Reduction In Zeta Potential Research Articles

Preparation, characterization of NIPAM and NIPAM/BAM copolymer nanoparticles and their acute toxicity testing using an aquatic test battery

Poly N-isopropylacrylamide and N-isopropylacrylamide/ N- tert-butylacrylamide copolymer nanoparticles of 50–70 nm were prepared by free radical polymerisation. The particle sizes of the copolymer nanoparticles were measured in the test media Milli-Q water, Algae Media, Daphnia Media and Microtox Diluent as a function of temperature. Whereas in Milli-Q water the particle size was seen to decrease above the lower critical solution temperature of the thermoresponsive polymer, in the test media it was seen to increase significantly, indicative of aggregation. At the temperatures employed for the ecotoxicological studies all particles, with the exception of the 50:50 copolymer existed as nanoparticles. The zeta potential of Poly N-isopropylacrylamide and N-isopropylacrylamide/ N- tert-butylacrylamide copolymer particles measured in the different media was seen to correlate well with the ratio of N- tert-butylacrylamide monomer and therefore the hydrophobicity of the particles. Ecotoxicological studies of the copolymer nanoparticles was performed using four test species Vibrio fischeri, Pseudokirchneriella subcapitata, Daphnia magna, Thamnocephalus platyurus and the cytotoxicity of the 100% Poly N-isopropylacrylamide and 85:15 N-isopropylacrylamide/ N- tert-butylacrylamide copolymer nanoparticles was evaluated using a salmonid cell line. Although no significant cytotoxicological response was recorded, significant ecotoxicological response was observed at particle concentrations of up to 1000 mg l −1. The ecotoxicological response was seen to correlate well with the ratio of N- tert-butylacrylamide monomer and therefore with the zeta potential of the nanoparticles. The toxic response in Daphnia magna was seen to further correlate with the reduction in zeta potential pointing towards a contribution of secondary effects due to modification of the medium. No correlation with particle size was observed. The sensitivity of the test species was seen to vary depending on copolymer composition. The relevance of the derived structure–activity relationships is discussed.

Electrokinetic Potential in B-Thalassemia Erythrocyte Membranes: Effect of Static Magnetic Field (2T)

ABSTRACTThe effects of the static magnetic field (SMF) on zeta potential of erythrocytes from patients with heterozygous ‘thalassemia’ and healthy subjects were studied by means of cell micro-electrophoresis. Electrophoretic mobility (EPM) of ‘thalassemic’ erythrocytes from patients in pregnancy decreased significantly after SMF exposure (0.1 - 2 T) compared to the same membranes without SMF pre-exposure. Significantly decreased extent of lipid peroxidation was observed in ‘thalassemic’ erythrocytes from patients in pregnancy increasing the dose of SMF pre-treatment. SMF exposure increased the aggregate's formation in erythrocyte suspension from healthy subjects as well as in ‘thalassemic’ erythrocytes at the expositions (0.5–2 T). Lectin—membrane interaction was tested on the EPM of erythrocytes in norm and pathology. Thus lectin binding may provide information about changes in glycoprotein complexes of the membrane. We studied the effect of Phaseolus vulgaris agglutinin (Phytohemagglutinin, PHA-M) on the surface charge density and 90° light scattering (LS) of erythrocytes in physiological pH (PBS, pH 7.6). PHA-M induced an increase in EPM of normal erythrocytes at doses of 60 pg PHA/ml and 150 pg PHA/ml. There was an enhancement in zeta potential of thalassemic erythrocytes upon pre-treatment with the 200 pgPHA/ml.SMF (0.1–2T) altered electrokinetic properties of ‘thalasemic’ erythrocytes with increased agglutinability, which could be due to reduction of zeta potential as well as decrease in lipid peroxidation products of erythrocyte membranes.

Poly(α-butyl cyanoacrylate) nanoparticles for intracellular delivery of protein: Physicochemical properties, cytotoxicity study and cellular uptake in dendritic cells

Abstract summary Poly(α-butyl cyanoacrylate) (PBCA) nanoparticles for intracellular delivery of protein were prepared by anionic polymerization method and characterized for their physicochemical properties, cytotoxicity and cellular uptake in dendritic cells (DC). The particles were in the nanometer size range and exposed a negative surface charge. Upon addition of protein, the particles became larger with slightly reduced zeta potential. Dextran, used as stabilizer, was found to retard the release of protein and reduce cytotoxicity of PBCA nanoparticles. The particles were efficiently taken up by the dendritic cells.

Preparation and Biophysical Characterization of Pluronic F127-Dendrimer Conjugate as a Delivery Agent of Antisense Oligonucleotides

A series of pluronic F127 conjugated PAMAM dendrimer generation 5 were prepared to evaluate the potential use of dendrimer-pluronic conjugates as a delivery agent of antisense oligonucleotides. The structural features of the conjugates were identified by FT-IR and 1H-NMR spectra. The prepared dendrimer generation 5-pluronic F127 conjugates showed particle size in the range of 50 to 130 nm with reduced zeta potential. The electrophoretic property of conjugates was further confirmed by capillary zone electrophoresis (CZE), demonstrating the decrease in electrophoretic mobility of conjugates as the number of pluronic F127 on surface of dendrimer increases. The number of free amino groups on a pluronic F127 conjugated dendrimer was quantitatively determined by fluorescamine assay, measuring the fluorescence intensity of amino groups reactive to fluorescamine on dendrimer generation 5-pluronic F127 conjugates. In MTT assay, dendrimer G5-pluronic F127 conjugates were safe on gingival fibroblast cells and acute toxicity was reduced as the mole ratio of dendrimer to pluronic increased. Complex formation of dendrimer G5-pluronic F127 conjugates with oligonucleotides was dose dependent.

Effect of polymerization method on structure and properties of cationic polyacrylamide

AbstractAcrylamide and 2‐(methacryloyloxy)ethyltrimethylammonium chloride (AM/MADQUAT) copolymers were synthesized by solution and inverse microemulsion polymerization using (NH4)2S2O8/NaHSO3 as redox initiator at the same feed mole ratio, and their microstructure, such as sequence distribution and composition distribution, was calculated from monomer reactivity ratios of different polymerization methods. The results show that charge distribution is more uniform for copolymer prepared in inverse microemulsion than that in solution, and copolymer composition distribution is close to unity, and maintains approximately at the feed ratio. Furthermore, the influence of the two structures of cationic polyacrylamides on kaolinite floc size and effective floc density, reduction of Zeta potential and floc compressive yield stress had been investigated at pH 7. The results show that the kaolinite floc size and effective floc density are strongly dependent upon copolymer microstructure, with greater floc size and lower effective floc density being observed for copolymer prepared in inverse microemulsion than for that in solution. Copolymer microstructure has a marked effect on the Zeta potential, whose reduction in the magnitude was much greater in the presence of copolymer prepared in inverse microemulsion than that in solution. Greater compressive yield stress was achieved for the strong flocs produced by copolymer prepared in inverse microemulsion than for the weak flocs produced by that in solution. The difference in flocs compressive yield stress may be attributed to flocs structure. Therefore, in this article, a correlation between the cationic polyacrylamide structure and flocculation property for kaolinite suspension was established. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

EFFECT OF POLYMERIZATION METHOD ON STRUCTURE AND PROPERTIES OF A CATIONIC POLYACRYLAMIDE

A cationic polyacrylamide was synthesized by polymerization of acrylamide and 2-(methacryloyloxy)-ethyltrimethylammonium chloride (AM/MADQUAT)in solution or by inverse microemulsion polymerization using (NH_4)_2S_2O_8/NaHSO_3 as redox initiator.The sequence distribution and composition distribution were calculated from monomer reactivity ratios of different polymerization methods.The results show that charge distribution is more uniform for the copolymer prepared in inverse microemulsion,and copolymer composition distribution is close to unity and maintains approximately at feed ratio.Furthermore,influence of the structure of cationic polyacrylamides on kaolinite flocs size,reduction of zeta potential and flocs compressive yield stress has been investigated at pH 7.The results show that the kaolinite flocs size is strongly dependent upon copolymer microstructure; with greater flocs size being observed for copolymer prepared in inverse microemulsion than for that in solution.Copolymer microstructure has a marked effect on the zeta potential,whose decrease in magnitude was much greater in the presence of copolymer prepared in inverse microemulsion than that in solution.Greater compressive yield stress was achieved for the strong flocs produced by copolymer prepared in inverse microemulsion.The difference in flocs compressive yield stress may be attributed to the flocs structure.Therefore,in this paper,a strong correlation between the cationic polyacrylamide structure and flocculation property for kaolinite suspension was established.

Self-Assembled Hollow Nanocapsule from Amphiphatic Carboxymethyl-hexanoyl Chitosan as Drug Carrier

A new type of amphiphilic chitosan, which was synthesized through the use of both hydrophilic carboxymethyl and hydrophobic hexanoyl substitutions, was employed to self-assemble into a hollow nanocapsule in an aqueous environment. Critical aggregation concentration (cac) and zeta potential were experimentally identified for the amphiphilic chitosan (CHC). Both experimental data suggested that the self-assembly behavior of the CHC is fundamentally determined as an interplay between the hydrophobic interaction and the variation of the zeta potential upon hexanoyl substitution, which further influenced the nanostructural evolution of the nanocapsules. Higher hexanoyl substitution promoted larger nanocapsules, ca. 200 nm in diameter, while a reduced zeta potential was correspondingly detected, and vice versa, forming smaller nanocapsules, ca. 20 nm in diameter. The self-assemble mechanism, together with the corresponding nanostructural stability, of this unique CHC nanocapsule was also proposed in terms of in...

Synthesis and Characterization of Organosilica Nanoparticles Prepared from 3-Mercaptopropyltrimethoxysilane as the Single Silica Source

Novel organosilica nanoparticles made of 3-mercaptopropyltrimethoxysilane as the single silica source (MPS NPs) have been synthesized successfully by using a Stober method. The MPS NPs were well dispersed in solution and have unique surface properties such as thiol residues on the surface and reduced zeta potential compared with the nanoparticles made of tetraethoxysilane. The MPS NPs with fluorescent dye were synthesized by a method that deposited fluorescent dye on the silica network. The resulting MPS NPs with fluorescence were bright, nonaggregated in solution, and photostable. The fluorescence intensity and photostability of fluorescent MPS NPs were sufficient for detection as a single fluorescent particle using flow cytometry and fluorescence microscopy. Protein-modified MPS NPs were prepared easily by absorption and by maleimide coupling. In this paper, we demonstrate the usefulness of MPS NPs and their surface properties and discuss their advantages for biological applications.

Effect of humic acid on the sorption of technetium on hematite colloids using 95mTc and 96Tc as tracers

Sorption of technetium on hematite colloids, at varying pH (3–10), has been studied in absence and presence of humic acid using 95mTc-96Tc radiotracers. Technetium was found to be weakly sorbed on hematite at lower pH (<5) values, while no sorption was observed at higher pH values. Humic acid was found to have no effect on the sorption of technetium on hematite under aerobic conditions, while at lower pH values small reduction was observed which was attributed to the reduced zeta potential of the hematite colloids owing to the strong sorption of humic acid.

Neutral Postgrafted Colloidal Particles for Gene Delivery

Surface modification of cationic lipoplexes has been carried out by means of a postgrafting reaction. The original lipoplexes described comprise a cationic lipid, a neutral lipid, poly(ethylene glycol)-cholesterol (with or without a targeting ligand) and DNA. Modifying their surface via a chemical, postgrafting reaction did not alter their size (approximately 100 nm) nor their ability to compact DNA, but did give a reduced zeta potential (approximately 0 mV) to afford surface neutral particles. With the modified lipoplexes nonspecific NIH3T3 cell surface binding in vitro was inhibited. Intravenous injection of the neutralized lipoplexes in mice showed decreased accumulation of the particles in the lung as compared to PEGylated cationic lipoplexes. Tumor targeting was also achieved in vivo by the addition of an RGD-PEG-Cholesterol as a lipid-ligand in the postgrafted lipoplex formulation.

Influence of hydrolyzable metal ions on the interfacial chemistry, particle interactions, and dewatering behavior of kaolinite dispersions

The influence of hydrolyzable metal ions (Mn(II) and Ca(II)) adsorption on the surface chemistry, particle interactions, flocculation, and dewatering behavior of kaolinite dispersions has been investigated at pH 7.5 and 10.5. Metal ion adsorption was strongly cation type- and pH-dependent and significantly influenced the zeta potential, anionic polyacrylamide–acrylate flocculant (PAM) adsorption, shear yield stress, settling rate, and consolidation of kaolinite slurries. The presence of Mn(II) and Ca(II) ions alone led to a systematic reduction in zeta potential due to specific adsorption of positively charged metal ion-based hydrolysis products at the kaolinite–water interface. Metal ion-mediated zeta potential changes were reflected by lower dispersion shear yield stresses and improved clarification (higher settling rates) but had no detectable effect on dispersion consolidation. The adsorption of PAM was significantly improved by prior addition of the metal ions. In the presence of Mn(II) or Ca(II) ions, the flocculant adsorption density was enhanced at pH 7.5 for Mn(II) and pH 10.5 for Ca(II). Optimum flocculation conditions, involving partial rather than complete particle surface coverage by both metal ions and flocculant, were identified. As a consequence, the metal ions and flocculant acted synergistically to enhance dewatering, producing particle interactions that were more conducive to high settling rates and greater consolidation of kaolinite dispersions at pH 7.5 than 10.5.

Zeta Potential Measurments of Graphite Ore Minerals and its Correlation on Selective Flotation of Graphite

In the present study, the surface chemical properties of graphite ore minerals with and without using tannin were characterized by electrokinetic measurements and adsorption studies and its correlation was studied with selective flotability of graphite and calcite. The results indicated that tannin has not shown significant effect on zeta potential with graphite at all pH ranges, whereas the effect of tannin on calcite mineral has shown a reduction in zeta potential due to adsorption of tannin on calcite surface; hence flotation selectively depressed calcite at alkaline pH and promoted to float graphite alone.

The structure of PEG-modified poly(ethylene imines) influences biodistribution and pharmacokinetics of their complexes with NF-kappaB decoy in mice.

To study the relationship between structure of poly(ethylene imine-co-ethylene glycol), PEI-PEG, copolymers and physicochemical properties as well as in vivo behavior of their complexes with NF-kappaB decoy. A variety of copolymers of PEG grafted onto PEI as well as PEI grafted onto PEG were synthesized and their complexes with a double stranded 20mer oligonucleotide were examined regarding size, surface charge, biodistribution and pharmacokinetics. Polyplexes of copolymers were smaller compared to polyplexes formed by non-PEGylated PEI 25 kDa (58 - 334 nm vs. 437 nm for a nitrogen/phosphate ratio of 3.5 and 85 - 308 nm vs. 408 nm for N/P 6.0) and showed reduced zeta potential (-2.5 - 6.4 mV vs. 14.5 mV for N/P 6.0). IV injection into mice revealed liver (35-76% of injected dose), kidney (3 - 22%) and spleen (2 - 16%) to be the main target organs for all injected complexes. Complexes formed by copolymers with few PEG blocks of higher molecular weight (5 kDa and 20 kDa) grafted onto PEI 25 kDa did not show different blood levels from PEI 25 kDa. In contrast, a copolymer with more short PEG blocks (550 Da) grafted onto PEI showed elevated blood levels with an increase in AUC of 62 %. A sufficiently high density of PEG molecules is necessary to effectively prevent opsonization and thereby rapid clearance from blood stream.

Physical properties and stability of two emulsion formulations of propofol

We have compared the physical properties of two commercial emulsion formulations of the intravenous anaesthetic propofol, (Diprivan®, AstraZeneca, and Propofol Intravenous Emulsion, Gensia Sicor Pharmaceuticals) which appear to differ primarily in the additive content and formulation pH. Diprivan® contains disodium edetate and has a pH of 7–8.5, while the Gensia product contains sodium metabisulphite and is formulated to a pH of 4.5–6.4. The average zeta potential of Diprivan® at pH 8 was −50 mV while that of the Gensia product at pH 4–5 was −40 mV. This information suggests that the physical stability of Propofol Intravenous Emulsion should be lower than that of Diprivan®. Three random batches of both products were subjected to a range of stability tests, including shaking, thermal cycling, and freeze–thaw cycling, and the emulsion droplet size distribution was then assessed by dynamic light scattering, light diffraction, and electrical and optical zone sensing. Both emulsions initially showed narrow submicrometre particle size distributions. An increased level of droplets larger than 5 μm could be detected in Propofol Intravenous Emulsion after as little as 4 h shaking (300 strokes/min at room temperature) and visible free oil could be detected after 8–12 h shaking. In contrast, Diprivan® showed no increase in the large droplet count after shaking for times up to 16 h. A similar difference in the emulsions was found after one freeze–thaw cycle, with Propofol Intravenous Emulsion exhibiting extensive coalescence, while that of Diprivan® was at the limits of detection. We conclude that these two products have different physical stability characteristics, and that this may in part be due to the reduced zeta potential in Propofol Intravenous Emulsion compared to that of Diprivan®.

Effect of Calcium on Lead in Soft-Water Distribution Systems

Meeting the lead rule action level for drinking water can be difficult for soft-water systems. One concern in these systems is the formation of particulate or colloidal lead that is difficult to remove from the aqueous phase. In this preliminary study, batch and pipe-loop systems are used to assess the effect of calcium addition on lowering the concentration of particulate or colloidal lead. The addition of calcium at levels as low as 5 mg/L reduced zeta potential of lead-bound colloids and in some cases resulted in a reduction of total Pb concentration.

Compatibility of propofol, fentanyl, and vecuronium mixtures designed for potential use in anesthesia and patient transport

Study Objective: To determine whether propofol emulsion, fentanyl, and vecuronium remain compatible and stable when mixed in clinically appropriate concentrations. Design: Seven separate in vitro experiments. Two different propofol-fentanyl-vecuronium mixtures were formulated. Regular assays of propofol, fentanyl, and vecuronium were performed during a 90-minute infusion period and also during storage of one of the mixtures for 30 days at 4 °C, 22 °C, and 30 °C. Initial and storage pH were determined, and assays of the three drugs were performed when pH of the mixtures was varied between 1.4 and 12.7. Emulsion stability was assessed by measuring immediate and delayed alterations in droplet charge (zeta potential) and size. Finally, samples of the stored mixtures were incubated in culture medium for one week. Setting: Teaching hospital and university laboratories. Measurements and Main Results: Concentrations of the three drugs remained unchanged during infusion. During storage, concentrations of all three drugs were stable for two weeks at 4 °C or 22 °C, and for several days at 30 °C. Initial pH of the two mixtures was 5.1 and 5.3, and pH of the stored mixture increased slowly after 8 days. When the pH of mixtures was greater than or equal to 5.6, concentrations of fentanyl and vecuronium were unstable, but the concentration of propofol remained unchanged. Despite a reduction in zeta potential, immediate droplet size was essentially unchanged. No microbial growth was detected in stored mixtures. Conclusion: The propofol, fentanyl, and vecuronium mixtures studied were compatible and stable immediately after mixing. Appropriate in vitro compatibility testing is recommended before clinical evaluation of propofol-opioid or propofol-opioid-musck relaxant mixtures.

Dispersion and zeta potential of pure clays as related to net particle charge under varying pH, electrolyte concentration and cation type

SummaryThe effect of changing pH and electrolyte concentration on the dispersion and zeta potential of Na‐and Ca‐forms of kaolinite, illite and smectite was investigated in relation to changes in their net negative charge.The percentage of dispersible Na‐clay and the percentage increase in net negative charge was positively correlated with pH, but the slopes varied from clay to clay. In general, the net negative charge was the primary factor in clay dispersion, and the pH affected clay dispersion by changing the net charge on clay particles. Na‐smectite had larger net charge at all pHs than Na‐illite and Na‐kaolinite, and it always had larger flocculation values. The role of electrolyte concentration could be due to its effect both on flocculation and variable charge component of the clay minerals. The zeta potential at different pHs also reflected the same trend of clay dispersion with net particle charge.In Ca‐clays the trends were similar to Na‐clays up to pH 7.0. In more alkaline solution CaCO3 formation led to charge reduction on clay particles, resulting in flocculation and reduction of zeta potential. At similar pHs the electrophoretic mobilities of all the clays showed constant potential behaviour. However, the zeta potentials of Ca‐clays were always smaller than those of sodic clays because the clays were more aggregated. Net particle charge was the most important factor in controlling clay dispersion for the whole range of pH and ionic strength and for all types of cations.

Oil recovery and waste reduction by microwave radiation

AbstractOil‐in‐water and oil‐water‐solid emulsions, by‐products of various industrial operations, often are environmental concerns. Laboratory and field tests have shown that these emulsions can be demulsified and separated into their individual layers by microwave radiation. The data also show that microwave separation is faster than gravity separation and can be faster than conventnal heating at many conditions. After separation of emulsion into water, slop and oil layers, water can be discharged and oil is collected for recycle. The volume of slop is much smaller than the original volume of emulsion, therefore, the oily waste to be disposed is greatly reduced.The zeta potential of oily droplets in water was measured and found that it is reduced by microwave radiation. This indicates that microwave provides heating and reduction of zeta potential in demulsification.

Adsorption of Zn(II) onto hydrous aluminosilicates in the presence of EDTA

The effects of EDTA on the adsorption of Zn(II) onto various hydrous aluminosilicates was investigated. Two major types of aluminosilicates, amorphous (Zeosyl 100, Zeo 49, Zeolex 23 and Blazer), and crystalline (Zeolite A and Mordenite) and two simple oxides (SiO 2 and Al 2O 3) were studied. Adsorption of EDTA occurred in the acidic pH range and was more pronounced for solids with a low silica to aluminum ratio. The adsorption of EDTA is brought by specific interactions with the surface hydroxyl groups. Solids with a high Si/Al ratio have negatively charged sites, hence little adsorption of EDTA. Depending on the types of solids, the addition of EDTA resulted in a shift of maximum Zn(II) adsorption to the acidic pH range, and reduction of zeta potential. In general, Zn(II) removal in the presence of EDTA was significantly reduced at the alkaline pH range, and slightly enhanced in the acidic pH range. Zn(II) removal in the presence of EDTA is associated with Zn-EDTA complex for γ-alumina. For aluminosilicates, Zn(II) removal may follow an ion exchange process with either free Zn(II) or complex Zn-EDTA, and to some extent, specific adsorption at constant potential sites.

Inhibition of human red cell sodium and potassium transport by divalent cations.

The influx and efflux of Na and K across the human red cell membrane by the bumetanide-sensitive (Na-K co-transport) and residual (ouabain- and bumetanide-insensitive) routes were inhibited by increasing concentrations of external Mg. Ca, Sr, Ba, Mn and Co also inhibited bumetanide-sensitive and residual K transport. External Mg inhibited choline uptake and the Na-dependent fractions of L-alanine and L-serine uptakes. External Mg reduced the maximal rate (app. Vmax) but not the affinity (app. Km) of the bumetanide-sensitive K and Na influxes when they were measured as functions of external K and Na respectively. The inhibitory effect of Mg was not due to a small reduction in zeta potential since much larger reductions in zeta potential produced by neuraminidase did not affect transport. Internal Mg stimulated the ouabain-sensitive K influx but inhibited the co-transport and residual components of K influx. Bumetanide was a poor co-transport inhibitor in red cells pre-treated with A23187 and EDTA. It was concluded that the inhibitory effects of external Mg were probably not due to changes in the ionic composition of the diffuse double layer adjacent to the cell membrane. Mg and other divalent cations should not be used as 'inert' ionic substitutes in human red cell Na and K transport studies.