Chemical stimuli-responsive supramolecular hydrogel from amphiphilic tris-urea

Harnessing Glycolipids for Supramolecular Gelation: A Contemporary Review

Within the scope of this review, our exploration spans diverse facets of amphiphilic glycolipid-based low-molecular-weight gelators (LMWGs). This journey explores glycolipid synthesis, self-assembly, and gelation with tailorable properties. It begins by examining the design of glycolipids and their influence on gel formation. Following this, a brief exploration of several gel characterization techniques adds another layer to the understanding of these materials. The final section is dedicated to unraveling the various applications of these glycolipid-based supramolecular gels. A meticulous analysis of available glycolipid gelators and their correlations with desired properties for distinct applications is a pivotal aspect of their investigation. As of the present moment, there exists a notable absence of a review dedicated exclusively to glycolipid gelators. This study aims to bridge this critical gap by presenting an overview that provides novel insights into their unique properties and versatile applications. This holistic examination seeks to contribute to a deeper understanding of molecular design, structural characteristics, and functional applications of glycolipid gelators by offering insights that can propel advancements in these converging scientific disciplines. Overall, this review highlights the diverse classifications of glycolipid-derived gelators and particularly emphasizes their capacity to form gels.

Bolaamphiphile-based supramolecular gels with drugs eliciting membrane effects

Supramolecular chemistry has garnered important interest in recent years toward improving therapeutic efficacy via drug delivery approaches. Although self-assemblies have been deeply investigated, the design of novel drugs leveraging supramolecular chemistry is less known. In this contribution, we show that a Low Molecular Weight Gel (LMWG) can elicit cancer cell apoptosis. This biological effect results from the unique supramolecular properties of a bolaamphiphile-based gelator, which allow for strong interaction with the lipid membrane. This novel supramolecular-drug paradigm opens up new possibilities for therapeutic applications targeting membrane lipids.

Synthesis and Self-Assembly Properties of Bola-Amphiphilic Glycosylated Lipopeptide-Type Supramolecular Hydrogels Showing Colour Changes Along with Gel-Sol Transition

Supramolecular hydrogels formed by self-assembly of low-molecular-weight amphiphiles (hydrogelators) have attracted significant attention, as smart and soft materials. However, most of the observed stimuli-responsive behaviour of these supramolecular hydrogels are limited to gel-sol transitions. In this study, we present bola-amphiphilic glycosylated lipopeptide-type supramolecular hydrogelators that exhibit reversible thermochromism along with a gel-sol transition. The bola-amphiphiles have mono-, di-, tri- or tetra-phenylalanine (F) as a short peptide moiety. We investigate and discuss the effects of the number of F residues on the gelation ability and the morphology of the self-assembled nanostructures.

Structural diversification of bola-amphiphilic glycolipid-type supramolecular hydrogelators exhibiting colour changes along with the gel-sol transition

We diversified the structures of bola-amphiphilic glycolipid-type supramolecular hydrogelators that exhibited reversible thermochromism along with a gel-sol transition. The hydrogelators were designed and synthesized to have homo- or hetero-saccharides on each end of their molecules. Herein, the effects of the saccharides' structure on the gelation ability are discussed.

Ionic Diffusion and Drug Release Behavior of Core-Shell-Functionalized Alginate-Chitosan-Based Hydrogel

This paper reports the core-shell structure effects in calcium alginate (CaALG) microbeads due to the threshold water level for phase transition and correlates these properties with respect to pH and electrical conductivity. Further, in this study, we used a novel microfluidic device for drug release testing to study the programmed release of risedronate (RIS-anti-osteoporotic drug) encapsulated in pH-responsive CaALG-chitosan (CHT) microbeads. Our microfluidic device contains a single straight microchannel containing a steplike barrier design used to restrict the mobility of the microbeads at the sample detection zone. For optical and fluorescence microscopy, single fluorescently labeled CaALG-CHT microbead containing RIS was placed in the sample detection zone by flowing through the inlet port with ultrapure water. The RIS release behavior from the microbeads at different pH (2.1, 4, 6.8, and 7.4) conditions was determined by using a spectrophotometer connected to the outlet port of the device. Results of our first study showed that the decrease in the concentration of CaCl₂ increases the swelling rate in CaALG microbeads. Maximum swelling was achieved with the lowest molar concentration of CaCl₂ used for fabrication of CaALG microbeads. Further, electrical current-voltage characteristic shows the nature of ionic mobility with respect to varying levels of pH indicating electrokinetic forces developed in the CaALG microbeads. By using a microfluidic device for drug release testing, we demonstrated that a sustained release delivery system for RIS can be prepared by coating with pH-sensitive and biodegradable CaALG-CHT. The CaALG-CHT microbeads used for encapsulating RIS are resistant to the acidic environment of the stomach. This may improve the therapeutic effectiveness and reduce the gastric adverse effects associated with RIS by preventing its decomposition in the acidic condition of stomach. The newly developed microfluidic device for drug release testing may find applications in screening novel drugs and delivery systems.

The effect of carbohydrate structures on the hydrogelation ability and morphology of self-assembled structures of peptide-carbohydrate conjugates in water

We describe the construction of peptide-carbohydrate conjugates, namely glycopeptides, capable of self-assembling in water. We found that disaccharide structures (epimer or glycosidic-bond geometry) appended to the glycopeptides have a noticeable effect on the hydrogel formation ability as well as the morphology of the self-assembled structures. The soft materials consisting of self-assembled structures with carbohydrates on their surface and various types of morphologies might be useful as matrices to investigate the function of carbohydrates in biological events.

Morphology-Variable Aggregates Prepared from Cholesterol-Containing Amphiphilic Glycopolymers: Their Protein Recognition/Adsorption and Drug Delivery Applications

In this study, a series of diblock glycopolymers, poly(6-O-methacryloyl-d-galactopyranose)-b-poly(6-cholesteryloxyhexyl methacrylate) (PMAgala-b-PMAChols), with cholesterol/galactose grafts were prepared through a sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and deprotection process. The glycopolymers could self-assemble into aggregates with various morphologies depending on cholesterol/galactose-containing block weight ratios, as determined by transmission electronic microscopy (TEM) and dynamic laser light scattering (DLS). In addition, the lectin (Ricinus communis agglutinin II, RCA120) recognition and bovine serum albumin (BSA) adsorption of the PMAgala-b-PMAChol aggregates were evaluated. The SK-Hep-1 tumor cell inhibition properties of the PMAgala-b-PMAChol/doxorubicin (DOX) complex aggregates were further examined in vitro. Results indicate that the PMAgala-b-PMAChol aggregates with various morphologies showed different interaction/recognition features with RCA120 and BSA. Spherical aggregates (d ≈ 92 nm) possessed the highest RCA120 recognition ability and lowest BSA protein adsorption. In addition, the DOX-loaded spherical complex aggregates exhibited a better tumor cell inhibition property than those of nanofibrous complex aggregates. The morphology-variable aggregates derived from the amphiphilic glycopolymers may serve as multifunctional biomaterials with biomolecular recognition and drug delivery features.

Pyridine/pyridinium symmetrical bisamides as functional materials: aggregation, selective sensing and drug release

We report the design, synthesis and gelation behavior of some 3-amino pyridine/pyridinium-based bisamides. As an application, gels are useful in the visual detection of cations, anions, biomolecules and in drug release.

Non-invasive strategies for targeting the posterior segment of eye

The safe and effective treatment of eye diseases has been remained a global myth. Several advancements have been done and various drug delivery and treatment techniques have been suggested. The Posterior segment disorders are the leading cause of visual impairments and blindness. Targeting the therapeutic agents to the anterior and posterior segments of the eye has attracted extensive attention from the scientific community. Significant key factors in the success of ocular therapy are the development of safe, effective, economic and non-invasive novel drug delivery systems. These specialized non-invasive ocular drug delivery systems revolutionized the drug delivery strategies by overcoming the limitations, provided targeted delivery to the ocular tissues by avoiding larger doses, and reducing the toxicity encountered by the conventional approaches. These non-invasive systems are fabricated by ingredients encompassing biodegradability, biocompatibility, mucoadhesion, solubility and permeability enhancement and stimuli responsiveness. The variety of routes are utilized to provide minimally invasive drug delivery to the patients without any discomfort and pain. This review is focused on the brief introduction, types, significance, preparation techniques, components and mechanism of drug release of non-invasive systems, including in situ gelling systems, microspheres, iontophoresis, nanoparticles, nanosuspensions and specialized novel emulsions.

Amino Acids and Peptide-Based Supramolecular Hydrogels for Three-Dimensional Cell Culture

Supramolecular hydrogels assembled from amino acids and peptide-derived hydrogelators have shown great potential as biomimetic three-dimensional (3D) extracellular matrices because of their merits over conventional polymeric hydrogels, such as non-covalent or physical interactions, controllable self-assembly, and biocompatibility. These merits enable hydrogels to be made not only by using external stimuli, but also under physiological conditions by rationally designing gelator structures, as well as in situ encapsulation of cells into hydrogels for 3D culture. This review will assess current progress in the preparation of amino acids and peptide-based hydrogels under various kinds of external stimuli, and in situ encapsulation of cells into the hydrogels, with a focus on understanding the associations between their structures, properties, and functions during cell culture, and the remaining challenges in this field. The amino acids and peptide-based hydrogelators with rationally designed structures have promising applications in the fields of regenerative medicine, tissue engineering, and pre-clinical evaluation.

Chirality inversion, supramolecular hydrogelation and lectin binding of two thiolactose amphiphiles constructed on a di-lauroyl-l-tartaric acid scaffold

The supramolecular self-assembly mode of two diacyl-glycoamphiphiles depends on the length of the flexible achiral ethoxylated linker.

Regulating the Rate of Molecular Self-Assembly for Targeting Cancer Cells

Besides tight and specific ligand-receptor interactions, the rate regulation of the formation of molecular assemblies is one of fundamental features of cells. But the latter receives little exploration for developing anticancer therapeutics. Here we show that a simple molecular design of the substrates of phosphatases-tailoring the number of phosphates on peptidic substrates-is able to regulate the rate of molecular self-assembly of the enzyme reaction product. Such a rate regulation allows selective inhibition of osteosarcoma cells over hepatocytes, which promises to target cancer cells in a specific organ. Moreover, our result reveals that the direct measurement of the rate of the self-assembly in a cell-based assay provides precise assessment of the cell targeting capability of self-assembly. This work, as the first report establishing rate regulation of a multiple-step process to inhibit cells selectively, illustrates a fundamentally new approach for controlling the fate of cells.

Supramolecular Hydrogelators and Hydrogels: From Soft Matter to Molecular Biomaterials

In this review we intend to provide a relatively comprehensive summary of the work of supramolecular hydrogelators after 2004 and to put emphasis particularly on the applications of supramolecular hydrogels/hydrogelators as molecular biomaterials. After a brief introduction of methods for generating supramolecular hydrogels, we discuss supramolecular hydrogelators on the basis of their categories, such as small organic molecules, coordination complexes, peptides, nucleobases, and saccharides. Following molecular design, we focus on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators. Particularly, we discuss the applications of supramolecular hydrogelators after they form supramolecular assemblies but prior to reaching the critical gelation concentration because this subject is less explored but may hold equally great promise for helping address fundamental questions about the mechanisms or the consequences of the self-assembly of molecules, including low molecular weight ones. Finally, we provide a perspective on supramolecular hydrogelators. We hope that this review will serve as an updated introduction and reference for researchers who are interested in exploring supramolecular hydrogelators as molecular biomaterials for addressing the societal needs at various frontiers.

Multifarious facets of sugar-derived molecular gels: molecular features, mechanisms of self-assembly and emerging applications

The remarkable capability of nature to design and create excellent self-assembled nano-structures, especially in the biological world, has motivated chemists to mimic such systems with synthetic molecular and supramolecular systems. The hierarchically organized self-assembly of low molecular weight gelators (LMWGs) based on non-covalent interactions has been proven to be a useful tool in the development of well-defined nanostructures. Among these, the self-assembly of sugar-derived LMWGs has received immense attention because of their propensity to furnish biocompatible, hierarchical, supramolecular architectures that are macroscopically expressed in gel formation. This review sheds light on various aspects of sugar-derived LMWGs, uncovering their mechanisms of gelation, structural analysis, and tailorable properties, and their diverse applications such as stimuli-responsiveness, sensing, self-healing, environmental problems, and nano and biomaterials synthesis.

Supramolecular hydrogels based on bola-amphiphilic glycolipids showing color change in response to glycosidases

We developed supramolecular hydrogels exhibiting reversible thermochromism concurrently with gel-to-sol transition from four glycolipids. In addition, these gels showed the similar color change in response to glycosidases, which can be employed to construct a colorimetric sensor array chip for sensing glycosidases with the naked eye.

Separation of proteins using supramolecular gel electrophoresis

An amphiphilic low-molecular-weight hydrogelator 1 was synthesized. A tris-glycine-SDS solution gel of 1 was applied for electrophoresis to separate proteins. Centrifugation of a mixture of protein and a hydrogel of 1 enabled the recovery of protein. Various combinations of proteins were applied for supramolecular gel electrophoresis (SUGE), and remarkably poor mobility for small proteins (<45 kDa) was found.