Bisurea-Based Supramolecular Polymers for Tunable Biomaterials.

Water-soluble supramolecular polymers show great potential to develop dynamic biomaterials with tailored properties. Here, we elucidate the morphology, stability and dynamicity of supramolecular polymers derived from bisurea-based monomers. An accessible synthetic approach from 2,4-toluene diisocyanate (TDI) as the starting material is developed. TDI has two isocyanates that differ in intrinsic reactivity, which allows to obtain functional, desymmetrized monomers in a one-step procedure. We explore how the hydrophobic/hydrophilic ratio affects the properties of the formed supramolecular polymers by increasing the number of methylene units from 10 to 12 keeping the hydrophilic hexa(ethylene glycol) constant. All bisurea-based monomers form long, fibrous structures with 3-5 monomers in the cross-section in water, indicating a proper hydrophobic\hydrophilic balance. The stability of the supramolecular polymers increases with an increasing amount of methylene units, whereas the dynamic nature of the monomers decreases. The introduction of one Cy3 dye affords modified supramolecular monomers, which co-assemble with the unmodified monomers into fibrous structures. All systems show excellent water-compatibility and no toxicity for different cell-lines. Importantly, in cell culture media, the fibrous structures remain present, highlighting the stability of these supramolecular polymers in physiological conditions. The results obtained here motivate further investigation of these bisurea-based building blocks as dynamic biomaterial.

Effects of Charge Density on Spread Hyperbranched Polyelectrolyte/Surfactant Films at the Air/Water Interface.

The interfacial structure and morphology of films spread from hyperbranched polyethylene imine/sodium dodecyl sulfate (PEI/SDS) aggregates at the air/water interface have been resolved for the first time with respect to polyelectrolyte charged density. A recently developed method to form efficient films from the dissociation of aggregates using a minimal quantity of materials is exploited as a step forward in enhancing understanding of the film properties with a view to their future use in technological applications. Interfacial techniques that resolve different time and length scales, namely, ellipsometry, Brewster angle microscopy, and neutron reflectometry, are used. Extended structures of both components are formed under a monolayer of the surfactant with bound polyelectrolytes upon film compression on subphases adjusted to pH 4 or 10, corresponding to high and low charge density of the polyelectrolyte, respectively. A rigid film is related to compact conformation of the PEI in the interfacial structure at pH 4, while it is observed that aggregates remain embedded in mobile films at pH 10. The ability to compact surfactants in the monolayer to the same extent as its maximum coverage in the absence of polyelectrolyte is distinct from the behavior observed for spread films involving linear polyelectrolytes, and intriguingly evidence points to the formation of extended structures over the full range of surface pressures. We conclude that the molecular architecture and charge density can be important parameters in controlling the structures and properties of spread polyelectrolyte/surfactant films, which holds relevance to a range of applications, such as those where PEI is used, including CO2 capture, electronic devices, and gene transfection.

The evolution of equilibrium poly(styrene sulfonate) and dodecyl trimethylammonium bromide supramolecular structure in dilute aqueous solution with increasing surfactant binding.

HYPOTHESIS: In the last 20 years, it has been demonstrated that oppositely charged polyelectrolyte-surfactant (PE-S) mixtures are prone to forming kinetically arrested non-equilibrium aggregates, which are present in the prepared mixtures from rather low surfactant-to-polymer-repeat-unit ratios. Practically, this means that the PE-S mixtures used for the structural investigations of the formed PE-S complexes are typically a mixture of the primary PE-S complexes and large non-equilibrium aggregates of close to charge-neutral complexes. EXPERIMENTS: In this work, we present a unique approach that allows the preparation of PE-S mixtures in the equilibrium one-phase region (surfactant binding ß, is typically below 80%) without forming non-equilibrium aggregates. We used this method to prepare equilibrium, non-aggregated complexes of sodium poly(styrene sulfonate) (NaPSS, Mw = 17 kDa) and dodecyltrimethylammonium bromide (DTAB) (ß = 10 - 70%) both in water and in an inert electrolyte (100 mM NaCl). The evolution of the complex structure was monitored by small-angle X-ray scattering (SAXS) as a function of increasing surfactant binding (ß), and the measured scattering data were fitted by suitable structural models on an absolute scale where concentrations, compositions, and scattering contrasts calculated from molecular properties are used as restraints. FINDINGS: We could show that at low binding (ß < 30%), the system is a mixture of bare polyelectrolyte coils and NaPSS-DTAB complexes containing a closed surfactant associates of low aggregation number wrapped by the polyelectrolyte chain. Once all polymer chains are occupied by a micelle-like surfactant aggregate, the aggregation number increases linearly with increasing surfactant chemical potential. Using the structural insight provided by the SAXS measurements, we could fit the experimental binding isotherm data with a physically coherent, simple thermodynamic model. Finally, we also compared the stoichiometric NaPSS-DTAB precipitate's structure with the equilibrium complexes' structure.

Assessment of Frontal Hemispherical Lateralization in Plaque Psoriasis and Atopic Dermatitis.

BACKGROUND: Each brain hemisphere plays a specialized role in cognitive and behavioral processes, known as hemispheric lateralization. In chronic skin diseases, such as plaque psoriasis (Pso) and atopic dermatitis (AD), the degree of lateralization between the frontal hemispheres may provide insight into specific connections between skin diseases and the psyche. This study aims to analyze the hemispherical lateralization, neurovegetative responses, and psychometric characteristics of patients with Pso and AD. METHODS: The study included 46 patients with Pso, 56 patients with AD, and 29 healthy control (Ctrl) subjects. The participants underwent frontal electroencephalogram (EEG) measurement, heart rate variability (HRV) assessment, and psychological tests. Statistical analyses were performed using ANOVA, with Bonferroni correction applied for multiple comparisons. RESULTS: This study shows a significant right-lateralized prefrontal activity in both AD patients (p < 0.001) and Pso patients (p = 0.045) compared with Ctrl, with no significant difference between the AD and Pso groups (p = 0.633). AD patients with right-hemispheric dominant prefrontal activation exhibited increased inhibition and avoidance markers, while Pso patients showed elevated sympathetic nervous system activity. CONCLUSION: Psychophysiological and psychometric data suggest a shared prevalence of right-hemispheric dominance in both AD and Pso patient groups. However, the findings indicate distinct psychodermatological mechanisms in AD and Pso.

Advancement of Fluorescent and Structural Properties of Bovine Serum Albumin-Gold Bioconjugates in Normal and Heavy Water with pH Conditioning and Ageing.

The red-emitting fluorescent properties of bovine serum albumin (BSA)-gold conjugates are commonly attributed to gold nanoclusters formed by metallic and ionized gold atoms, stabilized by the protein. Others argue that red fluorescence originates from gold cation-protein complexes instead, not gold nanoclusters. Our fluorescence and infrared spectroscopy, neutron, and X-ray small-angle scattering measurements show that the fluorescence and structural behavior of BSA-Au conjugates are different in normal and heavy water, strengthening the argument for the existence of loose ionic gold-protein complexes. The quantum yield for red-emitting luminescence is higher in heavy water (3.5%) than normal water (2.4%), emphasizing the impact of hydration effects. Changes in red luminescence are associated with the perturbations of BSA conformations and alterations to interatomic gold-sulfur and gold-oxygen interactions. The relative alignment of domains I and II, II and III, III and IV of BSA, determined from small-angle scattering measurements, indicate a loose ("expanded-like") structure at pH 12 (pD ~12); by contrast, at pH 7 (pD ~7), a more regular formation appears with an increased distance between the I and II domains, suggesting the localization of gold atoms in these regions.

Size Measurement of Extracellular Vesicles and Synthetic Liposomes: The Impact of the Hydration Shell and the Protein Corona.

Size characterization of extracellular vesicles (EVs) and drug delivery liposomes is of great importance in their applications in diagnosis and therapy of diseases. There are many different size characterization techniques used in the field, which often report different size values. Besides technological biases, these differences originate from the fact that various methods measure different physical quantities to determine particle size. In this study, the size of synthetic liposomes with nominal diameters of 50nm and 100nm, and red blood cell-derived EVs (REVs) were measured with established optical methods, such as dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA), and with emerging non-optical methods such as microfluidic resistive pulse sensing (MRPS) and very small-angle neutron scattering (VSANS). The comparison of the hydrodynamic sizes obtained by DLS and NTA with the sizes corresponding to the excluded volume of the particles by MRPS enabled the estimation of the thickness of the hydration shell of the particles. The comparison of diameter values corresponding to the boundary of the phospholipid bilayer obtained from VSANS measurements with MRPS size values revealed the thickness of the polyethylene glycol-layer in case of synthetic liposomes, and the thickness of the protein corona in case of REVs.

Effect of Temperature and Ionic Strength on Micellar Aggregates of Oppositely Charged Thermoresponsive Block Copolymer Polyelectrolytes.

The self-assembly of two oppositely charged diblock copolymers that have a common thermosensitive nonionic block of poly(N-isopropylacrylamide) (pNIPAAM) has been investigated. The effect of the mixing ratio and total polymer concentrations on the self-assembly of the components and on the phase stability of the mixtures was studied by dynamic light scattering, electrophoretic mobility, and turbidimetry measurements in water at 20 °C. The effect of the competing electrostatic and hydrophobic interactions on the nanostructure of negatively charged electrostatically self-assembled micelles bearing a pNIPAAM corona was investigated by small-angle X-ray scattering (SAXS). The electrostatic and hydrophobic interactions were controlled independently by tuning the ionic strength (from pure water to 50 mM NaCl) and the temperature (20-50 °C) of the investigated mixtures. The SAXS data could be fitted by a spherical micelle model, which has a smoothly decaying radial profile and a Gaussian star term that describes the internal structure of the micellar structures and possible attractive interactions between the polymer chains. At high temperature, a cluster structure factor was included for describing the formation of bulky clusters of the formed micelles. At low temperature and ionic strength, the formation of micelles with a coacervate core and hydrated pNIPAAM shell was observed. The structural evolution of the self-assembled micelles with increasing ionic strength and temperature could be followed, and finally at high ionic strength and temperature, the formation of inverted micelles with a hydrophobic core and polyelectrolyte shell could be identified.