Search Results (25)

Cosmetic formulations are complex mixtures of ingredients that must fulfill several requirements. One of the challenges of the cosmetic industry is to find natural alternatives to replace synthetic polymers, preserving desirable sensory characteristics. The aim of this work is to induce the formation of gels, by replacing synthetic polymers with a low-molecular-weight gelator (LMWG), a small molecule able to self-assemble and form supramolecular networks. The impact of low-molecular-weight gelators on the environment is reduced as they are highly biodegradable. Thus, the behavior of solutions containing Boc-L-Dopa(Bn)₂-OH, an LMWG, together with ten different anionic surfactants, was studied to understand if the LMWG may act as a rheological modifier by increasing the viscosity of the formulation or forming gels with these ingredients. An amphoteric surfactant, cocamidopropyl betaine (CAPB), often used to increase cleansing gentleness, was also added to the solutions to better mimic a cosmetic formulation. In most cases, the addition of the gelator at only a 1% w/v concentration induces the gelification or an increase in the viscosity of the solutions, thus showing that this molecule is also able to self-assemble in complex mixtures. Full article

Gelling agents are critical for food texture and stability; usually, polymeric substances are employed. Low-molecular-weight gelators (LMWG) like phenylalanine (PHE) form supramolecular gels. However, food applications are limited due to amino acid derivatization or gelling solvent. This study characterizes PHE, water, and propylene glycol solutions and their gelling capability when cooled or stirred. Gelation is faster at higher stirring speeds. Gel strength increases if pH is near the PHE isoelectric point or at higher PHE concentrations, which increases gel transition temperature. Solutions develop browning in xylose (XYL) presence via first-order kinetics, accelerated by increasing PHE or xylose concentration. Full article

Self-assembled peptide-based hydrogels have attracted considerable interest from the research community. Particularly, low molecular weight gelators (LMWGs) consisting of amino acids and short peptides are highly suitable for biological applications owing to their facile synthesis and scalability, as well as their biocompatibility, biodegradability, and stability in physiological conditions. However, challenges in understanding the structure–property relationship and lack of design rules hinder the development of new gelators with the required properties for several applications. Hereby, in the plethora of peptide-based gelators, this review discusses the mechanical properties of single amino acid and dipeptide-based hydrogels. A mutual analysis of these systems allows us to highlight the relationship between the gel mechanical properties and amino acid sequence, preparation methods, or N capping groups. Additionally, recent advancements in the tuning of the gels’ rheological properties are reviewed. In this way, the present review aims to help bridge the knowledge gap between structure and mechanical properties, easing the selection or design of peptides with the required properties for biological applications. Full article

Chemiluminescence in solution-based systems has been extensively studied for the chemical analysis of biomolecules. However, investigations into the control of chemiluminescence reactions in gel-based systems, which offer flexibility in reaction conditions (such as the softness of the reaction environment), have only recently begun in polymer materials, with limited exploration in low-molecular-weight gelator (LMWG) systems. In this study, we investigated the chemiluminescence behaviors in the gel states using LMWG systems and evaluated their applicability to fluorescent-dye-containing molecular organogel systems/oxidant-containing aqueous systems. Using diethyl succinate organogels composed of 12-hydroxystearic acid as a molecular organogelator, we examined the fluorescent properties of various fluorescent dyes mixed with oxidant aqueous solutions. As the reaction medium transitioned from the solution to the gel state, the emission color and chemiluminescence duration changed significantly, and distinct characteristics were observed, for each dye. This result indicates that the chemiluminescence behavior differs significantly between the solution and gel states. Additionally, visual inspection and dynamic viscoelastic measurements of the mixed fluorescent dye-containing molecular gels and oxidant-containing aqueous solutions confirmed that the chemiluminescence induced by the mixing occurred within the gel phase. Furthermore, the transition from the solution to the gel state may allow for the modulation of the mixing degree, thereby enabling control over the progression of the chemiluminescence reaction. Full article

The combination of lyotropic liquid crystals (LLCs) and low-molecular-weight gelators (LMWGs) for the formation of lyotropic liquid crystal gels (LLC gels) leads to a versatile and complex material combining properties of both parent systems. We gelled the calamitic nematic N_C phases of a binary and ternary system using the LMWG 3,5-bis-(5-hexylcarbamoyl-pentoxy)-benzoic acid hexyl ester (BHPB-6). This binary system consists of the surfactant N,N-dimethyl-N-ethyl-1-hexadecylammonium bromide (CDEAB) and water, whereas the ternary system consists of the surfactant N,N,N-trimethyl-N-tetradecylammonium bromide (C₁₄TAB), the cosurfactant n-decanol, and water. Though containing similar surfactants, the gelled N_C phases of the binary and ternary systems show differences in their visual and gel properties. The gelled N_C phase of the binary system remains clear for several days after preparation, whereas the gelled N_C phase of the ternary system turns turbid within 24 h. We investigated the time evolution of the gel strength with oscillation rheology measurements (a) within the first 24 h and (b) up to two weeks after gel formation. The shape of the fibers was investigated over different time scales with freeze fracture electron microscopy (FFEM). We demonstrate that despite their similarities, the two LLC gels also have distinct differences. Full article

Traditional cleaning methods for removing undesired substances from artworks often involve the use of toxic volatile solvents, raising concerns about human health and environmental impact. Over time, various cleaning systems, such as thickeners, rigid, peelable, and nanostructured gels, have been introduced in the conservation sector to minimize solvent use and toxicity. However, these methods are primarily tailored for aqueous solutions or medium-to-high-polar solvents, leaving sustainable organogels for low-polar solvents largely unexplored. This paper explores the application of Low-Molecular-Weight Gelators (LMWGs) in the field of cultural heritage conservation, focusing on their potential to gel low-polar organic solvents. LMWGs, including cholesterol derivatives, fatty acid-derived compounds, anthryl, anthraquinone, amino acid, and saccharide-based organogelators, offer biocompatible and cost-effective options by forming supramolecular gels that immobilize solvents and reduce their release into the environment. This study highlights the need to transition from traditional, often toxic, solvents to greener and more sustainable cleaning systems by emphasizing LMWGs’ biodegradability, biocompatibility, and sustainability. While challenges such as optimizing gel properties and ensuring compatibility with artwork surfaces still need to be addressed, LMWGs hold promise as organogelators in conservation practice. Further research into LMWGs should focus on their optimization for conservation applications by adjusting their rheological properties and physico-chemical stability. Full article

Herein, the problem concerning the poorer mechanical properties of gels based on low molecular weight gelators (LMWGs)—L-cysteine and silver nitrate—was solved by the addition of various polymers—polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG)—to the initial cysteine–silver sol (CSS). The physicochemical methods of analysis—viscosimetry, UV spectroscopy, DLS, and SEM—identified that cysteine–silver hydrogels (CSG) based on PVA possess the best rheological properties and porous microstructure (the average pore size is 2–10 µm) compared to gels without the polymer or with PVP or PEG. Such gels are able to form cysteine–silver cryogels (CSC) and then porous cysteine–silver films (CSF) with an average pore size of 10–20 µm and good mechanical, swelling, and adhesion to skin characteristics as long as the structure of CSS particles remains stable. In vitro experiments have shown that hydrogels are non-toxic to normal human fibroblast cells. The obtained materials could potentially be applied to regenerative medicine. Full article

Low-molecular-weight gelators (LMWGs) are compounds with an intrinsic tendency to self-assemble forming various supramolecular architectures via non-covalent interactions. Considering that the development of supramolecular assemblies through the synergy of molecules is not entirely understood at the molecular level, this study introduced a Fmoc-short peptide and four Fmoc-amino acids as building blocks for the self-assembly/co-assembly process. Hence, we investigated the formation of supramolecular gels starting from the molecular aggregation following two triggering approaches: solvent/co-solvent method and pH switch. The complex morphological analysis (POM, AFM, and STEM) offered an insight into the spontaneous formation of well-ordered nanoaggregates. Briefly, POM and AFM images demonstrated that self-assembled gels present various morphologies like dendrimer, spherulite, and vesicle, whereas all co-assembled supramolecular systems exhibit fibrillar morphologies as a result of the interaction between co-partners of each system. STEM study has confirmed that the molecules interact and join together, finally forming a fibrous network, an aspect seen in both self-assembled and co-assembled gels. XRD allowed the determination of the molecular arrangement. The study emphasized that the Fmoc motif protected the amino groups and facilitated gelation through additional π-π interactions. Full article

Carbohydrate-based low molecular weight gelators (LMWGs) are compounds with the capability to self-assemble into complex molecular networks within a solvent, leading to solvent immobilization. This process of gel formation depends on noncovalent interactions, including Van der Waals, hydrogen bonding, and π–π stacking. Due to their potential applications in environmental remediation, drug delivery, and tissue engineering, these molecules have emerged as an important area of research. In particular, various 4,6-O-benzylidene acetal-protected D-glucosamine derivatives have shown promising gelation abilities. In this study, a series of C-2-carbamate derivatives containing a para-methoxy benzylidene acetal functional group were synthesized and characterized. These compounds exhibited good gelation properties in several organic solvents and aqueous mixtures. Upon removal of the acetal functional group under acidic conditions, a number of deprotected free sugar derivatives were also synthesized. Analysis of these free sugar derivatives revealed two compounds were hydrogelators while their precursors did not form hydrogels. For those protected carbamates that are hydrogelators, removal of the 4,6-protection will result in a more water-soluble compound that produces a transition from gel to solution. Given the ability of these compounds to form gels from solution or solution from gels in situ in response to acidic environments, these compounds may have practical applications as stimuli-responsive gelators in an aqueous medium. In turn, one hydrogelator was studied for the encapsulation and release of naproxen and chloroquine. The hydrogel exhibited sustained drug release over a period of several days, with the release of chloroquine being faster at lower pH due to the acid lability of the gelator molecule. The synthesis, characterization, gelation properties, and studies on drug diffusion are discussed. Full article

The Hansen solubility parameter (HSP) is a useful index for reasoning the gelation behavior of low-molecular-weight gelators (LMWGs). However, the conventional HSP-based methods only “classify” solvents that can and cannot form gels and require many trials to achieve this. For engineering purposes, quantitative estimation of gel properties using the HSP is highly desired. In this study, we measured critical gelation concentrations based on three distinct definitions, mechanical strength, and light transmittance of organogels prepared with 12-hydroxystearic acid (12HSA) and correlated them with the HSP of solvents. The results demonstrated that the mechanical strength, in particular, strongly correlated with the distance of 12HSA and solvent in the HSP space. Additionally, the results indicated that the constant volume-based concentration should be used when comparing the properties of organogels to a different solvent. These findings are helpful in efficiently determining the gelation sphere of new LMWGs in HSP space and contribute to designing organogels with tunable physical properties. Full article

One of the methods of obtaining supramolecular gels consists of the possibility of self-assembly of low molecular weight gelators (LMWGs). However, LMWG-based gels are often difficult to handle, easy to destroy and have poor rheological performance. In order to improve the gels’ properties, the LMWGs molecules are co-assembled, which induces more cross-links with more stable structures. Starting from these aspects, the present study refers to the preparation of a bionic hydrogel stabilized with a physiologically occurring, bifunctional biomolecule, L-lysine, co-assembled with other amino acids or peptides (such as a modified amino acid (Fmoc-serine or Fmoc-glutamic acid) or a tripeptide (Fmoc-Gly-Gly-Gly)) with the potential to support the repair of injuries or the age-related impaired structures or functions of living tissues. The introduction of a copartner aims to improve hydrogel characteristics from a morphological, rheological and structural point of view. On the other hand, the process will allow the understanding of the phenomenon of specific self-association and molecular recognition. Various characterization techniques were used to assess the ability to co-assemble: DLS, FT-IR, SEM and fluorescence microscopy, rheology and thermal analysis. Studies have confirmed that the supramolecular structure occurs through the formation of inter- and intramolecular physical bonds that ensure the formation of fibrils organized into 3D networks. The rheological data, namely the G′ > G″ and tan δ approximately 0.1–0.2 gel-like behavior observed for all studied samples, demonstrate and sustain the appearance of the co-assembly processes and the ability of the samples to act as LMWG. From the studied systems, the Fmoc–Lys–Fmoc_ Fmoc–Glu sample presented the best rheological characteristics that are consistent with the observations that resulted from the dichroism, fluorescence and SEM investigations. Full article

Three novel bis-urea fluorescent low-molecular-weight gelators (LMWGs) based on the tetraethyl diphenylmethane spacer—namely, L1, L2, and L3, bearing indole, dansyl, and quinoline units as fluorogenic fragments, respectively, are able to form gel in different solvents. L2 and L3 gel in apolar solvents such as chlorobenzene and nitrobenzene. Gelator L1 is able to gel in the polar solvent mixture DMSO/H₂O (H₂O 15% v/v). This allowed the study of gel formation in the presence of anions as a third component. An interesting anion-dependent gel formation was observed with fluoride and benzoate inhibiting the gelation process and H₂PO₄⁻, thus causing a delay of 24 h in the gel formation. The interaction of L1 with the anions in solution was clarified by ¹H-NMR titrations and the differences in the cooperativity of the two types of NH H-bond donor groups (one indole NH and two urea NHs) on L1 when binding BzO⁻ or H₂PO₄⁻ were taken into account to explain the inhibition of the gelation in the presence of BzO⁻. DFT calculations corroborate this hypothesis and, more importantly, demonstrate considering a trimeric model of the L1 gel that BzO⁻ favours its disruption into monomers inhibiting the gel formation. Full article

Venous malformation (VM), which causes severe damage to patients’ appearance and organ function, is one of the most common vascular malformations. At present, many drugs in clinical treatment cause various adverse reactions. Herein, we synthesized cationic amphiphilic gelators (TA6, TA8, and TA9) by introducing saturated carbon chains of different lengths to tranexamic acid (TA), which could self-assemble into low-molecular-weight gels (LMWGs) as drug delivery carriers by hydrogen bonds, van der Waals forces, and hydrophobic interactions. The rheological properties, gelation driving force and drug release profiles of TA6, TA8, and TA9 hydrogels were characterized, and the results indicated that the hydrogels prepared in this study possessed the typical characteristics of a gel and could release drugs slowly. More importantly, the TA9 gelator showed significant pharmacological activity, in that it served as both an active drug compound and a drug carrier. The in vitro experiments demonstrated that TA9 induced HUVECs death and hemolysis by destroying cell membranes in a dose-dependent manner, and caused cell death and hemolysis at a concentration of 0.09 µM/mL. Meanwhile, we found TA9 could interact not only with fibrinogen, but also with other endogenous molecules in the blood. After the administration of TA9 hydrogel for 15 days, macroscopic imaging and histological evaluation in mice and rabbits displayed obvious thrombi, inflammatory reactions, and venous embolization, indicating that the mechanism of the TA9 hydrogel in treating VM was involved in two processes. Firstly, the TA9 hydrogel relied on its mechanical strength to physically block veins and continuously release TA9, in situ, for targeted therapy. Then, TA9 destroyed endothelial cells and damaged venous walls critically, causing thrombi. Most excitingly, TA9 was hydrolyzed to TA by enzymes that inhibited the degradation of thrombi by plasmin to prolong the embolization time and to promote venous fibrosis. Compared with other clinically available sclerosants, the degradation of TA9 also empowered a better biocompatibility and biodegradability for the TA9 hydrogel. In conclusion, we synthesized a potentially safe and effective derivative of TA and developed a low-molecular-weight gel as a self-delivery system for TA in treating VM. Full article

Controlling the polymerization of supramolecular self-assembly through external stimuli holds great potential for the development of responsive soft materials and manipulation at the nanoscale. Vinyl esters of bis(leu or val)fumaramide (1a and 2a) have been found to be gelators of various organic solvents and were applied in this investigation of the influence of organogelators’ self-assembly on solid-state polymerization induced by gamma and ultraviolet irradiation. Here, we report our investigation into the influences of self-assemblies of bis(amino acid vinyl ester)fumaramides on gamma-ray- and ultraviolet-induced polymerization. The gelator molecules self-assembled by non-covalent interactions, mainly through hydrogen bonds between the amide group (CONH) and the carboxyl group (COO), thus forming a gel network. NMR and FTIR spectroscopy were used to investigate and characterize supramolecular gels. TEM and SEM microscopy were used to investigate the morphology of gels and polymers. Morphology studies showed that the gels contained a filamentous structure of nanometer dimensions that was exhaustive in a three-dimensional network. The prepared derivatives contained reactive alkyl groups suitable for carrying out the polymerization reaction initiated by gamma or ultraviolet radiation in the supramolecular aggregates of selected gels. It was found that the polymerization reaction occurred only in the network of the gel and was dependent on the structure of aggregates or the proximity and orientation of double bonds in the gel network. Polymers were formed by the gels exposure to gamma and ultraviolet radiation in toluene, and water/DMF gels with transcripts of their gel structure into polymers. The polymeric material was able to immobilize various solvents by swelling. Furthermore, methyl esters of bis(leu and val)fumaramide (1b and 2b) were synthesized; these compounds showed no gelling properties, and the crystal structure of the valine derivative 2b was determined. Full article

Low molecular weight gelators, LMWGs, are small molecules that can self-associate in organic solvents or in water to form fibrous supramolecular architectures and three-dimensional networks that present important applications in several fields. Although various strategies are known for the synthesis of these type of compounds, these are commonly hampered by the use of long multistep processes that include the protection and deprotection of functional groups. Therefore, it is essential to find direct and robust reactions that allow introducing the complexity and structural diversity necessary to obtain tailor-made functional materials in a simple and efficient way. A promising approach to this end is the use of multicomponent reactions. Based on our experience in this field, we report our studies aimed at the use of multicomponent reactions of isocyanides to prepare LMWGs. Full article