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PubMed2004

Attempted endocytosis of nano-environment produced by colloidal lithography by human fibroblasts.

Control of the cells' nanoenvironment is likely to be important in the future of cell and tissue engineering. Microtopography has been shown to provide cues to cells that elicit a large range of cell responses, including control of adhesion, morphology, apoptosis and gene regulations. Now, researchers are focusing on nanotopography as techniques such as colloidal and electron beam lithography and polymer demixing have become available. In this study, human fibroblast response to nanocolumns (160-nm high, 100-nm diameter, 230-nm centre-centre spacing) produced by colloidal lithography are considered. Using electron microscopy and immunofluorescence to image the cytoskeleton, clathrin and dynamin, it was observed that the cells try to endocytose the nanocolumns. It also appeared that a small population of the cells changed to unusual morphologies with macrophage-like processes and highly disrupted cytoskeleton. These observations could have implications for nanomaterials science in areas such as cell transfection and drug delivery.

Actins↗
PubMed2001

The mechanism of oxidation-induced low-density lipoprotein aggregation: an analogy to colloidal aggregation and beyond?

Atherosclerosis is a disease initiated by lipoprotein aggregation and deposition in artery walls. In this study, the de novo low-density lipoprotein aggregation process was examined. Nine major intermediates were identified in two stages of the aggregation process. In the aggregation stage, low-density lipoprotein molecules aggregate and form nucleation units. The nucleation units chain together and form linear aggregates. The linear aggregates branch and interact with one another, forming fractals. In the fusion stage, spatially adjacent nucleation units in the fractal fuse into curved membrane surfaces, which, in turn, fuse into multilamellar or unilamellar vesicles. Alternatively, some adjacent nucleation units in the fractals assemble in a straight line and form rods. Subsequently, the rods flatten out into rough and then into smooth ribbons. Occasionally, tubular membrane vesicles are formed from the fractals. The aggregation stage seems to be analogous to colloidal aggregation and amyloid fiber formation. The fusion stage seems to be characteristic of the lipid-rich lipoproteins and is beyond colloidal aggregation and amyloid fiber formation.

Amyloid↗
PubMed1993

Colloidal gold particles as an incompressible atomic force microscope imaging standard for assessing the compressibility of biomolecules.

Colloidal gold particles have multiple uses as three-dimensional atomic force microscopy imaging standards because they are incompressible, monodisperse, and spherical. The spherical nature of the particles can be exploited to characterize scanning tip geometry. As uniform spheres, colloidal gold particles may be used to calibrate the vertical dimensions of atomic force microscopy at the nanometer level. The monodisperse and incompressible nature of the gold can be used to characterize the vertical dimensions of coadsorbed biomolecules. Simultaneous measurements of gold with tobacco mosaic virus show that, at the same applied vertical force, the tobacco mosaic virus is undamaged by blunt tips but is compressed or disintegrated under sharper scanning styli, suggesting that specimen degradation is partly a pressure-dependent effect.

Biophysical Phenomena↗
PubMed2003

Layer-by-layer self-assembly of Prussian blue colloids.

The adsorption of Prussian blue (PB) colloids within layers of polyelectrolytes has been achieved by a reiterative immersion-rinse approach. Multilayer assemblies consisting of alternate layers of these components have been prepared by the layer-by-layer (LbL) self-assembly technique. Both processes have been carefully monitored by cyclic voltammetry and infrared and UV-visible spectroscopy. Linear increase in the IR and UV-visible light absorbance with the number of deposited layers indicates that well-organized lamellar systems have been elaborated. Size and distribution of Prussian blue nanoparticles in these systems have been investigated by AFM. The effect of the molar concentration of the PB dipping solution on the adsorption process and the distribution of the PB colloids has also been described. Finally, magnetic properties of these assemblies have been studied by low-temperature ESR measurements. Indeed, this new approach of hybrid LbL films opens the way to a new class of nanostructured lamellar compounds.

Adsorption↗
PubMed2003

Asymmetric alpha-helicity loss within a peptide adsorbed onto charged colloidal substrates.

A combination of circular dichroism and solution 1H NMR spectroscopy provides a localized description of the distribution of alpha -helical structure within the capped peptide DDDDAAAAARRRR (4DAR5) in aqueous solution and adsorbed onto anionic and cationic colloidal substrates. The adsorption-induced conformational changes are different from those observed upon heating 4DAR5 in solution, in which case the alanine segment remains largely alpha -helical and the transition to a coil structure propagates from the termini. Adsorption is driven by electrostatic complementarity, which places the charged peptide segment adjacent to the substrate of opposite charge. A similar pattern of alpha -helicity loss is observed whether the peptide is adsorbed onto anionic or cationic colloidal silica, despite inverse orientations; significant alpha -helicity loss occurs within the central alanine segment and the terminal arginine segment, whereas alpha -helicity is retained in the aspartate segment. This pattern of adsorption-induced conformational change illustrates the complex and subtle balance among the intramolecular and intermolecular factors that influence the conformations of adsorbed peptides and proteins.

Adsorption↗
PubMed1980

99m technetium sulfur colloid scanning in diagnosis of renal transplant rejection.

To evaluate the possible presence of rejection 37 99mtechnetium sulfur colloid imaging procedures were done on 17 renal transplant patients. There was good correlation between the clinical diagnosis and the results of the technetium sulfur colloid images, with no falsely positive studies in the series. An illustrative case and a review of pertinent literature confirm this technique to be an excellent method for the early detection of renal transplant rejection.

Colloids↗
PubMed2003

NOM-facilitated transport of metal ions in aquifers: importance of complex-dissociation kinetics and colloid formation.

The transport of metal ions (Al, Fe, Zn, Pb) complexed by natural organic matter (NOM) was investigated by column experiments. Direct breakthrough of metal-NOM complexes was observed after elution of one bed volume for Al, Fe, and Pb, but not for Zn. This observation cannot be understood assuming local thermodynamic equilibrium in the columns. Hence, a model was developed, taking into account the kinetics of the interactions of metal ions with NOM and the solid phase. Of all possible reactions during passage through the column, the dissociation of the metal-NOM complexes was assumed to be the rate-determining step. Dissociation-rate constants were determined by cation-exchange experiments with a non-NOM-adsorbing cation-exchange resin (Chelex-100). These rate constants were used to predict the migration of metal-NOM complexes in the column experiments. Experimental and modeling results were in good agreement for the bivalent metal ions. Also, the model well predicted the pH dependence of breakthrough of trivalent metal ions and the differences between Al and Fe breakthrough on a qualitative basis. This leads to the conclusion that the dissociation kinetics of metal-NOM complexes is an essential parameter for the estimation of NOM-facilitated metal transport. However, for the trivalent metals, Al and Fe, the model overestimated the direct breakthrough, thus giving a worst case prediction of metal transport. With the help of coupling size-exclusion chromatography to inductively coupled plasma-mass spectrometry, the formation of Al-hydroxide and Fe-hydroxide colloids in addition to NOM complexes was detected. These colloids, which were not considered in the model, were partially filtered off in the column, thus leading to overestimation of metal breakthrough.

Chromatography, Gel↗
PubMed2003

Effects of several low-molecular weight organic acids and phosphate on the adsorption of acid phosphatase by soil colloids and minerals.

Adsorption of acid phosphatase on goethite, kaolinite and two colloids from the soils in central and south China in the presence of organic acids and phosphate was studied. With the increase of anion concentration, the ability in decreasing enzyme adsorption followed the sequence: phosphate>tartrate>oxalate>acetate. Acetate showed promotive effect on enzyme adsorption at lower anion concentrations whereas oxalate, tartrate and phosphate compete effectively with enzyme in a broad range of anion concentration. The adsorption isotherms of enzyme in most of the anionic systems studied conformed to the Langmuir equation. Phosphate reduced the affinity of enzyme on goethite more significantly than the other anions. However, tartrate decreased the affinity of enzyme on soil colloids and kaolinite to a greater extent than phosphate, oxalate and acetate. This observation suggested that the impact of anions on enzyme adsorption varies with anionic type and the surface characteristics of soil components. The influence of the addition order of ligand on enzyme adsorption was found greater in tartrate and phosphate systems. In general, simultaneous introduction of ligand and enzyme into the system had the lowest enzyme adsorption, showing more competition between ligand and enzyme molecules in this system. Data from this work indicated that the status and activity of enzyme in certain soil microenvironments especially the rhizosphere where various organic and inorganic ligands are active can be altered and may be completely different from the bulk soil.

Acid Phosphatase↗
PubMed1978

Histochemical investigation of acid mucopolysaccharides in amyloid, colloid and hyaline.

The carbohydrate component in amyloid was histochemically compared with that in colloid or hyaline. Alcian blue, azure A, and periodic acid Schiff were used to stain mucopolysaccharides. In a further attempt to identify various polyanions, staining was carried out with alcian blue containing various concentrations of electrolytes. Methylation, saponification, acid hydrolysis, and digestion with streptomyces or testicular hyaluronidase, or chondroitinase ABC were also employed. The results obtained suggest that the presence of heparitin sulfate in amyloid, of chondroitin sulfate A in hyaline, and of chondroitin sulfate C in colloid.

Amyloid↗
PubMed1977

Incidence and severity of anaphylactoid reactions to colloid volume substitutes.

All available colloid volume substitutes carry the risk of anaphylactoid reactions. In a multicentre prospective trial, 69 cases of anaphylactoid reactions have been observed among 200 906 infusions of colloid volume substitutes. The frequency of severe reactions (shock, cardiac and/or respiratory arrest) was 0-003% for plasma-protein solutions, 0-006% for hydroxyethyl starch, 0-008% for dextran, and 0-038% for gelatin solutions.

Aged↗
PubMed1981

Treatment of recurrent corneal erosion and corneal edema with topical osmotic colloidal solution.

Ten patients with recurrent corneal erosion unresponsive to conventional therapy were treated with a topical colloidal solution to obtain epithelial dehydration and lubrication. Nine of the ten patients responded with improved vision and resolution of symptoms. All erosions healed and focal epithelial abnormalities were decreased or reversed. Similar treatment of ten patients with corneal edema due to endothelial decompensation did not significantly reduce symptoms or improve vision, but such a solution may have significant dehydrating effect when edema results solely from epithelial abnormalities. Pachometric studies of the cornea demonstrated no significant change in stromal thickness during therapy. Colloidal hyperosmotic solutions are well tolerated and appear effective in treating recurrent corneal erosion.

Colloids↗
PubMed1998

Lymphocyte fractionation using immunomagnetic colloid and a dipole magnet flow cell sorter.

The relationship between cell function and surface marker expression is a subject of active investigation in biology and medicine. These investigations require separating cells of a homogeneous subset into multiple fractions of varying marker expression. We have developed a novel cell sorter, the dipole magnet flow sorter (DMFS), which separates selected T lymphocyte subpopulations, targeted by immunomagnetic colloid, into multiple fractions according to cell surface marker expression, as determined by flow cytometry. A narrow stream of cells is introduced into a sheath of carrier fluid in a rectangular channel while subjected to a perpendicular magnetic force. The special design of the pole pieces ensures a constant magnetic force acting on the magnetically labeled cells in the separation area. Cells are spread across the flow in relation to their magnetophoretic mobility. Separation is achieved by control of the positions of the effluent stream boundaries, which separate fluid volumes with cells of different magnetophoretic mobility. CD4 and CD8 T lymphocytes labeled with primary antibody-fluorescein isothiocyanate (FITC) conjugate and anti-FITC-magnetic colloid are the chosen cell systems. Flow cytometry analysis shows that, for CD4 cells, a three-fold increase in total marker number per cell is observed when comparing the highest to the lowest fluorescence fractions. Similarly, a four-fold increase in total marker number is observed for CD8 cells. We also observed the separation of two dissimilar cell types that differed in expression of the CD4 marker, monocytes and T helper lymphocytes. We believe that this type of separation is applicable to any cells in suspension for which a suitable antibody exists and, due to the comparatively gentle nature of the process, is particularly suitable for the sorting of fragile cells.

Biomedical Engineering↗
PubMed2000

Polymer chemical structure is a key determinant of physicochemical and colloidal properties of polymer-DNA complexes for gene delivery.

Polyplexes are now emerging as potentially useful vectors for gene therapy. To improve our understanding of how the chemical structure of the polymer affects the properties of these systems, a series of structurally related polymers, the linear poly(amidoamine)s (PAAs), have been examined for their abilities to form complexes with DNA. Structure-dependent differences in DNA binding are shown by gel electrophoretic retardation of DNA and thermal transition analyses. Two PAAs, NG28 and NG30, stand out as having high affinity DNA binding characteristics, similar to the model homopolypeptide, poly-L-lysine. In addition, differences in complex formation, particle size and surface charge are displayed for the different polymer-DNA systems. Electron microscopy studies showed that the polymers condensed DNA into similar unit structures but only complexes with NG30 did not undergo agglomeration. This was attributed to an excess of complexed polymer forming a shell of uncomplexed polymer chain segments around a condensed DNA-polymer core. The transfection activities of these polymer complexes differ greatly, and some of these differences can be explained in a multifactorial way by the physicochemical and colloidal properties. It is concluded that polymer chemical structure dictates the apparent affinity of DNA binding, and also several of the important colloidal characteristics of the resulting complexes.

Chloroquine↗
PubMed1998

Fluid therapy. Crystalloids and colloids.

Appropriate fluid therapy requires an understanding of fluid dynamics and pathologic alterations during various disease states. In addition, it requires an understanding of the pharmacologic differences of available fluids. Crystalloid fluids and colloid fluids can be used in combination to treat a variety of volume-deficient states. Synthetic colloids are also used to treat hyponcotic states. Blood products are used to replace blood components and coagulation proteins. Frequent monitoring and reassessment are required to prevent volume overload and life-threatening edema.

Animals↗
PubMedDate not supplied

[Value of 99mTc-Sulphur colloid scintigraphy in the diagnosis of intermittent digestive bleeding secondary to a case of jejunal angiodysplasia].

We present the case of a 74 year old female patient, with clinical criteria of liver cirrhosis caused by hepatic C virus who required several admissions in our hospital over a five month period. She was given several blood transfusions because of repeated clinical manifestation of gastrointestinal bleeding without a clear origin. Her last admission was due to intermittent melenas, secondary anemia and hemodynamic angina. The patient's study included clinical analysis, fibrogastroscopy, colonoscopy, opaque enema, spiral CT and supraortic vessels arteriography. Because all the results to diagnose and locate the patient's disease were negative, she was referred to our service for a scintigraphy study. As it was an emergency case because of the patient's serious hemodynamic condition, a 99mTc-sulphur colloid scintigraphy was chosen, the results of which showed and located active gastrointestinal bleeding requiring urgent surgical intervention. The laparotomy with intrasurgical enterotomy and fibrogastroscopy undertaken ratified gastrointestinal bleeding, and the result of the biopsy of the jejunum removed in the intervention confirmed bowel angiodysplasia. Given the low incidence of gastrointestinal bleeding secondary to bowel angiodysplasia and absence of bibliographic references regarding the diagnosis of this disease in the above mentioned site by means of 99mTc-sulphur colloid scintigraphy in particular, we consider it interesting to highlight this case, in which the capability of this nuclear medicine technique for quick and non-invasive detection and location of gastrointestinal bleeding has been highly proven.

Aged↗
PubMed2001

Dissolved and colloidal transport of Cd, Pb, and Zn in a silt loam soil affected by atmospheric industrial deposition.

As a result of processing of metal ores, trace metals have contaminated large areas of northern France. Metal migration from the soil to groundwater presents an environmental risk that depends on the physico-chemical properties of each contaminated soil. Soil water samples were obtained over the course of 1 year with zero-tension lysimeters from an acidic, loamy, metal contaminated soil. The average trace metal concentrations in the soil water were high (e.g. for Zn 11 mg l-1 under the surface horizon), but they varied during the sampling period. Zn concentrations were not correlated with pH or total organic carbon in the solutions but were correlated with Cd concentrations. On average, 95% of the Zn and Cd but only 50% of Pb was present in a dissolved form. Analytical transmission electron microscopy was used to identify the Zn or Pb carriers. Colloids containing Pb and Zn were biocolloids, whereas colloids containing only Zn were smectites.

Air Pollutants↗
PubMed1997

Colloid osmotic properties of modified hemoglobins: chemically cross-linked versus polyethylene glycol surface-conjugated.

Colloid osmotic pressures of hemoglobin solutions containing unmodified, intramolecularly cross-linked, intermolecularly polymerized, or polyethylene glycol (PEG) surface-conjugated hemoglobin have been measured to determine their macromolecular solution properties. Tetrameric and polymeric hemoglobins show nearly ideal solution behavior: whereas, hemoglobins conjugated to PEG have significantly higher colloid osmotic activity and exhibit solution non-ideality. From these studies, the average calculated molecular weights are 65.300 +/- 3500 for unmodified and intramolecularly cross-linked hemoglobin tetramers, 156,000 for ring-opened raffinose polymerized human hemoglobin, 97,000 for pyridoxalated human hemoglobin conjugated to a carboxy-PEG polymer, and 117,000 for bovine hemoglobin conjugated to a methoxy-PEG polymer. The calculated radius of gyration for tetrameric hemoglobins is 2.9 +/- 0.2 nm compared to 4.9 nm for the polymerized hemoglobin, and 7.2 and 14.1 nm for the human and bovine PEG-conjugated hemoglobins, respectively. Exclusion volumes are calculated to be 823 +/- 148 nm3 for tetramers, 4000 nm3 for polymers, and 13,000 nm3 and 94,000 nm3 for human and bovine PEG-conjugated hemoglobins, respectively. These studies show that polyethylene glycol conjugated to surface amino groups greatly increases the effective macromolecular size of hemoglobin in solution.

Animals↗
PubMed1998

Crystalloids, colloids and kids: a review of paediatric burns in intensive care.

This is a retrospective review of all burns patients admitted to a paediatric intensive care unit (PICU) over a 7 year period. Resuscitation fluid therapy and clinical course are presented. Ninety-eight new burns victims were admitted with a mortality rate of 10.2%, all in burns of greater than 25% body surface area (BSA). The incidence of ARDS was 20%, with an 18% mortality rate. Of 85 patients with burns greater than 5% BSA, 33 received the hospital-recommended colloid-based resuscitation formula, 46 received a combination of crystalloids and colloids and in 6 patients the resuscitation regimen was not able to be determined. The aetiology, age distribution, sex ratio, severity of burns and length of stay in hospital did not alter significantly over the study period. The number of burns admissions to PICU increased, as did their duration of intubation and ICU stay. The hospital-recommended resuscitation formula consistently underestimated the fluid volume required for adequate resuscitation. No statistically significant difference in adverse effects was found between the resuscitation groups. This study is unable to recommend a definitive approach to the fluid resuscitation of burns shock in paediatrics and the best approach is one of meticulous fluid resuscitation titrated on clinical effect.

Adolescent↗