Colloidal dispersions, complexity

Amphotericin B-induced ARF occurs in as many as 40% to 65% of patients treated with the conventional desoxycholate formulation.30 Nephrotoxicity is due to renal arterial vasoconstriction and distal renal tubule cell damage. Risk factors include high doses, treatment for at least 7 days, preexisting kidney dysfunction, and concomitant use of other nephrotoxic drugs.31 Three lipid-based formulations of amphotericin B have been developed in an attempt to decrease the incidence of ARF amphotericin B lipid complex, amphotericin colloidal dispersion, and liposomal amphotericin B. The range of... 

ABLC = Amphotericin B Lipid Complex ABCD = Amphotericin B Colloidal Dispersion L-AMB = Liposomal Amphotericin B... 

Lipid-associated formulations of amphotericin B, liposomal amphotericin B (AmBisome) and amphotericin B lipid complex (Abelcet) have been approved for use in proven cases of candidiasis however, patients with invasive candidiasis have also been treated successfully with amphotericin B colloid dispersion (Amphotec or Amphocil). The lipid-associated formulations are less toxic but as effective as amphotericin B deoxycholate. 

Candida albicans, C. tropicalis, C parapsilosis and resolution of signs and symptoms of infection Remove existing central venous catheters when feasible, plus Amphotericin B IV 0.6 mg/k day or Fluconazole IV/po 6 mg/kg/day or An echinocandin or Amphotericin B IV 0.7 mg/kg/day plus fluconazole IV/po 800 mg/day Patients intolerant or refractory to other therapf Amphotericin B lipid complex IV 5 m k day Liposomal amphotericin B IV 3-5 mg/kg/day Amphotericin B colloid dispersion IV 2-6 mg/k day (continued)... 

Barbehenn R (2001) Roles of peritrophic membranes in protecting herbivorous insects from ingested plant allelochemicals. Arch Insect Biochem Physiol 47 86-99 Barbehenn RV, Martin MM (1998) Formation of insoluble and colloidally dispersed tannic acid complexes in the midgut fluid ofManduca sexta (Lepidoptera Sphingidae) an explanation for the failure of tannic acid to cross the peritrophic envelopes of lepidopteran larvae. Arch Insect Biochem Physiol 39 109-117... 

I I heology is an integral part of life, from decorative paint and movement of volcanic lava to the flow of blood in our veins. This book describes, without the use of complex mathematics, how atoms and molecules interact to control the handling properties of materials ranging from simple ionic crystals through polymers to colloidal dispersions. 

This case study deals with the transfer of a complex, proprietary delivery system into a CMO. The delivery system was developed to better deliver poorly soluble compounds, using Alkermes proprietary Nanocrystal Colloidal Dispersion (NCD ) system. The major challenges associated with the transfer of this technology into an Alkermes production facility (Anon, 2012), included ... 

It is operationally difficult to distinguish between dissolved and colloidally dispersed substances. For example, colloidal metal-ion precipitates occasionally have particle sizes smaller than 100 A, sufficiently small to pass through a membrane filter, and organic substances can exist as a stable colloidal suspension. Information on the types of species encountered under different chemical conditions (type of complexes, their stabilities, rate of formation) is a prerequisite to better understanding of the transformation in properties of toxic chemicals in a water body. 

One-Step Activation Process. In a one-step activation process, the sensitizing and nucleating solutions are combined into one solution. It is assumed that when this solution is made up, it contains various Sn-Pd chloride complexes (24). These complexes may subsequently transform into colloidal particles of metallic Pd or a metallic alloy (Sn/Pd) to form a colloidal dispersion (19,28). This dispersion is unstable. It may be stabilized by addition of an excess of Sn ions. In this case, Pd particles adsorbed on the nonconductor surface are surrounded by Sn ions. The latter must be removed by solubilizing before electroless plating so that the catalytic Pd on the surface will become exposed, freely available, to subsequent plating. An example of such a solubilizing solution is a mixture of fluoroboric and oxalic acids in a dilute solution, or just plain NaOH or HCl. 

Other Methods. Other reductants like hydrazine, sodium metal, etc. can be used for the reduction of metal ions. Decomposition of metal salts or complexes by heat treatment is sometimes used for synthesis of fine particles as well. In this case the valence of metals in the fine particles should be carefully examined. Recently, irradiation of ultrasonic wave was applied to the synthesis of colloidal dispersions of metal fine particles. 

For example, the aggregated structures of the solutions containing polymer-metal complexes and the colloidal dispersions of metal nanoparticles stabilized by polymers have been analyzed quantitatively (64). SAXS analyses of colloidal dispersions of Pi, Rh, and Pt/Rh (1/1) nanoparticles stabilized by PVP have indicated that spatial distributions of metal nanoparticles in colloidal dispersions are different from each other. The superstructure (greater than 10.0 nm in diameter), with average size highly dependent on the metal element employed, is proposed. These superstructures are composed of several fundamental clusters with a diameter of 2.0-4.0 nm, as shown in Figure 9.1.13 for PVP-stabilized Pt nanoparticles. 

Matsuoka, H. and he, N. Small-Angle and Ultra-Small Angle Scattering Study of the Ordered Structure in Polyelectrolyte Solutions and Colloidal Dispersions. Vol. 114, pp. 187-232. Miyasaka, K PVA-Iodine Complexes Formation, Structure and Properties. Vol. 108, pp. 91-130. 

Zeolite crystallization represents one of the most complex structural chemical problems in crystallization phenomena. Formation under conditions of high metastability leads to a dependence of the specific zeolite phase crystallizing on a large number of variables in addition to the classical ones of reactant composition, temperature, and pressure found under equilibrium phase conditions. These variables (e.g., pH, nature of reactant materials, agitation during reaction, time of reaction, etc.) have been enumerated by previous reviewers (1,2, 22). Crystallization of admixtures of several zeolite phases is common. Reactions involved in zeolite crystallization include polymerization-depolymerization, solution-precipitation, nucleation-crystallization, and complex phenomena encountered in aqueous colloidal dispersions. The large number of known and hypo-... 

It is well known that hydrolyzed polyvalent metal ions are more efficient than unhydrolyzed ions in the destabilization of colloidal dispersions. Monomeric hydrolysis species undergo condensation reactions under certain conditions, which lead to the formation of multi- or polynuclear hydroxo complexes. These reactions take place especially in solutions that are oversaturated with respect to the solubility limit of the metal hydroxide. The observed multimeric hydroxo complexes or isopolycations are assumed to be soluble kinetic intermediates in the transition that oversaturated solutions undergo in the course of precipitation of hydrous metal oxides. Previous work by Matijevic, Janauer, and Kerker (7) Fuerstenau, Somasundaran, and Fuerstenau (I) and O Melia and Stumm (12) has shown that isopolycations adsorb at interfaces. Furthermore, it has been observed that species, adsorbed at the surface, destabilize colloidal suspensions at much lower concentrations than ions that are not specifically adsorbed. Ottewill and Watanabe (13) and Somasundaran, Healy, and Fuerstenau (16) have shown that the theory of the diffuse double layer explains the destabilization of dispersions by small concentrations of surfactant ions that have a charge opposite to... 

Humic acid I (symbol H) retained the sorbed material to a slightly greater extent in acid media, but released marginally greater amounts to the complexing agents. The alkaline complexing solutions (i.e., citrate, pyrophosphate, EDTA, DTPA) appeared to dissolve or colloidally disperse the humic acids, but there was a residual > 0.45 pm fraction which retained a measurable amount of the sorbed ion (this observation is consistent with the adsorption/pH trends observed in earlier studies). 

MATIJEVIC, E., The role of chemical complexing in the formation and stability of colloidal dispersions , J. Colloid Interface Sci., 58, 374-389 (1977)... 

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