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Despite decades of research, the fundamental question of structure and morphology of the poly(3,‐4‐ethylenedioxythiophene):poly(styrene sulfonate) complex (PEDT: PSS) electrically conducting polymer remains open. Here, through a systematic study of the polymerization of 3,4‐ethylenedioxythiophene (EDT) on two series of sulfonated polystyrenes, i.e., PS‐co‐SSH and PS‐co‐SSNa, with per cent sulfonation 24 ≲ x ≲ 100, this study shows that the substrate polyelectrolyte not only affords charge compensation and processability, but also templates the morphology of the growing PEDT chain—whether extended, coiled or collapsed. This determines the electrical, electronic and optical properties of the resultant PEDT: PSS interpolyelectrolyte complexes, including their work function. This study calls this the Polyelectrolyte Template model. The PEDT: PSS complex retains memory of its polymerization morphology even after subsequent ion‐exchange, for example, to the same acid form. Electrical conductivity decreases sharply with decreasing x, and depends on whether the polymerization is templated with the H+ or Na+ form of the polyelectrolyte. The work function is less sensitive to x, but exhibits a transition from low to high work function (5.2–5.3 eV) when x exceeds a threshold, which indicates formation of a polar surface driven by molecular‐scale segregation of the PSS counteranion. This surface segregation also affects the ability of these complexes to inject holes into very large‐ionization‐energy semiconductors. [ABSTRACT FROM AUTHOR]

The aim of this study was the analysis of interpolyelectrolyte complexes (IPECs) based on Eudragit® EPO and Eudragit® L100 as prospective carriers for gastroretentive drug delivery systems (GRDDS) using two model drugs: metronidazole (MZ) and acyclovir (ACR). Eudragit® EPO/L100 IPECs with different pH concentrations were characterized by different degrees of swelling in mimicking fasted stomach medium (0.1 M HCl) and saved their shape for 6 h. The microenvironmental changes in IPEC structures in acidic medium were investigated using FT-IR spectroscopy, thermal and elemental analysis. IPEC samples showed bioadhesive properties that were not significantly different from the positive control (Carbopol) in the test with the mucin compacts. The release rate of metronidazole (class I BCS) from IPEC matrices increased with the increasing degree of swelling. IPEC 1 provided 49.62 ± 6.20% and IPEC 2 reached 87.69 ± 5.15% of metronidazole release after 6 h in mimicking fasted stomach medium (0.1 M HCl). The total amount of released acyclovir (class III BCS) from IPEC 1 was 25.76 ± 5.67% and from IPEC 2 was 21.48 ± 5.00%. Release of both drugs was controlled by relaxation of polymeric chains in matrices according to the Peppas–Sahlin model. According to the received results, investigated interpolymer complexes are prospects for further evaluation as carriers for gastroretentive bioadhesive systems. [ABSTRACT FROM AUTHOR]

IR spectroscopy is used to show that aerogels based on the interpolyelectrolyte complexes (IPEC) form in slightly acidic aqueous solutions at initial molar ratios ≥1.5 of aqueous solutions of chitosan and sodium alginate. Two to three times more hydroxylophine (in sc-CO2) can be introduced into AG-based matrices than into the corresponding polymer films of the same mass, due obviously to the larger surface area of the AG. It is found the preliminary solubilization of TAI with pluronic F-127 contributes to additional slowing of the release of the active substance from the matrices into a model biological environment. [ABSTRACT FROM AUTHOR]

Due to the presence of cationic units interpolyelectrolyte complexes (IPECs) can be used as a universal basis for preparation of biocidal coatings on different surfaces. Metallopolymer nanocomposites were successfully synthesized in irradiated solutions of polyacrylic acid (PAA) and polyethylenimine (PEI), and dispersions of non-stoichiometric IPECs of PAA–PEI containing silver ions. The data from turbidimetric titration and dynamic light scattering showed that pH 6 is the optimal value for obtaining IPECs. Metal polymer complexes based on IPEC with a PAA/PEI ratio equal to 3/1 and 1/3 were selected for synthesis of nanocomposites due to their aggregative stability. Studies using methods of UV–VIS spectroscopy and TEM have demonstrated that the size and spatial organization of silver nanoparticles depend on the composition of polymer systems. The average sizes of nanoparticles are 5 nm and 20 nm for complexes with a molar ratio of PAA/PEI units equal to 3/1 and 1/3, respectively. The synthesized nanocomposites were applied to the glass surface and exhibited high antibacterial activity against both gram-positive (Staphylococcus aureus) and gram-negative bacteria (Salmonella). It is shown that IPEC-Ag coatings demonstrate significantly more pronounced biocidal activity not only in comparison with macromolecular complexes of PAA–PEI, but also coatings of PEI and PEI based nanocomposites. [ABSTRACT FROM AUTHOR]

In this paper we give the overview of our latest results on the complexation between polyelectrolytes and oppositely charged low-molar mass species, proteins, homopolymers and block copolymers. First, we review the results on the study of the interaction of polythiophene-based polycations with phosphonium and ammonium pendants and their complexation with negatively charged multivalent species followed by fluorescence quenching. We proved that multivalent solutes bind to polyelectrolyte stronger than to previously studied polythiophene, thus, allowing for their application as luminescence sensors. Secondly, we investigated the co-assembly of polyanion with double hydrophilic block copolymer composed of polycationic block and neutral hydrophilic block and followed the complex formation by quenching of fluorescence of the indicator attached to the end of polyanion chain. We discovered that the formed interpolyelectrolyte (IPEC) core of core/shell micelles remains dynamical even after equilibrium was reached thus making such systems suitable materials for targeted delivery of multivalent species. In addition, the formation of micelles with fluid cores was observed as a result of self-assembly of di- and triblock polyelectrolytes containing a hydrophobic block with low glass transition temperature and a positively charged block. We proved their ability to encapsulate and release hydrophobic species from the soft core upon dilution. Moreover, we confirmed their ability to complex with multivalent negatively charged species. The morphology of the formed complex strongly depends on ionic strength: the aggregates formed by micelles bonded at the periphery disrupt with increasing salt concentration and a part of multivalent ions releases into solution. Finally, the multilayered nanoparticles with both soft hydrophobic and IPEC layers were designed by co-assembly between core/shell micelles with a soft core and a positively charged shell, and block polyelectrolyte composed of polyanion and neutral hydrophilic blocks. We showed that the morphology of the particles and the charge of IPEC layer of such multicompartment nanostructures can be controlled by the ratio of oppositely charged monomeric units. [ABSTRACT FROM AUTHOR]

We describe six aqueous formulations prepared from anionic HYPAN, an acrylic acid/acrylamide copolymer, and cationic poly(diallyldimethylammonium chloride) (PDADMAC) for stabilization of loamy sandy soil and quartz sand. The formulations were deposited on the surface of soil and sand that after drying resulted in the formation of protective polymer–soil and polymer–sand coatings. Most formulations gave mechanically stable coatings with a strength of 100–200 kg cm−2 and sustained a storm wind of 76 km h−1. A non‐stoichiometric HYPAN–PDADMAC polycomplex with a 10‐fold excess of anionic HYPAN units formed the water resistant coatings, which retained 99% soil and 90% sand. These characteristics were superior to those for coatings made from a conventional binder polyacrylamide. Additionally, the coating from soil and 'anionic' non‐stoichiometric interpolyelectrolyte complex increased the total amount of stored water and lengthened the time of water release. Anionic polymer formulations did not exhibit antimicrobial action against bacteria and yeast in both solutions and films. Cationic polymer formulations manifested strong antimicrobial action against bacteria and yeast in solutions, and suppressed the growth of Gram‐positive bacteria and yeast in films. Taking into account the commercial availability of the initial polymers and a simple procedure for polycomplex preparation, there is great potential for anionic polymer formulations as anti‐erosion binders and soil conditioners. © 2021 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Background. Research is underway to obtain three-component interpolyelectrolyte complexes (IPECs) of chitosan with polyanions and polyampholytes. The presence of a surface charge in the macromolecule of three-component IPECs can effectively immobilize oppositely charged particles. Purpose: obtaining stable three-component interpolyelectrolyte complexes based on Bombyxmori chitosan and studying their physicochemical properties. Methodology. We used conductometric titration, DLS, Litesizer and other research methods. Originality.Three-component interpolyelectrolyte complexes based on natural macromolecules have been obtained and their hydrodynamic parameters have been studied. Findings.The compositions and hydrodynamic dimensions of three-component complexes of chitosan were revealed. It has been established that at pH 6.3 binary complexes of chitosan/Na-CMC interact with collagen at 1:0.75:0.01 wt. ratio, where the sum of the surface charge of the complex is equal to zero. The hydrodynamic particle sizes of ternary IPECs vary from 98 to 132 nm. [ABSTRACT FROM AUTHOR]

This paper investigates the structure, morphology and antimicrobial properties of silver-containing nanocomposites based on interpolyelectrolyte complexes (IPEC) of pectin with polyethylenimine, cationic starch or chitosan as a cationic polyelectrolyte. The reduction of silver ions was carried out by thermochemical technique by heating of the interpolyelectrolyte–metal complexes, which in turn prepared by adsorption of ions on IPEC. The chemical reduction was also performed using ascorbic acid as reductant. The temperature and time needed to produce the nanocomposites at which completely reduction of silver ions occurs are 150 °C and 30 min. It is revealed that during thermochemical reduction depending on the type of cationic polyelectrolyte (PEI, cationic starch, chitosan), silver nanoparticles with an average size of 4.1, 5.3 and 4.7 nm, respectively, are formed. Various mechanisms of thermochemical reduction for interpolyelectrolyte–metal complexes containing polymers with aminogroups or polymers with the glucopyranose units are considered. It is found that the silver-containing nanocomposites, formed by thermochemical reduction, exhibited higher antimicrobial activity against strains of S. aureus and E. coli than ones obtained using ascorbic acid. [ABSTRACT FROM AUTHOR]

Introduction. One of the well-known requirements for buccal drug delivery systems is the demonstration of mucoadhesive properties of the carrier, ensuring retention on the mucosa for a long time with the gradual release of the included drug. It should be noted that one of the advantages of buccal systems compared with oral ones is the absence of the «first pass effect» through the liver.Aim. To carry out a physicochemical and pharmaceutical research of the interpolyelectrolyte complex (IPEC), obtained on the basis of pharmaceutically acceptable polymers – Eudragit® EPO and Noveon® AA-1, in comparison with the physical mixture and individual polymers, as a mucoadhesive delivery system of metronidazole for the treatment of periodontal diseases.Materials and methods. Obtained on the basis of a pair of pharmaceutical polymers (Eudragit® EPO and Noveon® AA-1), two IPEC samples were characterized by elemental analysis, FTIR spectroscopy, and modulated temperature differential scanning calorimetry (mDSC) in comparison with individual polymers and their physical mixtures. The study of swelling ability, bioadhesion and release was carried out in a medium simulating artificial salivary fluid (pH 7.0) at a temperature of 37 ± 0.1 °C. Mucoadhesion of polymer samples and IPEC was studied using a TA.XTplus texture analyzer (Stable Micro Systems, UK). The release of metronidazole (MD) from matrices based on the developed IPEC was studied on a CE 7Smart USP 4 apparatus (Sotax, Switzerland) using the Flow Trough Cell method at a speed a flow of 20 ml/min in an open cycle within 5 hours. The amount of released MD was estimated by UV spectrophotometry on a Lambda 25 instrument (PerkinElmer, USA) at a wavelength of 319 nm.Results and discussion. As a result of studies on the physicochemical and pharmaceutical properties, there was selected the optimal composition of a polycomplex carrier (IPEC 2) based on Eudragit® EPO and Noveon® AA-1, which is characterized by the required bioadhesive properties and the ability of providing controlled release of drug from the tablet matrix (with weight ratio MD/IPEC-2 1:0.5) in conditions mimicking oral cavity environment, which provides the necessary mode of buccal delivery of metronidazole in accordance with Fick's law of diffusion.Conclusion. IPEC 2 is a perspective for use as carrier for buccal controlled delivery of metronidazole.

Introduction. There are a number of drugs, the absorption zone of which is the upper region of the gastrointestinal tract (GIT) – the stomach and duodenum. To increase bioavailability, gastroretentive (intragastric) systems for the controlled drug delivery are being developed. To date, there are various approaches to ensure intragastric drug delivery. One of the most promising approaches is the use of excipients with bioadhesive properties, both individually and in combination with other types of gastroretentive systems.Aim. Development and research of new carriers for gastroretentive bioadhesive drug delivery systems based on interpolyelectrolyte complexes (IPEC) with the participation of chemically complementary poly(meth)acrylates of the Eudragit®.Materials and methods. The study of swelling ability was carried out in a medium of 0.1 M hydrochloric acid solution (pH 1.2) at a temperature of 37 ± 0.5 °C for 6 hours. The study of the release of metronidazole (MZ) from matrices based on the corresponding IPEC was performed on a DFZ II instrument (ERWEKA, Germany) according to the Flow Trough Cell method in 0.1 M HCl medium, pH 1.2, flow rate 4 ml/min in a closed cycle within 6 hours. The amount of released MZ was estimated by UV spectrophotometry on a Lambda 25 instrument (PerkinElmer, USA) at a wavelength of 274 nm. IPEC adhesion was studied using a TA.XTplus texture analyzer (Stable Micro Systems, UK).Results and discussion. Matrices based on IPEC 1 were disintegrated after being in a medium with a pH of 1.2 for 4 hours, matrices based on IPEC 4 were dissolved in an acidic medium for 3 hours. At the same time, matrices based on IPEC 2 and IPEC 3 retain their shape throughout the experiment and are characterized by rather high values of the degree of swelling. IPEC samples are characterized by higher adhesion performance compared to individual copolymers. The release of metronidazole from matrices based on IPEC 1 occurs in accordance with Fick's law of diffusion; from the matrix based on IPEC 4, MZ is released according to the anomalous transport mechanism.Conclusion. IPEC 3 is promising for use as carrier for gastroretentive bioadhesive systems of controlled delivery of metronidazole.

Interpolymer complexes (IPC) Eudragit® EPO/S100 were prepared in different media (water pH of 7.0 and ethanol). According to the elemental analysis, FTIR spectroscopy, and thermal analysis data, IPC prepared in aqueous media (denoted as interpolyelectrolyte complexes—IPECs) is stabilized predominantly by ionic intermacromolecular bonds and has a composition close to equimolar. However, polycomplexes formed in nonaqueous (ethanol) media (denoted as IPC) are stabilized by both hydrogen and ionic bonds and characterized by an almost twofold excess of Eudragit® S100. All samples do not include free copolymer domains. IPECs and IPCs have different behavior in the buffer media mimicking the gastrointestinal tract. Matrices of IPECs are characterized by the surface erosion and pH‐independent swelling profiles with low values of a swelling degree. Matrices of the IPCs swell significantly in the buffer media with pH 1.2, 5.8, and 6.8 with subsequent decrease in the swelling degree due to the surface erosion. According to the assessment of release of the model active pharmaceutical ingredient (API), IPECs are prospective carriers for sustained delivery of II class Biopharmaceutical Classification System (BCS) drug (diclofenac sodium). At the same time, IPCs provide sustained release of the II class BCS and prolonged release of the I class BCS drug (theophylline). [ABSTRACT FROM AUTHOR]

Carbopol polymers are polymers of acrylic acid and crosslinking agents; there is the prospect of penetration of linear macromolecules between the mesh size of crosslinked Carbopol microgels for a certain period of time. Interpolyelectrolyte complex (IPEC) samples between Carbopol and linear polycations (Eudragit EPO—EPO) were obtained at different interpolyelectrolyte reaction (IPER) times (1, 3, and 7 days). Confirmation of the IPEC structures was proved by FTIR and mDSC. Moreover, according to the results of elemental analysis and mDSC, an increase in the duration of IPER time did not lead to a significant increase in the fraction of the incorporated EPO (CS), since its amount in polycomplex samples remains almost unchanged and the Tgs varies slightly and it depends from the Carbopol grade used. Analysis of the particle size and zeta potential of polycomplex gels showed that the obtained IPEC samples are nanosized, and the particle charge depends on the presence of free ionized carboxyl groups Carbopol (Noveon) or positively charged dimethylamino groups of EPO on their surfaces. After increasing the duration of IPER up to 3 days, a decrease in zeta potential values was observed. In the case of 7 days, an increase in particle size was observed due to their aggregation (C2020/EPO, C10/EPO, NAA‐1/EPO). Mathematical modeling of diclofenac sodium release according to the Korsmeyer–Peppas equation showed that all IPEC samples were characterized by the Super Case‐II transport mechanism, except for C10/EPO sample, which was characterized by Anomalous transport. [ABSTRACT FROM AUTHOR]

The structure and properties of Cu/Cu2O-containing nanocomposites formed by chemical reduction of Cu2+ ions in interpolyelectrolyte–metal complexes (IMC) at different molar ratios [NaBH4]: [Cu2+] and reduction times were studied by methods of wide- and small-angle X-ray scattering, transmission electron microscopy, thermomechanical analysis, and antimicrobial tests. Optimal conditions ([NaBH4]: [Cu2+] = 6.0, reduction time ≥ 120 min) for the formation of copper-containing nanocomposites based on interpolyelectrolyte complexes and Cu/Cu2O core–shell nanoparticles have been established by X-ray diffraction analysis. Owing to the above conditions, the structural manifestation of the metal copper phase is fully realized. Applying transmission electron microscopy, it was found that at molar ratio [NaBH4]: [Cu2+] = 6.0, and reduction time of 40 min and 180 min, accordingly, the nanocomposites with average nanoparticles size of 4.1 nm and 12.4 nm are derived from IMC, respectively, what correlates with effective size of the nanocomposites' heterogeneity regions, lp. Thermomechanical analysis has shown that raise in the amount of reducing agent or the duration of reduction of Cu2+ ions in IMC is accompanied by elevation in the glass transition temperature, which reaches a constant level, boost in the temperature of transition to the viscous state Tf and decrease in the relative deformation of nanocomposites. The antimicrobial investigations of the elaborated nanocomposites revealed they possess an antimicrobial activity against S. aureus and E. coli strains. [ABSTRACT FROM AUTHOR]

The structure and properties of silver-containing nanocomposites formed by the method of thermochemical reduction of Ag+ ions in polyelectrolyte-metal complexes pectin–Ag+–polyethyleneimine were studied using X-ray diffraction analysis, thermogravimetric analysis, pyrolysis mass spectrometry, transmission electron microscopy and antimicrobial test. The optimal parameters for the formation of nanocomposites based on interpolyelectrolyte complexes of pectin–polyethyleneimine and Ag nanoparticles (reduction temperature T = 150 °C, reduction time t = 30 min) have been found by X-ray diffraction analysis, in which the structural manifestation of the silver metal phase is fully realized. Using transmission electron microscopy, it was found that nanocomposite formed by thermochemical reduction of Ag+ ions at 150 °C for 30 min has an average nanoparticle size of 4.1 nm that less than for nanocomposite obtained at T = 120 °C during the same reduction time (average nanoparticle size is 5.8 nm). Ag nanoparticles obtained by using a typical reducing agent (NaBH4) have an average size equals 3.8 nm. It was revealed that nanocomposites obtained by thermochemical method have significantly higher antimicrobial activity compared with nanocomposites obtained by chemical reduction of Ag+ ions using NaBH4. A mechanism of thermochemical reduction of silver ions in IMC pectin–Ag+–polyethyleneimine, which is based on the transfer of electrons from the nitrogen atoms of amino groups PEI to Ag+ ions, has been investigated by destructive processes that occur at the same time. [ABSTRACT FROM AUTHOR]

The specific features of the formation of metal nanoparticles under X-ray radiation in interpolyelectrolyte complex (IPEC) films based on polyacrylic acid and polyethyleneimine with different silver ion content were studied. IPEC films were irradiated in aqueous-alcoholic medium. Electron microscopy demonstrated that the formation of silver nanoparticles occurred in zones regularly located by film thickness. It was found that nanoparticle size and spatial distribution in IPEC films depended on the initial concentration of silver ions within the sample and on the absorbed dose of radiation. The obtained film nanocomposites are promising objects for application as antibacterial and catalytic materials. [ABSTRACT FROM AUTHOR]

Abstract The structural organization and thermomechanical properties of nanocomposites prepared from interpolyelectrolyte–metal complex (IMC) involving anionic polyelectrolyte, pectin and AgNO3, and cationic polyelectrolyte, poly(4-vinylpyridine), have been investigated using the methods of wide- and small-angle X-ray scattering and thermomechanical analysis. It is established that chemical reduction of Ag+ ions in the IMC by sodium borohydride results in formation of the nanocomposite based on the “pectin–poly(4-vinylpyridine)” interpolyelectrolyte complex (IPEC) and Ag0 nanoparticles as well. At the same time, the level of nanocomposites’ structural heterogeneity is substantially enhancing, while effective size of the heterogeneity regions decreases. The nanocomposites IPEC–Ag0 prepared are shown much bigger T g value and enhanced ability for deformation than those for IMC.

Copper, silver and gold nanoparticles were obtained by reduction of metal ions under X-ray irradiation of "layer-by-layer" (LbL) coatings in a water-alcohol medium. The precursors for metal polymer composites (metallopolymer complexes) were prepared by sorption of metal ions in polyethyleneimine - poly (styrenesulfonic acid) and polyethyleneimine - poly (acrylic acid) coatings deposited on cotton fibers. EPR spectroscopy was use to characterize the complexation of metal ions in coatings with different chemical structure and variable number of polyanion-polycation layers. The effect of coating structure and thickness on the size and stability of nanoparticles was studied using TEM and microdiffraction measurements. Antibacterial activity was found for composites containing silver nanoparticles. • Radiation-induced reduction of metal ions in the ultrathin polymer coatings. • Obtaining of nanocomposite antibacterial coatings on the textile fabrics. • The effect of the number of layers of polyelectrolyte on the ions sorption capacity. • Advantages of PEI-PAA as a matrix for metal nanocomposite preparation. [ABSTRACT FROM AUTHOR]

Background. Currently huge amount of work has been carried out to obtain interpolyelectrolyte complexes (IPEC) of chitosan with natural and synthetic polyanions. Presence of charge in the macromolecule on surface of IPEC particles could effectively immobilize oppositely charged of particles. In this regard, polyelectrolyte complexes are used for wastewater purification, targeted drug delivery, for the construction of different biomaterials, as well as biologically active and biodegradabled of agricultural preparations. At the present, time study of fundamental principles of obtaining IPEC of natural polyelectrolytes and creation of preparations based on nosshown scientific and applied interest. Purpose. The aimof study is obtaining thermodynamically stable interpolyelectrolyte complexes based on Bombyx mori chitosan and study their ability to bind with soil minerals. Methodology. At this work are used turbidimetric, potentiometric and conductometric titration, laser microelectrophoresis, elemental analysis, etc. Originality. For the first time, stoichiometric and non-stoichiometric Bombyx mori chitosan complexes were obtained and hoyghown the possibility of their applicotions as a structurant for soil erosion. Findings. Obtained IPEC chitosan Bombyx mori with macromolecules of Na-CMC. The composition and hydrodynamic dimensions of the complexes are revealed. It was established that at pH = 6.3 of, chitosan and Na-CMC interacted at 1: 0.34 molar ratio. The particle size of IPEC in solution ranges from 80 to 1000 nm and has ability to bind with soil minerals, forming strong crusts. It hos shown that polyelectrolyte crusts are durable to washing and mechanical stress, which in will be applied in soil erosion. [ABSTRACT FROM AUTHOR]

Film membranes were prepared from interpolyelectrolyte complexes of various aliphatic polyamines with a copolyamide synthesized from isophthalic dichloride and two diamines: disodium 4,4′-diaminobiphenyl-2,2′-disulfonate and 4,4′-diaminodiphenylmethane-2,2′-dicarboxylic acid. The mechanical and sorption properties of the membranes and their performance in pervaporation separation of the water-isopropanol mixture were studied. The possibility of thermal cross-linking of the materials was demonstrated. The effect of the amidation on the physicochemical and mass-exchange properties of the film samples was examined. The variation of the separation characteristics of the membranes depending on the copolyamide composition was considered. With respect to the combination of separation and transport properties, the interpolymer systems containing the copolyimide with low (7 mol %) content of units with carboxy groups are of most interest. An increase in the fraction of carboxyl-containing units in the polyanion leads to an increase in the permeability of the materials with a significant decrease in their selectivity. The tensile strength of the film samples prepared from copolyamide-containing interpolyelectrolyte complexes is 54–92 MPa. [ABSTRACT FROM AUTHOR]

Conditions for the preparation of stable to sedimentation aqueous dispersions of interpolyelectrolyte complexes based on chitosan (Chit) and pectin (Pect) with particle diameter 0.5-0.9 μm for Pect/Chit and 1.0-2.0 μm for Chit/Pect have been determined. The absolute value of the zeta potential of these complexes is >10 mV for Pect/Chit and Chit/Pect when the molar ratio of the ionogenic groups of the polymers nCOOH/nNH2 is 0.4-4.6 for Pect/Chit and 0.02-0.63 for Chit/Pect. Optical spectroscopy and electrophoretic light scattering have been used to determine the effect of molecular mass and the content of the free ionogenic groups in the polysaccharide macromolecules as well as the order of mixing the solution on the formation and properties of these interpolyelectrolyte complexes. [ABSTRACT FROM AUTHOR]

The bimetallic nanostructures are of considerable interest for various prospective applications. This paper reports a generation of the Cu/Ag and Cu/Au nanoparticles in the interpolyelectrolyte films irradiated in aqueous media. It was shown that the radiation-induced reduction of (Cu/Ag) or (Cu/Au) ions in the matrix of poly(acrylic acid)-polyethylenimine complexes led to formation of the nanoparticles with narrow size distribution. The core-shell structure of nanoparticles was demonstrated by the TEM results. According to the X-ray diffraction data, the nanoparticle cores (Ag or Au) are formed at early stage of irradiation, while increase of the absorbed dose results in the growth of copper shell. It was demonstrated that the radiation-induced reduction could be applied for effective preparation of bimetallic nanoparticles directly in the polymer matrix. [ABSTRACT FROM AUTHOR]

Structural organization, morphology and thermomechanical properties of nanocomposites based on pectin, polyethyleneimine and Cu nanoparticles, formed by the thermal reduction method from interpolyelectrolyte–metal complexes (IMC) pectin–Cu 2+ –polyethyleneimine have been investigated using WAXS (wide-angle X-ray scattering), SAXS (small-angle X-ray scattering) methods as well as TEM (transmission electron microscopy) and thermomechanical analysis. It is defined that thermal reduction of Cu 2+ ions in IMC bulk (while films are heated to the temperature around 170 °C and higher temperatures) results in nanocomposites based on interpolyelectrolyte complexes “pectin–polyethyleneimine” and Cu nanoparticles being formed. In its turn, thermal reduction of copper ions is found out to take place owing to polyethyleneimine (namely, on account of electrons transfer from the amino groups’ nitrogen atoms of polyethyleneimine to Cu 2+ ions). It has been shown by thermomechanical analysis that the optimal time for complete thermal reduction of Cu 2+ ions to metallic copper at T = 170 °C is 30 min. The antimicrobial investigations of the elaborated nanocomposites revealed they possess a high antimicrobial activity against S. aureus and E. coli strains. [ABSTRACT FROM AUTHOR]

Solutions of the series of polymers (sodium polystyrene sulfonate, polyethyleneimine, and poly-N-vinylpyrrolidone) and certain mixtures thereof were studied by NMR relaxation and ESR spectroscopy using manganese(II) and gadolinium(III) ions as paramagnetic probes. The growth of the NMR-relaxation efficiency (relaxivity, R 1,2 ) is observed in solutions of the anionic polymer, as well as the decrease of R 1,2 - in the case of the cationic polymer. For mixtures of polymers, the dependent on the solution composition non-monotonic changes of R 1,2 are caused either by a formation of metal-interpolymer complexes or by a competitive cation/polymer substitution. For both ions, the changes in the ESR spectra of their polyelectrolyte solutions were analyzed. In case of sodium polystyrene sulfonate and blends thereof, the ESR spectra parameters are only slightly broadened compared to the pure metal aqua ion's, whereas for the polyethyleneimine solution the ESR spectra lines broaden greatly at pH > 7 up to their disappearance. All these effects were explained by the distinction of ion probes' binding mode to polyelectrolytes of different nature. Addition of NaCl to manganese(II) solutions containing polystyrene sulfonate, or mixtures thereof with PVP or PEI, lead to recovery of R 1,2 values, close to the probes' aqua ions relaxivities due to the release of the latter from the polymer/medium interface into the bulk water, while no changes were detected for PEI solutions. [ABSTRACT FROM AUTHOR]

The structural organization and thermomechanical properties of nanocomposites prepared from interpolyelectrolyte-metal complex (IMC) involving anionic polyelectrolyte, pectin and AgNO, and cationic polyelectrolyte, poly(4-vinylpyridine), have been investigated using the methods of wide- and small-angle X-ray scattering and thermomechanical analysis. It is established that chemical reduction of Ag ions in the IMC by sodium borohydride results in formation of the nanocomposite based on the 'pectin-poly(4-vinylpyridine)' interpolyelectrolyte complex (IPEC) and Ag nanoparticles as well. At the same time, the level of nanocomposites' structural heterogeneity is substantially enhancing, while effective size of the heterogeneity regions decreases. The nanocomposites IPEC-Ag prepared are shown much bigger T value and enhanced ability for deformation than those for IMC. [ABSTRACT FROM AUTHOR]

Interaction between anionic (and cationic) colloidal particles of silica having the particles diameters 12 and 22 nm with synthetic cationic (and anionic) polyelectrolytes of various nature and structure was studied by potentiometric, conductimetric spectroturbidimetric and viscometric methods in aqueous solution. It was shown that the complexation of silica nanoparticles with linear polyelectrolytes leads to formation of mostly stoichiometric interpolyelectrolyte complexes (IPEC) which precipitate from aqueous solution. Casting of water-soluble IPEC followed by thermal treatment gives thin composite films insoluble in water while ‘layer by layer’ (LbL) deposition of polyelectrolyte components onto silica sols leads to formation of multilayered nano- and microcomposites. The possible mechanism of formation of LbL multilayers consisting of silica sol (SiO2) ‘cores’ and polyethyeleneimine-polyacrylic acid (PEI-PAA) ‘shells’ was suggested. It was found that in diluted aqueous solution the radius of gyration, Rg and hydrodynamic radius, Rhmean of LbL particles are independent on LbL concentration and smaller than 100 nm. The zeta potential values of LbL particles are arranged between –10 and –30 mV. The average size of LbL particles estimated by scanning electron microscopy (SEM) is in the range of 200–500 nm. Thermal treatment of LbL multilayers followed by etching of (SiO2) ‘core’ by HF leads to formation of a series of spherical nanocavities and blob-like microcavities.

Interpolyelectrolyte complexes (IPEC) have been used in different fields, ranging from biomedicine to oil exploration. Particle dimension is a key parameter for the use of an IPEC for a particular application. In this work, dynamic and static scattering (in the form of optical DLS and SAXS, respectively) were used to follow particle growth as a function of anionic/cationic polyelectrolyte mass ratio, w A C , coupled to turbidimetry, conductometry, viscometry, and zeta potential measurements. Turbidimetry, conductometry, and viscometry showed that at w A C ≅ 2 the IPEC dispersions presented changes that were associated to a massive production of IPEC particles. At the same w A C value, zeta potential measurements indicated an apparent isoelectric point, showing that this w A C must be related to a stoichiometric point for IPEC formation. Double KWW equation was adjusted to data from DLS intensity correlation functions, and parameters related to the distribution of relaxation rates presented characteristic changes at the same value of w A C . SAXS was used to follow particle growth until massive IPEC production. It showed that particles firstly were in the form of small, globular particles, tending to unfolded chain geometry, which can be related to the occurrence of flocculation, just at the point of massive IPEC production. [ABSTRACT FROM AUTHOR]

[Display omitted] • New interpolyelectrolyte non-toxic complexes based on the self-assembly of water-soluble pillar[5]arenes were obtained. • Spherical aggregates with an average diameter of 10 nm are found. • Interpolyelectrolyte complex more efficiently binds quercetin (pK a 5.13) compared with individual macrocycles. • The influence of the pH media on the ability of quercetin to be released from the IPEC was shown. The using of pH-sensitive delivery systems is a promising strategy to significantly improve the pharmacological properties of water-insoluble drugs. Herein, we propose and develop an approach to synthesis of interpolyelectrolyte complexes based on combination of two water-soluble decasubstituted non-toxic pillar[5]arenes for encapsulation poor-soluble quercetin and its subsequent release depending on the pH. Interpolyelectrolytes were obtained by mixing aqueous solutions one of which contained a polycationic (ammonium) and the other - a polyanionic (carboxylate) components. The shape and size evolution of interpolyelectrolytes were studied by dynamic light scattering and transmission electron microscopy. Spherical aggregates with an average diameter of 10 nm are found. The ability to form complexes and associates with quercetin by polycationic and polyanionic macrocycle, as well as an interpolyelectrolyte complex based on them, was studied by electron UV–vis and fluorescence spectroscopy, dynamic light scattering. Interpolyelectrolyte complex more efficiently binds quercetin (pK a 5.13) compared with individual macrocycles due to the greater stability of the associates formed by IPEC. The release of quercetin from the interpolyelectrolyte complex was studied in acidic (pH = 4.00), weakly acidic (pH = 5.00–5.50), neutral (pH = 7.44) and weakly alkaline (pH = 8.15) solutions. It was found the full release of the quercetin without oxidation of flavonoid is observed in the neutral solution. This work provides important guidance for the design of successful delivery systems via optimizing the structure and composition of nanocapsules. [ABSTRACT FROM AUTHOR]

The morphology, structural, thermomechanical and electric properties of nanocomposites prepared from interpolyelectrolyte–metal complex being formed involving anionic polyelectrolyte – pectin, CuSO 4 and cationic polyelectrolyte – polyethyleneimine have been investigated using the methods of wide-angle X-ray scattering, transmission electronic microscopy, thermomechanical analysis and dielectric spectroscopy. Such type of nanocomposites with Cu/Cu 2 O core–shell nanoparticles incorporated into polymer matrix is obtained due to the chemical reduction of Cu 2+ cations by NaBH 4 in the interpolyelectrolyte complex, and appearance of the copper’s metallic phase is observed in full extent while BH 4 − :Cu 2+ molar ratio is equal to 6.0. Applying thermomechanical analysis and dielectric spectroscopy, it was observed that transformation of interpolyelectrolyte–metal complexes into nanocomposites results in decreasing of their glass-transition temperature and increasing of the electric conductivity. [ABSTRACT FROM AUTHOR]

Applying wide-angle X-ray scattering method, thermomechanical analysis, and differential scanning calorimetry, the structural organization and properties of nanocomposites formed by chemical reduction of Сu cations in the interpolyelectrolyte-metal complex (pectin-Cu-polyethyleneimine) under the influence of a constant magnetic and electric fields have been studied. It has been found that the chemical reduction of Cu cations in the interpolyelectrolyte-metal complex bulk under constant electric and magnetic fields leads to formation of nanocomposite consisting of interpolyelectrolyte complex, including pectin-polyethyleneimine and nanoparticles of the metal Cu phase, whereas nanocomposite with Cu/CuO nanoparticles is formed in original state (without any field). It was observed that, under constant field, nanocomposites obtained have higher structural glass-transition temperatures and thermal stability. [ABSTRACT FROM AUTHOR]

The article is devoted to the design, development and application of a new generation of binders for various dispersed systems, including soil, ground, sand, waste rock and others. The binders are formed by interaction of oppositely charged polyelectrolytes, both chemically stable and (bio)degradable. The fundamental aspects of interpolyelectrolyte reactions are discussed; the IPC structure and properties of the resulting interpolyelectrolyte complexes (IPCs) allow considering them as unique and universal binders. Numerous results of laboratory experiments and field trials of the IPC formulations are presented. In particular, large-scale tests have been done in the Chernobyl accident zone where the IPC binders were shown to be effective means to suppress water and wind erosion thereby preventing a spread of radioactive particles (radionuclides) from contaminated sites. Ecologically friendly IPC compositions are described, including those based on commercially available polymers; prospects for improving their efficiency and extending the range of their possible use are discussed. [ABSTRACT FROM AUTHOR]

The interpolyelectrolyte complexes (IPECs) are widely used for various applications, ranging from agriculture and medicine to advanced technological processes. In many cases, they are subjected to the action of ionizing radiation or hard UV light, either intentionally (e.g., for fabrication of nanocomposites) or in the course of routine treatment (sterilization or weathering), or unexpected accidents. In this communication, we report the first preliminary results on the effect of ionizing radiation on the poly(acrylic acid) (PAA) – polyethyleneimine (PEI) complexes and their components as revealed by EPR spectroscopic studies. The obtained results clearly reveal that the yield of primary radicals trapped after irradiation is comparable in all the studied systems and the main processes are decarboxylation in the PAA moiety and proton loss in the PEI moiety. There are no evidences for main-chain scission, which might lead to the degradation of material properties (at least, at moderate doses), instead of this, the radiation-induced crosslinking looks plausible. Generally, it provides a positive forecast for the radiation resistance of such complexes. • Effect of ionizing radiation on interpolyelectrolyte complexes (IPECs) was studied by EPR. • The radicals produced in the polyacrylic acid – polyethyleneimine IPECs were identified. • No evidence for the radiation-induced destruction of the IPECs was found. • A plausible mechanism of the radiation-induced processes was proposed. [ABSTRACT FROM AUTHOR]

This review considers interpolyelectrolyte complexes, with a particular emphasis on advanced macromolecular co-assemblies based on polyionic species with nonlinear topology and on polymer–inorganic hybrids formed by interpolyelectrolyte complexes containing metal ions and/or metal nanoparticles. [ABSTRACT FROM AUTHOR]

This mini-review reports on complex macromolecular architectures (interpolyelectrolyte complexes) based on star-shaped polyelectrolytes. These complexes can be prepared in aqueous media via electrostatically driven co-assembly of star-shaped polyions (a) with oppositely charged linear homopolyelectrolytes or (b) with oppositely charged double hydrophilic (ionic/non-ionic) diblock copolymers. In case (a), the complexes can be water-soluble if the charge of the star-shaped macromolecule is only partially compensated by a linear polyion. In case (b), the complexes retain their solubility in aqueous media even under a full charge compensation of the polymeric components. In both cases, the complex macromolecular architectures based on star-shaped polyelectrolytes are characterized by a distinct compartmentalized structure of a micellar ('core-corona') type with an insoluble core, which is assembled from coupled monomer units of the oppositely charged polymeric components, and a hydrophilic, either ionic or non-ionic, corona. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Interpolymer interactions between the countercharged methacrylate copolymers Eudragit® RL 30D (polycation) and Eudragit® FS 30D (polyanion), were investigated in conditions mimicking the gastrointestinal environment. The formation of inter-macromolecular ionic bonds between Eudragit® RL 30D and Eudragit® FS 30D was investigated using FT-IR spectroscopy and modulated DSC. The FT-IR spectra of the tested polymeric matrices are characterized by visible changes in the observed IR region indicating the interaction between chains of two oppositely charged copolymers. A new band at 1570cm−1 appeared which was assigned to the absorption of the carboxylate groups that form the ionic bonds with the quaternary ammonium groups. Moreover, while increasing the pH values from pH 5.8 to 7.4, a decrease of the intensity of the band at 960cm−1 (quaternary ammonium group vibration) was observed. All binary mixtures were characterized by the presence of only one and narrow Tg, pointing to sample homogeneity, because of the compatibility of components. As a result of electrostatic interaction between the copolymer chains during swelling, the resulting Tg is decreased significantly and was dependent on the quantity of copolymers present in the structure of polycomplexes formed. Overall, the interaction between countercharged copolymers during passage in gastrointestinal tract can strongly modify the release profile of the model drug diclofenac sodium. [Copyright &y& Elsevier]

Abstract: We have studied the interpolyelectrolyte complexation in chloroform between polystyrene-block-poly(cetyltrimethylammonium acrylate), (PA− CTA+), and poly(2-(methacryloyloxy)ethyldimethylethyl-ammonium dodecyl sulfate) (quaternized poly(2-(dimethylamino)ethyl methacrylate) complexed with sodium dodecyl sulfate), (PDMAEMAQ+ DS−). Turbidimetry, dynamic/static light scattering, and transmission electron microscopy show the formation of large aggregated interpolyelectrolyte complex species, which are colloidally stable in chloroform or even chloroform-soluble if the certain conditions are met. We suggest such co-assemblies to be micellar species with a core assembled from electrostatically coupled fragments of the polymeric components. The corona is built up either from a mixture of polystyrene blocks and excessive fragments of (PDMAEMAQ+ DS−) chains or from a mixture of polystyrene blocks and excessive fragments of (PA− CTA+) blocks, depending on which polymeric component was taken in excess for the interpolyelectrolyte complexation. However, their real structures may deviate from such idealized consideration because of the non-equilibrium character of interpolyelectrolyte complexation in organic media of low polarity. [Copyright &y& Elsevier]

New interpolyelectrolyte complexes (IPECs) between oppositely charged types of Eudragit EPO and Eudragit L100 - 55 were investigated with a view to their application in oral controlled drug delivery systems. Monitoring of microenvironmental changes of polycomplex matrices in simulated gastro-intestinal fluids showed that all IPECs could have different pH-sensitivity characteristics. Evaluation of the diffusion transport properties of the investigated IPECs with diclofenac sodium confirmed that their swellability and release characteristics were closely correlated. The main possible mechanisms of control over the delivery of drugs to the desired regions of the gastro-intestinal tract are found. The results confirm that the proposed IPEC matrices have great potential to be used for controlled drug delivery. [ABSTRACT FROM AUTHOR]

New interpolyelectrolyte complexes (IPEC) between oppositely charged types of Eudragit, EPO and L100-55, with different molar ratios were synthesized with the aim of seeking potential carriers for oral delivery systems. Elemental analysis showed that the resulting polycomplexes had different compositions, with 0.36 < Z = [EPO]/[L100] < 1.81. The structural properties of the materials assessed by IR spectroscopy and modulated-temperature differential scanning calorimetry showed that all IPEC were stabilized by a cooperative system of ionic bonds, were chemically homogeneous, and were characterized by the presence of a single glass transition temperature. These properties suggest that the polycomplexes synthesized here have potential for further study as carriers for controlled drug release in specified parts of the gastrointestinal tract. [ABSTRACT FROM AUTHOR]

Abstract: Aim of this paper was that to prepare biocompatible, polyaspartamide based copolymers containing spermine or spermine/hydrophobic side chains able to condense nucleic acids and to transfect mammalian cells. Copolymers were prepared starting from α,β-poly-(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) and exploiting the reactive hydroxyl groups in the polymeric side chains by subsequent activation reactions to obtain PHEA-Spermine (PHEA-Spm) and PHEA-Spermine-Butyramide (PHEA-Spm-C4). Molecular, physico-chemical and biological characterization of copolymers and interpolyelectrolyte complexes with plasmid DNA was performed. Experimental results evidenced that these copolymers are able to form complexes with plasmid DNA already at low polycation/DNA weight ratio ranging from 0.75/1 to 2/1. Interpolyelectrolyte complexes with decreased size were obtained when increasing the polycation/DNA weight ratio, until nanosized dimensions were reached. Copolymers as well as complexes were not haemolytic and non toxic in vitro. In vitro cell transfection with PHEA derivatives showed good biocompatibility and high transfection efficiency (luciferase) in cancer cells in comparison with commercially available, but toxic transfection agents. [Copyright &y& Elsevier]

Abstract: The formation of a novel interpolyelectrolyte complex (IPEC) between basic butylated methacrylate copolymer and kappa-carrageenan was investigated and the product formed was characterized. Turbidity measurements and elemental analyses pointed to a 1:1 interaction of the repeating units. These results and FT-IR confirmed IPEC formation. Electronic microscopy images, particle size determination by image analysis and N2 (77K) adsorption measurements were consistent with a porous material. This IPEC formed presented very good flowability and compactibility. Two maxima were observed in the swelling behaviour as a function of pH. The performance of the IPEC as a matrix for controlled release of drugs was evaluated, using ibuprofen as a model drug. Release profiles were properly represented by a mathematical model, which indicates that the system releases ibuprofen in a zero-order manner. These profiles could be controlled by conveniently modifying the proportion of the IPEC in the tablets. [Copyright &y& Elsevier]

Abstract: Static/structural characteristics of non-covalent complexes, formed by terminally charged hyperbranched polymers and oppositely charged neutralizing linear polyelectrolytes, are examined by means of Brownian dynamics computer simulations. Excluded-volume, electrostatic and hydrodynamic interactions are taken into account in implicit solvent. Three pairs of complexes consisting of linear chains and hyperbranched molecules each bearing different molecular weight and distinctly diverse topologies are examined under conditions of varying electrostatic interactions. The findings from the present work demonstrate that through an appropriate modification of internal structure and external stimuli, key attributes of such complexes like size, shape and local density distribution, can be tuned at desired levels, rendering them promising candidates for a wide range of pertinent nanoscale applications. [Copyright &y& Elsevier]

Abstract: Controlled/‘living’ radical polymerization methods, including the versatile reversible addition–fragmentation chain transfer (RAFT) polymerization process, are rapidly moving to the forefront in construction of drug and gene delivery vehicles. The RAFT technique allows an unprecedented latitude in the synthesis of water soluble or amphiphilic architectures with precise dimensions and appropriate functionality for attachment and targeted delivery of diagnostic and therapeutic agents. This review focuses on the chemistry of the RAFT process and its potential for preparing well-defined block copolymers and conjugates capable of stimuli-responsive assembly and release of bioactive agents in the physiological environment. Recent examples of block copolymers with designed structures and segmental compositions responsive to changes in pH or temperature are reviewed and hurdles facing further development of these novel systems are discussed. [Copyright &y& Elsevier]

Artificial polymeric carriers for bioactive compounds, such as drugs and genes, are increasingly being reported in the literature. Most are poly- electrolytes aimed at being injected into body fluids that are composed of charged macromolecules (proteins, glycoproteins, poly(glycosamino glycane)s, polynucleotides, etc.). Many interactions can occur and lead to dramatic phenomena, such as polyelectrolyte complexation or substitution, cell aggregation and hemolysis. For the purpose of modeling and better understanding these interactions and their effects, a library of polyanions of the poly(L-lysine citramide)-type was interacted with the polycation poly(L-lysine) in aqueous media. Different fractions of complexes were generated by successive additions of aliquots of the polycation solution to the polyanion library solution by a titrating process. The two components, the polycation and the complex population of polyanions, were separated from the collected complex fractions by affinity chro- matography and then analyzed by aqueous SEC. Molecular weight selectivity was shown, the high molecular weight polyanion macromolecules precipitated first, while complexes involving smaller molecules were found to remain in solution. The data show the potential of affinity chromatography for studying inter-polyelectrolyte complexes and emphasizes the critical role that polydispersity can play when therapeutic charged macromolecules are injected into blood. [ABSTRACT FROM AUTHOR]

The micellization of ionic amphiphilic diblock copolymers, polyisobutylene-block-poly(methacrylic acid) (PIB-b-PMAA), with a constant degree of polymerization of the non-ionic block (DPn=20) and various degrees of polymerization of the polyelectrolyte block (DPn=100–425) was examined in aqueous media by means of fluorescence spectroscopy using pyrene as a polarity probe. The molar values of the critical micellization concentration (cmc) were found to be around 2×10−6 mol/l, being nearly independent of the length of the polyelectrolyte block as well as pH (in the range 6–9) and ionic strength (≤0.5 M NaCl) while the specific cmc values varied from 20 to 100 mg/l. Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) experiments provided evidence that aggregation numbers and hydrodynamic radii of the formed copolymer micelles are sensitive to variations of pH and ionic strength, indicating that these micelles might be ‘dynamic’ rather than ‘frozen’ ones. It was also shown by means of a combination of turbidimetry, analytical ultracentrifugation, fluorescence spectroscopy, SANS, and DLS that the formed copolymer micelles mixed with a strong cationic polyelectrolyte, poly(N-ethyl-4-vinylpyridinium bromide) at charge ratio Z=[+]/[−] not exceeding a certain critical value ZM<1, generate peculiar water-soluble micellar complex onion-like species, each containing a two-phase hydrophobic nucleus and a hydrophilic corona. The nucleus consists of a PIB core and a shell assembled from the fragments of water-insoluble interpolyelectrolyte complex. The corona is formed by the excess fragments of poly(sodium methacrylate) blocks not involved in complexation with poly(N-ethyl-4-vinylpyridinium bromide). [Copyright &y& Elsevier]

Interactions of a major whey protein, β-lactoglobulin (BLG), with an anionic polysaccharide, dextran sulfate (DS), were investigated by nephelometric titration and high-sensitivity differential scanning calorimetry at pH 2.5–7.0 and NaCl concentrations of 0–500 mM. The pH-dependences of the light scattering of the BLG−DS system revealed a maximum. Its position was dependent on the polysaccharide/protein ratio and salt concentration. Thermodynamic parameters of the denaturation of BLG in mixtures with DS were determined at different pH and salt concentrations. Conformational stability of BLG in the BLG–DS complexes was shown to either increase or decrease depending on the solution conditions and complex composition. The binding curves of BLG to DS were calculated from the light scattering and calorimetric data and analyzed using various binding models including the Langmuir and McGhee–von Hippel models as well as a stoichiometric interpolyelectrolyte reaction. Mechanisms responsible for changes in the BLG oligomer structure and conformational stability induced by the complex formation with the polysaccharide were proposed. [Display omitted] • BLG–DS complexes form at pH 3.0–pI BLG and NaCl concentration up to 0.5 M. • The complex formation can result in the dissociation of BLG dimer. • Stability of BLG is defined by charge-charge or charge-dipole interactions with DS. • Stoichiometric BLG–DS complexes are formed at high ionic strength. [ABSTRACT FROM AUTHOR]

• Benznidazole-loaded multiparticulate drug delivery systems (BZ-MDDS) were in vivo studied. • BZ-MDDS showed trypanocidal efficacy at conventional or low doses of BZ. • BZ-MDDS reduced heart and liver injury, increasing Chagas disease treatment safety. • BZ-MDDS exhibited an improved preclinical performance for Chagas disease treatment. Benznidazole (BZ) is a first-line drug for the treatment of Chagas disease; however, it presents several disadvantages that could hamper its therapeutic success. Multiparticulate drug delivery systems (MDDS) are promising carriers to improve the performance of drugs. We developed BZ-loaded MDDS intended for improving Chagas disease therapy. To assess their efficacy and safety, Trypanosoma (T) cruzi infected BALB/c mice were orally treated with free BZ or BZ-MDDS at different regimens (doses of 50 and 100 mg/kg/day, administered daily or at 2- or 5-days intervals) and compared with infected non-treated (INT) mice. At 100 mg/kg/day, independent of the administration regimen, both treatments were able to override the parasitemia, and at 50 mg/kg/day significantly reduced it compared to INT mice. BZ-MDDS at a dose of 100 mg/kg/day administered every 5 days (BZ-MDDS 100–13d) induced the lowest cardiac parasite load, indicating an improved efficacy with lower total dose of BZ when loaded to the MDDS. Reactive oxygen species produced by leukocytes were higher in INT and mice treated with BZ at 50 mg/kg/day compared to 100 mg/kg/day, likely because of persistent infection. BZ-MDDS treatments markedly reduced heart and liver injury markers compared to INT mice and those receiving the standard treatment. Therefore, BZ-MDDS exhibited enhanced activity against T. cruzi infection even at lower doses and reduced administration frequency compared to free BZ while increasing the treatment safety. They likely avoid undesired side effects of BZ by keeping a sustained concentration, avoiding plasmatic drug peaks. BZ-MDDS evidenced significant improvements in experimental Chagas disease treatment and can be considered as a potential improved therapeutic alternative against this illness. [Display omitted] [ABSTRACT FROM AUTHOR]