Application Of Antibacterial Nano-Materials In Vivo

Bacterial resistance is an extremely serious and urgent problem in today's society.The existing methods are now just delaying the occurrence of bacterial drug resistance,and the problem cannot be solved fundamentally.Therefore,new thoughts and methods are needed to develop new antimicrobial agents.Nanotechnology is one of the three major technologies in the 21 st century.It focuses on the the phenomenon of material's change about physical,chemical and biological in nanometer scale to study various research areas such as physics,chemistry and biology,etc,and establish new technology and knowledge on the basis of the small size material.Nanomaterials with very small size have these characteristics: surface effect,quantum size effect,small size effect.Other characteristics are dielectric limiting effects,macroscopic quantum tunneling effect,etc.Nanomaterials are the most closely related with the former three characteristics in biomedicine.Therefore,the application of nanomaterials in biomedical field has broad prospects.Currently,human has used silver and zinc oxide in the treatment of skin infection disease for thousands of years,so nano silver and nano zinc oxide are now the most common and the earliest researched and widely used in the inorganic nanomaterials.But there is little report about nanomaterials on pathogenic bacteria infection in vivo,which are likely to be the last line of defending human against antibiotic resistant bacteria.Therefore,this project will be carried out from the perspective of applications.Part ?: Study of nanosilver on the synthesis,characterization,biocompatibility and application in vivo.Background: Until now,nano silver still had not been used in vivo,resulting from the safety people concerned.Based on our former study,we found that carbon packaged nano silver could realise three modes conversion of packaged,activation and inactivation through PBS solution implemented by using different concentration,achieving the goal of controlling nano silver antibacterial ability intelligently.NaCl is its main component.It is unknown that how NaCl affects the antibacterial properties,cytotoxicity and others of nano silver.Objective: To study different modes of nano silver affected by NaCl and the performance of this mode in its antibacterial properties,cytotoxicity,metabolism in vivo and sepsis.Methods:The size of Ag-C affected by NaCl was accessed with UV-vis,TEM and SEM.Staphylococcus aureus,Escherichia coli and Pseudomonas aeruginosa were used to illustrate the antibacterial properties of nano silver affected by NaCl.L929 and 3T3 cell lines were utilized to test cytotoxicity by CCK-8 assay.Then,we explored the metabolism of Ag-C with NaCl in vivo.Finally,based on the above experiments,the effect of Ag-C with 4×NaCl on sepsis was observed.Results: NaCl could regulate the size of Ag-C.Ag-C exhibited superior antibacterial properties compared to similar sized pure Ag nanoparticles.Furthermore,the addition of NaCl could not only reduce the cytotoxicity of Ag-C,but could also continue to discharge Ag-C from major organs and reduce accumulation.Based on these factors,this method was used to treat severe sepsis mice and found Ag-C+4×NaCl could extend the median survival time(MST).Conclusion: The use of NaCl could significantly improve the safety and feasibility of nano silver,and could potentially play an important role in antibacterial applications in vivo.Thus,a new method to combat the growing threat of drug-resistant bacteria could be possible through using nano silver.NaCl may be essential for metabolism and safe use of nano silver.Part ii: Study of ZnO Nanoslices Hydrogel on synthesis,characterization,biocompatibility,and application in infected woundsBackgroud: Nano ZnO is insoluble in water.It is therefore difficult to prolong and improve its antibacterial properties under the premise of biocompatibility.Hydrogel is widely used in the field of biomedicine because of its high biocompatibility and drug transmission capacity.Vacuum Sealing Drainage(VSD)is now commonly used in the treatment of various acute and chronic infected wounds,achieving remarkable curative effect.However,it is lack of antibacterial property.At the same time,VSD also has its own disadvantages that some irregular shape,uneven depth,specific parts of wounds are not fully contacted the VSD wound dressing,and has so complexed instruments that are not easy to carry for the patient.In addition,surgical suture skills require extremely high skills and long training.Therefore,it is a need for a new kind of wound material with excellent mechanical traction,adapting to the shape of the wound,and easy to carry and operate.Objective: To explore the performance of different nano ZnO hydrogel in tensile strength,moisture content,water absorption,stickness and cytotoxicity and so on,and select appropriate nano ZnO hydrogel treating skin infected wound,observing its effects on wound healing and scar.Methods:We first synthesized diverse sizes of ZnO nanoslices and rods.Through scanning electron microscope,energy spectrum analyzer and X-ray diffraction,different kinds of nano ZnO were identified.Then we mixed them and montmorillonite respectively with dopamine,acrylamide,ammonium persulfate and other materials to synthesize hydrogel.Considering the curing time,tensile strength,water absorption,antibacterial properties and cytotoxicity and other indexs,we selected a kind of hydrogel with short synthesis time,strong tensile strength,large water absorption,strong antimicrobial properties and good biocompatibility,and then we applied the type of hydrogel to full-thickness skin defect wound with the infection in rabbit.Results: we first synthesized three different sizes of ZnO nanoslices and a kind of ZnO nano rod,and applied them to the synthesis of nano ZnO hydrogel.Compared with two kinds of montmorillonite hydrogel,ZnO-large nanoslices hydrogel,ZnO nanorod hydrogel and montmorillonite-large hydrogel have larger pore size than other hydrogels;ZnO-large and ZnO-middle nanoslices hydrogel solidified much faster than other hydrogels.The elongation of montmorillonite-large hydrogel is the longest,and the tensile strength of ZnO-large and ZnO-middle nanoslices hydrogel is stronger than that of other hydrogels.There were no any differences in the moisture content of 3 kinds of ZnO nanoslices hydrogel.In terms of water absorption capacity,compared with other hydrogels,ZnO-small and ZnO-middle nanoslices hydrogel and montmorillonite-large hydrogel had good hydroscopicity.The stickiness strength of ZnO-middle nanoslices hydrogel was the most viscous,and the montmorillonite hydrogel was not sticky.In terms of cytotoxicity,two concentrations of six hydrogels in 10mg/ml and 20mg/ml had no obvious toxicity in L929 cells.In terms of antibacterial properties,4 kinds of nano ZnO hydrogel had good antibacterial effect on S.aureus,E.coli and P.aeruginosa.Among them,ZnO-large nanoslices hydrogel had weaker antibacterial effect than other hydrogels,and montmorillonite hydrogels had almost no antibacterial effect.Based on the above results,we applied ZnO-middle nanoslices hydrogel to full-thickness skin defect wound with infection in rabbit.We found that the scar area was the smallest and thickness was the thinnest in ZnO-middle nanoslices hydrogel group,but there was no difference in the epithelial thickness among the groups.Conclusion: A new kind of wound dressing was produced,which could improve wound healing quality,reduce the scar area,prevent and cure infection,carry easily and operate simple.