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PubMed1994

[Use of colloids in acute hypovolemia].

In Denmark several natural and synthetic colloids are available. Natural colloids are fresh frozen plasma (FFP) and human albumin (HA). Both are ideal as plasma expanders, but FFP can carry infectious agents and HA is quite expensive. The synthetic colloids or modified macromolecules are the dextrans (Macrodex (MD) and Rheomacrodex (RMD)), Haemaccel (HC), and Haes-steril (HS) in 6 and 10% solutions. HC has few indications because of a questionable volume expansion and a relatively high frequency of side effects. RMD is useful in cases of compromised regional blood flow. HS 10% and HA 20% are hyperoncotic and are effective in redistributing interstitial fluid to the intravascular space. HS and MD are both effective as volume substitutes. In addition HS and MD have beneficial side effects such as an inhibition of erythrocyte aggregation and inhibition of leucocyte marginalisation. Furthermore, MD has an anti-thrombotic effect. However, MD has in contrast to HS a dose dependent effect on the bleeding time. HS and MD are effective in restoring the colloid osmotic pressure and can in many cases replace HA in treatment of hypovolaemia.

Acute Disease↗
PubMed1977

The effects of cardiopulmonary bypass with crystalloid and colloid hemodilution on myocardial extravascular water.

The effect of cardiopulmonary bypass (CPB) on myocardial extravascular water (MEW) was evaluated with crystalloid and colloid hemodilution. Heart water was measured gravimetrically and by the double-indicator and thermal methods. CPB without hemodilution resulted in a 5.7 per cent increase in the wet : dry weight ratio of the left ventricle obtained by desiccation to stable weight. CPB with colloid hemodilution to a hematocrit of 10.7 +/- 0.4 per cent resulted in a 5.4 per cent increase in the wet:dry weight ratio. Crystalloid hemodilution to a hematocrit of 9.5 +/- 0.8 per cent resulted in a marked increase in myocardial water with a wet:dry weight ratio 30.3 per cent greater than the controls. Hypothermic (22 degrees C.) crystalloid hemodilution resulted in a 37.4 per cent increase in the wet:dry weight ratio. MEW was also measured by the double-indicator method with Evans blue dye and tritiated water. This method measured 85 per cent of the gravimetrically measured water. Although it indicated the increase in heart water in the crystalloid group, it proved less reliable in the measurement of MEW in this dynamic situation. The thermal heart water was also measured with an impedance and thermistor-bearing catheter similar to that used to measure thermal lung water. This proved ineffective in measuring heart water. Colloid hemodilution was thus found to prevent the development of myocardial edema which occurred with crystalloid hemodilution (p less than 0.01) with and without hypothermia. These findings support the addition of colloid to the hemodilution prime used for cardiopulmonary bypass.

Animals↗
PubMed1993

Pharmacologic and clinical considerations in selecting crystalloid, colloidal, and oxygen-carrying resuscitation fluids, Part 1.

The pharmacologic properties of crystalloid, colloidal, and oxygen-carrying resuscitation fluids are described, and the findings of clinical trials of these solutions are discussed. Fluid administration is a fundamental part of resuscitation therapy. Crystalloid solutions supply water and sodium to maintain the osmotic gradient between the extravascular and intravascular compartments. Examples are lactated Ringer's injection and 0.9% sodium chloride injection. Colloidal solutions, such as those containing albumin, dextrans, or starches, increase the plasma oncotic pressure and effectively move fluid from the interstitial compartment to the plasma compartment. Oxygen-carrying resuscitation fluids, such as whole blood and artificial hemoglobin solutions, not only increase plasma volume but improve tissue oxygenation. Clinically, colloidal solutions are generally superior to crystalloids in their ability to expand plasma volume. However, colloids may impair coagulation, interfere with organ function, and cause anaphylactoid reactions. Crystalloid solutions represent the least expensive option and are less likely to promote bleeding, but they are more likely to cause edema because larger volumes are needed. Favorable experience with inexpensive hypertonic crystalloids with improved plasma volume expansion properties may favor a return to resuscitation with crystalloid solutions. Oxygen-carrying resuscitation fluids are indicated when the patient has lost more than 25% of the total blood volume. Tailoring therapy to the individual patient and close monitoring are essential to safe and effective fluid resuscitation.

Colloids↗
PubMed1979

[Effect of kidney function on the elimination and action of colloidal plasma substitutes].

Hypovolemia and prophylaxis of thrombosis are the main indications for colloidal plasma substitutes. This is also true for patients with renal failure. Due to their difference in molecular structure colloidal plasma substitutes, which are in clinical use--dextran, hydroxyethyl starch, gelatin--, are eliminated tbrough different pathways. However, the kidney plays an important role in the elimination of all three substances. Therefore pharmacokinetics and pharmacodynamics of colloidal plasma substitutes, which are based on dextran, hydroxyethyl starch and gelatin, were studied in patients with normal or impaired renal function. Renal insufficiency proved to affect the elimination and therapeutic efficacy of these colloids in different and characteristic ways. Consequently this requires special indications and dosage recommendations for patients with renal insufficiency.

Anuria↗
PubMedDate not supplied

Effect of recirculation of 99mTc-Sn colloid in estimating mean transit time of soft-tissue vascular anomalies by direct puncture scintigraphy: a simulation analysis.

We have reported direct puncture scintigraphy, a novel method to estimate mean transit time (MTT) of soft-tissue vascular anomaly. In the examination, 99mTc-Sn colloid is infused percutaneously into the lesion, and MTT is calculated using the time-activity curve for the lesion. Recirculation of 99mTc-Sn colloid is neglected in computing MTT, and this may cause error. The aim of this study was to assess this error by simulation analysis. Data simulating direct puncture scintigraphy were produced for lesions with various blood volumes and various blood flows, considering recirculation and blood clearance of 99mTc-Sn colloid, and MTT was estimated by the same method used in the patient examination. Although MTT was overestimated in large lesions with intermediate or long MTT, the error was small except in extremely large lesions. It was suggested that recirculation of 99mTc-Sn colloid does not cause a serious problem in the clinical use of direct puncture scintigraphy.

Arteriovenous Malformations↗
PubMed2006

Co/CNF catalysts tailored by controlling the deposition of metal colloids onto CNFs: preparation and catalytic properties.

Carbon nanofiber-supported Co nanocomposites were prepared by means of a modified ethylene glycol (EG) process, in which the Co salts are reduced in EG and are subsequently deposited onto carbon nanofibers (CNFs). It has been found that the deposition of cobalt colloids onto CNFs can be tailored by simply adjusting the pH of the EG and by heating the mixture of CNFs and colloidal solution at 100 degrees C for some time. The pH value (<7) and the temperature (at least 100 degrees C) for heating the mixture of CNFs and colloidal solution are found to be the key factors for depositing Co particles onto CNFs. The obtained Co/CNFs have a high and homogeneous dispersion of spherical Co metal particles with a narrow size distribution of 10-15 nm with a peak around 13.5 nm; this result is consistent, to a certain degree, with the value of 12.8 nm obtained from the XRD study. The different states of the stabilizer including carboxylates (pH>7) and carboxylic acids (pH<7) as well as the decomposition of carboxylic acids during heat treatment were monitored by using FTIR and UV-visible spectroscopy. On the basis of experimental results, the mechanism of depositing cobalt colloids onto CNFs is also addressed. The as-synthesized Co/CNF catalysts show excellent activity and regioselectivity for the 1-octene hydroformylation.

Journal Article↗
PubMed1989

Hepatic metabolism of colloidal gold-low-density lipoprotein complexes in the rat: evidence for bulk excretion of lysosomal contents into bile.

Rats were treated with 17 alpha-ethinyl estradiol to induce high levels of low-density lipoprotein receptors in hepatocytes. When these rats were given intravenous injections of low-density lipoprotein-colloidal gold complexes, most of the gold (labeled with 195Au) appeared to be taken up by Kupffer cells, as were complexes of colloidal gold with albumin or polyvinylpyrrolidone. However, when these rats were also administered gadolinium chloride, which blocks Kupffer cell activity, most of the low-density lipoprotein-gold (but not gold complexed with albumin or polyvinylpyrrolidone) was taken up into hepatocytes by receptor-mediated endocytosis and concentrated in peribiliary lysosomes, as determined by electron microscopy. Colloidal gold taken up as a complex with low-density lipoprotein was excreted into the feces via the common bile duct at a maximal rate of about 5% daily, 4 to 12 days after injection. Thereafter, the rate of gold excretion fell off until reaching a plateau after 3 weeks. At this late time, most of the colloidal gold was shown by electron microscopy to be in Kupffer cells, whereas earlier (6 days after injection) it was contained mainly in older hepatocytic lysosomes, identified by lipofuscin granules. It is concluded that, in rats, hepatocytic lysosomes empty most of their contents into bile every week or two, apparently by exocytosis.

Animals↗
PubMed1994

Colloid osmotic pressure of steer alpha- and beta-crystallins: possible functional roles for lens crystallin distribution and structural diversity.

This study addresses the general mechanisms whereby the major cytoplasmic proteins from the adult bovine lens contribute both to transparency and maintenance of the refractive index gradient across the lens. Colloid osmotic properties and quaternary structure were measured for alpha- and beta-crystallins isolated from the steer lens, including low-molecular-weight crystallins from the cortex (alpha Le and beta L) and nucleus (alpha Ln) and high-molecular-weight crystallins from the nucleus (alpha H and beta H). In electron microscopic images of rotary-shadowed preparations alpha Le appears as spherical particles 16 nm in diameter, alpha Ln appeared as individual spheres or small aggregates of spherical subunits, alpha H contained large irregular aggregates as large as 180 nm, and both beta L and beta H appeared as elliptical particles of 7-9 nm diameter. Secondary osmometry showed that for all these crystallins colloid osmotic pressure increased monotonically in a non-linear fashion with protein concentration. For the alpha-crystallins, osmotic pressure rose more steeply with concentration for alpha Le than for either alpha Ln or alpha H, so that at 0.3 g ml-1 at 0.1 M ionic strength, the colloid osmotic pressure of alpha Le, alpha Ln and alpha H were approximately 2.6 x 10(5) dyn cm-2, 1.6 x 10(5) dyn cm-2 and 1.0 x 10(5) dyn cm-2, respectively. In a similar manner, osmotic pressure rose more steeply with concentration of beta L than for beta H, so that at 0.3 g ml-1 at 0.1 M ionic strength the colloid osmotic pressures of beta L and beta H were 2.6 x 10(5) dyn cm-2 and 1.1 x 10(5) dyn cm-2, respectively. The osmotic pressure of alpha Le dropped as ionic strength was increased from 0.02 to 0.4 M. For beta L and beta H, osmotic pressure dropped as ionic strength was increased from 0.02 to 0.1 M but was nearly the same at 0.1 M and 0.4 M ionic strength. The data for steer alpha Ln and beta H were similar to previous reports for calf cortical alpha L and beta-crystallins, respectively. The osmotic pressure isotherms for alpha Le, beta L and that previously reported for steer cortical extract were nearly identical, whereas the nuclear crystallins (alpha Ln, alpha H or beta H) generated slightly higher pressures than those previously reported for steer nuclear crystallin extracts. In all cases, osmotic pressure rose more steeply with concentration for the cortical crystallins than for the nuclear crystallins.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1997

Stability of a Nanometric Zirconia Colloidal Dispersion under Compression: Effect of Surface Complexation by Acetylacetone

The stability of a colloidal dispersion of nanometric zirconia particles has been studied during a compression process. Using the osmotic stress method, cycles of compression and reswelling were applied to the dispersion to test the reversibility of the process. Original dispersions are stable in a very limited pH range (0.5-2). At pH 3, the bare particles aggregate irreversibly under compression as checked by osmotic pressure and light and X-ray scattering measurements. To improve the stability, small organic complexing molecules (acetylacetone) were added to the original dispersion. The adsorbed monolayer on the particle surfaces acts as a steric barrier and prevents the two colloids from contacting. As a consequence, the dispersion becomes more compressible and the compression cycle is totally reversible. The experimental data are quantitatively reproduced with a classical theory of statistical mechanics of liquids based on a DLVO-like colloid-colloid potential.

Journal Article↗
PubMed1997

Stability of Dilute Colloidal Silica Suspensions in the Vicinity of the Binodal Curve of the System 2-Butoxyethanol/Water

In the temperature-composition diagram of the system 2-butoxyethanol (abbreviated C4E1)/water, SiO2 [mass fraction of SiO2, y(SiO2) approximately 0.01; volume fraction phi(SiO2) approximately 10(-3)] there exists a flocculation temperature-composition curve running below the binodal curve for x > xc (x, mole fraction of C4E1; xc = 0.0598). The concentration of the colloidal particles is low enough to consider them an "impurity." In the region of the phase diagram bound by the binodal and the flocculation curve the suspension of the colloidal SiO2 particles is unstable and the particles flocculate reversibly. The difference between the temperature of phase separation and the flocculation temperature increases with increasing values of x - xc up to a maximum value of x (xmax). For x > xmax the suspensions are unstable at all temperatures studied. For x < xc the suspension of the SiO2 particles is stable up to the temperature of phase separation of the C4E1/water mixture. The flocculation curve is assumed to reflect the influence of local concentration fluctuations with long range correlations on the stability of the SiO2 suspensions. For x > xc these concentration fluctuations are water rich and interact with the hydrophilic surface of the colloidal SiO2 particles by forming an adsorption layer. This layer is assumed to modify the interparticle potential energy-distance curve and to trigger flocculation. For x < xc the concentration fluctuations are C4E1 rich and no adsorption layer is formed at the hydrophilic surface of the colloidal particles. Copyright 1997Academic Press

Journal Article↗
PubMed1998

Effect of Interparticle Electrostatic Double Layer Interactions on Permeate Flux Decline in Crossflow Membrane Filtration of Colloidal Suspensions: An Experimental Investigation.

A systematic study on the effect of electrostatic double layer interaction on permeate flux decline and deposit cake formation in crossflow membrane filtration of colloidal suspensions is reported. Three monodisperse silica suspensions with diameters of 47, 110, and 310 nm were used as model colloids, and a tubular zirconia membrane with an average pore diameter of 20 nm was used as a model membrane. The magnitude and range of the electrostatic double layer interactions were controlled via changes in solution ionic strength and pH. The coupling between colloidal interactions and hydrodynamic forces was investigated by changing the transmembrane pressure and particle size. The results indicate that the rate of flux decline is strongly dependent on solution ionic strength and, to a much lesser degree, on solution pH (for the investigated pH range 6.1-10.0). Variations in flux decline rate with solution ionic strength are especially significant as the particle size decreases. Particle cake thickness, permeability, and porosity generally increased with a decrease in solution ionic strength for a given particle size. For given physical and chemical conditions, the cake layer porosity increased with decreasing particle size, while cake permeability decreased with decreasing particle size. These trends are consistent with the increased importance of double layer repulsive forces in controlling the cake layer structure as the solution ionic strength and particle size decrease. Pressure relaxation experiments indicated that the particle cake layer is reversible, implying no irreversible deposition (attachment) of silica colloids onto the zirconia membrane surface. Copyright 1998 Academic Press.

Journal Article↗
PubMed1999

Chemical Charge Regulation and Charge Renormalization in Concentrated Colloidal Suspensions.

This article discusses the charging behavior of particles in a colloidal suspension allowing for a simple model reaction at the surface of the colloidal particles that regulates the total number Z(f) of free counterions. This number is to be distinguished from an effective number of charges Z* calculated in the Wigner-Seitz cell model to determine the interaction between the colloidal particles. We discuss the problem in terms of the full free energy of the system. The number of free counterions Z(f) as a function of the structural charge of the colloid is derived from the minimum of this free energy. Our results are compared with experimental data. Copyright 1999 Academic Press.

Journal Article↗
PubMed2000

Diffuse Double-Layer Interaction between Two Identical Spherical Colloidal Particles.

A simple method is given for calculating the potential energy of the diffuse double-layer interaction between two identical spherical colloidal particles in a symmetrical electrolyte solution with the help of Derjaguin's approximation. This method uses accurate analytic expressions for the corresponding interaction energy between two parallel similar plates obtained previously (Colloids Surf. A Physicochem. Eng. Asp. 146, 213 (1999); J. Colloid Interface Sci. 212, 130 (1999)). Agreement with numerical data provided by Honig and Mul (J. Colloid Interface Sci. 36, 258 (1971)) is excellent particularly for small particle separations. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Kinetics of Diffusion-Controlled Adsorption of Colloid Particles and Proteins.

A theoretical model was developed for describing localized adsorption kinetics of proteins and colloid particles at solid/liquid interfaces. In contrast to previous approaches the adsorption and desorption rate constants as well as the surface blocking function were evaluated explicitly without using empirical parameters. It was also predicted that irreversible adsorption kinetics can unequivocally be characterized in terms of the adsorption rate constant k(a) and the maximum (jamming) coverage Theta(mx) known for various particle shapes from previous Monte-Carlo simulations. The dimensionless constant k(a) was shown to be inversely proportional to the concentration of particles which is usually very low for protein and colloid adsorption measurements. From the theoretical model it was also deduced that in this case the asymptotic adsorption law for large dimensionless time tau can be expressed as Theta(mx)-Theta approximately 1/tau(1/(n-1)) (where n=3 for spheres, n=4 for side-on adsorption of spheroids, n=5 for randomly oriented spheroid adsorption). It was also shown that this limiting adsorption regime occurs for proteins at surface coverage Theta(l) very close to the jamming value Theta(mx), becoming therefore difficult to detect due to limited experimental accuracy. These analytical predictions were found to be in agreement with numerical calculations performed by using the finite-difference scheme, valid for an arbitrary range of adsorption time. Moreover, it was demonstrated that these numerical results adequately reflected the experimental results of Johnson and Lenhoff who determined the kinetics of colloid particle adsorption using atomic force microscopy. Previously used approaches assuming that particle adsorption flux is reduced by the factor B(Theta) were found to be inadequate. It was also demonstrated that due to the similarity of underlying parameters the results obtained for colloid systems can be exploited as well-defined reference data for estimating the adsorption kinetics of proteins. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

On the Applicability of DLVO Theory to the Prediction of Clay Colloids Stability.

The stability behavior of Na-montmorillonite colloids has been studied by combining the analysis of their surface charge properties and time-resolved dynamic light scattering experiments. The chemical surface model for several types of clays, including montmorillonite, has to take into account the double surface charge contribution due to their permanent structural charge and to their pH-dependent charge, which is developed at the edge sites, therefore, these stability studies were carried out as a function of both ionic strength and pH. DLVO theory is largely applied for the prediction of the stability of many colloidal systems, including the natural ones. This work shows that the stability behavior of Na-montmorillonite colloids cannot be satisfactorily reproduced by DLVO theory, using the surface parameters experimentally obtained. Particularly, this theory is unable to explain their pH-dependent stability behavior caused by the small charge at the edge sites. Based on these results, a literature review of DLVO stability prediction of clay colloids was performed. It confirmed that this theory is not capable of taking into account the double contribution to the total surface charge and, at the same time, pointed out the main uncertainties related to the appropriate use of the input parameters for the calculation as, for example, the Hamaker constant or the surface potential. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Synthesis of Highly Charged, Monodisperse Polystyrene Colloidal Particles for the Fabrication of Photonic Crystals.

We have developed a series of emulsion polymerization recipes for the synthesis of highly charged, monodisperse polystyrene colloids of diameters between 100-400 nm. These spherical colloidal particles were crosslinked with divinyl benzene and functionalized with 1-allyloxy-2-hydroxypropane sulfonate. These highly charged, monodisperse colloidal particles readily self-assemble into robust three-dimensionally ordered crystalline colloidal arrays (CCAs). These CCAs operate as photonic crystals that Bragg diffract light in the ultraviolet, visible, and infrared regions of the spectrum. Copyright 2000 Academic Press.

Journal Article↗
PubMed2001

Stability of Liquid Films Containing Monodisperse Colloidal Particles.

Thin liquid films containing colloidal particles are considered to be the key structural elements of three-phase foams containing liquid, gas, and colloidal particles. This study is aimed at understanding the stability of such films in the absence of any surfactants. The particles form a layered structure in the film and produce a stepwise thinning in the thin liquid films. We report here for the first time the effects of particle concentration and size on film thickness transition of curved liquid films containing monodispersed colloidal particles. The rate of stepwise film thinning was observed to be high when particle concentration was low and both particle size and film size were large. The phenomenon of stepwise film thinning (i.e., stratification) is rationalized on the basis of diffusion of colloidal particles from the film to the meniscus, i.e., the diffusive osmotic mechanism. There exists a critical film size below which at least one layer of particles always stays in the film (i.e., black spot expansion does not occur). This critical size is dependent upon both particle size and concentration. Also, Monte Carlo simulations of the film show that, at a high particle concentration, better particle in-layer structure develops that increases the energy barrier, inhibiting particle diffusion from the film to the bulk meniscus. Copyright 2001 Academic Press.

Journal Article↗
PubMed2001

Effect of beta-Cyclodextrin on the Photoinduced Charge Transfer in Sodium 1-Anilino-8-naphthalene Sulfate (ANS)/CdS Colloidal System.

The S-center radical (ANS(.)) of sodium 1-anilino-8-naphthalene sulfate (ANS) generated by photoinduced charge transfer in ANS/CdS and ANS/CdS/beta-cyclodextrin(beta-CD) systems has been studied by using spin trapping electron spin resonance techniques, UV-visible spectroscopic methods, and fluorescence spectroscopic methods. It was found that the S-centered radical (ANS(.)) was produced by the charge transfer reaction between the ground state ANS and the positive hole h(+)(CdS) from the valence band of CdS colloids, by the charge transfer from the excited singlet state (1)ANS* to the conduction band of CdS colloids, or by both in the ANS/CdS and ANS/CdS/beta-CD systems. The ESR signal intensity of the spin adduct (5,5'-dimethyl-1-pyrroline-N-oxide (DMPO)-ANS)(.), which is formed from ANS(.) trapped by DMPO, in the latter system is 15 times stronger than that in the former system. The apparent association constants between ANS and CdS colloids in the absence and presence of beta-CD determined from fluorescence quenching experiments are 1097 and 1606 M(-1), respectively. From ESR and fluorescence results, it is estimated that the efficiency of photoinduced charge transfer from ANS to CdS colloids in the ANS/CdS/beta-CD system is 12.5 times that in the ANS/CdS system. Copyright 2001 Academic Press.

Journal Article↗