Colloidal Dimensions Research Articles

#4157 A NOVEL STRATEGY TO TARGET V2R IN RENAL CARCINOMA

Abstract Background and Aims The vasopressin V2 receptor (V2R) is a G-protein Coupled Receptor (GPCR) selectively expressed in the kidney. V2R is located at basolateral membrane of principal cells of the distal nephron and thick ascending limb cells and in response to circulating levels of vasopressin (AVP), promotes sodium and water reabsorption. Ectopic expression of V2R plays a role in clear cell renal carcinoma (ccRCC). A recent study shows that tolvaptan, a V2R-antagonist, inhibits cancer growth in an experimental model of ccRCC. However, polyuria remains a serious side effect, limiting the repositioning of this drug in clinical practise. Recent evidences demonstrate that ccRCC have also an up regulation of the transferrin receptor 1 (TfR1). Based on this, we developed Transferrin-conjugated liposomes (Tf-LPs) encapsulating tolvaptan to allow a site-specific delivery to the tumor site, in the attempt to reduce drug side effects. We performed in vitro studies to evaluate the effect of Tf-LPs on cell proliferation and the immunoblotting of cyclin A2, an essential regulator of the cell cycle that participates in the regulation of S phase as well as mitotic entry. Method Liposome formulation and characterization. Liposomes composed of DPPC/DSPEPEG2000/DSPEPEG-MAL were mixed with tolvaptan and prepared by hydration of a thin lipid film, followed by extrusion. Transferrin was conjugated to liposomes at room temperature, overnight. The resulting liposomes were then purified by ultracentrifuge (80000 rpm, 40 min, 4°C). Liposomes were characterized in terms of colloidal dimensions, polydispersity index and surface charge by using dynamic light scattering (DLS) (Zetasizer Nano Z, Malvern, UK). The encapsulation efficiency of Tolvaptan was measured by spectrophotometer (Epoch, Biotek) at the wavelength of 266 nm. In vitro studies. CAKI-1 cells were cultured until the exponentially growing phase. Cells were then incubated with Tf-LPs with or without tolvaptan in growth medium with 0.2%FBS for 24h. Cell viability was assessed by measuring the mitochondrial activity by the 3[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay quantified by spectrophotometry at 570nm. Cell lysate were immunoblotted and Cyclin A2 primary antibody tested as a marker of cell proliferation. Results The liposomes we have generated have an average diameter of about 100 nm, a low polydispersity index (<0.2) and a 50% encapsulation efficiency. MTT assay showed that, compared with control, cells treated with Tf-LPs encapsulating tolvaptan have a reduction in cell proliferation. Interestingly, this reduction starts at lower concentrations and timescales than in a previous study performed with free drug. To further confirm the previous result, we also performed immunoblotting of cyclin A2 which is usually linked to cell proliferation and as such is often found expressed at a high level in human cancers. The expression level of this protein is significantly reduced when cells are treated with Tf-LPs+TOLV while it remains the same in the treatment with Tf-LPs. Conclusion In this study we developed and tested Tf-LPs encapsulating tolvaptan with cytotoxic activity on tumor cells. The preliminary results of this study will be confirmed by subsequent in vivo studies to demonstrate the advantages of this system: site-specific delivery to the tumor site and reduction of drug side effects.

Hydrodynamic interactions between charged and uncharged Brownian colloids at a fluid-fluid interface

HypothesisThe cluster formation and self-assembly of floating colloids at a fluid/fluid interface is a delicate force balance involving deterministic lateral interaction forces, viscous resistance to relative colloid motion along the surface and thermal (Brownian) fluctuations. As the colloid dimensions get smaller, thermal forces and associated drag forces become important and can affect the self assembly into ordered patterns and crystal structures that are the starting point for various materials applications. NumericsLangevin dynamic simulations for particle pairs straddling a liquid–liquid interface with a high viscosity contrast are presented to describe the lateral interfacial assembly of particles in Brownian and non-Brownian dominated regimes. These simulations incorporate capillary attraction, electrostatic repulsion, thermal fluctuations and hydrodynamic interactions (HI) between particles (including the effect of the particle immersion depth). Simulation results are presented for neutrally wetted particles which form a contact angle θ=900 at the interface. FindingsThe simulation results suggest that clustering, fractal growth and particle ordering become favorable outcomes at critically large values of the Pe numbers, while smaller Pe numbers exhibit higher probabilities of final configurations where particle motion remains uncorrelated in space and particle pairs are found to be more widely separated especially upon the introduction of HI.

Nanocrytals-Mediated Oral Drug Delivery: Enhanced Bioavailability of Amiodarone.

The aim of this study was to improve the saturation solubility, dissolution profile and oral bioavailability of amiodarone hydrochloride (AMH), a highly lipophilic drug. Stabilizer (Pluronic F-127)-coated AMH nanocrystals (AMH-NCs) were developed by a combination of antisolvent precipitation and homogenization techniques. The optimized formulation comprised pluronic F-127 and AMH at the concentration of 4% and 2% w/v, respectively. The particle size (PS), zeta potential (ZP) and polydispersity index (PDI) of the optimized formulation was found to be 221 ± 1.2 nm, 35.3 mV and 0.333, respectively. The optimized formulation exhibited a rough surface morphology with particles in colloidal dimensions and a significant reduction in crystallinity of the drug. AMH-NCs showed a marked increase in the saturation solubility as well as rapid dissolution rate when compared with the AMH and marketed product. The stability study displayed that the formulation was stable for 3 months, with no significant change in the PS, ZP and PDI. The in vivo pharmacokinetic study demonstrated the ability of AMH-NCs to significantly (p < 0.05) improve the oral bioavailability (2.1-fold) of AMH in comparison with AMH solution, indicating that the production of AMH-NCs using a combination of antisolvent precipitation and homogenization techniques could enhance the bioavailability of the drug.

Shape Modulation of Plasmonic Nanostructures by Unconventional Lithographic Technique.

Conventional nano-sphere lithography techniques have been extended to the fabrication of highly periodic arrays of sub-wavelength nanoholes in a thin metal film. By combining the dry etching processes of self-assembled monolayers of polystyrene colloids with metal physical deposition, the complete transition from increasing size triangular nanoprism to hexagonally distributed nanoholes array onto thin metal film has been gradually explored. The investigated nano-structured materials exhibit interesting plasmonic properties which can be precisely modulated in a desired optical spectral region. An interesting approach based on optical absorbance measurements has been adopted for rapid and non-invasive inspections of the nano-sphere monolayer after the ion etching process. By enabling an indirect and accurate evaluation of colloid dimensions in a large area, this approach allows the low-cost and reproducible fabrication of plasmonic materials with specifically modulated optical properties suitable for many application in biosensing devices or Raman enhanced effects.

Regulation of nanoporous structure of detonation nanodiamond powders by pressure: SANS study

Nanodiamonds combine unique mechanical, thermodynamic and optical properties of diamond with the peculiarities of colloidal dimensions and wide possibilities of chemical modification of their surface. Of particular practical interest is the presence of a branched porous structure inside detonation nanodiamond agglutinates in powders. Application of moderate (up to 1.5 GPa) static pressures allowed us to separate the contributions to small-angle scattering from micro- and nanosized pores. In continuation of the previous studies, the given research shows the possibilities of controlling the fractal structure of the porous system at the nanoscale by applying static pressure. Thus, the partial pore recombination in the pressure range covered leads to the formation of linear pores, in contrast to the branched system characteristic for the initial industrial samples. This modification can have a wide practical impact associated with the loading of anisotropic additives.

Out-of-Equilibrium Colloidal Assembly Driven by Chemical Reaction Networks.

Transient assembled structures play an indispensable role in a wide variety of processes fundamental to living organisms including cellular transport, cell motility, and proliferation. Typically, the formation of these transient structures is driven by the consumption of molecular fuels via dissipative reaction networks. In these networks, building blocks are converted from inactive precursor states to active (assembling) states by (a set of) irreversible chemical reactions. Since the activated state is intrinsically unstable and can be maintained only in the presence of sufficient fuel, fuel depletion results in the spontaneous disintegration of the formed superstructures. Consequently, the properties and behavior of these assembled structures are governed by the kinetics of fuel consumption rather than by their thermodynamic stability. This fuel dependency endows biological systems with unprecedented spatiotemporal adaptability and inherent self-healing capabilities. Fascinated by these unique material characteristics, coupling the assembly behavior to molecular fuel or light-driven reaction networks was recently implemented in synthetic (supra)molecular systems. In this invited feature article, we discuss recent studies demonstrating that dissipative assembly is not limited to the molecular world but can also be translated to building blocks of colloidal dimensions. We highlight crucial guiding principles for the successful design of dissipative colloidal systems and illustrate these with the current state of the art. Finally, we present our vision on the future of the field and how marrying nonequilibrium self-assembly with the functional properties associated with colloidal building blocks presents a promising route for the development of next-generation materials.

Thermal and microstructural properties of cuticle hydrophobic compounds from four species of Opuntia

Las ceras vegetales son ampliamente usadas en las industrias agroalimentaria, cosmética y farmacéutica. La cera de la cutícula de nopal podría representar una alternativa nueva capaz de satisfacer sus necesidades. El objetivo de la investigación es caracterizar las propiedades térmicas y estructurales de compuestos hidrofóbicos de la cutícula de cuatro especies del género Opuntia [O. robusta Wendl, O. leucotricha DC., O. streptacantha Lem. y O. ficusindica (L.) Mill.]. Las variables determinadas fueron, contenido de compuestos hidrofóbicos por Soxhlet y perfiles de fusión y cristalización de los extractos mediante calorimetría diferencial de barrido. Se observaron microestructuras en la superficie cuticular por medio de microscopía electrónica de barrido, mientras que las características cristalinas de los extractos se observaron a través de microscopía de luz polarizada. Los resultados mostraron que a O. streptacantha se asocian la mayor concentración de compuestos hidrofóbicos (3.97 %) y la temperatura de fusión mayor (78.25 °C). Además, esta especie tiene la mayor cantidad de depósitos de compuestos hidrofóbicos en la superficie del cladodio; los cristales son pequeños de dimensiones coloidales en forma de placas irregulares. Las especies de Opuntia estudiadas, en especial O. streptacantha, contienen compuestos hidrofóbicos con características térmicas similares a las ceras vegetales con valor agregado grande.

Mechanistic understanding regarding the functionality of microcrystalline cellulose and powdered cellulose as pelletization aids in wet-extrusion/spheronization

Powdered cellulose (PC) and microcrystalline cellulose (MCC) show considerable different behavior during wet-extrusion and spheronization. While MCC is an appropriate pelletization aid, PC is not suitable. The differences were explained by either the “molecular-sponge” or the “crystallite-gel” hypothesis. To elucidate the differences in functionality, the effect of several polar solvents on liquid–solid interaction with PC and MCC was investigated. In addition, PC was homogenized via high pressure homogenization to reduce particle size without affecting the degree of polymerization. Mixer torque rheometry (MTR), laser diffraction and texture analysis were used to characterize the behavior of PC and MCC in wet pastes, suspensions and pellets. PC and MCC interacted differently with solvents like dimethyl sulfoxide, dimethylformamide and several glycols during MTR experiments. While PC mainly swells in appropriate solvents, MCC showed a particle size reduction, partly into colloidal dimensions. Solvents that induced liberation of colloidal fibers, also enabled a wet-extrusion/spheronization process. The quantity of colloidal cellulose only had minor effect on the resulting pellet quality. Also, the properties of the used solvent had only minor impact on the pellet size, shape and mechanical stability. PC contained small amounts of colloidal fibers after high pressure homogenization. With this pre-treated PC, wet-extrusion/spheronization process was also possible although the pellet quality is inferior to MCC pellets. Colloidal cellulose fibers have a major impact on the behavior of wet mass and on the feasibility for pellet production via wet-extrusion/spheronization. These insights provide new evidence for the “crystallite-gel” model.

Continuous-flow membrane filtration (CFMF) as a new method to study the narrow size fractions of colloidal dimension

In addition to the cascade filtering method, a new method of continuous-flow gel filtration (CFMF gel filtration) without replacing the filter septum has been developed and tested. The results of narrow size fractions separation from water samples with a high content of colloids (cascade filtration and continuous filtration) and the study of their migration with microelements are presented. An experimental investigation of the joint migration of a large number of elements (up to 40-60) and organic matter in continental waters demonstrates the high prospects for the methods to establish stable geochemical associations of trace elements adsorbed on colloids.

Tunable Colloidal Crystalline Patterns on Flat and Periodically Micropatterned Surfaces as Antireflective Layers and Printable–Erasable Substrates

Abstract2D nonclose‐packed colloidal crystal patterns have received considerable attention in various fields, but it remains a challenge to fabricate patterns and manipulate their geometries regardless of substrate types and structures. Herein, a simple approach is developed for producing nonclose‐packed hydrogel colloidal crystalline patterns on flat and periodically micropatterned substrates by exposing close‐packed colloidal crystal monolayers to salt aqueous solutions. The patterns are achievable on flat surfaces like silicon, glass, graphene, poly(ethylene terephthalate), and poly(dimethyl siloxane) surfaces. Hydrogel colloidal spheres can deform into disk‐like or hemispherical particles on different material substrates. The colloid geometries and dimensions in the patterns are tunable by varying the salt type or concentration. The tunable colloidal crystalline patterns can form on periodically micropatterned substrates, resulting in novel hierarchical crystalline structures. The modification of the method is effective to easily fabricate nonclose‐packed hybrid colloidal crystal patterns where plasmonic nanoparticles are selectively assembled on the hydrogel particle surfaces. These patterned substrates modulate colors, reduce reflectivity of visible to near‐infrared light, and enhance transmittance. The nonclose‐packed colloidal patterns are useful as antireflection coating layers to enhance the solar thermoelectricity efficiencies of flat and micropatterned substrates. The optical tunability of colloidal crystal patterns enables developing colloid crystal‐based printable and erasable substrates.

Formulation and Characterization of a Pharmaceutical Pickering Emulsion

The ability of solid particles to adhere to soft deformable interfaces, for example to the surface of emulsion droplets or bubbles, is currently the subject of renewed interest in material science. On the other hand, Clay minerals are among the most widely used materials in pharmaceutical formulation, because of their properties as excipients and/or their biological activities. These features depend on both their colloidal dimensions and high surface. The phenomenon that solid particles can reside at the interface of droplets, thereby providing them with resistance against coalescence or Ostwald ripening, is known as Pickering stabilization. In this study Algerian bentonite clay is used for this purpose. An evaluation of the antibacterial activity of the emulsion after incorporation of the essential oil of Thymus fontanesii (local plant) also showed a fairly good encapsulation ability.

Partitioning and geochemical fractions of heavy metals from geogenic and anthropogenic sources in various soil particle size fractions

The size of soil particles can significantly affect the enrichment of heavy metals in soil. However, the size effect of soil particles in colloidal dimension on the partitioning and geochemical fractions of heavy metals has been rarely studied. In this study, four soils, polluted by several heavy metals, were collected from Jiangxi (JX) and Hebei (HB) Provinces and Guangxi Zhuang Autonomous Region (GX and GX′) in China, respectively. Five size fractions (>10, 10–1, 1–0.45, 0.45–0.2 and <0.2μm) were separated from the studied soils to investigate the partitioning and geochemical fractions of cadmium (Cd), cadmium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). For JX, GX and GX′ soils, Cr and Ni in JX and GX′ soils and Cr, Ni and Mn in GX soil, as geogenic elements, were comparable with their background values; whereas other heavy metals, as anthropogenic elements, were higher than their background values. For the HB soil that was only polluted by Pb, Cd, Cr, Cu, Mn, Ni and Zn were the geogenic heavy metals. Generally, the contents of most heavy metals in the soil colloids were higher than that in coarse soil particles, and the partitioning tendencies with particle size were not significantly different between geogenic heavy metals and anthropogenic heavy metals. The partitioning of heavy metals in various soil particle size fractions was closely related to the soil particle compositions, such as OM, Fe/Al oxides and clay minerals. For geogenic heavy metals (Cr, Ni), the proportion of the residual fraction, which is imbedded in the silicate crystalline structures of soil particles, was very high, and the geochemical fraction patterns of the various soil particle size fractions were comparable, whereas the bioavailable fraction of anthropogenic heavy metals, such as Cu, Mn, Pb and Zn, decreased with decreasing soil particle size and the proportion of other fractions increased with decreasing size. This result indicates that more anthropogenic heavy metals exist in their stable form in fine soil particles. Correlations between Fe, Al and TOC and the bioavailable fraction of anthropogenic heavy metals were all negative, and most were significant or very significant indicating that high contents of OM and Fe/Al oxides stabilize anthropogenic heavy metals in fine soil particles.

Effect of the size of variable charge soil particles on cadmium accumulation and adsorption

Purpose The size of soil particles strongly affects the accumulation and adsorption of heavy metals which partly controls the co-transport of heavy metals by soil colloids. However, the effect of the size of soil particles on the accumulation and adsorption of heavy metals in the colloidal dimension has seldom been studied. In this study, variable charge soils were selected and separated into five size fractions to elucidate the effect of the size of soil particles on Cd accumulation and adsorption.

The Immobilization of a Transfer Hydrogenation Catalyst on Colloidal Particles

AbstractIn this paper, we report a new synthetic procedure to immobilize a transfer hydrogenation catalyst on the surface of colloidal polystyrene particles. Using supports of colloidal dimensions allows for combining a relatively high surface area for catalyst binding, mobility of the catalyst, and facile recovery by centrifugation or sedimentation. The immobilization procedure relies on the covalent attachment of terpyridine moieties on the particle surface. These immobilized terpyridines are subsequently employed as colloidal ligands, which participate in the formation of an active ruthenium‐based transfer hydrogenation catalyst. The resulting functional colloidal particles successfully catalyze the transfer hydrogenation of acetophenone with 2‐propanol as the hydrogen donor. Thorough analysis of the chemical composition of the colloidal surface led to the determination of the catalyst loading per particle. This enabled us to conduct reference hydrogenations with equal concentrations of the homogeneous transfer hydrogenation catalyst to probe the effect of the immobilization procedure on the catalytic activity. Despite a decrease in transfer hydrogenation activity, full acetophenone conversion is still achievable within 24 h. Preliminary experiments show that the catalytic colloids are recyclable without significant loss of transfer hydrogenation activity.

Redox Active Colloids as Discrete Energy Storage Carriers.

Versatile and readily available battery materials compatible with a range of electrode configurations and cell designs are desirable for renewable energy storage. Here we report a promising class of materials based on redox active colloids (RACs) that are inherently modular in their design and overcome challenges faced by small-molecule organic materials for battery applications, such as crossover and chemical/morphological stability. RACs are cross-linked polymer spheres, synthesized with uniform diameters between 80 and 800 nm, and exhibit reversible redox activity as single particles, as monolayer films, and in the form of flowable dispersions. Viologen-based RACs display reversible cycling, accessing up to 99% of their capacity and 99 ± 1% Coulombic efficiency over 50 cycles by bulk electrolysis owing to efficient, long-distance intraparticle charge transfer. Ferrocene-based RACs paired with viologen-based RACs cycled efficiently in a nonaqueous redox flow battery employing a simple size-selective separator, thus demonstrating a possible application that benefits from their colloidal dimensions. The unprecedented versatility in RAC synthetic and electrochemical design opens new avenues for energy storage.

Interaction between Cationic Micelles and Hyaluronan

Micelles are particles of colloidal dimension and it is known that in an aqueous phase can solubilize water insoluble molecules (hydrophobic biologically active substances) in their inner core. However surfactants may have adverse effects on biological structures. Association of micelles with suitable bioacceptable molecules (e.g. hyaluronan) may lead to enhance their biocompatibility, decrease the nanoparticles cytotoxicity and also to target to the specific receptors in a human body. In this study, results of the research of electrostatic coating of cationic micelle with hyaluronan are reported. The cationic micelle/hyaluronan complexes were studied using turbidimetry and dynamic light scattering method and were evaluated to determine their structure, average size and zeta potential as a function of the amount of the both component in the system. Turbidimetric titration was chosen as indicator of the loss of intensity of transmitted light due to the scattering effect of particles associated from hyaluronan and surfactant in it. Dynamic light scattering measurement provided information about size distribution and zeta potential during mixing of component. Pilot solubilization experiments were performed to evaluation of stability and solubilization ability of the complexes. Results of turbidimetry revealed that aggregates formation (turbidity increasing) depends especially on hyaluronan concentration while surfactant concentration (above critical micelle concentration) affects interaction insignificantly. Dynamic light scattering experiments indicate that hyaluronan molecular weight has insignificant effect on isoelectric point of the systems. It was found that solubilization ability of the complexes is influenced by molecular weight of hyaluronan.

Role of Asphaltenes and Additives on the Viscosity and Microscopic Structure of Heavy Crude Oils

An attempt to understand the microscopic origin of the high viscosity of Brazilian heavy crude oils was made combining macroscopic (rheological measurements) and microscopic [small-angle X-ray scattering (SAXS) measurements] techniques. A clear relationship between the asphaltene content and viscosity was found, while the removal of asphaltene via flocculation led to a large viscosity drop, confirming them as the origin of high viscosity. The SAXS analyses of crude oils confirmed the presence of asphaltene aggregates as fractal-like particles of colloidal dimensions. Afterward, a systematic investigation was performed on the effects of a series of additives and physical treatments on the crude oil viscosity. Physical methods did not cause any significant viscosity drop as well as more than 80 additives tested. SAXS measurements on oil samples containing toluene and heptane indicated little effect on the asphaltene nanoaggregates within the dimensions probed by SAXS, confirming a general mode of action bas...

Effect of oil and co-surfactant on the formation of Solutol HS 15 based colloidal drug carrier by Box–Behnken statistical design

The present study provides an overview to design and optimize self-emulsifying system as colloidal drug carrier for oral delivery of hydrophobic drug using a new surfactant Solutol HS15. The formulation components i.e. surfactant, co-surfactant and oil were investigated to construct a pseudoternary phase diagram. Box–Behnken experimental design was employed as statistical tool to optimize the formulation variables, X1 (Propylene glycol monocaprylate as oil), X2 (Solutol HS15 as surfactant), and X3 (Transcutol HP as cosurfactant). Formulations were assessed for percentage transmittance, droplet size and emulsification efficacy. Transcutol HP was found to be better than other investigated cosurfactants with Solutol HS15, to solubilize the aqueous and the oil phase. Furthermore, the results revealed the significant influence of the surfactant/cosurfactant mass ratio (Km) to form self-emulsifying system of colloidal dimension. Km value 2 was observed to exert a synergistic effect. There was a good correlation between percentage transmittance of diluted self-emulsifying system and droplet size analysis (R2=0.951).

ChemInform Abstract: Porous Inorganic Nanostructures with Colloidal Dimensions: Synthesis and Applications in Electrochemical Energy Devices

AbstractReview: 119 refs.

Porous inorganic nanostructures with colloidal dimensions: synthesis and applications in electrochemical energy devices

Porous inorganic nanostructures with colloidal dimensions can be considered as ideal components of electrochemical devices that operate on renewable energy sources. They combine nanoscale properties with good accessibility, a high number of active sites, short diffusion distances and good processability. Herein, we review some of the liquid-phase routes that lead to the controlled synthesis of these nanostructures in the form of non-hollow, hollow or yolk-shell configurations. From solar and fuel cells to batteries and supercapacitors, we put special emphasis on showing how these sophisticated structures can enhance the efficiency of electrochemical energy devices.