug-loaded AP-Fe₃O₄/CNTs and drug-loaded CTS-Fe₃O₄/CNTs had antibacterial effects against gram-positive and gram-negative bacteria.The drug-loaded CTS-Fe₃O₄/CNTs,by contrast,had better antibacterial effect.?5?Glycidol and Succinic anhydride were used in the modification of surface functional of silver nano-particles and and endowed them with carboxyl groups.Silver modified magnetic carbon nanotubes composites?Ag@AP-Fe₃O₄/CNTs,Ag@CTS-Fe₃O₄/CNTs?were prepared by acylation of carboxylated silver particles with AP-Fe₃O₄/CNTs and CTS-Fe₃O₄/CNTs.And the properties of Ag@AP-Fe₃O₄/CNTs and Ag@CTS-Fe₃O₄/CNTs were characterized by FT-IR,TEM,XRD,XPS and VSM etc..Besides,the antibacterial effect of Ag@AP-Fe₃O₄/CNTs and Ag@CTS-Fe₃O₄/CNTs on gram-positive and gram-negative bacteria was studied by inhibition zone experiments.The results proved that both Ag@AP-Fe₃O₄/CNTs and Ag@CTS-Fe₃O₄/CNTs had antibacterial effect.While the antibacterial effect of Ag@AP-Fe₃O₄/CNTs was better by contrast.