Charged Polystyrene Latex Research Articles

Influence of Concentration, Surface Charge, and Natural Water Components on the Transport and Adsorption of Polystyrene Nanoplastics in Sand Columns.

Information about the influence of surface charges on nanoplastics (NPLs) transport in porous media, the influence of NPL concentrations on porous media retention capacities, and changes in porous media adsorption capacities in the presence of natural water components are still scarce. In this study, laboratory column experiments are conducted to investigate the transport behavior of positively charged amidine polystyrene (PS) latex NPLs and negatively charged sulfate PS latex NPLs in quartz sand columns saturated with ultrapure water and Geneva Lake water, respectively. Results obtained for ultrapure water show that amidine PS latex NPLs have more affinity for negatively charged sand surfaces than sulfate PS latex NPLs because of the presence of attractive electrical forces. As for the Geneva Lake water, under natural conditions, both NPL types and sand are negatively charged. Therefore, the presence of repulsion forces reduces NPL's affinity for sand surfaces. The calculated adsorption capacities of sand grains for the removal of both types of NPLs from both types of water are oscillating around 0.008 and 0.004 mg g-1 for NPL concentrations of 100 and 500 mg L-1, respectively. SEM micrography shows individual NPLs or aggregates attached to the sand and confirms the limited role of the adsorption process in NPL retention. The important NPL retention, especially in the case of negatively charged NPLs, in Geneva Lake water-saturated columns is related to heteroaggregate formation and their further straining inside narrow pores. The presence of DOM and metal cations is then crucial to trigger the aggregation process and NPL retention.

Particle Adsorption Using a Quartz Crystal Microbalance with Dissipation by Applying a Kelvin-Voigt-Based Viscoelastic Model and the Gauss-Newton Method.

The use of a quartz crystal microbalance with dissipation (QCM-D) to study the adsorption of particles larger than 100 nm, such as liposomes, viruses, and nano/micro-plastics, remains challenging owing to the lack of appropriate models for data evaluation. This study presents a method for quantifying the adsorption of negatively charged polystyrene latex (100 nm-1 μm) at the solid-liquid interface. The validity of a viscoelastic model based on Kelvin-Voigt theory was assessed, and the model was used to evaluate particle adsorption data obtained from QCM-D measurements. The Gauss-Newton method was used to fit the data; the values obtained were larger than results from atomic force microscopy, indicating that the viscoelastic model combined with the Gauss-Newton method can quantify the adsorption of large polystyrene particles and the surrounding water around them. We suggested that QCM-D, in combination with an appropriate viscoelastic model, is applicable to estimate adsorption at the solid-liquid interface even for soft particles larger than 1 μm, which are out of the range of applications to the hydrodynamics model. Furthermore, we successfully showed that the recorded dissipation reflects the viscoelastic properties of the layer. The viscoelastic model allowed quantification of the rheological properties of the layer. The ratio of the viscous and elastic contributions was characterized by using loss tangent (tan δ) values that were extracted from the experimental data by applying the viscoelastic model. These values were lower for the adsorption of the negatively charged polystyrene particles on a positive surface than on a negative surface. This suggests that tan δ reflects the strength of the contact between the particle and substrate.

A high resolution differential mobility analyzer for the study of large virus particles

The conical inner electrode of a recently described differential mobility analyzer (DMA), covering at resolution >50 the size range up to 60 nm, has been modified by increasing its radius at the outlet slit from 1 cm to 1.6 cm, and decreasing its convergence angle from 3° to 0.5°. The cylindrical outer electrode radius is maintained at 2 cm, while other critical dimensions are only slightly modified. The classification voltage for fixed flow rate of sheath gas and particle diameter decreases almost fourfold, extending the size range theoretically spanned at high resolution well beyond 120 nm. Tests with multiply charged polystyrene latex spheres 200 nm in diameter confirm the actual ability to cover this wide size range. A resolution above 100 (with no corrections for instrument or particle nonidealities) is demonstrated with rotavirus double-layered particles (DLP) whose mobility diameter is found to be near 60 nm. The DLP has several configurations that complicate its use for DMA characterization, but occasionally presents mainly one conformer, with singularly narrow relative mobility width FWHM < 1/150. Two broad range instruments with slightly different axial lengths have been developed and tested, both reaching resolving powers of 100.

The inhibitory effects of synthetic polyacrylic acid and humic substances on the initial stage of colloidal flocculation induced by polycationic flocculant with low charge density

Humic substances (HS) coexisting with colloidal particles are inevitable in water bodies. Since the cationic flocculant used for flocculation treatment in such water bodies interacts electrostatically with HS and colloidal particles, the efficiency of the flocculant tends to be lower than in water bodies containing only colloidal particles. The colloidal flocculation mechanism by polycation with low charge density is dominated by bridging effects rather than charge neutralization effects. Furthermore, the polyionic complex formation of low charge density polycations with HS is not stoichiometric, based on the oppositely charged groups. Therefore, it was unclear how HS affects the flocculation of colloidal particles by polycation with low charge density. In this study, the effects of two naturally occurring HS and two synthetic polyanions on the flocculation behavior of negatively charged polystyrene latex (PSL) particles induced by polycationic flocculant with low charge density (4 %) were investigated under standardized mixed fluid conditions. Considering the flocculation inhibition effect in terms of the molar concentration ratio of flocculant-derived cations to polyanion-derived anions, it was found that polyanions less inhibit the flocculation of PSL particles by flocculant with low charge density compared to flocculant with high charge density. The relationship between the degree of inhibition of flocculation and the affinity of polyanions for polycations obtained from electrophoretic mobility experiments was verified, and the effectiveness of using low charge density polycations as particle flocculants in water bodies containing particles and HS was discussed.

Analysis of initial stage of colloidal particles flocculation induced by different degree branching polyelectrolytes

Flocculation performance of polyelectrolytes is affected by their molecular branching. To unravel the mechanisms involved, we performed flocculation experiments of negatively charged polystyrene latex particles using three cationic polyacrylamide-based polyelectrolytes differing only in the degree of molecular branching. In the experiment, a simple linear chain molecule and two branched polyelectrolytes were tested. The initial rate of flocculation under the condition of standardized mixing, the value of resulted electrophoretic mobility of particles coated with polyelectrolytes, and their hydrodynamic layer thickness by means of particle tracking of Brownian motion were monitored to compare the effect of branching degree. The rate of flocculation was found to increase with an increase in the degree of branching, as corresponding to the hydrodynamic adsorbed layer thickness. These results suggested the importance of the relaxation process polymer chain from coil-like solution conformation to flattened adsorbed state on the surface of colloidal particles. Branched polymers retain their shape after arriving on the surface due to the presence of branches that disturb smooth movement resulting in slow relaxation on the surface of the colloidal particle. Subsequently, forming thick adsorbed layer and enhances the rate of flocculation. Thus, explaining the commonly observed trend where branched polymers achieve better flocculating abilities than linear ones.

The Toxicity of Polystyrene-Based Nanoparticles in Saccharomyces cerevisiae Is Associated with Nanoparticle Charge and Uptake Mechanism.

Polystyrene latex (PSL) nanoparticles (NPs), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes, and hybrid NPs that have different concentrations, sizes, surface charges, and functional groups were used to determine their toxicity to Saccharomyces cerevisiae cells. The size, charge, and morphology of the nanoparticles were characterized by dynamic light scattering, electrophoretic light scattering, scanning transmission electron microscopy, and transmission electron microscopy analysis. The cell viabilities were determined by colony forming unit analysis and confocal laser scanning microscopy imaging. Uptake inhibition studies were performed to determine the internalization mechanism of PSL NPs. At 50 mg/L, both positively and negatively charged NPs were slightly toxic. With increasing concentration, however, full toxicities were observed with positively charged PSL NPs, while a marginal increase in toxicity was obtained with negatively charged PSL NPs. For negatively charged and carboxyl-functionalized NPs, an increase in size induced toxicity, whereas for positively charged and amine-functionalized NPs, smaller-sized NPs were more toxic to yeast cells. Negatively charged NPs were internalized by the yeast cells, but they showed toxicity when they entered the cell vacuole. Positively charged NPs, however, accumulated on the cell surface and caused toxicity. When coated with DOPC liposomes, positively charged NPs became significantly less toxic. We attribute this reduction to the larger-diameter and/or more-agglomerated NPs in the extracellular environment, which resulted in lower interactions with the cell. In addition to endocytosis, it is possible that the negatively charged NPs (30-C-n) were internalized by the cells, partly via direct permeation, which is preferred for high drug delivery efficiency. Negatively charged PSL NP exposure to the yeast cells at low-to-moderate concentrations resulted in low toxicities in the long term. Our results indicate that negatively charged PSL NPs provide safer alternatives as cargo carriers in drug delivery applications. Moreover, the variations in NP size, concentration, and exposure time, along with the use of hybrid systems, have significant roles in nanoparticle-based drug delivery applications in terms of their effects on living organisms.

Heteroaggregation between Charged and Neutral Particles.

Experimentally determined heteroaggregation rates between charged and neutral colloidal particles are reported for the first time. Different positively and negatively charged polystyrene latex particles are investigated. The neutral particles are obtained through adsorption of an appropriate amount of oppositely charged additives, such as aliphatic oligoamines, iron cyanide complexes, or alkyl sulfates. Heteroaggregation rates were measured with time-resolved multiangle light scattering. One observes that heteroaggregation between charged and neutral particles is always fast and diffusion controlled. These experimental values are compared with calculations of the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory, whereby one finds that this heteroaggregation process is highly sensitive to charge regulation conditions. The comparison with experiments shows unambiguously that the surface of the neutral particles regulates strongly and probably behaves close to a constant potential surface. This observation is in line with direct force measurements on similar systems and further agrees with the fact that for neutral surfaces the capacitance of the diffuse layer is expected to be much smaller than the one of the inner layer.

Influence of the Counterion Nature on the Stability Sequence of Hydrophobic Latex Particles.

The aggregation kinetics of negatively charged polystyrene latex particles in the presence of monovalent electrolytes have been investigated. The inferred coagulation critical concentrations were compared to establish the stability sequence. With the same representative co-ions, this sequence is reversed when using kosmotrope sodium and chaotrope potassium cations. The results have been ascribed to a variable competition of the co-ions toward the hydrophobic surface depending on the lyotropic nature of the associated counterion. They provide new insights into the implication of ionic specificity in the stability behavior of aqueous dispersions of charged colloids.

Direct measurements of colloidal behavior of polystyrene nanoparticles into budding yeast cells using atomic force microscopy and confocal microscopy

The colloidal behavior of positively charged polystyrene latex (PSL) nanoparticles (NPs) toward yeast cells (Saccharomyces cerevisiae) was investigated using atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). AFM imaging revealed that the conically-shaped pits connected with endocytosis were observed in 154 mM NaCl, and the surface was completely covered with NPs within 60 s in 5 mM NaCl. AFM force measurements revealed that the adhesion rate of NPs in 5 mM NaCl was faster than that in 154 mM NaCl. This strongly suggested that in 5 mM NaCl, the NPs accumulated on the cell surface over a short time followed by cell death. Furthermore, the accumulation of NPs on the cell surface in 5 mM NaCl could be suppressed by adding polyethylene glycol to the medium, resulting in an increase in the number of living cells. This suggests that the adhesion rate of NPs primarily depended on the interaction forces between the surfaces, and the viscosity of the medium. Thus, the colloidal behavior of the positively charged PSL NPs toward yeast cells was controlled by the balance between the adhesion rate of NPs on the cells and the uptake rate of NPs into the cells. Additionally, the uptake of the PSL NPs and an endocytosis marker into the cells was inhibited by Latrunculin B and NaN3. However, their locations without inhibitor treatment were obviously different, indicating that NPs were not transported to the vacuole and accumulated in the vesicles.

Control of colloidal behavior of polystyrene latex nanoparticles and their cytotoxicity toward yeast cells using water-soluble polymers

Positively charged polystyrene latex (PSL) nanoparticles (NPs) dispersed in physiological saline (154 mM NaCl solution) are taken up by yeast cells. However, in low ionic strength solutions, the yeast cells are covered with the NPs, leading to cell death. The environmental conditions under which NPs are taken up are therefore limited. In this study, we attempted to control the uptake of positively charged PSL NPs by Saccharomyces cerevisiae in 5 mM NaCl solution using a water-soluble polymer. Addition of a small amount of anionic sodium carboxymethylcellulose (CMC), which has a carboxyl group, to 5 mM NaCl solution allowed the uptake of PSL NPs by living yeast cells. In contrast, non-ionic methylcellulose did not affect the NP behavior. This is because the negatively charged CMC adhered to the positively charged PSL NP surfaces and the surface charge changed from positive to negative. Atomic force microscopy using a single-NP probe consisting of one NP immobilized on the flattened end of the silicon nitride tip showed that CMC significantly reduced the interaction force between a negatively charged living yeast cell and a positively charged PSL NP.

On the Size‐Determining Role of the Comonomer in the Nucleation and Growth of Cationic Polystyrene Latex via Emulsion Polymerization

AbstractThe formation of positively charged polystyrene latex particles via the surfactant‐free emulsion polymerization of styrene with cationic initiator is investigated. Using the comonomer (vinylbenzyl)trimethyl‐ammonium chloride (VBTMAC) it is shown that the particle size can be tuned rather precisely between above 350 nm and below 70 nm. The simple functional dependence of the particle size on the inverse cube root of the comonomer concentration leads to propose, with reasonable assumptions, that VBTMAC comonomer addition allows the separation of nucleation and growth for this reaction. Thereby the comonomer concentration determines the nucleation rate and number of particles produced, while the styrene amount determines by how much the nucleated particles grow. Support for this model is obtained through zeta potential measurements at different pH values. The latter confirmed that the surface density of cationic groups resulting from the comonomer relative to that of groups resulting from the initiator decreases with decreasing comonomer concentration.

Synthesis and properties of latex particles with polyaniline shells

Core–shell polyaniline–latex particles have been obtained via oxidative polymerization of aniline hydrochloride in the presence of charged polystyrene latex. The polymerization conditions have been determined under which polyaniline is predominantly formed on the surface of latex particles to yield closed shells. The dependence of the electrical conductivity of the resulting particles on the initial concentration of aniline hydrochloride in the polymerization medium has been studied. Stable aqueous dispersions of polyaniline–latex particles have been prepared by modifying the particles with sodium 3-mercaptopropane sulfonate.

Comparative Study of the Effect of Aluminum Chloride, Sodium Alginate and Chitosan on the Coagulation of Polystyrene Micro-Plastic Particles

The coagulation of negatively charged polystyrene latex micro-plastic particles is studied in presence of two linear biopolymers (chitosan and sodium alginate) and a trivalent salt, aluminum chloride as coagulants. The performance of the different coagulants, impact of the solution pH, and use of alginate as a coagulant in presence of aluminum chloride, fractal character and compactness of aggregates are investigated by using mainly electrophoretic experiments and image analysis. The coagulant efficiency and coagulation routes and strategies are analyzed by considering the variations of the particle surface charges at variable coagulant concentrations. Optimal coagulant dosage is determined when the surface charge of the latex particle is neutralized. Our results suggest that the biopolymers are in some cases more efficient than AlCl3 for the destabilization of latex micro-plastic particles. Indeed, charge neutralization is more rapidly achieved by chitosan regarding the optimal dosage and chitosan is found to work over a wider range of pH values. Alginate is also found to be a good candidate when particle charge inversion is achieved first with aluminum chloride. We also demonstrate that coagulant dosage is dependent on the initial pH of the suspension. When the initial pH of the dispersion is low, the isoelectric point is obtained for small dosage values. Image analysis indicates that in all situation fractal aggregates are obtained and that biopolymers result in the formation or more compact structures which will increase the sedimentation rates.

Comparison of the cytotoxic effect of polystyrene latex nanoparticles on planktonic cells and bacterial biofilms

The cytotoxic effect of positively charged polystyrene latex nanoparticles (PSL NPs) was compared between planktonic bacterial cells and bacterial biofilms using confocal laser scanning microscopy, atomic force microscopy, and a colony counting method. Pseudomonas fluorescens, which is commonly used in biofilm studies, was employed as the model bacteria. We found that the negatively charged bacterial surface of the planktonic cells was almost completely covered with positively charged PSL NPs, leading to cell death, as indicated by the NP concentration being greater than that required to achieve single layer coverage. In addition, the relationship between surface coverage and cell viability of P. fluorescens cells correlated well with the findings in other bacterial cells (Escherichia coli and Lactococcuslactis). However, most of the bacterial cells that formed the biofilm were viable despite the positively charged PSL NPs being highly toxic to planktonic bacterial cells. This indicated that bacterial cells embedded in the biofilm were protected by self-produced extracellular polymeric substances (EPS) that provide resistance to antibacterial agents. In conclusion, mature biofilms covered with EPS exhibit resistance to NP toxicity as well as antibacterial agents.

Cytotoxicity and colloidal behavior of polystyrene latex nanoparticles toward filamentous fungi in isotonic solutions

The effects of surface physicochemical properties of functionalized polystyrene latex (PSL) nanoparticles (NPs) and model filamentous fungi Aspergillus oryzae and Aspergillus nidulans cultivated in different environment (aqueous and atmospheric environment) on the colloidal behavior and cytotoxicity were investigated in different isotonic solutions (154 mM NaCl and 292 mM sucrose). When the liquid cultivated fungal cells were exposed to positively charged PSL NPs in 154 mM NaCl solution, the NPs were taken into A. oryzae, but not A. nidulans. Atomic force microscopy revealed that the uptake of NPs was more readily through the cell wall of A. oryzae because of its relatively softer cell wall compared with A. nidulans. In contrast, the positively charged PSL NPs entirely covered the liquid cultivated fungal cell surfaces and induced cell death in 292 mM sucrose solution because of the stronger electrostatic attractive force between the cells and NPs compared with in 154 mM NaCl. When the agar cultivated fungal cells were exposed to the positively charged PSL NPs, both fungal cells did not take the NPs inside the cells. Contact angle measurement revealed that the hydrophobin on the agar cultivated cell surfaces inhibited the uptake of NPs because of its relatively more hydrophobic cell surface compared with the liquid cultivated cells.

Interaction Forces and Aggregation Rates of Colloidal Latex Particles in the Presence of Monovalent Counterions.

Force profiles and aggregation rates involving positively and negatively charged polystyrene latex particles are investigated in monovalent electrolyte solutions, whereby the counterions are varied within the Hofmeister series. The force measurements are carried out with the colloidal probe technique, which is based on the atomic force microscope (AFM), while the aggregation rates are measured with time-resolved multiangle light scattering. The interaction force profiles cannot be described by classical DLVO theory, but an additional attractive short-ranged force must be included. An exponential force profile with a decay length of about 0.5 nm is consistent with the measured forces. Furthermore, the Hamaker constants extracted from the measured force profiles are substantially smaller than the theoretical values calculated from dielectric spectra. The small surface roughness of the latex particles (below 1 nm) is probably responsible for this deviation. Based on the measured force profiles, the aggregation rates can be predicted without adjustable parameters. The measured absolute aggregation rates in the fast regime are somewhat lower than the calculated ones. The critical coagulation concentration (CCC) agrees well with the experiment, including the respective shifts of the CCC within the Hofmeister series. These shifts are particularly pronounced for the positively charged particles. However, the consideration of the additional attractive short-ranged force is essential to quantify these shifts correctly. In the slow regime, the calculated rates are substantially smaller than the experimental ones. This disagreement is probably related to surface charge heterogeneities.

High density monolayers of plasmid protein on latex particles: experiments and theoretical modeling

Monolayers obtained by adsorption of the plasmid protein KfrA on negatively charged polystyrene latex particles under diffusion-controlled conditions at pH 3.5 were interpreted in terms of the random sequential adsorption (RSA) model. A quantitative agreement of the theoretical results derived from these calculations with experimental data was attained for the ionic strength from 0.15 up to 10−2 M. This confirmed the adsorption mechanism of KfrA molecules on latex in the form of tetramers up to 10−2 M. On the other hand, for the ionic strength of 10−3 M the experimental coverage agreed with theoretical predictions under the assumption that screening of electrostatic interaction is enhanced by the presence of counterions and negatively charged polymer chains stemming from latex particles.

Mapping single macromolecule chains using the colloid deposition method: PDADMAC on mica

Monolayers of the cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDADMAC) on mica were thoroughly characterized using the streaming potential and the colloid deposition methods. Initially, the stability of the monolayers was determined by performing desorption experiments carried out under diffusion-controlled regime. It was shown that the desorption of the polyelectrolyte at the ionic strength range 0.01–0.15M is negligible over the time of 20h. The structure of PDADMAC monolayers and orientation of molecules were evaluated using the colloid deposition measurements involving negatively charged polystyrene latex microspheres, 820nm in diameter. The functional relationships between the polyelectrolyte coverage and latex coverage deposited within 20h were acquired by direct optical microscope. In this way the influence of ionic strength varied in the range 0.15–0.01M on the molecule orientation in monolayers was determined. It was shown that for ionic strength of 0.15M nearly one to one mapping of polyelectrolyte chains by colloid particles can be achieved for PDADMAC coverage below 0.1%. In this way, because of a considerable surface area ratio between the macromolecule and the colloid particle, an enhancement factor of 103 can be attained. This behavior was quantitatively interpreted in terms of the random site adsorption model whereas the classical mean-field theory proved inadequate. On the other hand, for lower ionic strength, it was confirmed that an irreversible immobilization of latex particles can only occur at a few closely spaced PDADMAC chains. It was shown that these experimental results were consistent with the side-on adsorption mechanisms of PDADMAC at mica for the above ionic strength.

Cytotoxicity of functionalized polystyrene latex nanoparticles toward lactic acid bacteria, and comparison with model microbes

The cytotoxicity and colloidal behavior of surface-functionalized polystyrene latex (PSL) nanoparticles (NPs) (nominal diameter: 100 nm) toward a model gram positive bacterium Lactococcus lactis JCM 5805 were examined. Nearly all the L. lactis cells exposed to the negatively charged PSL NPs survived because the surface of the bacterial cell was charged negatively, and the NPs therefore hardly adhere to the cell surface. In contrast, the positively charged PSL NPs adhered to the L. lactis cell surface but were not entrapped within the cell, and cell death subsequently occurred. The bacterial growth curves after the toxic NP exposure suggested that NP toxicity did not affect the specific growth phase, but did affect lag time. These results indicated that the cells were damaged by the cell disruption that resulted from the adhesion of the NPs to the cell surface. Finally, the cytotoxicity of the toxic, positively charged PSL NPs toward L. lactis was compared with that displayed toward a model gram negative bacterium Escherichia coli and a model eukaryote Saccharomyces cerevisiae. The cytotoxic behaviors of NPs on L. lactis and E. coli were similar, and depended not on the bacterial surface structure, but rather the environmental ionic strength. In contrast, the cytotoxicity of the prokaryote bacteria was higher than that toward the model eukaryote S. cerevisiae. The difference between the NP sensitivities of the prokaryote and eukaryote resulted from the prokaryote’s lack of an endocytotic pathway.

Cytotoxicity and behavior of polystyrene latex nanoparticles to budding yeast

The cytotoxicity and behavior of positively charged amine-modified polystyrene latex nanoparticles (NPs) toward budding yeast cells were examined in different environments. The yeast cells, dispersed in either 27.8 mM glucose or low-ionic strength aqueous electrolyte solution, were covered with NPs regardless of the ionic species or diameter of the NPs. The NPs that adhered to the cell surface showed high toxicity. The cell viability following NP exposure increased with the NaCl concentration independently of the glucose concentration in the dispersion medium. Therefore, the strong electrostatic attraction between the negatively charged yeast cells and positively charged NPs resulted in NP adhesion to the cell surface and subsequent cell death. However, the amount of endocytosis-like NPs inside the cell, dispersed in the hypertonic solution, was lower than that in the isotonic solution. These results indicate that the osmotic pressure affects the uptake of NPs rather than the cell viability. In contrast, NPs dispersed in a high-ionic strength electrolyte solution with a diameter of ∼100 nm or less were absorbed by the yeast cells. NPs incorporated in the living yeast cells showed little toxicity.