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Based on published research on modifying the structure of water and water-containing systems, we assess external influence methods: temperature, magnetic field, light radiation, and their combination. We evaluate changes in the electrophysical, photo- and pH-metric biological, therapeutic, and other properties of water systems using non-destructive electrophysical research methods, i.e., thermometry, pH, laser interference, dynamic light scattering, microelectrophoresis, conductivity, surface tension, dielectric constant, polarimetric measurements, atomic force microscopy, and UV and EPR spectroscopy. The effects of temperature or magnetic field lead to a change in the content and size of water clusters, and physicochemical, biological, therapeutic, and other changes in the properties of water and water-containing systems. The combined effect of a magnetic field and curative mud and the impact of magnetised mineral water have a more pronounced therapeutic effect than only mineral water or curative mud. The data presented indirectly indicate structural changes in water and water-containing systems. We conclude that the primary mechanism of action of a magnetic field, light, or a combination of these factors on water and water-containing systems, including mineral water and therapeutic mud, is a change in the structure of water.

When creating new materials, surface modification is an effective means of controlling the characteristics and the colloidal properties of cellulose nanocrystals (CNC), thereby increasing its compatibility with composite matrices. In this paper, the CNC surface is modified in aqueous media by cyanoethyl groups, followed by the hydrolysis of grafted nitrile groups. Particles having a surface composition close to that of native cellulose (N-CNC) and particles with sulfated surfaces (S-CNC) are used. The influence of the functional composition of CNC, as well as that of temperature and the ratio of reagents on the modified particles is investigated. It is shown that under identical synthesis conditions, a higher degree of cyanoethylation can be achieved for N-CNC. Particles modified with only nitrile groups and those with a polyfunctional composition modified with amide and carboxyl groups are obtained. Atomic force microscopy (AFM) and X-Ray diffraction (XRD) data indicate the preservation of both the morphology and structure of CNC post modification. The modified CNC particles are characterized by elemental analysis, synchronous thermal analysis (STA) and Fourier-transform infrared (FTIR) spectroscopy. The thermal stability of the resulting particles is close to that of the starting materials but higher for N-CNC and its derivatives. The acid-base properties of the CNC surface are established using a combination of methods (photometric measurements), namely potentiometric titration, dynamic light scattering, and microelectrophoresis. It is shown that the aggregative stability of modified particles along with the activity and number of acid-base centers on their surface increases sharply after the hydrolysis of nitrile groups.

The purpose is to study the capability of the electric light scattering to determine the point of zero charge of native protein macromolecules adsorbed on colloid particles at low ionic strength and without using buffers. The chosen protein and particles are cytochrome c (cytC, globular haemoproteid) and montmorillonite (MM, negatively charged plate-like crystal). The pH-dependence of the electric polarizability γ(pH) in the range pH 6–11 shows minimum which coincides with the isoelectric point determined by measuring the electrophoretic mobility μ(pH) of the cytC-MM particles.

The pH-dependent surface charging of tellurium (IV) oxide has been studied. The isoelectric point (IEP) of tellurium (IV) oxide was determined by microelectrophoresis in various 1-1 electrolytes over a concentration range of 0.001–0.1 M. In all electrolytes studied and irrespective of their concentration the zeta potential of TeO2 was negative over the pH range 3–12. In other words the IEP of TeO2 is at pH below 3 (if any). TeO2 specifically adsorbs ionic surfactants, and their presence strongly affects the zeta potential. In contrast the effect of multivalent inorganic ions on the zeta potential of TeO2 is rather insignificant (no shift in the IEP). In this respect TeO2 is very different from metal oxides.

Flavonoid compounds are known for their antibacterial, anti-inflammatory, and anticancer properties. Therefore, they can influence membrane properties that interest us, modifying both their structure and functions. We used kaempferol (K) and myricetin (M) as representatives of this group. We investigated the influence of the abovementioned compounds on model cell membranes’ properties (i.e., Langmuir monolayers and liposomes). The basic research methods used in these studies were the Langmuir method with Brewster angle microscopy and microelectrophoresis. The π–A isotherms were registered for the pure components and mixtures of these compounds with phosphatidylcholine (PC) in appropriate volume ratios. Using mathematical equations, we established that kaempferol, myricetin, and the lipids formed complexes at 1:1 ratios. We derived the parameters characterizing the formed complexes, i.e., the surfaces occupied by the complexes and the stability constants of the formed complexes. Using the microelectrophoretic method, we determined the dependence of the lipid membranes’ surface charge density as a function of the pH (in the range of 2 to 10) of the electrolyte solution. The presented results indicate that the PC membrane’s modification with kaempferol or myricetin affected changes in the surface charge density and isoelectric point values.

We propose herein a theoretical model describing the effect of fatal ethanol poisoning on the equilibria between cell membranes and the surrounding ions. Using this model, we determined the parameters characterizing the interaction between the electrolyte solution’s ions and the functional groups on the blood cells’ surface. Via the application of mathematical equations, we calculated the total surface concentrations of the acidic and basic groups, cA and cB, and their association constants with solution ions, KAH and KBOH. Using the determined parameters and mathematical equations’ values, we calculated the theoretical surface charge density values. We verified the proposed model by comparing these values with experimental data, which were selected based on measurements of the electrophoretic mobility of erythrocyte and thrombocyte membranes. Compatibility of the experimental and theoretical surface charge density values was observed in the range of pH 2–8, while deviations were observed at higher pH values.

Elucidating electrokinetic stability by which surface charges regulate toxins interaction with erythrocytes is crucial for understanding the cell functionality. Electrokinetic properties of human erythrocytes upon treatment of Vipoxin, phospholipase A2 (PLA2) and Vipoxin acidic component (VAC), isolated from Vipera ammodytes meridionalis venom were studied using particle microelectrophoresis. PLA2 and Vipoxin treatments alter the osmotic fragility of erythrocyte membranes. The increased stability of cells upon viper toxins is presented by the increased zeta potential of erythrocytes before sedimentation of cells during electric field applied preventing the aggregation of cells. Lipid peroxidation of low dose toxin-treated erythrocytes shows reduced LP products compared to untreated cells. The apparent proton efflux and conductivity assays are performed and the effectiveness PLA2 > Vipoxin>VAC is discussed. The reported results open perspectives to a further investigation of the electrokinetic properties of the membrane after viper toxins treatment to shed light on the molecular mechanisms driving the mechanisms of inflammation and neurodegenerative diseases

Thylakoid membranes of photosynthetic plant chloroplasts are involved in a wide range of energy producing pathways. Their stacking can be employed in order to provide increased surface area for biocatalytic purposes. Here we probe the aggregate formation of higher plants' thylakoids using low-molecular poly-l-lysine as an electrostatic polymer linker in low ionic strength media. Microelectrophoresis, actinic light scattering, millisecond-delayed fluorescence and free radical production of thylakoid membranes are measured and analyzed in the presence of the cationic polypeptide to track its influence on the surface electrical properties, the electron-transport processes and the proton gradient accumulation across membranes. Enhanced proton gradient in polylysine-treated thylakoids is obtained upon illumination due to alterations of the proton intake across the membrane resulting from the non-specific electrostatic interactions of the cationic polypeptide with thylakoids. We report lower rates of lipid peroxidation in polylysine-treated thylakoids measured both in the dark and under illumination in salt-free medium. The gained insight on the effect of polycations on photosynthetic membranes may be used in future developments of thylakoid-based approaches for energy transfer applications.

An online combination of isotachophoresis (ITP) and capillary zone electrophoresis (CZE) was employed on a microchip with a column-coupling technology for the determination of homocysteine in various body fluids. ITP with its high concentration ability was used as a sample pretreatment and injection technique for CZE, which facilitated the rapid and sensitive determination of homocysteine. The resolution of the analyte from other constituents present in real complex samples was enhanced by discrete spacers, which were added to the injected sample. A solid-phase microextraction (SPME) pretreatment technique based on silver- and barium-form resins was used prior to the ITP-CZE analysis to remove high concentrations of chloride and sulfate naturally present in the analyzed samples. The combination of the micropretreatment and microelectrophoresis techniques facilitated the determination of trace concentrations of homocysteine in samples of urine and saliva

Stimuli-responsive particles of crosslinked poly-N-vinylcaprolactam and poly-N,N-(dimethylamino)ethyl methacrylate (microgels) have been synthesized in oil-in-water emulsion without using of emulsifier. Dispersions of spherical particles of about 200 nm in size rather narrowly distributed as defined by dynamic light scattering and TEM microscopy were stable in time in case of 50 and more mol. % of N,N-(dimethylamino)ethyl methacrylate. Zeta potential, measured by laser Doppler microelectrophoresis, revealed negative (-4.4 mV) and low positive (+6.6 mV) charges on particle surface. Positive charge in the case of 70 mol. % of N,N-(dimethylamino)ethyl methacrylate is provided by the protonated nitrogen atom of the monomer on the interphase surface. Low positive and negative instead of expected more positive value of zeta potential can be explained by specific sorption SO42- ions on the particle surface during the polymerization, which are formed by decomposition of initiator K2S2O8. Investigation of the effect of pH on the stability and particles size of the microgel with 50 mol. % of N,N-(dimethylamino)ethyl methacrylate showed that they remain stable in a wide range of pH values. An increase in the size of particles caused by polyelectrolyte swelling is observed in an acidic medium. Synthesized microgels exhibit thermosensitive properties. It is shown that, with an increase of N,N-(dimethylamino)ethyl methacrylate units, the volume phase transition temperature shifts to a lower temperatures, while the degree of particle compression is decreasing. It should also be noted that the change in particles size under the effect of temperature is reversible.

The aim of research was first, to study the interactions between components for finding out how pH effects on ζ-potential, dewatering rate and retention of TiO2/MCC mixtures with/without titanyl sulphate in order to find a way to titanyl sulphate hydrolysis in a papermaking process. The maximum heterocoagulation interactions between TiO2, MCC and TiOSO4 were revealed in the pH range 4.4–5.6. Second, handsheets made from refined chemical pulp, titanyl sulphate and TiO2 at pH 4.4 were investigated. The handsheets were formed and studied conventionally and with scanning electron microscopy (SEM). It was shown that titanyl sulphate hydrolysis leads to formation of translucent polymer film covering the fibres and TiO2 particles. The maximum first-pass ash retention reached is lower than its values usually obtained with an organic polymer. Addition of titanyl sulphate led to higher strength, but lowered opacity and brightness compared to a reference sample. The use of low dosage of titanyl sulphate together with a filler improved air permeability. As there exist certain advantages/disadvantages of titanyl sulphate application, extended research is needed to find suitable conditions for its applying to mass paper and board grades production.

A number of new membrane anchors based on water-soluble aminoglycerides with geraniol fragments have been synthesized. A biomimetic approach was used based on the design of meroterpenes structurally similar to archaeal lipids. Turbidimetry and laser Doppler microelectrophoresis showed that the synthesized compounds were incorporated into unilamellar dipalmitoylphosphatidylcholine (DPPC) vesicles.

As a bioactive and functional polysaccharide, sea cucumber fucoidan has received increasing attention. Chain conformation and physicochemical properties of fucoidan extracted from Thelenota ananas (Ta-FUC) was investigated by utilizing HPSEC-MALLS-Visc-RI, microelectrophoresis and steady shear measurements. The conformation parameter α s (0.61 ± 0.02), the Mark-Houwink-Kuhn-Sakurada exponent α η (0.92 ± 0.01), α h (0.64 ± 0.01) and the Smidsrod-Haug stiffness parameter B (0.036 ± 0.010) consistently manifested that Ta-FUC adopted a semi-flexible coil conformation in NaCl solution. Based on a wormlike cylinder model, stiffness parameters, including persistence length q (13.27 ± 0.80 nm) and cylinder diameter d (0.79 nm), were calculated. This polysaccharide demonstrated shear-thinning rheological behaviour, and critical concentration from dilute to semidilute concentration regime was determined as 3.6 mg/ml. Ta-FUC exhibited as a negative polyelectrolyte in wide pH and ionic strength ranges. These molecular characteristics and physicochemical properties would facilitate further application of Ta-FUC as a functional ingredient in food.

Срыв адаптационных возможностей организма может стать патогенетической основой различных заболеваний. Длительный выброс адреналина в кровь вызывает кататоксические эффекты, что делает актуальным поиск эффективных средств и методов коррекции гиперадреналинемии. Цель работы - изучение влияния низкоинтенсивного лазерного излучения (НИЛИ) на электрофоретическую подвижность эритроцитов, процессы липопероксидации и структуру надпочечников при адреналовой токсемии у крыс. Методика. Адреналовую токсемию моделировали внутрибрюшинным введением адреналина-гидрохлорида (0,1 мг/кг). Животным 1-й группы вводили только адреналин, животных 2-й - через 30 мин после введения адреналина облучали НИЛИ, крысы 3-й группы получали только воздействие НИЛИ, контролем служили интактные животные (4-я группа). Воздействие НИЛИ проводилось на затылочную область в течение 10 мин. В качестве источника излучения применяли аппарат лазерный терапевтический Успех (ГП Восход ), основанный на низкоинтенсивном импульсном излучении (длина волны - 0,890,05 мкм, частота импульсов 415 Гц, плотность средней мощности излучения - 193 мкВт/см2, площадь облучаемой поверхности 20 см2). Забор крови производили через 1 ч, 24 ч и 1 нед после начала эксперимента. Определяли уровень малонового диальдегида по реакции с тиабарбитуровой кислотой электрофоретическую подвижность эритроцитов изучали методом микроэлектрофореза. Структуру надпочечников изучали морфологическими методами. Результаты. Показано, что НИЛИ на фоне адреналина (2-я группа) через 1 нед нивелировало снижение электрофоретической подвижности эритроцитов, восстанавливало уровень малонового диальдегида до значений интактной группы. Морфологическая картина надпочечников в этой группе не отличалась от таковой у интактных животных, тогда как при действии адреналина (1-я группа) не происходило восстановления исследуемых показателей до физиологической нормы. Заключение. Полученные в ходе эксперимента данные свидетельствуют о корригирующем действии низкоинтенсивного лазерного излучения при адреналовой токсемии у животных. Механизм действия низкоинтенсивного лазерного излучения, вероятно, носит системный характер и связан с воздействием на стресс-реализующие системы организма., Maladaptation results in the third stage of stress, exhaustion, and, thus, may underlie many diseases. Prolonged release of epinephrine into blood exerts catatoxic effects therefore, searching for effective methods for correction of hyperadrenalinemia is relevant. Presently, low-intensity laser therapy (LILT) is commonly used in medicine. However, the introduction of LILT to clinical practice is largely empirical. The aim of this study was to analyze the effect of LILT on electrokinetic potential of red blood cells (RBC), lipid peroxidation (LPO), and the morphology of adrenal glands in adrenal toxemia in rats. Methods. Adrenal toxemia was modeled by intraperitoneal administration of epinephrine hydrochloride (0.1 mg/kg) to rats. Animals of group 1 received epinephrine alone animals of group 2 received LILT 30 min prior to epinephrine administration rats of group 3 received LILT alone and intact rats of group 4 were used as control. Blood was withdrawn at one hour, 24 h, and one week of the experiment onset. The RBC zeta potential, which characterizes the morpho-functional state of membranes, was determined by measuring the effect of low-intensity laser therapy on RBC electrophoretic mobility using microelectrophoresis. LPO as an indicator of cell membrane injury was determined by concentration of malonic dialdehyde (MDA). The structure of adrenal glands was studied histologically. Results. LILT combined with epinephrine (group 2) alleviated the decrease in RBC electrophoretic mobility and restored the MDA level to values of the intact group at one week. Morphological structure of adrenal glands in group 2 did not differ from that in control whereas epinephrine (group 1) did not restore the study parameters to physiologically normal values. Conclusion. The study showed that LILT exerted a correcting effect in experimental adrenal toxemia. The mechanism of this effect is likely systemic and related with the effect on stress systems of the body., №4 (2019)

Divalent ions, in particular calcium ions, constitute important macroelements in living organisms. They are also found in cell membranes, i.e., ensuring their stabilization or participating in synaptic transmission of nerve impulses. The aim of this work is to describe the interactions of divalent ions, such as Ca2+, Ba2+, and Sr2+, in electrolytes with the functional groups on the surface of liposomes formed from phosphatidylcholine (PC). Microelectrophoresis is used to determine the surface charge density as a function of pH. The interactions between ions found in solution and the functional groups of PC are described with the use of a seven-equilibrium mathematical model. Using this model along with experimental data on the charge density of the membrane surface, the association constants characterizing this equilibrium are determined. These parameters are used to calculate the theoretical model curves. The validity of the proposed model is confirmed by comparing the theoretically calculated changes in charge density on the liposome surface with the experimental results.

In this paper, we examined the effect of adsorbed monovalent ions on the surface charge of liposomal membranes formed from neutral (sphingomyelin), anionic (phosphatidylinositol) lipids mixed in various ratios. The surface charge density of the membrane was determined from electrophoretic mobility measurements at various pHs of solution. A four-quilibria model describing adsorption of ions on the sphingomyelin (SM) membrane and a two-equilibria model describing adsorption of ions on the phosphatidylinositol (PI) membrane was presented. We proposed a mathematical model for characterizing these equilibria. Using these models, together with experimental data of the membrane surface charge density, we determined association constants characterizing the equilibria. The correctness of the proposed model was proven by comparing the theoretical charge variation curves for SM and PI membranes with the experimental date.

The importance of fungicides uses to maintain healthy crops and reliable, high-quality yields poses environmental issues due to the water and soil contaminations. The montmorillonite is known as efficient adsorbent for many pesticides, while the organo modification enabled to use them in wider range of applications. In this study, the fungicide fludioxonil (FDX) was adsorbed on raw and organo-modified Patagonian montmorillonite. The effects of the organo treatment as well as the FDX adsorption on the surface properties were investigated by X-ray diffraction, microelectrophoresis and inverse gas chromatography. The importance of the organo treatment was revealed both for the changes in the surface properties (dispersive component of the surface energy, nanoroughness and surface acidity as well as zeta-potential) and for the adsorption of FDX as it enabled increase two times respect to the pristine montmorillonite. Fil: Flores, Federico Manuel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Gamba, Martina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Torres Sanchez, Rosa Maria. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Brendlé, Eric. Adscientis; Francia Fil: Brendlé, Jocelyne. Adscientis; Francia

Interactions of alkali metal cations (Li+, Na+, K+, Cs+) with phosphatidylcholine (PC) liposomal membranes were investigated through experimental studies and theoretical considerations. Using a microelectrophoresis technique, charge densities of experimental membrane surfaces were measured as a function of the pH of electrolyte solutions. Equilibria between the PC liposomal membranes and monovalent ions were mathematically analyzed and described quantitatively through a previously proposed theoretical model. Association constants between functional groups of PC and the studied ions were determined and used to define theoretical curves of membrane surface charge density versus pH. Theoretical and experimental data were compared to verify the model. The PC membrane was found to have the highest affinity for lithium ions, among the ions tested.

This Review describes how in the period 1940-1959 cell electrophoresis (in the earlier literature often referred to as 'microelectrophoresis') was used to explore the surface chemistry of cells. Using the erythrocyte as a suitable model for the study of biological membranes, the early investigators were agreed on the presence of negatively charged groups at the surface of this cell. The contemporary dogma was that these were phosphate groups associated with phospholipids. Work in the 1960s, particularly on changes in the electrokinetic properties of erythrocytes following treatment with proteolytic enzymes, lead to the realization that the negatively charged groups at the red cell surface are predominantly due to sialic acids carried on glycoproteins. It quickly became apparent from cell electrophoresis that sialic acids have a ubiquitous presence on the surface of animal cells. This finding required that any complete model of the plasma membrane must include glycosylated molecules at the cell periphery, thus laying the foundations for the field termed 'Glycobiology of the Cell Surface'.

Interactions between trivalent metal ions (Al3+, In3+, La3+) and phosphatidylcholine (PC) liposomes are studied by microelectrophoresis. The dependence of the PC membrane surface charge density and zeta potential on $p{\rm H}$ ( $p{\rm H}$ range from 2 to 10) of the aqueous metal chloride solutions is determined. The obtained results indicate the adsorption of Al3+, In3+ and La3+ ions on phosphatidylcholine model membranes, leading to changes in the electrical properties of the membranes. The theoretical considerations on equilibria occurring between phosphatidylcholine liposomal membrane and trivalent metal ions are presented. A mathematical model describing the interactions in a quantitative way is proposed.

We examined the adsorption of Na+, Cl−, H+, and OH− ions on phosphatidylcholine-cardiolipin liposomal membrane surfaces using both experimental and theoretical approaches. The dependence of the membrane surface charge density on the pH of the electrolyte solution was determined using microelectrophoresis. A mathematical model comprising eight equilibria was formulated to describe the adsorption of the electrolyte ions. Combination of this model with experimental surface charge density values enabled the determination of association constants. From the good agreement between the experimental and theoretical data, we can conclude that the assumed model is compatible with the experimental data.

In the present study, particular emphasis was put on the effects of the type of functional groups of anionic and cationic polyacrylamide (PAM) and solution pH on the mechanism of polymer adsorption on the surface of dispersed alumina. The polymer-adsorbed amount, surface charge density and zeta potential of solid particles without and with PAM, as well as the stability of Al2O3 suspension containing the polymer, were determined. For this purpose, the spectrophotometry, potentiometric titration, microelectrophoresis and turbidimetry were applied. It was shown that adsorption of anionic PAM decreases with the pH rise, whereas in the case of cationic PAM, it increases. High adsorption level is a result of more coiled structure of adsorbed macromolecules. The anionic PAM has greater impact on the suspension stability deterioration in comparison to the cationic polymer in the whole range of studied pH values. The more pronounced effect of alumina suspension destabilization in the anionic PAM presence was obtained at pH 6, at which solid surface charge neutralization occurs.

The effects of solution pH and degree of polymer hydrolysis on the adsorption mechanism of anionic polyacrylamide (PAM) on the alumina surface were investigated. The spectrophotometry, potentiometric titration, microelectrophoresis and thermogravimetry were applied to determine polymer adsorbed amount, surface charge density and zeta potential of solid particles in the presence and absence of PVA, as well as thermal characteristics of Al2O3 surface with the adsorbed polymer, respectively. The obtained results indicate that adsorption of PAM decreases with the increasing pH. Additionally, the polymer adsorption level depends on its degree of hydrolysis (which is equivalent to the content of carboxyl groups).

We carry out frequency-dependent solvent impedance measurements and alternating current (ac) colloid microelectrophoresis experiments in partially polar solvents in the low-frequency regime (0.25 Hz ≤ f ≤ 10 Hz). Solvent electrode polarization effects are quantified first in partially polar solvent mixtures containing bromocyclohexane (CHB). We find that the polarization capacitance from electrode polarization exhibits a clear power law behavior Cp = Cp0 f–m with power law exponent m = 0.25 ± 0.04. Once we account for electrode polarization effects, we are able to obtain quantitative mobilities in the low-frequency regime from our ac microelectrophoresis measurements; for these measurements, we use poly(methyl methacrylate colloids that are gravitationally confined to a plane while suspended in a low-polar solvent mixture of cis–trans decahydronapthalene and CHB. We find that the dimensionless electrophoretic mobility is constant, consistent with expectations for frequencies below the ion-diffusion freque...

The influence of the lysozyme and serum albumin in their native and amyloid forms on the electrokinetic behavior of the negatively charged uni- and multilamellar liposomes from the zwitterionic lipid phosphatidylcholine and anionic lipid cardiolipin has been investigated using the microelectrophoresis technique. The zeta - potential, the surface electrostatic potential and surface charge density of the lipid vesicles have been determined upon varying the lipid-to-protein molar ratio. The complex dependencies of the electrophoretic mobility on the protein concentration and reversal of the surface charge observed for the multilamellar vesicles have been explained by the multilayer protein adsorption on the liposomal surface. It has been found that the native and fibrillar proteins differ in their ability to modify the charge state of the model membranes.

The effects of solution pH and the content of cationic groups in polyacrylamide (PAM) macromolecules on the stability mechanism of aqueous alumina suspension were investigated. The following experimental techniques were applied: spectrophotometry, potentiometric titration, microelectrophoresis, viscosimetry and turbidimetry. They enable determination of polymer adsorbed amount, surface charge density and zeta potential of solid particles in the presence and absence of PAM, as well as thickness of polymer adsorption layer, size of macromolecules in the solution and stability of the Al2O3–polymer systems, respectively. The obtained results indicate that adsorption of PAM increases with the increasing pH, whereas the thickness of polymeric adsorption layer decreases. Additionally, the greater the number of cationic groups in the PAM chains is, the higher adsorption was found. The polymer presence influences on the alumina suspension stability. At pH 3 and 6 the slight deterioration of stability conditions of solid particle covered with polyacrylamide was observed. At pH 9 the systems containing polymer are unstable, similarly to the suspension without PAM, but the mechanism of their destabilization is different.

g r a p h i c a l a b s t r a c t a b s t r a c t The fine fraction of carbon black (CB) sample N234, initially prepared by the furnace process, was obtained by sieving and it was then dispersed in aqueous medium at various aqueous phase pH. Further, adsorp- tion from water onto this non porous CB particles, of polystyrene-polyethylene oxide (PS-PEO), non ionic diblock copolymers, having molecular weights, Mw = 2000 and Mw = 4000 g/mol, were investigated at ambient temperature. For the bare CB particles, prepared in the absence of copolymers, the TEM micrographs show aggregates and/or agglomerates having sizes depending of the aqueous phase pH, and formed from fused primary particles having sizes in the range 13-17 nm. These aggregates develop intra-porosity that result from their branching shape. The CB bare particles prepared in acidic aqueous dispersion form mostly ellipsoidal agglomerates having sizes exceeding 500 nm. However, by increasing the pH of the medium from pH = 3 to pH = 10, and after drying the CB dispersion, aggregates shaped as "bunch" of grapes and having smaller sizes are observed by TEM. The microelectrophoresis studies of these dispersions indicate that the CB particles are positively and negatively surface charged at pH val- ues, respectively, below and above the Isoelectrical point (IEP) which is about pH ∼ 6. Such electrokinetic behavior of the CB aqueous dispersion results from the presence on the CB surface of acidic and basic functional groups. However, upon PS-PEO copolymers adsorption onto CB, reduction in the magnitude of zeta potential, and shift of the Isoelectrical point (IEP) to lower pH values were observed. Such IEP shift is related to the copolymer adsorption on the Stern layer and to the position of the shear plane in the electrical double layer. In addition, the copolymer adsorption was found to reduce the CB parti- cle size achieving a minimum value in water of about 200 nm, resulting in sterically stable CB aqueous dispersions.

C60 fullerenes are spherical molecules composed purely of carbon atoms. They inspire a particularly strong scientific interest because of their specific physico-chemical properties and potential medical and nanotechnological applications. In this work we are focusing on studying the influence of the pristine C60 fullerene on biological activity of some aromatic drug molecules in human buccal epithelial cells. Assessment of the heterochromatin structure in the cell nucleus as well as the barrier function of the cell membrane was performed. The methods of cell microelectrophoresis and atomic force microscopy were also applied. A concentration-dependent restoration of the functional activity of the cellular nucleus after exposure to DNA-binding drugs (doxorubicin, proflavine and ethidium bromide) has been observed in human buccal epithelial cells upon addition of C60 fullerene at a concentration of ~10(-5 )M. The results were shown to follow the framework of interceptor/protector action theory, assuming that non-covalent complexation between C60 fullerene and the drugs (i.e., hetero-association) is the major process responsible for the observed biological effects. An independent confirmation of this hypothesis was obtained via investigation of the cellular response of buccal epithelium to the coadministration of the aromatic drugs and caffeine, and it is based on the well-established role of hetero-association in drug-caffeine systems. The results indicate that C60 fullerene may reverse the effects caused by the aromatic drugs, thereby pointing out the potential possibility of the use of aromatic drugs in combination with C60 fullerene for regulation of their medico-biological action.

The adhesion of acidophilic bacteria to mineral surfaces is an important phenomenon in bioleaching processes. In this study, functionalized colloidal probes covered by bioleaching bacterial cells (Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans) were developed and used to sense specific adhesion forces to a silica surface and a pyrite surface in various solutions. Experimentally, recorded retraction curves of A. thiooxidans revealed sawtooth features that were in good agreement with the wormlike chain model, while that of L. ferrooxidans exhibited stair-step separation. The magnitudes of adhesion forces and snap-off distances were strongly influenced by the ionic strength and pH. Macroscopic surface properties including hydrophobicity and surface potential for bacterial cells and substrata were measured by a sessile drop method and microelectrophoresis. The ATR-FTIR spectra indicated the presence of different types of biopolymers on two strains of bacteria.

Layer-by-layer (LbL) synthesis of titanium dioxide was performed by an oxidation-reduction route using a Ti(OH)3colloid and NaNO2solutions. A model of chemical reactions was proposed based on the results of an investigation of synthesized nanolayers by scanning electron microscopy, electron microprobe analysis and X-ray photoelectron spectroscopy, and studying colloidal solution of Ti(OH)3with laser Doppler microelectrophoresis. At each cycle, negatively charged colloidal particles of[Ti(OH)3]HSO4-adsorbed onto the surface of substrate. During the next stage of treatment in NaNO2solution, the particles were oxidized to Ti(OH)4. Photocatalytic activity was studied by following decomposition of methylene blue (MB) under UV irradiation. Sensitivity of the measurements was increased using a diffuse transmittance (DT) method. The investigation revealed strong photocatalytical properties of the synthesized layers, caused by their high area per unit volume and uniform globular structure.

Influence of sodium salts of selected chaotropic anions from the Hofmeister series (NaCl, NaBr, NaNO3, NaI) on the surface charge density of phosphatidylcholine membranes was studied. Small unilamellar lipid vesicles were used as a model system in the investigations. The theoretical and experimental approach to the interactions between inorganic anions and phosphatidylcholine membranes is presented. Experimental membrane surface charge densities data were determined as a function of pH of the aqueous electrolytes using microelectrophoresis method. The quantitative description of the interactions between zwitterionic phosphatidylcholine membrane and monovalent anions is presented. The equilibria constants of the binding of solution ions onto phospholipid surface were calculated. Knowledge of these parameters was essential to determine the theoretical membrane surface charge density values. The theoretical data were compared to the experimental ones in order to verify the mathematical model. Both approaches indicate that the anion-phosphatidylcholine membrane interaction increases with the size of the anion. The adsorption of chaotropic anions to membranes was found to follow the Hofmeister series I&minus, &gt, NO3&minus, Br&minus, Cl&minus

The electric properties of bacteria determine their non-specific interactions with the environment, in particular their pathogenic activity. The electric polarizability of Escherichia coli HB101 (K-12 strain) was studied while inactivation with ethanol (20–40 vol.%). The current investigation might be regarded as a continuation of previous research on the polarizability of E. coli at lower ethanol concentration (≤ 20 vol.%) and higher frequencies (≥ 20 kHz). The bacteria polarizability at low frequencies (4 Hz) shows anomalies (unexpected increase in the polarizability at certain ethanol concentrations), while the parameter decreases with an increase in the ethanol concentration at higher frequencies. We investigated for the possible reasons causing the anomalies — in our case reduced to the medium dielectric permittivity, the average cell length and the surface electric charge density distribution, related to bacterial lipopolysaccharides. We suggest a hypothesis for the molecular mechanism of changing the surface charge of E. coli, carried by lipopolysaccharides, induced by the non-ionic ethanol.

Following systemic administration, liposomes are covered by a 'corona' of proteins, and preserving the surface functionality is challenging. Coating the liposome surface with polyethylene glycol (PEG) is the most widely used anti-opsonization strategy, but it cannot fully preclude protein adsorption. To date, protein binding has been studied following in vitro incubation to predict the fate of liposomes in vivo, while dynamic incubation mimicking in vivo conditions remains largely unexplored. The main aim of this investigation was to determine whether shear stress, produced by physiologically relevant dynamic flow, could influence the liposome-protein corona. The corona of circulating PEGylated liposome was thoroughly compared with that formed by incubation in vitro. Systematic comparison in terms of size, surface charge and quantitative composition was made by dynamic light scattering, microelectrophoresis and nano-liquid chromatography tandem mass spectrometry (nanoLC-MS/MS). Size of coronas formed under static vs. dynamic incubation did not appreciably differ from each other. On the other side, the corona of circulating liposomes was more negatively charged than its static counterpart. Of note, the variety of protein species in the corona formed in a dynamic flow was significantly wider. Collectively, these results demonstrated that the corona of circulating PEGylated liposomes can be considerably different from that formed in a static fluid. This seems to be a key factor to predict the biological activity of a liposomal formulation in a physiological environment.

Oligomerization of linearized plasmids by nuclear proteins extracts, a recognized measure of nonhomologous end-joining (NHEJ) repair capacity, is typically assessed through agarose gel electrophoresis, a labor-intensive procedure. In the current study, a more convenient NHEJ assay was developed using microchips that allow scaled-down separation and quantification. This microchip method allows a considerable reduction in sample amount and analysis time with similar costs and comparable or slightly better precision. Data obtained with quercetin and wortmannin show that the method can be applied to the screening of food components and natural products for positive and negative modulators of NHEJ, potential chemopreventive and indirect genotoxic compounds, respectively.

The viability of the probiotic strain Lactobacillus plantarum subsp. plantarum, after its passage through simulated gastric and pancreatic juices, was evaluated as function of its pre-growth in a medium containing the known prebiotics pectin or inulin, and was compared to glucose used as control. The presence of pectin or inulin did not markedly affect the growth (10.07 log10 colony forming units/mL and 10.28 log10 colony forming units/mL for pectin and inulin respectively versus 10.42 log10 colony forming units/mL obtained for glucose). Pectin and inulin, in contrast to glucose, induced cell stress resistance against gastrointestinal juices (D log101.5 and 2.4 colony forming units/mL respectively, versus D log10 4.0 for glucose). The data were corroborated by the analysis of the protein pattern following stress treatments which, in the case of microbial cells grown with glucose, revealed a more marked protein degradation after the double passage through simulated gastric and intestinal juices. Inulin stimulated the production of the relevant healthy bio-molecule butyrate, which amount was 30% higher respect of growth in the presence of glucose. Inulin and pectin improved cell DPPH scavenging activity, and an impressive hydrophobicity (35.28% and 34.81%, respectively) was observed with respect to the microbial growth in presence of glucose (3.39%).

Natural rubber (NR) from the Hevea brasiliensis tree is the main commercial feedstock for rubber and latex dipping industries. NR latex particles in a matured commercial latex concentrate are stabilized by charged groups derived from proteins, long-chain fatty acid soaps and polypeptides adsorbed on the particle surface. The colloidal stability of the latex is extremely sensitive to pH as well as to the ionic environment of the dispersing medium. Previous work on particle microelectrophoresis has shown that the charge on the particle surface is derived mainly from carboxylic groups of long chain fatty acids (ca. 86%). Freshly collected field latex from the tree, on the other hand, is believed to be stabilized by proteins and phospholipids before hydrolysis sets in upon leaving the tree. The exact arrangement of the adsorbed proteins and phospholipids and the thickness of this adsorbed layer have yet to be successfully determined. The present study has been focused on unraveling the arrangement of these proteins and phospholipids on the particle surface of a freshly tapped NR latex. In order to visualize these molecules, they were imaged using phase contrast atomic force microscopy (AFM). Moreover, the molecules in the particle were labeled with fluorescent Rhodamine B (RB) and uncharged fluorescein-5(6)-isothiocyanate (FITC), and monitored by confocal laser scanning microscopy (CLSM) thereby permitting an in situ observation of their locations on and inside the particles. The selective labeling of the proteins and phospholipids with RB and FITC in protein-free as well as in protein-and-lipid-free latex particles permitted an unequivocal determination of their presence both on the surface and in the interior of the particles. An indentation study of the surface layer of the original untreated NR particle was also carried out to confirm the hypothesis of a core–shell structure with a mixed layer of proteins and phospholipids surrounding the hydrophobic core of polyisoprene particles. According to the obtained results, the surface of the particles in freshly tapped latex is distinctly different from that of a matured latex concentrate.

Microelectrophoresis, dynamic light scattering, fluorescence, and microcalorimetry are used to study the adsorption of a synthetic polycation, poly-N-ethyl-4-vinylpyridinium bromide, on the surface of three-component liposomes formed from electrically neutral phosphatidylcholine, anionic diphosphatidylglycerol (cardiolipin), and cationic dicetyldimethylammonium bromide, with the two latter being taken in equal amounts. The adsorption of the polycation on the liposomal membrane results in the generation of a positive charge, which provides the polycation-liposome complex with aggregation stability. Increasing salt concentration in the suspension causes the complex to dissociate into its components. According to the microcalorimetry data, the membranes of the initial three-component liposomes consist of two microphases, with one of them being enriched with the neutral lipid and another one, with the ionic components. The polycation adsorption does not lead to noticeable structural rearrangements in the liposomal membranes.

In the present work, polylactic acid, PLA, samples were degraded by hydrothermal treatment, and then their molecular weights, crystallinity, surface charges and compositions, were determined, respectively, by using viscometry, 1H NMR, Differential Scanning Calorimetry (DSC), microelectrophoresis and Infra Red spectroscopy methods. The viscometry and 1H NMR data indicate that the molecular weight, of the polymer, decreases after the hydrothermal treatment. However, the crystalline fractions of the PLA samples, as obtained from the DSC and X-ray data, were not altered after the hydrothermal treatment. Furthermore, the zeta potential data, as determined by microelectrophoresis, show for both non-degraded and degraded PLA, an increase of the polymer surface charge density with the pH of the aqueous phase. However, at acidic pH values, the surface charge density for the degraded PLA was higher as compared to the non degraded one. These differences in surface charge densities of the PLA samples were confirmed by Infrared study, according to which the spectra of degraded polymer show the appearance of carboxyl groups occurring at 1,600 cm−1 at the polymer surface.

In this study, the influence of pH, electrolyte concentration, and type of ionic species on the electrokinetic properties (zeta potential and electrokinetic charge density) of the acid-activated montmorillonite mineral have been investigated using the microelectrophoresis method. The electrokinetic properties of acid-activated montmorillonite dispersions have been determined in aqueous solutions of mono-, di-, and trivalent salts and divalent heavy metal salts. Zeta potential experiments have been performed to determine the point of zero charge (pzc) and potential determining ions (pdi). The zeta potential values of the acid-activated montmorillonite particles were negative and did not vary significantly within the pH range studied. Acid-activated montmorillonite dispersions do not have point of zero charge (pzc). The valence of the electrolytes has a great influence on the electrokinetic behavior of the suspension. A gradual decrease in the zeta potential (from −25 mV to −5 mV) occurs with the monovalent...

Nanocapsules containing hinokitiol (HKL) were prepared by an emulsion-diffusion method. Poly(ɛ-caprolactone) (PCL), synthesized according to a ring opening method, was used as a wall material, and HKL dissolved in octyl salicylate (OS) was use as a core material. In an emulsification step in preparing nanocapsules, three kinds of emulsifiers were employed, namely cetyltrimethylammonium chloride (CTAC), sodium lauryl sulfate (SLS), gelatin. On a transmission electron microscope, the size was hundreds of nanometers. According to the results of pH-dependent microelectrophoresis, the absolute value of the surface potential of the nanocapsules prepared using either CTAC or SLS was greater than 20 mV. In case the nanocapsules were prepared using the mixture of CTAC and gelatin, the value was between 0 mV and 20 mV. The nanocapsules prepared by using either CTAC or SLS were stable in terms of size over the pH range of 3–11. However, the nanocapsules prepared using the mixture of CTAC and gelatin was not stable in size over the same pH range. Following the results of in vitro permeation experiment, the nanocapsules enhanced the permeation of HKL. Especially, the nanocapsules prepared using SLS was prominent in promoting the permeation. This is probably because that SLS act as a permeation enhancer. However, the nanocapsules themselves hardly penetrated into hairless mouse skin, which was observed on a confocal laser scanning microscope.

The method of microelectrophoresis is employed to study the dependence of the ζ-potential of microcrystalline cellulose particles on the concentration (10−6–10−3 M) and pH (2–11) of aqueous aluminum chloride, nitrate, and sulfate solutions. It is shown that, in the absence of aluminum salts, the isoelectric point (IEP) of the particles is independent on the nature of acid anions and is observed at pH 3.2. The addition of aluminum salts in concentrations as low as 2 × 10 −6 M for chloride and nitrate and 1 × 10−5 M for sulfate causes a shift of IEP to a less acidic region (pH 3.8), the value of which is virtually independent of the nature of the salt. As the concentration of salts is increased, the ζ-potential becomes positive, rises with an increase in pH to a maximum magnitude at pH 5.0–6.0, and decreases further until the second IEP (pH ∼ 6.5–7.0) is reached. At higher pH values, the ζ-potential becomes negative again. The observed ζ(pH) dependences are explained by the formation of hydrolyzed aluminum species exhibiting different adsorbabilities on microcrystalline cellulose particles. It is shown that positively charged hydroxocomplexes formed in aluminum sulfate solutions are characterized by a lower adsorbability than hydroxocomplexes formed in chloride and nitrate solutions.

We have developed a new method for evaluating the affinity interactions between two different proteins by applying an alternating current (AC) voltage to a micro-flow channel. An AC voltage was applied to the protein-modified microspheres in the micro-flow channel, which resulted in the oscillation of the microspheres owing to their surface charges. The oscillation amplitude showed a linear relationship with the charge density of the microspheres. As an example for protein affinity measurement, the amplitude changes of a profilin-modified microsphere were measured by the addition of actin. In the same electrical condition, the oscillation amplitude of the profilin-modified microsphere increased by ≈175% by binding with actin. Similar results in the principle were obtained for the affinity interaction between biotin and streptavidin. The results showed that the higher the charge density of the microspheres induced by binding with different proteins, the higher the oscillation amplitude of the microspheres, thus, suggesting a possible application of the micro-flow channel and AC voltage on the protein property study, as well as on the biosensor application using the oscillation amplitude changes.

The pH dependences of electrokinetic potentials (EKP) of the cells of two Escherichia coli K-12 strains (D21 and JM 103) with known lipopolysaccharide (LPS) core composition have been determined by the method of microelectrophoresis. At pH 4.6–5.2, the negative surface charge of the cells with Re core LPS was reliably higher. It was shown that the interaction of bacteria with lysozyme results in a decrease of optical density of suspensions due to higher sensitivity of the cells with complete LPS core to hypotonic shock. LPS release from bacterial cell wall depended also on bacterial LPS core composition and increased with LPS core extension. Electrokinetic measurements and the study of the interaction of cells with lysozyme suggest that higher negative surface charge of E. coli JM 103 cells (Re type LPS) is associated with higher quantity and density of LPS packing in the cell wall as compared with the cells of E. coli D21 (Ra type LPS).

A new kind of magnetic luminescent nanocomposite (MLNC) particles was prepared by a combination process of sol–gel and electrostatic self-assembly techniques. In this process, superparamagnetic Fe 3 O 4 nanoparticles were coated with silica, forming SiO 2 /Fe 3 O 4 core-shell structure particles. A surface-active agent, 3-aminopropyltrimethoxysilane was then used to terminate the silica surface of these particles with amino groups. Finally, thioglycolic acid (TGA)-capped CdSe Quantum Dots (QDs) were attached onto the surface of SiO 2 /Fe 3 O 4 particles by electrostatic self-assembly. X-ray diffraction (XRD), transmission electron microscopy (TEM), microelectrophoresis, UV–vis absorption and emission spectroscopy and magnetometry were applied to characterize the nanocomposite particles. The particles exhibited favorable superparamagnetic and photoluminescenct (PL) properties. With increasing the thickness of silica shell, more dense CdSe QDs were attached on the SiO 2 /Fe 3 O 4 nanoparticles and the PL intensity increased.

In the present work, genome instability in human and bovine peripheral blood lymphocytes and spermatozoa was studied by the method of DNA microelectrophoresis with subsequent staining of single cells with silver nitrate. A comparative analysis of the types of damage to human and bovine lymphocytes and spermatozoa genomes was performed. In the group of healthy donors, the spontaneous frequency of DNA damage revealed by single cell DNA microelectrophoresis did not exceed 9% and amounted, on average, to 4.8 ± 1.2%. In studying the effect of the duration of cryoconservation on bovine spermatozoa, no significant changes were revealed between the group of bulls whose spermatozoa were stored for less than one year (3.1 ± 0.9%) and the group of animals whose spermatozoa were under conditions of cryoconservation for more than 20 years (4.3 ± 0.5%). From the obtained single-cell DNA microelectropheretic data on the types and frequencies of DNA damage, a conclusion was made regarding the possibility of using a light variant based on cell staining with silver nitrate for the detection of genome instability, not only in somatic, but also in reproductive, cells.

Nanocapsules containing hinokitiol (HKL) were prepared by an emulsion-diffusion method. In an emulsification step in preparing nanocapsules, cetyltrimethylamonium chloride (CTAC) was employed as a cationic emulsifier, Poly(epsilon-caprolactone) (PCL) was use as a wall material and HKL dissolved in octylsalicylate (OS) was used as a core material. The submicron-sized nanoparticle was observed on a TEM. The size ranged 55-234 nm and the mean diameters were 223 nm, which were determined by a dynamic light scattering method. According to the results of pH-dependent microelectrophoresis, the absolute value of the surface potential of the nanocapsules was greater than 20 mV. The nanocapsules were colloidally stable over the pH range of 3-11. The nanocapsules were included in two kinds of preparations, namely shampoo and hair tonic, and the preparations were applied every day for 3 weeks on the clipped backs of 6 week-old mouse (C57BL/6) to investigate the hair growth-promoting effect. The degree of hair growth was evaluated by image-analysing the photographs of the backs and, in parallel, by the histological observation of the formation and the growth of hair or hair bulbs. The results were compared with those of commercially available Minoxidil solution (3%). Phosphate buffered saline was used as a control. The in vivo hair growth-promoting effects of the two preparations were comparable to those of Minoxidil solution. These results are in a good agreement with the histological and structural changes of follicles of the model animals, of which skins were treated with either the testing samples or the control in the same way the experiments of in vivo hair growth promotion were performed.

Aims: Microelectrophoresis allows the detection of DNA bands using minimal amounts of sample in a short time, but commonly requires the use of special equipment which is not available in all laboratories. This fact has limited the application of this technique in microbiology despite its advantages. In this work, we describe a new approach to perform gel microelectrophoresis, named high-speed gel microelectrophoresis (HSGME), and its application for rapid detection of bacteria, protozoa and viruses in clinical, vegetal and environmental samples. Methods and Results: Aliquots of 0·4–1 μl of PCR product were loaded in 2 cm 1% agarose microgels and electrophoresed at high voltage (125 V cm−1) in conventional submarine horizontal mini-slabs. By using HSGME, single-DNA bands obtained after specific-PCR useful in diagnosis of different diseases caused by micro-organisms were detected in 5 min. Conclusions: HSGME is a rapid and easy procedure applicable to detection of microbial genes, which is carried out using conventional equipment and thus can be performed in any research and diagnostic laboratory. Significance and Impact of the Study: The performance of HSGME saves up to 90% time, material and energy costs, as well as laboratory hazardous wastes including carcinogenic agents used for visualizing DNA bands.

Four monodisperse polystyrene latices, containing particles of diameter ca. 2400 A, were prepared using hydrogen peroxide and potassium persulfate as initiators and sodium dodecanoate, sodium mono-dodecyl phosphate, and dodecylamine hydrochloride as emulsifiers. These latices were characterized by electron microscopy, gas adsorption, and microelectrophoresis. The results obtained by the first two techniques indicated that the particles were essentially nonporous rigid spheres. Electrokinetic procedures were used to characterize the ionogenic groups on the latex particles. In addition to the emulsifier molecules, other groups, namely carboxylic acid groups, were found to be present on all of the latices, irrespective of the nature of the initiator or umulsifier used to produce them, Electrophoresis also revealed that the emulsifiers could be removed from the latex dispersions by dialysis, leaving systems with these carboxyl groups as an integral part of the particle surfaces. By electrokinetics, the surface pK value of these unknown acid groups was 4.64. It was also established by radiochemical methods, combined with microelectrophoresis, that sodium dodecanoate was removable by dialysis from polystyrene latices. Before dialysis the concentration of the free emulsifier was below the critical micelle concentration. The latter experiments also suggested that the construction of adsorption isotherms from electrokinetic data is of doubtful validity. The integral carboxyl groups were probably produced by polymer oxidation during polymerization.

The objectives of this study were to prepare films from submicron chitosan/Eudragit® L100-55 polyelectrolyte complexes (CH/EL PEC) and to assess the influence of CH molecular weight and CH/EL mass ratio on their structure and drug-release properties. The films were obtained by a simple, environmentally friendly, casting/solvent evaporation method and the verapamil hydrochloride (VH) was used as model drug. Submicron size, narrow size distribution, and acceptable stability of CH/EL PECs were confirmed by DLS and laser Doppler microelectrophoresis. SEM analysis revealed nonporous inner structure and flat surface of the films. Interactions between comprising polymers and formation of CH/EL PEC were established by DSC and FT-IR spectroscopy. In vitro swelling and drug release studies revealed the pH sensitivity of the films, with burst drug release in acidic conditions (pH 1.2) and sustained release in phosphate buffers pH 5.8, 6.8, and 7.4. The slowest VH release was achieved from the films prepared from equal amounts of EL and CH of higher molecular weight, confirming the significance of the CH/EL ratio and CH molecular weight on their ability to sustain drug release. The obtained results suggested that presented, simple, and eco-friendly preparation procedure can be used to obtain pH-sensitive CH/EL PEC films with a promising potential as drug carriers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42583.

Stabilized PEI/DNA polyplexes were generated by cross-linking PEI with biodegradable disulfide bonds. The reaction conversion of different PEIs with the amine reactive cross-linker dithiobis(succinimidyl propionate) (DSP) was investigated, and the molecular weight of the reaction products was identified. Light scattering and microelectrophoresis were employed to assess size and zeta potential of the resulting polyplexes. Polyplex morphology and mechanic stability were investigated using atomic force microscopy. Finally, albumin and erythrocyte interactions and stability against polyanions and high ionic strength were checked. Polyplexes of PEI and DNA were prepared by two different formulation methods, either using pre-cross-linked polymers or by cross-linking polyplexes after complexation. Only the latter method yielded small (100-300 nm) polyplexes with a positive zeta potential when HMW PEI was used, whereas cross-linked LMW PEI resulted in polyplexes with increased size (>1000 nm) and zeta potentials down to -20 mV. In addition, only cross-linking after polyplex formation was able to enhance resistance against polyanion exchange and high ionic strength. AFM images revealed no changes in the morphology of cross-linked HWM PEI polyplexes, and indentation force measurements using AFM significantly increased mechanical stability of cross-linked HMW PEI polyplexes. These polyplexes also displayed significantly reduced interactions with major blood components like albumin and erythrocytes. The resulting biocompatible particles offer a means of combining enhanced polyplex stability with redox-triggered activation for in vivo application.