Preparation And Evaluation Of Zinc-doped Copper Oxide And Its Composite Material In Terms Of Their Antibacterial And Wound Healing Behaviors And Mechanisms

?-lactam and other synthetic antibiotics were commonly used drugs for clinical inhibition of surgerical or exogenous bacterial infections,but their abuse also led to a substantial increase in bacterial resistance,which brought the drawbacks of traditional antibiotics into public concerns.Compared with those antibiotic-related organic drugs,nanosized inorganic antibacterial materials,due to their facile fabrication methods,cost-effectiveness,stable yet effective antibacterial performance and other advantages,are growing appealing to experts recently.Through the optimization of nanotechnology,nano-inorganic antimicrobial materials with special properties can be further designed and synthesized to suit to others application,not limited to bacterial killing but other fields such as antibacterial wound dressings,and can effectively inactivate the emerging drug-resistant strains while exerting antibacterial activity simultaneously.The idea of utilizing copper and zinc,which are essential trace elements in the human body,to design and produce new antimicrobial materials can not only replace expensive antimicrobial silver nanoparticles,but also be applied directly as a medical dressing additive to avoid wound infection and effectively acelerate the wound healing process.In this work,prickly zinc-doped copper oxide(Zn-CuO)was prepared by a green sonochemical method,and through further decoration on graphene oxide(GO)nanosheets,an antimicrobial Zn-CuO@GO composite was also obtained.Subsequently,the antibacterial behaviors and mechanisms of these two kinds of materials were studied.In addition,acted as the Pickering nanoparticles,Zn-CuO@GO was aslo used to design Pickering high internal phase emulsion(HIPE)template with the aim to fabricate a peelable porous antibacterial biofoam as wound dressing.The obtained biofoam was studied for its behavior in accelerating dermal wound healing.Generally,the main parts of the research were illustrated as follows:(1)Controllable preparation of prickly Zn-CuO nanoparticles and their antimicrobial behavior and mechanismZn-CuO nanoparticles were prepared via a green sonochemical method.The formation of Zn-CuO was closely related to the ultrasonic frequency,reaction time and raw material feeding ratios,which concurrently contributed to their unique nanostructure.The physical and chemical properties of Zn-CuO were characterized by transmission electron microscopy(TEM),scanning electron microscopy(SEM)and laser confocal microscopy.Also,the antimicrobial properties of prickly Zn-CuO were analyzed and verified through traditional colony-forming-unit(CFU)counting,growth curve and inhibition zone studies.These results showed that the obtained prickly Zn-CuO nanoparticles showed strong antibacterial activity against microbes,and 99.0% of the bacteria were killed in the dark condition within 10 minutes,while their growth were also significantly inhibited in the nutrient broth media.Further studies revealed that the prickly Zn-CuO nanoparticles could cause physical damage to the bacteria,that was,to accelerate the cytoplasmic leakage through puncture on the bacterial membrane,which led to progressive bacterial death.In order to verify the effect of nanostructures on bacterial membrane damage and bacterial killing,a comparative study was conducted on Zn-CuO nanorods with two tips.It was found that prickly Zn-CuO had a different antibacterial activity against the rod-like Zn-CuO,and the former showed better antibacterial activity,due to their nanostructure transtion from multi-dimension(Prickly)to one-dimension(Rod-like).These results showed that the nanostructures were important for the antibacterial activity of Zn-CuO and provided a new strategy for mediating inorganic nanoparticles to exert the physical killing of bacteria.(2)Preparation of Zn-CuO@GO nanocomposites and their antimicrobial behavior and mechanismIn order to improve the antibacterial performances and structural rigidity of obtained materials,prickly Zn-CuO were deposited further on the graphene oxide(GO)nanosheets to fabricate Zn-CuO@GO composite via the green sonochemical methods.The antibacterial mechanism of Zn-CuO@GO composite was carefully investigated by means of CFU counting,and TEM and LCSM were employed to validate.These results demonstrated that the prepared Zn-CuO@GO has significant antibacterial activity,due to the combinational antibacterial activity from Zn-CuO and GO concurrently.Specifically,Zn-CuO@GO can accelerate the "cleavage" of bacteria and activate contact-killing within 10 minutes,among which time period the bacteria were completely destroyed.Moreover,the enhanced antimicrobial mechanism from Zn-CuO@GO was elaborated from the combination of transmission electron microscopy and scanning electron microscopy,and that Zn-CuO@GO could penetrate and embrace bacteria stepwisely by physical adsorption,nano-piercing and embracing.Due to its strong interaction with bacterial membrane,bacterial integrity was destroyed completely,while inducing cytoplasmic leakage,thereby depriving bacteria of oxygen and nutrients exchange from the surrounding media,and eventually leading to bacterial rupture and lysis.(3)Zn-CuO@GO as Pickering nanoparticles to constructe Pickering high internal phase emulsion template with the aim to fabricate a porous antibacterial bio-foam dressing for dermal wound healingThe Pickering high internal phase emulsion(HIPEs)template was constructed through Zn-CuO@GO as the stable Pikcering nanoparticle and a small amount of cell culture grade Tween-80 as the auxiliary emulsifier.By initiating the polymerization of a polysaccharide monomer(vinyl chondroitin sulfate)and a functional monomer(4-vinylbenzene boronic acid)in the external phase,a peelable porous antibacterial bio-foam was successfully prepared.The general properties of porous antibacterial biofoam were analyzed by IR spectroscopy(FT-IR),Raman spectroscopy,SEM and laser confocal microscopy,with concerns to its morphology and compositins.The effects of Zn-CuO@GO as the emulsifier on the general stability,rigidity and ductility of the porous antibacterial biofoam dressings were studied.Also,the behaviors of the antibacterial biofilm dressing on wound healing was carefully studied by combining antibacterial assays,animal and histological studies.These results revealed that the porous antibacterial bio-foam could effectively adhere to the wound bed through the reversible polyvalent boronic acid/cis-diol interaction and achieve painless peeling under the admonistration of glucose solution,which could also significantly accelerated the general process of wound healing.