Supramolecular hydrogels of self-assembled zwitterionic-peptides

Zwitterionic polymer materials have been extensively studied, but zwitterionic peptides supramolecular hydrogel materials are rarely studied. In this study, the preparation of two zwitterionic hydrogels using self-assembled peptides were reported. The hydrogels could be fabricated easily by changing the temperature or enzyme catalysis in a short time. And the differences in structure and function of the zwitterion peptide hydrogels caused by the two preparation methods were also be compared. We found that the hydrogel prepared by enzyme induced self-assembly has better solubility and lower cytotoxicity than that prepared by the heating-cooling process. The result showed the enzyme induced self-assembly way to form zwitterionic peptides supramolecular hydrogel materials could have further biomedical applications.     

Supramolecular hydrogels respond to ligand-receptor interaction

N-(Fluorenyl-9-Methoxycarbonyl) dipeptides form supramolecular hydrogels via hydrogen bonding and hydrophobic interactions. These hydrogels respond to a ligand-receptor interaction as well as to thermal or pH perturbation and also exhibit chiral recognition.     

Supramolecular hydrogels based on beta-amino acid derivatives

Here we report on a new class of supramolecular hydrogels based on dipeptides that consist of beta-amino acids, which may confer proteolytic resistance to the hydrogels for biomedical applications.     

Supramolecular hydrogels containing inorganic salts and acids

l-Lysine-based hydrogelators can form supramolecular hydrogels over a wide pH range and contain inorganic salts and acids, especially, 3 forms hydrogels containing 1 M HCl and H₂SO₄ at 1 g/L.     

Enzyme-responsive polymeric assemblies, nanoparticles and hydrogels

Being responsive and adaptive to external stimuli is an intrinsic feature characteristic of all living organisms and soft matter. Specifically, responsive polymers can exhibit reversible or irreversible changes in chemical structures and/or physical properties in response to a specific signal input such as pH, temperature, ionic strength, light irradiation, mechanical force, electric and magnetic fields, and analyte of interest (e.g., ions, bioactive molecules, etc.) or an integration of them. The past decade has evidenced tremendous growth in the fundamental research of responsive polymers, and accordingly, diverse applications in fields ranging from drug or gene nanocarriers, imaging, diagnostics, smart actuators, adaptive coatings, to self-healing materials have been explored and suggested. Among a variety of external stimuli that have been utilized for the design of novel responsive polymers, enzymes have recently emerged to be a promising triggering motif. Enzyme-catalyzed reactions are highly selective and efficient toward specific substrates under mild conditions. They are involved in all biological and metabolic processes, serving as the prime protagonists in the chemistry of living organisms at a molecular level. The integration of enzyme-catalyzed reactions with responsive polymers can further broaden the design flexibility and scope of applications by endowing the latter with enhanced triggering specificity and selectivity. In this tutorial review, we describe recent developments concerning enzyme-responsive polymeric assemblies, nanoparticles, and hydrogels by highlighting this research area with selected literature reports. Three different types of systems, namely, enzyme-triggered self-assembly and aggregation of synthetic polymers, enzyme-driven disintegration and structural reorganization of polymeric assemblies and nanoparticles, and enzyme-triggered sol-to-gel and gel-to-sol transitions, are described. Their promising applications in drug controlled release, biocatalysis, imaging, sensing, and diagnostics are also discussed.     

Supramolecular hydrogels for enzymatically triggered self-immolative drug delivery

For the first time the combination of self-immolative spacers and supramolecular hydrogels has been tested in enzyme triggered drug release. Low-molecular weight drug-gelator conjugates have been prepared, which contain a gel forming lysine moiety linked to model drugs (benzylamine and phenethylamine) through a self-immolating spacer (p-aminobenzyloxycarbonyl). In the presence of trypsin the amide linkage between the gelator moiety and the spacer is hydrolyzed leading to the release of the model drug. This approach provides with distinct advantages, such as sustained release or versatility associated to the use of supramolecular hydrogels and self-immolative spacers, respectively.     

Structural features of polymeric silicon glycerolate hydrogels

Structural features of polymeric silicon glycerolate hydrogels based on tetrafunctional silicon glycerolates were investigated using model process, namely, hydrolytic transformation of difunctional silicon glycerolates, by IR and ¹H NMR spectroscopy, elemental analysis, atomic emission spectrometry. The possibility of forming a polymer network containing Si—O—Si and Si—OCH₂CH(OH)CH₂O—Si fragments was demonstrated. The molecular weight of the sub-chains in the network was calculated using Flory—Rehner approach based on the mechanical properties of the swollen network of flexible polymeric chains.     

Synthesis of polymeric hydrogels containing sulfonate group

The copolymerization of n‐dodecyl poly(oxyethylene)600 maleate (DPM‐13) with 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) has been studied in the range from 25 to 90 % DPM‐13 in the feed stock. The reactivity ratio has been determined for DPM‐13/AMPS copolymer. The copolymer compositions, utilized for determining the reactivity ratio, have been determined from nitrogen content and ¹H nuclear magnetic resonance (NMR) analysis. The copolymer was characterized by IR and ¹H‐NMR. Crosslinked poly(AMPS) and DPM‐13/AMPS copolymers were prepared in water in the presence of potassium persulfate as initiator, and 1,1‐trimethylolpropane trimethacrylate (TPT) as hexafunctional crosslinker. The percentage of TPT was varied from 0.4 to 2 wt% to study the effect of TPT content on the swelling properties of the prepared polymers. Copyright © 1999 John Wiley & Sons, Ltd.     

Supramolecular self-assembly induced graphene oxide based hydrogels and organogels

We demonstrate the construction of three-dimensional graphene oxide based gel networks through the self-assembly of a series of amphiphilic molecules, which possess a polar carbohydrate headgroup attached to a nonpolar pyrene group. The gelation process can occur in both aqueous and organic solutions and be influenced by the gelators' molecular structure. The driving forces for the gelation process were determined as π-π stacking and hydrogen bonding interaction by using fluorescence and infrared spectroscopies. Rheometry was used to investigate the mechanical properties of the hydrogels and the organogels. The hydrogel was investigated to be applied to remove dye from aqueous solution.     

Supramolecular hydrogels based on the epitope of potassium ion channels

Imparting aromatic-aromatic interactions to the potassium binding epitope affords a supramolecular hydrogelator that responds to the K(+) concentration by self-assembly into nanofibers of different widths and crosslinking patterns, which illustrates a simple approach to generate biomimic materials based on tunable, hierarchical self-assembly of small molecules.     

Supramolecular hydrogels based on short peptides linked with conformational switch

Short peptides appropriately linked with an azobenzene conformational switch were found to be motif and pH dependant supramolecular hydrogelators. The hydrogelation properties of the short peptides linked with the conformational switch were studied in detail with respect to dependence on amino acid residue, pH and salt effect. The presence of amino acids with aromatic side chains such as Phe and Tyr was found to be favorable for the short peptides to gel water at an appropriate pH range. Cationic amino acid residues such as Arg and Lys in the short peptides were found to be unfavorable for hydrogelation. pH and salt effect were also found to be important factors for the hydrogelation properties of the short peptides. A series of short peptides with bioactive sequences were linked with the conformational switch and their hydrogelation properties were investigated. Photoresponsive supramolecular hydrogels were realized based on the E-/Z- transition of the conformational switch upon light irradiation. Proper combination of amino acid residues in the short peptides resulted in smart supramolecular hydrogels with responses to multiple stimuli.     

Supramolecular polymeric complexes of calix[8]arenes

Formation of ionic complexes of calix[8]arenes with polymers of various basicities was studied, and previously unknown ternary polymeric complexes of calix[8]arenes of the ion-ion (polymer-calixarene-uranyl ion) and ion-hydrophilic molecule-hydrophobic molecule (polymer-calixarene-fullerene) types were prepared.     

Dehydration of polymeric hydrogels designed for gelcasting method in ceramics

Key issue in the gelcasting method is the way water is released from the ceramic–hydrogel system. It is the first step to the formation of ceramic materials called green body. The purpose of the presented investigations is to establish the range of temperatures in which dehydration of the various hydrogels takes place, and at what temperatures the eight prepared hydrogels are disintegrated. The set of hydrogels polymers was obtained by radical polymerization from ionic and non-ionic monomers. The polymers were solved in water causing formation of clear gels. The dehydration and thermal decomposition of the obtained hydrogel samples was studied using thermal analysis techniques. The amount of water contained in hydrogels was determined as well as the temperature and products of polymer disintegration. Enthalpies of dewatering were also determined.     

Impact of polymeric films and hydrogels: Physical characteristics on bacterial growth

Hydrogels find diverse applications in manipulating bacteria, and serving purposes like elevation, maintenance, and elimination. Several factors of hydrogel have been studied in the benefits of antibacterial activity. Factors such as hydrogel stiffness and roughness gain significance in surface coating, influencing bacterial behavior. However, the intricate interplay of hydrogel stiffness, roughness, polymer types, and bacterial species necessitates further exploration. The choice of polymer is dictated by the specific objectives, particularly in antibacterial scenarios where polymers with positive charge, hydrophilicity, and acidity prove effective. These properties induce robust electrostatic and hydrophobic/hydrophilic interactions, along with pH-induced cell membrane damage, collectively contributing to hindered bacterial adhesion and growth. Additionally, extracellular polymeric substances (EPS) emerge as pivotal influencers in bacterial adhesion and proliferation. EPS production alters bacterial surfaces, fostering connections between bacteria and facilitating biofilm formation. The hydrophobic nature of EPS further complicates bacterial interactions with surface materials, emphasizing the nuanced interplay of hydrophilic and hydrophobic forces in bacterial adhesion. Herein, this work article has reviewed the related study of each physical property related to antibacterial property on the surface of the hydrogel. Moreover, this work also illustrates applications of the antibacterial properties of hydrogel for medical and surface treatment, including wound healing, food packaging, and surface coating. Additionally, the bacteria growing on hydrogel for engineered living materials, have been updated in various applications.     

Adsorption and controlled release of Chlortetracycline HCl by using multifunctional polymeric hydrogels

Adsorption and controlled release of Chlortetracycline HCl to and from multifunctional polymeric materials (HEMA/MAA) hydrogels were investigated. P(HEMA/MAA) hydrogels were synthesized by gamma radiation-induced copolymerization of 2-hydroxyethylmethacrylate (HEMA) and methacrylic acid (MAA) in aqueous solution. The influence of copolymer composition and pH value of the surrounding medium on the type of water diffusion into the glassy polymer were discussed. Drug, Chlortetracycline HCl containing hydrogels, with different drug concentration to polymer ratios, was loaded by direct adsorption method. The influence of MAA content in the gel on the adsorption capacities of hydrogel was studied. Chlortetracycline HCl adsorption capacity of hydrogels was found to increase from 8 to 138 mg Chlortetracycline HCl per gram dry gel with increasing amount of MAA in the gel system and drug concentration. The effect of pH on the releasing behavior of Chlortetracycline HCl from gel matrix was investigated. In vitro drug release studies in different buffer solutions show that the basic parameters affecting the drug release behavior of hydrogel are the pH of the solution and MAA content of hydrogel.     

Ion-induced white-light-emitting polymeric hydrogels with high mechanical strength and reversible stimuli-responsive properties

We have developed a facile strategy to fabricate model multicolor hydrogels via a straightforward mixing process of poly acrylonitrile-grafted methacrylamide (PANMAM), polymethacrylic acid (PMAA) and doped lanthanide (Eu/Tb) and zinc ions to form the interpenetrating dual-polymer gel networks. The hydrogels exhibit excellent tunability of multi-spectrum emission colors (including white light) by simply varying the stoichiometry of metal ions. Furthermore, taking the advantage of different metal ion response mechanisms, we have demonstrated the reversible acidity/alkalinity stimuli-responsive behaviors of white-light-emitting hydrogel (WLE gel). Meanwhile, the unique cross-linked network formed through hydrogen-bonding, metal-ligand coordination and ionic interaction is introduced to achieve favorable mechanical strength of hydrogels. These properties enable the possibility in obtaining fluorescent patterns on hydrogels, which are promising candidate for encrypted information with improved security.     

Recent progress in the shape deformation of polymeric hydrogels from memory to actuation

Shape deformation hydrogels, which are one of the most promising and essential classes of stimuli-responsive polymers, could provide large-scale and reversible deformation under external stimuli. Due to their wet and soft properties, shape deformation hydrogels are anticipated to be a candidate for the exploration of biomimetic materials, and have shown various potential applications in many fields. Here, an overview of the mechanisms of shape deformation hydrogels and methods for their preparation is presented. Some innovative and efficient strategies to fabricate programmable deformation hydrogels are then introduced. Moreover, successful explorations of their potential applications, including information encryption, soft robots and bionomic systems, are discussed. Finally, remaining great challenges including the achievement of multiple stable deformation states and the combination of shape deformation and sensing are highlighted.

Shape deformation hydrogels, which are one of the most promising and essential classes of stimuli-responsive polymers, could provide large-scale and reversible deformation under external stimuli.