Search Results (57)

This study investigated the influence of β-cyclodextrin (βCD) on the micellization behavior of two bile salt surfactants, sodium deoxycholate (NaDC) and sodium cholate (NaC), in aqueous solutions. Tensiometry, conductometric, and spectrofluorimetric techniques were employed to determine critical micelle concentrations (CMCs) in the presence of varying concentrations of βCD, as well as in the presence of inorganic salts (NaCl and CsCl). The results showed that βCD forms inclusion complexes with both bile salts, leading to an increase in their CMCs, consistent with a competitive interaction between micelle formation and complexation. The inclusion constants, determined graphically, revealed stronger complexation for NaDC than NaC, attributed to differences in hydrophobic surface area. Salt addition decreased the CMC of both surfactants, with CsCl having a more pronounced effect. However, salt presence also modulated the inclusion complex formation, suggesting specific ion effects influence the availability and behavior of βCD. These findings contribute to the understanding of bile salt–cyclodextrin interactions and their modulation by electrolytes, with implications for drug delivery and supramolecular chemistry. Full article

Aiming at the problem that conventional friction reducers used in fracturing cannot simultaneously possess properties such as temperature resistance, salt resistance, shear resistance, rapid dissolution, and low damage. Under the design concept of “medium-low molecular weight, salt-resistant functional monomer, supramolecular physical crosslinking aggregation, and enhanced chain mechanical strength”, acrylamide, sulfonic acid salt-resistant monomer 2-acrylamide-2-methylpropanesulfonic acid, hydrophobic association monomer, and rigid skeleton functional monomer acryloyl morpholine were introduced into the friction reducer molecular chain by free radical polymerization, and combined with the compound suspension technology to develop a new type of multi-functional viscous friction reducer suspension (SAMD), the comprehensive performance of SAMD was investigated. The results indicated that the critical micelle concentration of SAMD was 0.33 wt%, SAMD could be dissolved in 80,000 mg/L brine within 3.0 min, and the viscosity loss of 0.5 wt% SAMD solution was 24.1% after 10 min of dissolution in 80,000 mg/L brine compared with that in deionized water, the drag reduction rate of 0.1 wt% SAMD solution could exceed 70% at 120 °C and still maintained good drag reduction performance in brine with a salinity of 100,000 mg/L. After three cycles of 170 s⁻¹ and 1022 s⁻¹ variable shear, the SAMD solution restored viscosity quickly and exhibited good shear resistance. The Tan δ (a parameter characterizing the viscoelasticity of the system) of 1.0 wt% SAMD solution was 0.52, which showed a good sand-carrying capacity, and the proppant settling velocity in it could be as low as 0.147 mm/s at 120 °C, achieving the function of high drag reduction at low concentrations and strong sand transportation at high concentrations. The viscosity of 1.4 wt% SAMD was 95.5 mPa s after shearing for 120 min at 140 °C and at 170 s⁻¹. After breaking a gel, the SAMD solution system had a core permeability harm rate of less than 15%, while the SAMD solution also possessed the performance of enhancing oil recovery. Compared with common friction reducers, SAMD simultaneously possessed the properties of temperature resistance, salt resistance, shear resistance, rapid dissolution, low damage, and enhanced oil recovery. Therefore, the use of this multi-effect friction reducer is suitable for the development of unconventional oil reservoirs with a temperature lower than 140 °C and a salinity of less than 100,000 mg/L. Full article

Novel amphiphilic block copolymers of N-vinyl pyrrolidone (NVP) and either n-hexyl methacrylate (HMA, PNVP-b-PHMA) or stearyl methacrylate (SMA, PNVP-b-PSMA) were prepared by RAFT polymerization techniques and the sequential addition of monomers starting from the polymerization of NVP and using two different Chain Transfer Agents, CTAs. PNVP-b-PHMA are amorphous block copolymers containing constituent blocks with both high and low Tg values, whereas PNVP-b-PSMA are amorphous–semi-crystalline copolymers. Samples with different molecular weights and compositions were obtained. The copolymers were microphase-separated, but partial mixing was also observed. The presence of the amorphous PNVP block reduced the crystallinity of the PSMA blocks in the PNVP-b-PSMA copolymers. The thermal stability of the blocks was influenced by both constituents. The self-assembly behavior in THF, which is a selective solvent for polymethacrylate blocks, and in aqueous solutions, where PNVP was soluble, was examined. Unimolecular or low-aggregation-number micelles were obtained in THF for both types of samples. On the contrary, high-aggregation-number, spherical, and compact micelles were revealed in aqueous solutions. The increase in the steric hindrance of the side ester group of the polymethacrylate chain led to slightly lower degrees of association. The hydrophobic compound curcumin was efficiently encapsulated within the micellar core of the supramolecular structures in aqueous solutions. Micelles with higher aggregation numbers were more efficient in the encapsulation of curcumin. The results of this study were compared with those obtained from other block copolymers based on PNVP. Full article

Vaccination is credited as a significant medical achievement contributing to the decline in morbidity and mortality of infectious diseases. Traditional vaccines composed of inactivated and live-attenuated whole pathogens confer the induction of potent and long-term immune responses; however, traditional vaccines pose a high risk of eliciting autoimmune and allergic responses as well as inflammations. New modern vaccines, such as subunit vaccines, employ minimum pathogenic components (such as carbohydrates, proteins, or peptides), overcome the drawbacks of traditional vaccines and stimulate effective immunity against infections. However, the low immunogenicity of subunit vaccines requires effective immune stimulants (adjuvants), which are an indispensable factor in vaccine development. Although there are several approved adjuvants in human vaccines, the challenges of matching and designing appropriate adjuvants for specific vaccines, along with managing the side effects and toxicity of existing adjuvants in humans, are driving the development of new adjuvants. Self-assembling peptides are a promising biomaterial rapidly emerging in the fields of biomedicine, vaccination and material science. Here, peptides self-assemble into ordered supramolecular structures, forming different building blocks in nanoparticle size, including fibrils, tapes, nanotubes, micelles, hydrogels or nanocages, with great biostability, biocompatibility, low toxicity and effectiveness at controlled release. Self-assembling peptides are effective immunostimulatory agents used in vaccine development to enhance and prolong immune responses. This review describes the predominant structures of self-assembling peptides and summarises their recent applications as vaccine adjuvants. Challenges and future perspectives on self-assembled peptides as vaccine adjuvants are also highlighted. Full article

Phospholipase A2 (PLA2) is a superfamily of phospholipase enzymes that dock at the water/oil interface of phospholipid assemblies, hydrolyzing the ester bond at the sn-2 position. The enzymatic activity of these enzymes differs based on the nature of the substrate, its supramolecular assemblies (micelle, liposomes), and their composition, reflecting the interfacial nature of the PLA2s and requiring assays able to directly quantify this interaction of the enzyme(s) with these supramolecular assemblies. We developed and optimized a simple, universal assay method employing the pH-sensitive indicator dye bromothymol blue (BTB), in which different POPC (3-palmitoyl-2-oleoyl-sn-glycero-1-phosphocholine) self-assemblies (liposomes or mixed micelles with Triton X-100 at different molar ratios) were used to assess the enzymatic activity. We used this assay to perform a comparative analysis of PLA2 kinetics on these supramolecular assemblies and to determine the kinetic parameters of PLA2 isozymes IB and IIA for each supramolecular POPC assembly. This assay is suitable for assessing the inhibition of PLA2s with great accuracy using UV-VIS spectrophotometry, being thus amenable for screening of PLA2 enzymes and their substrates and inhibitors in conditions very similar to physiologic ones. Full article

Salt-induced diffusiophoresis is the migration of a colloidal particle in water due to a directional salt concentration gradient. An important example of colloidal particles is represented by micelles, generated by surfactant self-assembly in water. For non-ionic surfactants containing polyethylene glycol (PEG) groups, PEG preferential hydration at the micelle–water interface is expected to drive micelle diffusiophoresis from high to low salt concentration. However, micelles are reversible supramolecular assemblies, with salts being able to promote a significant change in micelle size. This phenomenon complicates the description of diffusiophoresis. Specifically, it is not clear to what extent the salt-induced growth of micelles affects micelle diffusiophoresis. In this paper, a multiple-equilibrium model is developed for assessing the contribution of the micelle growth and preferential hydration mechanisms to the diffusiophoresis of non-ionic micelles. The available experimental data characterizing the effect of NaCl on Triton X-100 aggregation number are combined with data on diffusiophoresis and the preferential hydration of PEG chains to show that the contribution of the micelle growth mechanism to overall diffusiophoresis is small compared to that of preferential hydration. Full article

The supramolecular solvent (SUPRAS) has garnered significant attention as an innovative, efficient, and environmentally friendly solvent for the effective extraction and separation of bioactive compounds from natural resources. However, research on the use of a SUPRAS for the extraction of phenolic compounds from plants, which are highly valued in food products due to their exceptional antioxidant properties, remains scarce. The present study developed a green, ultra-sound-assisted SUPRAS method for the simultaneous determination of three phenolic acids in Prunella vulgaris using high-performance liquid chromatography (HPLC). The experimental parameters were meticulously optimized. The efficiency and antioxidant properties of the phenolic compounds obtained using different extraction methods were also compared. Under optimal conditions, the extraction efficiency of the SUPRAS, prepared with octanoic acid reverse micelles dispersed in ethanol–water, significantly exceeded that of conventional organic solvents. Moreover, the SUPRAS method demonstrated greater antioxidant capacity. Confocal laser scanning microscopy (CLSM) images revealed the spherical droplet structure of the SUPRAS, characterized by a well-defined circular fluorescence position, which coincided with the position of the phenolic acids. The phenolic acids were encapsulated within the SUPRAS droplets, indicating their efficient extraction capacity. Furthermore, molecular dynamics simulations combined with CLSM supported the proposed method’s mechanism and theoretically demonstrated the superior extraction performance of the SUPRAS. In contrast to conventional methods, the higher extraction efficiency of the SUPRAS can be attributed to the larger solvent contact surface area, the formation of more types of hydrogen bonds between the extractants and the supramolecular solvents, and stronger, more stable interaction forces. The results of the theoretical studies corroborate the experimental outcomes. Full article

Ferrocene has been the most used organometallic moiety introduced in organic and bioinorganic drugs to cure cancers and various other diseases. Following several pioneering studies, two real breakthroughs occurred in 1996 and 1997. In 1996, Jaouen et al. reported ferrocifens, ferrocene analogs of tamoxifen, the chemotherapeutic for hormone-dependent breast cancer. Several ferrocifens are now in preclinical evaluation. Independently, in 1997, ferroquine, an analog of the antimalarial drug chloroquine upon the introduction of a ferrocenyl substituent in the carbon chain, was reported by the Biot-Brocard group and found to be active against both chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum. Ferroquine, in combination with artefenomel, completed phase IIb clinical evaluation in 2019. More than 1000 studies have been published on ferrocenyl-containing pharmacophores against infectious diseases, including parasitic, bacterial, fungal, and viral infections, but the relationship between structure and biological activity has been scarcely demonstrated, unlike for ferrocifens and ferroquines. In a majority of ferrocene-containing drugs, however, the production of reactive oxygen species (ROS), in particular the OH. radical, produced by Fenton catalysis, plays a key role and is scrutinized in this mini-review, together with the supramolecular approach utilizing drug delivery nanosystems, such as micelles, metal–organic frameworks (MOFs), polymers, and dendrimers. Full article

So far, it has been difficult to directly compare diverse characteristic gelation mechanisms over different length and time scales. This paper presents a universal water structure analysis of several gels with different structures and gelation mechanisms including polymer gels, supramolecular gels composed of surfactant micelles, and cement gels. The spatial distribution of water molecules was analyzed at molecular level from a diagram of the relaxation times and their distribution parameters (τ–β diagrams) with our database of the 10 GHz process for a variety of aqueous systems. Polymer gels with volume phase transition showed a small decrease in the fractal dimension of the hydrogen bond network (HBN) with gelation. In supramolecular gels with rod micelle precursor with amphipathic molecules, both the elongation of the micelles and their cross-linking caused a reduction in the fractal dimension. Such a reduction was also found in cement gels. These results suggest that the HBN inevitably breaks at each length scale with relative increase in steric hindrance due to cross-linking, resulting in the fragmentation of collective structures of water molecules. The universal analysis using τ–β diagrams presented here has broad applicability as a method to characterize diverse gel structures and evaluate gelation processes. Full article

There are various types of gel materials used in a wide range of fields, and their gelation mechanisms are extremely diverse. Furthermore, in the case of hydrogels, there exist some difficulties in understanding complicated molecular mechanisms especially with water molecules interacting through hydrogen bonding as solvents. In the present work, the molecular mechanism of the structural formation of fibrous super-molecular gel by the low molecular weight gelator, N-oleyl lactobionamide/water mixture was elucidated using the broadband dielectric spectroscopy (BDS) method. The dynamic behaviors observed for the solute and water molecules indicated hierarchical structure formation processes in various time scales. The relaxation curves obtained at various temperatures in the cooling and heating processes showed relaxation processes respectively reflecting the dynamic behaviors of water molecules in the 10 GHz frequency region, solute molecules interacting with water in MHz region, and ion-reflecting structures of the sample and electrode in kHz region. These relaxation processes, characterized by the relaxation parameters, showed remarkable changes around the sol–gel transition temperature, 37.8 °C, determined by the falling ball method and over the temperature range, around 53 °C. The latter change suggested a structure formation of rod micelles appearing as precursors before cross-linking into the three-dimensional network of the supramolecular gels. These results clearly demonstrate how effective relaxation parameter analysis is for understanding the gelation mechanism in detail. Full article

The global outbreak of SARS-CoV-2/COVID-19 provided the stage to accumulate an enormous biomedical data set and an opportunity as well as a challenge to test new concepts and strategies to combat the pandemic. New research and molecular medical protocols may be deployed in different scientific fields, e.g., glycobiology, nanopharmacology, or nanomedicine. We correlated clinical biomedical data derived from patients in intensive care units with structural biology and biophysical data from NMR and/or CAMM (computer-aided molecular modeling). Consequently, new diagnostic and therapeutic approaches against SARS-CoV-2 were evaluated. Specifically, we tested the suitability of incretin mimetics with one or two pH-sensitive amino acid residues as potential drugs to prevent or cure long-COVID symptoms. Blood pH values in correlation with temperature alterations in patient bodies were of clinical importance. The effects of biophysical parameters such as temperature and pH value variation in relation to physical-chemical membrane properties (e.g., glycosylation state, affinity of certain amino acid sequences to sialic acids as well as other carbohydrate residues and lipid structures) provided helpful hints in identifying a potential Achilles heel against long COVID. In silico CAMM methods and in vitro NMR experiments (including ³¹P NMR measurements) were applied to analyze the structural behavior of incretin mimetics and SARS-CoV fusion peptides interacting with dodecylphosphocholine (DPC) micelles. These supramolecular complexes were analyzed under physiological conditions by ¹H and ³¹P NMR techniques. We were able to observe characteristic interaction states of incretin mimetics, SARS-CoV fusion peptides and DPC membranes. Novel interaction profiles (indicated, e.g., by ³¹P NMR signal splitting) were detected. Furthermore, we evaluated GM1 gangliosides and sialic acid-coated silica nanoparticles in complex with DPC micelles in order to create a simple virus host cell membrane model. This is a first step in exploring the structure–function relationship between the SARS-CoV-2 spike protein and incretin mimetics with conserved pH-sensitive histidine residues in their carbohydrate recognition domains as found in galectins. The applied methods were effective in identifying peptide sequences as well as certain carbohydrate moieties with the potential to protect the blood–brain barrier (BBB). These clinically relevant observations on low blood pH values in fatal COVID-19 cases open routes for new therapeutic approaches, especially against long-COVID symptoms. Full article

Block copolymers of N-vinyl pyrrolidone (NVP) and benzyl methacrylate (BzMA), PNVP-b-PBzMA, were prepared by RAFT polymerization techniques and sequential addition of monomers. The copolymers were characterized by Size Exclusion Chromatography (SEC) and NMR spectroscopy. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG) were employed to study the thermal properties of these copolymers. The micellization behavior in THF, which is a selective solvent for the PBzMA blocks, was examined. For comparison the self-assembly properties of the corresponding statistical copolymers, PNVP-stat-PBzMA, were studied. In addition, the association behavior in aqueous solutions was analyzed for the block copolymers, PNVP-b-PBzMA. In this case, the solvent is selective for the PNVP blocks. Dilute solution viscometry, static (SLS) and dynamic light scattering (DLS) were employed as the tools to investigate the micellar assemblies. The efficient encapsulation of the hydrophobic curcumin within the micellar core of the supramolecular structures in aqueous solutions was demonstrated by UV-Vis spectroscopy and DLS measurements. Full article

This study describes the synthesis of novel amphiphilic linear-dendritic block copolymers and their self-assembly in water to form supramolecular nanoreactors capable of catalyzing Suzuki-Miyaura coupling reactions under “green” conditions. The block copolymers were formed through copper(I)-catalyzed alkyne-azide cycloaddition between azide functionalized poly(benzyl ether) dendrons as the perfectly branched blocks, as well as bis-alkyne modified poly(ethylene glycol), PEG, as the linear block. A first-generation poly(benzyl ether) dendron (G1) was coupled to a bis-alkyne modified PEG with molecular mass of 5 kDa, forming an ABA copolymer (G1)₂-PEG5k-(G1)₂ (yield 62%), while a second-generation dendron (G2) was coupled to a 11 kDa bis-alkyne modified PEG to produce (G2)₂-PEG11k-(G2)₂ (yield 49%). The structural purity and low dispersity of the linear-dendritic copolymers were verified by size-exclusion chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Their self-assembly was studied by dynamic light scattering, showing that (G1)₂-PEG5k-(G1)₂ and (G2)₂-PEG11k-(G2)₂ formed single populations of micelles (17 nm and 37 nm in diameter, respectively). The triazole rings located at the boundaries between the core and the corona are efficient chelating groups for transition metals. The ability of the micelles to complex Pd was confirmed by ¹H NMR, transmission electron microscopy, and inductively coupled plasma. The catalytic activity of the supramolecular linear-dendritic/Pd complexes was tested in water by model Suzuki-Miyaura reactions in which quantitative yields were achieved within 3 h at 40 °C, while, at 17 °C, a yield of more than 70% was attained after 17 h. Full article

It has recently been shown that the titer of the SARS-CoV-2 virus decreases in a cell culture when the cell suspension is irradiated with electromagnetic waves at a frequency of 95 GHz. We assumed that a frequency range in the gigahertz and sub-terahertz ranges was one of the key aspects in the “tuning” of flickering dipoles in the dispersion interaction process of the surfaces of supramolecular structures. To verify this assumption, the intrinsic thermal radio emission in the gigahertz range of the following nanoparticles was studied: virus-like particles (VLP) of SARS-CoV-2 and rotavirus A, monoclonal antibodies to various RBD epitopes of SARS-CoV-2, interferon-α, antibodies to interferon-γ, humic–fulvic acids, and silver proteinate. At 37 °C or when activated by light with λ = 412 nm, these particles all demonstrated an increased (by two orders of magnitude compared to the background) level of electromagnetic radiation in the microwave range. The thermal radio emission flux density specifically depended on the type of nanoparticles, their concentration, and the method of their activation. The thermal radio emission flux density was capable of reaching 20 μW/(m² sr). The thermal radio emission significantly exceeded the background only for nanoparticles with a complex surface shape (nonconvex polyhedra), while the thermal radio emission from spherical nanoparticles (latex spheres, serum albumin, and micelles) did not differ from the background. The spectral range of the emission apparently exceeded the frequencies of the Ka band (above 30 GHz). It was assumed that the complex shape of the nanoparticles contributed to the formation of temporary dipoles which, at a distance of up to 100 nm and due to the formation of an ultrahigh strength field, led to the formation of plasma-like surface regions that acted as emitters in the millimeter range. Such a mechanism makes it possible to explain many phenomena of the biological activity of nanoparticles, including the antibacterial properties of surfaces. Full article

Objectives. This study was aimed at the investigation of the supramolecular systems based on cationic surfactants bearing cyclic head groups (imidazolium and pyrrolidinium) and polyanions (polyacrylic acid (PAA) and human serum albumin (HSA)), and factors governing their structural behavior to create functional nanosystems with controlled properties. Research hypothesis. Mixed PE–surfactant complexes based on oppositely charged species are characterized by multifactor behavior strongly affected by the nature of both components. It was expected that the transition from a single surfactant solution to an admixture with PE might provide synergetic effects on structural characteristics and functional activity. To test this assumption, the concentration thresholds of aggregation, dimensional and charge characteristics, and solubilization capacity of amphiphiles in the presence of PEs have been determined by tensiometry, fluorescence and UV-visible spectroscopy, and dynamic and electrophoretic light scattering. Results. The formation of mixed surfactant–PAA aggregates with a hydrodynamic diameter of 100–180 nm has been shown. Polyanion additives led to a decrease in the critical micelle concentration of surfactants by two orders of magnitude (from 1 mM to 0.01 mM). A gradual increase in the zeta potential of HAS–surfactant systems from negative to positive value indicates that the electrostatic mechanism contributes to the binding of components. Additionally, 3D and conventional fluorescence spectroscopy showed that imidazolium surfactant had little effect on HSA conformation, and component binding occurs due to hydrogen bonding and Van der Waals interactions through the tryptophan amino acid residue of the protein. Surfactant–polyanion nanostructures improve the solubility of lipophilic medicines such as Warfarin, Amphotericin B, and Meloxicam. Perspectives. Surfactant–PE composition demonstrated beneficial solubilization activity and can be recommended for the construction of nanocontainers for hydrophobic drugs, with their efficacy tuned by the variation in surfactant head group and the nature of polyanions. Full article