基于微生物生物合成纳米颗粒机制的研究进展

纳米粒子的合成方法多种多样,包括物理法、化学法和生物合成法,其中生物合成法是以生物为基体的绿色合成方法。由于微生物易于培养、生长快、廉价易得,已成为纳米粒子生物合成法的重要生物类群。微生物和纳米材料的多样性决定了其合成机制的多样化。本文结合国内外的科研报道,着重介绍了目前纳米粒子生物合成机制,并对纳米粒子微生物合成技术未来发展趋势进行了展望。     

Quantum dot binding to DNA: Single-molecule imaging with atomic force microscopy

The interaction between nanoparticles (NPs) and DNA is of significance for both application and implication research of NPs. In this study, a single-molecule imaging technique based on atomic force microscopy (AFM) was employed to probe the NP-DNA interactions with quantum dots (QDs) as model NPs. Reproducible high-quality images of single DNA molecules in air and in liquids were acquired on mica by optimizing sample preparation conditions. Furthermore, the binding of QDs to DNA was explored using AFM. The DNA concentration was found to be a key factor influencing AFM imaging quality. In air and liquids, the optimal DNA concentration for imaging DNA molecules was approximately 2.5 and 0.25 μg/mL, and that for imaging DNA binding with QDs was 0.5 and 0.25 μg/mL, respectively. In the presence of QDs, the DNA conformation was altered with the formation of DNA condensates. Finally, the fine conformation of QD-DNA binding sites was examined to analyze the binding mechanisms. This work will benefit investigations of NP-DNA interactions and the understanding of the structure of NP-DNA bioconjugates. See accompanying article by Wang DOI: 10.1002/biot.201200309     

Application of Solanum lycopersicum (tomato) hairy roots for production of passivated CdS nanocrystals with quantum dot properties

Semiconductor quantum dot particles have a wide range of applications in medicine, bioassays, computing and photovoltaics. Biological synthesis is an attractive approach for mass production of quantum dots as cells have the capacity to passivate the particles with organic ligands. In this work, hairy roots of Solanum lycopersicum (tomato) were used to produce CdS nanoparticles with quantum dot properties. Treatment of the roots with 100 μM Cd during the mid-growth phase of batch culture elicited cellular responses for Cd detoxification without affecting root growth. A combination of freeze-drying and freeze-thawing of the roots was used to extract Cd from the biomass; anion-exchange chromatography was then applied to selectively remove metal–phytochelatin complexes. Size-fractionation using gel filtration allowed the recovery of phytochelatin-capped Cd- and inorganic sulphide-containing nanoparticles displaying the size and size-dependent optical/electronic properties of CdS quantum dots. At 4–10 nm in diameter, these particles fluoresced at wavelengths corresponding to blue-violet on the colour spectrum and exhibited a high level of photostability with prolonged excitation. Whereas 69% of the Cd extracted from the roots was associated with phytochelatin peptides, the maximum yield of CdS nanocrystals with quantum dot properties was 1.4% of the total Cd taken up into the biomass. This work demonstrates a new culture-based approach for the biosynthesis of metallo-organic semiconductor quantum dots using hairy roots.     

Nanoparticle-induced transition from positive to negative photochromism

We have designed and synthesized a photochromic spiropyran with a dithiolane appendage. The two sulfur atoms of the dithiolane ring encourage the adsorption of this compound on the surface of cadmium sulfide nanoparticles. The properties of the resulting photochrome-nanoparticle assemblies vary significantly with the experimental conditions selected for the preparation of the inorganic component. Nanoparticles prepared in the presence of tri-n-octylphosphine impose positive photochromism on the ligands. Instead, nanoparticles prepared in the presence of sodium dioctylsulfosuccinate impose negative photochromism on the ligand. This behavior is a consequence of the difference in the surface morphology of the two sets of nanoparticles. Indeed, emission spectra confirm the presence of surface defects on the nanoparticles exhibiting negative photochromism. Presumably, electrostatic interactions between these surface defects and the colored and zwitterionic isomer of the ligand are responsible for the transition from positive to negative photochromism. Thus, our studies demonstrate that the microscopic environment around a photochromic switch can regulate the relative stabilities of its colorless and colored states as well as their isomerization kinetics.     

Quantum dots for tracking cellular transport of lectin-functionalized nanoparticles

Successful drug delivery by functionalized nanocarriers largely depends on their efficient intracellular transport which has not yet been fully understood. We developed a new tracking technique by encapsulating quantum dots into the core of wheat germ agglutinin-conjugated nanoparticles (WGA-NP) to track cellular transport of functionalized nanocarriers. The resulting nanoparticles showed no changes in particle size, zeta potential or biobinding activity, and the loaded probe presented excellent photostability and tracking ability. Taking advantage of these properties, cellular transport profiles of WGA-NP in Caco-2 cells was demonstrated. The cellular uptake begins with binding of WGA to its receptor at the cell surface. The subsequent endocytosis happened in a cytoskeleton-dependent manner and by means of clathrin and caveolae-mediated mechanisms. After endosome creating, transport occurs to both trans-Golgi and lysosome. Our study provides new evidences for quantum dots as a cellular tracking probe of nanocarriers and helps understand intracellular transport profile of lectin-functionalized nanoparticles.     

Cancer Detection and Treatment: The Role of Nanomedicines

Nanotechnology is a field which has been at the forefront of research over the past two decades. The full potential of nanotechnology has yet to be fully realized. One subset of nanotechnology that has emerged is nanomedicine, which has been able to exploit the unique properties of nano-sized particles for therapeutics. Nanomedicine has the potential to increase the specific treatment of cancer cells while leaving healthy cells intact through the use of novel nanoparticles to seek and treat cancer in the human body. However, there are undoubtedly toxicities, which have not yet been fully elucidated. Various nano-carriers such as nanoshells, nanocrystals, nanopolymers, quantum dots, and dendrimers, and their role in early cancer detection and treatment have been discussed in this article.     

3D cellular spheroids as tools for understanding carboxylated quantum dot behavior in tumors

Background

Monolayer cell cultures have been considered the most suitable technique for in vivo cellular experiments. However, a lot of cellular functions and responses that are present in natural tissues are lost in two-dimensional cell cultures. In this context, nanoparticle accumulation data presented in literature are often not accurate enough to predict behavior of nanoparticles in vivo. Cellular spheroids show a higher degree of morphological and functional similarity to the tissues.

硒代硫酸钠诱导HL60细胞凋亡——还原态硒的细胞毒性(英文)

细胞毒性研究认为Cd2+的释放是硒化镉(CdSe)纳米粒子的细胞毒性机制之一,而Se2-阴离子在纳米粒子中的毒性机制未知。作者研究了硒代硫酸钠(selenosulfate(SSeO3)2-)对HL60细胞的细胞毒性作用,发现10μmol/L的硒代硫酸钠可以显著抑制细胞活力,诱导细胞凋亡,出现了染色质凝聚、DNA ladder和G0/G1凋亡亚峰。线粒体膜电位显著降低的同时,促凋亡蛋白Bax的免疫荧光增加。结果表明还原态的Se2-阴离子有显著的细胞毒性作用,可以诱导HL60细胞凋亡。同时也暗示Se2-阴离子的释放可能是含Se2-纳米粒子(比如硒化镉的量子点)细胞毒性的机制之一。     

Nanoparticle labels in immunosensing using optical detection methods

Efforts to improve the performance of immunoassays and immunosensors by incorporating different kinds of nanostructures have gained considerable momentum over the last decade. Apart from liposomes, which will not be discussed here, most groups focus on artificial, particulate marker systems, both organic and inorganic. The underlying detection procedures may be based either on electro-magnetical or optical techniques. This review will be confined to the latter only, comprising nanoparticle applications generating signals as diverse as static and time-resolved luminescence, one- and two-photon absorption, Raman and Rayleigh scattering as well as surface plasmon resonance and others. In general, all endeavors cited are geared to achieve one or more of the following goals: lowering of detection limits (if possible, down to single-molecule level), parallel integration of multiple signals (multiplexing), signal amplification by several orders of magnitude and prevention of photobleaching effects with concomitant maintenance of antigen binding specificity and sensitivity. Inorganic nanoparticle labels based on noble metals, semiconductor quantum dots and nanoshells appear to be the most versatile systems for these bioanalytical applications of nanophotonics.     

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, quantum dots should be highly fluorescent and small/monodisperse in size. While commonly used cadmium-based quantum dots possess these qualities, they are potentially toxic due to the possible release of Cd²⁺ ions through nanoparticle degradation. Indium-based quantum dots, specifically InP/ZnS, have recently been explored as a viable alternative to cadmium-based quantum dots due to their relatively similar fluorescence characteristics and size. The synthesis presented here uses standard hot-injection techniques for effective nanoparticle growth; however, nanoparticle properties such as size, emission wavelength, and emission intensity can drastically change due to small changes in the reaction conditions. Therefore, reaction conditions such temperature, reaction duration, and precursor concentration should be maintained precisely to yield reproducible products. Because quantum dots are not inherently soluble in aqueous solutions, they must also undergo surface modification to impart solubility in water. In this protocol, an amphiphilic polymer is used to interact with both hydrophobic ligands on the quantum dot surface and bulk solvent water molecules. Here, a detailed protocol is provided for the synthesis of highly fluorescent InP/ZnS quantum dots that are suitable for use in biomedical applications.     

体内光量子点可视化图像在脑肿瘤中的应用

恶性胶质瘤年发病率约为5/100,000。美国每年有超过14,000例的新发恶性脑胶质瘤患者。治疗主要以手术治疗为主,手术肿瘤的切除程度影响患者的预后。外科手术治疗脑肿瘤需要精确定位脑肿瘤组织在正常脑组织中的位置以便能够获得精确的组织活检和肿瘤的完全切除。量子点是稳定存在的,产生荧光的可视化半导体纳米晶体。静脉注射量子点伴随着网状内皮系统和巨噬细胞的隔离。巨噬细胞可渗入到肿瘤组织并且能够吞噬通过静脉注射的光量子来产生可视化的肿瘤标记。通过巨噬细胞介导,将光量子运输至肿瘤组织展现了一种新兴技术来标记术前肿瘤组织。由于肿瘤组织中的光量子可以被光学成像和光谱学工具来探测,因此在脑肿瘤组织活检和切除中可以为外科医生提供可视化得实时反馈。     

Size-modulated synergy of cellulase clustering for enhanced cellulose hydrolysis

Immobilization of enzymes onto nanoparticles for enhanced biocatalytic activity via enzyme clustering is a growing field. In this paper, the effect of nanoparticle size on the hydrolytic activity of artificial cellulosomes was investigated. A simple method based on metal affinity coordination was employed to directly conjugate two enzymes, an endoglucanase CelA and an exoglucanase CelE, onto CdSe–ZnS core–shell quantum dots (QDs) without the use of any chemical modification or linker molecules such as streptavidin. Artificial cellulosomes were created by clustering the enzymes onto two different QDs (5 and 10 nm) to systematically study the influence of particle size and QD to enzyme ratio on the enhancement in cellulose hydrolysis. Our results indicate that enzyme proximity is the most important factor for activity enhancement while the influence of particle size is relatively modest. This detailed understanding will provide insights for the design of other artificial cellulosomes based on nanoclustering of multiple catalytic domains with significantly enhanced activities, and may be applicable for designing improved nanobiocatalysts for biofuel production, bioremediation, and drug design.     

A novel hybrid simulation for study of multiscale phenomena

A novel multiscale model and simulation has been developed by combining the algorithms from a course grained 2D lattice model with Brownian dynamics (BD). The lattice model incorporates Lennard-Jones and coulombic interactions between particles, as well as nearest-neighbor interactions. The BD simulation allows the particles to move in solution before they adsorb to the surface. This hybrid simulation is used to study the behavior of nanoparticles in the presence of a surface and evaporation of solvent. The simulation is able to produce amorphous topologies of nanoparticles on the surface.     

Preparation of silica encapsulated quantum dot encoded beads for multiplex assay and its properties

Novel -COOH modified polystyrene beads were prepared by sulfonation grafting, and the surface area and pore volume are greatly improved in comparison with the swelling-treated beads. The optimization coating time is 4 h, and the corresponding -COOH content is approximately 2.1 mmol/g. The scanning electron microscope results show that the silica particles deposited on the beads and formed a silica shell that decreases the leakage of quantum dots (QDs) preferably and improves the bar code stability greatly. The anti-photobleaching of silica-coated beads was studied systemically, and the results show that the half-decay time (t1/2) of the coated beads increases to 537 s--seven times longer than that of the uncoated ones. Further DNA probe hybridization experiments indicated that the coding signal and target signal can be detected simultaneously and that the assays based on these probe-conjugated silica/QD/polystyrene beads have good specificity and sensitivity that can detect a concentration as low as 0.01 microg/ml target DNA in denatured calf thymus DNA solution, indicating that it is feasible to use this kind of bead for multiplex analysis.     

A PMMA microcapillary quantum dot linked immunosorbent assay (QLISA)

The development of a simple and inexpensive quantum dot based immunoassay for detecting myeloperoxidase (MPO) in stool samples is reported (QLISA). The method developed utilizes readily available polymethylmethacrylate (PMMA) microcapillaries as substrates for performing the sandwich assay. High power (80 mW) and low power (10 mW) UV-LEDs were tested for their efficiency in maximizing detection sensitivity in a waveguide illumination or a side illumination mode. The results obtained indicate that both waveguide and side illumination modes can be employed for detecting MPO down to 15 ng/mL, however the high power LED in a side illumination mode improves sensitivity and simplifies the data acquisition process. The protocol and sensor robustness was evaluated with animal stool samples spiked with MPO and the results indicate that the sensitivity of detection is not compromised when used in stool samples. The effect of the ionic strength of the environment on the fluorescence stability of quantum dots was evaluated and found to affect the assay only if long imaging times are employed. Replacing the buffer with glycerol during imaging increased the fluorescence intensity of quantum dots while significantly minimized the loss in intensity even after 2 h.     

Development of tyrosinase biosensor based on quantum dots/chitosan nanocomposite for detection of phenolic compounds

A sensitive and simple amperometric biosensor for phenols was developed based on the immobilization of tyrosinase into CdS quantum dots/chitosan nanocomposite matrix. The nanocomposite film with porous nanostructure, excellent hydrophilicity and biocompatibility resulted in high enzyme loading, and the tyrosinase (Tyr) immobilized in this novel matrix retained its activity to a large extent. The CdS quantum dots/chitosan nanocomposite film was characterized by scanning electron microscopy and electrochemical impedance spectroscopy, and the parameters of the various experimental variables for the biosensor were optimized. Under the optimal conditions, the designed biosensor displayed a wide linear response to catechol over a concentration range of 1.0 × 10⁻⁹ to 2.0 × 10⁻⁵ M with a high sensitivity of 561 ± 9.7 mA M⁻¹ and a low detection limit down to 0.3 nM at a signal-to-noise ratio of 3. The CdS quantum dots/chitosan nanocomposites could provide a novel matrix for enzyme immobilization to promote the development of biosensing and biocatalysis.     

Development of magnetic separation and quantum dots labeled immunoassay for the detection of mercury in biological samples

A rapid and sensitive immunoassays of mercury (Hg) in biological samples was developed using quantum dots (QDs) and magnetic beads (MBs) as fluorescent and separated probes, respectively. A monoclonal antibody (mAb) that recognizes an Hg detection antigen (BSA-DTPA-Hg) complex was produced by the injection of BALB/c mice with an Hg immunizing antigen (KLH-DTPA-Hg). Then the ascites monoclonal antibodies were purified. The Hg monoclonal antibody (Hg-mAb) is conjugated with MBs to separate Hg from biological samples, and the other antibody, which is associated with QDs, is used to detect the fluorescence. The Hg in biological samples can be quantified using the relationship between the QDs fluorescence intensity and the concentration of Hg in biological samples following magnetic separation. In this method, the detection linear range is 1–1000 ng/mL, and the minimum detection limit is 1 ng/mL. The standard addition recovery rate was 94.70–101.18%. The relative standard deviation values were 2.76–7.56%. Furthermore, the Hg concentration can be detected in less than 30 min, the significant interference of other heavy metals can be avoided, and the simultaneous testing of 96 samples can be performed. These results indicate that the method could be used for rapid monitoring Hg in the body.     

Synthesis and application of cNGR-containing imaging agents for detection of angiogenesis

Angiogenesis is a multi-step process regulated by pro- and anti-angiogenic factors. Inhibition of angiogenesis is a potential anti cancer treatment strategy that is now investigated clinically. In addition, advances in the understanding of the angiogenic process have led to the development of new angiogenesis therapies for ischemic heart disease.Currently, researchers search for objective measures that indicate pharmacological responses to pro- and anti-angiogenic drugs and therefore, there is a great interest in techniques to visualize angiogenesis noninvasively. As CD13 is selectively expressed in angiogenic blood vessels, it can serve as a target for molecular imaging tracers to noninvasively visualize angiogenic processes in animal models and patients. Here, an overview on the currently used CD13 targeted molecular imaging probes for noninvasive visualization of angiogenesis is given.     

Bionanocapsule-based enzyme-antibody conjugates for enzyme-linked immunosorbent assay

Macromolecules that can assemble a large number of enzyme and antibody molecules have been used frequently for improvement of sensitivities in enzyme-linked immunosorbent assays (ELISAs). We generated bionanocapsules (BNCs) of approximately 30 nm displaying immunoglobulin G (IgG) Fc-binding ZZ domains derived from Staphylococcus aureus protein A (designated as ZZ-BNC). In the conventional ELISA using primary antibody and horseradish peroxidase-labeled secondary antibody for detecting antigen on the solid phase, ZZ-BNCs in the aqueous phase gave an approximately 10-fold higher signal. In Western blot analysis, the mixture of ZZ-BNCs with secondary antibody gave an approximately 50-fold higher signal than that without ZZ-BNCs. These results suggest that a large number of secondary antibody molecules are immobilized on the surface of ZZ-BNCs and attached to antigen, leading to the significant enhancement of sensitivity. In combination with the avidin-biotin complex system, biotinylated ZZ-BNCs showed more significant signal enhancement in ELISA and Western blot analysis. Thus, ZZ-BNC is expected to increase the performance of various conventional immunoassays.     

Acoustic-based chemical tools for profiling the tumor microenvironment

Acoustic-based imaging modalities (e.g. ultrasonography and photoacoustic imaging) have emerged as powerful approaches to noninvasively visualize the interior of the body due to their biocompatibility and the ease of sound transmission in tissue. These technologies have recently been augmented with an array of chemical tools that enable the study and modulation of the tumor microenvironment at the molecular level. In addition, the application of ultrasound and ultrasound-responsive materials has been used for drug delivery with high spatiotemporal control. In this review, we highlight recent advances (in the last 2–3 years) in acoustic-based chemical tools and technologies suitable for furthering our understanding of molecular events in complex tumor microenvironments.