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Functionalization And Antibacterial Properties Of Multi-walled Carbon Nanotubes

Posted on:2020-09-04Degree:MasterType:Thesis
Country:ChinaCandidate:H WangFull Text:PDF
GTID:2381330596495557Subject:Chemical engineering
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For millions of years,many pathogens have been endangering human living environment.At present,despite the increasing level of science and technology,it has been confronted with the problem of bacterial resistance,and even the emergence of superbacteria that can resist the effects of various antibiotics.Therefore,it is very necessary to find a substitute for antibiotics to improve human living standards and living environment.As a new type of Carbon nanomaterials,CNTs have great potential in microbial antimicrobial properties due to their small size effect,quantum effect and extreme specific surface area.However,the stable physical and chemical properties of CNTs make it difficult to disperse in various solvents and the raw CNTs have high biological toxicity and low biocompatibility,which largely restrict their use.In recent years,the research on the antibacteria of CNTs composites has become one of the new directions in the field of biomedicine.First of all,in this paper,the raw Multi-walled Carbon Nanotubes(r-MWNTs)were purified and chopped by strong acid oxidation,so that the surface of r-MWNTs is provided with active groups such as carboxyl(-COOH),etc.Preparation of acidified Multi-walled Carbon Nanotubes(f-MWNTs)with good dispersibility.Secondly,on the basis of this,polyethylene glycol 1000(PEG)was covalently grafted on the wall of f-MWNTs by esterification to obtain a kind of composites f-MWNTs-PEG,which further improved the dispersion and biocompatibility of MWNTs.Finally,a non-covalent interaction(π-π stacking and hydrophobic interaction,etc.)was used to adsorb dihydromyricetin(DMY)on the PEG-unwrapped areas of MWNTs,and a kind of DMY functionalized MWNTs composites f-MWNTs-PEG-DMY was prepared.Meanwhile,the antibacterial properties and mechanism of MWNTs and f-MWNTs-PEG-DMY were preliminarily studied by using the common food-borne pathogen Vibrio Parahemolyticus as research object.The main results are as follows:(1)f-MWNTs were prepared by strong acid oxidation.It was found by characterization that active groups such as-COOH were mainly attached to the wall of f-MWNTs,andMWNTs were partially chopped.In addition,f-MWNTs were stably dispersed in deionized water for a week,and no obvious precipitation occurred.(2)At different rotation speeds and treatment times,r-MWNTs will promote the growth of Vibrio parahaemolyticus;while f-MWNTs showed certain antibacterial properties.The antibacterial effect of f-MWNTs is best at 1 h and 150 rpm,and at this time,the survival rate of Vibrio Parahemolyticus is merely 43.7 %.Comparative analysis of the characterization results,this paper preliminarily believed that the antibacterial properties of f-MWNTs is mainly derived from the physical adsorption of f-MWNTs on Vibrio parahaemolyticus cells.A large number of long f-MWNTs are wrapped around the surface of the cells bacteria,increasing the interaction with bacteria,causing damage to the surface structure of the bacteria,inhibiting cell growth and even death,and a small amount of chopped f-MWNTs also caused the cell membrane damage(physical puncture).(3)A kind of DMY functionalized MWNTs composites f-MWNTs-PEG-DMY was prepared.It was found by characterization that PEG was only partially wrapped around the surface of MWNTs to form a “core-shell” structure,while DMY was adsorbed on the PEG-unwrapped areas of MWNTs through non-covalent interactions(π-π stacking and hydrophobic interaction,etc.),and forming some irregular protrusions.In addition,composites f-MWNTs-PEG-DMY has better dispersibility in deionized water.(4)Comparative analysis of the characterization results,this paper preliminarily believed that the antibacterial properties of f-MWNTs-PEG-DMY is mainly derived from the physical adsorption of f-MWNTs-PEG-DMY on Vibrio parahaemolyticus cells and the strong inhibition of Vibrio parahaemolyticus by DMY loaded on the surface of MWNTs.Firstly,a large number of f-MWNTs-PEG-DMY are wrapped around the surface of cells to increase the interaction with the surface of the bacteria,Secondly,most of Vibrio parahaemolyticus is killed by the action of DMY adsorbed on MWNTs.
Keywords/Search Tags:MWNTs, DMY, functionalization, antibacterial properties, composites
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