The Influence Of Gold Nanoparticles On The Synergistic Antibacterial Effect Of Quinolones Combined With Ultrasound And Its Mechanism

Antibiotic abuse is a serious threat to human health,so the demand for new antibacterial drugs and antibacterial methods are increasing.In recent years,sonodynamic antimicrobial chemotherapy(SACT)has been favored by researchers in the field of antibacterials.Ultrasound can irradiate the sensitizers gathered in the diseased tissue because of its strong penetrability to tissues,at the same time,the microorganisms are killed by activating the active oxygen species(ROS)generated by the acoustic sensitizer and the series of sonochemical reactions or physical effects induced by it.Nanoparticles not only reduce the ultrasonic cavitation threshold,but also promote the generation of hydroxyl radicals in the system,and then play a role in enhancing the antibacterial effect.Gold nanoparticles(GNPs)are widely used in antitumor research due to their stable properties,low autotoxicity,good biocompatibility,and low side effects.Previous research by our research group showed that ciprofloxacin(CIP),a representative drug of quinolone,is acoustically sensitive,and combined with ultrasound can enhance the antibacterial effect.Based on the above points,we propose the combined use of GNPs,quinolone drugs,and ultrasound to study the antibacterial activity of bacteria.It is expected to be meaningful for the study of new antibacterial methods.First,GNPs were prepared by sodium citrate reduction method and loaded with CIP,the physical properties such as particle size,morphology,zeta potential,particle stability,and drug-loading ability were investigated.At the same time,the differences between GNPs and CIP:GNPs were compared by using ultraviolet spectrum,fluorescence spectrum and infrared spectrum.It was determined that there were both Au-N bonding and electrostatic interaction between GNPs and CIP.Then,the effect of GNPs on quinolones in synergistic ultrasound inhibition of E.coli and S.aureus was investigated.The effects of GNPs concentration,drug concentration,ultrasound time and temperature on the antibacterial effect were investigated,respectively.It was shown that both bacteria were inhibited by ultrasound alone,and the inhibition rate was enhanced due to the addition of GNPs and was concentration-dependent.The synergistic bacteriostatic effect of CIP,CIP:GNPs and ultrasound were increased with the increase of CIP concentration,and the synergistic bacteriostatic effect of CIP:GNPs and ultrasound was obviously better than that of CIP and ultrasound at the same concentration of CIP.It was proved that GNPs could promote the synergistic bacteriostasis of ultrasound and CIP.At the same time,It was shown that the antibacterial effect was enhanced if the ultrasound time or temperature increases.Finally,the bacterial morphological investigation and intracellular ROS detection were used to explore the mechanism of GNPs on the bacteriostatic effect of quinolones combined with ultrasound,and the effects of GNPs concentration,drug concentration,ultrasound time,and ultrasound temperature on the amount of ROS were investigated.The scanning electron microscope was used to observe the bacterial morphology under different conditions.It was proved that the mechanism of SACT was related to the cavitation effect.Cell permeability was affected by cavitation vesicles due to cavitation effect,cell contents were leaked in severe cases.Ultrasound cavitation could be promoted by GNPs,so cell integrity was most severely damaged when CIP: GNPs are used in conjunction with ultrasound for bacteria.Fluorescent probe DCFH-DA was used to detect intracellular ROS under different treatment conditions.The experimental results were shown that the trend of ros amount change under different treatment conditions was consistent with the trend of bacteriostasis rate.In summary,the synergistic bacteriostatic effect of quinolone drugs and ultrasound could be promoted by GNPs,and its bacteriostatic effect was concentration-dependent and time-dependent.The synergistic antibacterial mechanism of CIP:GNPs,CIP and ultrasound were due to oxidative damage induced by ROS and changes in cell membrane permeability.