Variation Of Zeta Potential Research Articles

Roles of methyl orange in preparation of emulsions stabilized by layered double hydroxide particles

The roles of a fluorescent dye, methyl orange (MO) in the emulsions stabilized by layered double hydroxide (LDH) particles have been investigated in detail. The hydrophilic LDH particles are rendered partially hydrophobic by the in situ surface modification with MO, leading to the enhanced stability of emulsions. The variation of contact angle, zeta potential and emulsion stability demonstrates the amphiphile-like behaviors of MO. Exploiting the fluorescence of MO, we have shown in situ microscopic images of MO-modified particle adsorption onto droplet surface using confocal fluorescence microscopy. Furthermore, the adsorption of MO-modified LDH on liquid droplet surface has also been exploited to produce hollow colloidosomes, the morphology of which has been observed with SEM.

Evaluation of the Role of Surfactant on the Surface Characterisation of Coal

The surfaces of three China coals varying widely in coal type(Baode,Xiangshan,Jincheng) have been modified by adsorption of three surfactants( Sodium dodecyl sulfate,Polyethoxylated fatty alcohols,Alkyl phenol gather oxygen vinyl ether).The impact about coals of the surfactant has been explored by correlating three chemical characterisation techniques.Changes in coal surface hydrophobicity were assessed using contact angle measurements at the coal/water interface.The largest variation in zeta potential resulting from addition of surfactants was seen for the higher rank coals.The Specific surface area decreased when surfactants were present.

낙동강 원수를 대상으로 Al염계 및 Fe염계 응집제를 이용한 고도응집의 적용

Enhanced coagulation is best available technologies to treat NOM in water to produce clean drinking water. In this research, the comparison experiments between conventional coagulation (CC) and enhanced coagulation (EC) using 4 type coa- gulants i.e., ferric chloride, aluminium sulphate (alum), poly aluminium sulphate organic magnesium (PSOM) and poly aluminium chloride (PACl) were performed in terms of surrogate parameters such as dissolved organic carbon (DOC), trihalomethane formation potential (THMFP), haloacetic acid formation potential (HAAFP) and zeta potential variation in order to find out the most effective coagulant and conditions to fit Nakdong River water. When applied to EC process, the turbidity removal efficiency did not increased gradually compared to the CC process when adding coagulants. Furthermore, the removal efficiency of turbidity became decreased much more as coagulants were added increasingly whereas the removal efficiency of DOC, THMFP and HAAFP became increased by 13~18%, 9~18% and 9~18% respectively compared to the CC process. The characteristics of turbidity removal showed relatively high removal efficiency considering the pH variation in entire pH range when using FeCl3 and PACl. Additionally, in case of alum and PSOM steady removal efficiency was shown between pH 5 and pH 8. In terms of DOC surrogate the coagulants including 4 type coagulants indicated high removal efficiency between pH 5 and pH 7. The removal efficiency of dissolved organic matter (DOM) in EC between less than 1 kDa and more than 10 kDa augmented by 11~21% and 16% respectively compared to the CC process. The removal efficiency of hydrophobic and hydrophilic organic matter proved to be increased by 27~38% and 11~15% respectively. In conclusion, the most effective coagulant relating to EC for Nakdong River water was proved to be FeCl3 followed by PSOM, PAC and alum in order.

Low-cost monofilament mesh filter used in membrane bioreactor process: Filtration characteristics and resistance analysis

This work investigates filtration performance of mesh filter bioreactor for synthetic municipal wastewater treatment. Critical flux is measured by flux stepping method and the effect of aeration rate on the critical flux is investigated. The long term monitoring of trans-filter pressure evolution at sub and super-critical fluxes is performed. The analysis of resistance is achieved by determination of resistances and microscopic observation of bio-cake. Cake resistance values vary from 78% to 92% of total filtration resistance for sub and super-critical fluxes. The effect of variations of specific aeration demands (SAD m: 0.5–6 m 3/m 2 h) on suspended solid of effluent, turbidity of filtrate, filtration resistance, and zeta potential of biomass is evaluated. The results show that filtrate quality is decreased when the aeration rate increases. It is attributed to stable formation of dynamic membrane. A rather clear filtrate, less than 18 NTU of turbidity, is obtained for SAD m 0.5 m 3/m 2 h. The results also show that the total filtration resistance of the sub-critical flux significantly decreases with increasing aeration intensity until SAD m 2 m 3/m 2 h and thereafter slightly decreases. It is also shown that the variations of zeta potential of biomass with aeration rate highly correspond to the alterations of filtration resistance.

Preparation and characterisation of 5-fluorouracil containing PLGA nanospheres coated with chitosan, for drug delivery

The aim of this study was to design a new Drug Delivery System (DDS) based on poly (lactide–co–glycolide) (PLGA) biodegradable nanospheres (NS) coated with Chitosan (CTS), in order to prolong its residence time and to deliver the nanoparticles more specifically to cancer cells. We have tried three methods of incorporation of Chitosan in the nanoparticles, but only one was efficient. The first method is named entanglement of chains, the second method is known as single adsorption and, in the third, we prior linked covalently Chitosan to the polymer and then prepared the nanoparticles. After selected the best method, it was monitored the stability following the temporal variation of diameter, polydispersity and zeta potential of particles prepared using different percentages of CTS and pH values, using a pre–optimised formulation of 5–fluorouracil containing PLGA NS.

Biophysical characterization of polymyxin b interaction with LPS aggregates and membrane model systems

Antibiotic resistance is an increasingly severe health problem. Antimicrobial peptides (AMPs) are being developed in order to overcome this problem, due lower bacterial resistance. Polymyxin B is an AMP with bactericidal effect on Gram-negative bacteria due to its high affinity for lipopolysaccharide (LPS). The objective of this work was to unravel the polymyxin B mechanisms of LPS neutralization and bactericidal activity. Using dynamic light scattering, it was observed that polymyxin B induces LPS aggregation in a concentration-dependent manner. The peptide increases the surface charge of LPS and membrane model systems, as revealed by zeta-potential measurements. The higher zeta-potential variations were detected in the presence of the negatively charged POPG membranes. This higher interaction with negatively charged membranes, made of POPG, was followed at higher peptide concentration by membrane permeabilization. Also, for zwitterionic POPC membranes a higher membrane leakage was detected. The peptide promotion of LPS aggregation may be related with the clearance of LPS from the bloodstream, eventually by facilitating macrophage phagocytosis and/ or blocking the binding of LPS to its receptor. Our data indicate that polymyxin B mechanism of action at the molecular level involves a first step of electrostatic approach toward LPS; then, it may be internalized and bind to the bacterial phosphatidylglycerol-rich membrane leaflets, inducing leakage at higher peptide concentrations.

Liposomes as a Model for the Biological Membrane: Studies on Daunorubicin Bilayer Interaction

In this study the interaction of the antitumoral drug daunorubicin with egg phosphatidylcholine (EPC) liposomes, used as a cell membrane model, was quantified by determination of the partition coefficient (K(p)). The liposome/aqueous-phase K(p) of daunorubicin was determined by derivative spectrophotometry and measurement of the zeta-potential. Mathematical models were used to fit the experimental data, enabling determination of K(p). In the partition of daunorubicin within the membrane both superficial electrostatic and inner hydrophobic interactions seem to be involved. The results are affected by the two types of interaction since spectrophotometry measures mainly hydrophobic interactions, while zeta-potential is affected by both interpenetration of amphiphilic charged molecules in the bilayer and superficial electrostatic interaction. Moreover, the degree of the partition of daunorubicin with the membrane changes with the drug concentration, due mainly to saturation factors. Derivative spectrophotometry and zeta-potential variation results, together with the broad range of concentrations studied, revealed the different types of interactions involved. The mathematical formalism applied also allowed quantification of the number of lipid molecules associated with one drug molecule.

Electroosmotic flows with simultaneous spatio-temporal modulations in zeta potential: cases of thick electrical double layers beyond the Debye Hückel limit

We devise a mathematical model for analyzing the effects of spatio-temporal perturbations in zeta potential on electroosmotic transport in narrow fluidic confinements, considering thick electrical double layer limits. The spatial perturbations in zeta potential may be attributed to surface charge patterning, either designed or manifested as a natural artifact of the surface inhomogeneities. The time-dependent variations in zeta potential, as considered in this work, may stem from the temporal perturbations in the bulk ionic concentrations in the end-channel reservoirs or ‘wells’. Overcoming the simplifications routinely employed in the literature, we develop here an improved analytical formalism, without imposing any constraints on the magnitude of the zeta potential. Using these solutions, we highlight the possibilities of obtaining designed rotationalities in the flow structure with simultaneous spatial variations in the zeta potential and temporal variations in the well concentrations. We show that such combinations of spatial and temporal variations, in effect, render the flow system to be capable of shedding vortex structures that are not otherwise obtainable with spatial variations in zeta potential alone.

Folate Receptor-Targeted Aggregation-Enhanced Near-IR Emitting Silica Nanoprobe for One-Photon in Vivo and Two-Photon ex Vivo Fluorescence Bioimaging

A two-photon absorbing (2PA) and aggregation-enhanced near-infrared (NIR) emitting pyran derivative, encapsulated in and stabilized by silica nanoparticles (SiNPs), is reported as a nanoprobe for two-photon fluorescence microscopy (2PFM) bioimaging that overcomes the fluorescence quenching associated with high chromophore loading. The new SiNP probe exhibited aggregate-enhanced emission producing nearly twice as strong a signal as the unaggregated dye, a 3-fold increase in two-photon absorption relative to the DFP in solution, and approximately 4-fold increase in photostability. The surface of the nanoparticles was functionalized with a folic acid (FA) derivative for folate-mediated delivery of the nanoprobe for 2PFM bioimaging. Surface modification of SiNPs with the FA derivative was supported by zeta potential variation and (1)H NMR spectral characterization of the SiNPs as a function of surface modification. In vitro studies using HeLa cells expressing a folate receptor (FR) indicated specific cellular uptake of the functionalized nanoparticles. The nanoprobe was demonstrated for FR-targeted one-photon in vivo imaging of HeLa tumor xenograft in mice upon intravenous injection of the probe. The FR-targeting nanoprobe not only exhibited highly selective tumor targeting but also readily extravasated from tumor vessels, penetrated into the tumor parenchyma, and was internalized by the tumor cells. Two-photon fluorescence microscopy bioimaging provided three-dimensional (3D) cellular-level resolution imaging up to 350 μm deep in the HeLa tumor.

Electrophoretic deposition of chitosan/45S5 Bioglass ® composite coatings for orthopaedic applications

This article presents experimental results on the electrophoretic deposition (EPD) of bioresorbable chitosan/45S5 Bioglass ® composite coatings for orthopaedic implants based on the Taguchi design of experiments (DOE) approach. The influence of EPD parameters including Bioglass ® concentration, electric voltage and deposition time on deposition yield was studied by an orthogonal Taguchi array of L 18 type. Multivariate analysis of variance (MANOVA) and regression analysis based on the partial least-square method were used to identify the significant factors affecting the deposition yield and its stability during constant-voltage EPD. The coatings were characterised by high resolution scanning electron microscope (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). It is shown that the co-deposition of polymer/Bioglass ® system is very sensitive to the concentration of Bioglass ® particles. The addition of Bioglass ® to the chitosan suspension alters the deposition rate due to variation of pH, suspension conductivity, and zeta potential. For low Bioglass ® concentrations, co-deposition of the chitosan and the bioactive glass particles occurs while at the higher concentrations massive deposition of the bioactive glass particles controls the deposition yield. The optimum condition for a high deposition rate with low standard deviation and homogeneous microstructure is achieved when an almost equal concentrations of chitosan and Bioglass ® is utilized. The validity of the approach is shown by confirmation experiments at the predicted optimal condition, and the mechanism of electrophoretic co-deposition of the polymer/glass system is discussed.

3-D Simulations of Electroosmotic Sample Migration in Microchannels: Effects of Surface and Solution Property Variations

This article reports a 3-D numerical study on the effects of variation of surface and solution properties in microchannels on sample dispersion during electroosmotic migration. Zeta potential variations across and along the microchannel is found to generate a shear flow that increases the rate of dispersion of a sample plug. The electric conductivity variation due to the presence of a sample plug resulted in a complicated distortion of the sample plug due to the interaction between flow fields, electric potential, and species concentration. A study on the appropriateness of the 1-D Taylor dispersion method in microchip capillary electrophoresis modeling was also carried out.

Studies on slip casting behavior of lanthanum strontium manganite

Dispersion conditions for slip (slurry) formulation of a powder mixture of lanthanum strontium manganite (La 0.84Sr 0.16MnO 3 – LSM) and carbon (pore former) in water was studied through detailed zeta-potential and rheological measurements. The zeta potential variation with pH for the aqueous suspensions of only LSM or carbon exhibited a maximum value in alkaline medium (−40 mV to −50 mV at a pH of 10–11), establishing the pH window for their co-dispersion for slurry formulation. A study of the viscosity variation with shear rate for the slurries with varying solid content (in the range of 45–65 wt.%) exhibited pseudo-plastic flow behavior, indicating presence of flocculates in them. The yield stress values obtained from the Casson equation reduced with decreasing solid content, indicating reduction in the flocculate strength. The slip with solid content of 50 wt.% exhibited optimum flow characteristics to form long tubes with uniform wall thickness (wall thickness 2–4 mm and length of 150–200 mm). The tubular specimens formed after controlled carbon burn out and sintering at 1400 °C for 1 h possessed about 35% open porosity. The porosity remained the same upon further sintering at 1400 °C for 8 h.

RBPI 21 Causes (HEMI)Fusion and Leakage of Membranes and Promotes Massive Lipopolysaccharide Aggregation

Bacteria are infectious agents that seem to have difficulties in acquiring resistance against natural occurring antimicrobial peptides (AMPs). These positively charged polypeptides were then developed as an alternative to conventional therapy against bacterial infections. rBPI21 is a 21 kDa peptide based on the N-terminal region of the neutrophil bactericidal/permeability-increasing protein (BPI). It has bactericidal effects on Gram-negative bacteria and higher affinity for lipopolysaccharide (LPS), neutralizing its effect. rBPI21 is in phase III clinical trials against meningitis. This work aimed at elucidating the mechanism of action of rBPI21 at the molecular level. We demonstrate that rBPI21 promotes the aggregation of negatively charged large unilamellar vesicles (LUV) and LPS aggregates, by dynamic light scattering, while for zwitterionic phosphatidylcholine (POPC) LUV the size remains unchanged. The aggregation increases with peptide concentration until promotion of massive aggregation followed by sample flocculation/precipitation [1,2]. Through a Förster resonance energy transfer (FRET) assay, the aggregation is followed by (hemi)fusion of the negatively charged vesicles, culminating at their leakage (also assessed by fluorescence spectroscopy). With the rBPI21-lipid interaction, there is a progressive change in the zeta-potential of the LUV systems and LPS aggregates [2]. LUV systems composed of phosphatidylglycerol (POPG) and POPC:POPG mixtures have higher zeta-potential variations than POPC LUV. For the LPS aggregates, rBPI21 neutralizes the surface charge and, at higher peptide concentrations, overcompensates it [2]. The results demonstrate that rBPI21 mechanism of action at the molecular level involves the interaction with the LPS of the outer membrane of Gram-negative bacteria, followed by internalization and leakage induction through the (hemi)fusion of the bacterial outer and inner membranes, both enriched in phosphatidylglycerol. [1] Domingues, MM et al., Biophys. J. 2009, 96, 987-996. [2] Domingues, MM et al., PLoS ONE 2009, 4, e8385.

Hydrothermal synthesis of highly stabilised ZnS–polystyrene hybrid nanoparticles

Hydrothermal synthesis of ZnS nanoparticles in the presence of polystyrene (PS) nanosphere templates has been investigated. Polyvinylpyrrolidone (PVP) as dispersing agent and ethylenediaminetetraacetic acid (EDTA) as chelating agent caused the gradual formation of ZnS–PS hybrid nanoparticles. Chemical compound and structural studies revealed the formation of ZnS sphalerite phase which was increased by reaction time. The size of the hybrid particles was in the range of 40–60 nm. The formation of the hybrid particles was confirmed by the variation of zeta potential against pH. The obtained nanoparticles could be stabilised in aqueous medium for more than 2–3 months. It was in agreement with the controlled growth of ZnS nanoparticles on the surface of PS templates. The red shift of adsorption edge (from 4.36 to 4.27 eV) with an increase of reaction time was due to the growth of ZnS particles in the quantum confinement region.

Promoted slurryability of petroleum coke–water slurry by using black liquor as an additive

The purpose of this paper is to prepare the petroleum coke–water slurry with a maximal coke mass fraction and the superior slurry natures using black liquor as an additive. The variations of rheological properties, contact angle, fluidity, stability and zeta potential of the coke–water slurry with different black liquor dosages were investigated. It was observed that the addition of a black liquor dosage around 1.0 wt.% of the petroleum coke remarkably improved the rheological properties, fluidity and stability of the slurry, and the slurry could hold a mass of petroleum coke as high as 70 wt.%, with the superior apparent viscosity, fluidity and stability available for practical utilization.

Effects of pH on coagulation behavior and floc properties in Yellow River water treatment using ferric based coagulants

Enhanced coagulation is one of the major methods to control disinfection by-products (DBPs) in water treatment process. Coagulation pH is an important factor that affects the enhanced coagulation. Recently, many studies focus on the coagulation effects and mechanisms, and few researchers studied the properties of flocs formed under different coagulation pH. Two inorganic polymer coagulants, polyferric silicate sulphate (PFSS) and polyferric sulphate (PFS), were used in Yellow River water treatment. The influence of pH on coagulation effect was investigated under the optimum dosage, and the results show that both coagulants gave excellent organism removal efficiency when pH was 5.50. According to the variation of zeta potential in coagulation process, coagulation mechanisms of the coagulants were analyzed. An on-line laser scatter instrument was used to record the development of floc sizes during the coagulation period. For PFSS, pH exerted great influence on floc growth rates but little influence on formed floc sizes. In PFS coagulation process, when pH was 4.00, PFS flocs did not reach the steady-state during the whole coagulation period, while little difference was observed in floc formation when pH was 5.50 and above. The preformed flocs were exposed to strong shear force, and the variation of floc sizes was determined to evaluate the influence of pH on floc strength and re-growth capability. In comparison of the two coagulants, PFS flocs had higher floc strength and better recovery capability when pH was 4.00, while PFSS flocs had higher floc strength but weaker recovery capability when pH was 5.50 and above.

Recycling of spent filter backwash water using coagulation-assisted membrane filtration: effects of submicrometre particles on membrane flux

Membrane separation technology has been widely used for recycling of spent filter backwash water (SFBW) in water treatment plant. Membrane filtration performance is subject to characteristics of the particles in the SFBW. A bench-scale microfiltration (MF) coupled with pre-coagulation was set up to evaluate the recovery efficiency of SFBW. Effect of particle size distribution and zeta potential of the coagulated SFBW on the membrane filtration as well as the coagulation strategies were investigated. Pore clogging was more severe on the membrane with 1.0 mum pore size than on the membrane with 0.5 mum pore size due to the fact that submicrometre particles are dominant and their diameters are exactly closed to the pore size of the MF membrane. Pre-settling induced more severe irreversible fouling because only the submicrometre particles in the water become predominant after settling, resulting in the occurrence of more acute pore blocking of membrane. By contrast, pre-coagulation mitigates membrane fouling and improves membrane flux via enlarging particle size on membrane surface. The variations of zeta potential in response to coagulant dosing as well as fractal dimension were also compared with the performance of the subsequent filtration. The result showed that pre-coagulation induced by charge neutralization at the optimum dosage where the zeta potential is around zero leads to the optimal performance of the subsequent membrane filtration for SFBW recycling. At such condition, the fractal dimension of coagulated flocs reached minimum.

Surface hydrophobicity of petroleum hydrocarbon degrading Burkholderia strains and their interactions with NAPLs and surfaces

Bacterial cell surface hydrophobicity (CSH) is an important factor governing the growth and adhesion behavior of microorganisms on non-aqueous phase liquids (NAPLs). In this work CSH and surface charge was quantified for three oil degrading Burkholderia cultures: aliphatic degrader Burkholderia cepacia (ES1) and two strains of aromatic degrading Burkholderia multivorans (NG1 and HN1) based on contact angle and zeta potential measurement. Model non-aqueous phase liquids (NAPLs) were formulated using n-hexadecane, naphthalene, phenanthrene and pyrene in varying concentration. Adhesion on to glass surfaces of varying hydrophobicity and adherence to n-hexadecane was quantified and correlated with hydrophobicity of the surface; variation in CSH of the culture in response to model NAPL used as growth substrate; and variation in zeta potential as a result of variation in growth substrate, ionic strength and pH of resuspension solution. B. cepacia (ES1) and B. multivorans (HN1) depicted comparable CSH which was higher than that of B. multivorans (NG1). For each culture, CSH was found to vary with the model NAPL used as growth substrate. Adhesion to glass increased with increase in CSH of the bacterial culture and with increase in hydrophobicity of the glass surface. B. cepacia (ES1) with lower negative zeta potential consistently depicted greater adhesion compared to B. multivorans (HN1). Adherence to n-hexadecane was significantly affected by various other factors, such as, growth substrate, pH, resuspension solution and their interactions as revealed through statistical analysis. These factors affected both the zeta potential and adherence to n-hexadecane to varying degree for the three Burkholderia cultures.

Seasonal Changes in the Aggregate Status of Particles in Dough used in the Manufacture of Insulators

In order to clarify the mechanism of seasonal changes in agglomeration and dispersion of the slurry used in the manufacture of insulators, we focused our attention on the concentration of iron ions which elute within slurry, added water glass and long-term storage treatment to process slurry, ore slurry and clay slurry, carried out heating treatment, and then measured the concentration of the eluted iron ions. Furthermore, when we evaluated the variations in zeta potential and slurry fluidity, we discovered that there was an influence caused by slurry temperature during ore grinding. Slurry temperature during ore grinding can be 20°C or more warmer in the summer than in the winter. As a result, even greater amount of iron ions elute from the pottery stone. The elution of iron ions causes particles to acquire more negative charge, which causes stronger repulsion among particles. We learned that, during the summer months, when slurry is warmer and there is a great amount of eluted iron ions, slurry tends to disperse. Conversely, we also learned that in the winter months slurry tends to agglomerate.

RBPI21 Promotes Lipopolysaccharide Aggregation and Exerts Its Antimicrobial Effects by (Hemi)fusion of PG-Containing Membranes

Antimicrobial peptides (AMPs) are important potential alternatives to conventional therapies against bacterial infections. rBPI21 is a 21 kDa peptide based on the N-terminal region of the neutrophil bactericidal/permeability-increasing protein (BPI). This AMP possesses highly selective bactericidal effects on Gram-negative bacteria and have affinity for lipopolysaccharide (LPS) which is believed to be at the origin of its neutralizing effect of the LPS segregated into the bloodstream. We aim at understanding the molecular bases of rBPI21 bactericidal and LPS neutralization actions, using biomembrane model systems. Using dynamic light scattering spectroscopy we demonstrate that rBPI21 promotes aggregation of negatively charged large unilamellar vesicles (LUV), even in the absence of LPS, and LPS aggregates, while for zwitterionic phosphatidylcholine (POPC) LUV the size remains unchanged. The peptide also promotes the fusion (or hemifusion) of membranes containing phosphatidylglycerol (POPG). The aggregation and fusion of negatively charged LUV are peptide concentration-dependent until massive aggregation is reached, followed by sample flocculation/precipitation. Concomitantly, there is a progressive change in the zeta-potential of the LUV systems and LPS aggregates. LUV systems composed of phosphatidylglycerol (POPG) and lipid mixtures with POPG have higher zeta-potential variations than in the absence of POPG. The interaction of rBPI21 with lipid vesicles is followed by leakage, with higher effect in POPG-containing membranes. LPS aggregation can be related with a decreased toxicity, possibly by facilitating its clearance by macrophage phagocytosis and/or blocking of LPS specific receptor recognition. Our data indicate that rBPI21 mechanism of action at the molecular level involves the interaction with the LPS of the outer membrane of Gram-negative bacteria, followed by internalization and leakage induction through the (hemi)fusion of the bacterial outer and inner membranes, both enriched in phosphatidylglycerol.