Colloidal Phase Research Articles

On the structure and stability of novel cationic DPPC liposomes doped with gemini surfactants

A novel formulation of cationic liposomes was studied by mixing dipalmitoylphosphatidylcholine (DPPC) with tetradecyltrimethylammonium bromide gemini surfactants with different alkane spacer groups lengths attached to their ammonium head-groups. The physicochemical characterization of the cationic liposomes was obtained by combining experimental results from differential scanning microcalorimetry (DSC) with molecular dynamic simulations, in order to understand their structural configuration. An adapted Ising model was used to interpret the results in terms of cooperativity of the phase transitions.The gemini surfactants partition into the lipid bilayer of DPPC liposomes, and the induced changes in colloidal stability and phase transition were analyzed in detail. The DPPC liposomes became positively charged upon gemini surfactant partition, showing increased colloidal stability. Our results show significant differences in structural configuration between gemini surfactants with short and long spacer lengths. While gemini with shorter spacers allocate within the lipid bilayer with both headgroups in the same layer, geminis with longer spacers unexpectedly intercalate in the lipid membrane in a particular zig-zag configuration, with each headgroup located at a different side of the bilayer, altering the coupling degree parameters of the membrane’s phase transition.The extraordinary increase of colloidal stability of DPPC liposomes with gemini surfactants at very low molar ratio and the possibility to tune the physicochemical properties of the membrane by control de spacer length of the geminis opens new possibilities for cationic liposomal formulations with potential applications in vaccines, drug/gene delivery or biosensing.

Pharmaceutically active compounds in biotic and abiotic media of rivers receiving urban sewage: Concentrations, bioaccumulation and ecological risk

Pharmaceutically active compounds (PhACs) are recognized as posing health risks to aquatic ecosystems. The occurrence characteristics and ecological effects of 15 PhACs were investigated in the multiphase media of Yangtze River (Nanjing area, China) during wet and dry seasons. All 15 PhACs were detected in the traditionally dissolved phase, suspended particulate matter, sediment and fish, with total concentrations of PhACs (ΣPhACs) of 64.75–366.20 ng/L, 18.50–69.40 ng/g, 3.29–23.30 ng/g and 0.00–176.44 ng/g, respectively. Ibuprofen (IPF), roxithromycin (ROX) and caffeine (CFI) were the dominant PhACs in all of the environmental media. As the main carrier for PhACs, the colloids contributed 8.60%− 77.04% of PhACs in the traditionally dissolved phase, and distribution coefficients (log Kcol=6.38–7.95) of PhACs in colloidal phase were significantly higher than those in SPM and sediment. The bioaccumulation potential of ΣPhACs in the wild fish tissues was generally in order as follows: brain > liver > kidney > gill > blood > intestines > muscle > bile, which was positively correlated with their log Kow. The concentrations of CFI, ROX and IPF in the muscle, gill and liver can be predicted by their log Kow and pollution levels in the blood, and the concentrations of PhACs in the muscle of benthic fish were much higher than those in pelagic fish. The bioaccumulation factors of ROX, fluoxetine and bezafibrate in intestines, brain and blood showed strong enrichment capacity (>5000). In the risk assessment, the acute risk level of PhACs to aquatic organisms decreases gradually with the trophic level, while the trend of chronic risk was the opposite. The chronic mixture risk of PhACs to fish was > 1 at all sampling sites, 59.79% of mixed risk quotient were provided by clofibric acid, diclofenac, erythromycin and ketoconazole. These results indicated that PhAC can cause harmful health effects to sensitive organisms both individually and mixedly.

Magnetic dynamics in suspensions of ferrimagnetic platelets

• First characterization of magnetic dynamics of platelet suspensions using ACS. • Comparison of dynamics in isotropic and nematic phases. • Analysis of ACS spectra by using superposition of multiple Debye-type processes. • Investigation of influence of magneto- and electrostatic interactions. • Exploration of relationship between magnetic dynamics and macroscopic flow. Dense dispersions of ferrimagnetic bariumhexaferrite nanoplatelets form colloidal nematic phases even in the isotropic solvent such as n-butanol. The transition into the nematic phases is marked by developing the long-range orientational and magnetic correlations between the particles. Here we explore the magnetic dynamics in such dispersions in the range of the isotropic and nematic phases. We demonstrate that even in the low concentration isotropic regime, a simple Debye-type mechanism cannot describe the dynamics. Clustering of the particles results in low-frequency contributions.

Coordination–reduction leaching process of ion-adsorption type rare earth ore with ascorbic acid

The magnesium sulfate (MgSO4)–ascorbic acid (Vc) compound leaching technique can extract rare earth elements (REEs) existing in ion-exchangeable phase and colloidal phase from ion-adsorption type rare earth ore through the synergy effect of coordination and reduction, but its reaction process and mechanism remain unclear. In this paper, the coordination–reduction leaching mechanism was analyzed from the perspectives of leaching thermodynamics and kinetics, which provide theoretical guidance for the compound leaching process. In the case of neodymium, about 45% of dissolved neodymium will exist as the complex species of NdVc3(aq) in Nd–Vc–sulfate system. Based on this, it is deduced that the Gibbs free energy of the leaching reaction of ion-exchangeable phase REEs will change to a more negative value through the coordination of REEs cations and Vc anions in the MgSO4 leaching process. In addition, the Eh–pH diagrams of Ce–SO42––H2O and Fe–SO42––H2O together with the dissolution experiments confirm that the added Vc initiates the leaching process of colloidal phase REEs through reduction–dissolution reaction. Through the study of leaching kinetics, the leaching of REEs is controlled by diffusion and chemical reaction in the compound leaching system since colloidal phase REEs are leached. Therefore, the addition of Vc can shift the leaching equilibrium to a more favorable state and accelerate leaching process. The rare earth leaching efficiency of ion–exchangeable phase and colloidal phase can be effectively improved by increasing the reaction temperature, the concentrations of leaching agent and Vc, and the leaching agent acidity.

The influence of buttermilk powder on the stability of emulsion and colloidal phases of homogenized milk

The influence of buttermilk powder on the stability of emulsion and colloidal phases of homogenized milk

Multimedia distribution and ecological risk of bisphenol analogues in the urban rivers and their bioaccumulation in wild fish with different dietary habits

Bisphenol analogues (BPs) have been widely used in industrial production, and caused harmful effects on biological reproduction and development. The occurrence characteristics of six BPs in multi-matrices, including truly dissolved phase, colloids, suspended particulate matter (SPM), sediment and fish samples from urban river were investigated. Bisphenol A (BPA) and bisphenol S (BPS) were the mostly detected in six BPs in the Yangtze River (Nanjing section). The total average concentration of BPs was 393.8 ng/L in truly dissolved phase, 57.4 ng/L in colloids, 255.2 ng/g in SPM and 34.5 ng/g in sediment. The adsorption capacity of SPM and sediment to BPs were weaker than that of colloids. For the spatial variation, the concentrations of BPs in the surface water of the downstream of urban rivers were 1.3–1.6 times higher than that of the upstream, and the BPs concentrations in the sediments downstream of the sewage treatment plant were significantly higher than that in other sites. In wild fish, muscle has a high accumulative potential for BPs, followed by brain and liver tissues, and BPA was the dominant BPs in brain tissues. Furthermore, BPs concentration in muscle of wild fish with different feeding habits was in the following order: filter-feeding fish > omnivorous fish > herbivorous fish, and which was significantly positively correlated with BPs concentration in traditionally dissolved phase and colloidal phase. Meanwhile, BPs concentration in benthic herbivorous fish might be also controlled by the BPs adsorbed in the sediment. Ecological risk assessment was conducted and demonstrated that BPs might pose a moderate risk to fish, a low risk to algae and daphnias. The detected BPs does not pose a health risk to human trough drinking water and eating fish alone.

Diminishing Interfacial Turbulence by Colloid-Polymer Electrolyte to Stabilize Zinc Ion Flux for Deep-Cycling Zn Metal Batteries.

The fluidity of aqueous electrolytes and undesired H2 evolution reaction (HER) can cause severe interfacial turbulence in aqueous Zn metal batteries (ZMBs) at deep cycling with high capacities and current densities, which would further perturb ion flux and aggravate Zn dendrite growth. In this study, a colloid-polymer electrolyte (CPE) with special colloidal phase and suppressed HER is designed to diminish interfacial turbulence and boost deep Zn electrochemistry. Density functional theory calculations confirm that the quantitative migratory barriers of Zn2+ along the transport pathway in CPE demonstrate much smaller fluctuations compared with normal aqueous electrolyte, indicating that CPE can effectively diminish interfacial disturbance. Benefitting from this, the Zn2+ ion flux can be homogenized and deposited evenly on the electrode, which is confirmed by finite element simulation and in situ Raman measurements. Consequently, CPE enables stable operation of Zn//Cu cells even with high capacity (up to 20 mAh cm-2 ) and current density (up to 100mA cm-2 ) and Zn//Na5 V12 O32 full-cell with N/P ratio as low as 1 (i.e., 100%Zn utilization). It is believed that this strategy opens a brand-new avenue based on CPE toward boosting deep-cycling electrochemistry in ZMBs and even other aqueous energy-storage applications.

Mechanistic insight into improving strength and stability of hydrogels via nano-silica

In this investigation, the nanocomposite hydrogels were prepared by hydrophilic nanoscale silica secondary crosslinking hydrolytic polyacrylamide (HPAM) hydrogel to improve its strength and stability performance. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to study the composition and microstructure of nanocomposite hydrogel. In addition, it increases the viscosity of the gel solution by increasing the amount of nano-silica. According to Sydansk coding system, the maximum gel strength of P (HPAM/HMAM/SiO2) hydrogel increased from code “F” to codes “G” and “H”. The stability time of P(HPAM/HMAM/SiO2) hydrogel increased from 30 days to 90 days. The results of molecular dynamics simulation (MDS) and differential scanning calorimetry analyses (DSC) showed that SiO2 increases the interactions between the water molecules and colloidal phase, which is the main reason for improving the stability of the nanocomposite hydrogel. The dehydration rate of hydrogel decreased with the increase of nanoparticle content in terms of the dehydration tests. The dehydration rate of hydrogel increases with the increase of temperature. In addition, the kinetics of all nanocomposite hydrogels dehydration can be described by first-order kinetics at 35 °C, 45 °C, and 55 °C.

Metal-Polymer Heterojunction in Colloidal-Phase Plasmonic Catalysis.

Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal–polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity.

Microscopic structural origin behind slowing down of colloidal phase separation approaching gelation.

The gelation of colloidal particles interacting through a short-range attraction is widely recognized as a consequence of the dynamic arrest of phase separation into colloid-rich and solvent-rich phases. However, the microscopic origin behind the slowing down and dynamic arrest of phase separation remains elusive. In order to access microscopic structural changes through the entire process of gelation in a continuous fashion, we used core-shell fluorescent colloidal particles, laser scanning confocal microscopy, and a unique experimental protocol that allows us to initiate phase separation instantaneously and gently. Combining these enables us to track the trajectories of individual particles seamlessly during the whole phase-separation process from the early stage to the late arresting stage. We reveal that the enhancement of local packing and the resulting formation of locally stable rigid structures slow down the phase-separation process and arrest it to form a gel with an average coordination number of z = 6-7. This result supports a mechanical perspective on the dynamic arrest of sticky-sphere systems based on the microstructure, replacing conventional explanations based on the macroscopic vitrification of the colloid-rich phase. Our findings illuminate the microscopic mechanisms behind the dynamic arrest of colloidal phase separation, the emergence of mechanical rigidity, and the stability of colloidal gels.

Choosing microelements for the immobilization of their colloidal frames on a natural carrier in order to enrich the main food products

The development and implementation of new technologies for enriching the finished product with trace elements is important and relevant. Deviations in the elemental state of the body are found in the vast majority of the adult population of Russia, significantly differing in nature and degree of severity in representatives of different regions and persons divided by profession and occupation. At the same time, it is recognized that in Russia, on average, about two-thirds of adults and three-quarters of children are classified as at risk for hypomicroelementosis, on the other hand, about one-third of the population is more or less susceptible to hypermicroelementosis. The most common deficiency of trace elements such as iron, zincum, copper, chromium, iodine, selenium, cobalt, silicium. The main problem of detecting microelementosis is that the deficiency of essential elements does not have a pronounced clinical picture. To correct the finished formulations of products, it is necessary to take into account the indicators of the level of absorption and the rate of release of these elements, as well as ways of their disposal in the body. One of the most effective ways to introduce essential and conditionally essential elements into formulations is the immobilization of colloidal solutions with a high content of these elements on a polymeric materialor protein carrier, followed by introduction into the composition of the prepared product. The efficiency of using elements such as silver, gold, zinc, cobalt and selenium as a colloidal phase is described. Antagonistic and synergistic interactions of essential elements, their effect on the body, taking into account the indicators of absorption and the rate of their excretion, are described.

Decay pattern of self-healing temperature susceptibility of bitumens at various ageing states

Understanding the evolution law of the self-healing ability of bitumen under actual service environment is conductive to optimizing the design of self-healing bituminous pavement, while the changing temperatures and variety of ageing states complicate this issue. In this study, the decay pattern of self-healing temperature susceptibility of pure bitumen and rock-asphalt (RA) modified bitumen at the simulated ageing states of thermal oxidation and all-weather is analyzed by the dynamic shear rheometer based fatigue-healing-fatigue experiment. Through the thin layer chromatography, differential scanning calorimeter and rheological characterizations, the chemical composition, colloidal stability and macro phase transition (PT) behavior of bitumens with various ageing levels are examined. Results show that the self-healing rate parabola evolution with temperature of bitumen has to do with its frequent PT behaviors. The shift of self-healing curves and the appearance of healing inert temperature zone are the results of the growth of heavy components and decays of colloidal structure and phase structure caused by ageing. Notably, the superposition impacts of temperature and ageing on bitumen phase structures elicit the healing transition phenomena in the viscoelastic zone and viscous flow zone. Moreover, the multi-scale analysis reveals that the decay of self-healing temperature susceptibility with ageing is consistent with the deterioration tendency of the macro PT property, chemical composition and colloidal stability. Especially, all-weather ageing causes more serious impact on the self-healing temperature susceptibility of bitumens than thermal oxidative long-term ageing. RA bitumen with greater ageing resistance undergoes smaller ageing impact on self-healing temperature susceptibility than pure bitumen.

Dermal and transdermal peptide delivery using enhancer molecules and colloidal carrier systems. Part V: Transdermal administration of insulin

In this study, insulin was loaded into non-ionic colloidal carrier systems (CCS) to be used as nano-sized drug delivery systems for transdermal administration. The CCS were characterized for their rheological properties, droplet size and drug loading. Also, the transdermal flux of insulin was estimated using Franz diffusion cells through the epidermis and all the layers of the rats’ skin. The efficacy of the administration of the CCS was assessed in vivo transdermally in rats. Based on the rheological properties and droplet size results, the formulated fluids were identified as nano-sized systems having an aqueous colloidal phase, where the hydrophilic peptide is located. Also, a flux of insulin as high as 0.119 ± 0.016 and 1.328 ± 0.047 iu/cm2.h through the rat’s skin and epidermis, respectively, could be achieved using CCSIn2. Moreover, the monitoring of the blood sugar level over 6.5 h after a single transdermal administration of CCS exhibited a slight decrease. However, a significant drop in the blood sugar level was observed when they were administered once every two days over 10 days. The developed insulin-loaded CCS containing the penetration enhancer DMSO are nano-sized drug delivery systems and can induce a delayed therapeutic effect by repeating the administration.

Effect of alkalinization and ultra-high-pressure homogenization on casein micelles in raw and pasteurized skim milk

Mechanical and physicochemical treatments of milk induce structural modifications of the casein (CN) micelles, affecting their techno-functional properties in dairy processing. Here, we studied the effect of alkalinization and ultra-high-pressure homogenization (UHPH) on CN micelles in raw skim milk (rSM) and pasteurized skim milk (pSM). The pH of both skim milks (approximately 6.7) was adjusted to 8.5 and 10.5 before UHPH at 100, 200, and 300 MPa. The structural changes of the CN micelles during the treatments were assessed using laser diffraction, transmission electron microscopy, and turbidity measurements. Finally, ultracentrifugation (70,000 × g for 1 h at 20°C) was carried out to evaluate the protein's distribution between the supernatant (serum phase) and the pellet (colloidal phase) by gel electrophoresis and protein concentration measurement. Alkalinization of both skim milks induced a significant reduction in turbidity, whereas an increase of the average particle size was observed, the effect being more severe in pSM than rSM. At alkaline pH, more proteins were recovered in the serum phase, which suggested that the CN underwent major rearrangements into nonsedimentable CN forms of various sizes, as confirmed by transmission electron microscopy. The amount of CN found in the serum phase at pH 8.5 also increased with the UHPH pressure. Although UHPH did not influence the average CN micelle size at pH 6.7 and 8.5, a pressure-dependent decrease was observed at pH 10.5 for both skim milks. The structural changes of the CN micelles observed in this study throughout the combination of alkalinization and UHPH could be of interest for developing new dairy ingredients with improved functionality.

Dynamic light scattering analysis of size-selected graphene oxide 2D colloids fractioned via liquid crystal phase separation.

Exfoliated platelets of graphene oxide (GO) can be considered as polydisperse 2D colloids that form nematic colloidal liquid crystal phases in aqueous suspension even at very low concentrations thanks to their extremely high aspect ratios. However, with the rapidly emerging scientific interest in these GO-based liquid crystals, it became clear that the precise analysis and control of the GO sheet size distribution is essential, both for their scientific understanding and for potential applications, e.g., in optoelectronic devices, nanocomposites, or catalysis. In this work, we show that the mean effective (hydrodynamic) GO platelet width can be determined from the translational diffusion coefficient with depolarized dynamic light scattering by using a model for circular, infinitely thin disks. We further studied the phase separation process of biphasic isotropic-nematic GO dispersions and developed a simple fractionation protocol, which can be used to prepare relatively monodisperse fractions of GO sheets with widths ranging from 2.0-12.4 μm. Overall, we expect that the combined application of these relatively simple fractionation and analysis methods will advance the fabrication of well-defined and size-selected GO-based systems.

The Influence of Buttermilk Powder on the Stability of Emulsion and Colloidal Phases of Homogenized Milk

The Influence of Buttermilk Powder on the Stability of Emulsion and Colloidal Phases of Homogenized Milk

Microgels react to force: mechanical properties, syntheses, and force-activated functions.

Microgels are colloidal polymer networks with high molar mass and properties between rigid particles, flexible macromolecules, and micellar aggregates. Their unique stimuli-responsiveness in conjunction with their colloidal phase behavior render them useful for many applications ranging from engineering to biomedicine. In many scenarios either the microgel's mechanical properties or its interactions with mechanical force play an important role. Here, we firstly explain microgel mechanical properties and how these are measured by atomic force microscopy (AFM), then we equip the reader with the synthetic background to understand how specific architectures and chemical functionalities enable these mechanical properties, and eventually we elucidate how the interaction of force with microgels can lead to the activation of latent functionality. Since the interaction of microgels with force is a multiscale and multidisciplinary subject, we introduce and interconnect the different research areas that contribute to the understanding of this emerging field in this Tutorial Review.

POTENSI EKSTRAK KULIT JERUK KUNCI (Citrus microcarpa Bunge) SEBAGAI BIOREDUKTOR DALAM SINTESIS NANOPARTIKEL PERAK

Nowadays silver nanoparticles (AgNPs) synthesized so often by plant extracts as a reductor. The synthesis of AgNPs was carried out by Citrus microcarpa Bunge fruit peel extract a reductor in various extract concentrations (10, 15, and 20%), concentration of AgNO3 solution of 0.15M and temperature of 700C. The presence of AgNPs was determined by color test and the formation of Surface Plasmon Resonance (SPR) using UV-Vis Spectrophotometer while to determine the morphology and size of the nanoparticles using Scanning Electron Microscope (SEM). The results of the analysis showed that AgNPs was formed at colloidal phase with dark brown color with wavelengths of 457.30 nm, 478.90 nm, and 422.80 nm for variation concentration of 10, 15 and 20% with slightly spherical, slightly elongated and jagged morphology with average size of 253.8 nm (10%), 254.2 nm (15%) and 253.9 nm (20%).

Characterization of ozone dosage reduction mechanism in catalytic ozonation process coupled with coagulation and flocculation

• Colloids in the real wastewater were separated by ultrafiltration. • Colloids would consume extra ozone and decreased the O 3 usage. • CF were complementary for CO treating real wastewater. • Polysaccharides was hard to remove either by CO alone and CF-CO. • CF-CO was favorable for aromatic protein II and humic acid-like substances. Characterization of O 3 dosage reduction mechanism in heterogeneous catalytic ozonation (CO) process coupled with coagulation and flocculation (CF) was investigated. Dissolved organics (<0.45 μm) was separated into the truly dissolved and the colloidal phase by ultrafiltration with a 1 K membrane. To meet the emission standard (the COD was reduced from 103.0 mg/L to 50.0 mg/L), when 6.1% of colloidal substances were removed by CF, the effluent COD further decreased 21.1% compared with CO alone. Ozone consumption per unit COD removed by O 3 unit decreased from 0.68 g-O 3 /g-COD (CO alone) to 0.30 g-O 3 /g-COD (CF-CO). Results indicated that colloidal substances significantly affect the CO treatment by increasing the O 3 consumption. Transformation of colloids between molecular weight of 1–3 K and 3–5 K, 5–10 K and 10–30 K were observed. Specific UV absorbance at 254 nm (SUVA 254 ) of the effluent increased by 54.4% after CO alone while decreased by 34.9% after CF-CO, showing that organics with low DOC but high UV 254 accounted for a high level in the raw water. It is hard for CO to remove the polysaccharides of 10–100 K whether the CF pretreatment was applied or not. Fluorescent excitation-emission matrix- fluorescence regional integration analysis showed that the <10 K fractions were removed more in the aromatic protein II, fulvic acid-like substances and humic acid-like substances; <1 K and 30–100 K of soluble microbial by-product-like substances were removed most by both the CO alone and CF-CO. Relationship between the total and individual fluorescence showed that CF-CO was favorable for aromatic protein II and humic acid-like substances. To enhance the removal of the organics by CO, the colloids should be removed by CF pretreatment. For a better energy saving in the practical application, the systemic effects of the concentration of the colloidal substances on the CO was needed for the optimized dosage combination of coagulate and ozone. However, the polysaccharides (10–100 K fractions) was hard to be removed by CO weather the CF pretreatment was applied or not. This is helpful to guide the choice of low-cost advanced oxidation technology according to the character of organic matters.

Computational and Experimental Models of Type III Lipid-Based Formulations of Loratadine Containing Complex Nonionic Surfactants.

Type III lipid-based formulations (LBFs) combine poorly water-soluble drugs with oils, surfactants, and cosolvents to deliver the drugs into the systemic circulation. However, the solubility of the drug can be influenced by the colloidal phases formed in the gastrointestinal tract as the formulation is dispersed and makes contact with bile and other materials present within the GI tract. Thus, an understanding of the phase behavior of LBFs in the gut is critical for designing efficient LBFs. Molecular dynamics (MD) simulation is a powerful tool for the study of colloidal systems. In this study, we modeled the internal structures of five type III LBFs of loratadine containing poly(ethylene oxide) nonionic surfactants polysorbate 80 and polyoxyl hydrogenated castor oil (Kolliphor RH40) using long-timescale MD simulations (0.4-1.7 μs). We also conducted experimental investigations (dilution of formulations with water) including commercial Claritin liquid softgel capsules. The simulations show that LBFs form continuous phase, water-swollen reverse micelles, and bicontinuous and phase-separated systems at different dilutions, which correlate with the experimental observations. This study supports the use of MD simulation as a predictive tool to determine the fate of LBFs composed of medium-chain lipids, polyethylene oxide surfactants, and polymers.