Synthesis of immunomagnetic nanoparticles and their application in the separation and purification of CD34 hematopoietic stem cells

The silica-coated superparamagnetic nanoparticles with the uniform diameter of about 60 nm were synthesized by reverse microemulsions method. And the magnetic nanoparticles were modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS). The immunomagnetic nanoparticles were then successfully prepared by covalently immobilizing anti-CD34⁺ monoclonal antibodies to the surface of amino silane modified magnetic particles. The cell separation results showed that the synthesized immunomagnetic nanoparticles could rapidly and conveniently separate the CD34⁺ cells with high efficiency and specificity than normal ones. The surface morphology of separated target cells was examined by scanning electron microscope (SEM). Atomic force microscope (AFM) also characterized the magnetic materials on the surface of the separated target cells for the first time, which further confirmed that the target cells were separated by the immunomagnetic nanoparticles. The viability of the separated cells was studied by culturing method and Beckman Vi-cell viability analyst. Therefore, our experiments provided a new, direct, rapid mode to separate target cells.     

Laser-induced decoration of carbon nanotubes with metal nanoparticles

Hybrid nanomaterials consisting of multiwall carbon nanotubes (MWCNT) decorated with noble metal nanoparticles were produced by irradiating aqueous mixed solutions of the separate components with nanosecond lasers pulses at 248 nm. Specifically, the decoration with Au and Pd nanoparticles is discussed. No decoration of the MWCNT was observed by simple mixing with nanoparticle solutions. Hence, a photo-thermal mechanism is suggested, whereby the laser-heating of the nanoparticles induces melting, boiling and subdivision into smaller clusters and atoms, which then attach to the MWCNT.     

Femtosecond laser modification of living neuronal network

An all-wet femtosecond laser microprocessing technique was utilized for patterning and cutting functional network of living neuronal cells on a multi-electrode dish (MED). The neuronal cells cultured on a source substrate were transferred onto an electrode in a MED probe in solution by utilizing a femtosecond laser-induced impulsive force and a pattern of neuronal cells were formed on the MED probe. The cellular activity of the detached neurons was supported that neurites could be regenerated around the electrodes. As another processing method, the neurons stretching between electrodes were selectively cut by the direct femtosecond laser irradiation and the spontaneous electrical activity of the neuronal network was evaluated. While the spontaneous action potentials of neurons were synchronized before the cutting, the synchronization disappeared after the cutting, indicating that the neuronal network is locally disconnected by the laser cutting. The present method is applicable to artificial reconstruction of living neuronal network.     

Electrokinetic transport of nanoparticles to opening of nanopores on cell membrane during electroporation

Nanoparticle transport to the opening of the single nanopore created on the cell membrane during the electroporation is studied. First, the permeabilization of a single cell located in a microchannel is investigated. When the nanopores are created, the transport of the nanoparticles from the surrounding liquid to the opening of one of the created nanopores is examined. It was found that the negatively charged nanoparticles preferably move into the nanopores from the side of the cell membrane that faces the negative electrode. Opposite to the electro-osmotic flow effect, the electrophoretic force tends to draw the negatively charged nanoparticles into the opening of the nanopores. The effect of the Brownian force is negligible in comparison with the electro-osmosis and the electrophoresis. Smaller nanoparticles with stronger surface charge transport more easily to the opening of the nanopores. Positively charged nanoparticles preferably enter the nanopores from the side of the cell membrane that faces the positive electrode. On this side, both the electrophoretic and the electro-osmotic forces are in the same directions and contribute to bring the positively charged particles into the nanopores.     

Structural, optical and photoelectrochemical characterization of CdS nanowire synthesized by chemical bath deposition and wet chemical etching

Nanocrystalline thin films of CdS have been grown onto flexible plastic and titanium substrates by a simple and environmentally benign chemical bath deposition (CBD) method at room temperature. The films consist of clusters of CdS nanoparticles. The clusters of CdS nanoparticles in the films were successfully converted into nanowire (NW) networks using chemical etching process. The possible mechanism of the etching phenomenon is discussed. These films were examined for their structural, surface morphological and optical properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-vis spectrophotometry techniques, respectively. Photoelectrochemical (PEC) investigations were carried out using cell configuration as n-CdS/(1 M NaOH + 1 M Na₂S + 1 M S)/C. The film of nanowires was found to be hexagonal in structure with the preferential orientation along the (0 0 2) plane. The nanowires have widths in the range of 50-150 nm and have lengths of the order of a few micrometers. Optical studies reveal that the CdS nanowires have value of band gap 2.48 eV, whereas it is 2.58 eV for nanoparticles of CdS. Finally, we report on the ideality of junction improvement of PEC cells when CdS nanoparticles photoelectrode converted into nanowires photoelectrode.     

A simple thermal decomposition synthesis, magnetic properties, and cytotoxicity of La0.7Sr0.3MnO3 nanoparticles

This study reports the new and simple synthesis of magnetic La_0.7Sr_0.3MnO₃ (LSMO) nanoparticles by thermal decomposition method using acetate salts of La, Sr and Mn as starting materials. To obtain the LSMO nanoparticles, thermal decomposition of the precursor is carried out at the temperatures of 600, 700, 800, 900, and 1000°C for 6 hours. The synthesized LSMO nanoparticles were characterized by XRD, FT-IR, TEM and SEM. Structural characterization shows that the prepared particles consisted of two phases of LaMnO₃ (LMO) and LSMO with crystallite sizes ranging from 18 to 55 nm. All the prepared samples have a perovskite structure which changes from cubic to rhombohedral with the increase in the thermal decomposition temperature. Basic magnetic characteristics such as saturation magnetization (M _S) and coercive field (H _C) are evaluated by sample vibrating magnetometry at room temperature (20°C). The samples show soft ferromagnetic behavior with M _S values of ∼9–55 emu/g and H _C values of ∼8–37 Oe, depending on the crystallite size and thermal decomposition temperature. The relationship between the crystallite size and the magnetic properties is presented and discussed. The cytotoxicity of synthesized LSMO nanoparticles was also evaluated with NIH 3T3 cells and the result showed that the synthesized nanoparticles were not toxic to the cells as determined from cell viability in response to the liquid extraction of LSMO nanoparticles.     

Manipulation and soldering of carbon nanotubes using atomic force microscope

Manipulation of carbon nanotubes (CNTs) by an atomic force microscope (AFM) and soldering of CNTs using Fe oxide nanoparticles are described. We succeeded to separate a CNT bundle into two CNTs or CNT bundles, to move the separated CNT to a desirable position, and to bind it to another bundle. For the accurate manipulation, load of the AFM cantilever and frequency of the scan were carefully selected. We soldered two CNTs using an Fe oxide nanoparticle prepared from a ferritin molecule. The adhesion forces between the soldered CNTs were examined by an AFM and it was found that the CNTs were bound, though the binding force was not strong.     

Effects of hydroxyls on the structural and room temperature ferromagnetic properties of Co doped SnO2 nanoparticles

Co doped SnO₂ nanoparticles have been prepared via a wet chemical method with different precipitation processes. The structure and morphology of Co doped SnO₂ nanoparticles demonstrate that the nanoparticles are in a rutile single phase and uniform, respectively. X-ray photoelectron spectroscopy shows that the Co dopants are in 2+ oxidation valence state and doped ∼2 atm% in SnO₂ nanoparticles. Moreover, Raman spectroscopy further confirms that Co doped SnO₂ nanoparticles have single phase crystallinity without forming any extra modes related to secondary phases. The magnetic measurements reveal that all nanoparticles exhibit room temperature ferromagnetism (RTFM) due to the presence of disorders and defects introduced by hydroxyls in the crystal structure. In addition, it has been clearly observed that the saturated magnetic moments are strongly affected by the precipitation processes which control the incorporation of hydroxyls into the lattice.     

Modification of AFM Tips for Facilitating Picking-up of Nanoparticles

The radius of atomic force microscope (AFM) tip is a key factor that influences nonspecific interactions between AFM tip and nanoparticles. Generally, a tip with larger radius contributes to a higher efficiency of picking up nanoparticles. We provide two methods for modifying the AFM tip: one is to wear a tip apex on a solid substrate and the other is to coat a tip with poly (dimethylsiloxane) (PDMS). Both the approaches can enhance the adhesion force between the tip and nanoparticles by increasing tip radius. The experimental results show that a modified tip, compared to an unmodified one, achieves six-fold efficiency improvement in the capture of targeted colloidal gold nanoparticles.     

Ion synthesis and laser annealing of Cu nanoparticles in Al2O3

Al₂O₃ samples with Cu nanoparticles, synthesised by ion implantation at 40 keV with a dose of 1×10¹⁷ ion/cm² and a current density from 2.5 to 12.5 μA/cm², were annealed using ten pulses from a KrF excimer laser with a single pulse fluence of 0.3 J/cm². The copper depth distribution, formation and modification of metal nanoparticles under the ion implantation and laser treatment were studied by Rutherford backscattering (RBS), energy dispersive X-ray (EDX) analysis, atomic force microscopy (AFM) and optical spectroscopy. It was found that laser annealing leads to a reduction in the nanoparticle size without diffusion of metal atoms into the bulk. The change in particle size and the possibility for oxidation of the copper particles are examined in the framework of Mie theory. Calculations presented show that under excimer laser treatment, Cu nanoparticles are more likely to be reduced in size than to undergo oxidation. Received: 19 April 2001 / Accepted: 7 November 2001 / Published online: 23 January 2002     

Adhesion of chemically and electrostatically bound gold nanoparticles to a self-assembled silane monolayer investigated by atomic force volume spectroscopy

The adhesion of gold nanoparticles either electrostatically or chemically attached to a substrate has been probed using AFM operating in force spectroscopy mode. A monolayer of –NH₂ terminated 3-aminopropyltriethoxysilane or –SH terminated 3-mercaptopropyltrimethoxysilane was self-assembled onto a p-type silicon (100) substrate. Each silane monolayer provided the point of attachment for citrate stabilised gold colloid nanoparticles. In the case of the –NH₂ terminated layer gold colloid assembly was driven by the electrostatic attraction between the negative, citrate-capped, gold nanoparticles and a partially protonated amine layer. In the case of the –SH terminated regions, well-known gold–thiol chemistry was used to chemically attach the nanoparticles. An atomic force microscope tip was chemically modified with 3-mercaptopropyltrimethoxysilane and scanned across each surface, where the cantilever deflection was measured at each x, y pixel of the image to create an array of adhesion force curves. This has allowed an unprecedented nanoscale characterisation of the adhesion force central to two common surface attachment methods of gold colloid nanoparticles, providing useful insights into the stability of nanoscale constructs.     

Theoretical Study on the Capillary Force between an Atomic Force Microscope Tip and a Nanoparticle

Considering that capillary force is one of the most important forces between nanoparticles and atomic force microscope （AFM） tips in ambient atmosphere, we develop an analytic approach on the capillary force between an AFM tip and a nanoparticle. The results show that the capillary forces are considerably affected by the geometry of the AFM tip, the humidity of the environment, the vertical distance between the AFM tip and the nanoparticle, as well as the contact angles of the meniscus with an AFM tip and a nanoparticle. It is found that the sharper the AFM tip, the smaller the capillary force. The analyses and results are expected to be helpful for the quantitative imaging and manipulating of nanoparticles by AFMs.     

Dewetting of polymer films by ion implantation

We report dewetting of thermodynamically stable, thick (∼ 100 nm) polystyrene films by titanium ion implantation. The dynamic dewetting patterns in time evolution are recorded. The dewetting mechanism is determined to be heterogeneous nucleation, where the defects and Ti nanoparticles formed by ion implantation serve as the nuclei. In addition, we observe abundant rims with regular polygonal shapes in dewetting patterns. This is attributed to fingering instability, which results from the balance between the driving force arisen from thermally induced surface tension gradient and the resistive forces from the combination of friction force, Laplace pressure and long-range van der Waals interactions. Finally, a model based on mass conservation is used to qualitatively describe the transition from circular to polygonal shaped rims at a critical diameter for holes.     

Transformation mechanism of n-butyl terminated Si nanoparticles embedded into Si1−xCx nanocomposites mixed with Si nanoparticles and C atoms

Bright-field transmission electron microscopy (TEM) images, high-resolution TEM (HRTEM) images, and fast-Fourier transformed electron-diffraction patterns showed that n-butyl terminated Si nanoparticles were aggregated. The formation of Si_1−xC_x nanocomposites was mixed with Si nanoparticles and C atoms embedded in a SiO₂ layer due to the diffusion of C atoms from n-butyl termination shells into aggregated Si nanoparticles. Atomic force microscopy (AFM) images showed that the Si_1−xC_x nanocomposites mixed with Si nanoparticles and C atoms existed in almost all regions of the SiO₂ layer. The formation mechanism of Si nanoparticles and the transformation mechanism of n-butyl terminated Si nanoparticles embedded into Si_1−xC_x nanocomposites mixed with Si nanoparticles and C atoms are described on the basis of the TEM, HRTEM, and AFM results. These results can help to improve the understanding of the formation mechanism of Si nanoparticles.     

Role of surface ligands in nanoparticle permeation through a model membrane: a coarse-grained molecular dynamics simulations study

How nanoparticles interact with biological membranes is of significant importance in determining the toxicity of nanoparticles as well as their potential applications in phototherapy, imaging and gene/drug delivery. It has been shown that such interactions are often determined by nanoparticle physicochemical factors such as size, shape, hydrophobicity and surface charge density. Surface modification of the nanoparticle offers the possibility of creating site-specific carriers for both drug delivery and diagnostic purposes. In this work, we use coarse-grained molecular dynamic simulations to explore the permeation characteristics of ligand-coated nanoparticles through a model membrane. We compare permeation behaviors of ligand-coated nanoparticles with bare nanoparticles to provide insights into how the ligands affect the permeation process. A series of simulations is carried out to validate a coarse-grained model for nanoparticles and a lipid membrane system. The minimum driving force for nanoparticles to penetrate the membrane and the mechanism of nanoparticle–membrane interaction were investigated. The potential of the mean force profile, nanoparticle velocity profile, force profile and density profiles (planar and radial) were obtained to explore the nanoparticle permeation process. The structural properties of both nanoparticles and lipid membrane during the permeation, which are of considerable fundamental interest, are also studied in our work. The findings described in our work will lead to a better understanding of nanoparticle–lipid membrane interactions and cell cytotoxicity and help develop more efficient nanocarrier systems for intracellular delivery of therapeutics.     

带电纳米颗粒与相分离的带电生物膜之间相互作用的分子模拟

纳米颗粒在纳米医药、细胞成像等领域有着非常广泛的应用,深入理解纳米颗粒与生物膜之间相互作用的微观机制是纳米颗粒合成与应用的重要基础.本文采用粗粒化分子动力学模拟的方法研究了带电配体包裹的金纳米颗粒与相分离的带电生物膜之间的相互作用.结果表明,通过改变金纳米颗粒表面的配体密度、配体带电种类和比例,以及膜内带电脂分子的种类,可以方便地调控纳米颗粒在膜表面或膜内停留的位置和状态.进一步从自由能的角度分析了带电纳米颗粒与带电生物膜之间相互作用的微观物理机制.本文对纳米粒子在纳米医药、细胞成像等领域的应用具有一定的理论参考意义.     

Optical investigation on sulfur-doping effects in titanium dioxide nanoparticles

The sulfur-doping (S-doping) effects in TiO₂ nanoparticles are investigated by means of Raman spectroscopy and UV–Vis spectroscopy with different S-doping levels (10 and 50%). Raman spectra indicate that the rutile and anatase phases dominate for the low S-doped (10%) and high S-doped (50%) TiO₂ nanoparticles, respectively. The variation of phase with different S-doping levels has been ascribed to the different S-doping processes into TiO₂ nanoparticles. In addition, an extra absorption band is observed in both the S-doped TiO₂ nanoparticles. With increasing S-doping level from 10 to 50%, the extra absorption band shows a blue-shift from 470 to 445 nm, which may be ascribed to the variation of phase from rutile to anatase for TiO₂.     

Synthesis and gas sensing properties of perovskite CdSnO<Subscript>3</Subscript> nanoparticles

The CdSnO₃ semiconducting oxide that can be used as a gas-sensitive material for detecting ethanol gas is reported in this paper. CdSnO₃ nanoparticles were prepared by a chemical co-precipitation synthesis method, in which the preparation conditions were carefully controlled. The n-type gas-sensing semiconductors were obtained from the as-synthesized powders calcined at 600°C for 1 h. The phase and microstructure of the obtained nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) method with a gas adsorption analyzer. CdSnO₃ has a small particle size range of 30–50 nm and a high surface area of 9.12 m²/g, and a uniformity global shape. The gas sensitivity and operating temperature, and selectivity of CdSnO₃-based sensors were measured in detail. The gas sensors fabricated by CdSnO₃ nanoparticles had good sensitivity and selectivity to vapor of C₂H₅OH when working temperature at 267°C, the value of gas sensitivity at 100 ppm of C₂H₅OH gas can reach 11.2 times. Furthermore, gas-sensing mechanism was studied by using chromatographic analysis.     

自驱动颗粒体系中的熵力

在许多纳米复合材料体系中熵力(entropy force)是普遍存在的,但由于熵力的存在会导致纳米颗粒的凝聚从而降低其许多性能,因此在大多数情况下熵力的存在对体系并无益处,所以研究如何减小熵力对体系的影响是非常重要的.不带角速度的自驱动粒子在熵力作用下会集聚在纳米颗粒(或者纳米棒)周围,这会对纳米颗粒(或者纳米棒)产生很大的相互作用力.对于纳米颗粒,在不带角速度的自驱动粒子体系中存在着非常大的排斥力.而对于纳米棒,由于纳米棒内外的不对称性,使得两个纳米棒之间会产生吸引-排斥转变,同时这个吸引-排斥转变与纳米棒之间的距离有关.当自驱动粒子加上一个自转角速度ω之后,熵力的作用就大大减弱,纳米颗粒不再集聚.研究结果有助于对非平衡态下纳米颗粒(或纳米棒)之间熵相互作用力的认识.     

Fuzzy Impulsive Control of Permanent Magnet Synchronous Motors

The permanent magnet synchronous motors （PMSMs） may experience chaotic behaviours with systemic parameters falling into a certain area or under certain working conditions, which threaten the secure and stable operation of motor-driven. Hence, it is important to study the methods of controlling or suppressing chaos in PMSMs. In this work, the Takagi-Sugeno （T-S） fuzzy impulsive control model for PMSMs is established via the T-S modelling methodology and impulsive technology. Based on the new model, the control conditions of asymptotieal stability and exponential stability for PMSMs have been derived by the Lyapunov method. Finaily, an illustrated example is also given to show the effectiveness of the obtained results.