Polyelectrolyte Complex Particles Research Articles

A Novel Family of Stable Polyelectrolyte Complexes Based on Mixed Olefins-Maleic Anhydride Copolymer.

In the present study, the copolymer of mixed olefins included in unetherified gasoline and maleic anhydride (PUGM) was prepared by self-stabilized precipitation polymerization (2SP) and employed for the synthesis of a new family of stable polyelectrolyte complexes (PECs). Polyanionic saponified PUGM partially grafted with methoxy poly(ethylene glycol) (PUGMS-g-mPEG) and polycationic quaternized PUGM (PUGMQ) were both derived from PUGM via the facile modification of anhydride groups. The particle size, zeta potential, morphology, and stability of self-assembled PEC particles were investigated thoroughly. Strikingly, the introduction of long mPEG side chains (Mn = 4000) had a remarkable effect on the self-assembled particles, which displayed a constant particle size of ∼200 nm regardless of varying n+/n-. Moreover, it also enhanced the salt tolerance and long-term stability of PEC particles significantly. Our work not only provides an effective approach to PECs from petroleum resources with low cost but also deepens the understanding of the relationship between the chain structure of polyelectrolytes and the stability of PECs.

Specific ion effects on the aggregation of polysaccharide-based polyelectrolyte complex particles induced by monovalent ions within Hofmeister series

Polysaccharide-based polyelectrolyte complex (PEC) particles have been utilized as carriers for drug delivery systems (DDS) and as building components for material development. Despite their versatility, the aggregation mechanism of PEC particles in the presence of salts remains unclear. To clarify the aggregation mechanism, the specific ion effects of monovalent salts within the Hofmeister series on the aggregation behavior of PEC particles composed of chitosan and chondroitin sulfate C, which are often used as DDS carriers and materials, were studied. Here, we found that weakly hydrated chaotropic anions promoted the aggregation of positively charged PEC particles. The hydrophobicity of the PEC particles was increased by these ions. Strongly hydrated ions such as Cl- are less likely to accumulate in these particles, whereas weakly hydrated chaotropic ions such as SCN- are more likely to accumulate. Molecular dynamics simulations suggested that the hydrophobicity of PECs might be strengthened by ions due to changes in intrinsic and extrinsic ion pairs and hydrophobic interactions. Based on our results, it is expected that the control of surface hydrophilicity or hydrophobicity is an effective approach for controlling the stability of PEC particles in the presence of ions.

One-Step Encapsulation of Capsaicin into Chitosan-Oleic Acid Complex Particles: Evaluation of Encapsulation Ability and Stability.

Capsaicin (CAP) demonstrates a potential for application in the food and pharmaceutical industries owing to its various attractive health benefits, including anti-cancer, anti-inflammatory, and antioxidant activities. However, the application of CAP is often limited by its low solubility in water, low bioavailability, and strong pungency. In this study, a simple one-step method for the stable encapsulation and dispersion of CAP in aqueous media was developed using polyelectrolyte complex particles formed by chitosan (CHI) and oleic acid (OA). Homogeneous particles with mean diameters below 1 μm were successfully prepared via spontaneous molecular complexation by mixing an aqueous solution of CHI with an ethanolic solution of OA and CAP. CAP was incorporated into the hydrophobic domains of the CHI–OA complex particles through hydrophobic interactions between the alkyl chains of OA and CAP. The factors affecting CAP encapsulation were investigated, and a maximum encapsulation yield of approximately 100% was obtained. The CHI–OA–CAP complex particles could be stored for more than 3 months at room temperature (22–26 °C) without resulting in macroscopic phase separation or degradation of CAP. We believe that our findings provide a useful alternative encapsulation technique for CAP and contribute to expanding its practical application.

Polyelectrolyte complexes of hyaluronic acid and diethylaminoethyl dextran: Formation, stability and hydrophobicity

Polyelectrolyte complexes (PECs) of hyaluronic acid (HA) and diethylaminoethyl dextran (DEAE-D), promising for biomedical applications, have been investigated with respect to physicochemical properties, mainly in terms of particle size and relative hydrophobicity as well as storage stability. Influences of charge ratio, polymer concentration, molar masses of HA, ionic strength and mixing methods have been particularly investigated. The complexation between HA and DEAED generally resulted in colloidal particles having mean hydrodynamic diameter of 150–350 nm, with larger particle size observed at negative to positive charge ratio (n-/n+) further from the unity. Higher polymer concentration or higher molar mass of HA also led to higher particle size of the PECs, whereas the increasing ionic strength led to a non-monotonic evolution in particle size. The effects of mixing mode and mixing order on particle size were interdependent and depended also on n-/n+. PECs at n-/n+ ≤ 0.4 showed lack of stability, which seemed not to be sensitive to storage temperature but significantly improved at higher salt concentration or lower polymer concentration. The relative hydrophobicity of such PECs was also confirmed by the fluorescence spectra of pyrene incorporated in PEC particles. Such results gave a better insight to polysaccharides-based PECs, especially as a potential system to encapsulate hydrophobic active molecules for drug delivery purposes.

Size-Controlled and Shelf-Stable DNA Particles for Production of Lentiviral Vectors.

Polyelectrolyte complex particles assembled from plasmid DNA (pDNA) and poly(ethylenimine) (PEI) have been widely used to produce lentiviral vectors (LVVs) for gene therapy. The current batch-mode preparation for pDNA/PEI particles presents limited reproducibility in large-scale LVV manufacturing processes, leading to challenges in tightly controlling particle stability, transfection outcomes, and LVV production yield. Here we identified the size of pDNA/PEI particles as a key determinant for a high transfection efficiency with an optimal size of 400–500 nm, due to a cellular-uptake-related mechanism. We developed a kinetics-based approach to assemble size-controlled and shelf-stable particles using preassembled nanoparticles as building blocks and demonstrated production scalability on a scale of at least 100 mL. The preservation of colloidal stability and transfection efficiency was benchmarked against particles generated using an industry standard protocol. This particle manufacturing method effectively streamlines the viral manufacturing process and improves the production quality and consistency.

Influence of the Mixing Ratio on the Dynamics of Polymer Segments in Polyelectrolyte Complexes

AbstractThe rotational dynamics of the spin‐labeled polyacid poly(ethylene‐alt‐maleic acid) (P(E‐alt‐MA)) in polyelectrolyte complexes (PECs) formed with the polycations poly(allylamine hydrochloride) (PAH) and poly(diallyldimethylammonium chloride) (PDADMAC) are studied by electron paramagnetic resonance (EPR) spectroscopy as a function of the mixing ratio of polycation and polyanion. At low mixing ratios a superposition of two spectral components is found. The fast‐motion component observed arises from chain segments of the polyacid in excess, which form a stabilizing shell around the PEC particles. The other one is a slow‐motion component, which is caused by the interaction of charged chain segments of the polyacid with the oppositely charged segments of the polycation in the core. At high mixing ratios, the spectra are dominated by the slow‐motion component, because the polyacid is exclusively located in the core. The study has shown that the outer extrema separation of the slow‐motion component decreases with increasing mixing ratio, i.e., the rotational mobility of the polyacid segments in the core increases when the excess of the polycation becomes larger. An increasing number of extrinsic polycation sites within the core of the PECs which reduces the density of intrinsic binding sites are assumed to be the reason.

Adsorption of eosin Y on polyelectrolyte complexes based on chitosan and arabinogalactan sulfate

Positively charged polyelectrolyte complexes (PECs) were synthesized from two polysaccharides chitosan and arabinogalactan sulfate by self-assembly method as potentially efficient adsorbents for medical and environmental purposes. The obtained PEC particles of submicron size were comprehensively characterized by dynamic and electrophoretic light scattering, FTIR spectroscopy and scanning electron microscopy. The adsorption properties of the synthesized PECs were determined by optical methods using eosin Y as a model anionic dye. A temporal evolution of dye absorption spectra was revealed during the equilibration process in the eosin Y-PEC system; the decay can be described by three characteristic times with maximal value of 35 min. The adsorption within the pH range of 3.0–5.6 can be appropriately described by Langmuir-Freundlich model with the maximal adsorption capacity of 500 mg g−1. The increase of ionic strength has no significant effect on adsorption capacity of PECs, however it results in the increase of the heterogeneity factor from 0.82 up to 2.35. The revealed relationships were discussed in terms of predominantly electrostatic adsorbate-adsorbent interactions. The synthesized PECs demonstrated high colloidal stability along with a high removal efficiency of dye at low pH values that makes them very attractive eco-friendly dye adsorbent with improved biocompatibility.

Simulation-based optimisation of thermodynamic conditions in the ESEM for dynamical in-situ study of spherical polyelectrolyte complex particles in their native state

We present a complex analysis and optimisation of dynamic conditions in the environmental scanning electron microscope (ESEM) to allow in-situ observation of extremely delicate wet bio-polymeric spherical particles in their native state. According to the results of gas flow and heat transfer simulations, we were able to develop an improved procedure leading to thermodynamic equilibrium between the sample and chamber environment. To quantify and hence minimise the extent of any sample deformation during specimen chamber pumping, a strength-stress analysis is used. Monte Carlo simulations of beam-gas, -water, and -sample interactions describe beam scattering, absorbed energy, interaction volume and the emission of signal electrons in the ESEM. Finally, we discuss sample damage as a result of drying and the production of beam-induced free radicals. Based on all experimental and simulation results we introduce a Delicate Sample Observation Strategy for the ESEM. We show how this strategy can be applied to the characterization of polyelectrolyte complex spherical particles containing immobilized recombinant cells E. coli overexpressing cyclohexanone monooxygenase, used as a model biocatalyst. We present the first native-state electron microscopy images of the viscous core of a halved polyelectrolyte complex capsule containing living cells.

Emulsions Stabilized with Polyelectrolyte Complexes Prepared from a Mixture of a Weak and a Strong Polyelectrolyte.

The possibility of stabilizing emulsions with polyelectrolyte complexes (PEC) obtained from the interaction of two non-surface-active oppositely charged polyelectrolytes (PEL) is described. Poly(allylamine hydrochloride) (PAH) and poly(4-styrene sulfonate) sodium salt are selected as the weak cationic and the strong anionic polyelectrolyte, respectively. Aqueous polymer mixtures are investigated by light scattering to determine the size of the complexes and whether precipitation or complex coacervation occurs. The effects of PEL mixing ratio, pH, and PEL concentration are studied in detail. By increasing the pH, the transition precipitate-precipitate/coacervate-coacervate-polymer solution is observed. At low pH, both PEL are fully ionized and therefore precipitates (soft particles) arise as a result of strong electrostatic interactions. By increasing the pH, the degree of ionization of PAH decreases and weak electrostatic interactions ensue, supporting the formation of coacervate droplets. The most stable oil-in-water emulsions are prepared from aqueous mixtures around charge neutralization. Although emulsions can be prepared from coacervate droplet dispersions, their coalescence stability is worse than those stabilized by soft PEC particles. By increasing the PEL concentration, the average droplet diameter decreases and the fraction of cream in the emulsion increases for emulsions prepared with PEC particles, following the limited coalescence model. However, at high concentrations, emulsion stability is slightly worse probably due to extensive aggregation of the particles. Viscous high internal phase emulsions can be prepared at low pH in which oil droplets are deformed. Here, PEC particles are detected only at the oil-water interface. At lower oil content, excess particles form a network in the aqueous phase aiding emulsion stability to coalescence.

Synthesis of sphere-like polyelectrolyte complexes and their homogeneous membranes for enhanced pervaporation performances in ethanol dehydration

A series of sphere-like polyelectrolyte complexes (PECs) and their homogeneous polyelectrolyte complex membranes (HPECMs) were synthesized by using sodium carboxymethyl cellulose (CMCNa) and poly(diallyldimethylammonium chloride) (PDDA). Different compositions or ionic complexation degrees (ICD) of PECs could be characterized by FT-IR spectra. The circular dichroism spectrum (CD) and field emission scanning electron microscopy (FESEM) were employed to examine the conformation and morphology of PECs, respectively. Zeta (ζ) potential was utilized to investigate the charge density of PEC particles while the surface hydrophilicity of HPECMs was studied by using contact angle (CA) meter. When subjected to ethanol dehydration, HPECMs revealed a satisfactory pervaporation performance and desired anti-trade-off phenomenon. For HPECM 0.31 and HPECM 0.57, the permeation fluxes were 2.25 kg m−2 h−1 and 2.93 kg m−2 h−1, and the water content in permeate reached up to 99.35 wt% and 99.38 wt%, with respect to 10 wt% water in feed under 70 °C. All the results indicated that small-sized and sphere-like PECs were truly in favor of enhancing the pervaporation performance in ethanol dehydration.

Morphology, electrokinetic characteristics and the effect on biofilm formation of carrageenan:chitosan polyelectrolyte complexes

Carrageenan:chitosan (CG:CH) polyelectrolyte complexes (PEC) were obtained and the effect of the initial components ratio on formation was studied by dynamic light scattering, atomic force microscopy (AFM) and electrokinetic measurements. Positively charged PEC particles (average ζ-potential 40.2 mV) were formed, provided that the polycation was present in excess in the complex and was stabilized by chitosan amino groups. According to the AFM data, chitosan was located on the surface of the carrageenan fibers. In PEC where carrageenan prevailed, the number of unbound sulfate groups decreased when the chitosan content increased, this resulted in a decrease in the PEC negative surface charge (from −92.4 to −55.6 mV). In this case, AFM showed that chitosan was incorporated into the network structure of carrageenan and breaks it at a CG:CH ratio of 1:0.5 w/w. Complexes with a high content of kappa-CG inhibited biofilm formation by Gram negative and Gram positive microorganisms.

Pickering Janus emulsions and polyelectrolyte complex-stabilized Janus gels

Janus emulsions, containing olive oil (OO) and silicone oil (SiO), were formed in presence of polyelectrolyte complex particles, i.e., gelatin-sodium polyacrylate (NaPAA) complexes. The diameter of completely engulfed Janus droplets can be tuned between 50 and 200μm by varying the gelatin/NaPAA complex particle size between 200 and 400nm. The gelatin/NaPAA complex particles adsorbed at the olive oil interface decrease the interfacial tension and stabilize the resulting completely engulfed Pickering Janus emulsions.Long-term stable Janus gels can be synthesized in presence of gelatin/sodium carboxymethylcellulose (NaCMC) mixtures. In that case Coulombic forces are of relevance with regard to the stabilization of the Janus droplets embedded in a gelatin/NaCMC gel matrix. Janus gels show elastic reological behavior and thixotropic properties.

Cationic curdlan: Synthesis, characterization and application of quaternary ammonium salts of curdlan

Water-soluble curdlan derivatives containing quaternary ammonium groups with a degree of substitution up to 0.15 were synthesized using different cationic agents in alkaline medium. The chemical structure of curdlan derivatives was confirmed by FTIR, 13C and 1H NMR spectroscopy. The influence of some reaction conditions (temperature, time, and molar ratio) on the degree of substitution and the viscosimetic behaviour were studied. The degree of substitution increased with the amount of the cationization agent per anhydroglucose unit and was higher when the glycidyl reagents were used, compared with the case when the reagents contained chloro-hydroxypropyl groups. The viscosity behaviour of these new derivatives of curdlan in aqueous solutions and the values of intrinsic viscosities calculated using different semi-empirical equations denote a high hydrodynamic dimension of the macromolecular coils. The interaction of these cationic curdlan derivatives with an anionic curdlan (monobasic curdlan phosphate) was studied in situ by turbidimetric measurements and after 24h by optical density and dynamic light scattering. The formation of polyelectrolyte complexes was influenced by the degree of substitution, the nature of the quaternary substituent, and by the ionic strength of the aqueous solution. The morphology of the polyelectrolyte complexes particles in dry state was examined by atomic force microscopy.

Polyelectrolyte complex-silica hybrid colloidal particles decorated with different polyelectrolytes

We report the synthesis of polyelectrolyte-decorated hybrid colloidal particles by using negatively charged polyelectrolyte complex (PEC) micelles as colloidal templates for silica mineralization under ambient conditions. The negatively charged polyelectrolytes including poly(acrylic acid) (PAA), poly(L-glutamic acid) (PLGA), and poly(styrene sulfonate) (PSS) were complexed with poly(L-lysine) at non-stoichiometric mixing weight percentage to form negatively charged PEC micelles. Varying the mixing weight percentage and molecular weight of polyelectrolytes led to the changes in the size and charge of the PEC particles. Silica mineralization in the complex core resulted in the colloidally stable hybrid particles decorated with different negatively charged polyelectrolytes. The colloidal properties of these polyelectrolyte-decorated hybrid particles were determined by the composition and decorated polyelectrolyte. This approach provided a simple and facile method to prepare polymer-decorated hybrid colloidal particles comprised of different polymers and their colloidal properties can be easily tuned by varying the decorated polymer and synthesis condition.

Delivery of functional polyelectrolytes from complexes induced by salt addition: Impact of the initial binding strength

This paper focuses on polyelectrolyte complexes (PECs) soft nanoparticles and how dissociation occurs upon salt addition. The system is composed of a strong polyanion (polystyrene sulfonate, PSS) and a weak polycation (poly(allylamine) hydrochloride, PAH) in large excess. Soft nanoparticles were obtained by pouring a PSS solution into a PAH one under constant stirring. As the charge density of PAH chain depends on the pH of the polyelectrolyte solution, PEC particles exhibit distinct behaviors under salt addition depending on the pH of the continuous phase. At pH=5.5, PAH chains are fully charged and the addition of salt produces particle aggregation followed by sedimentation. Conversely, at pH=10 where PAH is only partially charged, the addition of salt drives a progressive disentanglement of the two polyelectrolytes, as revealed by both viscosimetric and spectroscopic measurements. At sufficiently high ionic strength, the two electrolytes are fully dissociated. Our results emphasize differences in behavior (binding reversibility) between strongly and weakly bound polyelectrolytes of opposite charge upon addition of salt. We discuss the potential use of these systems as stimulus responsive materials for the delivery of scale nucleation inhibitors in application around petroleum recovery.

Simple preparation of polyelectrolyte complex beads for the long-term release of small molecules.

We report a simple method for preparing solid polyelectrolyte complex (PEC) beads, which provide effective barriers to diffusion and can be used for the multiple-day release of small molecules. Single-phase poly(allylamine) (PAH) and poly(styrenesulfonate) (PSS) mixtures were prepared at pH 11.6 (significantly above the effective pKa of PAH), where the PAH amine groups were deprotonated and therefore neutral. These mixtures were added dropwise into acid baths, whereupon the rapid acid diffusion into the polyelectrolyte droplets led to instant ionization of PAH amine groups and, thus, the formation of PEC beads (i.e., via phase inversion). In stark contrast to the PEC particles prepared through phase inversion in previous studies, which had (solvent-filled) capsule-like morphologies, these beads had solid internal structures. The solute permeabilities of these PEC matrices could be extensively tuned by air drying the beads, which led to the apparently-irreversible closure of pores. Thus, by tuning the drying conditions and polymer compositions used during bead preparation, a model small molecule (Fast Green FCF dye) was released over times ranging between 2 and 18 days.

Formation of Soft NanoparticlesviaPolyelectrolyte Complexation: A Viscometric Study

This paper describes the formation of soft nanoparticles resulting from electrostatically driven complexation of oppositely charged polyelectrolytes. The system was composed of a strong polyanion (polystyrene sulfonate, PSS) and a weak polycation (poly(allylamine) hydrochloride, PAH) in large excess. Soft nanoparticles were obtained by pouring a PSS solution into a PAH one under constant stirring. The polyelectrolyte complexes (PEC) were characterized through a viscometric study complemented by Dynamic Light Scattering (DLS), electrophoretic mobility and suspension turbidity measurements. PEC suspensions were centrifuged and by measuring the viscosity of the supernatant, we were able to estimate the free polycation concentration and hence the percentage of complexed polycation. We also measured the relative viscosity of the suspensions; from the estimated contribution of the PEC particles and of the polycation in excess, the average particle volume fraction was estimated. From all viscometric data, we could derive the evolution of the binding stoichiometry in PEC and of the effective particle volume fraction as a function of the mixing ratio (ratio of the cationic to anionic groups) and of the pH. Our results emphasize the importance of charge accessibility in controlling both the stoichiometry and packing density of the complexes.

Cast adhesive polyelectrolyte complex particle films of unmodified or maltose-modified poly(ethyleneimine) and cellulose sulphate: fabrication, film stability and retarded release of zoledronate

The bone therapeutic drug zoledronate (ZOL) was loaded at and released by polyelectrolyte complex (PEC) particle films composed of either pure poly(ethyleneimine) (PEI) or maltose-modified poly(ethyleneimine) (PEI-M) and oppositely charged cellulose sulfate attached to model germanium (Ge) substrates by solution casting. Dispersions of colloidally stable polyelectrolyte complex (PEC) particles in the size range 11-141 nm were obtained by mixing PEI or PEI-M, CS and ZOL in defined stoichiometric ratios. TRANS-FTIR spectroscopy was used to determine the stability of the PEC films against detachment, in-situ-ATR-FTIR spectroscopy for the ZOL loss in the PEC film and UV-VIS spectroscopy for the ZOL enrichment of the release medium. Films of casted ZOL/CS/PEI-M or ZOL/CS/PEI particles were stable in contact to water, while films of the pure drug (ZOL) and of the binary systems ZOL/PEI-M or ZOL/PEI were not stable against detachment. Retarded releases of ZOL from various PEC films compared to the pure drug film were observed. The molecular weight of PEI showed a considerable effect on the initial burst (IB) of ZOL. No significant effect of the maltose modification of PEI-25 K on IB could be found. Generally, after one day the ZOL release process was finished for all measured ZOL/PEC samples and residual amounts of 0-30% were obtained. Surface adhesive drug loaded PEC particles are promising drug delivery systems to supply and release a defined amount of bone therapeutics and to functionalize bone substitution materials.

Poly(l-glutamic acid)-Decorated Hybrid Colloidal Particles from Complex Particle-Templated Silica Mineralization

We report the synthesis of polyelectrolyte complex (PEC) particles by mixing the negatively and positively charged polyelectrolytes, poly(L-glutamic acid) (PGA) and poly(2-(N,N-diethylamino) ethylmethacrylate) (PDEAEMA), and the use of negatively charged PEC particles as colloidal templates for silica mineralization under ambient conditions. The structure and property of PEC particles, as well as polypeptide chain conformation, were found to depend on the mixing weight percentage, polymer molecular weight, and solution condition. The negatively charged PEC micelles can be deposited with silica without loss colloid stability, leading to PGA-decorated hybrid particles. These hybrid particles were negatively charged at neutral and basic condition and become positively charged, accompanying the conformational changes of the grafted PGA, upon decreasing pH below isoelectric points due to the protonation/deprotonation of PGA and PDEAEMA. Functional nanoparticles such as gold NPs could be incorporated using polypeptides as the mediating agents. These hybrid particles loaded with drug exhibited noticeable pH-responsive behavior with accelerated release at acidic condition, demonstrating the potential for use as pH-responsive delivery vehicles. This type of polypeptide-decorated hybrid particles represents an interesting class of organic-inorganic hybrids in which the functional properties of polypeptides such as biocompatibility, stimuli responsiveness, and directed growth of metal nanoparticles can be incorporated.

Size-Controlled Polyelectrolyte Complexes: Direct Measurement of the Balance of Forces Involved in the Triggered Collapse of Layer-by-Layer Assembled Nanocapsules

Polyelectrolyte multilayers composed of poly(allylamine hydrochloride) and poly(styrene sulfonate) were assembled on 13 nm gold nanoparticles and characterized by Transmission Electron Microscopy and Atomic Force Microscopy. The direct measurement of the interactions at the molecular level using a Surface Force Apparatus revealed that the colloidal stability of such coated particles in aqueous media is brought about concomitantly by electrostatic and steric repulsive interactions. The cyanide induced dissolution of the gold cores yields either hollow nanocapsules or collapsed nanospheres, two species which are very difficult to distinguish. In contrast to the established micron sized hollow capsules, the dissolution of the nanosized gold cores may induce a substantial swelling of the polyelectrolyte complex into the central void as induced by the temporary local increase of the ionic strength. At least three layer pairs are required to maintain the structural integrity of the polyelectrolyte shells to yield hollow nanospheres. At about three layer pairs, thin nanocapsules are mechanically compressible and may collapse on themselves following mechanical stimulation to form even smaller spherical polyelectrolyte complex particles that retain the small polydispersity of the gold cores. Thus, the templating of polyelectrolyte shells around, e.g., gold nanoparticles followed by the dissolution of the respective cores constitutes a new method for the synthesis of extremely small polyelectrolyte complex particles with very low polydispersity.