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21.
Derek D. Lovingood Jeffrey R. Owens Michael Seeber Konstantin G. Kornev Igor Luzinov 《Journal of visualized experiments : JoVE》2013,(82)
Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan δ solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials'' morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by Stöber''s methods, which have smooth surfaces. 相似文献
22.
Given that the effectiveness of interstitial hyperthermia for cancer treatment is related to the temperature achieved during the ablation process, there is a need for an accurate understanding of the required temperature distribution which is affected by the physical shape and form of tumours. Although a maximum peak temperature value and minimum backward heating are desired, the temperature distribution needs to be not only high but also uniformly extended over a section instead of at one peak point, especially when a roughly oval-shaped tumour is aligned with the antenna. In this case, achieving a high temperature peak destroys only the central cancerous cells after the first minutes of ablation, leaving the cells on the side alive. In this paper, a complex model was extended for the study of the heat distribution of an antenna over a porous liver composed of blood, cancerous cells, and normal tissue. Three different types of antenna were analysed: single-slot, double-slot, and dipole-tip. A novel structure made up of the single-slot antenna with a micron cut, named the micro-cut slot (MCS) antenna, was proposed and analysed. Thanks to the new structure, high uniform temperature distribution with minimum backward heating was achieved. The extended model equations, which encompass a coupled nonlinear set of transient Maxwell's electromagnetic equations, extended Darcy–Brinkman equation, and local thermal non-equilibrium equations for porous medium approximation, were solved numerically using the novel alternating direction implicit, finite–difference time–domain approach. The results showed that each type of antenna could be useful if chosen according to the shape of the tumour. In comparison with previously used antennas, the MCS antenna presented a good combination of the required goals of achieving uniform high temperature distribution and minimum backward heating. 相似文献
23.
Emily House Anthony Polwart Philippa Darbre Lester Barr George Metaxas Christopher Exley 《Journal of trace elements in medicine and biology》2013,27(4):257-266
The aetiology of breast cancer is multifactorial. While there are known genetic predispositions to the disease it is probable that environmental factors are also involved. Recent research has demonstrated a regionally specific distribution of aluminium in breast tissue mastectomies while other work has suggested mechanisms whereby breast tissue aluminium might contribute towards the aetiology of breast cancer. We have looked to develop microwave digestion combined with a new form of graphite furnace atomic absorption spectrometry as a precise, accurate and reproducible method for the measurement of aluminium in breast tissue biopsies. We have used this method to test the thesis that there is a regional distribution of aluminium across the breast in women with breast cancer. Microwave digestion of whole breast tissue samples resulted in clear homogenous digests perfectly suitable for the determination of aluminium by graphite furnace atomic absorption spectrometry. The instrument detection limit for the method was 0.48 μg/L. Method blanks were used to estimate background levels of contamination of 14.80 μg/L. The mean concentration of aluminium across all tissues was 0.39 μg Al/g tissue dry wt. There were no statistically significant regionally specific differences in the content of aluminium. We have developed a robust method for the precise and accurate measurement of aluminium in human breast tissue. There are very few such data currently available in the scientific literature and they will add substantially to our understanding of any putative role of aluminium in breast cancer. While we did not observe any statistically significant differences in aluminium content across the breast it has to be emphasised that herein we measured whole breast tissue and not defatted tissue where such a distribution was previously noted. We are very confident that the method developed herein could now be used to provide accurate and reproducible data on the aluminium content in defatted tissue and oil from such tissues and thereby contribute towards our knowledge on aluminium and any role in breast cancer. 相似文献
24.
Yu.D. Ivanov K.A. Malsagova A.A. Izotov T.O. Pleshakova V.Yu. Tatur S.G. Vesnin N.D. Ivanova S.A. Usanov A.I. Archakov 《Biochemistry and Biophysics Reports》2016
Microwave radiation at 3.4–4.2 GHz frequency of the cytochrome P450 CYP102 A1 (BM3) solution was registered during the lauric acid hydroxylation reaction. The microwave radiation generation was shown to occur following the addition of electron donor NADPH to a system containing an enzyme and a substrate. The radiation occurs for the enzyme solutions with enzyme concentrations of 10?8 and 10?9 М. The microwave radiation effect elicited by the aqueous enzyme solution was observed for the first time. The results obtained can be used to elaborate a new approach to enzyme systems research, including studying of the mechanism of interaction of a functioning enzyme system with microenvironment. 相似文献
25.
《Bioorganic & medicinal chemistry》2016,24(18):4452-4463
A facile and robust microwave-assisted solution phase parallel synthesis protocol was exercised for the development of a 38-member library of N,N′-disubstituted thiourea analogues (1–38) by using an identical set of conditions. The reaction time for synthesis of N,N′-disubstituted thiourea analogues was drastically reduced from a reported duration of 8–12 h for conventional methods to only 1.5–2.0 min. All the derivatives (1–38) were characterized by physico-analytical techniques such as elemental analysis in combination with FT-IR, 1H, 13C NMR and by single crystal XRD analysis have also been performed. These compounds were screened for their in vitro urease inhibition activities. Majority of compounds exhibited potent urease inhibition activities, however, the most significant activity was found for 16, with an IC50 value of 1.23 ± 0.1 μM. Furthermore, the synthesized compounds were screened for their cytotoxic potential against lungs cancer cell lines. Cell culture studies demonstrated significant toxicity of the compounds on the cell lines, and the levels of toxicity were altered in the presence of various side groups. The molecular docking studies of the most potent inhibitors were performed to identify the probable binding modes in the active site of the urease enzymes. These compounds have a great potential and significance for further investigations. 相似文献
26.
《Bioorganic & medicinal chemistry》2016,24(21):5103-5114
A series of bisbenzimidazole derivatives starting from o-phenylenediamine and 4-nitro-o-phenylenediamine were prepared with oxalic acid. Most of the reactions were conducted using both the microwave and conventional methods to compare yields and reaction times. The operational simplicity, environmental friendly conditions and high yield in a significantly short reaction time were the major benefits. All substances’ inhibitory activities against α-glucosidase were evaluated. The results may suggest a significant role for the nature of bisbenzimidazole compounds in their inhibitory action against α-glucosidase. They showed different range of α-glucosidase inhibitory potential with IC50 value ranging between 0.44 ± 0.04 and 6.69 ± 0.01 μM when compared to the standard acarbose (IC50, 13.34 ± 1.26 μM). This has described a new class of α-glucosidase inhibitors. Molecular docking studies were done for all compounds to identify important binding modes responsible for inhibition activity of α-glucosidase. 相似文献
27.
微波辐射法合成苄基-2-萘基醚的研究 总被引:1,自引:0,他引:1
在微波辐射条件下,以2-萘酚和氯化苄为原料,用氢氧化钠作碱剂,碘化钾作催化剂,以水和N,N-二甲基甲酰胺(DMF)为溶剂合成了苄基-2-萘基醚;采用单因素实验法,考察了反应物的摩尔比、催化剂用量、微波功率、辐射时间等因素对苄基-2-萘基醚产率的影响。实验结果表明:在n(2-萘酚):n(氢氧化钠):n(氯化苄):n(碘化钾)=1:1.1:1:0.018,水7 ml,DMF 25 ml,微波功率320 W和辐射时间75 s的优化条件下,苄基-2-萘基醚的产率可达88.03%。 相似文献
28.
Maggi L Catellani PL Fisicaro E Santi P Zani F Massimo G Colombo P 《AAPS PharmSciTech》2000,1(3):94-101
The aim of this work was to find a drying procedure for moist sucralfate gel capable of producing dried sucralfate gel that
retains the original gel properties of bioadhesion, rheology, and micromeritics. Spray-drying and microwave-drying procedures
were employed. Mannitol was used as a gel-protective substance during the drying processes. The spray drying of moist sucralfate
gel gave rise to a powder whose water suspensions showed significantly reduced viscosity. The bioadhesion of spray-dried sucralfate
gel was strongly reduced by drying. When mannitol was used as a gel protector, the spray-dried sucralfate in part maintained
the original bioadhesion of moist sucralfate gel. The preparation of a dried sucralfate gel retaining the bioadhesion characteristics,
avoiding the use of mannitol, was made possible using the microwavedrying procedure. The microwave-dried product possesses
a granular morphology suitable for direct compression because it is a free flowing and strongly coherent granular powder. 相似文献
29.
Microwave oven and boiling waterbath extraction of hepatotoxins from cyanobacterial cells 总被引:11,自引:0,他引:11
Low-cost, straightforward methods for the extraction of microcystins and nodularins from cyanobacterial cells were developed using a microwave oven and boiling waterbath. The use of organic solvents, such as methanol, which can interfere with sensitive analytical procedures, e.g. immunoassays, can thus be avoided. Analysis by protein phosphatase inhibition assay and high performance liquid chromatography indicated that purified microcystin-LR was unaffected by the microwave oven and boiling waterbath treatments. Four microcystins of differing hydrophobicities were successfully extracted from Microcystis PCC 7813 by both treatments at yields equivalent to those obtained by longer protocols using methanol. Assessment of the microwave oven and boiling waterbath extraction methods with laboratory strains and environmental samples of cyanobacteria showed good correlation with results from lyophilisation and methanol extraction, when extracts were analysed by high performance liquid chromatography with diode array detection (R(2)>/=0.92). The microwave and boiling waterbath extraction methods also sterilised the environmental bloom samples, as evidenced by the abolition of heterotrophic bacterial growth. 相似文献
30.
In this study, the microwave rewarming process of cryopreserved samples with embedded superparamagnetic (SPM) nanoparticles was numerically simulated. The Finite Element Method (FEM) was used to calculate the coupling of the electromagnetic field and the temperature field in a microwave rewarming system composed of a cylindrical resonant cavity, an antenna source, and a frozen sample phantom with temperature-dependent properties. The heat generated by the sample and the nanoparticles inside the electromagnetic field of the microwave cavity was calculated. The dielectric properties of the biological tissues were approximated using the Debye model, which is applicable at different temperatures. The numerical results showed that, during the rewarming process of the sample phantom without nanoparticles, the rewarming rate was 29.45 °C/min and the maximum temperature gradient in the sample was 3.58 °C/mm. If nanoparticles were embedded in the sample, and the cavity power was unchanged, the rewarming rate was 47.76 °C/min and the maximum temperature gradient in the sample was 1.64 °C/mm. In the presence of SPM nanoparticles, the rewarming rate and the maximum temperature gradient were able to reach 20.73 °C/min and 0.68 °C/mm at the end of the rewarming under the optimized cavity power setting, respectively. The ability to change these temperature behaviors may prevent devitrification and would greatly diminish thermal stress during the rewarming process. The results indicate that the rewarming rate and the uniformity of temperature distribution are increased by nanoparticles. This could be because nanoparticles generated heat in the sample homogeneously and the time-dependent parameters of the sample improved after nanoparticles were homogeneously embedded within it. We were thus able to estimate the positive effect of SPM nanoparticles on microwave rewarming of cryopreserved samples. 相似文献