水溶性CdTe量子点的制备和表面修饰及表征

近年来,半导体纳米晶CdTe引起人们越来越多的关注。它具有吸收光谱宽,发射光谱窄而对称,发光颜色可调,荧光强度和光稳定性高等特点,已经广泛用于生物标记,生物传感及生物检测领域。尤其在基于荧光共振能量转移原理的生物传感领域,量子点有望取代有机荧光发色基团作为能量供体。在文章实验中,以巯基丙酸(MPA)作为稳定剂,在水相中合成了CdTe量子点,并考察了回流时间,反应温度,溶液pH对CdTe光学性质的影响。利用透射电子显微镜(TEM),荧光分光光度计(FS)等手段对产物进行分析和表征。结果表明:在pH为9.1,反应温度为30℃,回流5 h,可以实现CdTe的优化合成。在紫外灯(254 nm)照射下,回流时间从1 h到7 h所得到的CdTe量子点,颜色由绿色变到黄色,对应的荧光光谱图的吸收峰位从515 nm(回流1 h)红移到573 nm(回流7 h),证实了CdTe量子点的尺寸随着回流时间的增长而增加。由TEM结果,所合成的CdTe量子点分散性好,且粒径大约在5 nm左右。该本实验制备的CdTe量子点具有较高的荧光强度和量子效率,将在生物标记,生物传感,生物成像等领域有重要作用。     

量子点的合成研究

量子点（半导体纳米晶）是纳米尺度的微小发光粒子。作为新型的生物标记试剂,具有比传统的有机染料更好的光谱特性和光学稳定性。本文对量子点的光学性质、制备方法做一简要综述。     

Effects of Rhizosphere Bacteria on Strawberry Plants (Fragaria × ananassa Duch.) under Water Deficit

Due to the observed climate warming, water deficiency in soil is currently one of the most important stressors limiting the size and quality of plant crops. Drought stress causes a number of morphological, physiological, and biochemical changes in plants, limiting their growth, development, and yield. Innovative methods of inducing resistance and protecting plants against stressors include the inoculation of crops with beneficial microorganisms isolated from the rhizosphere of the plant species to which they are to be applied. The aim of the present study was to evaluate 12 different strains of rhizosphere bacteria of the genera Pantoea, Bacillus, Azotobacter, and Pseudomonas by using them to inoculate strawberry plants and assessing their impact on mitigating the negative effects of drought stress. Bacterial populations were assessed by estimates of their size based on bacterial counts in the growth substrate and with bioassays for plant growth-promoting traits. The physiological condition of strawberry plants was determined based on the parameters of chlorophyll fluorescence. The usefulness of the test methods used to assess the influence of plant inoculation with rhizosphere bacteria on the response of plants growing under water deficit was also evaluated. A two-factor experiment was performed in a complete randomization design. The first experimental factor was the inoculation of plant roots with rhizosphere bacteria. The second experimental factor was the different moisture content of the growth substrate. The water potential was maintained at −10 to −15 kPa under control conditions, and at −40 to −45 kPa under the conditions of water deficit in the substrate. The tests on strawberry plants showed that the highest sensitivity to water deficiency, and thus the greatest usefulness for characterizing water stress, was demonstrated by the following indices of chlorophyll “a” fluorescence: F_M, F_V, F_V/F_M, PI, and Area. Based on the assessment of the condition of the photosynthetic apparatus and the analysis of chlorophyll “a” fluorescence indices, including hierarchical cluster analysis, the following strains of rhizosphere bacteria were found to have favorable effects on strawberry plants under water deficit: the Bacillus sp. strains DLGB2 and DKB26 and the Pantoea sp. strains DKB63, DKB70, DKB68, DKB64, and DKB65. In the tests, these strains of Bacillus sp. exhibited a common trait—the ability to produce siderophores, while those of Pantoea sp. were notable for phosphate mobilization and ACCD activity.     

量子点的应用及研究进展

量子点因具有宽的激发光谱、窄的发射光谱、高的荧光量子产率和寿命长等特殊的性质,是一种比荧光染料分子更理想的生物探针。详细介绍了国内外的几种量子点制备方法及其表面修饰,另外综述了量子点在生物学的应用。     

“Turn on” Fluorescence Sensor of Glutathione Based on Inner Filter Effect of Co-Doped Carbon Dot/Gold Nanoparticle Composites

Glutathione (GSH) is a thiol that plays a significant role in nutrient metabolism, antioxidant defense and the regulation of cellular events. GSH deficiency is related to variety of diseases, so it is useful to develop novel approaches for GSH evaluation and detection. In this study we used nitrogen and phosphorus co-doped carbon dot-gold nanoparticle (NPCD–AuNP) composites to fabricate a simple and selective fluorescence sensor for GSH detection. We employed the reductant potential of the nitrogen and phosphorus co-doped carbon dots (NPCDs) themselves to form AuNPs, and subsequently NPCD–AuNP composites from Au³⁺. The composites were characterized by using a range of spectroscopic and electron microscopic techniques, including electrophoretic light scattering and X-ray diffraction. The overlap of the fluorescence emission spectrum of NPCDs and the absorption spectrum of AuNPs resulted in an effective inner filter effect (IFE) in the composite material, leading to a quenching of the fluorescence intensity. In the presence of GSH, the fluorescence intensity of the composite was recovered, which increased proportionally to increasing the GSH concentration. In addition, our GSH sensing method showed good selectivity and sensing potential in human serum with a limit of detection of 0.1 µM and acceptable results.     

石墨烯量子点在生物传感和成像技术中的应用

石墨烯量子点具有许多吸引人的优点,如低细胞毒性、溶解能力强、稳定的光致发光、良好的生物相容性、高比表面积、电子高迁移率和可调节带隙等,因此,适用于构建传感系统和生物成像。根据近几年来,基于石墨烯量子点性质构建的光学生物传感器和电化学生物传感器以及石墨烯量子点在生物成像技术中的应用进行了综述。     

非晶碳化硅量子点的制备及其光学性质研究

采用脉冲激光烧蚀法,以多晶3C-SiC陶瓷片为靶材,制备了悬浮于去离子水中的非晶SiC纳米颗粒.利用透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、傅里叶变换红外吸收光谱(FTIR)、紫外可见吸收光谱(UV-Vis)和光致发光谱(PL)等测试手段对其形貌、结构和光学性质进行了分析.结果表明:这些纳米颗粒由大量的非晶SiC构成,粒径在8～9 nm,光学带隙为3.28 eV;样品表现出较强的光致发光,发光峰位于415 nm处,这主要是由于量子限制效应造成的.     

碳量子点的制备及其在发光二极管中的应用

碳量子点是纳米材料领域一个备受关注的荧光纳米材料,仅近几年里,基于碳量子点的研究,在制备和应用方面均取得了许多突破性的进展。本文简述了碳量子点的优异特性及其合成方法,重点概述了碳量子点的修饰、复合材料的制备以及在发光二极管(LED)应用方面的最新研究进展。以期为碳量子点的发展应用提供思路和参考。     

N-Heterocycles Scaffolds as Quorum Sensing Inhibitors. Design,Synthesis, Biological and Docking Studies

Quorum sensing is a communication system among bacteria to sense the proper time to express their virulence factors. Quorum sensing inhibition is a therapeutic strategy to block bacterial mechanisms of virulence. The aim of this study was to synthesize and evaluate new bioisosteres of N-acyl homoserine lactones as Quorum sensing inhibitors in Chromobacterium violaceum CV026 by quantifying the specific production of violacein. Five series of compounds with different heterocyclic scaffolds were synthesized in good yields: thiazoles, 16a–c, thiazolines 17a–c, benzimidazoles 18a–c, pyridines 19a–c and imidazolines 32a–c. All 15 compounds showed activity as Quorum sensing inhibitors except 16a. Compounds 16b, 17a–c, 18a, 18c, 19c and 32b exhibited activity at concentrations of 10 µM and 100 µM, highlighting the activity of benzimidazole 18a (IC₅₀ = 36.67 µM) and 32b (IC₅₀ = 85.03 µM). Pyridine 19c displayed the best quorum sensing inhibition activity (IC₅₀ = 9.66 µM). Molecular docking simulations were conducted for all test compounds on the Chromobacterium violaceum CviR protein to gain insight into the process of quorum sensing inhibition. The in-silico data reveal that all 15 the compounds have higher affinity for the protein than the native AHL ligand (1). A strong correlation was found between the theoretical and experimental results.     

CdTe/CdS量子点对木犀草素与人血清白蛋白结合力的影响

用还原型谷胱甘肽(GSH)作硫源和稳定剂在水相中合成了生物相容性好、量子产率高的核壳型CdTe/CdS半导体量子点;同时模拟人体内生理环境,研究了CdTe/CdS量子点(QDs)对木犀草素与人血清白蛋白(HSA)相互作用的影响。结果表明,CdTe/CdS QDs可有规律地猝灭HSA荧光;在CdTe/CdS QDs存在条件下,木犀草素可使HSA荧光最大发射波长从341 nm红移到347 nm,红移程度明显大于无QDs存在时,同时木犀草素与HSA的表观结合常数和结合位点数均有增加,即CdTe/CdS QDs使木犀草素与HSA的结合力增强。     

Bioactive Constituents from “Triguero” Asparagus Improve the Plasma Lipid Profile and Liver Antioxidant Status in Hypercholesterolemic Rats

We have previously shown that the Andalusian-cultivated Asparagus officinalis L. “triguero” variety produces hypocholesterolemic and hepatoprotective effects on rats. This asparagus is a rich source of phytochemicals although we hypothesized there would be some of them more involved in these functional properties. Thus, we aimed to study the effects of asparagus (500 mg/kg body weight (bw)/day) and their partially purified fractions in flavonoids (50 mg/kg bw/day), saponins (5 mg/kg bw/day) and dietary fiber (500 mg/kg bw/day) on oxidative status and on lipid profile in rats fed a cholesterol-rich diet. After 5 weeks treatment, plasma lipid values, hepatic enzyme activities and liver malondialdehyde (MDA) concentrations were measured. With the exception of the saponin fraction (SF), the administration of lyophilized asparagus (LA), fiber fraction (FF), and flavonoid fraction (FVF) to hypercholesterolemic rats produced a significant hypolipidemic effect compare to a high-cholesterol diet (HCD). In addition, the LA and FVF groups exhibited a significant increase in enzyme activity from multiple hepatic antioxidant systems including: superoxide dismutase, catalase, and gluthatione reductase/peroxidase as well as a decrease in MDA concentrations compared to HCD group. These results demonstrate that “triguero” asparagus possesses bioactive constituents, especially dietary fiber and flavonoids, that improve the plasma lipid profile and prevent hepatic oxidative damage under conditions of hypercholesterolemia.     

Precipitation and Optical Properties of CsPbBr3 Quantum Dots in Phosphate Glasses

CsPbBr₃ quantum dots were precipitated in phosphate glasses through heat treatment. Controlled formation of CsPbBr₃ quantum dots was realized by adjustment of heat‐treatment conditions. Absorption and photoluminescence spectra of CsPbBr₃ quantum dots were tuned from 432 to 521 nm. Upon ultraviolet or blue light excitation, efficient photoluminescence from these CsPbBr₃ quantum dots doped phosphate glasses was observed.     

Thyroid Hormones and Antioxidant Systems: Focus on Oxidative Stress in Cardiovascular and Pulmonary Diseases

In previous works we demonstrated an inverse correlation between plasma Coenzyme Q₁₀ (CoQ₁₀) and thyroid hormones; in fact, CoQ₁₀ levels in hyperthyroid patients were found among the lowest detected in human diseases. On the contrary, CoQ₁₀ is elevated in hypothyroid subjects, also in subclinical conditions, suggesting the usefulness of this index in assessing metabolic status in thyroid disorders. A Low-T3 syndrome is a condition observed in several chronic diseases: it is considered an adaptation mechanism, where there is a reduction in pro-hormone T4 conversion. Low T3-Syndrome is not usually considered to be corrected with replacement therapy. We review the role of thyroid hormones in regulation of antioxidant systems, also presenting data on total antioxidant capacity and Coenzyme Q₁₀. Published studies suggest that oxidative stress could be involved in the clinical course of different heart diseases; our data could support the rationale of replacement therapy in low-T3 conditions.     

Microwave-Assisted Synthesis of Glutathione-Capped CdTe/CdSe Near-Infrared Quantum Dots for Cell Imaging

These glutathione (GSH)-conjugated CdTe/CdSe core/shell quantum dot (QD) nanoparticles in aqueous solution were synthesized using a microwave-assisted approach. The prepared type II core/shell QD nanoparticles were characterized by UV–Vis absorption, photoluminescence (PL) spectroscopy, X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). Results revealed that the QD nanoparticles exhibited good dispersity, a uniform size distribution and tunable fluorescence emission in the near-infrared (NIR) region. In addition, these nanoparticles exhibited good biocompatibility and photoluminescence in cell imaging. In particular, this type of core/shell NIR QDs may have potential applications in molecular imaging.     

Preparation and Characterization of Highly Fluorescent, Glutathione-coated Near Infrared Quantum Dots for in Vivo Fluorescence Imaging

Fluorescent probes that emit in the near-infrared (NIR, 700–1,300 nm) region are suitable as optical contrast agents for in vivo fluorescence imaging because of low scattering and absorption of the NIR light in tissues. Recently, NIR quantum dots (QDs) have become a new class of fluorescent materials that can be used for in vivo imaging. Compared with traditional organic fluorescent dyes, QDs have several unique advantages such as size- and composition-tunable emission, high brightness, narrow emission bands, large Stokes shifts, and high resistance to photobleaching. In this paper, we report a facile method for the preparation of highly fluorescent, water-soluble glutathione (GSH)-coated NIR QDs for in vivo imaging. GSH-coated NIR QDs (GSH-QDs) were prepared by surface modification of hydrophobic CdSeTe/CdS (core/shell) QDs. The hydrophobic surface of the CdSeTe/CdS QDs was exchanged with GSH in tetrahydrofuran-water. The resulting GSH-QDs were monodisperse particles and stable in PBS (phosphate buffered saline, pH = 7.4). The GSH-QDs (800 nm emission) were highly fluorescent in aqueous solutions (quantum yield = 22% in PBS buffer), and their hydrodynamic diameter was less than 10 nm, which is comparable to the size of proteins. The cellular uptake and viability for the GSH-QDs were examined using HeLa and HEK 293 cells. When the cells were incubated with aqueous solutions of the GSH-QDs (10 nM), the QDs were taken into the cells and distributed in the perinuclear region of both cells. After 12 hrs incubation of 4 nM of GSH-QDs, the viabilities of HeLa and HEK 293 cells were ca. 80 and 50%, respectively. As a biomedical utility of the GSH-QDs, in vivo NIR-fluorescence imaging of a lymph node in a mouse is presented.     

Proteomic Analysis Reveals the Leaf Color Regulation Mechanism in Chimera Hosta “Gold Standard” Leaves

Leaf color change of variegated leaves from chimera species is regulated by fine-tuned molecular mechanisms. Hosta “Gold Standard” is a typical chimera Hosta species with golden-green variegated leaves, which is an ideal material to investigate the molecular mechanisms of leaf variegation. In this study, the margin and center regions of young and mature leaves from Hosta “Gold Standard”, as well as the leaves from plants after excess nitrogen fertilization were studied using physiological and comparative proteomic approaches. We identified 31 differentially expressed proteins in various regions and development stages of variegated leaves. Some of them may be related to the leaf color regulation in Hosta “Gold Standard”. For example, cytosolic glutamine synthetase (GS1), heat shock protein 70 (Hsp70), and chloroplastic elongation factor G (cpEF-G) were involved in pigment-related nitrogen synthesis as well as protein synthesis and processing. By integrating the proteomics data with physiological results, we revealed the metabolic patterns of nitrogen metabolism, photosynthesis, energy supply, as well as chloroplast protein synthesis, import and processing in various leaf regions at different development stages. Additionally, chloroplast-localized proteoforms involved in nitrogen metabolism, photosynthesis and protein processing implied that post-translational modifications were crucial for leaf color regulation. These results provide new clues toward understanding the mechanisms of leaf color regulation in variegated leaves.     

硅壳包裹核/壳型CdSe/CdS纳米晶的制备与性能研究

采用低温水热技术,分别以柠檬酸、聚乙二醇(PEG400)和甲硫氨酸为稳定剂,在水相中合成了核壳型CdSe/CdS量子点,研究了稳定剂、CdSe与CdS物质的量比对量子点发光性能和结构的影响。XRD结果表明,当CdSe∶CdS在1∶3~4时,CdS主要在CdSe的外延生长,形成核壳型纳米粒子,当比例达到1∶5时,CdS单独成晶现象严重。CdSe∶CdS=1∶4时,核壳型量子点具有较高的荧光发射效率。TEM研究表明CdS在CdSe外表面生长形成较为完整的壳层,有效钝化CdSe表面,减少表面缺陷,从而显著提高CdSe量子点的发光效率。CdSe核尺寸为2~3nm的核壳型纳米粒子外包裹一层SiO2壳后,荧光发射效率没有显著提高,发射峰位置无明显红移。量子点包壳后能有效提高该量子点的光化学稳定性,提高量子点的生物相容性。     

One-Pot Exfoliation of Graphite and Synthesis of Nanographene/Dimesitylporphyrin Hybrids

A simple one-pot process to exfoliate graphite and synthesize nanographene-dimesitylporphyrin hybrids has been developed. Despite the bulky mesityl groups, which are expected to hinder the efficient π–π stacking between the porphyrin core and graphene, the liquid-phase exfoliation of graphite is significantly favored by the presence of the porphyrins. Metallation of the porphyrin further enhances this effect. The resulting graphene/porphyrin hybrids were characterized by spectroscopy (UV-visible, fluorescence, and Raman) and microscopy (STEM, scanning transmission electron microscopy).     

Development of Molecularly Imprinted Polymer in Porous Film Format for Binding of Phenol and Alkylphenols from Water

Molecularly imprinted polymers (MIPs) were fabricated on glass slides with a “sandwich” technique giving ~20 μm thick films. Methanol/water as a solvent, and polyethyleneglycol and polyvinylacetate as solvent modifiers, were used to give a porous morphology, which was studied with scanning electron microscopy and gravimetric analysis. Various MIPs were synthesized through non-covalent imprinting with phenol as the template; itaconic acid, 4-vinylpyridine, and styrene as monomers; ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and pentaerythritol triacrylate (PETA) as cross-linkers. Binding and imprinting properties of the MIPs were evaluated based on phenol adsorption isotherms. Since phenol has only one weakly acidic hydroxyl group and lacks unique structural characteristics necessary for binding specificity, the preparation of selective MIPs was challenging. The recognition of phenol via hydrogen bonding is suppressed in water, while hydrophobic interactions, though promoted, are not specific enough for highly-selective phenol recognition. Nevertheless, the styrene-PETA MIP gave modest imprinting effects, which were higher at lower concentrations (Imprinting Factor (IF) = 1.16 at 0.5 mg·L⁻¹). The isotherm was of a Freundlich type over 0.1–40 mg·L⁻¹ and there was broad cross-reactivity towards other structurally similar phenols. This shows that phenol MIPs or simple adsorbents can be developed based on styrene for hydrophobic binding, and PETA to form a tighter, hydrophilic network.