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At least 775 records · Page 43Linked to original sources
PubMed2006

Detection of endoleaks after endovascular aneurysm repair with use of technetium-99m sulfur colloid and (99m)Tc-labeled red blood cell scans.

PURPOSE: This study was performed to determine whether endoleaks could be detected after endovascular aneurysm repair (EVAR) with use of technetium-99m sulfur colloid and (99m)Tc-labeled red blood cell (RBC) nuclear medicine scans. MATERIALS AND METHODS: There were 13 patients enrolled in this study: nine with endoleaks seen on computed tomographic (CT) angiography and four with no endoleak on CT angiography. All patients underwent regularly scheduled surveillance CT angiography examination after EVAR to evaluate for endoleak. Endoleak detection was then attempted in each patient with two nuclear medicine scans: a (99m)Tc sulfur colloid scan and a (99m)Tc-labeled RBC scan. Flow images (5 seconds per frame) were obtained for 1 minute after intravenous administration of 555 MBq (15 mCi) (99m)Tc sulfur colloid. Sequential dynamic images were then obtained every minute for 30 minutes. Next, a (99m)Tc-labeled RBC study was performed after the intravenous administration of 370-1,073 MBq (10-29 mCi) in vitro labeled (99m)Tc RBCs. Flow images were obtained, followed by sequential dynamic images obtained every minute for 30 minutes. Single photon emission CT images of the abdomen were then acquired. The nuclear medicine scans were evaluated for the presence or absence of endoleak independent of the CT angiography findings. RESULTS: Of the nine patients with endoleaks on CT angiography, seven (78%) had them detected by nuclear medicine examinations. Two of the nine endoleaks seen on CT angiography (22%) were not seen on either scintigraphic examination. All patients with no endoleak on CT angiography had their nuclear medicine scans correctly interpreted as showing no endoleak present (n = 4; 100%). No complications occurred as a result of the nuclear medicine scans. CONCLUSIONS: Endoleaks can be detected with (99m)Tc sulfur colloid and (99m)Tc-labeled RBC nuclear medicine scans. This initial work suggests that the sensitivities of these scintigraphic scanning methods for endoleak detection are lower than that of CT angiography.

Aortic Aneurysm, Abdominal↗
PubMed2003

Recent developments in European colloid solutions.

Coagulopathy resulting from hydroxyethyl starch (HES) administration is well documented for high-molecular-weight, highly substituted HES solutions. These are the only starch-based synthetic colloids approved for volume replacement in the United States. Recent developments in European colloid solutions revolve around designing new starch molecules. By increasing the C2:C6 ratio and decreasing the molar substitution to 0.4, a new HES with a molecular weight of 130,000 was introduced. This solution is without significant influence on coagulation. Actual experimental work is concentrating on modulating the inflammatory response of monocytes and endothelial cells after infusion of colloid solutions. This may help prevent or even correct capillary leak, and the intravascular persistence of infused colloidal might be prolonged.

Colloids↗
PubMed2007

Colloidal lithography and current fabrication techniques producing in-plane nanotopography for biological applications.

Substrate topography plays a vital role in cell and tissue structure and function in situ, where nanometric features, for example, the detail on single collagen fibrils, influence cell behaviour and resultant tissue formation. In vitro investigations demonstrate that nanotopography can be used to control cell reactions to a material surface, indicating its potential application in tissue engineering and implant fabrication. Developments in the catalyst, optical, medical and electronics industries have resulted in the production of nanopatterned surfaces using a variety of methods. The general protocols for nanomanufacturing require high resolution and low cost for fabricating devices. With respect to biological investigations, nanotopographies should occur across a large surface area (ensuring repeatability of experiments and patterning of implant surfaces), be reproducible (allowing for consistency in experiments), and preferably, accessible (limiting the requirement for specialist equipment). Colloidal lithography techniques fit these criteria, where nanoparticles can be utilized in combination with a functionalized substrate to produce in-plane nanotopographies. Subsequent lithographic processing of colloidal substrates utilizing, for example, reactive ion etching allows the production of modified colloidal-derived nanotopographies. In addition to two-dimensional in-plane nanofabrication, functionalized structures can be dip coated in colloidal sols, imparting nanotopographical cues to cells within a three-dimensional environment.

Biocompatible Materials↗
PubMed2003

Capillary condensation and interface structure of a model colloid-polymer mixture in a porous medium.

We consider the Asakura-Oosawa model of hard sphere colloids and ideal polymers in contact with a porous matrix modeled by immobilized configurations of hard spheres. For this ternary mixture a fundamental measure density functional theory is employed, where the matrix particles are quenched and the colloids and polymers are annealed, i.e., allowed to equilibrate. We study capillary condensation of the mixture in a small sample of matrix as well as demixing and the fluid-fluid interface inside a bulk matrix. Density profiles normal to the interface and surface tensions are calculated and compared to the case without matrix. Two kinds of matrices are considered: (i) colloid-sized matrix particles at low packing fractions and (ii) large matrix particles at high packing fractions. These two cases show fundamentally different behavior and should both be experimentally realizable. Furthermore, we argue that capillary condensation of a colloidal suspension could be experimentally accessible. We find that in case (ii), even at high packing fractions, the main effect of the matrix is to exclude volume and, to high accuracy, the results can be mapped onto those of the same system without matrix via a simple rescaling.

Biophysics↗
PubMed2003

Phase diagram of a quasi-two-dimensional colloid assembly.

We report the results of simulations of the phase diagrams of a quasi-two-dimensional (Q2D) colloid assembly and of a two-dimensional (2D) colloid assembly which have the same colloid-colloid interaction. That interaction is the same as used in the study reported by Zangi and Rice [Phys. Rev. E 58, 7529 (1998)]. Among the goals of the work reported are elucidation of the influence of small amplitude out-of-plane motion on the phase diagram of a system and determination of the effect of that motion on the role of a hexatic phase in the melting process. Both of the systems we have studied undergo a first-order solid I-solid II and solid II-solid III isostructural transition induced by the attractive and repulsive components of the interaction, respectively. Introduction of the out-of-plane motion shifts the low density portion of the phase boundaries involving the solid II phase. The liquid-solid I coexistence line is nearly the same for the two systems. The solid II-solid III transition is shifted to lower temperature and shifted to higher density in the quasi-two-dimensional system. We further use the simulations to calculate the elastic constants, which can be used to predict the location of the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) melting transition. For the Q2D system we find that the first-order melting transition preempts the KTHNY transition for the reduced temperatures T(*)=1.00, 0.60, and 0.50. For the 2D system, when T(*)=0.60, the KTHNY transition barely preempts the first-order melting transition and when T(*)=1.00 and 0.50 the ordinary first-order transition preempts the KTHNY transition.

Biophysics↗
PubMed2003

Crystal structures of two-dimensional magnetic colloids in tilted external magnetic fields.

The stability of different crystal lattices of two-dimensional superparamagnetic suspensions that are confined to a planar liquid-gas interface and exposed to a tilted external magnetic field is studied theoretically by lattice sum minimizations. The magnetic field induces magnetic dipoles onto the colloidal particles along its direction, whose strength can be controlled by the amplitude of the external field. The mutual interaction between the colloids is governed by dipole-dipole forces and a short-ranged repulsion having its physical origin at the presence of the colloidal cores. If the direction of the magnetic field is perpendicular to the liquid-gas interface, there is a purely repulsive interaction leading to stable triangular crystals. By tilting the external field, the interaction becomes anisotropic and a mutual attraction appears upon a threshold tilt angle. We have calculated the full phase diagram at zero temperature varying the tilt angle, the colloidal density, and the strength of the magnetic field. Apart from the triangular lattice we find a variety of stable crystal lattices including rectangular, oblique, chainlike oblique, and rhombic structures. We also present the accurate derivation of the Hamiltonian of two polarizable particles of finite arbitrary geometries in external magnetic and electric fields.

Colloids↗
PubMed2004

Statistical mechanics of a colloidal suspension in contact with a fluctuating membrane.

Surface effects are generally prevailing in confined colloidal systems. Here we report on dispersed nanoparticles close to a fluid membrane. Exact results regarding the static organization are derived for a dilute solution of nonadhesive colloids. It is shown that thermal fluctuations of the membrane broaden the density profile, but on average colloids are neither accumulated nor depleted near the surface. The radial correlation function is also evaluated, from which we obtain the effective pair potential between colloids. This entropically driven interaction shares many similarities with the familiar depletion interaction. It is shown to be always attractive with range controlled by the membrane correlation length. The depth of the potential well is comparable to the thermal energy, but depends only indirectly upon membrane rigidity. Consequences for the stability of the suspension are also discussed.

Colloids↗
PubMed2000

Patterned colloidal deposition controlled by electrostatic and capillary forces.

We use substrates chemically micropatterned with anionic and cationic regions to govern the deposition of charged colloidal particles. The direct observation of the colloidal assembly suggests that this process includes two steps: an initial patterned attachment of colloids to the substrate and an additional ordering of the structure upon drying. The driving forces of the process, i.e. , screened electrostatic and lateral capillary interactions, are discussed. This approach makes it possible to fabricate complex, high-resolution two-dimensional arrays of colloidal particles.

Capillary Action↗
PubMed2001

Phase separation in mixtures of colloids and long ideal polymer coils.

Colloidal suspensions with free polymer coils which are larger than the colloidal particles are considered. The polymer-colloid interaction is modeled by an extension of the Asakura-Oosawa model. Phase separation occurs into dilute and dense fluid phases of colloidal particles when polymer is added. The critical density of this transition tends to zero as the size of the polymer coils diverges.

Colloids↗
PubMed2003

Colloid-polymer mixtures in the protein limit.

We computed the phase-separation behavior and effective interactions of colloid-polymer mixtures in the "protein limit," where the polymer radius of gyration is much larger than the colloid radius. For ideal polymers, the critical colloidal packing fraction tends to zero, whereas for interacting polymers in a good solvent the behavior is governed by a universal binodal, implying a constant critical colloid packing fraction. In both systems the depletion interaction is not well described by effective pair potentials but requires the incorporation of many-body contributions.

Colloids↗
PubMed2005

Glasslike arrest in spinodal decomposition as a route to colloidal gelation.

Colloid-polymer mixtures can undergo spinodal decomposition into colloid-rich and colloid-poor regions. Gelation results when interconnected colloid-rich regions solidify. We show that this occurs when these regions undergo a glass transition, leading to dynamic arrest of the spinodal decomposition. The characteristic length scale of the gel decreases with increasing quench depth, and the nonergodicity parameter exhibits a pronounced dependence on scattering vector. Mode coupling theory gives a good description of the dynamics, provided we use the full static structure as input.

Colloids↗
PubMed2006

Branching of colloidal chains in capillary-confined nematics.

We report on the observation of colloidal chain assembly and branching inside capillaries filled with a nematic liquid crystal. Because of the homeotropic anchoring of liquid crystalline molecules on the capillary and colloidal droplet surfaces, the assembly of droplets along the capillary axis is expected, producing a transformation of the nematic director field from an escape-radial to quasiradial configuration. However, the subsequent over time branching of the straight colloidal chains is counterintuitive. By numerical simulations, we demonstrate that chain branching can occur by overcoming an energy barrier and can at least dwell as a metastable configuration. Moreover, manipulation of colloidal chains by electric fields and their gradients demonstrates various regimes of chain behavior in electric fields.

Biphenyl Compounds↗
PubMed1989

Rapid diagnosis in varicella and herpes zoster: re-evaluation of direct smear (Tzanck test) and electron microscopy including colloidal gold immuno-electron microscopy in comparison with virus isolation.

The Tzanck test and electron microscopy with the technique of colloidal gold labelling in varicella-zoster virus (VZV) infections were compared with virus isolation in 54 patients with clinically suspected varicella or herpes zoster infection. The Tzanck test and direct electron microscopy can determine whether or not an eruption is herpetic but cannot distinguish between herpes simplex virus (HSV) and VZV infection. However, colloidal gold immuno-electron microscopy, using monoclonal antibodies against HSV and anti-VZV IgG, can distinguish between these two herpes viruses. This achieves the same specificity as virus isolation followed by virus neutralization or virus typing using immunofluorescence techniques. The Tzanck test was positive in 91%, virus isolation, under optimal conditions of sampling and transportation, in 80%, direct electron microscopy (negative staining) in 80%, and colloidal gold immuno-electron microscopy after a virus concentration procedure in 95% of the cases. The colloidal gold technique offers a rapid diagnosis in patients with suspected VZV infection.

Adolescent↗
PubMed1989

Neuronal imaging with colloidal gold.

Colloidal gold is easily prepared, and readily adsorbs to a number of immunoreagents and other proteins for a wide variety of uses for neuronal visualization. Gold probes serve a role as immunolabels for both light and electron microscopy. As an ultrastructural immunocytochemical marker for detection of proteins, peptides or amino acids, gold can be used for immunostaining thick or thin sections prior to embedding, or for immunostaining ultrathin sections after embedding tissue in conventional or unusual embedding matrices. By virtue of its particulate nature, gold as an immunolabel facilitates a semi-quantitative analysis of relative antigen densities on ultrathin sections. Various combinations of different size gold particles or dual immunolabelling with enzymatic immunolabels together with colloidal gold or silver-intensified gold serve well for ultrastructural immunocytochemical localization of two antigens in the same tissue section. Colloidal gold can be detected with light microscopy, transmission and scanning electron microscopy, and with confocal laser microscopy. Silver intensification allows detection of gold at both the light and electron microscope level, and increases the sensitivity of immunogold procedures. Colloidal gold is useful as a tracer for physiological studies of transport and internalization in neurons in vivo and in vitro; computer-assisted video imaging techniques allow detection and tracking of single gold particles in living cells.

Animals↗
PubMed1985

Rationale for the use of colloids in the treatment of shock and hypovolemia.

The question, "Are colloids or crystalloids to be preferred for resuscitation in hypovolemic shock conditions?" is detailed in this review. The effects of these two types of fluid regimes on restitution of circulating blood volume, interstitial rehydration, microvascular blood flow, cellular metabolic recovery and on the incidence of systemic complications such as adult respiratory distress syndrome (ARDS), disseminated intravascular coagulation (DIC) and multiple organ failure are considered. Colloid containing solutions seem superior to crystalloids due to efficient reexpansion of circulating blood volume and enhancement of capillary blood flow. Resuscitation times and thereby the cellular hypoxic insult are considerable reduced while at the same time the formation of excessive tissue oedema is prevented. Colloids do not seem to adversely affect pulmonary function. Dextran has considerable advantages over other types of colloids for the initial shock treatment due to its antithrombotic properties whereby cell aggregability is prevented and the incidence of systemic complications (microembolism syndromes) is convincingly reduced.

Blood Volume↗
PubMed2005

Colloids decrease clot propagation and strength: role of factor XIII-fibrin polymer and thrombin-fibrinogen interactions.

Colloid-mediated hypocoagulability is clinically important, but the mechanisms responsible for coagulopathy have been incompletely defined. Thus, my goal was to elucidate how colloids decrease plasma coagulation function. Plasma was diluted 0% or 40% with 0.9% NaCl, three different hydroxyethyl starches (HES, mean molecular weight 450, 220 or 130 kDa), or 5% human albumin. Samples (n=6 per condition) were activated with celite, and diluted samples had either no additions or addition of fibrinogen (FI), thrombin (FIIa) or activated Factor XIII (FXIIIa) to restore protein function to prediluted values. Thrombelastographic variables measured included clot propagation (angle, alpha), and clot strength (amplitude, A; or shear elastic modulus, G). Dilution with 0.9% NaCl significantly decreased alpha, A and G-values compared to undiluted samples. Supplementation with FI, but not FIIa or FXIIIa, resulted in 0.9% NaCl-diluted thrombelastographic variable values not different from those of undiluted samples. FI supplementation of HES 450, HES 220, HES 130 and albumin-diluted samples only partially restored alpha, A and G-values compared to undiluted samples. FIIa addition only improved clot propagation and strength in albumin-diluted samples. FXIIIa supplementation improved propagation in samples diluted with HES 450, HES 220 and albumin, and clot strength improved in HES 450 and albumin-diluted plasma. Considered as a whole, these data support compromise of FIIa-FI and FXIIIa--fibrin polymer interactions as the mechanisms by which colloids compromise plasma coagulation. Investigation to determine if clinical enhancement of FXIII activity and/or FI concentration (e.g. fresh-frozen plasma, cryoprecipitate) can attenuate colloid-mediated decreases in hemostasis is warranted.

Albumins↗
PubMed2006

Visual detection of IS6110 of Mycobacterium tuberculosis in sputum samples using a test based on colloidal gold and latex beads.

The IS6110 sequence was detected visually in sputum samples of tuberculosis patients using a bi-probe system. One of the probes was an oligonucleotide conjugated to colloidal gold particles, complementary to one end of the target strand. The other probe was an oligonucleotide conjugated to latex beads complementary to the other end of the target strand. In a reaction mix, these two probes bind to the target strand, and the latex beads are then separated by filtration. Bound latex beads have gold colloid particles at the other end of the target strand. These gold colloid particles were made visible to the naked eye by silver autometallography on the 'invisible' colloidal gold particles. The lower detection limit was 50 ng of genomic DNA of Mycobacterium tuberculosis. This new test, together with conventional PCR, was performed on DNA extracted from sputum samples of suspected tuberculosis patients. The new test was simple to perform, the results were visible to the naked eye, and the test was highly specific, as even single point mutations in the target strand sequence could be differentiated. The test could be useful in field-level laboratories because it requires no sophisticated equipment.

Bacteriological Techniques↗
PubMed2003

Inoculation of plasmids encoding Japanese encephalitis virus PrM-E proteins with colloidal gold elicits a protective immune response in BALB/c mice.

We established a simple and effective method for DNA immunization against Japanese encephalitis virus (JEV) infection with plasmids encoding the viral PrM and E proteins and colloidal gold. Inoculation of plasmids mixed with colloidal gold induced the production of specific anti-JEV antibodies and a protective response against JEV challenge in BALB/c mice. When we compared the efficacy of different inoculation routes, the intravenous and intradermal inoculation routes were found to elicit stronger and more sustained neutralizing immune responses than intramuscular or intraperitoneal injection. After being inoculated twice, mice were found to resist challenge with 100,000 times the 50% lethal dose (LD(50)) of JEV (Beijing-1 strain) even when immunized with a relatively small dose of 0.5 micro g of plasmid DNA. Protective passive immunity was also observed in SCID mice following transfer of splenocytes or serum from plasmid DNA- and colloidal gold-immunized BALB/c mice. The SCID mice resisted challenge with 100 times the LD(50) of JEV. Analysis of histological sections detected expression of proteins encoded by plasmid DNA in the tissues of intravenously, intradermally, and intramuscularly inoculated mice 3 days after inoculation. DNA immunization with colloidal gold elicited encoded protein expression in splenocytes and might enhance immune responses in intravenously inoculated mice. This approach could be exploited to develop a novel DNA vaccine.

Animals↗