Shift In Zeta Potential Research Articles

Cytotoxicity and antibacterial activity of gold-supported cerium oxide nanoparticles.

BackgroundCerium oxide nanoparticles (CeO2) have been shown to be a novel therapeutic in many biomedical applications. Gold (Au) nanoparticles have also attracted widespread interest due to their chemical stability and unique optical properties. Thus, decorating Au on CeO2 nanoparticles would have potential for exploitation in the biomedical field.MethodsIn the present work, CeO2 nanoparticles synthesized by a chemical combustion method were supported with 3.5% Au (Au/CeO2) by a deposition-precipitation method. The as-synthesized Au, CeO2, and Au/CeO2 nanoparticles were evaluated for antibacterial activity and cytotoxicity in RAW 264.7 normal cells and A549 lung cancer cells.ResultsThe as-synthesized nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy, and ultraviolet-visible measurements. The X-ray diffraction study confirmed the formation of cubic fluorite-structured CeO2 nanoparticles with a size of 10 nm. All synthesized nanoparticles were nontoxic towards RAW 264.7 cells at doses of 0–1,000 μM except for Au at >100 μM. For A549 cancer cells, Au/CeO2 had the highest inhibitory effect, followed by both Au and CeO2 which showed a similar effect at 500 and 1,000 μM. Initial binding of nanoparticles occurred through localized positively charged sites in A549 cells as shown by a shift in zeta potential from positive to negative after 24 hours of incubation. A dose-dependent elevation in reactive oxygen species indicated that the pro-oxidant activity of the nanoparticles was responsible for their cytotoxicity towards A549 cells. In addition, cellular uptake seen on transmission electron microscopic images indicated predominant localization of nanoparticles in the cytoplasmic matrix and mitochondrial damage due to oxidative stress. With regard to antibacterial activity, both types of nanoparticles had the strongest inhibitory effect on Bacillus subtilis in monoculture systems, followed by Salmonella enteritidis, Escherichia coli, and Staphylococcus aureus, while, in coculture tests with Lactobacillus plantarum, S. aureus was inhibited to a greater extent than the other bacteria.ConclusionGold-supported CeO2 nanoparticles may be a potential nanomaterial for in vivo application owing to their biocompatible and antibacterial properties.

Carbon nanoparticles for gene transfection in eukaryotic cell lines

For the first time, oxygen terminated cellulose carbon nanoparticles (CCN) was synthesised and applied in gene transfection of pIRES plasmid. The CCN was prepared from catalytic of polyaniline by chemical vapour deposition techniques. This plasmid contains one gene that encodes the green fluorescent protein (GFP) in eukaryotic cells, making them fluorescent. This new nanomaterial and pIRES plasmid formed π-stacking when dispersed in water by magnetic stirring. The frequencies shift in zeta potential confirmed the plasmid strongly connects to the nanomaterial. In vitro tests found that this conjugation was phagocytised by NG97, NIH-3T3 and A549 cell lines making them fluorescent, which was visualised by fluorescent microscopy. Before the transfection test, we studied CCN in cell viability. Both MTT and Neutral Red uptake tests were carried out using NG97, NIH-3T3 and A549 cell lines. Further, we use metabolomics to verify if small amounts of nanomaterial would be enough to cause some cellular damage in NG97 cells. We showed two mechanisms of action by CCN–DNA complex, producing an exogenous protein by the transfected cell and metabolomic changes that contributed by better understanding of glioblastoma, being the major finding of this work. Our results suggested that this nanomaterial has great potential as a gene carrier agent in non-viral based therapy, with low cytotoxicity, good transfection efficiency, and low cell damage in small amounts of nanomaterials in metabolomic tests.

Design and evaluation of Lumefantrine – Oleic acid self nanoemulsifying ionic complex for enhanced dissolution

BackgroundLumefantrine, an antimalarial molecule has very low and variable bioavailability owing to its extremely poor solubility in water. It is recommended to be taken with milk to enhance its solubility and bioavailability. The aim of present study was to develop a Self Nanoemulsifying Delivery system (SNEDs) of lumefantrine (LF) to achieve rapid and complete dissolution independent of food-fat and surfactant in dissolution media.MethodsSolubility of LF in oil, co-solvent/co-surfactant and surfactant solution and emulsification efficiency of surfactant were analyzed to optimize the LF loaded self nanoemulsifying preconcentrate. Effect of LF-oleic acid complexation on emulsification, droplet size, zeta potential and dissolution were investigated. Effect of milk concentration and fat content on saturation solubility and dissolution of LF was investigated. Dissolution of marketed formulation and LF-SNEDs was carried out in pH 1.2 and pH 6.8 phosphate buffer.ResultsLF exhibited very high solubility in oleic acid owing to complexation between tertiary amine of LF and carboxyl group of oleic acid (OA). Cremophore EL and medium chain monoglyceride were selected surfactant and co-surfactant, respectively. Significantly smaller droplet size (37 nm), shift in zeta potential from negative to positive value, very high drug loading in lipid based system (> 10%), no precipitation after dissolution are the major distinguish characteristics contributed by LF-OA complex in the SNED system. Saturation solubility and dissolution study in milk containing media pointed the significant increment in solubility of LF in the presence of milk-food fat. LF-SNEDs showed > 90% LF release within 30 min in pH 1.2 while marketed tablet showed almost 0% drug release.ConclusionSelf nanoemulsification promoting ionic complexation between basic drug and oleic acid hold great promise in enhancing solubility of hydrophobic drugs.

Hypochlorite treatment on thin film composite RO membrane to improve boron removal performance

Controlled hypochlorite treatment was conducted on three commercial RO membranes to improve their boron removal performance. The effects of hypochlorite treatment on membrane performance, including permeate flux, NaCl rejection as well as boron removal were investigated. The effect of pH of feed water on both original and chlorinated membranes was also investigated. In order to better understand the membrane performance changes related to membrane structure and physicochemical property changes caused by hypochlorite treatment, the membranes before and after chlorination were characterized by XPS, ATR-FTIR, SEM, AFM, surface contact angle, zeta potential and isopropanol (IPA) rejection. The results showed that all the chlorinated membranes had better performance than the original ones, including boron removal, NaCl rejection and permeate flux. Boron can be removed efficiently at pH of 11 after hypochlorite treatment and boron concentration of permeate water was less than 0.5 mg·L − 1 . Chlorine had been bound to the surface of the membrane, which led to a more hydrophilic, more negatively charged surface and without change of the morphology. The negative shift of zeta potential and increase of IPA rejection indicated that both electrostatic repulsion and size exclusion effects contributed to the enhanced boron and NaCl rejection.

Implication of zeta potential at different salinities on boron removal by RO membranes

Boron removal by reverse osmosis (RO) membranes has been improved through raised pH and its removal mechanism was suggested as either charge repulsion or size exclusion. In the present study, boron removal by different RO membranes at different salinities was investigated along with their respective zeta potentials. While the impact of salinity on zeta potential of RO membranes was similar, its impact on boron removal by brackish water reverse osmosis (BWRO) membranes was different from that by SWC4+ and ESPAB membranes. RO membranes used in this study showed negative zeta potential value at high pH. However, at pH 9 and with higher salinity, their zeta potentials shifted to positive values. Boron removal by BWRO membranes decreased with increasing salinity at pH 9. The shift of zeta potential towards positive values at higher salinity suggested that charge repulsion mechanism became less dominant. Boron removal by ESPAB and SWC4+ decreased initially when NaCl concentration was increased towards 2000 mg/L at pH 9. However, removal increased slowly when NaCl was beyond 2000 mg/L. This observation suggested that boron removal by these membranes at low salinity was partially contributed by charge repulsion mechanism. At higher salinity, size exclusion could be the dominant factor for boron removal by SWC4 and ESPAB.

Efficacy of surface charge in targeting pegylated nanoparticles of sulpiride to the brain

The objective of the study was to formulate sulpiride-loaded nanoparticles (NPs) that can improve bioretention and achieve dose reduction by passively targeting the drug near the site of action. Methoxy PEG–PLA and maleimide PEG–PLA were synthesized via ring opening polymerization of l-lactide and used to prepare pegylated nanoparticles (NPs) loaded with sulpiride by emulsification and solvent evaporation method. Thiolated cationized bovine serum albumin (CBSA) was conjugated through the maleimide function to the NPs. Rhodamine B and Alexa Fluor® 488 were used as fluorescent markers for nanoparticle uptake studies. The nanoparticles were characterized for particle size, zeta potential and drug loading. Sprague Dawley rats were administered with each of CBSA-NPs, BSA-NPs and uncoated NPs (10 mg/kg) via tail vein; plasma and urine concentrations were measured and tissue sections were observed under fluorescence microscope. Characterized particles (mean particle size 329 ± 44 nm) indicated the conjugation of cationic albumin to NPs (zeta potential shift from −39 mV to −19 mV). Fluorescence showed a high accumulation of CBSA-NPs in brain compared to that of BSA-NPs and uncoated NPs supported by plasma and urine profile. The significant results proved that CBSA-NPs could be a promising brain drug delivery for sulpiride.

Study on the mucoadhesion mechanism of pectin by atomic force microscopy and mucin-particle method

Atomic force microscopy (AFM) has been used to probe the interaction between porcine stomach mucin and a mucoadhesive polymer, pectin, with different chemical characteristics. Images were produced detailing the structures of mucin, pectin and the mixtures of pectin and mucin, in either 0.1 N hydrochloric acid or deionized water. The AFM images of the pectin–mucin mixture in acidic medium showed no association between pectin and mucin. The large aggregates observed after mixing pectin and mucin in deionized water revealed the association between pectin and mucin, probably by the H-bonding. Increasing of pectin in the mixture with mucin resulted in a shift of zeta potential of the mixture to a higher negative value. The electrostatic repulsion with the same charges of pectin and mucin may cause an uncoiling of polymer chains, which facilitated chain entanglement and bond formation. The particle size of the mixtures of pectin and mucin depended on the proportion of either pectin or mucin in the mixture. The results suggested that the mucoadhesion of pectin could be due to the adsorption mechanism on the mucin molecules or electrostatic repulsion between pectin and mucin.

Tailoring surface properties of biomedical polymers by implantation of Ar and He ions

Ion implantation at 25 and 100 keV has been used as a tool for the modification of the surface properties of two biomedical polymers. The modulation induced by the different energy dispersion mechanisms of Ar and He have allowed satisfactory modifications for both the activation of the surfaces of chemically functional polycaprolactone (PCL) and the stabilization of anti-fouling poly(ethylene glycol) (PEG). In both cases the implantations have been performed at doses of 10 14 cm −2 by taking into account the effect of different current densities, which are shown to distinctly influence the fragmentation-crosslinking of the target polymers. The resultant films were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, time of flight secondary ion mass spectroscopy and atomic force microscopy. Both shifts in zeta potential versus pH curves and the alteration of the polar components of the surface free energy (contact angle measurements) were correlated with the composition analysis. The response of the modified surfaces towards biomolecular interaction is demonstrated by the induction of preferential adsorption on irradiated PCL and the inhibited adsorption onto implanted PEG regions for selected oligopeptides and proteins.

Effect of bile components on the surface properties of bifidobacteria.

The action of bile on bifidobacteria was studied by measuring changes in zeta potential. hydrophobicity and adherence to enterocyte-like cells in vitro. Highly hydrophobic strains shocked with bile displayed more negative zeta potential values and a decrease in adherence. When a non-hydrophobic non-adherent strain (CIDCA 5324) was shocked with bile, an increase in hydrophobicity was observed. However, no changes of zeta potential or adherence properties were apparent. The action of the bile components was different from the action of whole bile. Cholate and deoxycholate produced a decrease in the negativity of zeta potential values of all strains studied whereas taurocholate displayed a shift in zeta potential of hydrophobic strains to more negative values, thus explaining the decrease in the autoaggregation by charge repulsion. However, the decrease in zeta potential caused by cholate and deoxycholate did not increase autoaggregation in a hydrophobic non-adherent strain (CIDCA 531). This suggests that other forces are contributing to autoaggregation.

Temporal zeta potential variations of 45S5 bioactive glass immersed in an electrolyte solution

45S5 bioactive glass (BG) is a bioactive material known to bond to bone in vivo through a surface calcium phosphate (Ca-P) layer. The goal of this study was to address the importance of BG surface charge in the bioactive response by examining the relationship between charge variations and the formation of the surface Ca-P layer. The zeta potential of BG in an electrolyte solution (TE) was measured by particle electrophoresis, and the formation of a Ca-P layer was characterized using SEM, EDXA, and FTIR. Si, Ca, and P solution concentrations also were determined. The initial BG surface was negatively charged, and two sign reversals were detected during 3 days of immersion. The first, from negative to positive after 1 day, is attributed to the adsorption of cations at the BG surface, and the second reversal was due to the precipitation of phosphate ions from solution. A strong correlation was found between the formation of a Ca-P layer and BG surface zeta potential variations. The dynamic shift in zeta potential from an initially negative surface to a positively charged surface directly corresponded with the formation of an amorphous Ca-P layer. In addition, when the glass surface matured into a crystalline Ca-P layer, it was associated with a reversal from a positive to a negative surface. Future work will focus on the effects of protein adsorption on BG surface charge and Ca-P layer formation kinetics as well as on cellular response to a changing BG surface.

Changes in surface characteristics of silicon nitride prepared for extrusion

The preparation step for extrusion (with binders) of Si 3N 4 powder, as well as the extrusion process itself, modify the original properties of the powder so that its recovery and subsequent rework are not possible. X-ray photoelectron spectroscopy (XPS), X-ray diffraction, infra-red spectroscopy, potentiometric titrations and zeta potential determinations have been used to identify the surface modifications in Si 3N 4 due to addition of binders, and to examine powders after elimination of the binders by extraction with organic solvents and heat treatment. The original Si 3N 4 with binders showed a shift in zeta potential and point of zero charge (PZC) to lower pH, indicating the adsorption of organic compounds on the Si 3N 4 surface at this step. The appearance of one O ls peak at 532.3 eV in the XPS spectrum showed the presence of Si 2N 2O. After extraction with organic solvents the PZC value was close to that of the Si 3N 4 + binders (pH = 3.2), indicating incomplete removal of organics; this was confirmed by XPS determination (C ls intensity data) and chemical analysis. The presence of Si 2N 2O was not modified as shown by XPS and the value of the isoelectric point. Heat treatment removes the organics completely but produces an oxidation of Si 3N 4 to SiO 2 as evidenced by a shift in the binding energy of the O ls photopeak to 534.0 eV.

Reversible and irreversible surface charge modification of bacteria for facilitating transport through porous media

Reversible and irreversible surface charge modification of Bacillus subtilis (a gram-positive aerobe), Pseudomonas fluorescens (a gram-negative species) and polymeric microspheres was attempted using common chemicals. This study was undertaken to see if such chemicals could be used to alter significantly the transport of various bacterial species through porous media. Significant surface charge alterations were observed in the irreversible treatments as shown by zeta potential measurements. The changes were shown to be partly reversible as evidenced by much larger shifts in zeta potential in the presence of the chemicals. Sodium pyrophosphate was found to alter the surface charge most significantly. All three species showed similar trends. Experiments on the transport of these species through sandpacks showed that their transport was significantly enhanced by the presence of the chemicals. The excellent correlation between high surface charge and transportability clearly suggests that electrostatic interactions between bacteria and sand grains are a dominant factor in their retention. Other bacterial retention mechanisms such as polymer adhesion seem to be relatively unimportant, at least for the species studied here. The various mechanisms responsible for the improved transportability and the surface charge modification are discussed. The applications of the study to filtration and microbial-enhanced oil recovery are pointed out.

Effect of lipid phase transition on the binding of anions to dimyristoylphosphatidylcholine liposomes

Temperature dependence of the electrophoretic mobility of multilamellar liposomes prepared from dimyristoylphosphatidylcholine was measured in the presence of salts with different anions in aqueous solutions. It was established that specific binding of anions to liposome surface induced a pronounced zeta potential (electrostatic potential at the hydrodynamic plane of shear). A combination of Langmuir, Gouy-Chapman, and Boltzmann equations was used to describe the dependence of the zeta potential on the concentration of anions. The values of binding constants ( K) and maximum numbers of binding sites per unit area ( σ max ) were determined by this method. The sequence for anion affinities to liposome surface was found to be as follows: trinitrophenol > ClO 4 − > I − > SCN − > Br − > NO 3 − > Cl − ≊ SO 4 2− . A sharp increase in the negative zeta potential was detected at the temperature of phase transition of the lipid from the gel to liquid-crystalline state. It was found that the parameter K did not change at lipid phase transition and the shifts in zeta potential might be due to alterations of σ max . The binding sites were considered as defects in the package of lipid molecules in membranes.