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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.

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.

Stabilization of the enzymes under stress conditions is of special interest for modern biochemistry, bioengineering, as well as for formulation and target delivery of protein-based drugs. Aiming to achieve an efficient stabilization at elevated temperature with no influence on the enzyme under normal conditions, we studied chaperone-like activity of thermoresponsive polymers based on poly(dimethylaminoethyl methacrylate) (PDMAEMA) toward two different proteins, glyceraldehyde-3-phosphate dehydrogenase and chicken egg lysozyme. The polymers has been shown to do not interact with the folded protein at room temperature but form a complex upon heating to either protein unfolding or polymer phase transition temperature. A PDMAEMA-PEO block copolymer with a dodecyl end-group (d-PDMAEMA-PEO) as well as PDMAEMA-PEO without the dodecyl groups protected the denatured protein against aggregation in contrast to PDMAEMA homopolymer. No effect of the polymers on the enzymatic activity of the client protein was observed at room temperature. The polymers also partially protected the enzyme against inactivation at high temperature. The results provide a platform for creation of artificial chaperones with unfolded protein recognition which is a major feature of natural chaperones. (C) 2018 Elsevier B.V. All rights reserved.

At present, a large amount of research works from experimental and theoretical points of view have been done on interpolyelectrolyte complexes formed by electrostatic interactions and/or interpolymer complexes stabilized by hydrogen bonds. On the contrary, relatively less attention has been given to polymer-polymer complex formation with synthetic polyampholytes. In this review the complexation of polyampholytes with polyelectrolytes is considered from theoretical and application points of view. Formation of intra- and interpolyelectrolyte complexes of random, regular, block, dendritic polyampholytes are outlined. The separate subchapter is devoted to amphoteric behavior of interpolyelectrolyte complexes. The realization of so-called “isoelectric effect” for interpolyelectrolyte complexes of water-soluble polyampholytes, amphoteric hydrogels and cryogels with respect to surfactants, dye molecules, polyelectrolytes and proteins is demonstrated.

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.

This article is part of the Supramolecular Chemistry at Interfaces special issue. The layer-by-layer (LbL) assembly of salt-containing nonstoichiometric polyelectrolyte complexes (PECs) with oppositely charged uncomplexed polyelectrolyte for the fabrication of dewetting-induced porous polymeric films has been systematically investigated. Salt-containing poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) complexes (noted as PAH-PAA) with a molar excess of PAH were LbL assembled with polyanion poly(sodium 4-styrenesulfonate) (PSS) to produce PSS/PAH-PAA films. The structure of the PAH-PAA complexes is dependent on the concentration of NaCl added to their aqueous dispersions, which can be used to tailor the structure of the LbLassembled PSS/PAH-PAA films. Porous PSS/PAH-PAA films are fabricated when salt-containing PAH-PAA complexes with a large amount of added NaCl are used for LbL assembly with PSS. In-situ and ex-situ atomic force microscopy measurements disclose that the dewetting process composed of pore nucleation and pore growth steps leads to the formation of pores in the LbL-assembled PSS/PAH-PAA films. The present study provides a facile way to fabricate porous polymeric films by dewetting LbL-assembled polymeric films comprising salt-containing PECs. Refereed/Peer-reviewed

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.

We have investigated the formation of complexes between negatively charged niosomal vesicles (hybrid niosomes), built up by dicethylphosphate [DCP], Tween 20 and Cholesterol, and three linear differently charged cationic polyions, such as alpha-polylysine, epsilon-polylysine, and polyethylvinylpyridinium bromide [PEVP], with two different substitution degrees. Our aim is to investigate the interaction mechanism between anionic-nonionic vesicles (hybrid niosomes) and linear polycations, characterizing the resulting aggregates in view of possible applications of these composite colloidal particles as vectors for multidrug delivery. In order to explore the aggregation behavior of the complexes and to gain information on the stability of the single niosomal vesicles within the aggregates, we employed dynamic light scattering (DLS), laser Doppler electrophoretic measurements, and fluorescence measurement techniques. The overall phenomenology is well described in terms of the re-entrant condensation and charge inversion behavior, observed in different colloidal systems. The aggregate size and overall charge depend on the charge ratio between vesicles and polyions, and the aggregates reach their maximum size at the point of charge inversion (re-entrant condensation). While the overall phenomenology is similar for all three polycations investigated, the stability and the integrity of the hybrid niosomal vesicles forming the aggregates strongly depend on the chemical structure of the polycations. The role of the polycations in the aggregation process is discussed by identifying specific interactions with the niosomal membrane, pointing out their importance for possible applications as drug delivery vectors.

The interaction between protein and soluble organic matter is studied through layer-by-layer assembly of lysozyme (LSZ) and purified Aldrich humic acid (PAHA) at a solid surface (2-D) and in solution (3-D). By bringing a silica surface in alternating contact with solutions of LSZ and PAHA a layer-by-layer LSZ-PAHA assembly is formed. At pH 5 the negative charge density of PAHA is about 3 times that of the positive LSZ; the layers of LSZ and PAHA are stable and the adsorbed amounts decrease with increasing ionic strength. The mass ratios PAHA/LSZ in the layers depend on the ionic strength; K+ incorporation is relatively large (similar to 25%) when PAHA is the outer layer of the assembly. At pH 6 and 8, and moderate ionic strength (0-100 mmol L-1 KCl) the assembly is accompanied by partial solubilization of positive LSZ by the much more negative PAHA followed by desorption of the complex. The solubilization increases with increasing pH, and decreases with increasing KCl concentration. At 400 mmol L-1 KCl the electrostatic interactions are so well screened that the assembly is no longer accompanied by layer erosion. Assembly of PAHA and LSZ in solution is also investigated at pH 5 and 5 mmol L-1 KCl. The PAHA/LSZ mass ratio at the iso-electric point of the assembly depends on the order of the addition. When LSZ is added to the negative assembly K+ is incorporated in the complex, but when PAHA is added to the positive assembly PAHA and LSZ neutralize each other. (C) 2014 Elsevier Inc. All rights reserved.

The interactions between a cationic polymer, poly(2-dimethylamino)ethyl methacrylate (pDMAEMA), and negatively charged rhodamine-labeled 25-mer phosphodiester oligonucleotides (Rh-ONs) were studied by fluorescence fluctuation spectroscopy and other techniques. The composition of the pDMAEMA/Rh-ON complexes was investigated as a function of the charge ratio (+/-) by increasing the pDMAEMA concentration and keeping the Rh-ON concentration constant. We applied two different methods for analyzing the fluorescence fluctuation profiles of the pDMAEMA/Rh-ON complexes, which depended on their composition. First, we analyzed the data with the photon counting histogram (PCH) technique, which determines the molecular brightness and the concentration of fluorophores (Chen et al, 1999). A particular challenge for the data analysis is the occurrence of sudden fluorescence bursts in the fluorescence fluctuation profiles, which are linked to the appearance of multimolecular complexes (i. e. when several Rh-ONs were present in one complex). A quantitative interpretation of the analysis for the complexes remains challenging and is connected to the rarity of the fluorescent bursts, which do not provide sufficient data statistics. To specifically address the problem of the fluorescent bursts we employed a method described by Van Craenenbroeck et al. (1999). This method, applicable only when data were integrated over much longer time bins, allowed us to estimate the number of fluorescence bursts which could be considered as a relative measure of the amount of multimolecular complexes present. When monomolecular complexes were formed, i. e. at high values of the charge ratio, highly intense fluorescence peaks were not present and the interpretation of the PCH analysis was more straightforward. The molecular brightness of the species (epsilon), as revealed from PCH analysis, was greater than epsilon for the free Rh-ONs, indicating that the Rh-ONs were attached to pDMAEMA chains.