Molecular nanofibers of olsalazine form supramolecular hydrogels for reductive release of an anti-inflammatory agent

A facile strategy to generate polymeric nanoparticles for synergistic chemo-photodynamic therapy

Polymeric nanoparticles generated by mPEG-tetrakis(4-carboxyphenyl)porphyrin amphiphiles were used to trap doxorubicin for synergistic chemo-photodynamic therapy.

Controllable self-assemblies of sodium benzoate in different solvent environments

Sodium benzoate is an important and widely used food additive, however, it's self-assembly properties in diverse solvents have been rarely studied. Here, we systematically report its various self-assemblies in different solvents environments.

Supramolecular nanofibers of triamcinolone acetonide for uveitis therapy

Supramolecular nanofibers of prodrugs hold advantages for drug release due to their high drug payload, sustained and constant drug release behavior, and stimuli responsiveness. In this study, we report on a supramolecular hydrogel mainly formed by a clinically used drug triamcinolone acetonide (TA). Such a hydrogel could only be prepared via an ester bond hydrolysis process from its prodrug of succinated triamcinolone acetonide (STA). The resulting hydrogel could constantly release TA in the in vitro release experiment. The TA hydrogel possessed an excellent transscleral penetration ability, as evaluated by the in vitro transscleral transport study. The developed TA hydrogel also exhibited a great ocular compatibility in rats, as indicated by the optical coherence tomography (OCT) images, HE observation, and glial fibrillary acidic protein (GFAP) and vimentin immuno-staining assays of the retinas. Our TA hydrogel showed a decreased efficacy to inhibit ocular inflammation in the rat's experiment autoimmune uveitis (EAU) model compared to the commercial TA suspension (Transton), but without causing complications such as high intraocular pressure and cataracts. These promising properties of the hydrogel indicated its great potential for the treatment of eye diseases.

Exploiting supramolecular synthons in designing gelators derived from multiple drugs

A simple strategy for designing salt-based supramolecular gelators comprised of various nonsteroidal anti-inflammatory drugs (NSAIDs) and amantadine (AMN) (an antiviral drug) has been demonstrated using a supramolecular synthon approach. Single-crystal and powder X-ray diffraction established the existence of the well-studied gel-forming 1D supramolecular synthon, namely, primary ammonium monocarboxylate (PAM) synthon in all the salts. Remarkably five out of six salts were found to be capable of gelling methyl salicylate (MS)-an important ingredient in commercially available topical gels; one such selected biocompatible salt displayed an anti-inflammatory response in prostaglandin E2 (PGE2 ) assay, thereby indicating their plausible biomedical applications.

Glutathione-triggered formation of a Fmoc-protected short peptide-based supramolecular hydrogel

A biocompatible method of glutathione (GSH) catalyzed disulfide bond reduction was used to form Fmoc-short peptide-based supramolecular hydrogels. The hydrogels could form in both buffer solution and cell culture medium containing 10% of Fetal Bovine Serum (FBS) within minutes. The hydrogel was characterized by rheology, transmission electron microscopy, and fluorescence emission spectra. Their potential in three dimensional (3D) cell culture was evaluated and the results indicated that the gel with a low concentration of the peptide (0.1 wt%) was suitable for 3D cell culture of 3T3 cells. This study provides an alternative candidate of supramolecular hydrogel for 3D cell culture and cell delivery.

Activatable cell penetrating peptide-peptide nucleic acid conjugate via reduction of azobenzene PEG chains

The use of stimuli-responsive bioactive molecules is an attractive strategy to circumvent selectivity issues in vivo. Here, we report an activatable cell penetrating peptide (CPP) strategy ultimately aimed at delivering nucleic acid drugs to the colon mucosa using bacterial azoreductase as the local reconversion trigger. Through screening of a panel of CPPs, we identified a sequence (M918) capable of carrying a nucleic acid analogue payload. A modified M918 peptide conjugated to a peptide nucleic acid (PNA) was shown to silence luciferase in colon adenocarcinoma cells (HT-29-luc). Reversible functionalization of the conjugate's lysine residues via an azobenzene self-immolative linkage abolished transfection activity, and the free CPP-PNA was recovered after reduction of the azobenzene bond. This activatable CPP conjugate platform could find applications in the selective delivery of nucleic acid drugs to the colon mucosa, opening therapeutic avenues in colon diseases.

Multistimuli-responsive supramolecular gels: design rationale, recent advances, and perspectives

This manuscript presents a brief overview of recent advances in multistimuli-responsive supramolecular gels (MRSGs). The synthesis of MRSGs with faster and smarter responsive abilities to a variety of external stimuli, such as redox reagents, pH changes, ligands, and coupling reagents, is one key issue for the upgrade of current molecular motors, signal sensors, shape memory devices, drug delivery systems, display devices, and other devices. However, the design rules of MRSGs are still not well understood. The lack of information about the relationship between the spatial structure and gelation behavior of existing gelators means that the knowledge required to design new gelators by the addition of functional moieties to well-known gelators is lacking. Insights into the gelation pathway of known gelators may bring inspiration to researchers who want to exploit elegant designs and specific building blocks to obtain their own MRSGs with predictable stimuli-responsive abilities.

(-)-Menthol based thixotropic hydrogel and its application as a universal antibacterial carrier

A kind of novel hydrogelator based on (-)-menthol, a traditional cooling compound, tailed by an amino acid derivate through an alkyl chain, has been designed and synthesized. The hydrogelator containing an l-lysine can form a stable hydrogel with thixotropic character in a large pH range. An interesting feature is that the viscoelastic character of the hydrogel can be enhanced by mechanical force. The mechanism of the self-assembly process was investigated by means of IR, SEM, AFM and X-ray diffraction. The formation of three dimensional multiporous networks through acid base interactions and strong double hydrogen bonding between amino acids is proposed to be the driving force for the construction of the stable hydrogel. As a result, the hydrogelator can further gelate aqueous solutions of some confirmed antibacterial agents such as Zn(2+) and a series of water soluble organic antibiotic medicines like lincomycin, amoxicillin, etc., in such a unique way that the concentration of the antibacterial agents loaded into the hydrogel can be tuned to a large extent. The antimicrobial susceptibility of the hydrogels loaded with Zn(2+) or lincomycin is much more effective than that of the corresponding aqueous solution tested by the Oxford cup method. Furthermore, the hydrogelator is completely innoxious to living cells by measurement of MTT assay. Thus, the hydrogel can be developed as a universal carrier for antibacterial agents and may also be widely used in the fields of cell culture, tissue engineering, or drug delivery systems.

Manipulation of the gel behavior of biological surfactant sodium deoxycholate by amino acids

Supramolecular hydrogels were prepared in the mixtures of biological surfactant sodium deoxycholate (NaDC) and halide salts (NaCl and NaBr) in sodium phosphate buffer. It is very interesting that with the addition of two kinds of amino acids (L-lysine and L-arginine) to NaDC/NaX hydrogels, the gel becomes solution at room temperature. We characterized this performance through phase behavior observation, transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectra, and rheological measurements. The results demonstrate that the gels are formed by intertwined fibrils, which are induced by enormous cycles of NaDC molecules driven by comprehensive noncovalent interactions, especially the hydrogen bonds. Our conclusion is that the presence of halide salts (NaCl and NaBr) enhances the formation of the gels, while the addition of amino acids (L-lysine and L-arginine) could make the breakage of the hydrogen bonds and weaken the formation of the gels. Moreover, its fast disassembly in the presence of amino acids allows for the release of substances (i.e., the dye methylene blue) entrapped within the gel network. The tunable gel morphology, microstructure, mechanical strength, and anisotropy verify the role of halide salts and amino acids in altering the properties of the gels, which can probably be exploited for a variety of applications in future.

Gemcitabine induced supramolecular hydrogelations of aldehyde-containing short peptides

Supramolecular hydrogels can be formed by the addition of gemcitabine to aldehyde-containing peptides.

An ultrasensitive colorimetric aptasensor for ATP based on peptide/Au nanocomposites and hemin–G-quadruplex DNAzyme

A self-assembled peptide nanosphere was firstly applied to construct biosensors. A new signal amplification strategy was proposed for colorimetric aptasensor based on PNS/AuNPs composite. The colorimetric aptasensor displayed an ultra-high sensitivity for ATP detection with a LOD of 1.35 pM.

A supramolecular polymer gel with dual-responsiveness constructed by crown ether based molecular recognition

A supramolecular polymer gel was prepared from self-assembly of a heteroditopic A–B monomer based on benzo[18]crown-6. Such a gel shows interesting gel–sol transitions in response to dual-stimuli owing to the dynamically reversible complexation between benzo[18]crown-6 and primary alkylammonium salt moieties.

Short peptide based self-assembled nanostructures: implications in drug delivery and tissue engineering

Self-assembling peptides with many potential biomedical applications.

Recovery and redispersion of gold nanoparticles using the self-assembly of a pH sensitive zwitterionic amphiphile

The pH-responsive self-assembly of a zwitterionic amphiphile was expanded to the recovery of gold (Au) nanoparticles. Multilayered lamellae were incorporated into the nanoparticles. Redispersion of nanoparticles was achieved by the transition of self-assembly based on pH.

Charge-transfer interaction mediated organogels from 18β-glycyrrhetinic acid appended pyrene

We describe herein the two-component charge-transfer (CT) interaction induced organogel formation with 18β-glycyrrhetinic acid appended pyrene (GA-pyrene, 3) as the donor, and 2,4,7-trinitrofluorenone (TNF, 4) as the acceptor. The use of TNF (4) as a versatile electron acceptor in the formation of CT gels is demonstrated through the formation of gels in a variety of solvents. Thermal stability, stoichiometry, scanning electron microscopy (SEM), optical micrographs, and circular dichroism (CD) are performed on these CT gels to investigate their thermal and assembly properties. UV–vis, fluorescence, mass spectrometric as well as variable-temperature ¹H NMR experiments on these gels suggest that the CT interaction is one of the major driving forces for the formation of these organogels.

β-Amino acid and amino-alcohol conjugation of a nonsteroidal anti-inflammatory drug (NSAID) imparts hydrogelation displaying remarkable biostability, biocompatibility, and anti-inflammatory properties

A well-known nonsteroidal anti-inflammatory drug (NSAID), namely, naproxen (Np), was conjugated with β-alanine and various combinations of amino alcohols and l-alanine. Quite a few bioconjugates, thus synthesized, were capable of gelling pure water, NaCl solution (0.9 wt %), and phosphate-buffered saline (PBS) (pH 7.4). The hydrogels were characterized by rheology and electron microscopy. Hydrogelation was probed by FT-IR and temperature-variable (1)H NMR studies. Single-crystal X-ray diffraction (SXRD) of a nonhydrogelator and a hydrogelator in the series established a useful structure-property (gelation) correlation. MTT assay of the hydrogelators in the mouse macrophage RAW 264.7 cell line showed excellent biocompatibility. The prostaglandin E2 (PGE2) assay of the hydrogelators revealed their anti-inflammatory response, which was comparable to that of the parent NSAID naproxen sodium (Ns).

Supramolecular nanostructures formed by anticancer drug assembly

We report here a supramolecular strategy to directly assemble the small molecular hydrophobic anticancer drug camptothecin (CPT) into discrete, stable, well-defined nanostructures with a high and quantitative drug loading. Depending on the number of CPTs in the molecular design, the resulting nanostructures can be either nanofibers or nanotubes, and have a fixed CPT loading content ranging from 23% to 38%. We found that formation of nanostructures provides protection for both the CPT drug and the biodegradable linker from the external environment and thus offers a mechanism for controlled release of CPT. Under tumor-relevant conditions, these drug nanostructures can release the bioactive form of CPT and show in vitro efficacy against a number of cancer cell lines. This strategy can be extended to construct nanostructures of other types of anticancer drugs and thus presents new opportunities for the development of self-delivering drugs for cancer therapeutics.

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.

Introducing D-amino acid or simple glycoside into small peptides to enable supramolecular hydrogelators to resist proteolysis

Here we report the examination of two convenient strategies, the use of a d-amino acid residue or a glycoside segment, for increasing the proteolytic resistance of supramolecular hydrogelators based on small peptides. Our results show that the introduction of d-amino acid or glycoside to the peptides significantly increases the resistance of the hydrogelators against proteinase K, a powerful endopeptidase. The insertion of d-amino acid in the peptide backbone, however, results relatively low storage moduli of the hydrogels, likely due to the disruption of the superstructures of the molecular assembly. In contrast, the introduction of a glycoside to the C-terminal of peptide enhances the biostability of the hydrogelators without the significant decrease of the storage moduli of the hydrogels. This work suggests that the inclusion of a simple glycogen in hydrogelators is a useful approach to increase their biostability, and the gained understanding from the work may ultimately lead to development of hydrogels of functional peptides for biomedical applications that require long-term biostability.

A self-assembled delivery platform with post-production tunable release rate

Self-assembly of three molecular components results in a delivery platform, the release rate of which can be tuned after its production. A fluorophore-conjugated gelator can be hydrolyzed by an enzyme, resulting in the release of a fluorescent small molecule. To allow the release to be tunable, the enzyme is entrapped in liposomes and can be liberated by heating the system for a short period. Crucially, the heating time determines the amount of enzyme liberated; with that, the release rate can be tuned by the time of heating.

A general method for detecting protease activity via gelation and its application to artificial clotting

A modular system for detecting protease activity via enzyme-triggered gel formation is described. Protease-specific recognition sequences are utilized to achieve enzyme specificity. Artificial blood clotting is demonstrated by activating endogenous thrombin to trigger gelation in fibrinogen-deficient blood plasma.

Stimuli-responsive supramolecular polymeric materials

Supramolecular materials, dynamic materials by nature, are defined as materials whose components are bridged via reversible connections and undergo spontaneous and continuous assembly/disassembly processes under specific conditions. On account of the dynamic and reversible nature of noncovalent interactions, supramolecular polymers have the ability to adapt to their environment and possess a wide range of intriguing properties, such as degradability, shape-memory, and self-healing, making them unique candidates for supramolecular materials. In this critical review, we address recent developments in supramolecular polymeric materials, which can respond to appropriate external stimuli at the fundamental level due to the existence of noncovalent interactions of the building blocks.

A multiresponsive, shape-persistent, and elastic supramolecular polymer network gel constructed by orthogonal self-assembly

A cross-linked supramolecular polymer network gel is designed and prepared, which shows reversible gel-sol transitions induced by changes in pH, temperature, cation concentration, and metal co-ordination. The gel pore size is controlled by the amount of cross-linker added to the system, and the material can be molded into shape-persistent, free-standing objects with elastic behavior. These features are all due to the dynamically reversible host-guest complexation and good mechanical properties of the cross-linked polymer network. No single organogel has previously been reported to possess all of these features, making this supramolecular gel an unprecedentedly intelligent soft material.

Multifunctional, biocompatible supramolecular hydrogelators consist only of nucleobase, amino acid, and glycoside

The integration of nucleobase, amino acid, and glycoside into a single molecule results in a novel class of supramolecular hydrogelators, which not only exhibit biocompatibility and biostability but also facilitate the entry of nucleic acids into cytosol and nuclei of cells. This work illustrates a simple way to generate an unprecedented molecular architecture from the basic biological building blocks for the development of sophisticated soft nanomaterials, including supramolecular hydrogels.

Dissolution parameters reveal role of structure and solvent in molecular gelation

The relationship between thermodynamic dissolution parameters (enthalpy and entropy) and gelation ability was examined for two different classes of compounds in three different solvent systems. In total, 11 dipeptides and 19 pyridines were synthesized and screened for gelation in aqueous and organic solvents, respectively. The dissolution parameters were determined from the variable-temperature solubilities using the van't Hoff equation. These studies revealed that the majority of gelators had higher dissolution enthalpies and entropies compared to nongelators, consistent with the notion that gelators have stronger intermolecular interactions and more order in the solid state. The dissolution parameters were also found to be solvent-dependent, suggesting that solvent-solute interactions are also important in gelation. Overall, these results indicate that converting nongelators into gelators is attainable when structural modifications or a change in solvent lead to increases in the dissolution parameters.

Hydrogels for biomedical applications

Hydrogels are swollen, crosslinked networks that have great potential for use in biomedicine. Their softness, biocompatibility and ability for rapid diffusion of molecules make them useful for drug delivery, cell culture, wound healing and sensing applications. The chemical functionality of the gels can be easily modified to provide signalling and growth factors for cell proliferation. To allow the ingress of large cells, either porosity of the substrate can be controlled, or the gel can be made biodegradable. One ultimate goal is the growth of entire organs in the laboratory for eventual transplantation. Gels can be used as drug-delivery vehicles, either as implantable depots, or as microgels in blood-based delivery systems. One expanding area is the use of gels as surgical aides to prevent bleeding, infection and post-operative complications.