Unique Temperature-Dependent Supramolecular Self-Assembly: From Hierarchical 1D Nanostructures to Super Hydrogel

Copper-Induced Supramolecular Peptide Assemblies for Multi-Pathway Cell Death and Tumor Inhibition

Although self-assembly has emerged as an effective tool for fabricating biomaterials, achieving precise control over the morphologies and functionalities of the resultant assemblies remains an ongoing challenge. Inspired by the copper peptide naturally present in human plasma, in this study, we designed a synthetic precursor, FcGH. FcGH can self-assemble via two distinct pathways: spontaneous and Cu2+-induced. These two assembly pathways enabled the formation of assemblies with tunable morphologies by adjusting the amount of added Cu2+. We found that the nanoparticles formed by Cu2+-induced self-assembly exhibited a significantly higher cellular uptake efficiency than the wormlike fibers formed spontaneously. Moreover, this Cu2+-induced assembly process occurred spontaneously at a 1 : 1 molar ratio of Cu2+ to FcGH, avoiding the excessive use of Cu2+ and a tedious preparation procedure. By co-assembling with 10-hydroxycamptothecin (HCPT)-conjugated FcGH, Cu2+-induced supramolecular nanodrugs elicited multiple cell death modalities in cancer cells with elevated immunogenicity, enhancing the therapeutic effect compared to free HCPT. This study highlights Cu2+-induced self-assembly as an efficient tool for directing the assembly of nanodrugs and for synergistic tumor therapy.

Chiral fiber supramolecular hydrogels for tissue engineering

Tissue engineering (TE), as a new interdisciplinary discipline, aims to develop biological substitutes for repairing damaged tissues and organs. For the success of tissue regeneration, such biomaterials need to support the physiological activities of cells and allow the growth and maturation of tissues. Naturally, this regulation is achieved through the dynamic remodeling of the extracellular matrix (ECM) of cells. In recent years, chiral supramolecular hydrogels have shown higher application potential in the TE field than traditional polymer hydrogels due to their dynamic noncovalent interactions, adjustable self-assembly structure, and good biocompatibility. These advantages make it possible to construct hydrogels under physiological conditions with structure and function similar to those of the natural ECM. Meanwhile, the chiral characteristics of hydrogels play an important role in regulating cellular activities such as differentiation, adhesion, and proliferation, which is beneficial for tissue formation. In this review, a brief introduction is presented to highlight the importance of chiral fiber supramolecular hydrogels for TE at first. Afterward, the considerations for chiral supramolecular hydrogel design, as well as the influence of external stimuli on chiral hydrogel construction, are discussed. Finally, the potential application prospects of these materials in TE and the significant contribution made by our group in this field are summarized. This review not only helps to reveal the importance of chiral properties in TE but also provides new strategies for TE research based on chiral bionic microenvironments. This article is categorized under: Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Biology-Inspired Nanomaterials > Peptide-Based Structures Nanotechnology Approaches to Biology > Cells at the Nanoscale Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Injectable Anti-Inflammatory Supramolecular Nanofiber Hydrogel to Promote Anti-VEGF Therapy in Age-Related Macular Degeneration Treatment

Age-related macular degeneration (AMD) is a major cause of visual impairment and severe vision loss worldwide, while the currently available treatments are often unsatisfactory. Previous studies have demonstrated both inflammation and oxidative-stress-induced damage to the retinal pigment epithelium are involved in the pathogenesis of aberrant development of blood vessels in wet AMD (wet-AMD). Although antivascular endothelial growth factor (VEGF) therapy (e.g., Ranibizumab) can impair the growth of new blood vessels, side effects are still found with repeated monthly intravitreal injections. Here, an injectable antibody-loaded supramolecular nanofiber hydrogel is fabricated by simply mixing betamethasone phosphate (BetP), a clinic anti-inflammatory drug, anti-VEGF, the gold-standard anti-VEGF drug for AMD treatment, with CaCl₂ . Upon intravitreal injection, such BetP-based hydrogel (BetP-Gel), while enabling long-term sustained release of anti-VEGF to inhibit vascular proliferation in the retina and attenuate choroidal neovascularization, can also scavenge reactive oxygen species to reduce local inflammation. Remarkably, such BetP-Gel can dramatically prolong the effective treatment time of conventional anti-VEGF therapy. Notably, anti-VEGF-loaded supramolecular hydrogel based on all clinically approved agents may be readily translated into clinical use for AMD treatment, with the potential to replace the current anti-VEGF therapy.

Solvent-Driven Transformation of Zn/Cd2+-Deoxycholate Assemblies

Deoxycholic acid (DOC) is a unique, biologically derived surfactant with facial amphiphilicity that has been exploited, albeit minimally, in supramolecular assembly of materials. Here, we present the synthesis and structural characterization of three hybrid metal (Zn²⁺ and Cd²⁺)-DOC compounds. Analysis by single-crystal X-ray diffraction reveals the many interactions that are possible between these facial surfactants and the influence of solvent molecules that drive the assembly of materials. These structures are the first metal-DOC complexes besides those obtained from alkali and alkaline earth metals. We isolated polymeric chains of both Cd and Zn (Zn_poly-DOC and Cd_poly-DOC) from water. Major interactions between DOC molecules in these phases are hydrophobic in nature. Cd_poly-DOC exhibits unique P1 symmetry, with complete interdigitation of the amphiphiles between neighboring polymeric chains. Zn₄-DOC, obtained from methanol dissolution of Zn_poly-DOC, features the OZn₄ tetrahedron, widely known in basic zinc acetate and MOF-5 (metal organic framework). We document a solvent-driven, room-temperature transition between Zn_poly-DOC and Zn₄-DOC (in both directions) by scanning and transmission electron microscopies in addition to small-angle X-ray scattering, powder X-ray diffraction, and infrared spectroscopy. These studies show the methanol-driven transition of Zn_poly-DOC to Zn₄-DOC occurs via an intermediate with no long-range order of the Zn₄ clusters, indicating the strongest interactions driving assembly are intramolecular. On the contrary, water-driven solid-to-solid transformation from Zn₄-DOC to Zn_poly-DOC exhibits crystal-to-crystal transformation. Zn_poly-DOC is robust, easy to synthesize, and comprised of biologically benign components, so we demonstrate dye absorption as a proxy for water treatment applications. It favors absorption of positively charged dyes. These studies advance molecular level knowledge of the supramolecular assembly of facial surfactants that can be exploited in the design of organic-inorganic hybrid materials. This work also highlights the potential of solvent for tuning supramolecular assembly processes, leading to new hybrid materials featuring facial surfactants.

From helices to superhelices: hierarchical assembly of homochiral van der Waals 1D coordination polymers

Chiral transcription from the molecular level to the macroscopic level by self-organization has been a topic of considerable interest for mimicking biological systems. Homochiral coordination polymers (CPs) are intriguing systems that can be applied in the construction of artificial helical architectures, but they have scarcely been explored to date. Herein, we propose a new strategy for the generation of superhelices of 1D CPs by introducing flexible cyclohexyl groups on the side chains to simultaneously induce interchain van der Waals interactions and chain misalignment due to conformer interconversion. Superhelices of S- or R-Tb(cyampH)3·3H2O (S-1H, R-1H) [cyampH2 = S- or R-(1-cyclohexylethyl)aminomethylphosphonic acid] were obtained successfully, the formation of which was found to follow a new type of "chain-twist-growth" mechanism that had not been described previously. The design strategy used in this work may open a new and general route to the hierarchical assembly and synthesis of helical CP materials.

Stimulus-responsive luminescent hydrogels: Design and applications

Luminescent hydrogels are emerging soft materials with applications in photoelectric, biomedicine, sensors and actuators, which are fabricated via covalently conjugation of luminophors to hydrogelators or physical loading of luminescent organic/inorganic materials into hydrogel matrices. Due to the intrinsic stimulus-responsiveness for hydrogels such as thermo-, pH, ionic strength, light and redox, luminescent hydrogels could respond to external physical or chemical stimuli through varying the luminescent properties such as colors, fluorescent intensity and so on, affording diverse application potential in addition to the pristine individual hydrogels or luminescent materials. Based on the rapid development of such area, here we systematically summarize and discuss the design protocols, properties as well as the applications of stimulus-responsive luminescent hydrogels. Because of the stimuli-responsiveness, biocompatibility, injectable and controllability of luminescent hydrogels, they are widely used as functional smart materials. We illustrate the applications of luminescent hydrogels. The future developments about luminescent hydrogels are also presented.

Injectable Anti-inflammatory Nanofiber Hydrogel to Achieve Systemic Immunotherapy Post Local Administration

Despite the great promise achieved by immune checkpoint blockade (ICB) therapy in harnessing the immune system to combat different tumors, limitations such as low objective response rates and adverse effects remain to be resolved. Here, an anti-inflammatory nanofiber hydrogel self-assembled by steroid drugs is developed for local delivery of antiprogrammed cell death protein ligand 1 (αPDL1). Interestingly, on the one hand this carrier-free system based on steroid drugs can reprogram the pro-tumoral immunosuppressive tumor microenvironment (TME) to antitumoral TME; on the other hand, it would serve as a reservoir for sustained release of αPDL1 so as to synergistically boost the immune system. By local injection of such αPDL1-loaded hydrogel, effective therapeutic effects were observed in inhibiting both local tumors and abscopal tumors without any treatment. This work presents a unique hydrogel-based delivery system using clinically approved drugs, showing promise in improving the objective response rate of ICB therapy and minimizing its systemic toxicity.

A CO2-responsive smart fluid based on supramolecular assembly structures varying reversibly from vesicles to wormlike micelles

CO2-responsive smart fluids have been widely investigated in the past decade. In this article, we reported a CO2-responsive smart fluid based on supramolecular assembly structures varying from vesicles to wormlike micelles. Firstly, oleic acid and 3-dimethylaminopropylamine reacted to form a single-chain weak cationic surfactant with a tertiary amine head group, N-[3-(dimethylamino)propyl]oleamide (NDPO). Then, 1,3-dibromopropane was used as the spacer to react with NDPO to form a gemini cationic surfactant, trimethylene α,ω-bis(oleate amide propyl dimethyl ammonium bromide) (GCS). By controlling the feed ratio of 1,3-dibromopropane and NDPO, we found that the mixtures of GCS and NDPO with the molar ratio of 7 : 3 approximately could form vesicles in aqueous solution by supramolecular self-assembly. After bubbling CO2, the tertiary amine of NDPO was protonated. The packing parameter of the mixed surfactants reduced accordingly, accompanied by the transition of aggregates from vesicles to wormlike micelles. As a result, the zero-shear viscosity of the solution increased by more than four orders in magnitude. When the solid content of GCS/NPDO mixtures was higher than 5 wt% in solution, the sample treated by CO2 behaved as a gel over a wide frequency range with shear-thinning and self-healing properties. In addition, the sol-gel transition could be repeatedly and reversibly switched by cyclically bubbling CO2 and N2. Our effort may provide a new strategy for the design of CO2-responsive smart fluids, fostering their use in a range of applications such as in enhanced oil recovery.

pH-Dependent Chiral Recognition of D- and L-Arginine Derived Polyamidoamino Acids by Self-assembled Sodium Deoxycholate

D- and L-arginine-based polyamidoamino acids, called D- and L-ARGO7, retain the chirality and acid/base properties of the parent -amino acids and show pH-dependent self-structuring in water. The ability of the ARGO7 chiral isomers to selectively interact with chiral biomolecules and/or surfaces was studied by choosing sodium deoxycholate (NaDC) as a model chiral biomolecule for its ability to self-assembly into globular micelles, showing enantio-selectivity. To this purpose, mixtures of NaDC with D-, L- or D,L-ARGO7, respectively, in water were analysed by circular dichroism (CD) spectroscopy and small-angle neutron scattering (SANS) at different levels of acidity expressed in terms of pD and concentrations. Differences in the CD spectra indicated chiral discrimination for NaDC/ARGO7 mixtures in the gel phase (pD 7.30) but not in the solution phase (pD 9.06). SANS measurements confirmed large scale structural perturbation induced by this chiral discrimination in the gel phase yet no modulation of the structure in the solution phase. Together, these techniques shed light on the mechanism by which ARGO7 stereoisomers modify the morphology of NaDC micelles as a function of pH. This work demonstrates chirality-dependent interactions that drive structural evolution and phase behaviour of NaDC, opening the way for designing novel smart drug delivery systems.

Self-assembly of luminescent triblock bottlebrush copolymers in solution

Self-assembly presents bottom-up strategies for the construction of complex micelles from luminescent bottlebrush copolymers.

Steroidal supramolecular metallogels

Steroidal supramolecular metallogels combine the properties of steroids with metal ions resulting in multi-responsive systems possessing many potential applications.

A metalloprotein-inspired thermo-gene for thermogels

Coordinating hydrogels may act as a thermo-gene to endow heat-melting conventional hydrogels with superior thermal stability at temperatures over 80 °C.

Supramolecular Hydrogels with Properties Tunable by Calcium Ions: A Bio-Inspired Chemical System

Boc-L-DOPA(OBn)₂-OH is a simple synthetic molecule that promotes hydrogelation through electrostatic and π-π stacking interactions. Hydrogelation can occur in alkaline conditions by the use of triggers. Four hydrogels were prepared varying the base, NaOH or Na₂CO₃, and the trigger, GdL or CaCl₂. When the hydrogel formed in the presence of Na₂CO₃ and CaCl₂, the concomitant production of CaCO₃ crystals occurred, generating an organic/inorganic composite material. It was observed that the hydrogel once self-assembled preserved its status even if the trigger, the calcium ions, was removed. The viscoelastic behavior of the hydrogels was analyzed through rheological experiments, which showed a solid-like behavior of the hydrogels. The corresponding xerogels were analyzed mainly by scanning electron microscopy (SEM) and synchrotron X-ray diffraction analysis (XRD). They showed differences in structure, morphology, and fiber organization according to their source. This research presents a hydrogel system that can be applied as a soft biomaterial for tissue engineering, cosmetics, food, and environmental science. Moreover, it represents a model for biomineralization studies in which the hydrogel structure can act as an analogue of the insoluble matrix that confines the calcification site, provides Ca²⁺, and preserves its structure.

Luminescent Sodium Deoxycholate Ionogel Induced by Eu3+ in Ethylammonium Nitrate

Hydrogels based on bile salts and lanthanide ions have been reported for their easy gelation. However, the weak mechanical properties and water quenching to luminescence of lanthanide ions limit their applications in practice. Hence, a supramolecular ionogel has been prepared here through simply mixing of sodium deoxycholate and europium nitrate in a protic ionic liquid, ethylammonium nitrate (EAN). The prepared ionogel was characterized by scanning electron microscopy, X-ray energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, fluorescence spectroscopy, and rheological measurements. Such an ionogel resulted synergistically from metal coordination and hydrogen bonding. The effect of the solvent structure on gel properties was also explored by comparison with those formed in alkylammonium nitrates with longer chains. EAN was found to behave more effectively both as a solvent and a bridge to enhance the ionogel mechanical strength. The ionogels also exhibited better fluorescent properties than those of the corresponding hydrogels. The obtained results should expand the applications of lanthanide-containing luminescent soft materials in nonaqueous media. It is expected to apply in the fields of solid electrolytes, biosensors, and optics response.

Super metal hydrogels constructed from a simple tripodal gelator and rare earth metal ions and its application in highly selective and ultrasensitive detection of histidine

A series of stable super metal hydrogels (TP-Ms, M = Tb3+, Eu3+, La3+ and Ce3+) with a low critical gelation concentration (2.28 × 10-3 M, 0.1%) was successfully constructed by forming hierarchical assemblies of a tripodal gelator (TP) with rare earth metal ions (Tb3+, Eu3+, La3+ and Ce3+). Interestingly, the super metal hydrogels TP-Eu and TP-La show a specific and ultrasensitive response to histidine (His). The addition of a series of amino acids into the metal hydrogels TP-Eu and TP-La showed that only His could induce distinct fluorescent enhancement for TP-Eu and TP-La, while other amino acids did not significantly interfere with the His sensing process. The LODs of super metal-hydrogel TP-Eu and TP-La for His are (1.83-1.94) × 10-9 and (1.83-1.85) × 10-9 M, respectively. In addition, constructing super supramolecular metal hydrogels by hierarchical assemblies of an easily synthesized tripodal gelator and rare earth metal ions is a novel and efficient approach to the design and development of multi-functional super supramolecular metal hydrogel-based materials.

Self-assembling outside equilibrium: emergence of structures mediated by dissipation

Self-assembly under non-equilibrium conditions may give rise to the formation of structures not available at equilibrium.

Formation of a Bile Salt-Drug Hydrogel to Predict Human Intestinal Absorption

The unique character of bile salts to self-assemble into hydrogels in the presence of halide salts was exploited in this work to facilitate the prediction of human intestinal absorption (%HIA) for a set of 25 compounds. This was achieved by firstly incorporating each compound separately within the process of gel formation to create a series of gel-drug membranes. Scanning electron microscopy analysis of the freeze-dried samples of the blank bile salt hydrogels and drug-loaded bile salt hydrogels indicated a unique microstructure made of a network of intertwined fibrils. Drug-loaded sodium deoxycholate hydrogels were then utilized as the donor phase to study permeability using flow-through and static diffusion cells. The resulting values of the release-permeability coefficient (K_p) were then analyzed, along with other molecular descriptors, for the %HIA using multiple linear regression. Overall, when comparing predicted values (using the systems presented in this study) with known literature values, it can be seen that both methods (i.e., using static and flow-through cells) had good predictability with R²_PRED values of 79.8% and 79.7%, respectively. This study therefore proposes a novel, accurate, and precise way to predict HIA for compounds of pharmaceutical interest using a simple in vitro permeation system. It is important to develop alternatives to the current methods used in prediction of HIA, which are expensive and time-consuming or include the use of animals. Therefore, the proposed method in this study being economic and time-saving provides superiority over these current methods and suggests the possibility of its use as an alternate to such methods for prediction of HIA.

Carbon quantum dot-based fluorescent vesicles and chiral hydrogels with biosurfactant and biocompatible small molecule

In recent years, it is heartening to witness that carbon quantum dots (CQDs), a rising star in the family of carbon nanomaterials, have displayed tremendous applications in bioimaging, biosensing, drug delivery, optoelectronics, photovoltaics and photocatalysis. However, the investigations toward self-assembly of CQDs are still in their infancy. The participation of CQDs can bring additional functions to supramolecular self-assemblies, with photoluminescent property as the most exciting aspect. Here, we introduce CQDs into two types of classic colloidal systems containing low molecular weight surfactant and gelator to construct fluorescent vesicles and chiral hydrogels. The CQD-based vesicles were constructed through electrostatic interaction between the positively charged CQDs with peripherally substituted imidazolium cations and a negatively-charged biosurfactant, i.e., sodium deoxycholate (NaDC). The chiral hydrogels were prepared by increasing the concentration of NaDC and addition of a tripeptide (glutathione, GSH). It was found that both the hydrogels and corresponding xerogels are highly photoluminescent. A solid sensing system was prepared by coating a uniform layer of the hydrogel onto the silica gel plates by doctor blade technique followed by air-drying, which was then utilized to semiquantitatively detect Cu2+ in aqueous solutions.

Direct-Continuous Preparation of Nanostructured Titania-Silica Using Surfactant-Free Non-Scaffold Rice Starch Template

The conventional synthesis route of nanostructured titania-silica (Ti-SiNS) based on sol-gel requires the use of a surfactant-type template that suffers from hazardous risks, environmental concerns, and a tedious stepwise process. Alternatively, biomaterials have been introduced as an indirect template, but still required for pre-suspended scaffold structures, which hinder their practical application. Herein, we report an easy and industrially viable direct-continuous strategy for the preparation of Ti-SiNS from nanostructured-silica (SiNS) using a hydrolyzed rice starch template. This strategy fits into the conventional industrial process flow, as it allows starch to be used directly in time-effective and less complicated steps, with the potential to upscale. The formation of Ti-SiNS is mainly attributed to Ti attachment in the SiNS frameworks after the polycondensation of the sol-gel composition under acidic-media. The SiNS had pseudo-spherical morphology (nanoparticles with the size of 13 to 22 nm), short order crystal structure (amorphous) and high surface area (538.74 m²·g−1). The functionalized SiNS into Ti-SiNS delivered considerable catalytic activity for epoxidation of 1-naphtol into 1,4-naphthoquinone. The described direct-continuous preparation shows great promise for a cheap, green, and efficient synthesis of Ti-SiNS for advanced applications.

Cation instructed steroidal prodrug supramolecular hydrogel

In the present study, we propose an ionic coordination strategy for the design of a steroidal prodrug supramolecular hydrogel. The hydrogel composed of nanofibril networks formed spontaneously by the introduction of divalent cations (e.g., Mg²⁺, Ca²⁺, Zn²⁺ and Fe²⁺) and NH₄⁺ to a succinated dexamethasone (Dex-SA) aqueous solution at room temperature. The formation of the nanofibril structure was dominantly driven by the ionic coordination with the assistance of a delicate balance of multiple noncovalent interactions. A rheological analysis indicated that the formed Ca²⁺/Dex-SA supramolecular hydrogel exhibits dominant elastic and thixotropic properties. The formed Ca²⁺/Dex-SA supramolecular hydrogel allowed the gradual release of Dex and Dex-SA in vitro, and the drug release behaviour can be finely tuned by changing the Ca²⁺ concentration. Storage stability studies showed that Dex-SA in hydrogel underwent an apparent chemical decomposition at 4 °C and 37 °C. In contrast, the Dex-SA xerogel was quite stable without any obvious chemical decomposition of Dex-SA in storage at -20 °C for 35 days, and it was able to turn into a hydrogel again within one minute after rehydration. The formed Ca²⁺/Dex-SA supramolecular hydrogel caused negligible cytotoxicity against HCEC and L-929 cells at drug concentrations up to 2 mM, as indicated by the in vitro cytotoxicity tests. Additionally, the proposed Ca²⁺/Dex-SA supramolecular hydrogel displayed a comparable anti-inflammatory efficacy with Dexp via the downregulation of NO, TNF-α and IL-6 expression in lipopolysaccharide (LPS)-activated RAW264.7 macrophage. Overall, the cation instructed steroidal prodrug supramolecular hydrogel might be a promising ophthalmic drug delivery system for anti-inflammatory therapy.

Coordination-Triggered Hierarchical Folate/Zinc Supramolecular Hydrogels Leading to Printable Biomaterials

Printable hydrogels desired in bioengineering have extremely high demands on biocompatibility and mechanic strength, which can hardly be achieved in conventional hydrogels made with biopolymers. Here, we show that on employment of the strategy of coordination-triggered hierarchical self-assembly of naturally occurring small-molecule folic acid, supramolecular hydrogels with robust mechanical elastic modulus comparable to synthetic double-network polymer gels can be made at concentrations below 1%. A sequence of hierarchical steps are involved in the formation of this extraordinary hydrogel: petrin rings on folate form tetramers through hydrogen bonding, tetramers stack into nanofibers by π-π stacking, and zinc ions cross-link the nanofibers into larger-scale fibrils and further cross-link the fibril network to gel water. These supramolecular qualities endow the hydrogel with shear-thinning and instant healing ability, which makes the robust gel injectable and printable into various three-dimensional structures. Owing to the excellent biocompatibility, the gel can support cells three-dimensionally and can be used as an ideal carrier for imaging agent (Gd³⁺), as well as chemodrugs. In combination with its easy formation and abundant sources, this newly discovered metallo-folate supramolecular hydrogel is promising in various bioengineering technological applications.

Gels with sense: supramolecular materials that respond to heat, light and sound

Advances in the field of supramolecular chemistry have made it possible, in many situations, to reliably engineer soft materials to address a specific technological problem. Particularly exciting are "smart" gels that undergo reversible physical changes on exposure to remote, non-invasive environmental stimuli. This review explores the development of gels which are transformed by heat, light and ultrasound, as well as other mechanical inputs, applied voltages and magnetic fields. Focusing on small-molecule gelators, but with reference to organic polymers and metal-organic systems, we examine how the structures of gelator assemblies influence the physical and chemical mechanisms leading to thermo-, photo- and mechano-switchable behaviour. In addition, we evaluate how the unique and versatile properties of smart materials may be exploited in a wide range of applications, including catalysis, crystal growth, ion sensing, drug delivery, data storage and biomaterial replacement.

Controlled synthesis of novel one-dimensional structured ZIFs via supramolecular self-assemblies

Various 1D ZIF-8 nanomaterials have been synthesized via the self-templates of supramolecular self-assemblies, which exhibit hierarchical pores and high surface area. The resultant microstructures could be applied as excellent drug delivery vehicles and also as excellent carriers for enzymes with remarkable enzymatic activity.

The effect of temperature, composition and alcohols on the microstructures of catanionic mixtures of sodium dodecylsulfate and cetyltrimethylammonium bromide in water

The influence of mixing protocol, composition, temperature, ageing and added alcohols on the characteristics of the microstructures of sodium dodecylsulfate (SDS) + cetyltrimethylammonium bromide (CTAB) mixtures has been investigated in this paper. In this catanionic mixture (1 weight% total surfactant content) temperature induced microstructural transition occurs, which is (i) a micelle-to-vesicle transition (MVT) if α_SDS (mole fraction of SDS) = 0.7, 0.8 or 0.9 and (ii) a vesicle-to-micelle transition (VMT) if α_SDS = 0.1, 0.2 or 0.3. In the mixture of α_SDS = 0.7, specific conductivity and dynamic light scattering measurements also support the occurrence of MVT. Transition electron microscopy and small angle neutron scattering measurements were also made to assess the characteristics of the microstructures. Alcohols added to the mixture of α_SDS = 0.7 reduced the size of the vesicle, while only monohydric alcohols suppressed the temperature induced transition indicating that the number and location of -OH groups of the alcohols have a dramatic modulating influence on the structural transition occurring in catanionic mixtures. The influence of the alcohols is explained in terms of changes produced in the dielectric constant and hydrophobicity of the medium.

Metallogels of indium(iii) with bile salts: soft materials for nanostructured In2S3 synthesis

Metallo-hydrogels were formed from sodium cholate and deoxycholate in the presence of indium(iii). This soft hydrogel was used for nanostructured In₂S₃ synthesis.

Hydrogels of Superlong Helices to Synthesize Hybrid Ag-Helical Nanomaterials

The gelation behavior of mixtures of sodium deoxycholate (NaDC) and glutathione (GSH) in water is investigated. The system exhibits a structural transition of self-assembled hydrogels from nanofibers to nanohelix structures, and then to helical ribbons with increasing GSH concentration. Superlong helical nanofibers with left- and right-handed orientations are produced by tuning the concentration of GSH at a fixed concentration of NaDC. Random coil and β-sheet structures are significant for the formation of the helical structures, and are indicated by circular dichroism (CD) and Fourier transform infrared (FT-IR) spectra. The mechanical strength of the "weak" hydrogels is enhanced by the introduction of appropriate suitable amount of AgNO₃. Furthermore, the controlled growth of Ag nanoparticles at spatially arranged locations along the nanohelices (hybrid Ag-helical nanomaterial) is readily achieved by UV reduction of Ag (I) ions on the supramolecular helical templates.

A Supramolecular Shear-Thinning Anti-Inflammatory Steroid Hydrogel

Shear-thinning and self-healing steroid-drug-based hydrogels are presented, which exhibit rapid and complete recovery of their mechanical properties within seconds following stress-induced flow. The hydrogels release steroid drug in vivo with no visible residue when release is complete.

Two Gelation Mechanisms of Deoxycholate with Inorganic Additives: Hydrogen Bonding and Electrostatic Interactions

This work describes the gelation behaviors of a biological amphiphile, deoxycholate (DC(-)), in aqueous solution by adding inorganic salts and modulating pH. Electrostatic interaction and hydrogen bonding can separately act as the controlling interaction for the hydrogel formation. The hydrogels formed at higher pH (about 8.5) through introducing monovalent inorganic cations (Na(+)) are mainly driven by electrostatic interaction between deoxycholate species and Na(+) ions. When pH is decreased, with the formation of DCA molecules, hydrogen bonding between DC(-) and DCA come into being another leading role to construct the hydrogels, which can induce the gels within an appropriate pH region (6.7-7.3) without inorganic cations. Gels constructed through the self-assembly of deoxycholate present diverse properties according to the difference in the main driving force. Moreover, the combination of the two important interactions can significantly enhance the gelation ability.

Hydrogelation and Crystallization of Sodium Deoxycholate Controlled by Organic Acids

The gelation and crystallization behavior of a biological surfactant, sodium deoxycholate (NaDC), mixed with l-taric acid (L-TA) in water is described in detail. With the variation of molar ratio of L-TA to NaDC (r = n(L-TA)/n(NaDC)) and total concentration of the mixtures, the transition from sol to gel was observed. SEM images showed that the density of nanofibers gradually increases over the sol-gel transition. The microstructures of the hydrogels are three-dimensional networks of densely packed nanofibers with lengths extending to several micrometers. One week after preparation, regular crystallized nanospheres formed along the length of the nanofibers, and it was typical among the transparent hydrogels induced by organic acids with pKa1 value <3.4. Small-angle X-ray diffraction demonstrated differences in the molecular packing between transparent and turbid gels, indicating a variable hydrogen bond mode between NaDC molecules.

Adaptive soft molecular self-assemblies

Adaptive molecular self-assemblies provide possibility of constructing smart and functional materials in a non-covalent bottom-up manner. Exploiting the intrinsic properties of responsiveness of non-covalent interactions, a great number of fancy self-assemblies have been achieved. In this review, we try to highlight the recent advances in this field. The following contents are focused: (1) environmental adaptiveness, including smart self-assemblies adaptive to pH, temperature, pressure, and moisture; (2) special chemical adaptiveness, including nanostructures adaptive to important chemicals, such as enzymes, CO2, metal ions, redox agents, explosives, biomolecules; (3) field adaptiveness, including self-assembled materials that are capable of adapting to external fields such as magnetic field, electric field, light irradiation, and shear forces.

Supramolecular hydrogelation with bile acid derivatives: structures, properties and applications

Bile acid derivatives can form molecular hydrogels that may be useful for drug delivery, tissue engineering and nanotemplating.

Formation of molecular hydrogels from a bile acid derivative and selected carboxylic acids

A cholic acid dimer forms hydrogels with selected carboxylic acids via protonation and hydrogen bonding.

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.

Impact of Alkyl Chain Length on the Transition of Hexagonal Liquid Crystal-Wormlike Micelle-Gel in Ionic Liquid-Type Surfactant Aqueous Solutions without Any Additive

The search for functional supramolecular aggregations with different structure has attracted interest of chemists because they have the potential in industrial and technological application. Hydrophobic interaction has great influence on the formation of these aggregations, such as hexagonal liquid crystals, wormlike micelles, hydrogels, etc. So a systematical investigation was done to investigate the influence of alkyl chain length of surfactants on the aggregation behavior in water. The aggregation behavior of 1-hexadecyl-3-alkyl imidazolium bromide and water has been systematically investigated. These ionic liquid surfactants are denoted as C16-Cn (n = 2, 3, 4, 6, 8, 9, 10, 12, 14, 16). The rheological behavior and microstructure were characterized via a combination of rheology, cryo-etch scanning electron microscopy, polarization optical microscopy, and X-ray crystallography. The alkyl chain has great influence on the formation of surfactant aggregates in water at the molecular level. With increasing alkyl chain length, different aggregates, such as hexagonal liquid crystals, wormlike micelles, and hydrogels can be fabricated: C16-C2 aqueous solution only forms hexagonal liquid crystal; C16-C3 aqueous solution forms wormlike micelle and hexagonal liquid crystal; C16-C4, C16-C6 and C16-C8 aqueous solutions only form wormlike micelle; C16-C9 aqueous solution experiences a transition between wormlike micelle and hydrogel; C16-C10, C16-C12, C16-C14 and C16-C16 only form hydrogel. The mechanism of the transition of different aggregation with increasing alkyl chain length was also proposed.

Concentration and temperature induced dual-responsive wormlike micelle to hydrogel transition in ionic liquid-type surfactant [C₁₆imC₉]Br aqueous solution without additives

A highly viscoelastic fluid formed by the ionic liquid-type surfactant 1-hexadecyl-3-nonyl imidazolium bromide ([C16imC9]Br) in water in the absence of any additive was studied. The phase behavior and morphology of aggregates were studied by a combination of rheological techniques, small-angle X-ray scattering (SAXS), cryo-etch-scanning electron microscopy (cryo-etch-SEM) and freeze-fractured transmission electron microscopy (FF-TEM). [C16imC9]Br aqueous solutions showed interesting rheological behavior as a function of both concentration and temperature, which invoked a transition between wormlike micelles and hydrogels. With the increase in [C16imC9]Br concentration, the aqueous solution could form viscoelastic wormlike micelles (50-80 mM), hydrogels (90-110 mM) and wormlike micelles (120-180 mM). As the temperature increased, the hydrogels (90-110 mM) could also transit to wormlike micelles. The unusual phase transition between wormlike micelles and elastic hydrogels was postulated to be the change of the average micellar length.