The Dispersion And Antibacterial Properties Of Multi-walled Carbon Nanotubes In Presence Of Ultrasound

With the abuse of traditional antibiotics in various fields,the problem of bacterial resistance to antibiotics is becoming more and more serious.Human health and food safety are threatened by pathogens.Since the first discovery of antibacterial effect of carbon nanotubes（CNTs）by Kang et al,many researchers have explored the antibacterial effect of CNTs,which has largely solved the problem of bacterial resistance of traditional antibiotics.However,the current research mainly focuses on the antimicrobial effect of single-walled carbon nanotubes（SWNTs）,and the antimicrobial effect of multi-walled carbon nanotubes（MWNTs）is relatively studied.MWNTs has lower cytotoxicity and lower production cost.Therefore,the antibacterial study of MWNTs has a broad application prospect.The dispersity of MWNTs has always been an important factor affecting its antibacterial properties.Ultrasound（US）,as a means of external energy regulation,can achieve the dual effects of nanoparticles dispersion and enhanced antibacterial effect.In this paper,the influence of ultrasound on the dispersion of MWNTs was firstly studied.S.aureus and E.coli were taken as research objects to discuss the antibacterial effect and synergetic antibacterial mechanism of ultrasound and f-MWNTs.The research contents of this paper mainly include:（1）Ultrasonic dispersion of MWNTs in waterThe effects of ultrasound on the dispersion of MWNTs modified by montmorillonite（Na-MMT）and acidized MWNTs（f-MWNTs）were studied.For MWNTs modified by montmorillonite,the influence of montmorillonite/MWNTs weight ratio,ultrasonic time and ultrasonic power on the dispersion effect of MWNTs was studied,and the dispersion effect was compared with that of f-MWNTs.The results shown that Na-MMT has an obvious dispersing effect on MWNTs and can greatly improve the dispersing property of MWNTs.The optimal dispersion conditions were the ultrasonic time of 40min,the ultrasonic power of240W,the ratio of Na-MMT to MWNTs at 2:1,and the average particle size of MWNTs reached 324nm.The optimal dispersion conditions for f-MWNTs were 30min ultrasonic time,270W ultrasonic power,L f-MWNTs concentration,and the average particle size of f-MWNTs reached 143nm.（2）Study on the synergistic antibacterial effect of ultrasound and f-MWNTsWith S.aureus and E.coli as research objects,the effects of ultrasonic time,ultrasonic power and f-MWNTs concentration on the inhibition of two bacteria were studied by measuring OD600.The results showed both S.aureus and E.coli were inhibited under the synergistic effect of ultrasound and f-MWNTs.The optimal antibacterial effect for S.aureus was achieved with ultrasonic time at 30min,ultrasonic power at 60W,and the concentration of f-MWNTs atL,and the optimal antibacterial effect for E.coli was achieved when the ultrasonic time was 45min,the ultrasonic power was 80W,and the concentration of f-MWNTs wasL.（3）Study on synergistic antibacterial mechanism of ultrasound and f-MWNTsThe synergistic antibacterial mechanism of ultrasound and f-MWNTs was studied through membrane permeability,cell morphology observation and oxidative stress.The results showed that oxidative stress was the result of the synergistic effect of ultrasound and f-MWNTs,and ultrasound could make all target compounds produce ROS,mainly including OH^-and O^2-.The synergistic antimicrobial mechanism was likely a combination of ROS and physical nanoparticle（MWNTs）interference with the cell membrane.Ultrasound increased the dispersibility of f-MWNTs and damaged the bacterial cell membrane and facilitatied the entry of f-MWNTs into the bacteria to produce ROS,resulting in bacterial death.The results of this paper shown that ultrasound can greatly improve the dispersion of MWNTs and enhance the antibacterial effect of f-MWNTs.