Antimicrobial activity of nanocellulose conjugated with allicin and lysozyme

In this study, cellulose nanoparticles were prepared by acid hydrolysis, separately conjugated with allicin and lysozyme by a carbodiimide cross-linker, and characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Then, their antimicrobial properties were evaluated by the microdilution method and compared with allicin, lysozyme, and nanocellulose alone. The results showed that nanocellulose had few antimicrobial activities, but allicin-conjugated nanocellulose (ACNC) and lysozyme-conjugated nanocellulose (LCNC) had good antifungal and antibacterial effects against standard strains of Candida albicans, Aspergillus niger, Staphylococcus aureus, and Escherichia coli. Noticeably, although allicin and lysozyme had different minimum inhibitory concentrations (MICs) against all strains, the same quantity of MIC₅₀ and MIC₉₀ was observed for both ACNC and LCNC. The authors suggest that both ACNC and LCNC can be used in industries as an antimicrobial agent in food packaging, inside foodstuffs, and in textile materials.     

Antimicrobial porous hybrids consisting of bacterial nanocellulose and silver nanoparticles

The increasing resistance of pathogens and bacteria is a serious problem in the medical treatment of wounds and injuries. Therefore, new therapeutic agents are not solely based on antibiotics, but also on the use of antimicrobial metal nanoparticles. In this paper we present an innovative method to prepare porous hybrids consisting of bacterial nanocellulose (BNC) and silver nanoparticles (AgNPs). The stepwise modification is based on fairly simple chemical reactions already described for two-dimensional cellulose films. We transferred this method to the three-dimensional, porous network of BNC leading to an antimicrobial activation of its surface. Compared to former approaches, the ultrafine network structure of BNC is less damaged by using mild chemicals. The amount and distribution of the AgNPs on the modified BNC was investigated using scanning electron microscopy. The AgNPs are firmly immobilized on the top and bottom surface of the BNC by chemical interactions. Their size and quantity increase with an increasing concentration of AgNO₃ and extended reaction time in the AgNO₃ solution. A strong antimicrobial activity of the BNC-AgNP hybrids against Escherichia coli was detected. Furthermore, agar diffusion tests confirmed that this activity is restricted to the modified dressing itself, avoiding a release of NPs into the wound. Therefore, the produced hybrids could be potentially suited as novel antimicrobial wound dressings.     

Facile preparation and properties of superhydrophobic nanocellulose membrane

Superhydrophobic nanocellulose membrane was prepared by synergistically modifying biodegradable nanocellulose with low-carbon perfluoroorganosiloxane and ethyl orthosilicate. The effects of four kinds of low-carbon perfluoroorganosiloxanes with different structures and their ratio to ethyl orthosilicate on the hydrophobic properties of nanocellulose membrane were investigated, and then FT-IR, XPS, XRD, SEM, TEM, AFM, TG and contact angle goniometer were used to characterize the structure and hydrophobic properties of nanocellulose membrane before and after modification. It is found that when the molar ratio of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFOTMS) to ethyl orthosilicate (TEOS) is 1, the modified nanocellulose membrane PFOTMS-TEOS-CNF is loaded with silica nanoparticles both inside and on its surface, and a micro-nano hierarchical rough morphology with low surface energy is constructed. At this point, the root-mean-square roughness (Rq) of nanocellulose membrane is 112 nm, and the static contact angle of water droplet is 153.5°, successfully realizing superhydrophobicity. In addition, compared to unmodified nanocellulose membrane, PFOTMS-TEOS-CNF with better thermal stability includes an additional maximum weight loss rate temperature (491.2 °C). The above advantages markedly improve the shortcomings of pristine nanocellulose, such as superhydrophilicity and insufficient thermal stability, and also broadens its high-value application in many fields.     

胺基功能化咔唑共轭聚合物的合成及其光电性能研究

发展了新型含有胺基的支化烷基修饰的咔唑单元,并且与芴、咔唑、苯等单元通过Suzuki偶联反应共聚得到不同主链结构的水/醇溶共轭聚合物界面修饰材料,研究了主链结构的变化对材料光物理、电化学性能的影响.所有聚合物均被用作阴极界面材料应用于器件结构为ITO/PEDOT：PSS/P-PPV/界面层/Al的聚合物发光二极管中.在相同器件制备条件下,系统比较了不同主链结构的界面修饰材料在器件中的性能,并研究了性能差异的原因.器件研究结果表明,在高功函数金属Al阴极的聚合物发光二极管中,含胺基功能化咔唑单元的水/醇溶共轭聚合物材料由于界面偶极的形成,均表现出很好的电子注入/传输性能,与之对应的器件性能得到大幅提升.     

Synthesis and optoelectronic properties of amino-functionalized carbazole-based conjugated polymers

A series of alcohol soluble amino-functionalized carbazole-based copolymers were synthesized via Suzuki coupling reaction.The pendent amino groups endow them high solubility in polar solvents,as well as efficient electron injection capability from high work-function metals.The relationships between the photophysical and electrochemical properties and the polymer backbone structure were systematically investigated.These alcohol-soluble carbazole-based copolymers were used as cathode interlayers between the high work-function metal Al cathode and P-PPV emissive layer in polymer light-emitting diodes with device structure of ITO/PEDOT:PSS/P-PPV/interlayer/Al.The resulting devices exhibited improved performance due to the better electron injection/transporting ability of the designed copolymers from Al cathode to the light-emitting layer.     

Structure and thermal properties of bamboo viscose,Tencel and conventional viscose fiber

Comparative investigations of new regenerated cellulosic fibers, bamboo viscose fiber and Tencel, together with conventional viscose fibers have been carried out to explain the similarity and difference in their molecular and fine structure. The analyses jointly using SEM, XRD and IR reveal that all the three fibers belong to cellulose II. Tencel consists of longer molecules and has a greater degree of crystallinity, while bamboo viscose fiber has a lower degree of crystallinty. TG-DTG-DSC study shows three fibers resemble in thermal behavior with a two-step decomposition mode. The first step is associated to water desorption, suggesting that bamboo viscose fiber holds better water retention and release ability, the second a depolymerization and decomposition of regenerated cellulose, indicating that Tencel is more thermally stable in this process than bamboo and conventional viscose fiber.     

Thermal properties of flame retardant viscose fibers

This paper discusses the problem of the thermal properties of flame retarding additives based on phosphazene derivatives and of the commercial agents TomflamB, FlammexT23P and StockhausenW-20949, as well as of flame resistant viscose fibers containing the above agents. Results of this investigation showed the action of FlammexT23P, StockhausenW-20949 and phosphazene derivatives at lower temperature. TomflamB acted within a much wider range of temperatures. The flame retardant additives applied to viscose fibers change the thermal properties of the fiber material.     

Production of highly conductive textile viscose yarns by chemical vapor deposition technique: a route to continuous process

An oxidative chemical vapor deposition (OCVD) process was used to coat flexible textile fiber (viscose) with highly conductive polymer, poly (3,4‐ethylenedioxythiophene) (PEDOT) in presence of ferric (III) chloride (FeCl₃) oxidant. OCVD is a solvent free process used to get uniform, thin, and highly conductive polymer layer on different substrates. In this paper, PEDOT coated viscose fibers, prepared under specific conditions, exhibited high conductivity 14.2 S/cm. The effects of polymerization conditions, such as polymerization time, oxidant concentration, dipping time of viscose fiber in oxidant solution, and drying time of oxidant treated viscose fiber, were carefully investigated. Scanning electron microscopy (SEM) and FT‐IR analysis revealed that polymerization of PEDOT on surface of viscose fiber has been taken place and structural analysis showed strong interactions between PEDOT and viscose fiber. Thermogravimetric analysis (TGA) was employed to investigate the amount of PEDOT in PEDOT coated viscose fiber and interaction of PEDOT with viscose fiber. The effect of PEDOT coating on the mechanical properties of the viscose fiber was evaluated by tensile strength testing of the coated fibers. The obtained PEDOT coated viscose fiber having high conductivity, could be used in smart clothing for medical and military applications, heat generation, and solar cell demonstrators. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparative study on properties of nanocellulose derived from sustainable biomass resources

Cellulose - Nanocellulose, a unique and promising nanosized cellulose fibers extracted from renewable biomass, has gained much attention from both the scientific and industrial communities due to...     

Effect of isolation method on the properties of nanocellulose: a meta-analysis

Cellulose - There have been many kinds of research about nanocellulose isolation and its characterization. However, there are gaps in quantitative conclusion according to previous findings about...     

Some of the dielectric properties of cotton cellulose and viscose

Complex dielectric constants were measured at frequencies of 0.1–10,000 kc/s over the temperature range of 0–60°C in medicated cotton cellulose and viscose. In these fibers evidence is found for a new secondary relaxation process within the frequency region of 0.1–1 kc/s. The significance of the results is discussed.     

Antimicrobial properties of volatile phenylpropanes

The examination of antimicrobial structure-activity relationships of 93 volatile phenylpropanes (VPs) and 21 related aromatic compounds revealed a dependence of antimicrobial activity from the kind and number of substituents on the aromatic ring, their substitution pattern and microbial characteristics, such as Gram coloring and strain specific factors. Eugenol isomers were predominantly inhibitory in a concentration range from 25 to 2000 mg/L against all microorganisms tested, which were three strains of Escherichia coli and Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes, and Candida albicans. Etherified VPs were either less active or inactive depending on the type of side chain and/or substitution pattern. Differences in the antimicrobial activity of cis- and trans-isomers were observed. Species specific structure-activity relationships exist as was demonstrated with the Gram-negative bacteria (inactivity of E-ortho-eugenol) C. albicans (activity of di- and threefold methoxylated 1-propenylbenzenes), S. aureus and B. subtilis (activity of di-ortho methoxylated phenolic allylbenzenes and hydroquinone derivatives). With regard to the variety of observed specific effects and natural variation of susceptibility towards VPs according to literature reference data, the chances for successful prediction by computational analysis (QSAR) appear to be limited.     

Liquid crystal of nanocellulose whiskers’ grafted with acrylamide

12%acrylamide(AM) was grafted onto the surface of nanocellulose whiskers(NCW),which was self-assembled to be the chiral nematic suspension at 3%content.The acrylamide grafted NCW(AM-g-NCW) was characterized with Fourier Transform Infrared Spectroscopy(FTIR).The grafting ratio was measured by elemental analysis.The degrees of crystallinity of the AM-g-NCW were measured by X-ray diffraction(XRD).The liquid crystalline properties of the AM-g-NCW were investigated by the polarizing optical microscopy(POM).The AM-g-NCW was found to self-assembly to be a lyotropic state.     

Spectroscopic characterization of oxidized nanocellulose grafted with fluorescent amino acids

A hardwood bleached kraft pulp was oxidized by sodium hypochlorite using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and sodium bromide in water as catalysts to produce oxidized fibers. These oxidized fibers were mechanically disintegrated into oxidized nano-elements which were separated from the coarse components by centrifugation to obtain oxidized nanocellulose (ONC). The ONC was then coupled with fluorescent amino acids using a two step coupling procedure. First, the ONC was activated by N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide hydrochloride, forming a stable active ester in the presence of N-hydroxysuccinimide. Second, the active ester was reacted with the amino groups on the amino acids, forming an amide bond between the ONC and amino acids. The products (ONC-amino acids) were characterized by transmission electron microscopy and by different spectroscopic techniques such as absorption, emission, FTIR and XPS.     

Effect of the fine structure of viscose hydrocellulose on its adsorption properties

From the heat of wetting in water and the iodine adsorption measurements of certain hydrolytic residues prepared by the acid hydrolysis of viscose rayon in the absence and presence of FeCl₃, a comparison was made between their water adsorption capacity and iodine molecules. The data obtained revealed first that in the initial stages of acid action of the fibers the adsorption cites accessible to water or iodine molecules decrease to some extent, depending on the hydrolytic condition. Second, in the inner fine structure of the various residues examined, there remains a high proportion of cites accessible to water molecules that are inaccessible to iodine. These results are explained by the fact that the water molecules can penetrate the submicroscopic structure of cellulose chains by molecular forces and the swelling effect.     

Influence of drying method on the material properties of nanocellulose I: thermostability and crystallinity

The effect of drying method on selected material properties of nanocellulose was investigated. Samples of nanofibrillated cellulose (NFC) and cellulose nanocrystals (CNC) were each subjected to four separate drying methods: air-drying, freeze-drying, spray-drying, and supercritical-drying. The thermal stability and crystallinity of the dried nanocellulose were evaluated using thermogravimetric analysis (TGA) and X-ray diffraction. Supercritical-drying produced NFCs with the least thermal stability and the lowest crystallinity index. Air-drying or spray-drying produced NFCs which were more thermally stable compared with freeze-dried NFCs. The CNCs dried by the three methods (air-drying, freeze-drying, and spray-drying) have similar onset temperature of thermal degradation. The different drying methods resulted in various char weight percentages at 600 °C for the dried NFCs or CNCs from TGA measurements. The dried NFCs are pure cellulose I while the dried CNCs consist of cellulose I and II. The calculated crystallinity indices differ with each drying method. The cellulose II content in CNCs changes as a function of drying method. For the application of nanocellulose in non polar thermoplastics, spray-dried products are recommended according to their higher thermal stability and higher crystallinity index.     

Rheological properties of nanocellulose suspensions: effects of fibril/particle dimensions and surface characteristics

The rheological properties of aqueous suspensions based on three different nanocelluloses were compared. One system was obtained via acid hydrolysis (thus yielding crystalline nanocellulose, CNC) and the other two from mechanical shearing, but from different origins and subjected to different pretreatments. Of the latter two, one was considered to be a rather typical cellulose nanofibril (CNF) suspension whereas the other was a kind of intermediate between CNF and CNC. All three nanocellulose elements differed in dimensions as evident from transmission electron microscopy and atomic force microscopy. With regard to the length of the fibrils/particles, the three nanocelluloses formed three distinct groups with lengths between 200 and slightly more than 800 nm. The three cellulosic elements were also subjected to a TEMPO-mediated oxidation yielding a similar carboxylate content in the three systems. Furthermore, the TEMPO-oxidized elements were grafted with poly(ethylene glycol) (PEG). The amount of grafted PEG was about 35 wt%. The shear viscosity, the storage modulus and the loss modulus of suspensions of the unmodified, the TEMPO-oxidized and the grafted nanocelluloses were determined at room temperature and the solids content of the suspensions was varied between 0.7 and 2.0 wt%. It was concluded that the rheological properties varied significantly between the suspensions depending on the dimensions of the cellulosic elements and their surface characteristics. In this context, the length (or the aspect ratio) of the particles played a very important role.     

Nanocomposites prepared by in situ enzymatic polymerization of phenol with TEMPO-oxidized nanocellulose

The objective of this study was to prepare nanocomposites based on polyphenols and nanocellulose fibers using relatively benign processing. To accomplish this, phenol was polymerized using horseradish peroxidase in the presence of TEMPO-oxidized nanocellulose. The polyphenol-nanocellulose composite was insoluble in organic solvents but the individual components were soluble. SEM imaging of fracture surfaces of polyphenol, nanocellulose, and composite indicated brittle failure in polyphenol and nanocellulose but ductile failure in the composite pointing to a potential synergistic effect from the addition of the components. Polyphenol existed as spherical or near-spherical “clusters” that were ca. 10 μm in the absence of nanocellulose and ca. 0.1 μm in the presence of nanocellulose. The observed change in structure corresponded to changes in the thermal stability because the composite was more thermally stable than the components. FT-IR analysis of polyphenol-nanocellulose composites showed physical and chemical interactions between the fiber and matrix. This study is a significant improvement in forming nanocomposites without the intensive processing usually required for dispersion.