Colloidal Beads Research Articles

Multiplex analysis of tumor multidrug-resistance genes expression with photonic suspension array

An easy-operated suspension array based on silica colloidal crystal beads is developed for multiplex analysis of tumor multidrug-resistance genes expression, such as multidrug resistance 1 (MDR1) and multidrug resistance-associated protein 1 (MRP1), and potentially single nucleotide polymorphism. In order to obtain high fluorescence intensity, controlled PCR was used to amplify targets at the samples pretreatment stage. By optimizing the conditions a hybridization procedure, which is similar to nucleic acids analysis with binary probes, was established. Small amounts of analytes 10(-19) M could be detected by the method. The K562 cell, human myeloma cell, and its multidrug-resistance string, adriamycin-selected P-glycoprotein-overexpressed K562/A02, were analyzed by using an established procedure to validate feasibility. Clinical blood samples were detected by our method and real-time PCR simultaneously to validate accuracy. Moreover, when combined with multiplex controlled PCR, the method successfully meets the requirements of multiplex analysis. Hence, the method presented is a good method for multiplex analysis of tumor multidrug-resistance genes expression.

Chitosan–montmorillonite bio-based aerogel hybrid microspheres

Natural and biocompatible porous hybrid microspheres have been prepared by gelation of an intercalated “chitosan–montmorillonite” solution followed by drying with super-critical CO 2. This drying method allowed generating an open framework of fibrillar chitosan–montmorillonite in which chitosan is petrified by the clay platelets. Monitoring the formation of the dispersed colloidal beads microspheres by wide angle X-ray diffraction analysis evidenced the ingress (in acidic solution) and the egress (in basic solution) of chitosan scaffold within and from the montmorillonite galleries. Consistently with their high surface areas and enhanced accessibility, aerogel microspheres are found to be three times superior to their xerogel version in terms of methylene blue uptake. The presented hybrid materials take advantages from the chemical reactivity of chitosan backbone and the higher stability of clay platelets and pave the way toward positive synergetic effects.

Measuring adhesion forces between model polysaccharide films and PLA bead to mimic molecular interactions in flax/PLA biocomposite

Natural fiber-reinforced polymers or biocomposites are becoming increasingly popular as an environment friendly alternative to traditional glass fiber-reinforced thermoplastics. The mechanical properties of reinforced biocomposites, such as flax/polylactic acid (PLA), are largely governed by the level of interfacial interactions between the two constituents apart from their intrinsic properties. The hierarchical organization of various polysaccharides present in natural fibers results in complex mechanisms at the interface which are still poorly understood and difficult to analyze through a traditional approach that rely on indirect assessments. The possibility of measuring direct adhesion force between individual particles using the colloidal force microscopy has been exploited here by developing an experimental set-up in which a micrometer colloidal PLA bead is brought into close contact with molecularly smooth polysaccharide surfaces that mimic the main constituents of flax fibers, cellulose, hemicellulose, and pectins. Adhesion force measurements performed under ambient and low relative humidity conditions indicate that cellulose/PLA is the weakest interface in the biocomposite. Moreover, the results emphasize the important role of water molecules for the more hydrophilic polymers in flax fibers that takes place in the fundamental forces involved in the adhesion phenomena at the biocomposite interface.

Highly ordered macroporous carbon spheres and their catalytic application for methanol oxidation

Highly ordered three dimensionally macroporous carbon spheres (3DMPCS) were successfully prepared against removable colloidal silica crystal bead templates by carbonization of glucose. The unique structural characteristics of the well-developed three dimensionally interconnected macropores were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption. The 3DMPCS have uniform large pore structures with size about 250nm. Pt nanoparticles were supported on the macroporous carbon spheres by two aqueous impregnation methods, and it was found that the 3DMPCS supported Pt exhibited high electrocatalytic activity for methanol oxidation.

Elimination of chromatic aberration and tuning of the saturation in reflective flat-panel display by utilizing monodisperse colloidal crystal beads as pixels

We proposed an idea for overcoming the difficulties met by the application of colloidal photonic crystal in flat-panel displays, such as overcoming the viewing angle dependence, displaying a complicated image, and, how to control the brightness and saturation of each pixel. In our strategy, nanospheres were firstly self-assembled into uniform spherical units, and then the colloidal crystal units were patterned as pixels. This method was favorable to realize the fabrication of display device in a large scale, with controllable uniformity and easily pattern designing. The problem that display colors varies with the observation angle can probably be adequately corrected through the homogeneity derived from the spherical symmetry of the colloidal crystals. Nematic liquid crystals were infiltrated into the voids of the inverse opaline colloidal crystal unit, and the saturation of the pixels can be controlled by utilizing the field response feature of the liquid crystals.

Imaginary Magnetic Tweezers for Massively Parallel Surface Adhesion Spectroscopy

A massively parallel magnetic tweezer system has been constructed that utilizes the self-repulsion of colloidal beads from a planar interface via a magnetic dipole image force. Self-repulsion enables the application of a uniform magnetic force to thousands of beads simultaneously, which permits the measurement of unbinding histograms at the lowest loading rates ever tested. The adhesion of 9.8 μm polystyrene beads to a fluorocarbon, PEG, and UV-irradiated PEG surfaces were measured between 10(-3)-10(0) pN/s force loading rates, revealing the presence of both kinetic and quasi-equilibrium unbinding regimes.

A simple and rapid colloidal gold-based immunochromatogarpic strip test for detection of FMDV serotype A

A sandwich format immunochromatographic assay for detecting foot-and-mouth disease virus (FMDV) serotypes was developed. In this rapid test, affinity purified polyclonal antibodies from Guinea pigs which were immunized with sucking-mouse adapted FMD virus (A/AV88(L) strain) were conjugated to colloidal gold beads and used as the capture antibody, and affinity purified polyclonal antibodies from rabbits which were immunized with cell-culture adapted FMD virus (A/CHA/09 strain) were used as detector antibody. On the nitrocellulose membrane of the immunochromatographic strip, the capture antibody was laid on a sample pad, the detector antibody was printed at the test line(T) and goat anti-guinea pigs IgG antibodies were immobilized to the control line(C). The lower detection limit of the test for a FMDV 146S antigen is 11.7 ng/ml as determined in serial tests after the strip device was assembled and the assay condition optimization. No cross reactions were found with FMDV serotype C, Swine vesicular disease (SVD), Vesicular stomatitis virus (VSV) and vesicular exanthema of swine virus (VES) viral antigens with this rapid test. Clinically, the diagnostic sensitivity of this test for FMDV serotypes A was 88.7% which is as same as an indirect-sandwich ELISA. The specificity of this strip test was 98.2% and is comparable to the 98.7% obtained with indirect-sandwich ELISA. This rapid strip test is simple, easy and fast for clinical testing on field sites; no special instruments and skills are required, and the result can be obtained within 15 min. To our knowledge, this is the first rapid immunochromatogarpic assay for serotype A of FMDV.

Toward a UV–visible–near-infrared hyperspectral imaging platform for fast multiplex reflection spectroscopy

A reflection hyperspectral imaging system covering a 350-1000nm spectral range is realized by a UV-visible-near-IR Fourier transform imaging spectrometer. The system has a simple design and good spectral and spatial resolving performance. Accurate and fast microspectroscopic measurement results on novel colloidal crystal beads demonstrate the system has practical potential for high-throughput molecular multiplex assays.

Self-assembled autonomous runners and tumblers

A class of artificial microswimmers with combined translational and rotational self-propulsion is studied experimentally. The chemically fueled microswimmers are made of doublets of Janus colloidal beads with catalytic patches that are positioned at a fixed angle relative to one another. The mean-square displacement and the mean-square angular displacement of the active doublets are analyzed in the context of a simple Langevin description, using which the physical characteristics of the microswimmers such as the spontaneous translational and rotational velocities are extracted. Our work suggests strategies for designing microswimmers that could follow prescribed cycloidal trajectories.

Isolation of cell surface proteins for mass spectrometry-based proteomics

Defining the cell surface proteome has profound importance for understanding cell differentiation and cell–cell interactions, as well as numerous pathogenic abnormalities. Owing to their hydrophobic nature, plasma membrane proteins that reside on the cell surface pose analytical challenges and, despite efforts to overcome difficulties, remain under-represented in proteomic studies. Limitations in the classically employed ultracentrifugation-based approaches have led to the invention of more elaborate techniques for the purification of cell surface proteins. Three of these methods – cell surface coating with cationic colloidal silica beads, biotinylation and chemical capture of surface glycoproteins – allow for marked enrichment of this subcellular proteome, with each approach offering unique advantages and characteristics for different experiments. In this article, we introduce the principles of each purification method and discuss applications from the recent literature.

Multiplex tumor marker detection with new chemiluminescent immunoassay based on silica colloidal crystal beads

A new multiplex chemiluminescent immunoassay (CLIA) based on silica colloidal crystal beads (SCCBs) was developed for tumor marker detection. As the code is the characteristic reflection peak originating from the stop-band of colloid crystal, they avoid photobleaching, the potential interference of encoding fluorescence with analyte-detection fluorescence and chemical instability. Meanwhile our SCCBs suspension array improved the luminescence analysis efficiency by using chemiluminescent detection of enzyme labels. By forming a sandwich immunocomplex on SCCBs, the proposed suspension array was used for simultaneous multiplex detection of tumor markers in one test tube. The results showed that the linear range was 0.5-100ng ml(-1) and 1.0-120ng ml(-1) for carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) with a detection limit of 0.12ng ml(-1) and 0.16ng ml(-1) at 3sigma. The proposed array showed the storage stability and the accuracy for sample detection were acceptable, and the results were in acceptable agreement with the reference electrochemiluminescence method. This technique provided an automated, simple, sensitive and low-cost approach for multianalyte immunoassay.

The synchronization of superparamagnetic beads driven by a micro-magnetic ratchet

We present theoretical, numerical, and experimental analyses on the non-linear dynamic behavior of superparamagnetic beads exposed to a periodic array of micro-magnets and an external rotating field. The agreement between theoretical and experimental results revealed that non-linear magnetic forcing dynamics are responsible for transitions between phase-locked orbits, sub-harmonic orbits, and closed orbits, representing different mobility regimes of colloidal beads. These results suggest that the non-linear behavior can be exploited to construct a novel colloidal separation device that can achieve effectively infinite separation resolution for different types of beads, by exploiting minor differences in their bead's properties. We also identify a unique set of initial conditions, which we denote the "devil's gate" which can be used to expeditiously identify the full range of mobility for a given bead type.

Fabrication of Robust Crystal Balls from the Electrospray of Soft Polymer Spheres/Silica Dispersion

This paper presents a novel and facile approach to fabricate robust crystal balls directly through the self-assembly of soft colloidal polymer spheres by the aid of nano silica using an electrospraying technique. In this approach, soft colloidal polymer spheres are synthesized by emulsion polymerization and then blended with colloidal silica to obtain nanocomposite dispersion. When this dispersion is loaded into an injector and forced to flow through the nozzle under direct electric field, the detached droplets are collected by an oil solvent. As water and solvent evaporate, the colloidal polymer spheres and silica beads can directly self-assemble into robust crystal balls. Neither soft matrix nor post-treatment is needed. The obtained crystal balls have not only excellent mechanical properties to withstand external forces such as cutting, puckering, and bending, but also reversible deformation.

Quantitative Reflection Interference Contrast Microscopy (RICM) in Soft Matter and Cell Adhesion

Adhesion can be quantified by measuring the distance between the interacting surfaces. Reflection interference contrast microscopy (RICM), with its ability to measure inter-surface distances under water with nanometric precision and milliseconds time resolution, is ideally suited to studying the dynamics of adhesion in soft systems. Recent technical developments, which include innovative image analysis and the use of multi-coloured illumination, have led to renewed interest in this technique. Unambiguous quantitative measurements have been achieved for colloidal beads and model membranes, thus revealing new insights and applications. Quantification of data from cells shows exciting prospects. Herein, we review the basic principles and recent developments of RICM applied to studies of dynamical adhesion processes in soft matter and cell biology and provide practical hints to potential users.

Multiplex Chemiluminescent Immunoassay Based on Silica Colloidal Crystal Beads

The paper presented a novel multiplex chemiluminescence (CL) immunoassay method, which was based on silica colloidal crystals beads (SCCBs) as carriers using enhanced chemiluminescence (CL) detection of a horseradish peroxidase (HRP) catalyzing the luminal reaction. The monodisperse and size-controlled SCCBs were fabricated by a microfluidic device. The experimental conditions were optimized and analytical performance was studied. Results showed that the SCCBs as supports were much sensitive (0.05 ng/ml IgG) than the glass beads (18 ng/ml IgG) and the planar carriers (125 ng/ml IgG). A multiplex immunoassay suggested the feasibility of high throughput applications. This novel immunoassay system provided a simple, sensitive and low-cost approach for multianalyte immunoassay without using of expensive array detector.

Packing the Silica Colloidal Crystal Beads: A Facile Route to Superhydrophobic Surfaces

To mimic the structure of the lotus leaf, we present a facile route to prepare superhydrophobic surfaces by depositing nanoparticle clusters onto a solid surface. These clusters were fabricated via solidification of an emulsion droplet containing a nanoparticle in silicone oil. Thus, the microsized clusters and nanoparticles form dual-scale roughness structures. The surface is modified by fluoroalkylsilane and exhibits superhydrophobicity, with a contact angle greater than 165 degrees as well as a sliding angle less than 1 degrees . On the basis of size tuning of the nano/microstructures, various contact angles and sliding angles were investigated. Furthermore, the influence of micro/nanostructures on superhydrophobicity is discussed.

Low-Threshold Lasing in 3D Dye-Doped Photonic Crystals Derived from Colloidal Self-Assemblies

In this article, we demonstrated low-threshold lasing in three-dimensional (3D) polymeric photonic crystals derived from colloidal suspensions. To achieve this, we used monodisperse silica beads in a photocurable refractive index matched medium with high viscosity and polarity. In this system, the colloidal silica beads rapidly self-organized into nonclose-packed fcc crystals because of strong repulsive interparticle potential relative to diminishing van der Waals attraction, and subsequently the colloid crystals were solidified by UV irradiation. Dye molecules as optical gain medium were incorporated in the polymeric matrix by simply mixing the dye molecules and the photocurable suspension before casting the photonic crystal films. The translucent composite photonic films showed emission inhibition and enhancement due to the low photon density of states (DOS) at the stop band and high DOS at the band edge, respectively. On the other hand, the porous photonic films, which were prepared by removal of silica particles from the composite films, exhibited larger bandwidth and higher reflectivity (>80%) due to the enhanced refractive index contrast. Under irradiation of excitation light source, the porous photonic film showed strongly enhanced stimulated emission at the band edge by a factor of more than 300 with respect to the spontaneous emission of dye molecules embedded in a bulk film without nanostructure. In addition, the lasing wavelength could be controlled by simply changing the particle volume fraction in the composite films from which the porous films were prepared. Moreover, the threshold excitation intensity was reduced by a factor of one-tenth relative to the previously reported values. The simple method for preparing 3D photonic crystals described here and subsequent lasing characteristics have great potential in a broad range of applications including displays, μ-TAS, and optofluidic light sources.

Multiphysics Flow Modeling and in Vitro Toxicity of Iron Oxide Nanoparticles Coated with Poly(vinyl alcohol)

This study investigated the behavior of ferrofluids containing superparamagnetic iron oxide nanoparticles (SPION) of various compositions for potential applications in drug delivery and imaging. To ensure biocompatibility, the interaction of these SPION with two cell lines (adhesive and suspended) was also investigated using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The cell lines studied were primary mouse connective tissue cells (adhesive) and human leukemia cells (suspended). SPION were synthesized with a co-precipitation method under different stirring rates and NaOH molarities. The SPION demonstrated a range of magnetic saturations due to their different shapes, which included magnetite colloidal nanocrystal clusters (CNC’s), magnetic beads, and single-coated nanoparticles. All synthesized SPION maintained reasonable cell viability following exposure to cells. Flow cytometer tests showed that no apoptosis took place in cells exposed to SPION. A multiphysics numerica...

Anomalous yet Brownian

We describe experiments using single-particle tracking in which mean-square displacement is simply proportional to time (Fickian), yet the distribution of displacement probability is not Gaussian as should be expected of a classical random walk but, instead, is decidedly exponential for large displacements, the decay length of the exponential being proportional to the square root of time. The first example is when colloidal beads diffuse along linear phospholipid bilayer tubes whose radius is the same as that of the beads. The second is when beads diffuse through entangled F-actin networks, bead radius being less than one-fifth of the actin network mesh size. We explore the relevance to dynamic heterogeneity in trajectory space, which has been extensively discussed regarding glassy systems. Data for the second system might suggest activated diffusion between pores in the entangled F-actin networks, in the same spirit as activated diffusion and exponential tails observed in glassy systems. But the first system shows exceptionally rapid diffusion, nearly as rapid as for identical colloids in free suspension, yet still displaying an exponential probability distribution as in the second system. Thus, although the exponential tail is reminiscent of glassy systems, in fact, these dynamics are exceptionally rapid. We also compare with particle trajectories that are at first subdiffusive but Fickian at the longest measurement times, finding that displacement probability distributions fall onto the same master curve in both regimes. The need is emphasized for experiments, theory, and computer simulation to allow definitive interpretation of this simple and clean exponential probability distribution.

Power-Law Stress and Creep Relaxations of Single Cells Measured by Colloidal Probe Atomic Force Microscopy

We measured stress and creep relaxations of mouse fibroblast cells arranged and cultured on a microarray, by colloidal probe atomic force microscopy (AFM). A hydrophobic monolayer coating of perfluorodecyltrichlorosilane (FDTS) on the surface of colloidal silica beads significantly reduced the adhesion force of live cells, compared with untreated beads. The rheological behaviors of cells were estimated by averaging several relaxation curves of cells measured by the AFM. Longer-time tailing of both stress and creep relaxation curves followed single power-law behavior over a time scale of 60 s, with exponents in the range 0.1–0.4, varying with cells. The results were in good agreement with previous measurements of the frequency-domain rheology of cells using the force modulation mode.