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The model of counterion-induced metallacarborane aggregation in water was verified on sodium bis(1,2-dicarbollide), one of the most studied examples of metallacarboranes. This case study introduces a novel approach in anionic boron cluster self-assembly that resembles the behavior of polyoxometalate nanoions. The key prerequisite of the counterion binding to the aggregates is the strongly uneven charge distribution of cobalt bis(dicarbollide) clusters. Simultaneously, the size of the counterion should fit into the void between the metallacarborane clusters within the aggregate. In consequence, compact pentamers with two bound sodium cations via Coulombic-driven assembly are formed. This behavior cannot be explained solely by the hydrophobic effect─the paradigm of metallacarborane aggregation in the current literature. The pentamers can merge into bigger nanostructures via the second aggregation mechanism that sheds light on the complex behavior of metallacarboranes in water. The proof-of-concept of counterion-induced metallacarborane aggregation and the proposed total description of the self-assembly via the two-process model are results of calorimetry modeling, quantum chemistry calculations, and molecular dynamics simulations.

Small cellular particles (SCPs) are being considered for their role in cell-to-cell communication. We harvested and characterized SCPs from spruce needle homogenate. SCPs were isolated by differential ultracentrifugation. They were imaged by scanning electron microscope (SEM) and cryogenic transmission electron microscope (cryo TEM), assessed for their number density and hydrodynamic diameter by interferometric light microscopy (ILM) and flow cytometry (FCM), total phenolic content (TPC) by UV-vis spectroscopy, and terpene content by gas chromatography-mass spectrometry (GC-MS). The supernatant after ultracentrifugation at 50,000× g contained bilayer-enclosed vesicles whereas in the isolate we observed small particles of other types and only a few vesicles. The number density of cell-sized particles (CSPs) (larger than 2 μm) and meso-sized particles (MSPs) (cca 400 nm–2 µm) was about four orders of magnitude lower than the number density of SCPs (sized below 500 nm). The average hydrodynamic diameter of SCPs measured in 10,029 SCPs was 161 ± 133 nm. TCP decreased considerably due to 5-day aging. Volatile terpenoid content was found in the pellet after 300× g. The above results indicate that spruce needle homogenate is a source of vesicles to be explored for potential delivery use.

The preparation of autologous platelet and extracellular vesicle-rich plasma (PVRP) has been explored in many medical fields with the aim to benefit from its healing potential. In parallel, efforts are being invested to understand the function and dynamics of PVRP that is complex in its composition and interactions. Some clinical evidence reveals beneficial effects of PVRP, while some report that there were no effects. To optimize the preparation methods, functions and mechanisms of PVRP, its constituents should be better understood. With the intention to promote further studies of autologous therapeutic PVRP, we performed a review on some topics regarding PVRP composition, harvesting, assessment and preservation, and also on clinical experience following PVRP application in humans and animals. Besides the acknowledged actions of platelets, leukocytes and different molecules, we focus on extracellular vesicles that were found abundant in PVRP.

Small particles in natural sources are a subject of interest for their potential role in intercellular, inter-organism, and inter-species interactions, but their harvesting and assessment present a challenge due to their small size and transient identity. We applied a recently developed interferometric light microscopy (ILM) to assess the number density and hydrodynamic radius (Rh) of isolated small cellular particles (SCPs) from blood preparations (plasma and washed erythrocytes) (B), spruce needle homogenate (S), suspension of flagellae of microalgae Tetraselmis chuii (T), conditioned culture media of microalgae Phaeodactylum tricornutum (P), and liposomes (L). The aliquots were also assessed by flow cytometry (FCM), dynamic light scattering (DLS), ultraviolet-visible spectrometry (UV-vis), and imaging by cryogenic transmission electron microscopy (cryo-TEM). In Rh, ILM showed agreement with DLS within the measurement error in 10 out of 13 samples and was the only method used here that yielded particle density. Cryo-TEM revealed that representative SCPs from Tetraselmis chuii flagella (T) did not have a globular shape, so the interpretation by Rh of the batch methods was biased. Cryo-TEM showed the presence of thin filaments in isolates from Phaeodactylum tricornutum conditioned culture media (P), which provides an explanation for the considerably larger Rh obtained by batch methods than the sizes of particles observed by cryo-TEM images. ILM proved convenient for assessment of number density and Rh of SCPs in blood preparations (e.g., plasma); therefore, its use in population and clinical studies is indicated.

In parallel to medical treatment of ovarian cancer, methods for the early detection of cancer tumors are being sought. In this contribution, the use of non-invasive static (SLS) and dynamic light scattering (DLS) for the characterization of extracellular nanoparticles (ENPs) in body fluids of advanced serous ovarian cancer (OC) and benign gynecological pathology (BP) patients is demonstrated and critically evaluated. Samples of plasma and ascites (OC patients) or plasma, peritoneal fluid, and peritoneal washing (BP patients) were analyzed. The hydrodynamic radius (Rh) and the radius of gyration (Rg) of ENPs were calculated from the angular dependency of LS intensity for two ENP subpopulations. Rh and Rg of the predominant ENP population of OC patients were in the range 20–30 nm (diameter 40–60 nm). In thawed samples, larger particles (Rh mostly above 100 nm) were detected as well. The shape parameter ρ of both particle populations was around 1, which is typical for spherical particles with mass concentrated on the rim, as in vesicles. The Rh and Rg of ENPs in BP patients were larger than in OC patients, with ρ ≈ 1.1–2, implying a more elongated/distorted shape. These results show that SLS and DLS are promising methods for the analysis of morphological features of ENPs and have the potential to discriminate between OC and BP patients. However, further development of the methodology is required.

The temperature-induced formation of nanoparticles of two poly(methacrylic acid) (PMA) isomers, atactic (aPMA) and isotactic (iPMA), displays an opposite thermoresponsiveness. The formation of nanoparticles is investigated in dilute aqueous solutions in the presence of cations of different charge (Na+, Mg2+, and La3+) first by UV spectroscopy and visual observations. In the aPMA case, aggregation and phase separation take place with increasing temperature, whereas with iPMA intermolecular associates gradually disintegrate upon heating the solutions; however, no macroscopic phase separation is observed, and the process is completely reversible. Stable associates exist in iPMA solutions at all temperatures if higher valency ions (Mg2+ and La3+) are present, whereas with aPMA, only La3+ ions induce irreversible (stable) aggregation. Detailed structural characteristics of iPMA and aPMA aggregates are determined by dynamic and static light scattering and additionally characterized by pyrene fluorescence measur...

Background: Cells in general secrete nanoparticles (NPs) which are believed to mediate intercellular communication. Recently, great efforts have been made to utilize them as delivery vectors. We aimed to harvest and identify NPs from liquid cultures of two marine microalgae Dunaliella tertiolecta and Phaeodactyum tricornutum. Methods: NPs were isolated from the culture conditioned media by differential ultracentrifugation by the protocol used for the isolation of extracellular vesicles. Microalgae and isolated NPs were examined by scanning electron microscopy (SEM) while isolated NPs were examined also by cryogenic transmission electron microscopy (cryo-TEM). The Triton X-100 detergent and temperature sensitivity of NPs was assessed by dynamic light scattering (DLS) through monitoring the intensity of the scattered light (I) and the distribution of hydrodynamic radii of NPs (Rh). Results: Two mechanisms of formation of NPs with average Rh 200 nm were observed in the D. tertiolecta culture: a disintegration of tubular protrusions, and cell decay. A part of the imaged D. tertiolecta NPs were membrane-enclosed vesicles, but the isolates also contained electron-dense NPs and nanofilaments. P. tricornutum NPs in the culture and in the isolate were homogeneous in size and shape. Their average Rh was 104 nm. The addition of surfactant to isolates resulted in a change in Rh distribution and a decrease of I in samples from both species, indicating decay of a part of NPs. Changes in the width of the I(Rh) peaks were observed at temperatures above 45 °C. Conclusions: A part of NPs found in isolates from microalgae D. tertiolecta and P. tricornutum were membrane-enclosed vesicles. However, the isolates obtained by a standard protocol for extracellular vesicle isolation by ultracentrifugation contained also a significant amount of other similar-sized nanoparticles. The isolates were partly susceptible to the addition of detergent and to temperature up to 80 degrees.

To increase the stability of bioactive compounds and to protect them from adverse environmental conditions, they can be encapsulated in lipids and/or polymeric matrices. Here, pantothenic acid was encapsulated in liposomes and in different hydrogel microcapsules that consisted of alginate or alginate–pectin mixtures. With liposomes, an encapsulation efficiency of 0.75 ± 0.02 was achieved, and for alginate microparticles, 0.60 ± 0.02. The release of pantothenic acid from liposomes and from the different alginate–pectin microparticles loaded with liposomes followed first-order kinetics. For alginate microparticles and alginate microparticles loaded with liposomes, pantothenic acid release followed Higuchi kinetics, which suggests that this pantothenic acid release was mainly driven by a diffusion-controlled mechanism. To the best of our knowledge, this is the first report of the encapsulation of pantothenic acid.

Extracellular vesicles (EVs) are gaining increasing amounts of attention due to their potential use in diagnostics and therapy, but the poor reproducibility of the studies that have been conducted on these structures hinders their breakthrough into routine practice. We believe that a better understanding of EVs stability and methods to control their integrity are the key to resolving this issue. In this work, erythrocyte EVs (hbEVs) were isolated by centrifugation from suspensions of human erythrocytes that had been aged in vitro. The isolate was characterised by scanning (SEM) and cryo-transmission electron microscopy (cryo-TEM), flow cytometry (FCM), dynamic/static light scattering (LS), protein electrophoresis, and UV-V spectrometry. The hbEVs were exposed to various conditions (pH (4–10), osmolarity (50–1000 mOsm/L), temperature (15–60 °C), and surfactant Triton X-100 (10–500 μM)). Their stability was evaluated by LS by considering the hydrodynamic radius (Rh), intensity of scattered light (I), and the shape parameter (ρ). The morphology of the hbEVs that had been stored in phosphate-buffered saline with citrate (PBS–citrate) at 4 °C remained consistent for more than 6 months. A change in the media properties (50–1000 mOsm/L, pH 4–10) had no significant effect on the Rh (=100–130 nm). At pH values below 6 and above 8, at temperatures above 45 °C, and in the presence of Triton X-100, hbEVs degradation was indicated by a decrease in I of more than 20%. Due to the simple preparation, homogeneous morphology, and stability of hbEVs under a wide range of conditions, they are considered to be a suitable option for EV reference material.

Interactions between ionic organic systems, such as surfactants or polyelectrolytes, and divalent or higher valent metal ions have been studied extensively for many years, but still present challenges in understanding the type and nature of interactions involved and also the driving forces behind metal ion binding.

Although the role of extracellular vesicles in inter-cell communication is acknowledged, their analytics is yet problematic. Poor understanding of effects of sample processing may be one of the cornerstones of this issue. We investigated the effects of centrifugation during the vesicle isolation on the number, size, content and shape of particles in the isolates. Particles in the range of about 100–500 nm as observed by the scanning electron microscope exhibited characteristic shapes of vesicles without internal structure. Enhanced centrifugal pull resulted in increased amount of certain types of proteins in the isolates. Majority of present proteins were highly abundant human plasma proteins, including albumins and immunoglobulins. Results are in favor of the hypothesis that the isolated particles reflect the substance from which they originate (cells and the surrounding solution) and the performed processing; and therefore, vesicles in isolates should be viewed upon as a dynamic material with transient identity.

Dynamic and static light scattering measurements were performed on isotactic and atactic forms of poly (methacrylic acid), iPMA and aPMA, respectively, in order to perform a wide survey of their molecular properties and chain dynamics in water as functions of tacticity, degree of neutralization, alpha(N), and salt concentration, c(s). The molecular parameters of PMA chains were analyzed at low alpha(N) and chain dynamics (diffusion coefficients and in this connection the polyelectrolyte slow mode behavior) at higher alpha(N). The data revealed that both PMAs form microgel-like aggregates with a core-shell structure at low alpha(N) ( = 0 and 0.25 for aPMA and iPMA, respectively). The distribution of the hydrophilic and hydrophobic functional groups within the aggregates and their compactness depended considerably on chain tacticity and for aPMA also on c(s). Further, the effect of c(s) on the polyelectrolyte slow diffusion coefficient, D-s, of partly (0.25

The formation of nanoparticles of two poly(methacrylic acid) (PMA) isomers, atactic (aPMA) and isotactic (iPMA), was investigated in aqueous solutions in the presence of mono- (Na+) and multivalent cations (Mg2+ and La3+). Using dynamic (DLS) and static light scattering (SLS), we show that PMA nanoparticles have characteristics of microgel-like particles with a denser core and a swollen corona. iPMA aggregates are stable at a much higher degree of neutralization (&alpha, N) than the aPMA ones, indicating a much stronger association between iPMA chains. This is explained by proposing segregation of ionized and unionized carboxyl groups within the iPMA aggregates and subsequent cooperative hydrogen-bonding between COOH groups. The calculated shape parameter (&rho, ) suggests different behavior of both isomers in the presence of Mg2+ ions on one hand and Na+ and La3+ on the other. The microgel-like particles formed in the presence of Mg2+ ions have a more even mass distribution (possibly a no core-shell structure) in comparison with those in the presence of Na+ and La3+ ions. Differences between the aggregate structures in the presence of different ions are reflected also in calorimetric experiments and supported by pH and fluorimetric measurements. Reasons for different behavior in the presence of Mg2+ ions lie in specific properties of this cation, in particular in its strong hydration and preference towards monodentate binding to carboxylate groups.

Stoichiometric polyelectrolyte-surfactant complexes, PSCs, were prepared from poly(acrylate), PA - , and poly(styrenesulfonate), PSS - , anions and dodecyltrimethylammonium cations, DTA + , and their properties were investigated by density and viscosity measurements in ethanol solutions in dependence on concentration and temperature. The measured densities were used to calculate the apparent molar volumes of the repeat units of DTAPA and DTAPSS complexes. Apparent molar volumes at infinite dilution, so as the reduced viscosities, in ethanol solutions are only weakly dependent on temperature. Through features typical for polyelectrolytes, viscosity curves suggest some small dissociation of complexes in ethanol. Light scattering, LS, measurements performed in the angular range from 50 to 150° did not reveal so called slow relaxation mode, which is typical for strongly charged polyelectrolytes in aqueous solutions without or with only a low amount of added salt. Size distributions were therefore calculated from the measured correlation functions. They were multimodal at all angles and for both PSCs, identifying 3 populations: particles with average hydrodynamic radii (i) below 10 nm, (ii) in the range 20–30 nm, and (iii) in the range 200–300 nm. Analysis of angular dependency of LS intensity for the largest particle population enabled the determination of the radius of gyration and the shape parameter ρ of these species. Large sizes, ρ values (ρ = 1.6 and 1.9 for DTAPA and DTAPSS, respectively), and the Kratky plots of the scattering data suggest that these particles are associates of more than one PSC (reverse micelle). Dynamic vapor sorption experiments with thin films of the studied PSCs show that the DTAPSS complex absorbs at the most 35% of water per its weight, whereas the DTAPA one absorbs considerably more (around 75%). Different structure of complexes was taken as responsible for large differences in water uptake.

Understanding the adsorption of amino acids (AAs) onto magnetic iron-oxide nanoparticles (SPIONs) is important not only for the preparation of the aqueous suspensions, but also for understanding the interactions at the bionano interface. In this investigation the adsorption of aspartic acid (Asp) and lysine (Lys) onto SPIONs was studied, based on a characterization of the suspension properties, i.e., measurements of the ξ-potential, the hydrodynamic size, and the osmolality, and by direct HPLC analysis of the AA in the supernatants and at the nanoparticles of the ultracentrifuged suspensions. The results show that the AAs adsorb onto the SPIONs in the form of large molecular associates, which decisively influence the nanoparticles’ surface properties. A measurement of the freezing-point depression using a Knauer osmometer proved that the molecular associates are already formed in the AA aqueous solutions.

In arthropods, the determination of two important parameters of digestive juices, i.e. the total surfactant concentration and the critical micelle concentration (CMC), is challenging due to small sample volumes and low surfactant concentrations. In this work, we report a successful implementation of potentiometric titrations using the surfactant ion-selective electrode (SISE) and the pyrene fluorescence method (PFM) for the determination of the total surfactant concentration and CMC in the digestive juice of terrestrial isopod crustaceans Porcellio scaber. Pooled digestive juice extracts of four (SISE) or two (PFM) animals were used per measurement run. In both cases, digestive juice extracts in 100 μL of deionized water were sufficient for one measurement run. The total surfactant concentration of P. scaber digestive juice was determined to be 9.2 ± 3.5mM and the CMC was approximately 90 μM. Our work presents an important improvement towards easy CMC determination in small volume samples in comparison with the commonly used stalagmometric technique, where much larger sample volumes are usually needed. To date, the total surfactant concentration was not measured in the digestive juices of arthropods other than Homarus vulgaris, Astacus leptodactylus and Cancer pagurus, for which complex separation and analytical techniques were required. Our results obtained by SISE and PFM therefore present the first successful quantification of surfactants and their CMC in small volumes of arthropod digestive juice without prior separation or purification techniques.

Mixtures of an anionic polyelectrolyte, poly(sodium methacrylate), NaPMA, and a neutral polymer, polyethylene glycol, PEG, were investigated by dynamic and static light scattering techniques at different concentrations and chain-lengths of PEG. The NaPMA standard with a narrow molecular weight distribution was chosen for the study. The so called slow-mode behaviour, characteristic of salt-free NaPMA solutions, vanishes as the simple salt, NaCl in this case, is added in a sufficient amount. However, in NaPMA–NaCl–PEG mixtures, the slow-mode signal is observed again. We assume that the dielectric constant of the mixture with PEG, which is substantially lower than that of pure water, causes the reappearance of the slow-mode signal through reinforced electrostatic interactions between NaPMA polyions. Monte Carlo simulations of a coarse-grained model of the system confirm stronger correlations between NaPMA molecules and thus qualitatively agree with experimental results.

Polyelectrolyte–surfactant complexes, PSCs, are widely used and studied. In this data article, we report an easy preparation procedure of the complex salt formed between cetylpyridinium cations and poly(styrenesulfonate) anion complemented by values of its molar extinction coefficient and specific refractive index increment in aqueous solutions at various charge ratios between the surfactant (S) and the polyion (P) charges (S/P). These complexes have superior solubility in water. The molar extinction coefficient increases linearly with S/P, whereas the specific refractive index increment does not depend on S/P. These data are useful for the spectrophotometric determination of concentration and for molar mass determination by light scattering, respectively. They were already used in measurements of several thermodynamic and transport properties (Kogej, 2010) and of molar mass values of the soluble PSCs (Prelesnik et al., 2011) where the knowledge of precise concentration is crucial.

In the past few years extracellular vesicles called exosomes have gained huge interest of scientific community since they show a great potential for human diagnostic and therapeutic applications. However, an ongoing challenge is accurate size characterization and quantification of exosomes because of the lack of reliable characterization techniques. In this work, the emphasis was focused on a method development to size-separate, characterize, and quantify small amounts of exosomes by asymmetrical-flow field-flow fractionation (AF4) technique coupled to a multidetection system (UV and MALS). Batch DLS (dynamic light-scattering) and NTA (nanoparticle tracking analysis) analyses of unfractionated exosomes were also conducted to evaluate their shape and internal structure, as well as their number density. The results show significant influence of cross-flow conditions and channel thickness on fractionation quality of exosomes, whereas the focusing time has less impact. The AF4/UV-MALS and DLS results display the presence of two particles subpopulations, that is, the larger exosomes and the smaller vesicle-like particles, which coeluted in AF4 together with impurities in early eluting peak. Compared to DLS and AF4-MALS results, NTA somewhat overestimates the size and the number density for larger exosome population, but it discriminates the smaller particle population.

An asymmetrical flow field-flow fractionation (AF4) technique coupled to a multiangle light scattering (MALS) detector with an embedded dynamic light scattering (DLS) module was introduced to study the size characteristics and shape of soft particles of various size and type: polystyrene nanosphere size standards, lipid droplets (LDs), and large unilamellar vesicles (LUVs). A range of flow velocities through the LS detector, at which accurate hydrodynamic size can be extracted from the DLS in flow mode, was studied since the particles subjected to a longitudinal flow exhibit not only the Brownian motion due to diffusion but also the translational movement. In addition, the impact of the longitudinal flow velocity on the shape of the artificial LUV of two different sizes and two different compositions was studied by MALS. For comparison, the conventional batch DLS and static light scattering (SLS) experiments without prior sample separation by size were performed. From a combination of batch and flow light scattering results, we concluded that the passage flow velocities at the detector used in this study, 0.2, 0.5, and 1 mL/min, have no significant impact on the shape of spherical vesicles; however, the flow DLS experiments give accurate hydrodynamic radius (R

The polyelectrolyte matrix tablets loaded with an oppositely charged drug exhibit complex drug-release mechanisms. In this study, the release mechanism of a cationic drug doxazosin mesylate (DM) from matrix tablets based on an anionic polyelectrolyte λ-carrageenan (λ-CARR) is investigated. The drug release rates from λ-CARR matrices are correlated with binding results based on potentiometric measurements using the DM ion-sensitive membrane electrode and with molecular characteristics of the DM-λ-CARR-complex particles through hydrodynamic size measurements. Experiments are performed in solutions with different ionic strength and with the addition of an anionic surfactant sodium dodecyl sulphate (SDS). It is demonstrated that in addition to swelling and erosion of tablets, the release rates depend strongly on cooperative interactions between DM and λ-CARR. Addition of SDS at concentrations below its critical micelle concentration (CMC) slows down the DM release through hydrophobic binding of SDS to the DM-λ-CARR complex. On the contrary, at concentrations above the CMC SDS pulls DM from the complex by forming mixed micelles with it and thus accelerates the release. Results involving SDS show that the concentration of surfactants that are naturally present in gastrointestinal environment may have a great impact on the drug release process.

In this investigation, a novel coating for viscose fabric surface modification was developed using a synergistic formulation between a natural antimicrobial cationic surfactant from lysine (MKM) and a biopolymer hyaluronic acid (HA). The interaction between MKM and HA in aqueous solutions, as well as the interactions between their synergistic formulation (HA-MKM) and viscose fabric (CV) were studied using pH-potentiometric titrations', turbidity measurements, the Kjeldahl method for the determination of nitrogen amounts, attenuated total reflectance fourier transform infrared spectroscopy, and scanning electron microscopy. The hydrophilic and antimicrobial properties of the functionalised CV were examined in order to evaluate its usages for medical applications. The results of the interaction studies showed that MKM and HA interact with each other by forming a precipitate when the binding sites of HA are saturated. The precipitate has a slightly positive charge at neutral pH due to excess binding of the MKM to HA. The excess positive charge was also detected on CV coated with HA-MKM. This was proven to be very beneficial for the antimicrobial properties of the functionalised CV. The antimicrobial tests showed exceptional antimicrobial activity of the functionalised CV against Escherichia Coli, Staphylococcus Aureus, Streptococcus Agalactiae, Candida Albicans, and Candida Glabrata, making the CV fabric highly interesting for potential use in medicine. © 2014 Springer Science+Business Media Dordrecht., The financial support of Savatech d.o.o., Industrial rubber products and tyres is gratefully acknowledged. The authors also acknowledge the financial support from the Ministry of Education, Science and Sport of the Republic of Slovenia through the program P2 0118 as well l as ARRS project L2-4060 .and the financial support from Spanish Plan National I+D+I MAT2012-38047-C02-02.

In this paper we show by light scattering techniques that polymer tacticity introduces an opposite association behavior in the case of aqueous solution of poly(methacrylic acid) in the presence of 0.1 M NaCl. Aggregates of highly stereoregular isotactic poly(methacrylic acid), iPMA, are disrupted by shear and gradually reform in solution at rest, whereas those of the usual atactic form, aPMA, multiply as a result of mechanical stress (phenomenon of negative thixotropy) and gradually decrease in number after its cessation. The aggregates have characteristics of microgel particles and may act as precursors for temperature induced gelation at higher concentrations. According to the shape parameter ρ (∼0.6 and ∼0.70 for iPMA and aPMA, respectively) iPMA aggregates have a denser core than aPMA ones. Additional differences between both isomers are demonstrated at higher degrees of neutralization, αN, through the analysis of the polyelectrolyte slow mode, which was identified for all αN > 0.25 with iPMA but only for αN = 1 with aPMA.

Nanostructured polyanilines (PANI) with various morphology were synthesized by polymerization of aniline with ammonium peroxodisulfate in acidic aqueous medium containing ionic liquids (ILs) with imidazolium, pyridinium and quaternary ammonium cations. The influence of the type of IL and the aniline/IL mole ratio on the morphology and properties of formed PANIs was investigated. ILs added to reaction mixture control the PANI morphology toward nanowires or various complex two- and three-dimensional structures in contrast to the morphology of agglomerated granular particles that is typical of PANIs prepared in the absence of IL. The UV–Vis, IR and Raman spectra of PANIs showed that the used ILs do not affect the chemical structure of PANI, which indicates that they do not affect the formation of PANI molecules but only their assembling during polymerization. The DLS measurements indicate that ILs as well as their mixtures with an oxidant and aniline form in 1 M HCl ordered micellar structures. The micellar structures most likely act as soft templates that assemble growing PANI chains and/or aniline molecules into particular nanostructures and/or their precursors. The fact that the structure of PANI nanoparticles is, in general, a function of the type of IL and IL/aniline concentration ratio, indicates that the architecture of micelles depends on the same variables.

Biofilm formation triggered by uncontrolled protein adsorption, on medical devices is the leading cause of catheter-associated urinary tract infections (CAUTI) during implantation. Herein, we report a water-based, green and one-step strategy to functionalize surfaces of silicone catheters, poly(dimethylsiloxane) (PDMS), with antifouling and antimicrobial substances to avoid uncontrolled protein adsorption and microbial attachment. A novel synergetic formulation consisting of an anionic glycosaminoglycan (hyaluronic acid, HA) and a lysine-derived biocompatible cationic surfactant (Nϵ-myristoyl-lysine methyl ester, MKM) was prepared, resulting in the formation of nanoparticles (NPs, ca. 100-250 nm). Besides their high stability and long-lasting hydrophilicity in ambient and aqueous environments for 60 days, the nanometric layers (48 ± 3 nm) of HA-MKM NPs on PDMS showed no adsorption of BSA and lysozyme and substantially lower adsorption of fibrinogen as revealed by a quartz crystal microbalance with dissipation (QCM-D). In vitro antimicrobial test with S. aureus, E. coli, P. aeruginosa, P. mirabilis, C. albicans microbes under dynamic conditions revealed that the microbial growth was hampered by 85% compared with unmodified PDMS. Given the multiple functionalities, charges and diverse physiochemical properties of polysaccharide-lysine-based surfactant mixtures, this approach can be easily extended to the development of novel coatings on other silicone-based materials, thereby broadening potential applicability of PDMS-based biomaterials/devices in microfluidics, diagnostic biosensors and others. © 2017 The Royal Society of Chemistry., L. Perez acknowledges Spanish Plan national I + D + I MAT2012-38047-C02-02. The authors are grateful to Mag. D. Reishofer and Assoc. Prof. Dr Thomas Grießer from the Technical University of Graz and University of Leoben for their help in regard of AFM, profilometry and XPS measurements. The authors are grateful for the financial support provided by the research program P2-0118 Textile chemistry and Slovenian Research Agency (project no. J2-7413). T. Mohan acknowledge the European Union WoodWisdom-NET+ project PShapes.

In this study the development of stable polyelectrolyte-surfactant complex nanoparticles composed of alginate and cetylpyridinium chloride (CPC), with and without ZnCl2, for therapeutic use, is investigated. The mechanism of CPC binding by alginate was analyzed using a cetylpyridinium cation (CP(+)) selective membrane electrode. The cooperative nature of the interaction between CP(+) and alginate was underlined by the sigmoidal shape of the binding isotherms. The presence of salts was shown to weaken interactions and, moreover, ZnCl2 reduced the cooperativity of binding. The CP(+) cations in the form of micellar associates acted as multivalent crosslinkers of the alginate chains where stable dispersions of CP-alginate nanoparticles were formed in water at CP(+)/alginate charge ratios from 0.2 to 0.8. Characterization of the nanoparticles showed hydrodynamic diameters from 140 to 200nm, a polydispersity index below 0.2, a negative zeta potential and spherical morphology. The entrapment efficiency of CPC was ∼94%, the loading capacity more than 50% and prolonged release over 7days were shown. The formulations with noted charge ratios resulted in stable CP-alginate nanoparticles with a potential of treating periodontal disease.

The affinity of amphiphilic compounds for water is important in various processes, e.g., in conformational transitions of biopolymers, protein folding/unfolding, partitioning of drugs in the living systems, and many others. Herein, we study the conformational transition of two isomer forms of poly(methacrylic acid) (PMA), isotactic (iPMA) and atactic (aPMA), in water. These isomers are chemically equivalent and differ only in the arrangement of functional groups along the chain. A complete thermodynamic analysis of the transition of the PMA chains from the compact to the extended form (comprising the conformational transition) in water in the presence of three alkali chlorides is conducted by determining the free energy, enthalpy, and entropy changes of the process as a function of temperature, and therefrom also the heat capacity change. The heat capacity change of the transition is positive (+20 J/K mol) for aPMA and negative (-50 J/K mol) for iPMA. This result suggests a different affinity of PMA isomers for water. The conformational transition of iPMA is parallel to the transfer of polar solutes into water, whereas that of aPMA agrees with the transfer of nonpolar solutes into water.

There are some molecular dynamic simulations but a paucity of experimental evidence of the effects of C-60 fullerene on lipid bilayers. The aim of this study is to assess the potential for disruption of the lipid bilayer by C-60 suspended in water. We selected a C-60 suspension that has previously been shown to provoke cell membrane destabilisation in vivo. Electromobility measurements show significant negative surface charge on the C-60 nanoparticles suspended in a glucose solution and a zeta potential of −26 mV. The prevalent C-60 clusters have hydrodynamic radii of approximately 2 nm. Phase contrast microscopy and computer aided image analysis results show that C-60 causes shape transformations and rupture of unilamellar phospholipid vesicles, indicative of changes in their average mean curvature. Small-angle X-ray scattering reveals that C-60 provokes disruptions of external membranes of multilamellar vesicles only after freeze and thaw cycles. Here, the liposomes undergo breakage and annealing steps which increase the probability for fullerenes to insert into the MLVs. Our experimental findings confirm the potential of C-60 to reconstruct lipids in biological membranes. This research enhances our understanding of the impact of engineered nanoparticles on cell membranes.

Organophilic nano ZnO particles have been synthesized in various diols (ethylene glycol - EG, 1,2 propane diol - PD, 1,4 butane diol - BD and tetra(ethylene glycol) - TEG) in the presence of p-toluenesulfonic acid, p-TsOH, as an end capping agent. The addition of p-TsOH reduces the ZnO particle size and increases its crystallite size. With increasing diol main chain length the ZnO particle size increases (EG (32 nm) < PD (33 nm) < BD (72 nm) < TEG (86 nm)). Using the as- synthesized and unmodified ZnO nanocomposites with poly(methyl methacrylate), PMMA, matrix have been prepared by the in-situ bulk polymerization of methyl methacrylate, MMA. The addition of surface modifiers is avoided which is an advantage for the application since they can influence other properties of the material. ZnO particles, especially those with smaller particle sizes (EG - 32 nm, PD - 33 nm) showed enhanced effect on the thermal stability of PMMA, ultraviolet, UV, absorption and transparency for visible light. Transparent materials with high UV absorption and with enhanced resist- ance to sunlight were obtained by optimizing the nanocomposite preparation procedure using ZnO particles of about 30 nm size in concentrations between 0.05 and 0.1 wt%. The reported nanocomposite preparation procedure is compatible with the industrial process of PMMA sheet production.

Investigations dealing with association behaviour and structure formation in oppositely charged polyelectrolyte-surfactant mixtures in aqueous solutions are reviewed. Discussion is limited to a selection of vinyl based anionic polyelectrolytes that, when completely ionized, posses the same structural value of the linear charge density parameter. Particular emphasis is placed on the role of polymer chain properties in aggregates with surfactants. Chain characteristics are varied by changing the nature of the charged group, its ionization degree - when possible, the spatial distribution of these groups along the chain, i.e. the tacticity, and the hydrophobic character of other substituents attached to the chain. Quantitative information on the degree of binding in the form of binding isotherms is obtained using surfactant-sensitive membrane electrodes and microstructures of polyelectrolyte-surfactant complexes are determined by synchrotron small angle X-ray scattering. Considerable differences in the degree of binding (including the critical association concentration, CAC, values) and in structures are found. It is concluded that strong interactions in these systems arise from the electrostatic attraction, but this only forms the basis for initial extensive accumulation (anchoring) of surfactant ions in the vicinity of the polyion chain. When this is accomplished, additional specific interactions and effects may come into play. The most powerful of these interactions, the hydrophobic association between the chain and the micelle core, were found in polystyrenesulfonate, PSS, solutions. Other properties are less influential but still lead to CAC values that differ by more than one order of magnitude. These differences are explained by taking into account the chain conformation, flexibility, and hydrophobic character. Specific interactions between PSS and cetylpyridinium, CP, cations result in a soluble non-stoichiometric PSS-CP complex that could be characterized by measuring various solution properties as a function of polymer concentration and degree of complexation. The review is supplemented by including studies of complexation between the spherical fullerene hexamalonate anion and cationic surfactants, which demonstrate a high association tendency with characteristics similar to those found in binding of surfactants by linear polyelectrolytes.

Perindopril Erbumine (PER) is one of the newly used angiotensin-converting enzyme inhibitors (ACE inhibitors) and is used for the treatment of patients with hypertension and symptomatic heart failure. It has two main degradation pathways, i.e. the degradation by hydrolysis and the degradation by cyclization. An isothermal heat conduction microcalorimetry (MC) and high pressure liquid chromatography (HPLC) were used for the characterization of aqueous solutions of PER and its stability properties. The rates of heat evolved during degradation of perindopril were measured by MC as a function of temperature and pH and from these data rate constant and change in enthalpy of the reactions were determined. With the HPLC method the concentration of perindopril and its degradation products were measured as a function of time in aqueous solutions of different pH that were stored at different temperatures. We demonstrated that reactions of degradation of perindopril at observed conditions follow the first order kinetics. The Arrhenius equation for each pH was determined. At pH 6.8 only one degradation pathway is present, i.e. the degradation by hydrolysis. Degradation constants for this pathway calculated from MC data are in good agreement with those obtained from HPLC. MC as a non-specific technique was shown to be useful in studies of PER when one reaction was present in the sample and also when more chemical and physical processes were simultaneously running.

Biomolecular profiling with Fourier-Transform InfraRed Microscopy was performed to distinguish the Zn2+-mediated effects on the crustacean (Porcellio scaber) digestive glands from the ones elicited by the ZnO nanoparticles (NPs). The exposure to ZnO NPs or ZnCl2 (1500 and 4000 µg Zn/g of dry food) activated different types of metabolic pathways: some were found in the case of both substances, some only in the case of ZnCl2, and some only upon exposure to ZnO NPs. Both the ZnO NPs and the ZnCl2 increased the protein (∼1312 cm−1; 1720–1485 cm−1/3000–2830 cm−1) and RNA concentration (∼1115 cm−1). At the highest exposure concentration of ZnCl2, where the effects occurred also at the organismal level, some additional changes were found that were not detected upon the ZnO NP exposure. These included changed carbohydrate (most likely glycogen) concentrations (∼1043 cm−1) and the desaturation of cell membrane lipids (∼3014 cm−1). The activation of novel metabolic pathways, as evidenced by changed proteins’ structure (at 1274 cm−1), was found only in the case of ZnO NPs. This proves that Zn2+ are not the only inducers of the response to ZnO NPs. Low bioavailable fraction of Zn2+ in the digestive glands exposed to ZnO NPs further supports the role of particles in the ZnO NP-generated effects. This study provides the evidence that ZnO NPs induce their own metabolic responses in the subtoxic range.

Key biological functions involved in cell survival have been studied to understand the difference between the impact of exposure to TiO2 nanoparticles (TiO2-NPs) and their bulk counterparts (bulk-TiO2). By selecting a unicellular eukaryotic model organism and applying proteomic analysis an overview of the possible impact of exposure could be obtained. In this study, we investigated the early response of unicellular eukaryotic protozoan Tetrahymena thermophila exposed to TiO2-NPs or bulk-TiO2 particles at subtoxic concentrations for this organism. The proteomic analysis based on 2DE + nLC-ESI-MS/MS revealed 930 distinct protein spots, among which 77 were differentially expressed and 18 were unambiguously identified. We identified alterations in metabolic pathways, including lipid and fatty acid metabolism, purine metabolism and energetic metabolism, as well as salt stress and protein degradation. This proteomic study is consistent with our previous findings, where the early response of T. thermophila to subtoxic concentrations of TiO2 particles included alterations in lipid and fatty acid metabolism and ion regulation. The response to the lowest TiO2-NPs concentration differed significantly from the response to higher TiO2-NPs concentration and both bulk-TiO2concentrations. Alterations on the physiological landscape were significant after exposure to both nano- and bulk-TiO2; however, no toxic effects were evidenced even at very high exposure concentrations. This study confirms the relevance of the alteration of the lipid profile and lipid metabolism in understanding the early impact of TiO2-NPs in eukaryotic cells, for example, phagocytosing cells like macrophages and ciliated cells in the respiratory epithelium. Funding agencies: Swedish Research Council-Natural Science; Carl Trygger Foundation; VINNOVA-Vinnmer program; Oscar Lilli Lamms Minne Foundation; Langmanska kulturfonden; Lars Hiertas Minne foundation; IKERBASQUE; Basque Foundation for science; Angpanneforening Research fo

The stability properties of enalapril maleate (EM) and of different tablet formulations including EM were studied by isothermal microcalorimetry and by high performance liquid chromatography (HPLC). It was shown that water content of the sample and elevated temperature have a high impact on stability properties of the substance itself and of the formulations including this substance. The degradation is more extensive at higher water content and at elevated temperature. The type of the tablet formulation (5 or 20mg EM tablet formulation) also has an impact: the 5 EM tablet formulation is the less stable one. The heat output of individual tablet formulations was used to evaluate the enthalpy changes and to calculate the difference in the amount of degraded EM between various samples. These results agreed satisfactorily with those obtained by HPLC. Isothermal microcalorimetry proved to be a fast and predictive method that could be used in preformulation studies to accelerate the pharmaceutical development and shorten the time before launching the product to the market.

The complexation between fullerene hexamalonate anions (FHM-) and dodecyl- (DP+) and cetylpyridinium (CP+) cations was studied in aqueous solutions in the absence and in the presence of NaCl by potentiometric and fluorimetric measurements. Results demonstrated a high association tendency between FHM- and cationic surfactants in aqueous solution, with characteristics similar to those found in complexes of linear polyelectrolytes with surfactants. It is proposed that FHM- spheres gradually arrange themselves into agglomerates of binding sites in conjunction with surfactant. SAXS studies on precipitated, wet surfactant/FHM- complexes suggest the formation of highly ordered lamellar and hexagonally packed cylinder structures.

Structural properties of complexes of poly(acrylate) anion (PA) and the cationic surfactants dodecylpyridinium (DPC) and cetylpyridinium chloride (CPC) were investigated by synchrotron X-ray scattering at various degrees of neutralization αN of poly(acrylic acid) (HPA) and at a fixed surfactant:polymer molar ratio. In all scattering curves, one broad (PA−DPC complexes, all αN-values, and PA−CPC complexes, αN = 0) or several sharp peaks (PA−CPC complexes, αN > 0) were observed, pointing to a high degree of ordering in these systems. The fundamental type of organization of surfactant is in the form of polymer-induced micelles that are clustered around the polymer. The multiple reflections in the case of PA−CPC complexes point to a Pm3n cubic structure. The calculated values of structural parameters indicate a larger degree of ordering in complexes at low αN-values (i.e., at αN < 0.5) than that at higher ones. This suggests that the binding of the surfactant by the polyelectrolyte is influenced by factors ot...

Mixtures of natural and biodegradable surfactants and ionic polysaccharides have attracted considerable research interest in recent years because they prosper as antimicrobial materials for medical applications. In the present work, interactions between the lysine-derived biocompatible cationic surfactant Nε-myristoyl-lysine methyl ester, abbreviated as MKM, and the sodium salt of hyaluronic acid (NaHA) are investigated in aqueous media by potentiometric titrations using the surfactant-sensitive electrode and pyrene-based fluorescence spectroscopy. The critical micelle concentration in pure surfactant solutions and the critical association concentration in the presence of NaHA are determined based on their dependence on the added electrolyte (NaCl) concentration. The equilibrium between the protonated (charged) and deprotonated (neutral) forms of MKM is proposed to explain the anomalous binding isotherms observed in the presence of the polyelectrolyte. The explanation is supported by theoretical model calculations of the mixed-micelle equilibrium and the competitive binding of the two MKM forms to the surface of the electrode membrane. It is suggested that the presence of even small amounts of the deprotonated form can strongly influence the measured electrode response. Such ionic-nonionic surfactant mixtures are a special case of mixed surfactant systems where the amount of the nonionic component cannot be varied independently as was the case for some of the earlier studies. © 2015 American Chemical Society., This work was partially supported by the Slovenian Research Agency, ARRS, through the Physical Chemistry program P1-0201, program P2 0118, and project L2-4060. LP generously thanks the Spanish Plan National I+D+I MAT2012-38047-C02-02.

The poly(acrylate) (PA)/surfactant and poly(methacrylic acid) (PMA)/surfactant complexes were investigated by synchrotron X-ray scattering at various degrees of neutralization, α, of the polyion and at a fixed surfactant to polyion charge ratio. At low α-values, the surfactant organizes into polymer-induced micelles that are attracted by the polymer through hydrophobic interactions. This is followed by a formation of a Pm3n cubic structure at higher α-values as a consequence of very strong electrostatic attractions between the polyion and charged surfactant aggregates. From the position of the maxima in the scattering curves, the characteristic distance d was obtained. In PA/surfactant complexes, d varies linearly with α. This is an indication of a smooth expansion of the PA chain upon neutralization. In PA/dodecylpyridinium chloride (DPC) solutions, d increases from 30.2 A at α = 0 to 36.6 A at α = 1, and correspondingly d increases from 44.1 to 51 A in the PA/CPC case. The d-value at α = 0 almost matche...

The aim of this study was to determine whether citric acid adsorbed onto cobalt ferrite (CoFe2O4) nanoparticles (NPs) influences the bioavailability of their constituents Co and Fe. Dissolution of Co and Fe was assessed by two measures: (i) in aqueous suspension using chemical analysis, prior to application onto the food of test organisms; and (ii) in vivo, measuring the bioavailability in the model terrestrial invertebrate (Porcellio scaber, Isopoda, Crustacea). The isopods were exposed to citric-acid-adsorbed CoFe2O4 NPs for 2 weeks, and tissue accumulation of Co and Fe was assessed. This was compared to pristine CoFe2O4 NPs, and CoCl2 and Fe(III) salts as positive controls. The combined data shows that citric acid enhances free metal ion concentration from CoFe2O4 NPs in aqueous suspension, although in vivo, very similar amounts of assimilated Co were found in isopods exposed to both types of NPs. Therefore, evaluation of the dissolution in suspension by chemical means is not a good predictor of metal assimilation of this model organism; body assimilation of Co and Fe is rather governed by the physiological capacity of P. scaber for the uptake of these metals. Moreover, we propose that citric acid, due to its chelating properties, may hinder the uptake of Co that dissolves from citric-acid-adsorbed CoFe2O4 NPs, if citric acid is present in sufficient quantity.

A comparative light-scattering study of isotactic and atactic poly(methacrylic acid), iPMA and aPMA, respectively, in aqueous solutions with added alkali chlorides, XCl (X = Li, Na, Cs), at 25 °C and XCl concentration of 0.1 mol L(-1), demonstrates that both PMA isomers are strongly associated at low degrees of neutralization, αN (= 0 for aPMA and 0.25 for iPMA), in the presence of all XCls. The shape parameter ρ and the scattering functions suggest that aggregates have the characteristics of microgel particles, with a dense core surrounded by a less dense shell. The extent of aggregation depends on the stereoregular structure of the polymer and on the type of the added cation. Li(+) and Na(+) ions support aggregation better than Cs(+) ions. Besides, iPMA chains are more strongly aggregated than aPMA chains and form particles with a denser core. A model of the aggregation process is suggested for iPMA. At high αN, a slow diffusive process (so-called extraordinary or anomalous mode in diffusion of polyelectrolytes), arising from electrostatic interactions between charged chains, is observed for both PMAs. Results suggest that under the same experimental conditions iPMA is effectively more charged than aPMA. The role of ions in the slow-mode phenomenon is less pronounced than in aggregation.

values), NaPSS/CPC (S/P < 1), and NaPA(NaPMA)/DPC (S/P < 1) complexes produced a micellelike organization of the surfactant along the polyion chain. The NaPSS-induced micelle is smaller in size than the ordinary one because of the inclusion of the aromatic rings on the PSS chain into the hydrophobic interior of the micelle. The size of the ordered elements in complexes with the hydrophilic NaPA and NaPMA corresponds to the radius of an ordinary globular micelle together with the thickness of the polyelectrolyte chain that surrounds it. (2) In NaPSS/CPC precipitate (S/P g 1), a hexagonal phase is observed with a unit cell parameter equal to 39.5 A. (3) The multiple reflections in the scattering curves of NaPA(NaPMA)/DPC complexes with S/P g 1 and of NaPA(NaPMA)/CPC ones for all S/P values point to some cubic structure. The cell constants of these mesophases correspond approximately to 2.5 diameters of a globular surfactant micelle. (4) In addition to a cubic phase, a well-pronounced hexagonal phase with a unit cell parameter of 40.5 A develops in the NaPA/CPC case with S/P g 1.

Synchrotron X-ray scattering was used for the structural investigation of complexes between anionic polyelectrolytes and cetylpyridinium chloride (CPC). According to the Bragg peaks, different types of ordering are proposed. Cetylpyridinium chloride in conjunction with carrageenan forms bilayers connecting rigid polysaccharide chains. In the presence of poly(styrenesul-fonate), several micelles are bound to one chain. They appear rather small in size due to specific interactions with this polyion. In poly(acrylate)/CPC and poly(methacrylate) /CPC solutions, a cubic structure is indicated.

The osmotic coefficient, the apparent molar volume, and the electrical conductivity of aqueous solutions of the homologous series of decyl-, undecyl-, dodecyl-, tridecyl-, tetradecyl-, pentadecyl-, and hexadecylpyridinium bromides (CnPyBr) have been determined at 25 °C. From these data the variation of the critical micelle concentration (cmc) with the chain length of the surfactant has been obtained. Measurements were performed usually at concentrations from well below to well above the cmc. From osmotic coefficient and conductivity measurements, the degree of counterion binding to micelles, β, has been calculated. It has been found that the values of β are rather insensitive to the chain length, and as expected, the values determined from transport measurement are lower than those from the osmotic pressure measurements. From the apparent molar volumes the aggregation numbers of alkylpyridinium bromides have been estimated, following simple geometrical considerations suggested by Tartar and Tanford.

Micelle formation of alkyltrimethylammonium surfactants (CnTMAB) in aqueous sodium poly(styrenesulfonate) (NaPSS) solutions was studied by fluorescence and conductivity measurements at 25 °C. The dependence of the aggregation phenomena on the chain length of the surfactant (n = 12, 14, 16, 18) and on the ionic strength of solutions was investigated. The critical aggregation concentration (cac) decreases with increasing hydrophobicity of the surfactant but remains approximately unchanged for C16TMAB and C18TMAB. The cac values are considerably lower than the critical micellization concentration (cmc) values for the same surfactant. The decrease is in the range from about three orders of magnitude for C12EDMAB in water to approximately 10 times for C18TMAB in 0.01 M NaBr. Furthermore, the cac for C12EDMAB and C14TMAB in NaPSS was found to increase slightly with increasing NaBr concentration but much less than, for instance, in sodium poly(acrylate) solutions. No significant effect of NaBr on cac values for ...