Heterogeneous Gold‐Catalyzed Selective Reductive Transformation of Quinolines with Formic Acid

Single phase rutile titania supported gold nanoparticles (Au/TiO₂‐R) are found to be efficient and versatile catalysts for chemo‐ and regioselective transfer hydrogenation of quinoline derivatives to 1,2,3,4‐tetrahydroquinolines (THQs) using formic acid (FA) as a safe and convenient hydrogen source under mild conditions. The activity and chemoselectivity of the Au/TiO₂‐R catalyst towards THQs is excellent, with a substrate to catalyst ratio (S/C) of 1000 being feasible. Furthermore, a straightforward and selective route to N‐formyltetrahydroquinolines (FTHQ) directly from quinoline compounds and FA by one‐pot, gold‐catalyzed reductive N‐formylation protocol is also established.

     

聚合物-纳米无机粒子复合微球研究新进展

近年来,聚合物-纳米无机粒子复合微球相关的设计、制备、以及应用研究得到了科学界众多学者的广泛关注与探索。本文论述了单体聚合法制备聚合物-纳米无机粒子复合微球的研究近况,主要介绍了悬浮聚合、乳液聚合(微乳液聚合、Pickering乳液聚合、细乳液聚合、反相乳液聚合、无皂乳液聚合)、分散聚合及溶液聚合的制备方法。概述了聚合物-纳米无机粒子复合微球在生物医药、光电材料、保护涂层、催化等方面的应用,展望了聚合物-纳米无机粒子复合微球的发展趋势。     

Methanobactin-Mediated Synthesis of Gold Nanoparticles Supported over Al2O3 toward an Efficient Catalyst for Glucose Oxidation

Methanobactin (Mb) is a copper-binding peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and reduce Au(III) to Au(0). In this paper, Au/Al₂O₃ catalysts prepared by a novel incipient wetness-Mb-mediated bioreduction method were used for glucose oxidation. The catalysts were characterized, and the analysis revealed that very small gold nanoparticles with a particle size <4 nm were prepared by the incipient wetness-Mb-mediated bioreduction method, even at 1.0% Au loading (w/w). The influence of Au loading, calcination temperature and calcination time on the specific activity of Au/Al₂O₃ catalysts was systematically investigated. Experimental results showed that decomposing the Mb molecules properly by calcinations can enhance the specific activity of Au/Al₂O₃ catalysts, though they acted as reductant and protective agents during the catalyst preparation. Au/Al₂O₃ catalysts synthesized by the method exhibited optimum specific activity under operational synthesis conditions of Au loading of 1.0 wt % and calcined at 450 °C for 2 h. The catalysts were reused eight times, without a significant decrease in specific activity. To our knowledge, this is the first attempt at the preparation of Au/Al₂O₃ catalysts by Mb-mediated in situ synthesis of gold nanoparticles.     

Nanoparticle-Mediated Pulmonary Drug Delivery: A Review

Colloidal drug delivery systems have been extensively investigated as drug carriers for the application of different drugs via different routes of administration. Systems, such as solid lipid nanoparticles, polymeric nanoparticles and liposomes, have been investigated for a long time for the treatment of various lung diseases. The pulmonary route, owing to a noninvasive method of drug administration, for both local and systemic delivery of an active pharmaceutical ingredient (API) forms an ideal environment for APIs acting on pulmonary diseases and disorders. Additionally, this route offers many advantages, such as a high surface area with rapid absorption due to high vascularization and circumvention of the first pass effect. Aerosolization or inhalation of colloidal systems is currently being extensively studied and has huge potential for targeted drug delivery in the treatment of various diseases. Furthermore, the surfactant-associated proteins present at the interface enhance the effect of these formulations by decreasing the surface tension and allowing the maximum effect. The most challenging part of developing a colloidal system for nebulization is to maintain the critical physicochemical parameters for successful inhalation. The following review focuses on the current status of different colloidal systems available for the treatment of various lung disorders along with their characterization. Additionally, different in vitro, ex vivo and in vivo cell models developed for the testing of these systems with studies involving cell culture analysis are also discussed.     

Biocompatible PEGylated Fe3O4 Nanoparticles as Photothermal Agents for Near-Infrared Light Modulated Cancer Therapy

In accordance with the World Cancer Report, cancer has become the leading cause of mortality worldwide, and various therapeutic strategies have been developed at the same time. In the present study, biocompatible magnetic nanoparticles were designed and synthesized as high-performance photothermal agents for near-infrared light mediated cancer therapy in vitro. Via a facile one-pot solvothermal method, well-defined PEGylated magnetic nanoparticles (PEG–Fe₃O₄) were prepared with cheap inhesion as a first step. Due to the successful coating of PEG molecules on the surface of PEG–Fe₃O₄, these nanoparticles exhibited excellent dispersibility and dissolvability in physiological condition. Cytotoxicity based on MTT assays indicated these nanoparticles revealed high biocompatibility and low toxicity towards both Hela cells and C6 cells. After near-infrared (NIR) laser irradiation, the viabilities of C6 cells were effectively suppressed when incubated with the NIR laser activated PEG–Fe₃O₄. In addition, detailed photothermal anti-cancer efficacy was evaluated via visual microscope images, demonstrating that our PEG–Fe₃O₄ were promising for photothermal therapy of cancer cells.     

PVP作为保护剂制备Ag纳米粒子

以聚乙烯吡咯烷酮(PVP)为分散剂和保护剂,分别用乙醇和高分子化合物聚乙烯醇(PVA)作还原剂制备银纳米粒子,通过控制反应时间、PVP和PVA的含量及硝酸银的浓度,在90℃回流条件下得到纳米银颗粒。采用红外光谱对聚合物结构进行表征,紫外-可见光谱表征反应物浓度对制备银纳米粒子尺寸分布的影响,扫描电镜观察纳米粒子和聚合物网络形貌,X射线衍射分析银纳米粒子的晶体结构。     

Tailoring acidity of HZSM-5 nanoparticles for methyl bromide dehydrobromination by Al and Mg incorporation

Three kinds of HZSM-5 nanoparticles with different acidity were tailored by impregnating MgO or varying Si/Al ratios. Both the textural and acidic properties of the as-prepared nanoparticles were characterized by nitrogen adsorption-desorption measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature-programmed desorption (NH₃-TPD) and Fourier transform infrared spectroscopy (FTIR or Py-FTIR). It was found that the intensity of Lewis acid sites with weak strength was enhanced by impregnating MgO or reducing Al concentration, and such an enhancement could be explained by the formation of Mg(OH)⁺ or charge unbalance of the MgO framework on the surface of HZSM-5 support. The effect of HZSM-5 nanoparticles'' acidity on methyl bromide dehydrobromination as catalyst was evaluated. As the results, MgHZ-360 catalyst with the highest concentration of Lewis acid sites showed excellent stability, which maintained methyl bromide conversion of up 97% in a period of 400 h on stream. Coke characterization by BET measurements and TGA/DTA and GC/MS analysis revealed that polymethylated naphthalenes species were formed outside the channels of the catalyst with higher acid intensity and higher Brønsted acid concentration during the initial period of reaction, while graphitic carbon formed in the channels of catalyst with lower acid intensity and higher Lewis acid concentration during the stable stage.     

Oxidative stress mediated cytotoxicity of biologically synthesized silver nanoparticles in human lung epithelial adenocarcinoma cell line

The goal of the present study was to investigate the toxicity of biologically prepared small size of silver nanoparticles in human lung epithelial adenocarcinoma cells A549. Herein, we describe a facile method for the synthesis of silver nanoparticles by treating the supernatant from a culture of Escherichia coli with silver nitrate. The formation of silver nanoparticles was characterized using various analytical techniques. The results from UV-visible (UV-vis) spectroscopy and X-ray diffraction analysis show a characteristic strong resonance centered at 420 nm and a single crystalline nature, respectively. Fourier transform infrared spectroscopy confirmed the possible bio-molecules responsible for the reduction of silver from silver nitrate into nanoparticles. The particle size analyzer and transmission electron microscopy results suggest that silver nanoparticles are spherical in shape with an average diameter of 15 nm. The results derived from in vitro studies showed a concentration-dependent decrease in cell viability when A549 cells were exposed to silver nanoparticles. This decrease in cell viability corresponded to increased leakage of lactate dehydrogenase (LDH), increased intracellular reactive oxygen species generation (ROS), and decreased mitochondrial transmembrane potential (MTP). Furthermore, uptake and intracellular localization of silver nanoparticles were observed and were accompanied by accumulation of autophagosomes and autolysosomes in A549 cells. The results indicate that silver nanoparticles play a significant role in apoptosis. Interestingly, biologically synthesized silver nanoparticles showed more potent cytotoxicity at the concentrations tested compared to that shown by chemically synthesized silver nanoparticles. Therefore, our results demonstrated that human lung epithelial A549 cells could provide a valuable model to assess the cytotoxicity of silver nanoparticles.     

Quantifying spectral changes experienced by plasmonic nanoparticles in a cellular environment to inform biomedical nanoparticle design

Metal nanoparticles (NPs) scatter and absorb light in precise, designable ways, making them agile candidates for a variety of biomedical applications. When NPs are introduced to a physiological environment and interact with cells, their physicochemical properties can change as proteins adsorb on their surface and they agglomerate within intracellular endosomal vesicles. Since the plasmonic properties of metal NPs are dependent on their geometry and local environment, these physicochemical changes may alter the NPs'' plasmonic properties, on which applications such as plasmonic photothermal therapy and photonic gene circuits are based. Here we systematically study and quantify how metal NPs'' optical spectra change upon introduction to a cellular environment in which NPs agglomerate within endosomal vesicles. Using darkfield hyperspectral imaging, we measure changes in the peak wavelength, broadening, and distribution of 100-nm spherical gold NPs'' optical spectra following introduction to human breast adenocarcinoma Sk-Br-3 cells as a function of NP exposure dose and time. On a cellular level, spectra shift up to 78.6 ± 23.5 nm after 24 h of NP exposure. Importantly, spectra broaden with time, achieving a spectral width of 105.9 ± 11.7 nm at 95% of the spectrum''s maximum intensity after 24 h. On an individual intracellular NP cluster (NPC) level, spectra also show significant shifting, broadening, and heterogeneity after 24 h. Cellular transmission electron microscopy (TEM) and electromagnetic simulations of NPCs support the trends in spectral changes we measured. These quantitative data can help guide the design of metal NPs introduced to cellular environments in plasmonic NP-mediated biomedical technologies.