Gels Obtained by Colloidal Self-Assembly of Amphiphilic Molecules

The Volatile Compounds Composition of Different Parts of Wild Kazakhstan Sedum ewersii Ledeb

The chemical composition of Sedum ewersii Ledeb., a plant indigenous to Kazakhstan and traditionally utilized in folk medicine, was comprehensively investigated, with a focus on its various plant parts. Fresh samples collected in May 2023 from the Almaty region underwent hydrodistillation to extract volatile components, followed by analysis using gas chromatography coupled with mass spectrometric detection, which identified a total of 71 compounds across different plant parts, including the root (underground part), root (aerial part), leaf, stem, and flowering aerial part. The predominant biologically active compound identified across all plant parts was Ethyl α-D-glucopyranoside. Monoterpenes, recognized as primary secondary metabolites, were notably abundant in each plant part, with varying compositions: the root (underground part) contained 28.58% aliphatic monoterpenes, 54.41% oxygenated monoterpenoids, 1.42% diterpenoids, and 15.59% other compounds; the root (aerial part) exhibited 1.34% aliphatic monoterpenes, 31.28% oxygenated monoterpenoids, 6.16% diterpenoids, and 61.22% other compounds; the stem and leaves showed 3.06% aliphatic monoterpenes, 21.49% oxygenated monoterpenoids, 17.99% diterpenoids, and 57.46% other compounds; and the flowering aerial part displayed 8.20% aliphatic monoterpenes, 53.18% oxygenated monoterpenoids, 23.75% diterpenoids, and 14.87% other compounds. Diterpenes, particularly Phytol, were prominently present in the leaf, stem, and flowering aerial parts. Additionally, a diverse array of organic acids, ketones, and phenolic compounds were identified across the plant parts, each potentially offering distinct pharmacological benefits. The presence of exclusive compounds in specific plant parts, such as Dihydroxyacetone in the root (aerial part), underscored the pharmacological diversity of S. ewersii. This study provides valuable insights into the chemical diversity and pharmacological potential of S. ewersii, suggesting promising applications in pharmaceutical and medicinal fields. Further research aimed at elucidating the individual and synergistic pharmacological effects of these compounds is crucial to fully harness the therapeutic benefits of this plant.

Tailoring Waterborne Coating Rheology with Hydrophobically Modified Ethoxylated Urethanes (HEURs): Molecular Architecture Insights Supported by CG-MD Simulations

A novel investigation of the effects of the hydrophilic and hydrophobic segments of hydrophobically modified ethoxylated urethanes (HEURs) on the rheological properties of their aqueous solutions, latex-based emulsions, and waterborne paints is demonstrated. Different HEUR thickeners were produced by varying the poly(ethylene glycol) (PEG) molecular weight and terminal hydrophobic size. Results reveal that the strength of hydrophobic associations and, consequently, the rheological properties of HEUR formulations can be effectively controlled by modifying the structure of the hydrophobic segment, specifically, the combination of diisocyanate and monoalcohol. This allows for the on-demand attainment of diverse rheological behaviors ranging from predominantly Newtonian profiles exhibiting lower viscosities to markedly pseudoplastic behaviors with significantly higher viscosities. The length of the hydrophilic group appears to affect viscosity only marginally up to a molecular weight of 23,000 g/mol, with more notable effects at 33,000 g/mol. Additionally, it was indicated that the rheological responses observed in water solutions provide a reliable forecast of their behavior in latex-based emulsions and waterborne paints. Coarse-grained molecular dynamics (CG-MD) simulations were also applied to gain insight into HEUR micelle dynamics in aqueous solutions. Guided by the DBSCAN algorithm, the simulations successfully captured the concentration-dependent behavior and the impact of hydrophilic chain length, aligning with the experimental viscosity trends. Various metrics were employed to provide a comprehensive analysis of the micellization process, including the hydrophobic cluster volume, the total micellar volume, the aggregation number, and the number of chains interconnecting with other micelles.

Lyotropic liquid crystalline phases: Drug delivery and biomedical applications

Liquid crystal (LC)-based nanoformulations may efficiently deliver drugs and therapeutics to targeted biological sites. Lyotropic liquid crystalline phases (LLCPs) have received much interest in recent years due to their unique structural characteristics of both isotropic liquids and crystalline solids. These LLCPs can be utilized as promising drug delivery systems to deliver drugs, proteins, peptides and vaccines because of their improved drug loading, stabilization, and controlled drug release. The effects of molecule shape, microsegregation, and chirality are very important in the formation of liquid crystalline phases (LCPs). Homogenization of self-assembled amphiphilic lipids, water and stabilizers produces LLCPs with different types of mesophases, bicontinuous cubic (cubosomes) and inverse hexagonal (hexosomes). Moreover, many studies have also shown higher bioadhesivity and biocompatibility of LCs due to their structural resemblance to biological membranes, thus making them more efficient for targeted drug delivery. In this review, an outline of the engineering aspects of LLCPs and polymer-based LLCPs is summarized. Moreover, it covers parenteral, oral, transdermal delivery and medical imaging of LC in targeting various tissues and is discussed with a scope to design more efficient next-generation novel nanosystems. In addition, a detailed overview of advanced liquid crystal-based drug delivery for vaccines and biomedical applications is reviewed.

Colon-Adhering Delivery System with Inflammation Responsiveness for Localized Therapy of Experimental Colitis

Ulcerative colitis (UC) is a chronic inflammation-related disease that severely affects the colon and rectum regions. A variety of therapy regimens are used for the treatment of UC. Clinically, therapeutic enema is the choice of therapy for UC patients. Irrespective of on-site administration, the major limitation of therapeutic enemas is the dispossession of the medicine followed by low drug availability for the therapeutic action. In our present work, we have developed an enzyme-responsive injectable hydrogel (ER-hydrogel) to overcome the limitations of therapeutic enema. The hydrogels possess two major advantages, which are being exploited for therapeutic drug delivery in UC: prolonged retention and enzyme responsiveness. The former is one of the prominent advantages of hydrogel compared to free drug enema and the latter controls the release of the drug or provides drug release on-demand. The ER-hydrogel was formulated by the heat-cool method and for therapeutic purposes, a corticosteroid drug, budesonide (Bud), was encapsulated into the ER-hydrogel and evaluated for its various physicochemical and therapeutic potentials in dextran sodium sulfate (DSS)-induced UC. In vitro and ex vivo adhesion studies confirm the retention or mucoadhesive nature of the ER-hydrogel, and the upsurge in Bud release from the Bud-loaded ER-hydrogel upon the addition of esterase enzyme confirms the enzyme-mediated drug release from the ER-hydrogel. Moreover, Bud-loaded ER-hydrogel exhibited promising results in alleviating the disease activity index of UC, and restored the length of the colon, which is the main hallmark of UC. In terms of the health of the colon tissue, the Bud-loaded ER-hydrogel restored the colonic tissue damage, as seen in the H&E-stained, AB-NR-stained, and HID-AB-stained colon sections. Finally, the Bud-loaded ER-hydrogel also markedly subsided the IL-1β, TNF-α, MPO, and nitrite levels in serum and colon tissues. Thus, the fabricated Bud-loaded ER-hydrogel possesses appreciable translational potential due to its ability to significantly ameliorate inflammatory changes compared to naive or water-based therapeutic enema in acute experimental colitis in mice.

Molecular Tuning of a Benzene-1,3,5-Tricarboxamide Supramolecular Fibrous Hydrogel Enables Control over Viscoelasticity and Creates Tunable ECM-Mimetic Hydrogels and Bioinks

Traditional synthetic covalent hydrogels lack the native tissue dynamics and hierarchical fibrous structure found in the extracellular matrix (ECM). These dynamics and fibrous nanostructures are imperative in obtaining the correct cell/material interactions. Consequently, the challenge to engineer functional dynamics in a fibrous hydrogel and recapitulate native ECM properties remains a bottle-neck to biomimetic hydrogel environments. Here, the molecular tuning of a supramolecular benzene-1,3,5-tricarboxamide (BTA) hydrogelator via simple modulation of hydrophobic substituents is reported. This tuning results in fibrous hydrogels with accessible viscoelasticity over 5 orders of magnitude, while maintaining a constant equilibrium storage modulus. BTA hydrogelators are created with systematic variations in the number of hydrophobic carbon atoms, and this is observed to control the viscoelasticity and stress-relaxation timescales in a logarithmic fashion. Some of these BTA hydrogels are shear-thinning, self-healing, extrudable, and injectable, and can be 3D printed into multiple layers. These hydrogels show high cell viability for chondrocytes and human mesenchymal stem cells, establishing their use in tissue engineering applications. This simple molecular tuning by changing hydrophobicity (with just a few carbon atoms) provides precise control over the viscoelasticity and 3D printability in fibrillar hydrogels and can be ported onto other 1D self-assembling structures. The molecular control and design of hydrogel network dynamics can push the field of supramolecular chemistry toward the design of new ECM-mimicking hydrogelators for numerous cell-culture and tissue-engineering applications and give access toward highly biomimetic bioinks for bioprinting.

Enhancement of polymer thermoresponsiveness and drug delivery across biological barriers by addition of small molecules

Thermoresponsive polymers that undergo sol-gel transitions in the physiological temperature range have been widely used in biomedical applications. However, some commercially and clinically available thermoresponsive materials, particularly poloxamer 407 (P407), have the significant drawback of insufficient gel strength, which limit their performance. Furthermore, co-delivery with some small molecules, including chemical permeation enhancers (CPEs) can further impair the physical properties of P407. Here, we have developed a thermoresponsive platform by combination of CPEs with the poloxamer P188 to enable gelation at physiological temperatures and enhance gel strength. P188 gels at 60 °C, which is far above the physiological range. In combination with limonene (LIM) and sodium dodecyl sulfate (SDS), P188 gels at ∼25 °C, a temperature that in useful for biomedical applications. Gelation behavior was studied by small angle neutron scattering (SANS) experiments, which identified micelle-to-cubic mesophase transitions with increasing temperature. Analysis of the SANS intensities revealed that P188 micelles became larger as LIM or SDS molecules were incorporated, making it easier to form a micellar gel structure. P188-3CPE (i.e., 2% LIM, 1% SDS and 0.5% bupivacaine (BUP)) had low viscosity at room temperature, facilitating administration, but rapidly gelled at body temperature. P188-3CPE enabled the flux of the antibiotic ciprofloxacin across the TM and completely eradicated otitis media from nontypable Haemophilus influenzae (NTHi) in chinchillas after a single administration.

Role of Hydrophobic Associations in Self-Healing Hydrogels Based on Amphiphilic Polysaccharides

Self-healing hydrogels have the ability to recover their original properties after the action of an external stress, due to presence in their structure of reversible chemical or physical cross-links. The physical cross-links lead to supramolecular hydrogels stabilized by hydrogen bonds, hydrophobic associations, electrostatic interactions, or host-guest interactions. Hydrophobic associations of amphiphilic polymers can provide self-healing hydrogels with good mechanical properties, and can also add more functionalities to these hydrogels by creating hydrophobic microdomains inside the hydrogels. This review highlights the main general advantages brought by hydrophobic associations in the design of self-healing hydrogels, with a focus on hydrogels based on biocompatible and biodegradable amphiphilic polysaccharides.

Interaction of TX-100 and Antidepressant Imipramine Hydrochloride Drug Mixture: Surface Tension, 1H NMR, and FT-IR Investigation

Interfacial interaction amongst the antidepressant drug-imipramine hydrochloride (IMP) and pharmaceutical excipient (triton X-100 (TX-100-nonionic surfactant)) mixed system of five various ratios in dissimilar media (H₂O/50 mmol·kg⁻¹ NaCl/250 mmol·kg⁻¹ urea) was investigated through the surface tension method. In addition, in the aqueous solution, the ¹H-NMR, as well as FT-IR studies of the studied pure and mixed system were also explored and deliberated thoroughly. In NaCl media, properties of pure/mixed interfacial surfaces enhanced as compared with the aqueous system, and consequently the synergism/attractive interaction among constituents (IMP and TX-100) grew, whereas in urea (U) media a reverse effect was detected. Surface excess concentration (Γ_max), composition of surfactant at mixed monolayer (X1σ), activity coefficient (f₁^σ (TX-100) and f₂^σ (IMP)), etc. were determined and discussed thoroughly. At mixed interfacial surfaces interaction, parameter (β^σ) reveals the attractive/synergism among the components. The Gibbs energy of adsorption (ΔGadso) value attained was negative throughout all employed media viewing the spontaneity of the adsorption process. The ¹H NMR spectroscopy was also employed to examine the molecular interaction of IMP and TX-100 in an aqueous system. FT-IR method as well illustrated the interaction amongst the component. The findings of the current study proposed that TX-100 surfactant could act as an efficient drug delivery vehicle for an antidepressant drug. Gels can be used as drug dosage forms due to recent improvements in the design of surfactant systems. Release mechanism of drugs from surfactant/polymer gels is dependent upon the microstructures of the gels and the state of the drugs within the system.

Influences of NaCl and Na2SO4 on the Micellization Behavior of the Mixture of Cetylpyridinium Chloride + Polyvinyl Pyrrolidone at Several Temperatures

Herein, the conductivity measurement technique is used to determine the interactions that may occur between polyvinyl pyrrolidone (PVP) polymer and cetylpyridinium chloride (CPC) surfactant in the presence of NaCl and Na2SO4 of fixed concentration at variable temperatures (298.15-323.15 K) with an interval of 5 K. In the absence or presence of salts, we observed three critical micelle concentrations (CMC) for the CPC + PVP mixture. In all situations, CMC1 values of CPC + PVP system were found to be higher in water than in attendance of salts (NaCl and Na2SO4). Temperature and additives have the tendency to affect counterion binding values. Various physico-chemical parameters were analyzed and demonstrated smoothly, including free energy (ΔG0m), enthalpy (ΔH0m) and entropy change (ΔS0m). The micellization process is achieved to be spontaneous based on the obtained negative ΔG0m values. The linearity of the ΔHmo and ΔSmo values is excellent. The intrinsic enthalpy gain (ΔH0*m) and compensation temperature (Tc) were calculated and discussed with logical points. Interactions of polymer hydrophobic chains or the polymer + surfactant associated with amphiphilic surface-active drugs can employ a strong impact on the behavior of the gels.

Spontaneous Formation of Stable Vesicles and Vesicle Gels in Polar Organic Solvents

The self-assembly of lipids into nanoscale vesicles (liposomes) is routinely accomplished in water. However, reports of similar vesicles in polar organic solvents like glycerol, formamide, and ethylene glycol (EG) are scarce. Here, we demonstrate the formation of nanoscale vesicles in glycerol, formamide, and EG using the common phospholipid lecithin (derived from soy). The samples we study are simple binary mixtures of lecithin and the solvent, with no additional cosurfactants or salt. Lecithin dissolves readily in the solvents and spontaneously gives rise to viscous fluids at low lipid concentrations (∼2-4%), with structures ∼200 nm detected by dynamic light scattering. At higher concentrations (>10%), lecithin forms clear gels that are strongly birefringent at rest. Dynamic rheology confirms the elastic response of gels, with their elastic modulus being ∼20 Pa at ∼10% lipid. Images from cryo-scanning electron microscopy (cryo-SEM) indicate that concentrated samples are "vesicle gels," where multilamellar vesicles (MLVs, also called "onions"), with diameters between 50 and 600 nm, are close-packed across the sample volume. This structure can explain both the elastic rheology as well as the static birefringence of the samples. The discovery of vesicles and vesicle gels in polar solvents widens the scope of systems that can be created by self-assembly. Interestingly, it is much easier to form vesicles in polar solvents than in water, and the former are stable indefinitely, whereas the latter tend to aggregate or coalesce over time. The stability is attributed to refractive index-matching between lipid bilayers and the solvents, i.e., these vesicles are relatively "invisible" and thus experience only weak attractions. The ability to use lipids (which are "green" or eco-friendly molecules derived from renewable natural sources) to thicken and form gels in polar solvents could also prove useful in a variety of areas, including cosmetics, pharmaceuticals, and lubricants.

How Do Amphiphilic Biopolymers Gel Blood? An Investigation Using Optical Microscopy

Amphiphilic biopolymers such as hydrophobically modified chitosan (hmC) have been shown to convert liquid blood into elastic gels. This interesting property could make hmC useful as a hemostatic agent in treating severe bleeding. The mechanism for blood gelling by hmC is believed to involve polymer-cell self-assembly, i.e., insertion of hydrophobic side chains from the polymer into the lipid bilayers of blood cells, thereby creating a network of cells bridged by hmC. Here, we probe the above mechanism by studying dilute mixtures of blood cells and hmC in situ using optical microscopy. Our results show that the presence of hydrophobic side chains on hmC induces significant clustering of blood cells. The extent of clustering is quantified from the images in terms of the area occupied by the 10 largest clusters. Clustering increases as the fraction of hydrophobic side chains increases; conversely, clustering is negligible in the case of the parent chitosan that lacks hydrophobes. Moreover, the longer the hydrophobic side chains, the greater the clustering (i.e., C₁₂ > C₁₀ > C₈ > C₆). Clustering is negligible at low hmC concentrations but becomes substantial above a certain threshold. Finally, clustering due to hmC can be reversed by adding the supramolecule α-cyclodextrin, which is known to capture hydrophobes in its binding pocket. Overall, the results from this work are broadly consistent with the earlier mechanism, albeit with a few modifications.

Colloid Chemistry

n/a