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At least 1,045 records · Page 58Linked to original sources
PubMed2005

Study on the immobilization of anti-IgG on Au-colloid modified gold electrode via potentiometric immunosensor, cyclic voltammetry, and electrochemical impedance techniques.

The immobilization of anti-IgG on Au-colloid modified gold electrodes has been investigated. A cleaned gold electrode was first immersed in a mercaptoethylamine (AET) solution, and then gold nanoparticles were chemisorbed onto the thiol groups of the mercaptoethylamine. Finally, anti-IgG was adsorbed onto the surface of the gold nanoparticles. Potentiometric immunosensor, cyclic voltammetry, and electrochemical impedance techniques were used to investigate the immobilization of anti-IgG on Au colloids. In the impedance spectroscopic study, an obvious difference of the electron transfer resistance between the Au-colloid modified electrode and the bare gold electrode was observed. The cyclic voltammogram tends to be more irreversible with increased anti-IgG concentration. Using the potentiometric immunosensor, the proposed technique is based on that the specific agglutination of antibody-coated gold nanoparticles, averaging 16 nm in diameter, in the presence of the corresponding antigen causes a potential change that is monitored by a potentiometry. It is found that the developed immunoagglutination assay system is sensitive to the concentration of IgG antigen as low as 12 ng mL(-1). Experimental results showed that the developed technique is in satisfactory agreement with the ELISA method, and that gold nanoparticles can be used as a biocompatible matrix for antibody or antigen immobilization.

Biocompatible Materials↗
PubMed2005

Influence of the colloidal crystal-like arrangement of polymethylmethacrylate bonded aerosil particles on the polymerization shrinkage of composite resins.

OBJECTIVE: Determination of the roles on the polymerization shrinkage during light-curing of composite resins of (i) the filler structuring effect of methylmethacrylate polymer adsorbed on fractal silica particles and (ii) of the crystal-like arrangement of the filler within the matrix. METHODS: Firstly, the domain of major efficiency of polymer in the aerosil agglomeration was determined. Secondly, the monomer system was changed in order to implement the spontaneous concentration of the filler within in a crystal-like arrangement. Finally, the rate of the polymerization shrinkage during light-curing of the resin was determined on the sediment recovered after centrifugation and on the colloidal crystal. Micro-modifications to the size of the samples were determined with the aid of the CCD Line Scan Sensor (H.-D. Rudolph GmbH, Germany). RESULTS: The composite micro-structure and the rate of polymerization shrinkage during light-curing of the resin are correlated with the amount of polymer initially supplied to the system that controls the degree of filler agglomeration. Different types of matrix/filler systems with typical shrinkage characteristics were sampled from the sediment containing amorphous and organized phases. The colloidal crystal-like system was determined to concentrate the filler within the matrix, and to give rise to the smallest shrinkage. SIGNIFICANCE: This study suggests that the silica particles embedded in a micro-structured polymer network (the filler scaffold) slowly develop spontaneously towards a colloidal crystal-like arrangement, and opens up new processes to reduce polymerization shrinkage.

Colloids↗
PubMed2005

Synthesis of colloidal dispersions of rhodium nanoparticles under high temperatures and high pressures.

Colloidal dispersions of rhodium (Rh) nanoparticles have been synthesized by the reduction of Rh ions (III) in high-temperature and high-pressure water, ethanol, or water-ethanol mixture under the existence of the protective polymer of poly(N-vinyl-2-pyrrolidone). The possibility of the regulation of the particle size and size distribution has been tested under several solvents at various temperatures and pressures. At 473 K and 25 MPa, particularly, concentrated colloidal dispersions of Rh particles of 2.5+/-0.5 nm were synthesized from the ionic solution of ethanol ([Rh]=15 mM) within a few seconds. Dilute colloidal dispersions of Rh particles were also synthesized from the dilute ionic solution ([Rh]=1.5 mM) with a diameter of 2.0+/-0.4 nm. From the water solution, Rh particles tended to form aggregates, especially for the lower concentration solution. In the case of solutions in water and ethanol mixture, the average diameter of Rh particles tended to be larger than in ethanol solution, and their distribution became broad.

Colloids↗
PubMed2005

A colloid "digesting" route to novel, thermally stable high surface area ZrO2 and Pd/ZrO2 catalytic materials.

Zirconia having high thermal stability and high surface area (up to 160 m(2)/g at 700 degrees C) has been prepared by a colloidal "digesting" process. This material having demonstrated high surface areas at elevated temperatures was then applied as a catalyst support. A Pd colloid with diameter of approximately 12 nm has been successfully deposited on the high surface area zirconia material. All systems have been well characterized by TEM, X-ray diffraction, N2 adsorption isotherms, FTIR, elemental analysis and dynamic light scattering techniques. The colloidal Pd particles have been found homogeneously well dispersed in the hydrous zirconia matrix without aggregation. The Pd/ZrO2 catalysts have been screened for cyclohexene and 1-hexene hydrogenation activity and it was found that the catalyst is extremely active.

Alkenes↗
PubMed2005

Influence of trivalent electrolytes on the humic colloid-borne transport of contaminant metals: competition and flocculation effects.

With the objective to assess the relevance of competitive effects in respect of the humic colloid-borne migration of actinides in case of release, the influence of Al(III) on humate complexation of La(III) as an analogue of trivalent actinides was investigated for various humic materials by using 140La as a radioactive tracer, allowing measurements in very dilute systems to simulate realistic settings. Generally, competition by aluminium is not detectable unless the metal-loading capacity of the humic colloids is nearly exhausted. For average contents of organic carbon, a threshold value of 10(-6) M Al(III) can be specified. The metal exchange turned out to be kinetically hindered. Effects on co-adsorption of La(III) and humic acid were found to be less important. Immobilization by the concomitantly induced flocculation process outweighs the role of displacement effects. Comparative studies on complexation and flocculation of humic acid with Al(III), Ga(III), In(III), Sc(III), Y(III), and La(III) were undertaken in order to evaluate the influence of specific properties apart from ion charge and to characterize the mechanism of flocculation. In spite of considerable variations in the binding affinities among these metals, it can be inferred that the possibility of significant competitive effects in natural aquatic systems is confined to Al(III). Complex stabilities and flocculation efficiencies proved to be interrelated. Precipitation is thus attributed to homocoagulation of humic colloids induced by charge compensation, which is further supported by flocculation experiments with Al(III) depending on pH, ionic strength, and humic acid concentration.

Adsorption↗
PubMed2005

Determination of surface-bound hydroxypropylcellulose (HPC) on drug particles in colloidal dispersions using size exclusion chromatography: a comparison of ELS and RI detection.

Evaporative light scattering (ELS) and refractive index (RI) detection methods were evaluated for the determination of surface-bound hydroxypropylcellulose (HPC) on drug particles in colloidal dispersions. Size exclusion chromatography (SEC) was used to separate HPC from other components of the dispersions. The instrumental parameters of the ELS detector were optimized to obtain maximum peak intensity, adequate peak shape and minimal baseline noise by varying the mobile phase flow rate, nebulizer temperature, and evaporation temperature. The chromatographic method was validated using both detectors. The ELS detector response exhibited second order polynomial and linear double logarithmic correlation with concentration over a 10-300% range while the RI response was linear. The double logarithmic correlation simplified the calculation compared to using the polynomial fit, and it provided more accurate results compared to the linear fit approach. Total HPC was obtained by solubilizing all components of the dispersion and analyzing for HPC. Non-bound HPC was obtained by ultracentrifuging the dispersion and analyzing the supernatant for HPC concentration. Analysis for total- and non-bound HPC in a representative colloidal dispersion gave method precisions with R.S.D.s of 2.5 and 2.2% for ELS, and 4.5 and 2.4% for RI (n=4). HPC bound to the surface of the drug particles was determined by difference: % bound HPC=100%-% non-bound HPC. Resultant % bound HPC values ranged from 22.1 to 25.4% of available HPC. Both ELS and RI are satisfactory detection techniques for HPC quantitation and for determination of the proportion of HPC bound to drug colloid particles, and the assay results are comparable.

Algorithms↗
PubMed2004

Resonance light scattering properties of Eu3+ in gold colloid.

Gold colloidal containing rare-earth ions Eu3+ were prepared at room temperature. Fluorescence spectra and resonance light scattering (RLS) spectra of Eu3+ ions and gold colloid containing Eu3+ were measured. For solution containing Eu3+, RLS features show two peaks at the edges of the visible light wavelength region. The short wavelength peak takes place at about 400 nm and the longer wavelength peak is the corresponding 1/2 fraction frequency RLS peak, which takes place at about 780 nm. When gold colloids were added to the solution containing Eu3+, both these two RLS peaks were enhanced. We believe that the energies, which are absorbed by the surface plasmon resonance in the gold nanoparticles, are efficiently transferred into the Eu3+ ions to cause the increased scattering.

Cations↗
PubMedDate not supplied

Optimization of a new preservation solution for machine perfusion of the liver: which is the preferred colloid?

AIMS: Machine perfusion (MP) has proven to be beneficial in experimental preservation of the liver. The modified University of Wisconsin solution (UW-Gluconate or UW-G) is used as the MP preservation solution of choice. We have developed Polysol, an enriched MP preservation solution based on a colloid. We sought to optimize Polysol by substituting the colloid hydroxyethylstarch (HES) with the colloids dextran and polyethylene glycol (PEG). METHODS: In an isolated perfused rat liver model, hepatocellular damage and liver function were assessed during reperfusion with Krebs-Henseleit buffer after 24 hours hypothermic MP using Polysol-HES, Polysol-dextran, or Polysol-PEG. Control livers were preserved by MP using UW-G. RESULTS: Compared to MP-UW-G, MP using Polysol resulted in significantly less damage and improved function during reperfusion. MP using Polysol-dextran or Polysol-PEG resulted in equal or less damage than Polysol-HES. Differences in ammonia clearance and bile production were not significant. Tissue edema was higher after MP using Polysol-HES as compared to Polysol-dextran and Polysol-PEG. CONCLUSIONS: MP of rat livers for 24 hours using UW-G results in more extensive damage and reduced liver function compared to MP using Polysol. MP using Polysol-dextran or Polysol-PEG results in equal or even better preservation compared to Polysol-HES.

Adenosine↗
PubMed2003

Tethered polymer chains: surface chemistry and their impact on colloidal and surface properties.

In this review the grafting of polymer chains to solid supports or interfaces and the subsequent impact on colloidal properties is examined. We start by examining theoretical models for densely grafted polymers (brushes), experimental techniques for their preparation and the properties of the ensuing structures. Our aim is to present a broad overview of the state of the art in this field, rather than an in-depth study. In the second section the interactions of surfaces with tethered polymers with the surrounding environment and the impact on colloidal properties are considered. Various theoretical models for such interactions are discussed. We then review the properties of colloids with tethered polymer chains, interactions between planar brushes and nanocolloids, interactions between brushes and biocolloids and the impact of grafted polymers on wetting properties of surfaces, using the ideas presented in the first section. The review closes with an outlook to possible new directions of research.

Colloids↗
PubMed1999

Cationic colloidal silica membrane perturbation as a means of examining changes at the sinusoidal surface during liver regeneration.

By employing the cationic colloidal silica membrane density perturbation technique, we examined growth factor receptor and extracellular matrix (ECM) changes at the sinusoidal surface during rat liver regeneration 72 hours after 70% partial hepatectomy (PHx). At this time after PHx, hepatocyte division has mostly subsided, while sinusoidal endothelial cell (SEC) proliferation is initiating, resulting in avascular hepatocyte islands. Because of the discontinuous nature of the surface of liver SEC, ECM proteins underlying the SEC, as well as SEC luminal membrane proteins, are available to absorption to the charged silica beads when the liver is perfused with the colloid. Subsequent liver homogenization and density centrifugation yield two separate fractions, enriched in SECs as well as hepatocyte basolateral membrane-specific proteins up to 50-fold over whole liver lysates. This technique facilitates examination of changes in protein composition that influence or occur as a result of SEC mitogenesis and migration during regeneration of the liver. When ECM and receptor proteins from SEC-enriched fractions were examined by Western immunoblotting, urokinase plasminogen activator receptor, fibronectin, and plasmin increased at the SEC surface 72 hours after PHx. Epidermal growth factor receptor, plasminogen, SPARC (secreted protein, acidic and rich in cysteine, also called osteonectin or BM40), and collagen IV decreased, and fibrinogen subunits and c-Met expression remained constant 72 hours after PHx when compared to control liver. These results display the usefulness of the cationic colloidal silica membrane isolation protocol. They also show considerable modulation of surface components that may regulate angiogenic processes at the end stage of liver regeneration during the reformation of sinusoids.

Animals↗
PubMed2002

A colloidal silver staining--destaining method for precise assignment of immunoreactive spots in two-dimensional protein patterns.

The characterization of protein expression patterns by two-dimensional gel electrophoresis depends on efficient and reliable identification strategies for target spots. In addition to sophisticated techniques, such as microsequencing and peptide mass spectrometry, immunodetection of membrane-immobilized proteins is a valuable method with which to identify the corresponding spots for a given set of candidate proteins. To precisely assign immunoreactive spots, this approach requires specific immunodetection and staining of total protein to be performed on the same membrane. Here, we describe a highly sensitive, colloidal silver-based method for the assignment of immunoreactive spots in two-dimensional protein patterns. This simple and rapid procedure involves a destaining step after staining of nitrocellulose-bound proteins with colloidal silver. We show that destaining of proteins is a prerequisite for subsequent immunodetection using enhanced chemiluminescence. Several types of antibodies were successfully employed for antigen detection after the staining-destaining procedure. Our results demonstrate that the colloidal silver-based method is generally applicable for the unambiguous identification of candidate proteins in complex two-dimensional patterns.

Animals↗
PubMed1984

Hydroxyethyl starch versus albumin for colloid infusion following cardiopulmonary bypass in patients undergoing myocardial revascularization.

Hydroxyethyl starch or hetastarch (HES), a synthetic colloid for intravascular volume expansion, was compared with albumin after coronary artery operations in 30 patients (15 in each study group). Cardiac index, atrial pressures, heart rate, and systolic blood pressure were similar in both groups. There were no differences in cumulative urine output at 24 hours or in weight change during the first 7 postoperative days. Values for colloid osmotic pressure, as well as for this variable minus left atrial pressure, were lowest soon after bypass but returned to baseline within 4 hours, with no difference between groups in the first 24 hours or 7 days after operation. Coagulation variables were similar, but prothrombin and partial thromboplastin times were higher 12 hours postoperatively and fibrinogen level was lower 7 days postoperatively in the patients receiving HES. There was no clinical evidence of excessive bleeding, although cumulative chest drainage at 12 and 24 hours was slightly higher in the HES group (p = 0.09 and 0.08, respectively). We conclude that hetastarch is a safe and effective colloid to use following coronary operations.

Albumins↗
PubMed2000

Interaction of cationic colloids at the surface of J774 cells: a kinetic analysis.

We have characterized the binding of multilamellar colloids to J774 cells. Cationic colloids were shown to bind much more efficiently than neutral ones. Particle uptake by cells was followed by flow cytometry and fluorescence microscopy. Analysis of the kinetics of uptake of cationic particles indicated that binding on the cell surface occurred with two characteristic times. Analysis of the dissociation properties allowed discriminating between several alternative models for adsorption and led us to propose a mechanism that involved two independent classes of binding sites on the cell surface. One class of sites appeared to be governed by a classic mass action law describing a binding equilibrium. The other sites were populated irreversibly by particles made of 10% cationic lipids. This was observed in the absence of endocytosis, under conditions where both the equilibrium and the irreversible binding occurred at the cell surface. We determined the rate constants for the different steps. We found that the reversible association occurred with a characteristic time of the order of tens of seconds, whereas the irreversible binding took a hundred times longer. The presence of serum proteins in the incubation medium did not drastically affect the final uptake of the particles. In contrast, the capture of the particles by cells significantly dropped when the fraction of positively charged lipids contained in the colloids was decreased from 10% to 5%. Finally, the results will be discussed within a comprehensive model where cationic particles find labile binding sites in the volume of the pericellular network (glycocalyx and extracellular matrix) and less-accessible irreversible binding sites at the cell membrane itself.

Animals↗
PubMed2003

Effects of synthetic lipids on solubilization and colloid stability of hydrophobic drugs.

Aqueous miconazole (MCZ) aggregates were solubilized and/or colloidally stabilized by bilayer-forming synthetic amphiphiles such as dioctadecyldimethylammonium bromide (DODAB) or sodium dihexadecylphosphate (DHP) dispersions. Particle sizing, light absorption and scattering from drug particles, zeta-potential determination, and drug aggregation kinetics from turbidity changes in the presence or absence of lipid dispersions were obtained over a range of drug and lipid concentrations. The very low solubility of MCZ in water made possible the determination of size distributions for drug particles in water and comparison to those in the presence of DODAB or DHP nanosized bilayer fragments or entire and closed bilayer vesicles. Large drug aggregates disappeared upon incubation with nanosized bilayer fragments produced by ultrasonic dispersion with tip. Light-absorption spectra for MCZ in a poor solvent (water), in a good organic solvent (methanol), and in different lipid dispersions showed that solubilization depended on the presence of bilayer fragments. MCZ was poorly soluble in dispersions formed of closed bilayers (vesicles) of DODAB or DHP in the gel state and in phosphatidylcholine (PC) vesicles in the liquid-crystalline state. Increased hydrophobicity at the borders of bilayer fragments explained MCZ solubilization. At [MCZ]>0.4 mM, kinetics of drug aggregation, zeta-potential measurements, and size minimization were obtained upon addition of minute amounts of oppositely charged bilayer fragments ([DHP]=0.05 mM), making possible determination of a remarkable stabilizing effect of drug particles by coverage with anionic bilayer fragments. High drug colloid stability in the presence of charged bilayer fragments was achieved by two different means: (1). at large drug concentrations and small concentrations of bilayer fragments, coverage of large drug particles with bilayer fragments; (2). at large amounts of bilayer fragments, drug solubilization in its monomeric form at the borders of bilayer fragments. Inexpensive, synthetic bilayer fragments offered a large area of hydrophobic nanosurfaces dispersed and electrostatically stabilized in water, opening new prospects for drug solubilization and colloid stabilization of insoluble drug particles.

Bromides↗
PubMed2003

Structural optimization of model colloidal clusters at the air-water interface using genetic algorithms.

The structure of colloidal clusters observed at the air-water interface is studied theoretically in this paper using a recently developed global optimization routine based on a genetic algorithm. A model potential with a secondary minimum produced from the attractive van der Waals interaction and repulsive dipolar interaction is used for the colloid-colloid interaction. The structures predicted from the genetic algorithm are not always consistent with the experimental observations; the theoretical results predict the growth of cluster as a spreading of triangular networks, however, the experimental observations seem to suggest the formation of a circular shell structure. More thorough theoretical as well as experimental studies are called for in order to obtain more conclusive evidence regarding these matters.

Air↗
PubMed2003

Development of a rapid, sensitive, dye immunoassay for schistosomiasis diagnosis: a colloidal dye immunofiltration assay.

The colloidal dye immunofiltration assay (CDIFA) combines the concepts of the double-antigen sandwich assay, the Dot immunofiltration assay, and colloidal dye-linked antigen technique to produce a new dye immunoassay for antibody detection in schistosomiasis. The CDIFA consisted of soluble egg antigen (SEA) of Schistosoma japonicum coated onto nitrocellulose membrane, mounted on a flow-through test device to provide the assay capture matrix. SEA absorbed to a red colloidal dye, R-3, produced in China, served as the antigen-antibody complex detecting reagents. The results showed that the sensitivity of the CDIFA was 100% in 35 cases of acute schistosomiasis (35/35), 98% in 50 cases of chronic schistosomiasis (49/50). The specificity of the assay was 99.4% in 180 healthy individuals (179/180). The cross-reaction was 13.3% in 30 cases of paragonimiasis, 2.6% in 38 cases of clonorchiasis sinensis and 0% in 20 cases of hookworm infection, 20 cases of fasciolopsiasis and 16 cases of ascariasis. The results were similar to those detected by routine enzyme-linked immunosorbent assay (ELISA). In a field evaluation of the CDIFA kit, the positivity rate of the CDIFA was 97.5% in 157 cases of schistosomiasis, compared with 91.1% with the circumoval precipitin test (COPT). The dye-labeled SEA conjugate was stable at room temperature for at least 6 months. The results indicated that the CDIFA provided an economic, simple, rapid, robust test for the detection of schistosome infection, suitable for a wide variety of field applications without any instrumentation.

Acute Disease↗
PubMed2003

Applications and limitations of the colloid titration method for measuring activated sludge surface charges.

Surface charge quantification of polymer solutions and sludge suspensions were investigated by the colloid titration technique and compared to charge densities obtained by pH-titration. The colloid titration technique worked well for polymer samples. The charge quantity of humic acid and activated sludge extracellular polymers (EPS) was estimated to be -1.51 and -0.42 meq/g, respectively. These values are reasonable when compared to pH-titration results. The surface charge of activated sludge particles appears to be below the limit of detection. However, surface charge estimates are obtained, when the reactant doses and sample concentration are increased. It is suggested that such estimates are not correct, but artefacts of the non-stoichiometric precipitation of the polymeric reactants at high doses. It appears that the colloid titration method is limited to conditions of low reactant doses and valid for charge determination of extracted sludge polymers, whereas the method is not valid for charge determination of whole sludge.

Colloids↗
PubMed2000

The effect of surface coatings on the association of orthophosphate with natural colloids.

A new method has been utilised for the characterisation of natural particle surface coatings. The method involves the use of sedimentation field-flow fractionation (SdFFF), radiolabelling and inductively coupled plasma-high resolution mass spectrometry (ICP-HR MS) techniques to study the effect of colloidal surface coatings on the adsorptive behaviour of orthophosphate. Colloidal river sediment and soil samples were chemically treated in an attempt to selectively remove metal hydroxyoxides and natural organic matter. The samples were then radiolabelled with 33PO4(3-) and analysed by SdFFF to determine the surface adsorption density (SAD) of orthophosphate as a function of particle size. The SdFFF unit was directly coupled to an ICP-HR MS to determine the chemical composition of the colloidal samples as a function of particle size. Element concentration/UV detector signal and element atomic molar ratios were plotted against particle size, and the trends used in the interpretation of SAD distribution (SADD) changes for the samples were studied. In general, non-constant trends in the orthophosphate SADDs were found, except for the river sediment treated with hydroxylamine hydrochloride. The results indicated that, in the soil sample studied, the Mn oxide coating was a dominant factor in determining phosphorus adsorption. This method could also be applicable to other industrial or similar samples.

Adsorption↗