反相高效液相色谱法测定荧光增白剂CBS中N,N-二甲基甲酰胺的残留量

建立了反相高效液相色谱外标法检测荧光增白剂CBS(即CF-351)中N,N-二甲基甲酰胺(DMF)残留量的方法。使用Accurasil C18(150 mm×4.6 mm,5 μm)反相液相色谱柱,以甲醇-水为流动相梯度洗脱,流速为1.0 mL/min,检测波长为205 nm,柱温为30 ℃,进样量为5 μL。在上述条件下,在DMF质量浓度为0.19～141 mg/L范围内,其峰面积与质量浓度的线性关系良好。在加标水平（用质量分数表示）为0.2344%和0.4678%时,回收率为98.4%～107.3%。本方法最低检出限(LOD)为0.019%（质量分数）,峰面积的相对标准偏差(RSD)为1.73%。此方法可快速、准确地测定出荧光增白剂CBS中DMF的残留量。     

Harvesting fibrils from bacterial cellulose pellicles and subsequent formation of biodegradable poly-3-hydroxybutyrate nanocomposites

Bacterial cellulose has the potential to be used as a biodegradable, reinforcing component in composites due to its high strength and crystallinity. However it is often problematic to use in this context as it is difficult to separate its extensively bonded fibril network. This means it can be difficult for it to be incorporated as a fine dispersion into a composite and for the true benefits of the nanofibres to be realised in terms of physical property improvement in a conventional polymer format such as injection moulding. The method of sonication (using a range of experimental conditions) was utilised to harvest fibrils from the interwoven mesh of the cellulose pellicle, and then disperse them in different solvents to allow blending and subsequent casting. The novel step identified in this process was the sonication harvesting of the nanofibres undertaken on the highly hydrated as-received pellicle fresh from the reaction media (not the dried pellicle which could not be easily separated in the selected solvent). This unique step of harvesting directly from the fresh pellicle together with conventional sonication for dispersion in chloroform produced a bacterial cellulose/poly-3-hydroxybutyrate nanocomposite which showed excellent nanofibre dispersion and significant improvement in mechanical properties.     

Thin-layer chromatography of tin on a cellulose support using fluorescent chloro-complexes

Summary A TLC method has been developed for direct quantitative estimation of Sn²⁺. The ion was converted to fluorescent chloro-complexes by HCl, in the presence of NaCl or KCl, on a cellulose support, and the complexes were estimated fluorometrically (excitation at 254 nm; measurement, in presence of KCl: 474 nm, in presence of NaCl: 445 nm). Reliable quantitative results were obtained with length concentrations of 0.8 g/cm with respect to Sn. Detection is possible with 0.5 g/cm.     

Characteristics and safety of nano-sized cellulose fibrils

A finely ground fibrillated cellulose was fractionated into separate size fractions. The characteristics of the smallest size fractions were studied, and the toxicity to humans was tested as part of a safety assessment. Morphological studies performed with state-of-the-art methods, such as scanning electron microscopy and atomic force microscopy, showed that the fraction obtained consisted of long thin fibrils but also larger fibril agglomerates, and spherical particles were present. The finest fraction did not show any sub-lethal effects as assessed by RNA inhibition test in vitro, nor were there any indications of genotoxicity as tested by the Ames test in vitro. Systemic effects tested in vivo with the nematode were also absent. No cytotoxic effects were seen in the highest tolerated dose test in vitro, but some indication of cytotoxicity was observed in the total protein content test in vitro at the highest sample concentration. The significance of this toxicity test result should be addressed in relation to the other toxicity tests, in which no toxicity was observed, with special emphasis on the in vivo test. Given this, the overall toxicity analyses support the conclusion that nano-scale cellulose fibrils can be considered to be safe towards humans. However, the reason for the positive cytotoxicity test result and, in addition, the effect of the biocide used in sample preservation on the toxicity tests need to be clarified before generalizing these results and declaring nanocellulose to be unambiguously safe.     

Production of bacterial cellulose by Gluconacetobacter sp. RKY5 isolated from persimmon vinegar

The optimum fermentation medium for the production of bacterial cellulose (BC) by a newly isolated Gluconacetobacter sp. RKY5 was investigated. The optimized medium composition for cellulose production was determined to be 15 g/L glycerol, 8 g/L yeast extract, 3 g/L K2HPO4, and 3 g/L acetic acid. Under these optimized culture medium, Gluconacetobacter sp. RKY5 produced 5.63 g/L of BC after 144 h of shaken culture, although 4.59 g/L of BC was produced after 144 h of static culture. The amount of BC produced by Gluconacetobacter sp. RKY5 was more than 2 times in the optimized medium found in this study than in a standard Hestrin and Shramm medium, which was generally used for the cultivation of BC-producing organisms.     

Development of conductive bacterial cellulose foams using acoustic cavitation

Bacterial cellulose (BC) has found applications in various fields ranging from healthcare to electronics. Functionalization of cellulose to impart conductive properties has been met with challenges due to superficial coating rather than uniform interactions with the conducting polymers. In this work, mechanical disruption is shown to be a facile strategy to develop BC-PEDOT:PSS conductive foams without the use of any harsh chemical treatments to functionalize cellulose. The strategy allows for uniform polymer intercalation with the cellulose nanofibers imparting superior conductive properties to the functional material. The conductive foams with low PEDOT:PSS ratio exhibit conductivity of 0.7 S/cm and are cytocompatible with human dermal fibroblasts (HDFa) cells.

     

Live-cell-permeant thiophene fluorophores and cell-mediated formation of fluorescent fibrils

In our search for thiophene fluorophores that can overcome the limits of currently available organic dyes in live-cell staining, we synthesized biocompatible dithienothiophene-S,S-dioxide derivatives (DTTOs) that were spontaneously taken up by live mouse embryonic fibroblasts and HeLa cells. Upon treatment with DTTOs, the cells secreted nanostructured fluorescent fibrils, while cell viability remained unaltered. Comparison with the behavior of other cell-permeant, newly synthesized thiophene fluorophores showed that the formation of fluorescent fibrils was peculiar to DTTO dyes. Laser scanning confocal microscopy of the fluorescent fibrils showed that most of them were characterized by helical supramolecular organization. Electrophoretic analysis and theoretical calculations suggested that the DTTOs were selectively recognized by the HyPro component of procollagen polypeptide chains and incorporated through the formation of multiple H-bondings.     

Characterization of water-soluble exopolysaccharides from Gluconacetobacter xylinus and their impacts on bacterial cellulose crystallization and ribbon assembly

Gluconacetobacter xylinus has the ability to produce different types of water soluble exopolysaccharides (EPS). Those EPS have different levels of association to bacterial cellulose (BC). At least a portion of the EPS can be released from the BC by 0.1 to 4 M NaOH solution treatments. Hard to extract EPS (HE-EPS) released by 4 M NaOH solutions have been characterized and contain approximately 75 % mannose and 25 % glucose. To study the effect of the EPS on BC synthesis, purified EPS were added to the medium at the start of cultivation and the BC produced was characterized. Results showed that the presence of HE-EPS in the culture medium interfered with the alignment of the BC crystals, but did not reduce crystal size. This is in contrast to similar studies performed using xyloglucan, xylan and glucomannan. The width of the average ribbon increased by 60 % when HE-EPS levels increased in the medium, which indicated that the HE-EPS could also modulate the bundling of cellulose ribbons. Based on the data we propose a mechanism for how HE-EPS alters cellulose formation and assembly. The addition of HE-EPS disturbs the preferential crystal orientation and increases the spacing of cellulose microfibrils without affecting crystallization by associating with ordered cellulose prior to physical aggregation or bundling.     

Production of bacterial cellulose by Gluconacetobacter sp. RKY5 isolated from persimmon vinegar

The optimum fermentation medium for the production of bacterial cellulose (BC) by a newly isolated Gluconacetobacter sp. RKY5 was investigated. The optimized medium composition for cellulose production was determined to be 15 g/L glycerol, 8 g/L yeast extract, 3 g/L K₂HPO₄, and 3 g/L acetic acid. Under these optimized culture medium, Gluconacetobacter sp. RKY5 produced 5.63 g/L of BC after 144 h of shaken culture, although 4.59 g/L of BC was produced after 144 h of static culture. The amount of BC produced by Gluconacetobacter sp. RKY5 was more than 2 times in the optimized medium found in this study than in a standard Hestrin and Shramm medium, which was generally used for the cultivation of BC-producing organisms.     

Reactivities of cellulases from fungi towards ribbon-type bacterial cellulose and band-shaped bacterial cellulose

We have investigated the reactivities of various cellulases onribbon-type bacterial cellulose (BC I) and band-shaped bacterial cellulose (BCII) so as to clarify the properties of different cellulases. BC I waseffectively hydrolyzed by exo-type cellulases from different fungi from twicetofour times as much as BC II, but endo-type cellulases showed little differencein reactivity on those substrates. One of the endo-type cellulases, EG II fromTrichoderma reesei, degraded BC II more rapidly thanexo-type cellulases even in the production of reducing sugars. The degree ofpolymerization (DP) of BC II was rapidly decreased by endo-type cellulases atanearly stage, while exo-type cellulases did not cause the decrease of DP atthe initial stage, though the decrease of DP was observed after an incubation of24 h. All exo-type cellulases adsorbed on BC I and BC II,whileendo-type cellulases except for EG II adsorbed slightly on both substrates. Itwas interesting to observe EG II adsorbed on BC I but not on BC II. It issuggested that the adsorption of enzyme on cellulose is important for thedegradation of BC I, but not for BC II. It is proposed that the ratio of aspecific activity of each enzyme between BC I and BC II represents thedifference in the mode of action of cellulase. Furthermore, the K _RW value, which we can calculate from thedecrease of DP/reducing sugar produced, is effective for discriminating themode of action of cellulase, especially the evaluation of randomness in thehydrolysis of cellulose by endo- and exo-type cellulases.     

Synthesis and characterization of hydroxypropyl cellulose from bacterial cellulose

Bacterial cellulose produced by Acetobacter xylinum has been reacted with propyleneoxide to synthesize hydroxypropyl cellulose(HPC) under different reaction conditions while diluted by toluene. The effects of mass ratio of bacterial cellulose to propyleneoxide, dilutability of toluene, reaction temperature(T) and time(t) were investigated by series of experiments. The degree of substitution(DS), hydroxypropyl content(A) and yield(η) were compared. The optimized product exhibited cold-water solubility and hot-water gelatinization in aqueous medium. Further study was carried out with FTIR, TGA, XRD, SEM and 13C-NMR for characterization. The water/air contact angle measurement reveals that it is a good hydrophobic material with good mechanical properties.     

Sorption of a fluorescent whitening agent (Tinopal CBS) onto modified cellulose fibers in the presence of surfactants and salt

The combined effect of salt (10 mmol L(-1)) and surfactants on the sorption of the fluorescent brightener 4,4'-distyrylbiphenyl sodium sulfonate (Tinopal CBS) onto modified cellulose fibers was studied. Sorption efficiencies with both cationic and anionic surfactants were evaluated. Emission spectroscopy was used for quantitative analysis since Tinopal has an intense fluorescence. The sorption efficiency of the brightener is greater for solutions containing a cationic surfactant (DTAC) below the critical micelle concentration (cmc), while for an anionic surfactant (SDS) above its cmc the efficiency is greater. The profile of the sorption isotherms were interpreted in terms of the evolution of surfactant aggregation at the fiber/solution interface. Salt influences the efficiency of the Tinopal sorption on the modified cellulose fibers either because it decreases the cmc of the surfactants or because the ions screen the surface charges of the fiber which decreases the electrostatic interaction among the charged headgroup of the surfactant and the charged fiber surface.     

In vivo measurement of vascular modulation in experimental tumors using a fluorescent contrast agent

Abstract We compared the effectiveness of three optical techniques based on fluorescence imaging and spectroscopy with indocyanine green (ICG) contrast agent to evaluate in vivo the disruption of the active vasculature induced by a vascular targeting agent. The blood perfusion of the MDA-MB-435 tumor model transplanted in nude mice was estimated from the signal of the contrast agent measured immediately after its systemic injection in mice. Optical measurements were performed using a fluorescence imaging setup and a fiber-based time correlated single photon counting (TCSPC) apparatus. This latter apparatus was used to measure the tumor fluorescence in transmittance geometry and the change in the basal optical absorption induced by the contrast agent, thus providing an alternative estimation of the blood content in the tumor. Mice were divided into four groups. Three groups were treated with different doses of the vascular disrupting agent ZD6126, the fourth group (control group) received the drug vehicle only. Optical measurements were carried out 3 h after pharmacologic treatment. After 24 h, mice were killed, tumors were excised and the extent of necrosis was evaluated with standard histologic analysis. On fluorescence imaging ICG emission from tumors of mice treated with ZD6126 significantly was lower compared with the emission from control mice. The histologic sections also showed a significantly higher amount of necrosis in tumors of treated mice. Both these findings, which correlate with each other, indicate an effective vascular shutdown induced by the drug. However, ICG fluorescence measured with the TCSPC apparatus in transmittance geometry and the estimate of the change in optical absorption did not allow a statistically significant differentiation between treated and control groups.     

Synthesis of cationic bacterial cellulose using a templated metal phenolic network for antibacterial applications

Cellulose - Bacterial cellulose (BC) has been an attractive bio-based material for biomedical applications due to its biocompatibility, non-toxicity, ultrafine nanofibril network, robust mechanical...     

Complete dechlorination of pentachlorophenol using palladized bacterial cellulose in a rotating catalyst contact reactor

A rotating catalyst contact reactor (RCCR) was developed which consisted of palladized bacterial cellulose immobilized on acrylic discs for hydrodechlorination of pentachlorophenol (PCP). More than 99% of 40 mg L(-1) PCP was dechlorinated to phenol in the presence of hydrogen in batch mode at initial pH values of 5.5 and 6.5 within 2 h of reaction with stoichiometric release of free chloride. The rate of PCP dechlorination was found to be independent of rotational speed of discs. PCP (40 mg L(-1)) hydrodechlorination experiments were also conducted using RCCR in continuous flow mode at hydraulic retention times of 1 and 2 h. The average outlet PCP concentrations revealed that liquid phase in RCCR closely resembled that of a continuous flow complete mix reactor (CFMR). Approximately 12 and 11 L of 40 mg L(-1) PCP (pH 6.5) could be treated in RCCR with 99 and 80% efficiencies in batch and continuous flow modes, respectively without any appreciable loss of the catalytic activity. These results suggested reusability of palladized bacterial cellulose which in turn is expected to substantially reduce the cost of treatment process. Thus RCCR seems to have high potential for treatment of ground water contaminated with chlorinated organic compounds. Dried palladized bacterial cellulose has been used as a material for electrodes in a fuel cell. However, its application as a hydrodechlorination catalyst in a reactor operating under room temperature and atmospheric pressure has not been reported to the best of our knowledge. Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses suggested the irreversible deposition of palladium (Pd 0) particles on the bacterial cellulose fibrils.     

Synthesis and characterization of microcrystalline cellulose produced from bacterial cellulose

In this study, microcrystalline cellulose (MCC) was prepared from the acid hydrolysis of bacterial cellulose (BC) produced in culture medium of static Acetobacter xylinum. The MCC-BC produced an average particle size between 70 and 90 μm and a degree of polymerization (DP) of 250. The characterization of samples was performed by thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy (SEM). The MCC shows a lower thermal stability than the pristine cellulose, which was expected due to the decrease in the DP during the hydrolysis process. In addition, from X-ray diffractograms, we observed a change in the crystalline structure. The images of SEM for the BC and MCC show clear differences with modifications of BC fiber structure and production of particles with characteristics similar to commercial MCC.     

Optical imaging of bacterial infection in living mice using a fluorescent near-infrared molecular probe

An optical imaging probe was synthesized by attaching a near-infrared carbocyanine fluorophore to an affinity group containing two zinc(II) dipicolylamine (Zn-DPA) units. The probe has a strong and selective affinity for the surfaces of bacteria, and it was used to image infections of Gram-positive S. aureus and Gram-negative E. coli bacteria in living nude mice. After intravenous injection, the probe selectively accumulates at the sites of localized bacterial infections in the thigh muscles of the mice.     

Enzymatic degradation of trichloroethylene using enzyme extracts isolated from a bacterial consortium

Degradation of trichloroethylene (TCE) using crude enzyme extracts from a bacterial consortium was examined for wastewater treatment. The effects of pH, chemical induction, and cofactor were investigate. Enzyme extracts showed an optimal activity (3.03±0.03 mg of TCE/[mg of protein·d]) at neutral pH (6.5–7.5). In an attempt to increase the production of effective enzymes for TCE degradation, chemical induction using both toluene and TCE in the growth of the bacterium consortium was conducted. Although the induction increased the overall production of protein by about fourfold, the activity of the extracts was only slightly improved (up to 3.40 mg of TCE/[mg of protein·d]), indicating that the induction did not specifically enhance the production of TCE-degrading enzymes. Interestingly, the addition of a cofactor (up to 0.02 mg/mL), NADH, led to an initial reaction rate of 5.30±0.05 mg of TCE/(mg of protein·d). This observation demonstrated that the availability of the cofactor played an important role in determining the overall degradation reaction rates. The observations with NADH were in agreement with the assumption that toluene monooxygenases (which are NADH dependent) are the key enzymes for the degradation reactions.