Preparation And Antibacterial Properties Of Iron/Carbon Composites

Bacterial infection,commomly caused by pathogenic bacteria invading human body and producing metabolites,are a growing threat to public health worldwide.The traditional treatment strategy of antibiotics has aggravated environmental pollution,and the emergence of drug-resistant bacteria limits its therapeutic effect,in this regard,exploring novel alternative strategies to defeat bacteria is imminent.Nowadays,an effective novel strategy is utilizing reactive oxygen species(ROS)produced by nanozyme platform to inactivate bacteria,which has attracted wide attention.Compared with the traditional treatment strategy,utilizing ROS to kill bacteria will not damage the normal tissue.Among enzyme-like nanomaterials,due to its inherent enzyme-like characteristics,easier accessibility,low cost,high stability and favorable biocompatibility,carbon nanomaterials have become a research hotspot,showing broad antibacterial prospects.However,the unsatisfiable enzymatic efficiency and inefficient antibacterial activity restrict their practical application as potential antibacterial agents.Numerous studies have indicated that enzyme activities of carbon materials will be enhanced by the introduction of metal elements,thus we are committed to the construction of iron-carbon composite nanomaterials with strong antibacterial efficiency.In this paper,iron-carbon composites with multi-enzyme mimicking activities,including peroxidase(POD)-,oxidase(OXD)-,catalase(CAT)-,and superoxide dismutase(SOD)-like activities were synthesized,and then the antibacterial efficiency were further studied.After detailed characterizations of the morphology and structure of the fabricated materials by SEM,TEM,XRD and so on,the multi-enzyme mimicking activities of Fe/N-doped hollow carbon nanospheres(Fe/N-HCNs),N-doped hollow carbon nanospheres covered with Fe7S8 nanosheets(N-HCNs@Fe7S8)and N-doped hollow carbon nanospheres loaded with FeP nanoparticles(N-HCNs@FeP)were carried out systematically,followed by the evaluation of the antibacterial efficiency of the fabricated materials by single reactive oxygen species therapy or multiple antibacterial therapies including reactive oxygen species therapy in vitro and in vivo.Finally,the corresponding antibacterial mechanism were explored,this paper mainly includes the following three parts:(1)The Fe/N-HCNs were synthesized with CTAB/F127 mixed micelle as the soft template,3-aminophenol-formaldehyde resin as carbon source and iron acetylacetonate as iron source.The morphology and structure of the obtained materials were characterized,and the effect of the addition amount of the iron source on morphology,structure,iron forms and enzyme activities of Fe-doped carbon materials was evaluated carefully.The results revealed that the Fe in the carbonized materials was mainly iron oxides,while by HCl leaching,the iron oxides were selectively removed,Fe/N-HCNs were obtained and the remaining iron was mainly in the form of Fe-Nx.By adjusting the ratio of Fe(acac)3/3-aminophenol,the effects of the content of Fe and the existing form of Fe on the enzyme activities were studied.The results indicated that Fe/N-HCNs exherted prominent multi-enzyme activities,compared with N-HCNs and FeOx/Fe/N-HCNs.The antibacterial properties of FeOx/Fe/N-HCNs and Fe/N-HCNs were further explored by the plate count method,revealing that as an efficient peroxidase,Fe/N-HCNs can catalyze the low concentration of H2O2 generating a high level of ROS under the weak acid atmosphere,effectively inhibiting Escherichia coli(96.926%)and Staphylococcus aureus(73.077%)in vitro,and accelerating the healing of Staphylococcus aureus-infected wounds in vivo with good biological safety.(2)In the above synthesis system,N-HCNs@Fe7S8 were synthesized through the hydrothermal method based on the nitrogen-doped hollow carbon nanosphere(N-HCNs)with iron acetylacetonate as iron source and tetraethylthiuram disulfide as sulfur source.The morphology and structure of the obtained materials were characterized,and the effect of the addition amount of tetraethylthiuram disulfide on morphology and structure of the fabricated nanomaterials was evaluated carefully.The following study of enzyme activities indicated that N-HCNs@Fe7S8 exherted prominent multi-enzyme activities,compared with N-HCNs.The antibacterial properties of N-HCNs,Fe7S8 NSs and N-HCNs@Fe7S8 were further studied by the plate count method and the their antibacterial mechanisms were further explored.The experimental results showed that except as a weak oxidase producing trace ROS,N-HCNs@Fe7S8 can release sulfur and Fe2+ in solution,effectively inhibiting Escherichia coli(99.479%)and Staphylococcus aureus(97.145%)in vitro,and accelerating the healing of Staphylococcus aureus-infected wounds in vivo with good biological safety.(3)Based on the synthesis of the first part,N-doped hollow carbon nanospheres loaded with Fe3O4 nanoparticles(N-HCNs@Fe3O4)was firstly synthesized.Then with NaH2PO2 was used as the phosphorus source,N-HCNs@FeP was obtained by high temperature phosphating.The morphology and structure of the obtained materials were characterized,and the effect of the hydrothermal time on morphology and structure was evaluated carefully.The results revealed that the Fe3O4 NPs were completely phosphated and FeP NPs were successfully compounded with N-HCNs.The following study of enzyme activities,the photothermal performance and the antibacterial performance under near-infrared irradiation indicated that in addition to producing heat,near-infrared irradiation can also promote the peroxidase activity of N-HCNs@FeP,catalyzing the low concentration of H2O2 generating a high level of ROS,effectively inhibiting Escherichia coli(99.987%),Staphylococcus aureus(99.997%),drug-resistant Staphylococcus aureus(99.645%)and Coccus albicans(99.988%)in vitro,and accelerating the recovery of drug-resistant Staphylococcus aureus-infected wounds in vivo with good biological safety.