Engineering cellulose nanopaper with water resistant, antibacterial, and improved barrier properties by impregnation of chitosan and the followed halogenation.

This work demonstrated a facile and sustainable approach to functionalize cellulose nanopaper (CNP) by impregnation of chitosan (CS) and the followed halogenation. It was found that the tensile strength of the functionalized CNP (CNP/CS-Cl) was enhanced by 38.3% and 512.6% at dry and wet conditions, respectively. Meanwhile, the total transmittance (at 550 nm) of CNP/CS-Cl was increased from 75% of pure CNP to 85%, with 35% decrease in optical haze. Moreover, the CNP/CS-Cl exhibited significant enhancement in barrier properties. Importantly, part of the amino groups on CS were transformed into N-halamines during the halogenation process, which endowed the CNP/CS-Cl with excellent antibacterial performance against both S. aureus and E. coli with 100% bacterial reduction after 10 min of contact. Thus, this work provides a simple and efficient approach to functionalize CNP with water resistance, high transparency, excellent antibacterial and barrier properties, which will expand the potential applications of CNP.

Evaluation of Escherichia coli and coliforms in aquaponic water for produce irrigation.

The FDA Produce Safety Rule states that water used for irrigation purposes, likely to come into contact with the edible portion of fruit and vegetables, must not exceed a defined limit of Escherichia coli populations. Although aquaponics has not been included in this guideline, it is worth investigating to establish a baseline for facilities to reference in produce production. Two microbial assays were performed, one a decoupled media-based aquaponics system over one year and another on a decoupled nutrient film technique (NFT) aquaponics system over 16 days. Water was sampled from each system over time to analyze changes of E. coli and coliforms. The geometric mean (GM) and statistical threshold variable (STV) were calculated based on E. coli populations from the irrigation source in each system. From the first experiment, it was determined, based on the FDA Produce Safety Rule, that E. coli must be monitored more closely from June to January as they were above the advised limit. The second experiment determined that E. coli and coliforms in the water significantly decreased over 16 days. Water should be held for 8 d and up to 16 d to reduce the likelihood of foodborne pathogens to contaminate produce.

Multifunctional Cellulose Nanopaper with Superior Water-Resistant, Conductive, and Antibacterial Properties Functionalized with Chitosan and Polypyrrole.

Cellulose nanopaper (CNP) has been considered as a promising material with great application potential in diverse fields. However, the hydrophilic nature of CNP significantly limits its practical application. In order to improve its water resistance, we demonstrate a facile approach to functionalize CNP by impregnating it with chitosan (CS), followed by in situ polymerization of polypyrrole (PPy). The results indicate that the obtained CNP/CS/PPy shows excellent water resistance with the wet tensile strength of up to 80 MPa, which is more than 10 times higher than that of the pure CNP. Intriguingly, new features (e.g., electrical conductivity, antibacterial activity, and so forth) are achieved at the same time. The functionalized CNP/CS/PPy shows a high conductivity of 6.5 S cm-1, which can be used for electromagnetic interference shielding applications with a high shielding performance of around 18 dB. In addition, the CNP/CS/PPy exhibits good antibacterial activity toward Staphylococcus aureus and Escherichia coli, with the bacterial reductions of 99.28 and 95.59%, respectively. Thus, this work provides a simple and versatile approach to functionalize CNP for achieving multifunctional properties.

3D Phage-based biomolecular filter for effective high throughput capture of Salmonella Typhimurium in liquid streams.

Foodborne illnesses caused by pathogens on fresh produce remain one of the most critical food safety problems the world faces. The recalls of pasta salad in 2018 and pre-cut melons in 2019 imply current methods in identifying the source of pathogens and outbreak prevention are inappropriate and time consuming. In this article, a new technology, called the 3D phage-based biomolecular filter, was developed to simultaneously capture and concentrate foodborne pathogens from large volumes of liquid streams (food liquid or wash water streams). The 3D phage-based filter consisted of phage-immobilized magnetoelastic (ME) filter elements, a filter pipe system, and a uniform magnetic field to fix and align the ME filter elements in the 3D filter column. The closely packed ME filter elements display a 3D layered structure which allows for enhanced surface interaction of the immobilized bacteriophage with specific pathogens in the passing liquid streams. As a result, a pathogen capture rate of more than 90% was achieved at a high flow rate of 3 mm/s with 20,000 ME filter elements. The capability of the 3D phage-based filter to capture pathogens in liquid streams at different filter element packing densities was further validated by experiments, finite element analysis and theoretical calculations. The capture rate increases significantly with larger numbers of ME filter elements placed in the testing pipe, and the turbulence flow induced by the 3D stacking of ME filter elements can further improve the capture efficiency. This technology enables rapid capture and analysis of large volume of water in processing fresh fruit and vegetables for the presence of small quantities of pathogens, which will ultimately benefit producers, the food industry, and society with improved food safety and production efficiency.

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.

N-halamine modified multiporous bacterial cellulose with enhanced antibacterial and hemostatic properties.

Bacterial cellulose (BC) is a natural polymer with remarkable superiority for fabricating biomaterials. In this study, a multiporous bacterial cellulose (MBC) film was modified with N-isopropylacrylamide (NIPAM), and the modified MBC film was imbued with antibacterial properties after chlorination. The dried chlorinated samples showed superb antibacterial efficacy and could inactivate 6.19 log of inoculated S. aureus and 6.29 log of E. coli within 1 min of contact. After releasing active chlorine for 12 h, 3.67 log of S. aureus and 3.97 log of E. coli were inactivated within 30 min of contact. The prepared films displayed high porous and layered structures with a resultant excellent water retention which can be applied as material for wound dressings. In addition, the chlorinated films showed hemostatic ability on wound bleeding and good biocompatibility. The prepared N-halamine functionalized MBC films might have great potential applications as wound dressings.

Novel quaternarized N-halamine chitosan and polyvinyl alcohol nanofibrous membranes as hemostatic materials with excellent antibacterial properties.

The aim of this study was to develop novel nanofibrous membranes based on the quaternary ammonium N-halamine chitosan (CSENDMH) and polyvinyl alcohol (PVA) for antibacterial and hemostasis wound dressing. To improve the antimicrobial properties of nanofibrous membranes, a new chitosan-quaternary ammonium N-halamine derivative was successfully synthesized, and the structure was analyzed by 1H NMR and 13C NMR, fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The morphological and water absorption ability studies showed that the membrane had a uniform bead-free network and high porosity structure like natural extracellular matrix as well as high hydrophilicity. For in vitro evaluation of the hemostatic effect, the membranes showed excellent blood clotting capacity, especially the PVA/CSENDMH membranes. The antimicrobial assay demonstrated excellent antibacterial activity of nanofibrous membranes against both gram-negative and gram-positive bacteria. Furthermore, the cytocompatibility assay results indicated that human fibroblasts could adhere and proliferate on the membranes, thus corroborating their biocompatibility.

Three-dimensionally printed polylactic acid/cellulose acetate scaffolds with antimicrobial effect.

This study aimed to develop novel, biodegradable, antiseptic-loaded and low-cost scaffolds using a direct ink writing (DIW) technique for antibacterial applications. Polylactic acid/cellulose acetate (PLA/CA) mixtures with different composition ratios were prepared, and the effect of CA content on the rheological behaviors of the inks was investigated. The printability of the prepared DIW inks was improved with the addition of the appropriate amount of CA, since the formation of hydrogen bonding 3D network between PLA and CA. As a result, a liquid form ink consisting of majority of PLA and minority of CA which was prepared and printed for the first time through DIW technique. Afterwards, the antimicrobial agent, 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC) was incorporated into the inks for preventing bacterial infections, which showed excellent stability and effective antibacterial activity against S. aureus and E. coli O157:H7 in a short time. Owning the ease of fabrication and the biocidal property, our 3D printed scaffolds will have a wide range of potential applications in the field of food packaging, communal facilities, medical equipments, and biomedical materials.

Novel pH-sensitive films based on starch/polyvinyl alcohol and food anthocyanins as a visual indicator of shrimp deterioration.

Intelligent packaging can provide better preservation and advanced convenience for consumers. In this study, corn starch and polyvinyl alcohol (PVA) were used to produce films. Two easily accessible anthocyanin sources-purple sweet potato extracts (PSPE) and red cabbage extracts (RCE), were added respectively to evaluate their potential of indicating food freshness. Film incorporated with PSPE or RCE showed distinguishable color changes in different buffers. Water vapor permeability (WVP) was not significantly (p > 0.05) affected by addition of RCE or lower level PSPE. As the extract content increased, a significant (p < 0.05) increase in thickness (from 64.0 to 97.7 or 85.5 µm with addition of PSPE or RCE, respectively), mechanical (from 7.3 to 11.3 or 9.1 MPa in TS, and from 92% to 249% or 284% in EB, added with PSPE or RCE, respectively), and thermal properties was observed, with the light transmittance reduced profoundly. PS-PSPE film exhibited bolder color, better mechanical properties and lower light transmittance than PS-RCE film at lower extract content. In addition, application for indicating shrimp freshness was conducted. The developed film presented visual color changes corresponding to TVB-N variation when shrimps were spoiled, showing its great potential as an indicator for monitoring shrimp freshness.

Novel ZnO/N-halamine-Mediated Multifunctional Dressings as Quick Antibacterial Agent for Biomedical Applications.

Cutaneous hemorrhage often occurs in daily life which may cause infection and even amputation. This research aims to develop a novel chitosan dressing impregnated with ZnO/N-halamine hybrid nanoparticles for quick antibacterial performance, outstanding hemostatic potential, high porosity, and favorable swelling property through combining sonication and lyophilization processing. After 30 days of storage, about 90% bacterial cell viability loss could be observed toward both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli O157:H7 within 30 min of contact by colony counting method. The hybrids assembled much more platelet and red blood cell as compared with pure chitosan control. Moreover, the lower blooding clotting index value gave evidence that these composites could control hemorrhaging and reduce the probability of wound infection. No potential skin irritation and toxicity were detected using in vitro cytocompatibility and a skin stimulation test. Therefore, this work demonstrated a facile and cost-effective approach for the preparation of N-halamine-based hybrid sponges which show promising application for wound dressings.

Graphene oxide as a polymeric N-halamine carrier and release platform: Highly-efficient, sustained-release antibacterial property and great storage stability.

N-halamine compounds have been applied as antibacterial agents owing to the oxidative chlorine. In this work, graphene oxide (GO) as carrier was used to load N-halamine compounds for the sustained-release of chlorine in order to maintain long-term biocidal efficacies. 3­(3'­Acrylic acid propylester)­5,5­dimethylhydantoin (APDMH) was synthesized using 5,5­dimethylhydantoin as a heterocyclic precursor and attached on the surface of GO nanosheets via in-situ polymerization. The modified GO composites were characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The chlorinated GO nanosheets modified with polymerized APDMH (PAPDMH) were very stable and possessed long-term antibacterial properties. The GO-PAPDMH-Cl composites exhibited good antimicrobial efficacies against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli O157:H7) with log reductions of 7.20 and 7.06 within 30 min of contact time, respectively.

Production and In Vitro Gastrointestinal Digestion of Antioxidant Peptides from Enzymatic Hydrolysates of Sweet Potato Protein Affected by Pretreatment.

Effects of ultrasonication, boiling, steaming, microwaving and autoclaving pretreatments on the production of sweet potato protein hydrolysates (SPPH) by single and combined Alcalase (ALC) and Protease (PRO) were investigated, as well as antioxidant activities of SPPH subjected to in vitro gastrointestinal digestion (GID). All pretreatments significantly increased the degree of hydrolysis (DH) and antioxidant activities of SPPH by ALC, PRO and ALC + PRO in the order of autoclaving > steaming, microwaving, boiling > ultrasonication (P < 0.05). GID significantly enhanced antioxidant activities and increased MW <3 kDa peptide fraction contents of all SPPH. Diverse peptides were identified as sporamin A, A precursor and sporamin B before and after GID from LC-QTOF-MS/MS analysis. Peptides with higher antioxidant amino acids of Trp, Tyr, Met, Cys, His and Phe were found after GID. There is a great potential application of SPPH as a novel food ingredient as a natural antioxidant.

The reduction of Salmonella on chicken skin by the combination of sodium dodecyl sulfate with antimicrobial chemicals and coating wax microemulsions.

Chickens with high populations of various microorganisms arrive at processing facilities. Salmonella species are one of the important foodborne pathogens commonly found in poultry products. Various intervention strategies are implemented during poultry processing to reduce microorganisms in the products, including pre-scald bird brushes, multi-stage scalding, antimicrobial applications, etc. In this study, the effects of adding sodium dodecyl sulfate (SDS) to chlorine (Cl) and peracetic acid (PAA) against Salmonella were investigated. In addition, the efficacy of wax coating the skin to reduce Salmonella attachment was studied. Skin samples were collected following the 4 different methods of (1) euthanized-dry hand-de-feathered carcasses, (2) carcasses rinsed in tap water and mechanically de-feathered, (3) carcasses soft scalded and mechanically de-feathered, and (4) from carcasses hard scalded and mechanically de-feathered. It was shown that 0.5% SDS was able to reduce Salmonella both loosely (34, 28, 42, and 13%, respectively) and firmly (29, 39, 32, and 53%, respectively) attached in the 0.005% Cl-treated samples, but did not increase antimicrobial efficacy of 0.2% PAA. Moreover, carnauba wax coating significantly (P ≤ 0.05) reduced Salmonella attachment on all 4 types of chicken skins, 1.57, 0.71, 0.74, and 0.84 log cfu/sample on dry hand de-feathered, tap water rinsed, soft-scalded and hard-scalded chicken skins, respectively. Beeswax coating did not affect Salmonella attachment regardless of types of chicken skins. Overall, the addition of SDS improved antimicrobial activity of Cl, but not for PAA. Moreover, carnauba wax coating was an effective intervention to reduce Salmonella on chicken skin.

PHB/PCL fibrous membranes modified with SiO2@TiO2-based core@shell composite nanoparticles for hydrophobic and antibacterial applications.

In order to prepare multifunctional fibrous membranes with hydrophobicity, antibacterial properties and UV resistance, we used silica and titanium dioxide for preparing SiO2@TiO2 nanoparticles (SiO2@TiO2 NPs) to create roughness on the fibrous membranes surfaces. The introduction of TiO2 was used for improving UV resistance. N-Halamine precursor and silane precursor were introduced to modify SiO2@TiO2 NPs to synthesize SiO2@TiO2-based core@shell composite nanoparticles. The hydrophobic antibacterial fibrous membranes were prepared by a dip-pad process of electrospun biodegradable polyhydroxybutyrate/poly-ε-caprolactone (PHB/PCL) with the synthesized SiO2@TiO2-based core@shell composite nanoparticles. TEM, SEM and FT-IR were used to characterize the synthesized SiO2@TiO2-based core@shell composite nanoparticles and the hydrophobic antibacterial fibrous membranes. The fibrous membranes not only showed excellent hydrophobicity with an average water contact angle of 144° ± 1°, but also appreciable air permeability. The chlorinated fibrous membranes could inactivate all S. aureus and E. coli O157:H7 after 5 min and 60 min of contact, respectively. In addition, the chlorinated fibrous membranes exhibited outstanding cell compatibility with 102.1% of cell viability. Therefore, the prepared hydrophobic antibacterial degradable fibrous membranes may have great potential application for packaging materials.

Cytocompatible quaternized carboxymethyl chitosan/poly(vinyl alcohol) blend film loaded copper for antibacterial application.

Antibacterial quaternized carboxymethyl chitosan/poly(vinyl alcohol)/Cu blend film (QCMCS/PVA/Cu blend film) was prepared by quaternary ammonium salt modified carboxymethyl chitosan (QCMCS), PVA and copper sulfate pentahydrate via the process of solution casting and ion adsorption. The successful preparation of QCMCS was proved by EA, NMR and FTIR, and the degree of quaternization is 71.86%. The QCMCS/PVA/Cu blend film was characterized by SEM, AFM and EDX, and the content of the copper is about 1 wt%. Tensile tests and TGA showed that the mechanical and thermal properties were improved after being loaded with copper ions. By loading with Cu2+, the blend film showed good antibacterial activities. About 98.3% of S. aureus and 99.9% of E. coli could be inactivated within 60 min. The cell cytotoxicity was also studied and the results showed that all the prepared films had acceptable cell viability and biocompatible, which indicates that this blend film has potential applications in packaging and biomedical materials.

N-halamine incorporated antimicrobial nonwoven fabrics for use against avian influenza virus.

Airborne pathogens are one of the most common avenues leading to poultry diseases. Preventing the avian influenza (AI) virus from entering the chicken hatchery house is critical for reducing the spread and transmission of AI disease. Many studies have investigated the incorporation of antimicrobials into air filters to prevent viruses from entering the indoor environment. N-halamines are one of the most effective antimicrobial agents against a broad spectrum of microorganisms. In this study, 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC, a variety of N-halamine) was coated on nonwoven fabrics to give the fabric antimicrobial activity against the AI virus. Results showed that MC exhibited potent antiviral activity either in suspension or in the air. Higher concentrations of MC completely inactivated AI viruses and disrupted their RNA, preventing them from being detected by the real time reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Coating the fabrics with MC resulted in remarkably reduced presence of AI virus on the MC-treated fabric in a short period of time. Furthermore, aerosolized AI viruses were completely inactivated when they passed through filters coated with the MC compound. In addition, MC is not volatile and does not release any gaseous chlorine. The active chlorine in the MC compound is stable, and the coating procedure is straightforward and inexpensive. Therefore, this study validates a novel approach to reducing airborne pathogens in the poultry production environment.

Preparation of antimicrobial and hemostatic cotton with modified mesoporous particles for biomedical applications.

N-halamine polymers have been successfully attached surfaces of mesoporous materials. The modified mesoporous materials have been applied on the modification of cotton. Soaking in household bleach, the coated cotton shows good antimicrobial efficacy against S. aureus and E. coli O157:H7. The chlorinated samples could completely inactivate 100% S. aureus within 10 min, and 99.99% E. coli O157:H7 within 30 min. The chlorinated sample had better platelet adhesion and red blood cell cohesion than the control sample. The blood clotting index and fluid absorptive property of the samples enhanced after coating with modified mesoporous materials, indicating that the coated sample can prevent wound infection from bacteria and control hemorrhaging simultaneously. The coating of the modified mesoporous materials and N-halamines on cotton has not affect the bioactivity of cotton in the simulated body fluid. The active chlorine of the coated sample decreased 30% after soaking in the whole blood for 1 h. Considering the good antimicrobial efficacy against microorganisms and hemostasis property in blood control of the prepared materials, they have potentials for biomedical applications in wound dressing.

Antibacterial modification of PET with quaternary ammonium salt and silver particles via electron-beam irradiation.

Quaternary ammonium compound 2-dimethyl-2-hexadecyl-1-methacryloxyethyl ammonium bromide (DEHMA) was synthesized and grafted onto polyester (PET) fibers with acrylic acid (AA) via electron-beam (EB) irradiation process. The grafted fibers were soaked in AgNO3 solution for further improving antibacterial efficiency. SEM, FTIR, EDX, and XPS were used to characterize the treated PET samples. The antibacterial efficacy testing showed the grafted PET samples inactivated all Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli O157:H7) in 10min. After coated with silver ions, the antibacterial efficacy of the grafted PET with silver against S. aureus improved significantly. The EB irradiation process only caused a small degree of the breaking strength loss of the grafted PET fabrics which is acceptable in practical application.

Absorbent Pads Containing N-Halamine Compound for Potential Antimicrobial Use for Chicken Breast and Ground Chicken.

N-Halamines are a group of compounds containing one or more nitrogen-halogen covalent bond(s), and the high-energy halide bond provides a strong oxidative state so that it is able to inactivate microorganisms effectively. In this study, the shelf life of chicken breast and ground chicken packed with 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC, a member oft the N-halamines) treated absorbent pads was investigated during refrigerated storage. Fresh, processed chicken meat in packaging trays loaded with or without MC treated absorbent pads were stored at 4 °C for 11 days. The microbial counts in chicken meat as well as in the food pads were analyzed on days 1, 4, 7, and 11. MC treated pads reduced the levels of the main spoilage-related microorganisms (aerobic plate counts, lactic acid bacteria, Enterobacteriaceae, psychrotrophs, and Pseudomonas spp.) present in the absorbent pads by an average of 3.5 log CFU/g compared to the control. Microbial loads in chicken breast packed with MC coated absorbent pads were 0.3 log CFU/g lower than those in the control, and an approximate 0.2 log CFU/g reduction was observed for ground chicken. Neither the color nor the pH of the meat was negatively impacted by the presence of MC. The populations of inoculated Salmonella and Campylobacter in meat loaded with MC treated absorbent pads were on average lower than those in the controls. Pathogens in the control pads increased to 3.7 and 4.9 log CFU/g, while the MC treated absorbent pads lowered these two bacteria to under the detection limit (l.7 log CFU/g) throughout 11 days of storage.

Antimicrobial Activity of N-Halamine-Coated Materials in Broiler Chicken Houses.

The antimicrobial activity of 1-chloro-2,2,5,5-tetramethyl-4-imidazoidinone (MC), a nonbleaching N-halamine compound, was investigated on materials commonly used in broiler production, including stainless steel, galvanized metal, aluminum, plastic, and pressure-treated wood. MC aqueous solutions at 0.02, 0.04, and 0.06% were challenged with Salmonella Typhimurium and Campylobacter jejuni at 6 log CFU/mL, resulting in complete inactivation of both bacteria in 30 min with 0.06% MC. Follow-up experiments were performed using test materials treated with 0.1 and 1% MC and challenged with Salmonella Typhimurium and C. jejuni at 6 log CFU per coupon. Stability of MC on the various surfaces of testing materials was assessed, and the chlorine content of the materials was measured using iodometric thiosulfate titration over a 4-week period. Antimicrobial activities were evaluated by a sandwich test on each sampling day during 4 weeks of storage. On the samples treated with 1% MC, bacteria at 6 log CFU per coupon were completely inactivated within 2 h of contact time. The antimicrobial activity extended to 4 weeks, and the active chlorine atoms in the treated materials decreased from the initial 1016 to 1015 atoms per cm2. Overall, MC had high stability and long-lasting antimicrobial activity, which suggests that MC has high potential for use as a novel antimicrobial agent to lower the microbial load on broiler house materials.