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排序方式: 共有1168条查询结果,搜索用时 15 毫秒
1.
Bacteria-associated infections have increased in recent years due to treatment resistance developed by these microorganisms. Due to the high antibacterial capacity associated with their nanometric size, nanoparticles, such as zinc oxide (ZnO), have proven to be an alternative for general medical procedures. One of the methodologies to synthesize them is green synthesis, where the most commonly used resources are plant species. Using Dysphania ambrosioides extract at various synthesis temperatures (200, 400, 600, and 800 °C), zinc oxide nanoparticles (ZnO-NPs) with average sizes ranging from 7 to 130 nm, quasi-spherical shapes, and hexagonal prism shapes were synthesized. Larger sizes were obtained by increasing the synthesis temperature. The ZnO crystalline phase was confirmed by X-ray diffraction and transmission electron microscopy. The sizes and shapes were observed by field emission scanning electron microscopy. The Zn-O bond vibration was identified by Fourier transform infrared spectroscopy. Thermogravimetry showed the stability of ZnO-NPs. The antibacterial evaluations, disk diffusion test, and minimum bactericidal concentration, demonstrated the influence of particle size. The smaller the nanoparticle size, the higher the inhibition for all pathogenic strains: Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, and dental pathogens: Streptococcus mutans, Streptococcus sanguinis, Porphyromonas gingivalis, and Prevotella intermedia. The molecular docking study showed a favorable interaction between ZnO-NPs and some proteins in Gram-positive and Gram-negative bacteria, such as TagF in Staphylococcus epidermidis and AcrAB-TolC in Escherichia coli, which led to proposing them as possible targets of nanoparticles.  相似文献   
2.
In the present study, a novel polysaccharide from Flammulina velutipes scraps (FVSP) was extracted and purified from Flammulina velutipes scraps. FVSP was chemically chelated to synthesize FVSP-iron (III) complex. Based on single factor experiments, preparation process of FVSP- iron (III) was optimized by response surface methodology. The characterization and antioxidant activity of FVSP-iron (III) were investigated. The results showed that the optimal preparation process of FVSP-iron (III) was reaction temperature of 50 °C, reaction time of 4.7 h and the mass ratio of FVSP/sodium citrate - of 2:1. The relative molecular weight of FVSP-iron (III) was 36.25 kDa. FVSP-Iron (III) was composed of glucose, galactose, mannose and xylose in a molar ratio of 65.1:20.5:5.2:9.2.The results of UV–vis absorption spectrum, FI-IR spectrum and X-ray diffraction showed that both hydroxyl and carboxyl groups in FVSP participated in the coordination reaction and the iron core of FVSP-Iron(III) was a polymerized β-FeOOH structure. FVSP-iron (III) had better thermal stability and stronger antioxidant activities than FVSP. The results indicated that FVSP-iron (III) could be potentially used in food industry as a new food additive and iron supplement.  相似文献   
3.
Nanotechnology deals with the materials at nanoscale to synthesize nanoparticles. The current study introduced a new green approach for the synthesis of Copper and Nickel hybrid nanoparticles by using Zingiber officinale rhizome extract as a capping and reducing agent. The nanoparticles were physico-chemically characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, Energy-dispersive X-ray spectroscopy, and Scanning electron microscopy. It was revealed by scanning electron micrograph that the Cu-Ni hybrid nanoparticles have spherical geometries with average grain size of 25.12 ± 1.2 nm. Furthermore, biocatalytic and photocatalytic applications of the biosynthesized nanoparticles were assessed. The results of antibacterial assay revealed that Cu-Ni hybrid nanoparticles had an inhibition zones of 28 ± 1.0, 25 ± 0.8, and 25 ± 1.5 mm against P. aeruginosa, E. coli and Proteus vulgaris. Commercially available antibiotics were purchased and coated with Cu-Ni hybrid nanoparticles, it was found that their antimicrobial efficacy was increased twice. To evaluate the antioxidant potential, nanoparticles having a concentration of 200 µg/mL were applied against 2,2-diphenyl-1-picrylhydrazyl free radicals and NPs showed 42.1 ± 0.71 % inhibition. Cu-Ni nanoparticles have shown a dose-dependent cytotoxicity against amastigote and promastigote in anti-leishmanial assay. The synthesized nanoparticles were found biocompatible and safe in nature to be used in vivo, as they showed no significant hemolysis of human red blood cells at their highest concentration. In antidiabetic assay, NPs inhibited alpha-amylase enzyme up to 38.07 ± 0.65 %. An organic crystal violet dye was successfully degraded by the synthesized nanoparticles in photocatalytic assay. Hence, it is concluded that Cu-Ni hybrid nanoparticles can be used both in vitro and in vivo for drug delivery in biomedical research. These nanoparticles can also be used in the remediation of organic dyes as a catalyst.  相似文献   
4.
The present study investigates the synthesis and effectiveness of gold/gelatin nanoparticles (NPs) biopolymer as a carrier for methotrexate (MTX) drug. Two different shapes of gold particles, including spherical AuNPs (50 & 100 nm) and gold nanorods (AuNRs) with three different sizes (20, 50 and 100 nm length) were synthesized using the chemical reduction method. The effect of AuNPs size and shape on the entrapment efficiency (E.E), the release rate of the drug, and cellular uptake were investigated. The surfaces of both AuNPs and AuNRs were coated with a gelatin biopolymer, and the stability and property of the generated compounds were studied. Moreover, MTX as a chemotherapeutic agent was loaded on the gelatin-coated AuNPs/AuNRs complexes. The physicochemical properties of the gelatin-coated AuNPs/AuNRs complexes were studied using ultraviolet-visible (UV–Vis) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The E.E and MTX release behavior from the complexes at pH values of 7.4 and 5.4 and temperatures of 37 and 40 °C were investigated in vitro. The cytotoxic effects of AuNPs, AuNPs-Gelatin, AuNPs-Gelatin-MTX, AuNRs, AuNRs-Gelatin, AuNRs-Gelatin-MTX and free MTX were studied. The results indicated that the E.E of AuNPs was higher than that of AuNRs. The highest release rate of the drug was related to the AuNR1-gelatin complex (pH 5.4 and temperature of 40 °C). In addition, MTX loaded AuNR2-gelatin showed the highest cytotoxic effect on the MCF-7 breast cancer cell line so that even its cell cytotoxicity was more than that of the free drug.  相似文献   
5.
王莉莉  朱平  董侠  王笃金 《高分子学报》2020,(1):1-11,I0001
长碳链聚酰胺(LCPA)作为聚酰胺的特殊品种,较长的亚甲基链和极性酰胺基团使其兼具聚烯烃和聚酰胺的双重特性.在加工或使用过程中,拉伸诱导结晶现象对长碳链聚酰胺及其共聚物的强度和弹性行为具有重要影响,深入认识其在外场下的微观结构响应对该材料的设计及制备具有重要意义.围绕拉伸诱导结晶作用,该专论主要基于本团队2010年以来在长碳链聚酰胺及其共聚物的拉伸诱导结晶工作,并综述了国内外的相关研究,涉及拉伸诱导结晶现象、拉伸诱导结晶的影响因素、拉伸诱导结晶与力学性能的构效关系及拉伸诱导结晶的表征方法等方面.  相似文献   
6.
This work aims to determine the tensile set behavior of a silicone rubber under different stress magnitudes and temperatures through digital image correlation implemented in an improved creep experimental set-up. Creep-recovery strains were measured with time at 20, 40 and 60 °C under tensile strengths of 98.1, 196.2 and 394.3 kPa, respectively. The behavior of creep and recovery strain with time at the different stress magnitudes and temperatures was successfully obtained by the experiments. The corresponding elastic and viscous components of the material for each condition were determined from the results. Overall, all obtained creep behaviors matched with the behavior of a four-element model of creep-recovery. The increase of temperature generated an increase of creep compliance at the three loads, but the increase of tensile load produced a decrease of creep compliance for the three temperatures. The strain was not recovered entirely in any case for the test time stated.  相似文献   
7.
Instrumental techniques such as Fourier Transform Infrared Spectroscopy (FT-IR) constitute well-studied methodologies for polymer characterization, including polymeric fibers. However, a relatively short number of scientific publications involve the characterization of commercial Poly [(4-hydroxybenzoic)-ran-(2-hydroxy-6-naphthoic acid)] (Vectran™) fiber and its surface species. The majority of the published infrared studies uses the medium infrared region (MIR) associated to the Attenuated total reflection (ATR) method. In this scenario, this short review addresses the characteristics of Vectran™ fiber, sample depth data of each FT-IR spectrum mode, reflection and photo-acoustic spectroscopy (PAS), including near infrared (NIR) analysis. This paper addresses also researches on the characterization of Vectran™ by several FT-IR analysis conditions aiming to contribute to future studies. This brief review deals with methodologies developed in the last decade and published by several scientific research groups, emphasizing studies conducted in the last five years. A critical assessment and trends are also included.  相似文献   
8.
Vanadate and vanadium compounds exist in many environmental, biological and clinical matrices, and despite the need only limited progress has been made on the analysis of vanadium compounds. The vanadium coordination chemistry of different oxidation states is known, and the result of the characterization and speciation analysis depends on the subsequent chemistry and the methods of analysis. Many studies have used a range of methods for the characterization and determination of metal ions in a variety of materials. One successful technique is high performance liquid chromatography (HPLC) that has been used mainly for measuring total vanadium level and metal speciation. Some cases have been reported where complexes of different oxidation states of vanadium have been separated by HPLC. Specifically reversed phase (RP) HPLC has frequently been used for the measurement of vanadium. Other HPLC methods such as normal phase, anion-exchange, cation-exchange, size exclusion and other RP-HPLC modes such as, ion-pair and micellar have been used to separate selected vanadium compounds. We will present a review that summarizes and critically analyzes the reported methods for analysis of vanadium salts and vanadium compounds in different sample matrices. We will compare various HPLC methods and modes including sample preparation, chelating reagents, mobile phase and detection methods. The comparison will allow us to identify the best analytical HPLC method and mode for measuring vanadium levels and what information such methods provide with regard to speciation and quantitation of the vanadium compounds.  相似文献   
9.
The treatment of chronic wounds represents a major interest for public health both medically and economically. Hence the need for a modern wound dressing that actively promotes the physiological process specific to healing. In this perspective we have studied the development of a new dressing able to offer a serious contribution to the dilemma of the various chronic wounds. A dressing grafted with two natural polysaccharides known for their multiple biological effects, chitosan and a carbohydrate polymer extracted from Commiphora myrrha (CMP). We began by studying the grafting of the two natural biopolymers onto cellulose dressings, via a polyacrylic acid as a crosslinking agent. An optimization study, revealed the different grafting parameters, the polymer concentration as well as the heat-setting time and temperature. After, different characterization techniques were carried out in order to evaluate the effectiveness of our grafting. The swelling test revealed a hydrophilicity enhancement which increased with the degree of grafting, a desired property for effective dressings. Infrared characterization as well as thermogravimetric analysis (TGA and DTA) confirmed the binding mode and the permanence of our grafting. XRD and mechanical characterization showed no change in the crystallinity or in the original mechanical properties of the functionalized dressings. Morphological SEM study, confirmed the presence of our grafting as well as its mode of distribution. Finally, a bacteriological study conducted, showed a clear improvement of the antimicrobial behavior of cellulosic wound dressings functionalized by our combined natural biopolymers.  相似文献   
10.
Graphene oxide (GO) has become the focus of scientific research due to unique mechanical, optical, electrical and chemical properties. We review the synthesis approaches and formation mechanism of GO, and propose that the crucial factor to the preparation of GO is to find efficient and environmentally friendly oxidant. Various characterization techniques are introduced, and characteristics are summarized. The GO model theories are synopsized, and determining the structure of GO has important influence on its surface modification and its application and development in composite materials. The interaction and reaction types between GO matrix and modified molecules, as well as the properties of modified products were described. In conclusion, the present challenges and future research directions are presented in terms of preparation and surface functional modification for GO.  相似文献   
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