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排序方式: 共有1367条查询结果,搜索用时 15 毫秒
61.
Broad Spectrum Anti-Bacterial Activity and Non-Selective Toxicity of Gum Arabic Silver Nanoparticles
Adewale O. Fadaka Samantha Meyer Omnia Ahmed Greta Geerts Madimabe A. Madiehe Mervin Meyer Nicole R. S. Sibuyi 《International journal of molecular sciences》2022,23(3)
Silver nanoparticles (AgNPs) are the most commercialized nanomaterials and presumed to be biocompatible based on the biological effects of the bulk material. However, their physico-chemical properties differ significantly to the bulk materials and are associated with unique biological properties. The study investigated the antimicrobial and cytotoxicity effects of AgNPs synthesized using gum arabic (GA), sodium borohydride (NaBH4), and their combination as reducing agents. The AgNPs were characterized using ultraviolet-visible spectrophotometry (UV-Vis), dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The anti-bacterial activity was assessed using agar well diffusion and microdilution assays, and the cytotoxicity effects on Caco-2, HT-29 and KMST-6 cells using MTT assay. The GA-synthesized AgNPs (GA-AgNPs) demonstrated higher bactericidal activity against all bacteria, and non-selective cytotoxicity towards normal and cancer cells. AgNPs reduced by NaBH4 (C-AgNPs) and the combination of GA and NaBH4 (GAC-AgNPs) had insignificant anti-bacterial activity and cytotoxicity at ≥50 µg/mL. The study showed that despite the notion that AgNPs are safe and biocompatible, their toxicity cannot be overruled and that their toxicity can be channeled by using biocompatible polymers, thereby providing a therapeutic window at concentrations that are least harmful to mammalian cells but toxic to bacteria. 相似文献
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63.
Marwa Sta Graziele Aguiar Abilio A. J. Forni Simone F. Medeiros Amilton M. Santos Nicole R. Demarquette 《应用聚合物科学杂志》2020,137(11):48472
In this work, nanofiber scaffolds for surface drug delivery applications were obtained by electrospinning poly(N-vinylcaprolactam) (PNVCL) and its blends with poly(ε-caprolactone) and poly(N-vinylcaprolactam)-b-poly(ε-caprolactone). The process parameters to obtain smooth and beadless PNVCL fibers were optimized. The average fibers diameter was less than 1 μm, and it was determined by scanning electron microscopy analyses. Their affinity toward water was evaluated by measuring the contact angle with water. The ketoprofen release behavior from the fibers was analyzed using independent and model-dependent approaches. The low values of the release exponent (n < 0.5) obtained for 20 and 42 °C, indicating a Fickian diffusion mechanism for all formulations. Dissolution efficiencies (DEs) revealed the effect of polymer composition, methodology used in the electrospinning process, and temperature on the release rate of ketoprofen. PNVCL/poly(N-vinylcaprolactam)-b-poly(ε-caprolactone)-based nanofibers showed greater ability to control the in vitro release of ketoprofen, in view of reduced kinetic constant and DE, making this material promising system for controlling release of hydrophobic drugs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48472. 相似文献
64.
Vinícius L. Carvalho Camila Safieddine Nicole R. Demarquette Luís A. Pinheiro 《应用聚合物科学杂志》2020,137(3):48295
The Friedel–Crafts alkylation reaction has been applied to reactively compatibilize a ternary blend of high-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS). The reactions were carried out in an internal mixer using varying catalyst concentrations. The resulting compatibilizer was quantified after Soxhlet extraction. In addition, p-substitution due to the grafting of alkyl groups onto the PS benzene ring was identified via nuclear magnetic resonance spectroscopy. The size of the PS domain in the reactive compositions is decreased by 80%. Moreover, the phase in which PS droplets were dispersed varied, that is, in the nonreactive blends they were found in the PP phase and in the reactive blends they shifted toward the HDPE phase. The effect of the compatibilizing agent was to improve the mechanical properties of the blend. Even with the lowest catalyst content, the properties of elongation-at-break, tensile strength, toughness, and elastic modulus showed improvements. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48295. 相似文献
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Vladimir Totolin Ichiro Minami Christoph Gabler Joseph Brenner Nicole Dörr 《Tribology Letters》2014,53(2):421-432
The assessment of ionic liquids (ILs) as lubricants in several tribological systems has shown their ability to provide remarkable reduced friction and protection against wear, whether they are used as additives or in the neat form. However, their corrosion and limited solubility in non-polar hydrocarbon oils represent the bottleneck-limiting factors for the use of ILs as lubricants. Therefore, in order to tackle these problems, mixtures of alkylborane–imidazole complexes with one halogen-free IL as additive were used in this study. The knowledge of the additive–surface interactions and hence the understanding of tribological properties are an important issue for lubricant formulations and were also investigated in this work. Thus, combination effects between two ionic liquid additives, a halogenated and a halogen-free one, were evaluated by a ball-on-disc-type tribometer under boundary lubrication conditions. Effective friction reduction and anti-wear properties have been demonstrated in tribological investigations when adding between 0.7 and 3.4 wt% of the halogen-free IL into base fluid composed of alkylborane–imidazole complexes. X-ray photoelectron spectroscopy analyses of the steel specimens were conducted to study the correlation between tribological properties and chemical surface composition of the boundary films formed on the rubbing surface. This work suggests potential applications for using halogen-free ILs as additives for synthetic ionic liquid lubricants. 相似文献
67.
In this study, the adsorption of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) from landfill leachate onto single-walled carbon nanotubes (SWCNTs) was investigated. Different leachate solutions were prepared by altering the pH, ionic strength, and dissolved organic carbon (DOC) in the solutions to mimic the varying water conditions that occur in leachate during the various stages of waste decomposition. The youngest and oldest leachate solutions contained varying DOC and background chemistry and were represented by leachate Type A (pH = 5.0; DOC = 2500 mg/L; conductivity = 12,500 μS/cm; [Ca2+] = 1200 mg/L; [Mg2+] = 470 mg/L) and Type E (pH = 7.5; DOC = 250 mg/L; conductivity = 3250 μS/cm; [Ca2+] = 60 mg/L; [Mg2+] = 180 mg/L). These solutions were subsequently combined in different ratios to produce intermediate solutions, labeled B-D, to replicate time-dependent changes in leachate composition. Overall, a larger fraction of EE2 was removed as compared to BPA, consistent with its higher log KOW value. The total removal of BPA and EE2 decreased in older leachate solutions, with the adsorptive capacity of SWCNTs decreasing in the order of leachate Type A > Type B > Type C > Type D > Type E. An increase in the pH from 3.5 to 11 decreased the adsorption of BPA by 22% in young leachate and by 10% in old leachate. The changes in pH did not affect the adsorption of EE2 in the young leachate, but did reduce adsorption by 32% in the old leachate. Adjusting the ionic strength using Na+ did not significantly impact adsorption, while increasing the concentration of Ca2+ resulted in a 12% increase in the adsorption of BPA and a 19% increase in the adsorption of EE2. DOC was revealed to be the most influential parameter in this study. In the presence of hydrophilic DOC, represented by glucose in this study, adsorption of the endocrine disrupting compounds (EDCs) onto the SWCNTs was not affected. In the absence of SWCNTs, hydrophobic DOC (i.e., humic acid) adsorbed 15-20% of BPA and EE2. However, when the humic acid and SWCNTs were both present, the overall adsorptive capacity of the SWCNTs was reduced. Hydrophobic (π-π electron donor-acceptor) interactions between the EDCs and the constituents in the leachate, as well as interactions between the SWCNTs and the EDCs, are proposed as potential adsorption mechanisms for BPA and EE2 onto SWCNTs. 相似文献
68.
Thines NJ Shipley LA Bassman JH Fellman JK Mattison DS Slusser JR Gao W 《Journal of chemical ecology》2007,33(5):1025-1039
Ultraviolet-B (UV-B) radiation has been increasing in temperate latitudes in recent decades and is expected to continue rising
for some time. Enhanced UV-B radiation can change plant chemistry, yet the effects of these changes on mammalian herbivores
are unknown. To examine the influence of enhanced UV-B radiation on nutrition of a specialist and generalist hindgut fermenter,
we measured nutritional and chemical constituents of three common North American range plants, big sagebrush (Artemisia tridentata), yarrow (Achillea millefolium), and bluebunch wheatgrass (Pseudoregneria spicata), and how these changes influenced in vitro dry matter digestibility and in vivo digestibility by pygmy rabbits (Brachylagus idahoensis) and eastern cottontails (Sylvilagus floridanus). Forages were irradiated for 3 mo with ambient (1×) or supplemental (1.6×) UV-B radiation representing a 15% ozone depletion
for Pullman, WA, USA. Enhanced UV-B radiation had minimal effects on the nutritional content and the tannin-binding capacity
of forages. Similarly, the terpene concentration in sagebrush and yarrow was not affected by higher UV-B irradiances. Flavonoid
compounds increased in sagebrush but decreased in yarrow. Rabbit preference and intake was not affected by treatment levels
for any forage species and no differences were found between treatments for dry matter, fiber, protein digestibility, and
apparent digestible energy. 相似文献
69.
Nicole J. Gaudette Gary J. Pickering 《Critical reviews in food science and nutrition》2013,53(5):464-481
The functional foods sector represents a significant and growing portion of the food industry, yet formulation of these products often involves the use of ingredients that elicit less than desirable oral sensations, including bitterness. Promising new functional ingredients, including polyphenolics, may be more widely and readily employed in the creation of novel functional foods if their aversive bitter taste can be significantly reduced. A number of approaches are used by the industry to improve the taste properties and thus the acceptance of conventional foods that elicit excessive bitterness. This article reviews the most commonly employed techniques, including the use of bitter-modifying additives, which may prove useful for successfully introducing new functional ingredients into this rapidly growing sector. 相似文献
70.
Bradizza Clara M.; Maisto Stephen A.; Vincent Paula C.; Stasiewicz Paul R.; Connors Gerard J.; Mercer Nicole D. 《Canadian Metallurgical Quarterly》2009,77(6):1147
Few investigators studying alcohol abuse among individuals with a severe mental illness (SMI) have examined predictors of posttreatment alcohol outcomes. In the present study, a multivariate approach based on a theoretical model was used to study the relationship between psychosocial factors and post-treatment-initiation alcohol use. Predictors of alcohol use outcomes were examined in 278 individuals diagnosed with a current schizophrenia-spectrum or bipolar disorder and an alcohol use disorder (AUD). At 6-months follow-up, 144 of 228 available participants (63%) had good clinical outcomes. The results of structural equation modeling indicated that type of pretreatment residential setting was directly related to treatment, with participants who lived in supervised settings (41%) reporting significantly more days of treatment (β = .34, p 相似文献