Studies on physico-chemical and antibacterial properties of grafted pullulans solutions

The physico-chemical properties of three grafted pullulans (P) having linked poly(3-acrylamidopropyl)trimethylammonium chloride (pAPTAC) as side chains (P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 with 22.53, 29.05, and 34.51 (wt.%) of pAPTAC content in polymer, respectively) and possessing polyelectrolyte character were determined by light scattering analysis. All grafted pullulan aqueous solutions were tested in the presence of 0.5 M NaCl, KCl, NaNO₃ or KNO₃. The biggest associations were recorded in 0.5 M NaCl aqueous solutions for P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 according to the maximum values for R_g extracted from MALLS (multiangle laser light scattering) measurements. Also, the dominant conformation in salted solution of these polyelectrolytes was random coil as Debye plot analysis revealed. Antibacterial activity was tested by Kirby–Bauer diffusion method and all grafted pullulans dissolved in aqueous solutions of 0.5 M NaCl have developed inhibition zone against Staphylococcus aureus (ATCC 25923).     

Inhibitory parameters of the essential oil and various extracts of Metasequoia glyptostroboides Miki ex Hu to reduce food spoilage and food-borne pathogens

The aim of this work was to examine the chemical composition of the essential oil and various solvent extracts isolated from the floral cone of Metasequoia glyptostroboides Miki ex Hu and to test their efficacy against a diverse range of organisms comprising food spoilage and food-borne pathogenic bacteria. The chemical composition of essential oil isolated by hydrodistillation was analysed by GC-MS. It was determined that 59 compounds, which represented 97.06% of total oil, were present in the oil. The oil contains mainly α-pinene (29.54%), totarol (9.37%), α-thujene (8.63%), bornylene (8.63%), β-caryophyllene (4.40%), totarol acetate (3.98%), δ-3-carene (3.19%) and 2-β-pinene (2.25%). The oil was found containing mainly the oxygenated mono- and sesquiterpenes and their respective hydrocarbons. Antibacterial activity of essential oil, methanol extract and various organic sub-fractions of methanol extract of M. glyptostroboides was determined in vitro using agar diffusion method and MIC determination test against eleven (four Gram-positive, seven Gram-negative) bacterial strains including food spoilage and food-borne pathogens. The essential oil (5 μl/ml, corresponding to 1000 ppm/disc), methanol extract and various organic sub-fractions (7.5 μl/ml, corresponding to 1500 ppm/disc) of M. glyptostroboides exhibited great potential of antibacterial activity against four Gram-positive bacteria such as Bacillus subtilis (ATCC 6633), Listeria monocytogenes (ATCC 19166), Staphylococcus aureus (KCTC 1916), S. aureus (ATCC 6538) and one Gram-negative bacterium, Pseudomonas aeruginosa (KCTC 2004). The zones of inhibition of different concentrations of essential oil, methanol extract and its derived various organic sub-fractions against the tested bacteria were found in the range of 10 ∼ 20 mm and the MIC values were recorded between 125 and 1000 μg/ml. This study shows that M. glyptostroboides mediated essential oil and extracts can be applied in food industries as a natural preservatives or flavoring additives to control food spoilage and food-borne pathogenic bacteria causing severe destruction in food.     

环保抗菌玻璃、陶瓷生产中TiO2的应用研究

二氧化钛的光催化作用被人们认识以来,成为最有希望的环境友好催化新技术,已经越来越多的运用到环保建材当中,环保抗菌玻璃和陶瓷就是其中最有代表性的产品。     

Synthesis,characterization, electrochemical behavior,thermal study and antibacterial/antifungal properties of some new zinc(II) coordination compounds

A novel symmetrical Schiff base ligand was prepared by condensation reaction of 2,2-dimethyl-1.3-diaminopropane and (E)3-(2nitrophenyl)acrylaldehyde. The ligand and its Zn(II) coordination compounds were well characterized by the elemental analysis, FTIR, ¹H, ¹³C NMR, UV–vis spectra and molar conductance. Thermal behaviors of all compounds were investigated from the room temperature to 600 °C with a heating rate of 10 °C/min. Furthermore some decomposition thermo-kinetic parameters were evaluated by Coats–Redfern equation at each decomposition step. Electrochemical properties of ligand and its complexes were studied by cyclic voltammetry technique. Also antibacterial/antifungal activities of the ligand and its complexes were tested against three Gram-negative bacteria Escherichia coli (ATCC 25922), Salmonella spp. and Pseudomonas aeruginosa (ATCC 9027) and two Gram-positive bacteria Staphylococcus aureus (ATCC 6538) and Corynebacterium renale and also three fungi (Aspergillus niger, Penicillium chrysogenum and Candida albicans). The results exhibited suitable antibacterial/antifungal properties for ligand and Zn(II) complexes. The study has shown that the complexation of ligand to zinc center lead to enhancement of antibacterial/antifungal activity.     

Co-Doped ZnO Nanoparticles:Structural,Morphological,Optical,Magnetic and Antibacterial Studies

Un-doped and Co-doped ZnO nanoparticles （NPs） with different weight ratios （0.5, 1.0, 1.5, and 2.0 wt% of Co） were synthesized by a facile and rapid microwave-assisted combustion method using urea as a fuel. The prepared NPs were characterized by X-ray diffraction （XRD）, high resolution scanning electron microscopy （HR-SEM）, energy dispersive X-ray analysis （EDX）, diffuse reflectance spectroscopy （DRS）, photoluminescence （PL） spectroscopy and vibrating sample magnetometry （VSM）. XRD patterns refined by the Rietveld method indicated that Co-doped ZnO had a single pure phase with wurtzite structure suggesting that Co^2＋ ions would occupy Zn^2＋ ionic sites within the ZnO crystal lattice. Interestingly, the morphology was found to convert substantially from grains to nanoparticles with close-packed periodic array of hexagonal-like shape and then into randomly distributed spherical NPs with the variation of Co-content. The optical band gap estimated using DRS was found to be red-shifted from 3.22 eV for the un-doped ZnO NPs then decrease up to 2.88 eV with increasing Co-content. PL spectra showed a strong green emission band thus confirming the formation of pure single ZnO phase. Magnetic studies showed that Co-doped ZnO NPs exhibited room temperature ferromagnetism （RTFM） and that the saturation magnetization attained a maximum value of 2.203 × 10^-3 emu/g for the highest Co-content. The antibacterial studies performed against a set of bacterial strains showed that the 2.0 wt% Co-doped ZnO NPs possessed a greater antibacterial effect.     

Silver nanoparticles enhance Pseudomonas aeruginosa PAO1 biofilm detachment

Objectives: Silver nanoparticles (AgNPs) with a size ranging from 7 to 70?nm were synthesized using the ascorbic acid-citrate seed-mediated growth approach at room temperature.

Methods: The 8?nm silver particles were prepared using gallic acid in alkaline conditions and used as seed to prepare AgNPs.

Results: The presence of ascorbic acid and citrate allows the regulation of size and size distribution of the nanoparticles. The increase in free silver ion-to-seed ratio (Ag⁺/Ag⁰) resulted in changes of particle shape from spherical to pseudo-spherical and minor cylindrical shape. Further, a repetitive seeding approach resulted in the formation of pseudo-spherical particles with higher polydispersity index and minor distributions of tetrahedral particles. Citrate-capped AgNPs were stable and did not agglomerate upon centrifugation. The effect of AgNPs on biofilm reduction was evaluated using static culture on 96-well microtiter plates. Results showed that AgNPs with the smallest average diameter were most effective in the reduction of Pseudomonas aeruginosa biofilm colonies, which accounted for 90% of removal.

Conclusion: The biofilm removal activities of the nanoparticles were found to be concentration-independent particularly for the concentration within the range of 80–200?µg/mL.     

固定化溶菌酶的氧化石墨烯/聚醚砜杂化超滤膜制备及抗菌性能研究

以氧化石墨烯(GO)为固定酶载体,在水溶液中通过静电吸附及氢键作用实现溶菌酶(Ly)的固定化得到GO-Ly。并将已固定化酶的GO为添加剂,以聚醚砜为膜材料,采用相转化法制备杂化超滤膜。考察了添加剂含量对膜形态、亲水性、分离性能、力学性能及抗菌性能的影响。结果表明,GO-Ly的加入使杂化膜的亲水性及纯水通量得到明显提高,同时拉伸强度也得到一定改善;尤其当GO-Ly添加量为1.5%(质量分数)时,膜的纯水通量达到318 L/(m2.h),并且对聚乙烯醇(PVA 30 000～70 000)的截留率维持在99%以上,对大肠杆菌的抑菌率可达68%。     

Morphology-dependent antibacterial activities of Cu2O

Cubic and octahedral Cu₂O microcrystals were synthesized by the reduction of a copper-ligand complex solution with glucose under microwave irradiation using ethylenediaminetetraacetic acid (EDTA) and N,N,N′,N′-tetramethyl ethylenediamine (TMEDA) as ligands. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) confirmed that the surfaces of the cubic and octahedral of Cu₂O microcrystals had {100} and {111} lattice planes. The antibacterial activity of the Cu₂O microcrystals against E. coli was examined using optical density (OD) methods. The antibacterial activity of the cubic Cu₂O crystals was superior to that of the octahedral Cu₂O crystals. The mechanism of the specific morphology-controlled synthesis of Cu₂O and their morphology-dependent antibacterial activity are discussed.     

Combination of photocatalytic and antibacterial effects of silver oxide loaded on titania nanotubes

Silver nanoparticles were photodeposited on titania nanotubes and their antibacterial activity was tested. Investigation of the structure and morphology of the nanostructures showed nanometer size silver oxide particles homogeneously distributed on titania nanotubes. Furthermore the modified titania nanotubes were spin-coated as thin films and their antibacterial activity was examined under visible light irradiation and in complete darkness. Although silver oxide loaded titania nanotubes (TiNT-AgO) has a potential for antibacterial activity in both conditions with and without light irradiation, enhanced activity was observed in visible light irradiation condition.     

家用空调器净化技术的应用与实验研究

介绍家用空调器中常见的净化技术,对不同技术的净化效果进行了实验与分析.实验结果表明,组合功能净化效果明显优于单一功能;换气功能对去除挥发性有机化合物(TVOC)有效,去除效果与换气量成正比;电离方式对去除可吸入颗粒物(PM10)、甲醛(HCHO)、菌落总数(ABC)效果较好.