Stable emulsions formed by self-assembly of interfacial networks of dipeptide derivatives

A Facile Way to Enhance the Therapeutic Efficacy of Hydrophobic Drugs via Amorphous Solid Dispersions

Approximately 40% of marketed drugs and 75% of invested drugs in the pharmaceutical field are poorly soluble hydrophobic drugs with minimal solubility in water which make them difficult to be absorbed by the body and significantly limiting their applications. Among chemotherapeutic agents, numerous antitumor drugs such as platinum compounds, camptothecin, paclitaxel and others are also restricted in processing and preparation due to solubility issues. Therefore, improving the solubility and enhancing the therapeutic efficacy of drugs have always been significant research topics in current pharmaceutics. Herein, we propose an amorphous solid dispersion system PRTA-DOX, involving the protein drug protamine sulphate and hydrophobic doxorubicin as the model hydrophobic drug. In previous studies, ASD (Amorphous Solid Dispersion) has been demonstrated to enhance the solubility of hydrophobic drugs and result in a storage-stable system. Protamine sulphate as a marketed drug is reliable in safety and conveniently obtained. Doxorubicin, an antitumor drug with a broad antitumor spectrum, is commonly used in the treatment of breast cancer. Typically, doxorubicin is prepared in the form of a hydrochloride salt to increase its solubility. However, the utilization of doxorubicin hydrochloride is reduced due to drug resistance issues in biological cells and it exhibits higher toxicity to the body. In this system, protamine sulphate which is rich in arginine guanidino hydrophobic planes physically mixes with doxorubicin which is a hydrophobic molecule with aromatic rings and they are connected through weak interactions: π-π conjugation. They constitute an amorphous solid dispersion system which increases the solubility of hydrophobic doxorubicin, enhances cellular uptake, mitigate some cellular drug resistance and thereby achieves the purpose of improving therapeutic efficacy.

Evolving Emulsion Microcompartments via Enzyme-Mimicking Amyloid-Mediated Interfacial Catalysis

Living organisms take in matter and energy from their surroundings, transforming these inputs into forms that cells can use to sustain metabolism and power various functions. A significant advancement in the development of protocells and life-like materials has been the creation of cell-like microcompartments capable of evolving into higher-order structures characterized by hierarchy and complexity. In this study, a smart emulsion system is designed to digests chemical substrates and generates organic or inorganic products, driving the self-organization and structuration of microcompartments. Central to this system is a lipase-derived peptide that undergoes amyloid fibrillation, exhibiting hydrolase-like activity and stabilizing Pickering emulsions. Through catalytic hydrolysis or silicatein-inspired mineralization, these emulsion microcompartments generate self-organized surfactant layers from organic substrates or silica scaffolds from inorganic substrates at the oil-water interface, respectively, helping to prevent coalescence. This process further facilitates a structural evolution into high-internal phase emulsion gels that are suitable for direct-ink-writing 3D printing. The findings underscore the potential for designing self-evolving soft materials that replicate the structures and functions of living organisms.

A Review on the Rheological Properties of Single Amino Acids and Short Dipeptide Gels

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.

Designer peptide-DNA cytoskeletons regulate the function of synthetic cells

The bottom-up engineering of artificial cells requires a reconfigurable cytoskeleton that can organize at distinct locations and dynamically modulate its structural and mechanical properties. Here, inspired by the vast array of actin-binding proteins and their ability to reversibly crosslink or bundle filaments, we have designed a library of peptide-DNA crosslinkers varying in length, valency and geometry. Peptide filaments conjoint through DNA hybridization give rise to tactoid-shaped bundles with tunable aspect ratios and mechanics. When confined in cell-sized water-in-oil droplets, the DNA crosslinker design guides the localization of cytoskeletal structures at the cortex or within the lumen of the synthetic cells. The tunable spatial arrangement regulates the passive diffusion of payloads within the droplets and complementary DNA handles allow for the reversible recruitment and release of payloads on and off the cytoskeleton. Heat-induced reconfiguration of peptide-DNA architectures triggers shape deformations of droplets, regulated by DNA melting temperatures. Altogether, the modular design of peptide-DNA architectures is a powerful strategy towards the bottom-up assembly of synthetic cells.

3,4-Ethylenedioxythiophene Hydrogels: Relating Structure and Charge Transport in Supramolecular Gels

Ionic charge transport is a ubiquitous language of communication in biological systems. As such, bioengineering is in constant need of innovative, soft, and biocompatible materials that facilitate ionic conduction. Low molecular weight gelators (LMWGs) are complex self-assembled materials that have received increasing attention in recent years. Beyond their biocompatible, self-healing, and stimuli responsive facets, LMWGs can be viewed as a "solid" electrolyte solution. In this work, we investigate 3,4-ethylenedioxythiophene (EDOT) as a capping group for a small peptide library, which we use as a system to understand the relationship between modes of assembly and charge transport in supramolecular gels. Through a combination of techniques including small-angle neutron scattering (SANS), NMR-based Van't Hoff analysis, atomic force microscopy (AFM), rheology, four-point probe, and electrochemical impedance spectroscopy (EIS), we found that modifications to the peptide sequence result in distinct assembly pathways, thermodynamic parameters, mechanical properties, and ionic conductivities. Four-point probe conductivity measurements and electrochemical impedance spectroscopy suggest that ionic conductivity is approximately doubled by programmable gel assemblies with hollow cylinder morphologies relative to gels containing solid fibers or a control electrolyte. More broadly, it is hoped this work will serve as a platform for those working on charge transport of aqueous soft materials in general.

Structural Transformation of Coassembled Fmoc-Protected Aromatic Amino Acids to Nanoparticles

Materials made of assembled biomolecules such as amino acids have drawn much attention during the past decades. Nevertheless, research on the relationship between the chemical structure of building block molecules, supramolecular interactions, and self-assembled structures is still necessary. Herein, the self-assembly and the coassembly of fluorenylmethoxycarbonyl (Fmoc)-protected aromatic amino acids (tyrosine, tryptophan, and phenylalanine) were studied. The individual self-assembly of Fmoc-Tyr-OH and Fmoc-Phe-OH in water formed nanofibers, while Fmoc-Trp-OH self-assembled into nanoparticles. Moreover, when Fmoc-Tyr-OH or Fmoc-Phe-OH was coassembled with Fmoc-Trp-OH, the nanofibers were transformed into nanoparticles. UV-vis spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectroscopy were used to investigate the supramolecular interactions leading to the self-assembled architectures. π-π stacking and hydrogen bonding were the main driving forces leading to the self-assembly of Fmoc-Tyr-OH and Fmoc-Phe-OH forming nanofibers. Further, a mechanism involving a two-step coassembly process is proposed based on nucleation and elongation/growth to explain the structural transformation. Fmoc-Trp-OH acted as a fiber inhibitor to alter the molecular interactions in the Fmoc-Tyr-OH or Fmoc-Phe-OH self-assembled structures during the coassembly process, locking the coassembly in the nucleation step and preventing the formation of nanofibers. This structural transformation is useful for extending the application of amino acid self- or coassembled materials in different fields. For example, the amino acids forming nanofibers could be applied for tissue engineering, while they could be exploited as drug nanocarriers when they form nanoparticles.

Three Stages of Dynamic Assembly Process of Dipeptide-Based Supramolecular Gel Revealed by In Situ Infrared Spectroscopy

The exploration of short peptide-based assembly is vital for understanding protein-misfolding-associated diseases and seeking strategies to attenuate aggregate formation. While, the molecular mechanism of their structural evolution remains poorly studied in view of the dynamic and unpredictable assembly process. Herein, infrared (IR) spectroscopy, which serves as an in situ and real-time analytical technique, was intelligently employed to investigate the mechanism of phase transition and aggregate formation during the dynamic assembly process of diphenylalanine. Combined with other spectroscopy and electron microscopy technologies, three stages of gel formation and the main driving forces in different stages were revealed. A variety of stoichiometric methods such as continuous wavelet transform, principal component analysis, and two-dimensional correlation spectroscopy techniques were conducted to analyze the original time-dependent IR spectra to obtain detailed information on the changes in the amide bands and hydration layer. The microenvironment of hydrogen bonding among amide bands was significantly changed with the addition of pyridine derivatives, resulting in great differences in the properties of co-assembled gels. This work not only provides a universal analytical way to reveal the dynamic assembly process of dipeptide-based supramolecular gel but also expands their applications in supramolecular regulation and high-throughput screens in situ.

Synergetic Self-Assembly of Liquid Crystalline Block Copolymer with Amphiphiles for Fabrication of Hierarchical Assemblies

Novel functions and advanced structure, where each single component could not be produced individually, can exhibit from the collective and synergistic behavior of component systems. This synergetic strategy has been successfully demonstrated for co-assembly of polymer-polymer to construct hierarchical nanomaterials. However, differences in the natures of polymer and small molecules impose challenges in the construction of sophisticated co-assemblies with geometrical and compositional control. Herein, a synergetic self-assembly strategy is proposed to prepare organic-organic hybrid colloidal mesostructures by blending a liquid crystalline block copolymer (LC-BCP) with small molecular amphiphiles. Through a classic solvent-exchange process, amphiphiles embedded with LC-BCP realize multi-component nucleation and hierarchical assembly driven by anisotropic interaction from the LC ordering alignment of the core-forming block. 1D nanofibers with a periodic striped structure are formed by further LC component fusion and refinement. In addition, LC ordering effect of LC-BCP can be regulated by selecting appropriate solvents and leads to the formation of vesicular co-micelles. By means of the thermal-responsive behavior of amphiphiles, hexagonal pore arrays are finally generated on the surface of those vesicles.

Developing Safe Organohydrogel Sunscreens Using Polyelectrolyte-Betaine Surfactant Complexes

Oil-in-water emulsions are extensively used in skincare products due to their improved texture, stability, and effectiveness. There is limited success in developing effective delivery systems that can selectively target the active sunscreen ingredients onto the skin surface. Herein, an organohydrogel was prepared by physical cross-linking of an oil-in-water nanoemulsion with chitosan under neutral pH conditions. In the presence of a small quantity of coconut oil, lauramidopropyl betaine and glycerol were able to emulsify the active sunscreen ingredients into nanoscale droplets with enhanced ultraviolet light absorption. A facile pH-triggered interfacial cross-linking approach was applied to transform the nanoemulsion into an organohydrogel sunscreen. Furthermore, the organohydrogel sunscreen displayed encouraging characteristics including efficient UV-blocking capacity, resistance to water, simple removal, and minimal skin penetration. This facile approach provides an effective pathway for scaling up the organohydrogels, which are highly suitable for the safe application of sunscreen.

Real-Time, In Situ Imaging of Macrophages via Phase-Change Peptide Nanoemulsions

Macrophages are specialized phagocytes that play central roles in immunity and tissue repair. Their diverse functionalities have led to an evolution of new allogenic and autologous macrophage products. However, realizing the full therapeutic potential of these cell-based therapies requires development of imaging technologies that can track immune cell migration within tissues in real-time. Such innovations will not only inform treatment regimens and empower interpretation of therapeutic outcomes but also enable prediction and early intervention during adverse events. Here, phase-changing nanoemulsion contrast agents are reported that permit real-time, continuous, and high-fidelity ultrasound imaging of macrophages in situ. Using a de novo designed peptide emulsifier, liquid perfluorocarbon nanoemulsions are prepared and show that rational control over interfacial peptide assembly affords formulations with tunable acoustic sensitivity, macrophage internalization, and in cellulo stability. Imaging experiments demonstrate that emulsion-loaded macrophages can be readily visualized using standard diagnostic B-mode and Doppler ultrasound modalities. This allows on-demand and long-term tracking of macrophages within porcine coronary arteries, as an exemplary model. The results demonstrate that this platform is poised to open new opportunities for non-invasive, contrast-enhanced imaging of cell-based immunotherapies in tissues, while leveraging the low-cost, portable, and safe nature of diagnostic ultrasound.

Peptide hydrogels: Synthesis, properties, and applications in food science

Due to the unique and excellent biological, physical, and chemical properties of peptide hydrogels, their application in the biomedical field is extremely wide. The applications of peptide hydrogels are closely related to their unique responsiveness and excellent properties. However, its defects in mechanical properties, stability, and toxicity limit its application in the food field. In this review, we focus on the fabrication methods of peptide hydrogels through the physical, chemical, and biological stimulations. In addition, the functional design of peptide hydrogels by the incorporation with materials is discussed. Meanwhile, the excellent properties of peptide hydrogels such as the stimulus responsiveness, biocompatibility, antimicrobial properties, rheology, and stability are reviewed. Finally, the application of peptide hydrogel in the food field is summarized and prospected.

Self-assembled short peptides: Recent advances and strategies for potential pharmaceutical applications

Self-assembled short peptides have intrigued scientists due to the convenience of synthesis, good biocompatibility, low toxicity, inherent biodegradability and fast response to change in the physiological environment. Therefore, it is necessary to present a comprehensive summary of the recent advances in the last decade regarding the construction, route of administration and application of self-assembled short peptides based on the knowledge on their unique and specific ability of self-assembly. Herein, we firstly explored the molecular mechanisms of self-assembly of short peptides, such as non-modified amino acids, as well as Fmoc-modified, N-functionalized, and C-functionalized peptides. Next, cell penetration, fusion, and peptide targeting in peptide-based drug delivery were characterized. Then, the common administration routes and the potential pharmaceutical applications (drug delivery, antibacterial activity, stabilizers, imaging agents, and applications in bioengineering) of peptide drugs were respectively summarized. Last but not least, some general conclusions and future perspectives in the relevant fields were briefly listed. Although with certain challenges, great opportunities are offered by self-assembled short peptides to the fascinating area of drug development.

Biocompatible Short-Peptides Fibrin Co-assembled Hydrogels

Fibrin hydrogels made by self-assembly of fibrinogen obtained from human plasma have shown excellent biocompatible and biodegradable properties and are widely used in regenerative medicine. The fibrinogen self-assembly process can be triggered under physiological conditions by the action of thrombin, allowing the injection of pregel mixtures that have been used as cell carriers, wound-healing systems, and bio-adhesives. However, access to fibrinogen from human plasma is expensive and fibrin gels have limited mechanical properties, which make them unsuitable for certain applications. One solution to these problems is to obtain composite gels made of fibrin and other polymeric compounds that improve their mechanical properties and usage. Herein, we prepared composite hydrogels made by the self-assembly of fibrinogen together with Fmoc-FF (Fmoc-diphenylalanine) and Fmoc-RGD (Fmoc-arginine-glycine-aspartic acid). We have shown that the mixture of these three peptides co-assembles and gives rise to a unique type of supramolecular fiber, whose morphology and mechanical properties can be modulated. We have carried out a complete characterization of these materials from chemical, physical, and biological points of view. Composite gels have improved mechanical properties compared to pure fibrin gels, as well as showing excellent biocompatibility ex vivo. In vivo experiments have shown that these gels do not cause any type of inflammatory response or tissue damage and are completely resorbed in short time, which would enable their use as vehicles for cell, drug, or growth factor release.

Surface Self-Assembly of Dipeptides on Porous CaCO3 Particles Promoting Cell Internalization

The self-assembling behavior of peptides and derivatives is crucial in the natural process to construct various architectures and achieve specific functions. However, the surface or interfacial self-assembly, in particular, on the surface of micro- or nanoparticles is even less systematically investigated. Here, uniform porous CaCO₃ microparticles were prepared with different charged, hydrophobic and hydrophilic surfaces to assess the self-assembling behavior of dipeptides composed of various sequences. Experimental results indicate that dipeptides with a negative charge in an aqueous solution preferred to self-assemble on the hydrophobic and positively charged surface of CaCO₃ particles, which can be ascribed to the electrostatic and hydrophobic interaction between dipeptides and CaCO₃ particles. Meanwhile, the Log p (lipid-water partition coefficient) of dipeptides has a significant effect on the self-assembling behavior of dipeptides on the surface of porous CaCO₃; dipeptides with high Log p preferred to self-assemble on the surface of CaCO₃ particles, resulting in the improved cell internalization efficiency of particles with low cytotoxicity. After loading with a model drug (doxorubicin), the particles show obvious antitumor activity in animal experiments and can reduce Dox side effects effectively.

Spatiotemporal Control Over Base-Catalysed Hydrogelation Using a Bilayer System

Controlling the formation and directional growth of hydrogels is a challenge. In this paper, we propose a new methodology to program the gel formation both over space and time, using the diffusion and subsequent hydrolysis of 1,1'-carbonyldiimidazole (CDI) from an immiscible organic solution to the aqueous gel media. This article is protected by copyright. All rights reserved.

Destructing surfactant network in nanoemulsions by positively charged magnetic nanorods to enhance oil-water separation

The separation of ultrafine oil droplets from wasted nanoemulsions stabilized with high concentration of surfactants is precondition for oil reuse and the safe discharge of effluent. However, the double barriers of the interfacial film and network structures formed by surfactants in nanoemulsions significantly impede the oil-water separation. To destroy these surfactant protective layers, we proposed a newly-developed polyethyleneimine micelle template approach to achieve simultaneous surface charge manipulation and morphology transformation of magnetic nanospheres to magnetic nanorods. The results revealed that positively charged magnetic nanospheres exhibited limited separation performance of nanoemulsions, with a maximum chemical oxygen demand (COD) removal of 50%, whereas magnetic nanorods achieved more than 95% COD removal in less than 30 s. The magnetic nanorods were also applicable to wasted nanoemulsions from different sources and exhibited excellent resistance to wide pH changes. Owing to their unique one-dimensional structure, the interfacial dispersion of magnetic nanorods was significantly promoted, leading to the efficient capture of surfactants and widespread destruction of both the interfacial film and network structure, which facilitated droplet merging into the oil phase. The easy-to-prepare and easy-to-tune strategy in this study paves a feasible avenue to simultaneously tailor surface charge and morphology of magnetic nanoparticles, and reveals the huge potential of morphology manipulation for producing high-performance nanomaterials to be applied in complex interfacial interaction process. We believe that the newly-developed magnetic-nanorods significantly contribute to hazardous oily waste remediation and advances technology evolution toward problematic oil-pollution control.

pH-driven-assembled soy peptide nanoparticles as particulate emulsifier for oil-in-water Pickering emulsion and their potential for encapsulation of vitamin D3

Pickering emulsions prepared by food-grade particles have gained growing attention due to their promising application in functional food and pharmaceutical industries. In this study, we successfully fabricated soy peptide-based nanoparticles (SPN) through pH-driven process. Obtained particles with small particle size were surface active and shared intermediate wettability, and they could be well applied as an efficient particulate emulsifier for stabilizing oil-in-water Pickering emulsions at SPN concentration above 0.25 wt%. Furthermore, formed emulsions stabilized with SPN exhibited good protection towards Vitamin D₃ against UV irradiation and oxidative deterioration, where controlled release of Vitamin D₃in vitro could also be well achieved by modulating particle concentration. The whole process can contribute to a sustainable development of low-value peptide byproducts as functional food ingredients.

Personal Perspective on Understanding Low Molecular Weight Gels

Low molecular weight gels are formed by the self-assembly of small molecules into anisotropic structures that form a network capable of immobilizing the solvent. Such gels are common, with a huge number of different examples existing, and they have many applications. However, there are still significant gaps in our understanding of these systems and challenges that need to be addressed if we are to be able to fully design such systems. Here, a number of these challenges are discussed.

Bioinspired Hydrogels as Platforms for Life-Science Applications: Challenges and Opportunities

Hydrogels, as interconnected networks (polymer mesh; physically, chemically, or dynamic crosslinked networks) incorporating a high amount of water, present structural characteristics similar to soft natural tissue. They enable the diffusion of different molecules (ions, drugs, and grow factors) and have the ability to take over the action of external factors. Their nature provides a wide variety of raw materials and inspiration for functional soft matter obtained by complex mechanisms and hierarchical self-assembly. Over the last decade, many studies focused on developing innovative and high-performance materials, with new or improved functions, by mimicking biological structures at different length scales. Hydrogels with natural or synthetic origin can be engineered as bulk materials, micro- or nanoparticles, patches, membranes, supramolecular pathways, bio-inks, etc. The specific features of hydrogels make them suitable for a wide variety of applications, including tissue engineering scaffolds (repair/regeneration), wound healing, drug delivery carriers, bio-inks, soft robotics, sensors, actuators, catalysis, food safety, and hygiene products. This review is focused on recent advances in the field of bioinspired hydrogels that can serve as platforms for life-science applications. A brief outlook on the actual trends and future directions is also presented.

Shaping and Patterning Supramolecular Materials─Stem Cell-Compatible Dual-Network Hybrid Gels Loaded with Silver Nanoparticles

Hydrogels with spatio-temporally controlled properties are appealing materials for biological and pharmaceutical applications. We make use of mild acidification protocols to fabricate hybrid gels using calcium alginate in the presence of a preformed thermally triggered gel based on a low-molecular-weight gelator (LMWG) 1,3:2:4-di(4-acylhydrazide)-benzylidene sorbitol (DBS-CONHNH₂). Nonwater-soluble calcium carbonate slowly releases calcium ions over time when exposed to an acidic pH, triggering the assembly of the calcium alginate gel network. We combined the gelators in different ways: (i) the LMWG was used as a template to spatially control slow calcium alginate gelation within preformed gel beads, using glucono-δ-lactone (GdL) to lower the pH; (ii) the LMWG was used as a template to spatially control slow calcium alginate gelation within preformed gel trays, using diphenyliodonium nitrate (DPIN) as a photoacid to lower the pH, and spatial resolution was achieved by masking. The dual-network hybrid gels display highly tunable properties, and the beads are compatible with stem cell growth. Furthermore, they preserve the LMWG function of inducing in situ silver nanoparticle (AgNP) formation, which provides the gels with antibacterial activity. These gels have potential for eventual regenerative medicine applications in (e.g.) bone tissue engineering.

Directed Discovery of Tetrapeptide Emulsifiers

Oil in water emulsions are an important class of soft material that are used in the food, cosmetic, and biomedical industries. These materials are formed through the use of emulsifiers that are able to stabilize oil droplets in water. Historically emulsifiers have been developed from lipids or from large biomolecules such as proteins. However, the ability to use short peptides, which have favorable degradability and toxicity profiles is seen as an attractive alternative. In this work, we demonstrate that it is possible to design emulsifiers from short (tetra) peptides that have tunability (i.e., the surface activity of the emulsion can be tuned according to the peptide primary sequence). This design process is achieved by applying coarse grain molecular dynamics simulation to consecutively reduce the molecular search space from the 83,521 candidates initially considered in the screen to four top ranking candidates that were then studied experimentally. The results of the experimental study correspond well to the predicted results from the computational screening verifying the potential of this screening methodology to be applied to a range of different molecular systems.

Micro- and Nanocapsules Based on Artificial Peptides

The encapsulation of active ingredients into solid capsules from biodegradable materials has received significant attention over the last decades. In this short review, we focus on the formation of micro- and nano-sized capsules and emulsions based on artificial peptides as a fully degradable material. It deals with various approaches for the preparation of peptide-based capsules as well as with their crucial properties such as size and stability. We categorize all preparation procedures into three basic approaches: self-assembly, polymerization and crosslinking, and layer-by-layer technology. This article is meant to offer a short overview over all successful methods suitable for obtaining access to these very promising carrier systems.

Impacts of preparation conditions on the structure and emulsifying properties of casein-alginate conjugates produced by transacylation reaction

The Maillard reaction is often used to glycate proteins but produces undesirable byproducts. In this study, the transacylation reaction was used for the first time to prepare protein-polysaccharide conjugates from sodium caseinate (NaCas) and propylene glycol alginate (PGA) as novel emulsifiers. By mixing NaCas and PGA (1% w/v) at mass ratios of 1:2, 1:1, and 2:1 for 2 h with pH maintained at 11.0, NaCas-alginate conjugates with 52.8%, 66.2%, and 76.5% NaCas were prepared, respectively. The purified conjugates resulted in the preparation of oil-in-water emulsions with a low surfactant-to-oil ratio of 0.75:100 (w:v), and the resultant emulsions were stable against environmental stresses of pH, ionic strength, and thermal pasteurization. Structural analyses showed the role of NaCas content in reducing droplet size and the role of the alginate moiety stabilizing oil droplets via the electrostatic and steric mechanisms. This work may be significant to prepare protein-polysaccharide conjugates with high emulsifying capacity and tunable functionalities using a scalable and green method.

Supramolecular fibrillation of peptide amphiphiles induces environmental responses in aqueous droplets

One-dimensional (1D) supramolecular polymers are commonly found in natural and synthetic systems to prompt functional responses that capitalise on hierarchical molecular ordering. Despite amphiphilic self-assembly being significantly studied in the context of aqueous encapsulation and autopoiesis, very little is currently known about the physico-chemical consequences and functional role of 1D supramolecular polymerisation confined in aqueous compartments. Here, we describe the different phenomena that resulted from the chemically triggered supramolecular fibrillation of synthetic peptide amphiphiles inside water microdroplets. The confined connection of suitable dormant precursors triggered a physically autocatalysed chemical reaction that resulted in functional environmental responses such as molecular uptake, fusion and chemical exchange. These results demonstrate the potential of minimalistic 1D supramolecular polymerisation to modulate the behaviour of individual aqueous entities with their environment and within communities.

Tuning Supramolecular Polymers' Amphiphilicity via Host-Guest Interfacial Recognition for Stabilizing Multiple Pickering Emulsions

Supramolecular host-guest chemistry bridging the adjustable amphiphilicity and macromolecular self-assembly is well advanced in aqueous media. However, the interfacial self-assembled behaviors have not been further exploited. Herein, we designed a β-cyclodextrin-grafted alginate/azobenzene-functionalized dodecyl (Alg-β-CD/AzoC12) supra-amphiphilic system that possessed tunable amphiphilicity by host-guest interfacial self-assembly. Especially, supra-amphiphilic aggregates could be utilized as highly efficient soft colloidal emulsifiers for stabilizing water-in-oil-water (W/O/W) Pickering emulsions due to the excellent interfacial activity. Meanwhile, the assembled particle structures could be modulated by adjusting the oil-water ratio, resulting from the tunable aggregation behavior of supra-amphiphilic macromolecules. Additionally, the interfacial adsorption films could be partially destroyed/reconstructed upon ultraviolet/visible irradiation due to the stimuli-altering balance of amphiphilicity of Alg-β-CD/AzoC12 polymers, further constructing the stimulus-responsive Pickering emulsions. Therefore, the supramolecular interfacial self-assembly-mediated approach not only technologically advances the continued development of creative templates to construct multifunctional soft materials with anisotropic structures but also serves as a creative bridge between supramolecular host-guest chemistry, colloidal interface science, and soft material technology.

Self-Assembled Micellar Nanoparticles by Enzymatic Hydrolysis of High-Density Lipoprotein for the Formation and Stability of High Internal Phase Emulsions

In this study, the influence of pH on the conformational state of EHT, which was obtained from the enzymatic hydrolysis of trypsin, and the stabilizing properties of high internal phase emulsions have been demonstrated. Critical micelle concentration and transmission electron microscopy results exhibited the formation of micellar nanoparticles with mean diameters ranging from 108 to 1359.5 nm. The results of solubility, surface hydrophobicity, and conformations indicated that EHT tended to act as particulate emulsifiers at pH 3, 5, and 7, while at alkaline pH, it was more like a polymeric emulsifier, which could be proven by confocal laser scanning microscopy. The EHT at pH 7 exhibited better stabilizing properties than those at pH 9 and 11 as influenced by storage, temperature, and ionic strength. These findings might be of great importance for broadening the range of sustainable applications of amphiphilic peptides in foods and pharmaceuticals.

Hybrid Self-Assembled Gel Beads for Tuneable pH-Controlled Rosuvastatin Delivery

This article describes the fabrication of new pH-responsive hybrid gel beads combining the polymer gelator calcium alginate with two different low-molecular-weight gelators (LMWGs) based on 1,3 : 2,4-dibenzylidene-d-sorbitol: pH-responsive DBS-COOH and thermally responsive DBS-CONHNH2 , thus clearly demonstrating that different classes of LMWG can be fabricated into gel beads by using this approach. We also demonstrate that self-assembled multicomponent gel beads can be formed by using different combinations of these gelators. The different gel bead formulations exhibit different responsiveness - the DBS-COOH network can disassemble within those beads in which it is present upon raising the pH. To exemplify preliminary data for a potential application for these hybrid gel beads, we explored aspects of the delivery of the lipid-lowering active pharmaceutical ingredient (API) rosuvastatin. The release profile of this statin from the hybrid gel beads is pH-dependent, with greater release at pH 7.4 than at pH 4.0 - primary control of this process results from the pKa of the API. The extent of pH-mediated API release is also significantly further modified according to gel bead composition. The DBS-COOH/alginate beads show rapid, highly effective drug release at pH 7.4, whereas the three-component DBS-COOH/DBS-CONHNH2 /alginate system shows controlled slow release of the API under the same conditions. These initial results indicate that such gel beads constitute a promising, versatile and easily tuned platform suitable for further development for controlled drug-delivery applications.

Trimacrocyclic hexasubstituted benzene linked by labile octahedral [X(CHCl3)6]- clusters

Crystalline supramolecular architectures mediated by cations, anions, ion pairs or neutral guest species are well established. However, the robust crystallization of a well-designed receptor mediated by labile anionic solvate clusters remains unexplored. Herein, we describe the synthesis and crystalline behaviors of a trimacrocyclic hexasubstituted benzene 2 in the presence of guanidium halide salts and chloroform. Halide hexasolvate clusters, viz. [Cl(CHCl3)6]-, [Br(CHCl3)6]-, and [I(CHCl3)6]-, were found to be critical to the crystallization process, as suggested by the single-crystal structures, X-ray powder diffraction (XRPD), thermogravimetric analysis (TGA), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and NMR spectroscopy. This study demonstrates the hitherto unexpected role that labile ionic solvate clusters can play in stabilizing supramolecular architectures.

Peptide-Based Supramolecular Systems Chemistry

Peptide-based supramolecular systems chemistry seeks to mimic the ability of life forms to use conserved sets of building blocks and chemical reactions to achieve a bewildering array of functions. Building on the design principles for short peptide-based nanomaterials with properties, such as self-assembly, recognition, catalysis, and actuation, are increasingly available. Peptide-based supramolecular systems chemistry is starting to address the far greater challenge of systems-level design to access complex functions that emerge when multiple reactions and interactions are coordinated and integrated. We discuss key features relevant to systems-level design, including regulating supramolecular order and disorder, development of active and adaptive systems by considering kinetic and thermodynamic design aspects and combinatorial dynamic covalent and noncovalent interactions. Finally, we discuss how structural and dynamic design concepts, including preorganization and induced fit, are critical to the ability to develop adaptive materials with adaptive and tunable photonic, electronic, and catalytic properties. Finally, we highlight examples where multiple features are combined, resulting in chemical systems and materials that display adaptive properties that cannot be achieved without this level of integration.

Self-Assembly Dipeptide Hydrogel: The Structures and Properties

Self-assembly peptide-based hydrogels are well known and popular in biomedical applications due to the fact that they are readily controllable and have biocompatibility properties. A dipeptide is the shortest self-assembling motif of peptides. Due to its small size and simple synthesis method, dipeptide can provide a simple and easy-to-use method to study the mechanism of peptides' self-assembly. This review describes the design and structures of self-assembly linear dipeptide hydrogels. The strategies for preparing the new generation of linear dipeptide hydrogels can be divided into three categories based on the modification site of dipeptide: 1) COOH-terminal and N-terminal modified dipeptide, 2) C-terminal modified dipeptide, and 3) uncapped dipeptide. With a deeper understanding of the relationship between the structures and properties of dipeptides, we believe that dipeptide hydrogels have great potential application in preparing minimal biocompatible materials.

Interfacial self-assembled behavior of pH/light-responsive host-guest alginate-based supra-amphiphiles for controlling emulsifying property

Soft emulsifiers with relatively suitable structural controllability are necessarily required for the preparation of multifunctional Pickering emulsions. Herein, a β-cyclodextrin-grafted alginate/azobenzene-functionalized dodecyl (Alg-β-CD/AzoC. 12) polymeric supra-amphiphile was designed based on the host-guest interfacial self-assembly. As compared with Alg-β-CD amphiphilic polymers, the interfacial tension of Alg-β-CD/AzoC12 supra-amphiphilic assemblies reduced from 29.57 mN/m to 0.18 mN/m, indicating the great amphiphilicity derived from Alg-β-CD/AzoC12 supra-amphiphilic assemblies. With the increase of pH, the interfacial microstructures transformed from flocculated structures, spherical structures into deformed structures. Especially, the spherical microstructures with the highest interfacial viscoelasticity and thickness demonstrated the highest emulsifying efficiency due to the steric hindrance mechanism. Moreover, the interfacial elastic modulus of adsorbed layers exhibited ~4 times of that upon the ultraviolet illumination. These results disclosed that the interfacial microstructures could be readily regulated by the tunable amphiphilicity of Alg-β-CD/AzoC12 assemblies, which would be useful for the applications of Pickering emulsions in numerous fields.

Bioinspired organohydrogels with heterostructures: Fabrications, performances, and applications

Since emerging in 1960, the artificial hydrogels have garnered enormous attentions in scientific community due to their high level of similarities to biological soft tissues in both structures and properties. With the proceeding of research, the concern of hydrogels is gradually shifted from fundamental investigation to abundant functionalization. In contrast to the natural soft tissues, the current artificial hydrogels still possess relatively simple structures and unsatisfactory environmental adaptability, extremely limiting their practical applications in complex environments. Enlightened by the prominent adaptability of biological organisms, the binary cooperative complementary principle is utilized to develop bioinspired organohydrogels by combining two components with opposite but cooperative physiochemical features. The present review provides the advanced progresses of bioinspired organohydrogels with sophisticated heterogeneous networks and desirably environmental adaptabilities. We clearly summarize the synthesizing strategies in regard to both corresponding mechanisms and typical examples, including macroscopic organohydrogels, organohydrogels with binary solvent, organohydrogels with heteronetworks, and emulsion-based organohydrogels. Meanwhile, the intriguing features of the reported organohydrogels, such as temperature resistance, switchable mechanics, adaptive wettability, and opposite components compatibility, are also clearly highlighted with a short overview of their promising applications. Ultimately, the current challenges and perspectives on the future development of bioinspired organohydrogels are also discussed.

Emerging Emulsifiers: Conceptual Basis for the Identification and Rational Design of Peptides with Surface Activity

Emulsifiers are gradually evolving from synthetic molecules of petrochemical origin to biomolecules mainly due to health and environmental concerns. Peptides represent a type of biomolecules whose molecular structure is composed of a sequence of amino acids that can be easily tailored to have specific properties. However, the lack of knowledge about emulsifier behavior, structure-performance relationships, and the implementation of different design routes have limited the application of these peptides. Some computational and experimental approaches have tried to close this knowledge gap, but restrictions in understanding the fundamental phenomena and the limited property data availability have made the performance prediction for emulsifier peptides an area of intensive research. This study provides the concepts necessary to understand the emulsifying behavior of peptides. Additionally, a straightforward description is given of how the molecular structure and conditions of the system directly impact the peptides' ability to stabilize emulsion droplets. Moreover, the routes to design and discover novel peptides with interfacial and emulsifying activity are also discussed, along with the strategies to address some of their major pitfalls and challenges. Finally, this contribution reviews methodologies to build and use data sets containing standard properties of emulsifying peptides by looking at successful applications in different fields.

Self-assembled low-molecular-weight gelator injectable microgel beads for delivery of bioactive agents

We report the preparation of hybrid self-assembled microgel beads by combining the low molecular weight gelator (LMWG) DBS-CONHNH2 and the natural polysaccharide calcium alginate polymer gelator (PG). Microgel formulations based on LMWGs are extremely rare due to the fragility of the self-assembled networks and the difficulty of retaining any imposed shape. Our hybrid beads contain interpenetrated LMWG and PG networks, and are obtained by an emulsion method, allowing the preparation of spherical gel particles of controllable sizes with diameters in the mm or μm range. Microgels based on LMWG/alginate can be easily prepared with reproducible diameters <1 μm (ca. 800 nm). They are stable in water at room temperature for many months, and survive injection through a syringe. The rapid assembly of the LMWG on cooling plays an active role in helping control the diameter of the microgel beads. These LMWG microbeads retained the ability of the parent gel to deliver the bioactive molecule heparin, and in cell culture medium this enhanced the growth of human mesenchymal stem cells. Such microgels may therefore have future applications in tissue repair. This approach to fabricating LMWG microgels is a platform technology, which could potentially be applied to a variety of different functional LMWGs, and hence has wide-ranging potential.

Oil-Water Interfacial-Directed Spontaneous Self-Assembly of Natural Quillaja Saponin for Controlling Interface Permeability in Colloidal Emulsions

Assembly of amphiphiles at the interface of two immiscible fluids is of great scientific and technological interest in offering efficient routes to smart vehicles for functional deliveries. Natural Quillaja saponin (QS) has gathered widespread interest within the scientific community as a result of its unique interfacial properties. Herein, spontaneously interface-driven self-assembly (SIDSA) of QS at the oil-water interface was systematically studied by morphology and spectroscopy. It was found to self-assemble into a micrometer-scale network in helical fibers by combined intermolecular π-π stacking and hydrogen bonding among saponins at the liquid-liquid interface. From SIDSA, multilayer films on the surfaces of dispersed droplets were formed and enhanced emulsion stability. Interfacial QS-based films on droplet surfaces were also shown to confine interfacial diffusion processes by serving as transport barriers. Furthermore, they can be exploited to control the release of volatiles from the dispersed liquid phase by regulating the interface film, which is shown by molecular dynamics to occur through a hydrogen-bonded mechanism. These results provide new insight into the interfacial assembly structure that can enable unique controllable release in a broad range of applications in food, beverages, pharmaceuticals, and cosmetics.

Enzymatic Noncovalent Synthesis

Enzymatic reactions and noncovalent (i.e., supramolecular) interactions are two fundamental nongenetic attributes of life. Enzymatic noncovalent synthesis (ENS) refers to a process where enzymatic reactions control intermolecular noncovalent interactions for spatial organization of higher-order molecular assemblies that exhibit emergent properties and functions. Like enzymatic covalent synthesis (ECS), in which an enzyme catalyzes the formation of covalent bonds to generate individual molecules, ENS is a unifying theme for understanding the functions, morphologies, and locations of molecular ensembles in cellular environments. This review intends to provide a summary of the works of ENS within the past decade and emphasize ENS for functions. After comparing ECS and ENS, we describe a few representative examples where nature uses ENS, as a rule of life, to create the ensembles of biomacromolecules for emergent properties/functions in a myriad of cellular processes. Then, we focus on ENS of man-made (synthetic) molecules in cell-free conditions, classified by the types of enzymes. After that, we introduce the exploration of ENS of man-made molecules in the context of cells by discussing intercellular, peri/intracellular, and subcellular ENS for cell morphogenesis, molecular imaging, cancer therapy, and other applications. Finally, we provide a perspective on the promises of ENS for developing molecular assemblies/processes for functions. This review aims to be an updated introduction for researchers who are interested in exploring noncovalent synthesis for developing molecular science and technologies to address societal needs.

Synthetic dimeric-drug phospholipid: a versatile liposomal platform for cancer therapy

An amphiphilic dimeric-podophyllotoxin (PODO) phospholipid was synthesized to assemble into liposomes as a combination of prodrug and nanocarrier. The results have demonstrated that the cell membrane-like delivery system possessed an improved cellular uptake and favorable antitumor efficacy with reduced side-effects. This strategy provides a new effective platform in drug delivery for cancer chemotherapy.

Lilypad aggregation: localised self-assembly and metal sequestration at a liquid-vapour interface

Spatially resolved soft materials, such as vesicles and microgels, have shown promise as selective adsorbents and microscale reaction vessels. However, spatiotemporal control of aggregation can be difficult to achieve. In this study, nickel(ii) chloride and a dipyridyl oligo(urea) ligand were combined in a vapour-diffusion setup to produce a localised spheroidal aggregate at the liquid-vapour interface. This aggregate forms via the self-assembly and fusion of monodisperse colloids and grows until its weight is no longer counterbalanced by surface tension. A simple physical model reveals that this process, termed lilypad aggregation, is possible only for surface energies that favour neither bulk aggregation nor the growth of an interfacial film. These surface energies dictate the final size and shape of the aggregate and may be estimated through visual monitoring of its changing morphology. Lilypad aggregates sequester metal from the surrounding sol and can be collected manually from the surface of the liquid.

Dipeptide Self-assembled Hydrogels with Shear-Thinning and Instantaneous Self-healing Properties Determined by Peptide Sequences

Dipeptide self-assembled hydrogels have potential biomedical applications because of their great biocompatibility, bioactivity, and tunable physicochemical properties, which can be modulated in the molecular level by design of amino acid sequences. Herein, a series of dipeptides (Fmoc-FL, -YL, -LL, and -YA) are designed to form shear-thinning hydrogels with self-healing and tunable mechanical properties by adjusting the synergetic effect of hydrophobic interactions (π-π stacking and hydrophobic effect) and hydrogen bonds of peptides through substitution of amino acid residues. The enhancement of hydrophobic interactions is a primary factor to promote mechanical rigidity of hydrogels, and strong hydrogen-bonding interactions between molecules contribute to the instantaneous self-healing property, which is supported by experimental studies (FTIR, CD, SEM, AFM, and rheology) and molecular dynamics simulations. The injectable dipeptide hydrogels were certified as an ideal endoscopic submucosal dissection filler to make operation convenient and secure in mice and living mini-pig's experiments with a longer duration time, higher stiffness, and lower inflammatory response than commercial clinical fillers.

Self-Assembling Supramolecular Hybrid Hydrogel Beads

With the goal of imposing shape and structure on supramolecular gels, we combine a low-molecular-weight gelator (LMWG) with the polymer gelator (PG) calcium alginate in a hybrid hydrogel. By imposing thermal and temporal control of the orthogonal gelation methods, the system either forms an extended interpenetrating network or core-shell-structured gel beads-a rare example of a supramolecular gel formulated inside discrete gel spheres. The self-assembled LMWG retains its unique properties within the beads, such as remediating PdII and reducing it in situ to yield catalytically active Pd0 nanoparticles. A single PdNP-loaded gel bead can catalyse the Suzuki-Miyaura reaction, constituting a simple and easy-to-use reaction-dosing form. These uniquely shaped and structured LMWG-filled gel beads are a versatile platform technology with great potential in a range of applications.

Widely Adaptable Oil-in-Water Gel Emulsions Stabilized by an Amphiphilic Hydrogelator Derived from Dehydroabietic Acid

A surfactant, R-6-AO, derived from dehydroabietic acid has been synthesized. It behaves as a highly efficient low-molecular-weight hydrogelator with an extremely low critical gelation concentration (CGC) of 0.18 wt % (4 mm). R-6-AO not only stabilizes oil-in-water (O/W) emulsions at concentrations above its critical micelle concentration (cmc) of 0.6 mm, but also forms gel emulsions at concentrations beyond the CGC with the oil volume fraction freely adjustable between 2 % and 95 %. Cryo-TEM images reveal that R-6-AO molecules self-assemble into left-handed helical fibers with cross-sectional diameters of about 10 nm in pure water, which can be turned to very stable hydrogels at concentrations above the CGC. The gel emulsions stabilized by R-6-AO can be prepared with different oils (n-dodecane, n-decane, n-octane, soybean oil, olive oil, tricaprylin) owing to the tricyclic diterpene hydrophobic structure in their molecules that enables them to adopt a unique arrangement in the fibers.