Precipitation In Aqueous Solution Research Articles

Nanoliposome C6-Ceramide Increases the Anti-tumor Immune Response and Slows Growth of Liver Tumors in Mice

BACKGROUND & AIMSCeramide, a sphingolipid metabolite, affects T-cell signaling, induces apoptosis of cancer cells, and slows tumor growth in mice. However, it has not been used as a chemotherapeutic agent because of its cell impermeability and precipitation in aqueous solution. We developed a nanoliposome-loaded C6-ceremide (LipC6) to overcome this limitation and investigated its effects in mice with liver tumors.METHODSImmune competent C57BL/6 mice received intraperitoneal injections of carbon tetrachlo-ride and intra-splenic injections of oncogenic hepatocytes. As a result, tumors resembling human hepatocellular carcinomas developed in a fibrotic liver setting. After tumors formed, mice were given an injection of LipC6 or vehicle via tail vein every other day for 2 weeks. This was followed by administration, also via tail vein, of tumor antigen-specific (TAS) CD8+ T cells isolated from the spleens of line 416 mice, and subsequent immunization by intraperitoneal injection of tumor antigen-expressing B6/WT-19 cells. Tumor growth was monitored with magnetic resonance imaging. Tumor apoptosis, proliferation, and AKT expression were analyzed using immunohistochemistry and immunoblots. Cytokine production, phenotype, and function of TAS CD8+ T cells and tumor-associated macrophages (TAMs) were studied with flow cytometry, real-time polymerase chain reaction (PCR), and ELISA. Reactive oxygen species (ROS) in TAMs and bone marrow-derived macrophages, induced by colony stimulating factor 2 (GMCSF or CSF2) or colony stimulating factor 1 (MCSF or CSF1), were detected using a luminescent assay.RESULTSInjection of LipC6 slowed tumor growth by reducing tumor cell proliferation and phosphorylation of AKT, and increasing tumor cell apoptosis, compared with vehicle. Tumors grew more slowly in mice given the combination of LipC6 injection and TAS CD8+ T cells followed by immunization compared with mice given vehicle, LipC6, the T cells, or immunization alone. LipC6 injection also reduced numbers of TAMs and their production of ROS. LipC6 induced TAMs to differentiate into an M1 phenotype, which reduced immune suppression and increased activity of CD8+ T cells. These results were validated by experiments with bone marrow-derived macrophages induced by GMCSF or MCSF.CONCLUSIONSIn mice with liver tumors, injection of LipC6 reduces the number of TAMs and the ability of TAMs to suppress the anti-tumor immune response. LipC6 also increases the anti-tumor effects of TAS CD8+ T cells. LipC6 might therefore increase the efficacy of immune therapy in patients with hepatocellular carcinoma.

Size dependent optical and antibacterial properties of Ag3PO4 synthesized by facile precipitation and colloidal approach in aqueous solution

Present study reports the synthesis of Ag3PO4 nano/mircoparticles by facile precipitation and colloidal synthesis approach in aqueous solution. Importantly, the presented approach does not require complicated instruments, difficult processes, and harsh conditions such as high temperature and high pressure. The obtained samples were characterized using SEM with EDS, XRD, TEM with HR-TEM and SAED, and FTIR. Their optical properties were studied using UV–vis diffusive reflectance spectra. Size dependent antibacterial activity towards Gram-positive (S. aureus) and Gram-negative (E. coli, K. pneumoniae and P. aeruginosa) bacteria. Experimental results showed that the antibacterial performances of nanoparticles obtained by mixing 0.01M of each reactant (colloidal synthesis approach) were found to be much higher than that of other formulation under identical conditions.

Deciphering pore-level precipitation mechanisms

Mineral precipitation and dissolution in aqueous solutions has a significant effect on solute transport and structural properties of porous media. The understanding of the involved physical mechanisms, which cover a large range of spatial and temporal scales, plays a key role in several geochemical and industrial processes. Here, by coupling pore scale reactive transport simulations with classical nucleation theory, we demonstrate how the interplay between homogeneous and heterogeneous precipitation kinetics along with the non-linear dependence on solute concentration affects the evolution of the system. Such phenomena are usually neglected in pure macroscopic modelling. Comprehensive parametric analysis and comparison with laboratory experiments confirm that incorporation of detailed microscale physical processes in the models is compulsory. This sheds light on the inherent coupling mechanisms and bridges the gap between atomistic processes and macroscopic observations.

Dual Alkali Solvent System for CO2 Capture from Flue Gas.

A novel two-aqueous-phase CO2 capture system, namely the dual alkali solvent (DAS) system, has been developed. Unlike traditional solvent-based CO2 capture systems in which the same solvent is used for both CO2 absorption and stripping, the solvent of the DAS system consists of two aqueous phases. The upper phase, which contains an organic alkali 1-(2-hydroxyethyl) piperazine (HEP), is used for CO2 absorption. The lower phase, which consists of a mixture of K2CO3/KHCO3 aqueous solution and KHCO3 precipitate, is used for CO2 stripping. Only a certain kind of amine (such as HEP) is able to ensure the phase separation, satisfactory absorption efficiency, effective CO2 transfer from the upper phase to the lower phase, and regeneration of the upper phase. In the meantime, due to the presence of K2CO3/KHCO3 in the lower phase, HEP in the upper phase is capable of being regenerated from its sulfite/sulfate heat stable salt, which enables the simultaneous absorption of CO2 and SO2/SO3 from the flue gas. Preliminary experiments and simulations indicate that the implementation of the DAS system can lead to 24.0% stripping energy savings compared to the Econamine process, without significantly lowering the CO2 absorption efficiency (∼90%).

Mixed biopolymer nanocomplexes conferred physicochemical stability and sustained release behavior to introduced curcumin

Beta-lactoglobulin (BLG)-sodium alginate (ALG) electrostatic nanocomplexes were utilized to encapsulate and deliver curcumin in clear acidic media. Relative viscosity measurements confirmed that ALG wrapping around the globular BLG molecules occurred in the aqueous biopolymer mixture upon acidification. Curcumin was efficiently entrapped within developed green delivery systems. The encapsulation efficiency (EE) of curcumin was around 98%. The carriers were efficiently able to retain the curcumin inside over time. The physical stability of hydrophobic curcumin toward precipitation in aqueous solution was significantly improved after introduction into nanostructures. Moreover, nanocomplexes conferred considerable protection to curcumin against heat-induced degradation. At the end of 15-day storage at 45 °C, the amounts of curcumin loaded in nanocomplexes were significantly (p < 0.05) larger than those loaded in blank samples. Non-significant changes in the particle size after high temperature short time (HTST) heat treatment indicated that the presence of polysaccharide shell around the protein core increased the thermal stability of BLG at acidic conditions. No release occurred in simulated fasting and non-fasting gastric conditions. However, a sustained release behavior (78.5% during 12 h) was observed in simulated intestinal fluid.

Low temperature synthesis of Co3O4 and (Co1−xMnx)3O4 spinels nanoparticles

The (Co1−xMnx)3O4 solid solution have been synthesized in water at 60°C by soda addition to a cationic solution. XRD patterns show that spinel oxide has been obtained except for pure cobalt composition which exhibits also the presence of hydroxide and oxy-hydroxide. Therefore, to reach this composition, a different synthesis route has been developed: the cationic solution is added to the soda and for the first time Co3O4 nanoparticles have been synthesized by a direct precipitation in aqueous solution at low temperature. For each composition, the particles are well crystallized and exhibit a size close to 50nm. Each particle is composed by several crystallographic domains of about 10nm. The cubic to tetragonal transition reported in the literature for x=0.46 is observed in between x=0.33 and x=0.50. Raman spectra show that substitution of Co by Mn, in the cubic phase, introduces a random high disorder. In the tetragonal phase, occupation of the octahedral site remains a random occupation, while the tetrahedral site seems to be preferentially occupied by Co ions. All these results show that the precipitation is a simple, fast and safe process to synthesize pure phase of (Co1−xMnx)3O4 spinel solid solution in aqueous media at low temperature.

Polymorphism and polytypism in zinc aliphatic carboxylate: The complex case of Zn(C11H21O2)2

Crystallographic study was performed on the zinc undecanoate Zn(C11H21O2)2 by X-ray diffraction. Three polymorphs A, B and C were identified. The structures of A and B were solved from X-ray diffraction on platelets like single crystals obtained by crystallization in methanol. Polymorph A: SG=P21/c, a=54.411(4)Å, b=4.666(4)Å, c=9.2231(8)Å, β=92.54(7)°, V=2341(2)Å3, Z=4; polymorph B: SG=Cc, a=53.451(2)Å, b=4.707(1)Å, c=9.178(1)Å, β=91.53(7)°, V=2308(2)Å3, Z=4. Polymorph C has been detected in powder samples obtained by precipitation in aqueous solution. Its structure was solved from X-ray synchrotron diffraction data: SG=Pna21, a=9.3386(6)Å, b=4.7393(3)Å, c=54.646(5)Å, V=2418.5(3)Å3 and Z=4. The three polymorphs have the usual layered structures encountered in zinc linear carboxylates series with Zn atoms in tetrahedral O-coordination. The forms A and C have the same building blocks but differ by their stacking. Two adjacent layers are 180° rotated around the short and the long axis in A and C respectively. The form B presents conformational disorder leading to modification of the preceding layers. In these form, the layers maintain the same orientation along the stacking direction.

Controlling the Photocorrosion of Zinc Sulfide Nanoparticles in Water by Doping with Chloride and Cobalt Ions.

Photodegradation under UV light irradiation is a major drawback in photocatalytic applications of sulfide semiconductors. ZnS nanoparticles were doped with very low amounts of chloride or cobalt ions in the ppm range and codoped with chloride and cobalt ions during their synthesis by precipitation in aqueous solution followed by calcination. The high-temperature wurtzite phase annealed at 800 °C had a high susceptibility to UV irradiation in water, while the low-temperature zincblende phase annealed at 400 °C was found to be stable. Chlorine doping increased the rate of photocorrosion in water, whereas cobalt doping led to a stabilization of the ZnS nanoparticles. Based on photochemical and spectroscopic investigations applying UV/vis, X-ray photoelectron, and photoluminescence spectroscopy, the increased susceptibility of Cl-doped ZnS is ascribed to a higher number of surface point defects, whereas the stabilization by Co2+ is caused by additional recombination pathways for the charge carriers in the bulk, thus avoiding photocorrosion processes at the surface. Additional doping of Cl-doped ZnS with cobalt ions was found to counteract the detrimental effect of the chloride ions efficiently.

Visual spectroscopy method to evaluate entrapment efficiency of electrostatically precipitated proteins in combination with octenyl succinic anhydrate (OSA)-modified polysaccharides

The objective of this study was to evaluate the application of visible spectroscopy to discern the entrapment capability of a hydrophobic compound (trans-cinnamaldehyde) by electrostatic precipitation in aqueous solution of pure whey proteins or in combination with octenyl succinic anhydrate (OSA)-modified polysaccharides. Particles were obtained by electrostatic precipitation of complex structures formed at different weight ratios (1:0–1:10) of proteins and OSA-modified polysaccharides. Trans-cinnamaldehyde 99% (TCNN) was selected as a model hydrophobic bioactive compound, due to its use as an antimicrobial. The entrapment capability of TCNN by the complex structures was evaluated by measuring the remaining TCNN on the supernatant (TCNNsuptt) after centrifugation of the complexes that were electrostatically precipitated at 23 °C. The insoluble complexes were effectively monitored through absorbance (Abs) measurements at 600 nm with a spectrophotometer. Absorbance values corresponded well with total sugar interaction-adsorption of OSA-modified polysaccharides at the electrostatic precipitation of proteins, which in turn corresponded to the entrapment efficiency, based on the amount of protein precipitated. These results validate the use of spectrophotometric measurements as a rapid, toxic-free, and easy, comparative method to evaluate the adsorption interaction between protein and other amphiphilic molecules. In addition, electrostatic precipitation of protein alone or in combination with OSA-modified polysaccharides is a feasible method to entrap volatile and thermolabile compounds.

Effect of Nanoscale Confinement on the Crystallization of Potassium Ferrocyanide

Many crystallization processes of great significance in nature and technology occur in small volumes rather than in bulk solution. This article describes an investigation into the effects of nanoscale confinement on the crystallization of the inorganic compound potassium ferrocyanide, K4Fe(CN)6 (KFC). Selected for study due to its high solubility, rich polymorphism, and interesting physical properties, K4Fe(CN)6 was precipitated within controlled pore glasses (CPG) with pore diameters of 8, 48, and 362 nm. Remarkable effects were seen, such that although anhydrous potassium ferrocyanide was never observed on precipitation in bulk aqueous solution, it was the first phase to crystallize within the CPGs and was present for at least 1 day in all three pore sizes. Slow transformation to the metastable tetragonal polymorph of the trihydrate K4Fe(CN)6·3H2O (KFCT) then occurred, where this polymorph was stable for a month in 8 nm pores. Finally, conversion to the thermodynamically stable monoclinic polymorph of K...

Precipitation mechanism of amorphous silica nanoparticles: A simulation approach

Hypothesis: Despite its importance in numerous industrial and natural processes, many unsolved questions remain regarding the mechanism of silica precipitation in aqueous solutions: order of the reaction, role of silica oligomers, existence of an induction time and characteristics of the particle population. This may be traced back, in past models, to the lack of account of the first stages of nucleation, size dependence of the growth law, and full particle population.Computational method: A microscopic description of the nucleation and growth of amorphous silica nanoparticles is achieved which reproduces a large set of experimental measurements, under various thermodynamic conditions. The time evolution of the solution supersaturation and of the precipitate characteristics is established.Findings: A growth law of order 6 allows reproducing experimental results, without being correlated to the presence of silica oligomers in the aqueous solution. The saturation plateaus are shown not to be due to an induction period. The characteristics of the particle population are more complex than assumed by simple precipitation models (Johnson–Mehl–Avrami-Kolmogorov or Chronomal models) and strongly depend on how supersaturation is reached. Such a microscopic approach thus proves to be well suited to elucidate the mechanism of nanoparticle formation in natural and industrial contexts.

Size-controlled synthesis of granular polyphosphate nanoparticles at physiologic salt concentrations for blood clotting.

Size-controlled granular polyphosphate (PolyP) nanoparticles were synthesized by precipitation in aqueous solutions containing physiological concentrations of calcium and magnesium. We demonstrate using dynamic light scattering (DLS) that the solubility is correlated inversely with PolyP chain length, with very long chain PolyP (PolyP1000+, more than 1000 repeating units) normally found in prokaryotes precipitating much more robustly than shorter chains like those found in human platelet dense granules (PolyP80, range 76-84 repeating units). It is believed that the precipitation of PolyP is a reversible process involving calcium coordination to phosphate monomers in the polymer chain. The particles are stable in aqueous buffer and albumin suspensions on time scales roughly equivalent to catastrophic bleeding events. Transmission electron microscopy images demonstrate that the PolyP nanoparticles are spherical and uniformly electron dense, with a particle diameter of 200-250 nm, closely resembling the content of acidocalcisomes. X-ray elemental analysis further reveals that the P/Ca ratio is 67:32. The granular nanoparticles also manifest promising procoagulant effects, as measured by in vitro clotting tests assaying contact pathway activity.

The disproportionation of [Ni(tacn)]2+ in Ni2+ and [Ni(tacn)2]2+ crystallographically demonstrated (tacn = 1,4,7-triazacyclononane).

From an EtOH/H2O solution, 0.3 M each of Ni(2+) and cyclic triamine tacn (2; tacn = 1,4,7-triazacyclononane), after 10 min refluxing and cooling at room temperature, copious and comparable amounts of blue crystals (containing the complex [Ni(tacn)(H2O)3](2+)) and pink crystals (containing in the same cell both [Ni(H2O)6](2+) and [Ni(tacn)2](2+)) precipitated. This unusual behaviour is ascribed to the fact that at the refluxing temperature the three species are present at the equilibrium in similar concentrations, which are frozen on cooling, due to the inertness of the macrocyclic complexes [Ni(tacn)(H2O)3](2+) and [Ni(tacn)2](2+).

Ionic‐Liquid‐Functionalized Polyoxometalates for Heterogeneously Catalyzing the Aerobic Oxidation of Benzene to Phenol: Raising Efficacy through Specific Design

AbstractBy combining nitrile‐tethered pyridinium‐based ionic liquid dication with the polyoxometalate anion of Keggin H5PMo10V2O40 (PMoV2) through precipitation in aqueous solution, an organic–inorganic hybrid catalyst 1,1′‐(butane‐1,4‐diyl)‐bis(3‐cyanopyridine)–PMoV2 was prepared for heterogeneous hydroxylation of benzene to phenol with O2 and ascorbic acid as the oxidant and reductant, respectively. The hybrid catalyst not only gave the high phenol yield of 13.0 % under the optimized reaction conditions, but also exhibited high potential for reusability. The catalyst and its analogue samples were characterized by elemental analysis, Fourier transform infrared spectroscopy, electron spin resonance spectroscopy, X‐ray diffraction, scanning electron microscopy, and nitrogen adsorption–desorption analysis. The structure–activity relationship is discussed according to the characterization and density functional theory calculation results.

Morphology of CuFe2O4/CNT composites prepared by precipitation

In this study, the effect of carbon nanotube (CNT) supports on the morphology and structural of copper ferrite nanoparticles has been investigated. The synthesis of CuFe2O4 nanoparticles has been done through direct precipitation in aqueous solution with CNT content. The morphology of the synthesised samples has been studied by the use of scanning electron microscopy; structural properties have been investigated through X-ray diffraction spectrometer. Fourier transform infrared spectroscopy apparatus was used to identify the functional groups on the surface of CNTs. The findings showed that the presence of CNT support in nanocomposite powder, the size of CuFe2O4 significantly decreased and the powder morphology changed from agglomerate state to nanorodes.

Hydrogen production by photocatalytic ethanol reforming using Eu- and S-doped anatase

Abstract Pure or S- and Eu-doped nanocrystalline titania has been synthesized by precipitation in aqueous solutions of TiSO4 in the presence of urea. Spherical aggregates were formed made of nanoparticles of size ranging between 33 and 46 nm. The samples were calcined at 700–750 °C and this allowed for making materials with high degree of crystallinity. Doping preserved the anatase phase and allowed for a substantial value of specific surface in spite of the high temperature annealing. The photocatalytic capacity of doped and undoped samples was monitored by photocatalytic alcohol reforming and hydrogen production. Only samples co-doped with Pt nanoparticles produced hydrogen. Doping with either S, Eu or both gave much more efficient photocatalysts than the undoped samples. The superiority of doped samples is assigned to a larger specific surface and to the impeding of electron–hole recombination in that case.

Structure of sodium sulphate aqueous solution/quartz interface: a molecular dynamics simulation

The molecular dynamics simulation was used to investigate the aqueous sodium sulphate solutions within quartz nanopores. Simulation was conducted for 13 ns to obtain the equilibrium distribution of water molecules, sulphate and sodium ions (Na+ and ) within the pores. The results clearly show an adsorption of sodium sulphate solution onto the quartz surface. However, Na+ shows a stronger attachment to the fully hydroxylated surface than due to size effects. The majority of Na+ ions appear within the primary and secondary water adsorption sites from the quartz surface. A special orientation of water molecules has been found in these layers, where one of the O–H bonds was parallel to the normal direction of the quartz surface. These observations illustrate the effect of quartz surface on the diffusion and precipitation of aqueous salt solutions under confinement, thus providing the mechanism of salt destruction on mural paintings.

Ionic and electronic conductivity of 3 mol% Fe2O3-substituted cubic yttria-stabilized ZrO2 (YSZ) and scandia-stabilized ZrO2 (ScSZ)

Abstract Scandia-stabilized zirconia (ScSZ) electrolytes exhibit the highest ionic conductivity among all ZrO 2 -based materials. However, a phase transition occurs around 650 °C from cubic to rhombohedral β-phase which is unique for Sc-stabilized zirconia and leads to reduced conductivity. The occurrence of this β-phase can be suppressed by co-doping ScSZ. The aims of this study are to confirm the influence of a small amount of Fe 2 O 3 doping on both the stabilization of the cubic phase and the decrease of the sintering temperature and to investigate the influence of this co-doping on the ionic and electronic conductivity of ScSZ. Therefore (ZrO 2 ) 0.90 –(Sc 2 O 3 ) 0.07 –(Fe 2 O 3 ) 0.03 powder has been prepared by precipitation in aqueous solution and sintered at 1380 °C to obtain ceramic. The electrical properties (ionic and electronic conductivities) of this ceramic are compared to the ones of Fe-doped YSZ.

Pure and Fe3+-doped ZnS quantum dots as novel and efficient nanophotocatalysts: Synthesis, characterization and use for decolorization of Victoria blue R

Ultra-small pure and iron-doped ZnS quantum dots (QDs) were synthesized using a simple and fast procedure based on chemical precipitation in aqueous solution. The QD size was controlled by adding 2-mercaptoethanol as a capping agent at room temperature. The QDs were characterized by X-ray diffraction (XRD), UV-Vis absorbance, transmission electron microscopy and atomic absorption spectroscopy. XRD analysis revealed that the iron-doped nanoparticles were crystalline with a cubic zinc blende structure and a crystallite size of 17±2Å. The undoped and Fe3+-doped ZnS QDs were used as nanophotocatalysts for decolorization of Victoria blue R as a cationic dye under UV irradiation. The effects of the photocatalyst dose, mole fraction of the dopant, irradiation time, and sample pH on the dye decolorization efficiency were studied.

Influence of the pH and ageing time on the acid aluminum phosphate synthesized by precipitation

Acid aluminum phosphates have been obtained by precipitation in aqueous solution. The influence of two important synthesis parameters, pH and ageing time, has been studied and important differences in the final materials have been observed. All precipitated phosphates present acid character regardless of pH and ageing time. An increase of phosphate acidity, crystallinity and size is favored with decreasing pH. Moreover, at synthesis pH below 4.8, increase of these characteristics have been also observed with increasing ageing time. In addition, the growth mechanism of phosphate particles has been established as a mechanism based on aggregation of globular primary nanoparticles regardless of the size and morphology of the final powders.