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PubMedDate not supplied

Experimental evaluation of hepatic functional reserve using 111In colloid for clinical application.

We have postulated that reduced hepatic blood flow is the primary factor responsible for postoperative hepatic insufficiency, and have shown the usefulness of the hepatic blood flow index (KL) estimated by 198Au colloid. However, 198Au colloid has became unavailable due to its intense exposure activity. Therefore, we prepared 111In colloid as a substitute for 198Au colloid to evaluate hepatic functional reserve. In the present study, a 111In colloid was administered to rats to investigate the possibility of clinical application. First, liver cirrhosis was induced in rats using CCl4 Changes in KL and hepatic tissue blood flow were measured by hydrogen gas clearance (HL) after CCl4 injection, and was shown to correlates well with it. The correlation between KL and HL, together with normal and cirrhotic liver, was significant (r = 0.83, p < 0.01) Second, reticuloendothelial function was modulated with Zymosan A (stimulation) and Silica (suppression). The KL value remained unchanged in spite of the addition of an activator or suppressor to the reticuloendothelial system. Third, 30% and 70% hepatectomy models were studied according to the method of Higgins-Anderson. KL and HL was measured before and 1, 3 and 7 days after hepatectomy. KL and HL after 30% and 70% hepatectomy showed similar changes. These results indicate that the clearance of 111In colloid can be used clinically as an index of the hepatic blood flow.

Animals↗
PubMed2001

Size-selective electrochemical preparation of surfactant-stabilized Pd-, Ni- and Pt/Pd colloids.

A detailed study concerning the size-selective electrochemical preparation of R4N+Br- -stabilized palladium colloids is presented. Such colloids are readily accessible using a simple electrolysis cell in which the sacrificial anode is a commercially available Pd sheet, the surfactant serving as the electrolyte and stabilizer. It is shown that such parameters as solvent polarity, current density, charge flow, distance between electrodes and temperature can be used to control the size of the Pd nanoparticles in the range 1.2-5 nm. Characterization of the Pd colloids has been performed using transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and X-ray powder diffractometry (XRD) evaluated by Debye-function-analysis (DFA). Possible mechanisms of particle growth are discussed. Experiments directed towards the size-selective electrochemical fabrication of (n-C6H13)4N+Br- -stabilized nickel colloids are likewise described. Finally, a new strategy for preparing bimetallic colloids (e.g., Pt/Pd nanoparticles) electrochemically is presented, based on the use of a preformed colloid (e.g., (n-C8H17)4N+Br- -stabilized Pt particles) and a sacrificial anode (e.g., Pd sheet).

Journal Article↗
PubMed2006

Characterization and catalytic-hydrogenation behavior of SiO2-embedded nanoscopic Pd, Au, and Pd-Au alloy colloids.

Colloids embedded in a silica sol-gel matrix were prepared by using fully alloyed Pd-Au colloids, and pure Pd and Au colloids stabilized with tetraalkylammonium bromide following a modified sol-gel procedure with tetrahydrofuran (THF) as the solvent. Tetraethoxysilicate (TEOS) was used as the precursor for the silica support. The molar composition of the sol was TEOS/THF/H2O/HCl = 1:3.5:4:0.05 for the bimetallic Pd-Au and TEOS/THF/H2O/HCl = 1:4.5:4:0.02 for Pd and Au monometallic systems. After refluxing, the colloid was added as a 4.5 wt % solution in THF for Pd-Au, 10.2 wt % solution in THF for Pd and 8.4 wt % solution in THF for Au at room temperature. The gelation was carried out with vigorous stirring (4 days) under an Ar atmosphere. Following these procedures, bimetallic Pd-Au-SiO2 catalysts with 0.6 and 1 wt % metal, and monometallic Pd- and Au-SiO2 catalysts with 1 wt % metal were prepared. These materials were further treated following four different routes: 1) by simple drying, 2) in which the dried catalysts were calcined in air at 723 K and then reduced at the same temperature, 3) in which they were directly reduced in hydrogen at 723 K, and 4) in which the surfactant was extracted using an ethanol-heptane azeotropic mixture. The catalysts were characterized by nitrogen adsorption-desorption isotherms at 77 K, H2 chemisorption measurements, solid-state 1H, 13C, 29Si-CP/MAS-NMR spectroscopy, powder X-ray diffraction (XRD), small angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and 197Au Mössbauer spectroscopy. The physical characterization by a combination of these techniques has shown that the size and the structural characteristics of the Pd-Au colloid precursor are preserved when embedded in an SiO2 matrix. Catalytic tests were carried out in selective hydrogenation of 3-hexyn-1-ol, cinnamaldehyde, and styrene. These data showed evidence that alloying Pd with Au in bimetallic colloids leads to enhanced activity and most importantly to improved selectivity. Also, the combination of the two metals resulted in catalysts that were very stable against poisoning, as was evidenced for the hydrogenation of styrene in the presence of thiophene.

Journal Article↗
PubMed1996

The Osmotic Pressure of Electrostatically Stabilized Colloidal Dispersions

A mathematical model for predicting the osmotic pressure of electrostatically stabilized colloids has been developed. The model is based on detailed descriptions of the colloidal interactions within an electrostatically stabilized dispersion. Electrostatic interactions are accounted for by a Wigner-Seitz cell approach including a numerical solution of the nonlinear Poisson-Boltzmann equation. London-van der Waals forces are calculated using a computationally efficient means of approximating screened, retarded Lifshitz-Hamaker constants. Configurational entropy effects are calculated using an equation of state giving excellent agreement with molecular dynamic data. These descriptions of colloidal interactions are used to develop an a priori model, with no adjustable parameters, that allows quantitative prediction of the osmotic pressure of colloidal dispersions as a function of zeta potential (and hence pH), colloid size, ionic strength, and colloid concentration. The model shows good agreement with literature experimental data for the osmotic pressure of the protein bovine serum albumin (BSA). A charge regulation model for the BSA surface has also been developed from knowledge of the amino acid groups giving rise to the protein charge. A comparison of zeta potentials calculated from this model with experimentally determined values for dilute BSA dispersions shows good agreement for a wide range of conditions. The charge regulation model has also been incorporated into the osmotic pressure prediction, resulting in excellent agreement between theory and experiment.

Journal Article↗
PubMed1998

Interaction between Colloids in Network Forming Solution.

The effective interaction between colloids in a solvent of hard spheres, which can polymerize with the formation of cross-like molecular clusters, is studied on the basis of the solution of the associative Percus-Yevick/Ornstein-Zernike equation for spatial correlations in an infinitely dilute solution. It is found that at low solvent density and low temperature, the effective intermolecular potential between the colloidal particles is attractive, thus facilitating a phase separation or precipitation of the colloids. A depletion of the local solvent density around the colloidal particle is observed. If the solvent consists of extended associative complexes, compared with hard spheres, the correlation between the colloid particles are of longer range and barrier for flocculation shifts to the larger separations. The effect of size ratio of the colloid spheres and of solvent on the potential of mean force is also discussed. Copyright 1998 Academic Press.

Journal Article↗
PubMed2000

Analysis of Contact Interactions between a Rough Deformable Colloid and a Smooth Substrate.

A model was developed for the effect of van der Waals interactions between a rough, deformable, spherical colloid and a flat, smooth, hard surface in contact. The model demonstrates the significant effect of colloid roughness on removal force. Small changes in colloid roughness produce large changes in the predicted removal force. Several authors attribute discrepancies in the observed interaction force between particles and surfaces to colloid roughness, and our model supports their hypotheses. Experimental data documenting the force required to remove colloids of polystyrene latex from silica substrates in aqueous solution were collected during AFM studies of this system. When colloid roughness exists, as is the case in this work, our model bounds the observed removal force. The predicted range of removal forces is in better quantitative agreement with our removal force data than are forces predicted by classical DLVO theory. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Colloidal Platinum Nanoparticles Stabilized by Vinyl Polymers with Amide Side Chains: Dispersion Stability and Catalytic Activity in Aqueous Electrolyte Solutions.

Colloidal platinum nanoparticles were prepared by ethanol reduction of PtCl(6)(2-) in the presence of poly(N-vinylformamide) (PNVF), poly(N-vinylacetamide) (PNVA), or poly(N-vinylisobuty-ramide) (PNVIBA). The effects of molecular weight and molar ratio of monomeric unit/Pt on the particle sizes and size distributions were characterized by transmission electron microscopy and UV-visible spectroscopy. The flocculation behavior of the polymer-stabilized colloidal Pt nanoparticles was studied with respect to the effects of temperature, addition of inorganic salts, and composition of the mixed solvents. The dispersion stability of the platinum colloids stabilized by poly(N-isopropylacrylamide) (PNIPAAm) and poly(vinylpyrrolidone) (PVP) was also examined. The sequence of polymer-stabilized platinum colloids in increasing order of dispersion stability was found to be PNIPAAm-Pt<PNVIBA-Pt<PVP-Pt<PNVA-Pt<PNVF-Pt. Anions of the added salts played an essential role in reducing the dispersion stability and sulfates were more efficient at promoting flocculation than chlorides. The PNVF-Pt colloids did not show any critical flocculation point (temperature or salt concentration) under employed conditions, owing to the strongly hydrophilic nature of PNVF chains. The catalytic activity of PNVF-Pt colloids for hydrogenation of allyl alcohol in 0.8 M Na(2)SO(4) solution was the same as that in pure water. Copyright 2000 Academic Press.

Journal Article↗
PubMed2002

Effect of TiO2 colloids on the fluorescence behavior of two cyanine dyes.

The photophysical properties of two typical cyanine dyes [3,3'-diethyl-9-methyl-thiacarbocyanine iodide (dye A) and anhydro-3,3'-disulfopropyl-5,5'-diphenyl-9-ethyloxacarbocyanine hydroxide (dye B)] in the absence and presence of TiO(2) colloids have been investigated by UV-visible spectroscopy, (1)H-NMR spectroscopy, fluorescence spectroscopy, fluorescence lifetime measurements, and ESR measurements. It was found from the absorption spectra and NMR results that there are two isomers in the ground state of these dyes. Steady-state fluorescence spectra show that the fluorescence intensities of dye A and dye B are enhanced and quenched by TiO(2) colloids, respectively. Time-resolved fluorescence lifetime measurements indicate that the lifetimes of dye A and dye B in the presence of TiO(2) colloids are longer and shorter than those obtained in the absence of TiO(2) colloids, respectively. ESR measurements demonstrate that the electron transfer efficiency from (1)dye B* to the conduction band of TiO(2) is much larger than that from (1)dye A* to the conduction band of TiO(2). The different fluorescence behavior of dye A and dye B can be intepreted in terms of whether phi(Tr,nr)(0)-phi(Tr,nr) (the reduction of the quantum yield for radiationless transition in the excited singlet state (1)dye* caused by the TiO(2) colloids) is larger or smaller than phi(ET) (the quantum yield of electron transfer from (1)dye* to the conduction band of TiO(2) colloids).

Journal Article↗
PubMed2003

[Haemodynamic effects following preoperative hypervolemic haemodilution with hypertonic hyperoncotic colloid solutions in coronary artery bypass graft surgery].

OBJECTIVE: Using hyperoncotic colloids as volume replacement to provide haemodynamic stability appears to be a suitable approach to diminish fluid overload and subsequent interstitial edema during cardiac surgery. The aim of the present study was to investigate for the first time the haemodynamic effects following preoperative haemodilution with different hypertonic hyperoncotic colloid solutions in patients undergoing coronary artery bypass grafting. METHODS: A total of 43 patients with normal left ventricular ejection fraction, undergoing elective coronary artery bypass grafting received preoperatively after induction of anaesthesia according to randomisation the following solutions: 1: 750 ml/m(2) (body surface area) NaCl 0.9% ( n=10, control group, NACL), 2: 250 ml/m(2) 10% HES 200/0.5 plus 400 ml/m(2) NaCl 0.9% ( n=9, HES), 3: 250 ml/m(2) 10% dextran 40 plus 300 ml/m(2) NaCl 0.9% ( n=8, DEX), 4: 150 ml/m(2) hypertonic NaCl (7.2%) 10% HES 200/0.5 (n=8, HYPER-HES), 5: 150 ml/m(2) hypertonic NaCl (7.2%) 10% dextran 60 ( n=8, HYPER-DEX). Haemodynamic measurements were performed immediately before and 15 min after haemodilution and up to 60 min after termination of extracorporeal circulation in 10 min intervals. Fluid balances were calculated separately, during the time period of surgery, postoperatively up to 24 h after termination of surgery, and during the course of extracorporeal circulation. RESULTS: After haemodilution with colloid solutions, a marked increase was observed in all patients and with HYPER-HES and HYPER-DEX a statistically significant increase in cardiac index (CI: +38%, +54%), stroke volume index (SVI: +42%, +40%), and oxygen availability (DO2: +34%; +41%), respectively, was observed during the pre-bypass period. At the same time right and left ventricular filling pressures increased slightly in all patients but these changes did not differ among the treatment groups. Heart rate and mean arterial pressure remained almost unchanged in all groups. The amount of crystalloid solutions required by the patients during surgery was markedly decreased with HES and DEX and significantly decreased with HYPER-HES and HYPER-DEX (1,013+/-341 ml/m(2), 1,096+/-234 ml/m(2)) compared to the control group NACL (1629+/-426 ml/m(2)). Serum sodium concentrations increased with HYPER-HES and HYPER-DEX to maximal values of 150+/-3 mmol/l and 149+/-4 mmol/l, respectively (baseline 141+/-3 mmol/l, 141+/-1 mmol/l) CONCLUSIONS: Compared to isotonic saline solution, preoperative volume replacement with hyperoncotic colloids improves haemodynamic conditions during the pre-bypass period in patients with normal left ventricular function undergoing coronary artery bypass grafting. Additionally intraoperative crystalloid solution requirements are reduced. The volume saving effects are increased with administration of hyperoncotic colloids in a preparation with hypertonic saline solution, whereas the choice of the colloid, either hydroxyethyl starch or dextran seems to be of minor importance.

Adult↗
PubMed1978

Relationship between colloid osmotic pressure and pulmonary artery wedge pressure in patients with acute cardiorespiratory failure.

Close relationships between progressive respiratory failure, roentgenographic signs of pulmonary opacification and decreases in the difference between colloid osmotic pressure of plasma and the pulmonary artery wedge pressure (colloid-hydrosatic pressure gradient) were demonstrated in 49 critically ill patients with multisystem failure, in patients in shock. The potential importance of this relationship is underscored by the observation that fatal progression of pulmonary edema was related to a critical reduction in the colloid-hydrostatic pressure gradient to levels of less than 0 mm Hg. More often, reduction in colloid osmotic pressure rather than increases in left ventricular filling pressure (pulmonary artery wedge pressure) accounted for the decline in colloid-hydrostatic pressure gradient. Routine measurement of colloid osmotic pressure, preferably in conjunction with pulmonary artery wedge pressure, is likely to improve understanding of the mechanisms of acute pulmonary edema.

Acute Disease↗
PubMed2003

Size distribution of colloidal silica in sodium silicate solutions investigated by dynamic light scattering and viscosity measurements.

Three types of aqueous sodium silicate solutions characterized by molar SiO(2):Na(2)O ratios of 2.2, 3.3, and 3.9 were investigated by dynamic light scattering and viscosity measurements. The solutions were prepared by diluting concentrated commercial products to SiO(2) content between 0.5 and 15 wt%. Dynamic light scattering (DLS) was used for the investigation of size distributions of colloids immediately after dilution. At least three size classes of colloidal particles were detected, which exist in parallel in the solutions. The respective radii are 0.4 to 0.6 nm, 2.5 to 13 nm, and 75 to 85 nm. The larger colloids dominate the mass distribution, whereas the smaller colloids control the surface area of the colloidal fraction. Material properties such as pH, viscosity, refractive index, and density were measured as a function of dilution. The evaluation of the viscosity data indicated that the colloids have a lower density than dense amorphous silica. Aging effects could be suppressed by measuring within 1 h after dilution.

Journal Article↗
PubMed2004

Dense colloid transport in a bifurcating fracture.

In this work, the transport of dense colloids through a water-saturated, bifurcating fracture is investigated using a constant spatial step particle tracking technique. The size of the constituents of a colloid plume is an important factor affecting the partitioning of dense colloids at the bifurcation. While neutrally buoyant colloids partition between daughter fractures in proportion to flow rates, dense colloids will preferentially exit fractures that are gravitationally downgradient, notwithstanding that the majority of the interstitial fluid may flow through the upper fracture. Comparison of the partitioning ratio between daughter fractures with the ratios of characteristic settling, diffusion, and advection time reveal that these parameters control how colloids behave at fracture bifurcations.

Journal Article↗
PubMed2005

Fabrication of hollow colloidal crystal cylinders and their inverted polymeric replicas.

We fabricated colloidal crystals on a fiber by a dip-coating method. The self-assembly of monodisperse colloidal particles was affected by the curvature of the fiber (the reciprocal of the fiber radius). As the fiber became smaller in diameter, fewer layers of the colloidal spheres were coated for a given lift-up speed. The hollow colloidal crystal cylinders were used as a template for creating macroporous structure having three-dimensionally interconnected air cavities. Specifically, the polymer precursor was infiltrated into the colloidal crystal template and the macroporous polymer structures were obtained after the selective etching of colloidal particles.

Journal Article↗
PubMed2005

Influence of various monovalent cations and calcium ion on the colloidal fouling potential.

The influence of various monovalent cations and of divalent calcium ions on colloidal fouling strength was investigated quantitatively on a bench-scale ultrafiltration device. A higher colloidal fouling potential (k) was consistently observed with lithium chloride compared to the same ionic strengths of chlorides of other monovalent cations (Na+, K+, and Cs+). This observation was attributed to the formation of an impervious layer around the colloidal particle by lithium ions that prevented the repulsive forces due to the interaction of the silica hairs formed on the particles in the presence of water. The impact of the divalent calcium ion on the fouling potential was more complex. The fouling potential first increased with calcium ion concentration and then decreased. The maximum value of fouling potential occurred at the ionic strength corresponding to the critical coagulation concentration, which decreased with increasing colloid concentration. The colloidal fouling potential was well correlated by a bilinear relationship with colloid concentration and ionic strength for all salts tested under the critical coagulation concentration.

Journal Article↗
PubMed2004

Studies on solution and solution-cast film of polyaniline colloids prepared in the absence and presence of ultrasonic irradiation.

Spectroscopic and voltammetric features for the solution and solution-cast film of polyaniline (PANI) colloids prepared in the absence and presence of ultrasonic irradiation were examined. Significant differences in the color and absorption spectra between the solution of colloids prepared in the absence and presence of irradiation were observed. Effects of ambient atmosphere on the solution of colloids were also studied. A gradual decay in the absorption at approximately 365 nm was occurred upon ageing the solution in air for the colloid prepared under ultrasonic irradiation. PANI film, cast from its colloidal solution, exhibited excellent electroactivity. The films thus cast were applied to electrode modification to control electrochemical reaction. Clear voltammetric response was observed on the electrode modified with the colloid prepared in the presence of ultrasonic irradiation.

Journal Article↗
PubMed1975

Serum colloidal osmotic pressure in the development of kwashiorkor and in recovery: its relationship to albumin and globulin concentrations and oedema.

1. Serum colloidal osmotic pressure was measured in children 'at risk' to kwashiorkor, in other with frank signs of the disease and during recovery. Simultaneous estimations of serum albumin and globulin concentrations and assessments of the extent of oedema were also made. 2. During the development of kwashiorkor, serum colloidal osmotic pressure did not decrease significantly until albumin concentration was 25-1--27-5 g/l. Above 30-0 g/1, colloidal osmotic pressure was maintained at normal levels during which time a significant reciprocal relationship existed between albumin and globulin concentrations. These findings provide support for suggestions that there may be on oncotic regulation of albumin synthesis. 3. Low albumin concentrations were mainly responsible for the low colloidal osmotic pressures found in children with kwashiorkor and in agreement and previous findings the threshold for the formation of oncotic oedema was found to be about 2-35--2-65 kN/m2. 4. Values for colloidal osmotic pressure calculated from serum albumin and gobulin concentrations using emprical formulas did not agree well with measured values and no constant correction factor suitable over the whole range of albumin concentrations found in rural Ugandan children could be devised. In many hypoalbuminaemic children ony direct measurement of serum colloidal pressure will indicate the true extent of risk to an episode of oedema.

Child↗
PubMed2002

Gram-scale synthesis of monodisperse gold colloids by the solvated metal atom dispersion method and digestive ripening and their organization into two- and three-dimensional structures.

We describe a synthetic procedure for preparation of large quantities of monodisperse thiol-stabilized gold colloids in toluene solution. The method is based on the solvated metal atom dispersion technique (SMAD), which is very suitable for preparation of large amounts of metal colloidal solutions, as well as of metal sulfide, metal oxide, and other types of dispersed compounds in different solvents. A combination of two different solvents like acetone and toluene is used for the preparation of the gold colloids. The necessity of initially carrying out the SMAD reaction in acetone comes from its high degree of solvation of gold particles. Acetone acts as a preliminary stabilizing agent. After its removal from the system, the particles are stabilized by dodecanethiol molecules, which enable their very good dispersion in toluene solution. A digestive ripening procedure is carried out with the gold-toluene colloid, and for this purpose pure toluene as solvent is necessary. This has a dramatic effect on the narrowing of particle size distribution and almost monodisperse colloids are obtained (some discussion of the probable mechanism of this remarkable digestive ripening step is given). These colloidal solutions have a great tendency to organize in two- and three-dimensional structures (nanocrystal superlattices, NCSs). We believe that this procedure provides a real opportunity to synthesize large amounts of gold nanocrystals as well as NCSs.

Journal Article↗
PubMed2005

Photoinduced deformation of amphiphilic azo polymer colloidal spheres.

Photoinduced shape deformation of colloidal spheres made of an amphiphilic azo polymer has been demonstrated in this work. The polymer contains the donor-and-acceptor-type azobenzene chromophores and can form uniform colloidal spheres by dropwise adding water into its THF solution. When the colloidal spheres obtained were exposed to the interfering p-polarized Ar+ laser beams (150 mW/cm2), the colloidal spheres changed to prolates (i.e., "rugby-balls"), "spindles", and finally "rods", depending on the irradiation times. The elongated direction of the spheres was observed to be the same as the polarization direction of the laser beam. The average major-to-minor ratio of the ellipsoids could be easily adjusted by controlling the irradiation time. The deformation effect observed in this work can offer a new way to prepare nonspherical colloids from colloidal spheres and will shed new light on the correlation between the photodriven shape deformation and photoinduced surface relief gratings for the same type of polymers.

Journal Article↗