Preparations And Properties Of N-Halamine/Silica Hybrid Antibacterial Nanoparticles And Magnetic Nanoparticles

N-halamine compounds attracted wide attention to researchers in recent yearsbecause of their wide antibacterial spectrum, long-term antimicrobial activity,non-toxicity, stability, and rechargeability. Due to these characteristics, theapplication of N-halamine antibacterial materials ranges across the area of medicaldevices, hospitals, water purification systems, food packaging, food storage, hygienicproducts, etc. When microorganisms come into contact with N-halamines, anoxidative halogen ion exchange reaction occurs, causing the expiration of the cells. Ingeneralm, the antibacterial performance of N-halamine-based aterials stronglydepends on materials’ surface area and the contact time of microorganisms withmaterials. N-halamine materials with larger surface area can provide moreN-halamine functional sites to contact with the bacteria，and the N-halamineincrement can lead to the enhanced antibacterial efficiency.Nanomaterials have shown huge potentials and good prospects for their applicationin many fields, due to their outstanding properties, such as small size, large surface area,and high reactivity. Therefore, the antibacterial activity of N-halamines can be improved’efficiently by decreasing materials size into nanometer size. Among these, nano-Si02particles are most widely chosen as supports since SiCh nanopatricles are nearly nontoxic,bioimpatible, chemically inert, optical transparent, optimistically water dispersible.In this thesis, three N-halamine/SiCh hybrid antibacterial nanoparticles weresynthesized, and their antibacterial performances against Gram-positive andGram-negative bacteria were investigated. In addition, magnetic separation techniquewas introduced to facilitate the separation process of N-halamine/SiCh hybridantibacterial nanoparticles. The details are as follows: 1.N-halamine/Si02hybrid antibacterial nanoparticles (Cl-DMH/Si02NPs) wereprepared, and the effect of reaction condition on mophology was studied. Theexcellent antibacterial activity of Cl-DMH/Si02NPs against E. coli and S. aureus wasassayed via the minimum inhibition Qoncentration (MIC) and minimurn bactericidalconcentration (MBC) method. The minimum inhibitory concentration (MIC) andminimum bactericidal concentration (MBC) values of the as-prepared Cl-DMH/Si02NPs are15and20|ig/mL for S. aureus，25and30^g/mL for E. coli, respectively.Paper disk diffusion assay showed that smaller-sized Cl-DMH/Si02NPs have biggerinhibition zone diameters, indicating stronger antimicrobial eiffcacies. Also, thestorage stability and regenerability of Cl-DMH/Si02NPs were investigated.2.N-halamine/Si02hybrid magnetic antibacterial nanoparticles (Cl-DMH/Si02@Fe3〇4NPs) were prepared and characterized by a series of measurements. Effects ofconcentration and contact time on antibacterial efficiency were investigated. The MICand MBC values of the as-prepared Cl-DMH/Si02@Fe3〇4NPs are25and30^ig/mLfor S. aureus,30and40^ig/mL for E. coli, respectively. Meanwhile, the concentrationof30jag/mL Cl-DMH/Si02@Fe304NPs can kill E. coli in60min and S. aureu in120min. The results demonstrate that Cl-DMH/Si02@FesOa NPs have higherantimicrobial activity against E. coli than S. aureus. The good regenerability featureof the as-prepared Cl-DMH/Si02@Fe304NPs means that the lost oxidative chlorinesin N-halamine functional groups of Cl-DMH/Si02@Fe304NPs atfer antibacterialperformance can be regained via a simple chlorination treatment.3.HinderedN-halamine/Si02hybrid antibacterial nanoparticles (Cl-HA/SiCh NPs)were prepared and effects of ratio of reactants, temperature and reaction time on theoxidative chlorine (C1+) percentage were studied. The as-synthesized Cl-HA/SiCh NPswere characterized by transmission electron microscopy (TEM), scanning electronmicroscopy (SEM)，X-ray photoelectron spectra (XPS)，specific surface area (BET),thermogravimetric analysis (TGA).Antibacterial test revealed that the as-preparedCl-HA/Si02NPs have excellent antibacterial activities against S.aureus and E.coli.The antimicrobial results showed that Cl-HA/SiO〗 NPs could kill E.coli and S. aureus within7min and10min, respectively. Also, the N-halamine antibacterial groups ofthe as-prepared Cl-HA/SiCh NPs have good stability.In summary, several N-halamine based antibacterial hybrid NPs were synthesized,and their enhanced antibacterial efficacies were ascribed to the decrease of theirparticle sizes. In addition, magnetic separation technology was introduced to facilitatethe separation process ofN-halamine-based materials.