Preparation And Properties Of Antimicrobial Composite Materials Based On N-halamines

Infection and the biofilm formation of bacteria,fungi or other microorganisms cause serious threats in medical,industrial and environmental fields,also bring negative impacts on human health.Antimicrobial materials and biocidal techniques have been developed to effectively control and prevent the pathogenic infection.Due to good hydrophilicity,rich nutrients such as polysaccharides,textiles especially cotton fabrics are easy to carry and breed bacteria.To increase the value of textiles and expand the scope of application,antimicrobial treatment has been one important functional finishing.Among common antimicrobial agents,N-halamine has attracted much attention due to its high-efficiency,broad-spectrum biocidal properties,and made a great contribution to human and public hygienic.It is urgent to improve the UV stability of N-halamine compounds since the antimicrobial ability would loss along with the broken of N-Cl or other covalent bonds between N-halamine and materials under UV light irradiation,thus limiting the practical application.To prepare high-efficient and UV-stable N-halamine based materials,some ideas were produced in this study as follow.Based on the structure of N-halamine antimicrobial agents,two cyclic structure N-halamine compounds were designed and coated onto cotton fabrics.On the basis of synthesized N-halamine compound,nano titanium dioxide?TiO₂?were introduced for treated cotton fabric.The UV stability of prepared N-halamine and antibacterial fabrics were highly improved,providing a novel basis for producing organic-inorganic composites.Considering size and optical properties of TiO₂,stable and efficient N-halamine/TiO₂ composites were synthesized,which provide the new direction of prepared core-shell organic-inorganic nanomaterials.Based on the biocidal mechanisms and electrostatic affinity of N-halamine and quaternary ammonium salts,new type of composite antimicrobial agent were developed and treated onto cotton fabric.Two cyclic N-halamine precursors,1-?2,3-dihydroxy propyl?-S-triazine-2,4,6-trione?DTT?and 3-?3-chloro-2-hydroxypropyl?-5,5-dimethylhydantoin?CHPDMH?,were synthesized and used to modify cotton fabrics via pad-dry-cure process.Antibacterial test showed that DTT treated cotton fabric could inactivate 1.00×10⁷ CFU of S.aureus within 1min and 2.00×10⁷ CFU of E.coli within 10 min.CHPDMH treated cotton fabric could inactivate 99.999%of S.aureus and 100%E.coli within 5 min.After 24 h UV light irradiation,the chlorine content of DTT treated cotton decreased from 0.27%to 0.02%,and about 37%chlorine could be recharged after rechlorination.Under the same condition,the chlorine content of CHPDMH treated cotton fabric decreased from 0.25%to 0.05%,and 92%chlorine could be recharged.DTT and CHPDMH treated cotton fabrics showed outstanding antibacterial properties after chlorination,however the chlorine contents of the samples were lost rapidly during UV light irradiation.It should be noted that most of the chlorine content on DTT treated cotton could not be restored.Rutile nano titanium dioxide?TiO₂?was introduced to increase the UV stability of DTT in this part.DTT/TiO₂/cotton sample was prepared via pad-dry-cure process using BTCA as crosslink agent.After chlorination,the prepared sample could inactivate 100%of S.aureus and E.coli within 5 min.Compared to DTT treated cotton,the chlorine content on DTT/TiO₂/cotton was stable during UV light irradiation,the chlorin content on DTT/3%TiO₂/cotton-Cl sample decreased from 0.30%to 0.09%under 24 h UV irradiation,and almost all the chlorine could be recharged after rechlorination.The prepared samples with good biocompatibility have potentials for practical application.Previous research fully proved Ti O₂ could improve the UV stability of N-halamine compounds.In this section,N-halamine functionalized titanium dioxide core-shell nanoparticles were prepared via miniemulsion polymerization using3-allyl-5,5-dimethylhydantoin?ADMH?and methyl methacrylate?MMA?as the shell and nano-TiO₂ as the core structure.TiO₂@poly?ADMH-co-MMA?-Cl NPs possessed excellent antibacterial ability against S.aureus and E.coli compared with the control samples,and could inactivated 100%of S.aureus and E.coli within 10 min and 30 min,respectively.The results of in vitro cytocompatibility showed good cytocompatibility to NIH 3T3 mammalian cells.The existence of TiO₂ in the core significantly improved the UV light stability of the N-halamine structure.Only 42%of original chlorine was lost after 72 h of UV irradiation,and73%of original chlorine on the TiO₂@poly?ADMH-co-MMA?-Cl NPs could be recharged upon exposure to an aqueous sodium hypochlorite solution.In the UV rechargebility test,after 8 cycles of UV irradiation-rechlorination cycles,the chlorine content of the prepared nanoparticles decreased from 1.26 to 0.98%,indicating that the N-halamine groups of samples have good UV stability and regenerability.TiO₂@poly?ADMH-co-MMA?-Cl NPs were used to coat onto cotton fabrics,and the coated fabrics showed excellent antibacterial property.Aromatic ring was introduced into N-halamine structure to improve the UV stability from structure.TiO₂ was modified by KH570 before encapsulating,so that it could be directly dispersed into the oil phase monomer to polymerize.For further improving the UV stability of N-halamine structure,aromatic ring structure was introduced into the N-halamine shell component to prepare N-halamine/TiO₂ nanocomposites.The resultant MPS-TiO₂@PVBC-DMH-Cl nanoparticles presented outstanding biocidal efficacy against S.aureus and E.coli and potent biofilm controlling ability towards S.epidermidis,E.coli,and C.albicans.In addition,the chlorinated nanoparticles showed better improved UV light stability.After 72 h of UV light irradiation,the chlorine content of the prepared nanoparticles is 0.72%,and 87%of the chlorine was regained after rechlorination.MPS-TiO₂@PVBC-DMH-Cl NPs could be directly coated onto cotton fabrics,and the prepared antimicrobial fabrics also showed good biocidal ability.TiO₂ could improve the UV stability of N-halamine compounds efficiently.To explore another approach,quaternary ammonium salt was introduced to synthesize cationic and anionic N-halamine copolymer precursors with different compositions,and coated onto cotton fabric via layer-by-layer assemble technique.The LBL fabric showed good antimicrobial efficacy and biofilm-controlling property against Gram-positive bacteria S.epidermidis,Gram-negative bacteria E.coli,and fungi C.albicans.After exposure to diluted aqueous solution of household bleach,the amide groups in the coatings were transformed into N-halamines,and significantly enhanced antimicrobial efficacy and biofilm-controlling function.In addition,the LBL N-halamine cotton fabrics showed good stability towards artificial sweat and rechargeability after repeated home laundering.The chlorine content of LBL cotton fabric decreased slowly,after 12 h UV irradiation,chlorine content decreased to0.10%and 92%of the chlorine can be restored after rechlorination.In vitro cytocompatibility test demonstrated that the LBL N-halamine cotton fabrics are cytocompatible to mammalian fibroblast cells.