Zeta Potential Data Research Articles

Effect of compact spherical potassium 12-tungstosilicate and lithium heteropolytungstate additives on the rheology and surface chemistry of washed spherical and platelet α-Al2O3 suspensions: Patch charge bridging

The zeta potential data confirmed the adsorption of the large compact Keggin [Si(W12O40)]4- and heteropolytungstate (LST) anions on both α-Al2O3. The adsorbed [Si(W12O40)]4- ions should form a thick steric barrier, ~1 nm, but this effect was not reflected in the yield stress results. A relatively strong additional attractive force explained the increasing maximum yield stress. A similar result was observed with LST. For the spherical α-Al2O3 the largest maximum yield stress (at zero charge) occurred at 0.6 dwb% additive. This attractive force was attributed to patch charge attraction between the negative additive patch and the positive surface site. For the low surface area platelet α-Al2O3 suspensions, complete surface coverage occurred at a low additive concentration as reflected by an almost identical all negative zeta potential-pH behaviour at all additive concentrations at low pH. The slightly larger yield stress at pH 2.5 could be due to this patch charge bridging attraction.

Rapid Characterization and Modeling of Natural and Undefined Charge-Regulated Surfaces in Aqueous Systems.

The surfaces of most materials in aqueous systems are charged due to the ionization of surface functional groups. When these surfaces interact, the surface charge, electrostatic potential, and pH will vary as a function of separation distance, and this process is termed the charge-regulation effect. Charge regulation is a controlling factor in the adhesion and transport of colloids and microorganisms in aqueous systems, and its modeling requires representation of the pH-charge response of the surfaces, typically provided as the equilibrium constants (K) and site densities (N) of the dominant surface functional groups. Existing methods for obtaining these parameters demonstrate shortcomings when applied to many natural and man-made materials, such as weathered materials, materials with undefined or complex surface structures, and permeable materials, and for materials that do not provide the requisite high surface area in suspension due to small sample sizes. This hinders inclusion of the charge-regulation effect in colloid and microbial transport studies, and most studies of colloidal and microbial surface interactions use simplifying assumptions; a key example is the routine use of the constant potential assumption in DLVO modeling. Here we present a robust method that overcomes these issues and provides a rapid means to characterize charge-regulated surfaces using zeta potential data, without requiring a priori knowledge of the material composition. Applying a combined charge-regulation and Gouy-Chapman model, K and N values are obtained that accurately represent the electrostatic response of a charge-regulated surface. This method is demonstrated using activated carbon, aluminum oxide, iron (hydr)oxide, feldspar, and silica sand. The resulting K and N values are then used to show the variations in surface charge, electrostatic potential, and pH that can occur as these charge-regulated surfaces interact. This method provides a readily applied experimental approach for characterizing charge-regulated surfaces, with the overall goal to promote the inclusion of charge-regulated interactions into adhesion and transport studies with natural and undefined materials.

Spodumene Flotation Mechanism

Fine and coarse fractions of spodumene were obtained from a pegmatite ore and their flotation was investigated under different conditions. In particular, the optimum pH and collector dosage were studied. It was found that the best flotation performance occurs at pH 10 using 250 mg/L of sodium oleate. It was also observed that upon the addition of CaCl2, spodumene flotation recovery increases to about 90%. In addition, poor floatability was found for spodumene when Na2CO3 was used as a pH regulator (compared to NaOH).The zeta potential data confirmed the adsorption of oleate on the spodumene surface. It was found that activation of spodumene by calcium ions makes the surface charge less negative due to the adsorption of Ca2+ on the surface. The crystallographic properties of spodumene were analyzed. The adsorption of sodium oleate was attributed to the chemisorption of oleate to the exposed Al and Si sites generated after breakage of the Al–O and Si–O bonds on the mineral surface. It was observed that the {110} planes are the most favorable for the adsorption of oleate. The {110} plane is the weakest plane, and spodumene has the highest tendency to cleave along this plane. The XRD data revealed that fine spodumene particles have more {110} planes than the coarser fraction, which may explain why the former has better floatability.

Evaluation of the interaction between polymyxin B and Pseudomonas aeruginosa biofilm and planktonic cells: reactive oxygen species induction and zeta potential

BackgroundAlthough the most widely accepted mechanism of action for polymyxins is related to bacterial lysis via disruption, we hypothesized that this antimicrobial drug class could have other effects on Pseudomonas aeruginosa planktonic and sessile cells. Little is known regarding oxidative burst and zeta potential (ZP) data associated with the interaction between polymyxin B and P. aeruginosa cells. The present study evaluated endogenous reactive oxygen species (ROS) production and changes in the net charges of biofilm and planktonic cells in response to polymyxin B.ResultsPolymyxin B induced concentration-dependent killing at all concentrations tested in planktonic and sessile cells from P. aeruginosa strains. Sublethal concentrations of polymyxin B induced oxidative burst. ROS production was higher in resistant planktonic cells than in biofilm cells but this was not observed for susceptible cells. Moreover, no net surface charge alterations were observed in planktonic cells from a susceptible strain treated with polymyxin B, but a significant increase of ZP was noted in planktonic cells from a resistant strain.ConclusionOxidative burst generated by planktonic and sessile cells from P. aeruginosa strains against polymyxin B indicates that ROS may have an important role in the mechanism of action of this drug. ZP data revealed that electrostatic interactions of the cationic peptide with the anionic surface of the cells are strain-dependent. Therefore, we suggested that the intracellular effects of polymyxin B should be further investigated to understand polymyxin B-induced stress in P. aeruginosa.

PREPARATION, PHYSICAL CHARACTERIZATION, AND PHARMACOKINETIC STUDY OF DOCETAXEL NANOCRYSTALS

Objective: The main objective of this study was to prepare and evaluate the nanocrystal formulation of docetaxel.
 Methods: Docetaxel nanocrystals were formulated to improve the water solubility. Docetaxel nanocrystals were prepared by nanoprecipitation method using Tween 80, egg lecithin, and povidone C-12 as stabilizers and poly(lactic-co-glycolic acid) (PLGA) as polymer in acceptable limits. A total of 16 formulations were prepared by changing stabilizer and polymer ratios. The prepared nanocrystals were characterized by particle size, zeta potential, crystalline structure, surface morphology, assay, saturation solubility, and in vitro drug release.
 Results: Based on particle size, polydispersity index, and zeta potential data, four formulations were optimized. The formulation containing Tween 80 as stabilizer has shown lowest particle size and better drug release than the formulations containing egg lecithin and povidone C-12 as stabilizers. The formulation containing Tween 80 and PLGA has shown still lower sized particles than the Tween 80 alone and exhibited prolonged sustained drug release. The release kinetics of formulations containing Tween 80 and PLGA followed zero-order release kinetics and formulations containing egg lecithin and povidone C-12 followed Higuchi diffusion (non-Fickian).
 Conclusion: From the study, we concluded that as the type and concentration of stabilizer changed the size and shape of the crystals were also changed and the formulations showed sustained drug release with non-Fickian diffusion.

High-throughput computational pipeline for 3-D structure preparation and in silico protein surface property screening: A case study on HBcAg dimer structures

Knowledge-based experimental design can aid biopharmaceutical high-throughput screening (HTS) experiments needed to identify critical manufacturability parameters. Prior knowledge can be obtained via computational methods such as protein property extraction from 3-D protein structures. This study presents a high-throughput 3-D structure preparation and refinement pipeline that supports structure screenings with an automated and data-dependent workflow. As a case study, three chimeric virus-like particle (VLP) building blocks, hepatitis B core antigen (HBcAg) dimers, were constructed. Molecular dynamics (MD) refinement quality, speed, stability, and correlation to zeta potential data was evaluated using different MD simulation settings. Settings included 2 force fields (YASARA2 and AMBER03) and 2 pKa computation methods (YASARA and H++). MD simulations contained a data-dependent termination via identification of a 2 ns Window of Stability, which was also used for robust descriptor extraction. MD simulation with YASARA2, independent of pKa computation method, was found to be most stable and computationally efficient. These settings resulted in a fast refinement (6.6–37.5 h), a good structure quality (−1.17–−1.13) and a strong linear dependence between dimer surface charge and complete chimeric HBcAg VLP zeta potential. These results indicate the computational pipeline’s applicability for early-stage candidate assessment and design optimization of HTS manufacturability or formulability experiments.

Removing arsenic from water by coprecipitation with iron: Effect of arsenic and iron concentrations and adsorbent incorporation

Arsenic (As) contamination of drinking water is a major cause of As toxicity in many parts of the world. A study was conducted to evaluate As removal from water containing 100–700 μg/L of As and As to Fe concentration ratios of 1:5–1:1000 using the coprecipitation process with and without As/Fe adsorption onto granular activated carbon (GAC). Fe concentration required to reduce As concentrations in order to achieve the WHO standard level of 10 μg/L increased exponentially with the increase in initial As concentration. When small amounts of GAC were added to the As/Fe solutions the Fe required to remove these As concentrations reduced drastically. This decline was due to the GAC adsorption of Fe and As, enhancing the removal of these metals through coprecipitation. Predictive regression equations were developed relating the GAC dose requirement to the initial As and Fe concentrations. Zeta potential data revealed that As was adsorbed on the GAC by outer-sphere complexation whereas Fe was adsorbed by inner-sphere complexation reversing the negative charge on GAC to positive values. X-ray diffraction of the GAC samples in the presence of Fe had an additional peak characteristic of ferrihydrite (Fe oxide) compared to that of the GAC sample without Fe. The study showed that incorporating an adsorbent into the coprecipitation process has the advantage of removing As from waters at all concentrations of Fe and As compared to coprecipitation alone which does not remove As to the required levels if Fe concentration is low.

Experimentation and modeling of surface chemistry of the silica-water interface for low salinity waterflooding at elevated temperatures

Models predicting wettability alteration of mineral-brine-oil interfaces during low-salinity-waterflooding (LSW) should account for the elevated temperatures typically found in oil reservoirs. For the first time, high temperature ζ-potential (zeta potential) data for silica are collected and used to interpret surface chemistries and interactions at reservoir-like conditions to predict temperature’s effect on wettability alteration. Mobility data for amorphous silica in varying NaCl(aq) concentrations at 25, 100, and 150 °C and neutral pH were obtained through microelectrophoresis experiments. Calculated ζ-potentials were fit with surface complexation model (SCM) parameters to predict electrical double layer (EDL) parameters based upon the Gouy-Chapman-Stern-Grahame (GCSG) model. ζ-potentials increased with increasing temperature (around 50% increase from 25 to 150 °C) and decreasing NaCl concentrations (10−1–10−4 mol kg−1). These trends, along with Derjaguin-Verwey-Landau-Overbeek (DLVO) theory, suggests that overall repulsive forces extend farther from the surface at low salinity and higher temperatures, implying greater wetting thickness/surface wettability in these environments. The resulting surface concentration calculations suggest that LSW is most impactful up to 10−2 mol kg−1 of salt, and that additional dilution below 10−3 mol kg−1 will negligibly impact oil recovery, particularly at reservoir temperatures above 100 °C. The analysis provides a framework for treating more complex reservoir systems, such as carbonates in multivalent brines.

Surface potential study of ceria/poly(sodium 4-styrenesulfonate) aqueous solution interface

The interfacial properties of the system cerium(IV) oxide/poly(sodium 4-styrenesulfonate) (NaPSS) aqueous solution were studied in a broad pH region by means of inner surface potential, zeta potential and adsorption measurements. Surface potential data were obtained using a single crystal electrode, while zeta potential and adsorption data were obtained using synthetized CeO2 nanoparticles. In order to examine the adsorption of NaPSS on cerium(IV) oxide in detail, surface and electrokinetic potentials of ceria particles were measured in the absence and in the presence of NaPSS.The results of surface potential measurements showed that negatively charged NaPSS molecules exhibit high adsorption affinity towards the CeO2 surface. Titration with NaPSS in the acidic region, where the ceria surface is originally positively charged, suggested that adsorption of negatively charged NaPSS molecules compensates positive charge at the surface and adsorption proceeds until the reversal of surface charge produces a critical value of the potential affecting the state of adsorbed NaPSS molecules. Adsorption of NaPSS on cerium(IV) oxide in the examined pH range was additionally confirmed by zeta potential and adsorption measurements in sodium chloride aqueous solution. From the measured pH dependence of the electrokinetic potential of CeO2 nanoparticles, isoelectric point was determined to be pHiep ≈ 5.4, while the electrokinetic potential in the presence of NaPSS was found to be negative in the whole investigated pH region. Finally, adsorption measurements were carried out which enabled the determination of the maximum surface concentration of the adsorbed polyelectrolyte as Γmax ≈ 1 μmol m−2.

Antibiofouling Performance by Polyethersulfone Membranes Cast with Oxidized Multiwalled Carbon Nanotubes and Arabic Gum

Despite extensive research efforts focusing on tackling membrane biofouling, one of the biggest problems associated with membrane technology, there has been little headway in this area. This study presents novel polyethersulfone (PES) membranes synthesized via a phase inversion method at incremental loadings of functionalized oxidized multiwalled carbon nanotubes (OMWCNT) along with 1 wt. % arabic gum (AG). The synthesized OMWCNT were examined using scanning electron microscopy and transmission electron microscopy for morphological changes compared to the commercially obtained carbon nanotubes. Additionally energy-dispersive X-ray spectroscopy was carried out on the raw and OMWCNT materials, indicating an almost 2-fold increase in oxygen content in the latter sample. The cast PES/OMWCNT membranes were extensively characterized, and underwent a series of performance testing using bovine serum albumin solution for fouling tests and model Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacterial species for anti-biofouling experiments. Results indicated that the composite PES membranes, which incorporated the OMWCNT and AG, possessed significantly stronger hydrophilicity and negative surface charge as evidenced by water contact angle and zeta potential data, respectively, when compared to plain PES membranes. Furthermore atomic force microscopy analysis showed that the PES/OMWCNT membranes exhibited significantly lower surface roughness values. Together, these membrane surface features were held responsible for the anti-adhesive nature of the hybrid membranes seen during biofouling tests. Importantly, the prepared membranes were able to inhibit bacterial colonization upon incubation with both Gram-positive and Gram-negative bacterial suspensions. The PES/OMWCNT membranes also presented more resilient normalized flux values when compared to neat PES and commercial membrane samples during filtration of both bacterial suspensions and real treated sewage effluents. Taken together, the results of this study allude to OMWCNT and AG as promising additives, for incorporation into polymeric membranes to enhance biofouling resistance.

Surface Plasmon Resonance, Formation Mechanism, and Surface Enhanced Raman Spectroscopy of Ag+-Stained Gold Nanoparticles.

A series of recent works have demonstrated the spontaneous Ag+ adsorption onto gold surfaces. However, a mechanistic understanding of the Ag+ interactions with gold has been controversial. Reported herein is a systematic study of the Ag+ binding to AuNPs using several in-situ and ex-situ measurement techniques. The time-resolved UV-vis measurements of the AuNP surface plasmonic resonance revealed that the silver adsorption proceeds through two parallel pseudo-first order processes with a time constant of 16(±2) and 1,000(±35) s, respectively. About 95% of the Ag+ adsorption proceeds through the fast adsorption process. The in-situ zeta potential data indicated that this fast Ag+ adsorption is driven primarily by the long-range electrostatic forces that lead to AuNP charge neutralization, while the time-dependent pH data shows that the slow Ag+ binding process involves proton-releasing reactions that must be driven by near-range interactions. These experimental data, together with the ex-situ XPS measurement indicates that adsorbed silver remains cationic, but not as a charged-neutral silver atom proposed by the anti-galvanic reaction mechanism. The surface-enhanced Raman activities of the Ag+-stained AuNPs are slightly higher than that for AuNPs, but significantly lower than that for the silver nanoparticles (AgNPs). The SERS feature of the ligands on the Ag+-stained AuNPs can differ from that on both AuNPs and AgNPs. Besides the new insights to formation mechanism, properties, and applications of the Ag+-stained AuNPs, the experimental methodology presented in this work can also be important for studying nanoparticle interfacial interactions.

Facile polyol synthesis of ultrasmall water-soluble cobalt ferrite nanoparticles

A facile protocol to prepare ultrasmall citrate-coated cobalt ferrite NPs was proposed from the comparison between one-step and two-step chemical routes based on the polyol method. Infrared spectroscopy, thermogravimetry and zeta potential data indicated different coordinations of citrate groups affecting the NP colloidal stability. The magnetic core size and saturation magnetization were also affected. The surface-modified NPs prepared by the one-step route presented superior colloidal stability, low core (2.9 nm) and hydrodynamic (4.8 nm) sizes, high magnetization (45 emu/g), and can be considered suitable platforms to produce nanoparticle-biomolecule conjugates.

СИНТЕЗ ГРАФТ-СОПОЛИМЕРОВ КАРБОКСИМЕТИЛЦЕЛЛЮЛОЗЫ С N-ВИНИЛИМИДАЗОЛОМ И ИССЛЕДОВАНИЕ КИНЕТИКИ ВЫСВОБОЖДЕНИЯ ПРОТИВООПУХОЛЕВОГО ПРЕПАРАТА ПАКЛИТАКСЕЛ ИЗ АССОЦИАТА С СОПОЛИМЕРОМ

Графт-сополимеры карбоксиметилцеллюлозы получены радикальной полимеризацией в растворе в присутствии перекиси водорода. Сополимеры охарактеризованы методами ИК- УФ-спектороскопии, гель-проникающей хроматографией и статическим светорассеянием. Изучение водных растворов сополимеров методами динамического светорассеяния, лазерного допплеровского микроэлектрофореза и просвечивающей электронной микроскопии показало, что частицы сополимеров имеют несферическую форму и характеризуются совокупным отрицательным зарядом частиц. Установлено, что взаимодействие между частицами сополимеров и Паклитакселом в водном растворе носит физический характер. Кинетика высвобождения препарата из комплекса с сополимером описывается кинетической моделью Корсмейера-Пеппаса и не подчиняется законам Фика.
 
 Данные ИК-спектроскопии, просвечивающей электронной микроскопии, лазерного допплеровского микроэлектрофореза получены на оборудовании Центра коллективного пользования научного оборудования ВГУ.

Predicting the electrokinetic properties of the crude oil/brine interface for enhanced oil recovery in low salinity water flooding

The low-salinity waterflooding (LSWF) technique during enhanced oil recovery has received increasing attention over the last decade. Several studies have attempted to understand the effects of LSWF through both experiments and modelling, but their results are inconsistent due to a lack of understanding of the crude oil/brine and brine/rock interfaces. In this paper, the crude oil/brine interface was studied by developing a triple-layer surface complexation model. The carboxyl groups (–COOH) were attributed to the surface charge and electrical triple-layer development of the crude oil in LSWF. The zeta potentials of the emulsion at various pH levels and the calcium and magnesium concentrations were measured to examine the interface. These data were then directly fitted to the simulated zeta potentials to determine the surface site density of –COOH and the associated equilibrium constants for the dissociation and adsorption of calcium and magnesium. The –COOH site density was determined by fitting the pH-independent zeta potential, while the equilibrium constant values were estimated from the variations in the zeta potential with the changes in pH and the concentrations of calcium and magnesium. The determined surface complexation parameters were validated by comparing the experimental zeta potential data from different ionic solutions. The developed surface complexation model was used along with the estimated parameters to predict the interface of crude oil in seawater, formation water, and their dilutions. The simulated zeta potential results agreed well with the experimental data, demonstrating that the model is applicable to understand the crude oil/brine interface in LSWF. Finally, the importance of the prediction of the surface and zeta potentials in the evaluation of the interface and the estimation of electrostatic forces, and thus the wettability alteration, was discussed.

Interaction of green silver nanoparticles with model membranes: possible role in the antibacterial activity.

Silver nanoparticles (AgNPs) constitute a very promising approach for overcoming the emergence of antibiotic resistance bacteria. Although their mode of action could be related with membrane damage, the AgNPs-lipid membrane interaction is still unclear. In this sense, the present work investigated the interaction of model lipid membranes with AgNPs coated with different capping agents such as citrate (C-AgNPs) and phytomolecules (G-AgNPs) obtained via a green synthesis. The AgNPs-membrane interactions were evaluated studying i) the surface pressure changes on both zwitterionic (DMPC) and negatively charged (DMPC:DMPG) lipid monolayers, ii) the zeta potential and DLS of DMPC:DMPG liposomes and iii) Zeta potential on Escherichia coli membranes, incubated with this nanomaterials. The results showed that both negatively charged-AgNPs can interact with these lipid monolayers inducing an increase in the surface pressure but G-AgNPs presented a significantly higher affinity toward both monolayers in comparison with C-AgNPs. Zeta potential data confirmed again the interaction event showing that both DMPC:DMPG liposomes and E. coli bacteria became more negative with the addition of G-AgNPs. This increased net negative charge of the liposomes and E. coli allows to indicate an interfacial interaction where the green nanometal should keep adsorbed to the membrane via the insertion of aromatic/hydrophobic moieties of capping agents on the surface of AgNPs into the lipid bilayer. Summarizing, the AgNPs-membrane interaction should be an essential step in the antibacterial activity either because the membrane is the main target or by increasing the local concentration of silver from G-AgNPs accumulation which could cause the bactericidal effect.

Colloidal Behavior of Cellulose Nanocrystals in Presence of Sodium Chloride

AbstractAggregation and gelation of cellulose nanocrystals (CNCs) induced by sodium chloride (NaCl) were investigated as a function of NaCl and CNC concentrations. Incorporation of NaCl improved CNCs ability to form clusters via screening surface charges of CNCs. Transmission electron microscopy (TEM) images revealed the formation of porous CNC clusters following NaCl addition. The confocal laser scanning microscopy (CLSM) micrographs indicated the presence of regions with colloid‐rich and colloid‐poor patterns in CNC clusters. Fluorescent brightener 28 was found to have a strong hydrogen bonding to the cellulose surface and used as the staining agent in CLSM. The CLSM images also indicated a dynamic structure for gels, continually rearranging over the course of time. Zeta potential data coupled with CLSM images confirmed the impact of NaCl on the gel formation of CNCs.

Mixed hemimicelle solid-phase extraction based on magnetic halloysite nanotubes and ionic liquids for the determination and extraction of azo dyes in environmental water samples

An effective and greener mixed hemimicelles magnetic solid phase extraction (MHMSPE) based on magnetic halloysite nanotubes (MHNTs) and ionic liquid (IL) is developed for the simultaneous enrichment and determination of anionic azo dyes in a spiked environmental water sample. In this MHMSPE, the formation of C16mimBr with mixed hemimicelles on the surface of MHNTs leads to the retention of analytes by strong hydrophobic, p-p and electrostatic interactions. This MHMSPE technique combines the advantages of MHNTs and mixed hemimicelles. Zeta potential data demonstrated that mixed hemimicelles were formed in [C16mimBr]/[MHNTs] ratios of the range from 0.15 to 1.33. Different important factors affecting the preconcentration of analytes were investigated and optimized by response surface methodology and one variable at a time. Under the optimum conditions, the limits of detection (LOD) for methyl red and methyl orange (MR and MO) were 0.042 and 0.050 μg L−1 in samples, respectively. The accuracy of the method was assessed by recovery measurements on a spiked sample, and good recoveries 85–87% for MR and 89–93% for MO, with preconcentration factors of 481 and 524, respectively. The low relative standard deviations from 1.6–3.1% for tap water and 2.5–5.4% for lake water was achieved. So far as we know, this is the first development of a mixed hemimicelles SPE based on MHNTs and IL for the extraction of trace anionic azo dyes in environment water samples.

Dispersion and densification of nano Si–(Al)–C powder with amorphous/nanocrystalline bimodal microstructure

AbstractThe dispersion behavior and densification of nano Si–(Al)–C powder with amorphous/nanocrystalline bimodal microstructure were investigated. The Si–C powders synthesized by a mechanical alloying (MA) process had a near‐spherical shape with an average particle size of 170 nm. A solid loading of 62 vol% was achieved using polyethyleneimine (PEI) as a dispersant. The optimum dispersant amount was 1 wt% based on zeta potential, sedimentation, and viscosity analysis data. The high zeta potential value (73 mV) compared with that of the commercially available SiC (65 mV) was caused by modified surface properties and consequent promotion of the cationic dispersant adsorption. A Si–Al–C slurry containing 6.5 wt% of sintering additives with a solid loading of 60 vol% was also prepared. The relative density of the dried Si–Al–C slurry was 63.3% without additional compaction, which could be densified at 1650°C at a pressure of 20 MPa using a spark plasma sintering furnace.

Incorporation of mRNA in Lamellar Lipid Matrices for Parenteral Administration.

Insertion of high molecular weight messenger RNA (mRNA) into lyotropic lipid phases as model systems for controlled release formulations for the mRNA was investigated. Low fractions of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) were used as an anchor to load the mRNA into a lamellar lipid matrix. Dispersions of zwitterionic lipid in the aqueous phase in the presence of increasing fractions of mRNA and cationic lipid were prepared, and the molecular organization was investigated as a function of mRNA and cationic lipid fraction. Insertion of both cationic lipid and mRNA was clearly proven from the physicochemical characteristics. The d-spacing of the lipid bilayers, as determined by small-angle X-ray scattering (SAXS) measurements, responded sensitively to the amount of inserted DOTAP and mRNA. A concise model of the insertion of the mRNA in the lipid matrices was derived, indicating that the mRNA was accommodated in the aqueous slab between lipid bilayers. Depending on the DOTAP and mRNA fraction, a different excess of water was present in this slab. Results from further physicochemical characterization, including determination of free and bound mRNA, zeta potential, and calorimetry data, were in line with this assumption. The structure of these concentrated lipid/mRNA preparations was maintained upon dilution. The functionality of the inserted mRNA was proven by cell culture experiments using C2C12 murine myoblast cells with the luciferase-encoding mRNA. The described lipid phases as carriers for the mRNA may be applicable for different routes of local administration, where control of the release kinetics and the form of the released mRNA (bound or free) is required.

Flocculation characteristics of a biodegradable polymer based on dextran

Abstract The flocculation efficiency of a cationic polysaccharide with 1-(2-hydroxypropyl)-3-methyl imidazolium chloride groups attached to dextran (D40-MeIm36) was evaluated on synthetic wastewaters containing either inorganic particles (Zirconium silicate (kreutzonit), Kfeldspar, TiO2) or organic ones (pesticides (Decis) and (Dithane M45)). The effect of polymer dose, medium pH, its composition and contaminant concentration on the separation efficacy was followed by UV–Vis spectroscopy measurements. The interactions between D40-MeIm36 and inorganic particles led to maximum removal efficiency (of around 95%), irrespective of the medium pH and composition. The negative values of the zeta potential, at the optimum polymer doses, point to charge patch as mechanism for the particles flocculation. A good efficiency of D40-MeIm36 in separation of pesticides has been noticed; the maximum removal percent slightly increased with increasing pesticide concentration, namely, from 85% at c (v/v) = 0.01% to 92% – 94% for c (v/v) = 0.02% and 0.04% for Decis and from around 85% at c = 0.1 g L−1 to 89% at c = 0.2 g L−1 for Dithane M45. A minimum residual pesticide absorbance of about 10% has been recorded for both pesticides, at the established medium pH. Zeta potential and particle aggregates size data plead for the charge neutralization as the dominant mechanism for the flocculation of pesticide particles.