N-halamine Structures Research Articles

Preparation of a bifunctional precursor with antibacterial and flame retardant properties and its application to cotton fabrics

Cotton fabric is a cellulose-based material with complex capillary spaces, which enhance breathability and softness. However, these capillary spaces can promote bacterial growth with moisture during storage and daily use. Additionally, cotton fibers are highly flammable, posing a fire hazard to wearer. The lack of inherent antibacterial and flame retardant properties in cotton fabric limits its applications. In this paper, the triazole compound containing Schiff base (NABTA) was synthesized from 3-bromopropene, p-hydroxybenzaldehyde and 3-amino-1,2,4-triazole, followed by an addition reaction between Schiff base activity and 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide (DOPO) to synthesize an antibacterial and flame retardant precursor (NABTA-DOPO). The structure of NABTA and NABTA-DOPO was characterized by FTIR and NMR. NABTA and NABTA-DOPO were applied to cotton fabrics to investigate and compare their antibacterial properties and thermal stability. The results showed that all the cotton fabrics treated with NABTA and NABTA-DOPO had favorable antibacterial effects. The introduction of DOPO had no significant effect on the antibacterial effect and mechanism of the fabrics. However, it otherwise improved the burning stability of treated cotton fabrics. The antibacterial activity of 10 g/L NABTA-DOPO treated cotton fabrics after chlorination against E. coli and S. aureus was over 99.99 %. The vertical burning test results showed that cotton fabrics treated with a concentration of 50 g/L NABTA-DOPO had improved flame retardant properties with a damaged length of 5.9 cm. In addition, the storage, washability, UV stability and antibacterial reproducibility experiments demonstrated the excellent durability and reproducibility of the N-halamine structure of chlorinated cotton fabrics. This study enhances cotton fabric by synthesizing and applying NABTA and NABTA-DOPO, resulting in improved multifunctionalities, including antibacterial properties, flame retardancy, UV resistance, and wettability.

In Situ Preparation of Chlorine-Regenerable Antimicrobial Polymer Molecular Sieve Membranes.

Microbial contamination has profoundly impacted human health, and the effective eradication of widespread microbial issues is essential for addressing serious hygiene concerns. Taking polystyrene (PS) membrane as an example, we herein developed report a robust strategy for the in situ preparation of chlorine-regenerable antimicrobial polymer molecular sieve membranes through combining post-crosslinking and nucleophilic substitution reaction. The cross-linking PS membranes underwent a reaction with 5,5-dimethylhydantoin (DMH), leading to the formation of polymeric N-halamine precursors (PS-DMH). These hydantoinyl groups within PS-DMH were then efficiently converted into biocidal N-halamine structures (PS-DMH-Cl) via a simple chlorination process. ATR-FTIR and XPS spectra were recorded to confirm the chemical composition of the as-prepared PS-DMH-Cl membranes. SEM analyses revealed that the chlorinated PS-DMH-Cl membranes displayed a rough surface with a multitude of humps. The effect of chlorination temperature and time on the oxidative chlorine content in the PS-DMH-Cl membranes was systematically studied. The antimicrobial assays demonstrated that the PS-DMH-Cl membranes could achieve a 6-log inactivation of E. coli and S. aureus within just 4 min of contact time. Additionally, the resulting PS-DMH-Cl membranes exhibited excellent stability and regenerability of the oxidative chlorine content.

Preparation of Rechargeable Antibacterial Polypropylene/N-Halamine Materials Based on Melt Blending and Surface Segregation.

Polypropylene (PP) has been widely used in health care and food packaging fields, however, it lacks antibacterial properties. Herein, we prepared the polymeric antibacterial agents (MPP-NDAM) by an in situ amidation reaction between 2,4-diamino-6-dialkylamino-1,3,5-triazine (NDAM) and maleic anhydride grafted polypropylene (MPP) using the melt grafting method. The effects of reaction time and monomer content on the grafting degree of N-halamine were investigated, and a grafting degree of 4.86 wt % was achieved under the optimal reaction conditions. PP/MPP-NDAM composites were further obtained by a melt blending process between PP and MPP-NDAM. With the adoption of surface segregation technology, the content of N-halamine structure on the surface of PP/MPP-NDAM composites was significantly increased. The antibacterial tests showed that the PP/MPP-NDAM composite could achieve 99.9% bactericidal activity against 1.0 × 107 CFU/mL of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) within 10 and 5 min of contact, respectively. The antibacterial effect became more pronounced with the prolongation of chlorinated time, and it could achieve 99.9% bactericidal activity against E. coli within merely 1 min of contact.

Flexible adhesive GelMA/SF-based patch embedded with polydopamine N-halamine nanoparticles for repair of infected wounds

Complex bacterial infection and inevitable movement are the two most concerning issues in joint wound healing. In this work, N-halamine structure was introduced into polydopamine nanoparticles (PDNPs) and encapsulated in a gelatin methacryloyl (GelMA)/silk fibroin (SF) matrix to endow the patches with efficient and broad-spectrum antibacterial activity. Zone of inhibition and in vivo antibacterial tests confirm that the addition of N-halamine containing organic nanoparticles as antibacterial components is a convenient and feasible strategy in the development of wound healing antibacterial materials. Here, dopamine methacrylamide (DMA) was synthesized and grafted onto the gelatin methacryloyl in patches with UV irradiation to get a reasonable adhesion. The liver prick injury model showed that the flexible adhesive GelMA/SF-based patch could be fixed on the wound area with rapid hemostatic effect. Furthermore, the resultant patches possess good flexibility, breathability and excellent biocompatibility. The histology analysis indicated the designed patches demonstrated less inflammatory response, significantly enhanced vascularization and the regeneration of dermis and epidermis. In summary, these N-halamine hemostatic GelMA/SF patches hold a promise for diverse practical acute trauma treatments.

Developing the functional cotton fabric with N-halamine antibacterial structure based on DA/PEI

In this study, functional coatings with N-halamine structure were formed on cotton fabrics by dopamine (DA) auto-deposition and DA/Polyethyleneimine (PEI) covalent co-deposition, respectively. SEM、UV-Vis and XPS had confirmed the deposition of DA and DA/ polydopamine (PDA) on the cotton fabrics. When the mass ratio of DA/PEI was 1:1.5, a uniform functional coating was formed. XRD had indicated that the coating and the oxidative sodium hypochlorite solution did not affect the crystal structure of cellulose. The DA/PEI co-deposited modified cotton fabric had excellent antibacterial property after chlorination, and the inactivation rate against E coli and S aureus could reach 100% with a contact time of 30 min. In vitro cell cytocompatibility studies demonstrated that the DA/PEI co-deposited modified cotton fabric has good biocompatibility. The functional coating on the cotton fabric remained stable after 50 washing cycles. The UPF values and the wrinkle recovery angle (WRA) tests showed that the DA/PEI co-deposited coating imparted great durable press and UV protective properties to the cotton fabric. The breaking strength loss rate of the modified cotton fabrics after chlorination was about 20%, which had little effect on the wearing property.

Fluorocarbon-assisted surface orientation of N-halamine groups on cellulose in supercritical CO2: An effective and eco-friendly approach for developing higher biocidability

Preferential segregation of N-halamine structure to top surface to better contact with bacteria is demonstrated to be an effective tactic for achievement of higher biocidability. 5-Allylbarbituric acid and its fluorinated derivative, formed by sacrificing a imide hydrogen to tether a 4-perfluorohexylbutyl segment via nucleophilic substitution, were synthesized and separately attached to (50% methylhydrosiloxane)–dimethylsiloxane block copolymer (P(MHS–DMS)) via hydrosilylation. Chlorination of NH bonds originating from barbituric acid produced two N-halamine polysiloxanes that were interpenetrated into cellulose to form coatings with similar morphology and thickness. Although containing ~50% less total content of chlorine than its nonfluorinated counterpart, polysiloxane with fluorinated pendants exerted faster inactivation against Staphylococcus aureus and Escherichia coli due to the orientation of its N-halamine groups on top surface with the assistance of the low-surface-tension 4-perfluorohexylbutyl segment as verified by depth profiling using angle-dependent X-ray photoelectron spectroscopy (ADXPS). Design biocide with proper surface segregation ability therefore paves a new way for improved antibacterial efficacy. The stability and rechargeability of the biocidability of the coatings are satisfactory under washing cycles, UV irrigation, and storage.

Construction of aerogels based on nanocrystalline cellulose and chitosan for high efficient oil/water separation and water disinfection

The aim of this study was to develop novel aerogels based on nanocrystalline cellulose (NCC), and chitosan (CS) for oily wastewater treatment. The quaternarized N-halamine siloxane monomer (QHS) was successfully synthesized and hydrolyzed to form quaternarized N-halamine siloxane polymer (PQHS) in the mixture of NCC and CS solution to improve the antibacterial properties of aerogels. The strong hydrophilicity of natural polymers NCC and CS and the microporous structure of aerogel endow the underwater oleophobic property. The applications of the aerogels as filter materials for oil/water separation are studied, and showed high separation efficiency of different types of oil/water mixtures. The presence of N-halamine structures in PQHS makes the aerogels effectively kill bacteria in oily sewage and inhibit the growth of bacteria on the surface of the materials. The properties of exceptional reusability, oil/water separation efficiency, and antibacterial efficacies render the aerogels as promising materials with potential applications in oily wastewater treatment.

Stable N-halamine on polydopamine coating for high antimicrobial efficiency

In this paper, we report a simple method for preparing a highly effective antibacterial coating by the introduction of an N-halamine structure on a polydopamine (PDA)-based coating. The PDA-based coating includes only PDA and PDA co-deposited with polyethylenimine (PEI). The amine groups in PDA and PEI are assumed to be chlorinated and converted to N-halamine. After the simple immersion of PDA-based coatings in a dilute bleach solution, the formation of N-halamine is confirmed by iodometric titration. Compared with the original PDA-based coating, N-halamine-functionalized PDA-based coatings exhibit high antibacterial activity toward Gram-positive S. aureus and Gram-negative E. coli within a brief contact time. Notably, the PDA samples retain their oxidative chlorine content after extended storage, and ~90% of the chlorine is restorable after repeated quenching. The coatings are applicable to a wide spectrum of substrates and are stable. This study may provide a simple, effective method for the preparation of functional fibers with antibacterial activities for the clothing and textile industries.

Novel composite unit with one pyridinium and three N-halamine structures for enhanced synergism and superior biocidability on magnetic nanoparticles

A novel composite unit of enhanced synergism that rises from the use of a cationic pyridinium structure to attract anionic bacteria to three N-halamine structures was designed for superior biocidability on recyclable magnetic nanoparticles. Briefly, 5-(4-hydroxybenzylidene)hydantoin (HBH), containing one imide and amide NH bonds, was synthesized by Knoevenagel condensation ofp-hydroxybenzaldehyde with hydantoin. 3-Triethoxysilylpropyl succinic anhydride was ammonolyzed with 4-aminopyridine to introduce a pyridine structure and form an amide NH and a carboxylic acid group that was esterified with HBH to introduce its two NH bonds. The triethoxysilyl groups of the esterification product were hydrolyzed into silanols to condense with the counterparts of different hydrolysates and on silica modified Fe3O4nanoparticles to provide a layer of polymeric modifier. After quaternization of the pyridine and chlorination of NH bonds from each esterification product, the resultant layer is composed of units each of which contains one pyridinium and threeN-halamine sites and exerted higher biocidability against Escherichia coli and Staphylococcus aureus than comparable systems including synergistic ones with one cationic center and one N-halamine, demonstrating an enhanced synergism. The biocidal layer had promising stability under quenching-chlorinating cycles and long-term storage. The study affords a strategy for syntheses of more powerful biocidal surfaces.

Rechargeable polyamide-based N-halamine nanofibrous membranes for renewable, high-efficiency, and antibacterial respirators.

Emerging infectious diseases (EIDs) have been acknowledged as a major public health concern worldwide. Unfortunately, most protective respirators used to prevent EID transmission suffer from the disadvantage of lacking antimicrobial activity, leading to an increased risk of cross-contamination and post-infection. Herein, we report a novel and facile strategy to fabricate rechargeable and biocidal air filtration materials by creating advanced N-halamine structures based on electrospun polyamide (PA) nanofibers. Our approach can endow the resultant nanofibrous membranes with powerful biocidal activity (6 log CFU reduction against E. coli), an ultrahigh fine particle capture efficiency of 99.999% (N100 level for masks), and can allow the antibacterial efficacy and air filtration performance to be renewed in a one-step chlorination process, which has never been reported before. More importantly, for the first time, we revealed the synergistic effect involving the intrinsic structure of polymers and the assembling structure of nanofibers on the chlorination capacity. The successful fabrication of such a fascinating membrane can provide new insights into the development of nanofibrous materials in a multifunctional, durable, and renewable form.

Controlling bacterial fouling with polyurethane/N-halamine semi-interpenetrating polymer networks.

N -halamine-based interpenetrating polymer networks were developed as a simple and effective strategy in the preparation of antimicrobial polymers. An N-halamine monomer, N-chloro-2, 2, 6, 6-tetramethyl-4-piperidyl methacrylate, was incorporated into polyurethane in the presence of a cross-linker and an initiator. Post-polymerization of the monomers led to the formation of polyurethane/N-halamine semi-interpenetrating polymer networks. The presence of N-halamines in the semi-interpenetrating polymer networks was confirmed by attenuated total reflectance infrared, water contact angle, and energy-dispersive X-ray spectroscopy analysis. The N-halamine contents in the semi-interpenetrating polymer networks could be readily controlled by changing reaction conditions. The distribution of active chlorines within the semi-interpenetrating polymer networks was characterized with energy-dispersive X-ray spectroscopy. Contact mode antimicrobial tests, zone of inhibition studies, and scanning electron microscopy observations showed that the semi-interpenetrating polymer networks had potent antimicrobial and antifouling effects against both Gram-positive and Gram-negative bacteria. Release tests demonstrated the outstanding stability of the N-halamine structures in the new semi-interpenetrating polymer networks.

Regenerablity and Stability of Antibacterial Cellulose Containing Triazine N-halamine

A reactive triazine derivative, 2,4-dichloro-6-hydroxy-1,3,5-triazine (DCHT), was prepared through the controlled hydrolysis of cyanuric chloride in water solution. The reaction was characterized with 13C NMR study. The reaction solutions could be directly used to treat cellulose fibers. A pad-dry-cure method was employed to immobilize the triazine derivative onto cotton. The covalently bound triazine moieties on cotton could be transformed into N-halamine structures after a chlorine bleaching treatment. The biocidal efficacies of the treated samples with different chlorine loadings were further examined. The storage and release testing showed that the antimicrobial function of the N-halamine modified cotton fabrics was durable and renewable. These advantages make the triazine N-halamine modified cotton as an attractive candidate in a broad range of application fields.

Development and characterisation of antibacterial suture functionalised with N-halamines

Braided and biodegradable polyglycolide suture was antibacterially functionalised with N-halamines via layer-by-layer assembly technique. Multilayers of chitosan (polycation) and poly-sodium-p-styrenesulfonate (polyanion) were successfully coated via electrostatic assembly, followed by top layer of chitosan on polyglycolide suture. Upon chlorination of coated suture with dilute sodium hypochlorite solution, the amino groups of chitosan were transformed into N-halamine structures. The transformation was assessed by iodometric/thiosulfate titration, Fourier transform infrared spectroscopy and differential scanning calorimeter analysis. The surface morphology of coated suture was observed by scanning electron microscope and atomic force microscope. Chlorine loading, antibacterial efficacy and tensile strength of chlorinated sutures treated with two different molecular weights of chitosan were compared and evaluated. A general trend of linear increase in chlorine loadings of sutures with the increase in number of layers and solution concentration was found. The chlorinated suture with high molecular weight chitosan coating completely inactivated both Escherichia coli O157:H7 and Staphylococcus aureus bacteria within 15 min of contact time. The 3T3 mouse fibroblasts in vitro cell cytocompatibility studies demonstrated that antibacterial sutures have fairly good biocompatibility.

N-halamine modified polyester fabrics: Preparation and biocidal functions

A cyclic N-halamine precursor, 1-glycidyl-s-triazine-2,4,6-trione (GTT), was synthesized and grafted onto polyester fibers. The tricarbimide rings could be transferred to N-halamine structure upon exposure to dilute sodium hypochlorite solution. Structural and surface characterizations of the polyester (PET) fabrics treated with GTT were accomplished using FT-IR, SEM, and DSC. The antimicrobial efficacy test showed that the N-halamine modified PET could inactivate 6-log of Staphylococcus aureus (Gram-positive) and E. coli O157:H7 (Gram-negative) within 10 min of contact time. The antimicrobial fabrics exhibited good durability and stability to washing and storage.

Eco-friendly synthesis of regenerable antimicrobial polymeric resin with N-halamine and quaternary ammonium salt groups

An effective macroporous cross-linked antimicrobial polymeric resin containing N-halamine and quaternary ammonium salt moieties was synthesized in an eco-friendly and economical way. Commercially available macroporous crosslinked chloromethylated polystyrene (CMPS) resin reacted with the salt of 5,5-dimethylhydantoin (DMH) and trimethylamine (TMA) in water to produce a polymeric resin containing hydantoinyl and quaternary ammonium salt moieties, poly(p-methylstyrene)-3-(5,5-dimethylhydantoin)-co-trimethyl ammonium chloride (PSHTMA). The hydantoinyl groups in PSHTMA were converted to an antimicrobial N-halamine structure by a facile chlorination reaction in dilute NaOCl solution. The as-synthesized antimicrobial polymeric resin (Cl-PSHTMA) was characterized by FT-IR, X-ray photoelectron spectroscopy, and zeta-potential measurement. The antimicrobial tests showed that the as-synthesized antimicrobial polymeric resin was capable of 7-log inactivation of S. aureus and 8-log inactivation of E. coli within 1 minute contact time. Moreover, the N-halamine moieties in Cl-PSHTMA exhibited excellent regenerability.

Durable antimicrobial cotton fabrics containing stable quaternarized N-halamine groups

A novel N-halamine precursor with tertiary amino group (5,5-dimethylhydantoinyl-3-ylethyl)-dimethylamine (DEADH), was synthesized and then covalently bonded onto cotton fabrics modified by 3-chloropropyltrimethoxysilane to form quaternarized N-halamine precursor grafted cotton fabrics which could be transferred to N-halamine structure upon exposure to dilute sodium hypochlorite solution. The grafted cotton fabrics were characterized by FT-IR, X-ray photoelectron spectroscopy, and field emission scanning electron microscope. The antimicrobial test showed that the cotton fabrics grafted with the quaternarized N-halamine were capable of 7-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 1 min of contact time. Very interestingly, it was found that the grafting process and following chlorination had almost no adverse effect on the tensile strength of cotton fabrics. Furthermore, the antimicrobial cotton fabrics exhibited good washing durability and stability.

High-efficacy antimicrobial cellulose grafted by a novel quaternarized N-halamine

A novel quaternarized N-halamine precursor (3-chloro-2-hydroxypropyl)-(5, 5-dimethylhydantoinyl-1-ylmethyl)-dimethylammonium chloride (CDDAC), has been synthesized by a very facile two-step reaction. The two-step synthesis of CDDAC occurred at room temperature with common reactors, so the production of CDDAC could be easily enlarged to an industrial scale. Without any work-up, the final reaction solution which contained CDDAC could be directly used as grafting solution. CDDAC could be effectively grafted onto the surface of cellulose by a dehydrochlorination reaction. CDDAC grafted on cellulose was converted to N-halamine structure which showed powerful antimicrobial property by a chlorination reaction in the diluted NaClO solution. The antimicrobial tests showed that the chlorinated cellulose grafted with CDDAC was capable of 5-log inactivation of S. aureus and E. coli within 5 min. Also, the washing durability and storage stability of chlorinated cellulose grafted with CDDAC were investigated.

Epoxide tethering of polymeric N-halamine moieties

Three heterocyclic N-halamine structures containing amine, amide, or both functional groups were immobilized onto cotton fabric through epoxide tethering. The coatings were rendered biocidal upon exposure to dilute household bleach solution. The coatings exhibited superior biocidal functionality with complete inactivation of about 6 logs of Staphylococcus aureus and Escherichia coli O157:H7 within 2–10 min contact time depending on the structure. Moreover, the coatings were quite stable against repeated laundering so that recharging was not even necessary after 50 washing cycles. Stability of the coatings against ultraviolet light exposure was studied with a comparison of the amide- and amine-containing N-halamines.

Chemical and biological decontamination functions of nanofibrous membranes

Novel composite membranes with poly(vinyl alcohol-co-ethylene-g-diallylmelamine) (PVA-co-PE-g-DAM) nanofibers layered on poly(propylene-g-diallylmelamine) (PP-g-DAM) meltblown nonwoven fabric were successfully developed as lightweight and breathable protective materials with chemical and biological decontamination functions. By controlling levels of coated nanofibers, three nanofibrous membranes with similar surface morphology, hydrophilicity and transport properties were prepared. The N-halamine precursor moieties in the membrane matrices can be converted to active N-halamine structures with a diluted sodium hypochlorite solution, and the active chlorine content on the membranes is rechargeable and durable. The chlorinated nanofibrous membranes demonstrated very powerful and rapid biocidal effects against both E. coli and S. aureus by contact, as well as excellent disinfection effect to wet bacterial penetration through the membrane. Furthermore, the efficient chemical detoxification functions of the halamine nanofibrous membranes were also observed by a total decontamination of aldicarb, a carbamate pesticide, within 30 min. These PVA-co-PE-g-DAM nanofiber composite membranes can serve as ideal ultra-light filtering media for chemical and biological protective clothing materials.

New Refreshable N-Halamine Polymeric Biocides: N-Chlorination of Acyclic Amide Grafted Cellulose

Acyclic N-halamine structures have demonstrated antibacterial functions similar to cyclic N-halamine. Precursors of acyclic halamine such as acrylamide and methacrylamide can be easily grafted onto surfaces of substrates via radical polymerization processes. However, due to easy hydrolysis of primary amides during chlorination and steric hindrance of secondary amide to conversion to acyclic halamine structures, the acyclic halamines still have limitations to many applications in preparation of antimicrobial materials. To reduce hydrolysis of amide during chlorination, particularly under alkaline conditions, addition of electrolytes such as NaCl was able to improve chlorination of polyacrylamide grafted cotton (chlorine content 458 ppm) with less than 10% hydrolysis under slightly basic (pH = 8) conditions. Both acidic conditions and the addition of salt can increase the chlorination of secondary amides and provide effective antibacterial functions on the treated cellulose (5 log reduction of E. coli in contact time of 120 min).