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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (31 October 2019) | Viewed by 45288

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Prof. Dr. Francesca D’Anna

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Dipartimento di Scienze e Tecnologie Biologiche, Università degli Studi di Palermo, Palermo, Italy
Interests: supramolecular chemistry; ionic liquids; supramolecular gels; hybrid supramolecular gels; biomass transformation; self-assembly processes
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Dr. Salvatore Marullo

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Dipartimento di Scienze e Tecnologie Biologiche, Università degli Studi di Palermo, Palermo, Italy
Interests: ionic liquids; supramolecular gels; biomass transformation; self-assembly processes
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Dr. Carla Rizzo

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Dipartimento di Scienze e Tecnologie Biologiche, Università degli Studi di Palermo, Palermo, Italy
Interests: ionic liquids; supramolecular gels; hybrid supramolecular gels; biomass transformation
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Special Issue Information

Dear Colleagues,

Supramolecular gels represent one of the new frontiers of materials chemistry. Built by the feeble and cooperative supramolecular interactions occurring among low molecular weight compounds (gelators), they are featured in 3D-networks able to immobilize solvents through the occurrence of capillary forces.

Their classification is solvent-based and together with more common organo- and hydrogels, i.e., gels formed in organic solvents or water; more recently ionogels, i.e., gels formed in ionic liquids, have also attracted researcher attention. In all cases, the gel texture proves more porous with respect to polymeric gels. Furthermore, they are frequently able to be restored after the action of external stimuli, such as pH changes, UV-vis irradiation, magnetic stirring or ultrasound irradiation. These abilities have significantly favored their application and currently they are applied in different fields, such as the pharmaceutical (as a drug carrier and matrix for drug crystallization), environmental (as a sorbent for pollutant removal), synthetic (as a reaction media) fields, etc.

This issue is aimed at collecting contributions on studies on the obtaining of gel phases and their characterization, in the attempt to better clarify the relationship between gelator, solvent nature and gel phase formation. On the other hand, investigations of the plethora of supramolecular gels applications will also be taken into account. The main goal of the issue is to shed light on the ongoing research on this topic.

Prof. Francesca D’Anna
Dr. Salvatore Marullo
Dr. Carla Rizzo
Guest Editors

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Keywords

hydrogels
organogels
ionogels
hybrid supramolecular gels
gel properties
gel applications

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Supramolecular Gel II in Molecules (6 articles)

Published Papers (10 papers)

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Research

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12 pages, 2252 KiB

Open AccessArticle

Tuning Mechanical Properties of Pseudopeptide Supramolecular Hydrogels by Graphene Doping

by Demetra Giuri, Marianna Barbalinardo, Nicola Zanna, Paolo Paci, Marco Montalti, Massimiliano Cavallini, Francesco Valle, Matteo Calvaresi and Claudia Tomasini

Molecules 2019, 24(23), 4345; https://doi.org/10.3390/molecules24234345 - 28 Nov 2019

Cited by 11 | Viewed by 2744

Abstract

Supramolecular hydrogels, obtained from small organic molecules, may be advantageous over polymeric ones for several applications, because these materials have some peculiar properties that differentiate them from the traditional polymeric hydrogels, such as elasticity, thixotropy, self-healing propensity, and biocompatibility. We report here the preparation of strong supramolecular pseudopeptide-based hydrogels that owe their strength to the introduction of graphene in the gelling mixture. These materials proved to be strong, stable, thermoreversible and elastic. The concentration of the gelator, the degree of graphene doping, and the nature of the trigger are crucial to get hydrogels with the desired properties, where a high storage modulus coexists with a good thixotropic behavior. Finally, NIH-3T3 cells were used to evaluate the cell response to the presence of the most promising hydrogels. The hydrogels biocompatibility remains good, if a small degree of graphene doping is introduced. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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10 pages, 1896 KiB

Open AccessFeature PaperArticle

On the Mechanical Properties of N-Functionalised Dipeptide Gels

by Ana M. Fuentes-Caparrós, Kate McAulay, Sarah E. Rogers, Robert M. Dalgliesh and Dave J. Adams

Molecules 2019, 24(21), 3855; https://doi.org/10.3390/molecules24213855 - 25 Oct 2019

Cited by 12 | Viewed by 3579

Abstract

The properties of a hydrogel are controlled by the underlying network that immobilizes the solvent. For gels formed by the self-assembly of a small molecule, it is common to show the primary fibres that entangle to form the network by microscopy, but it is difficult to access information about the network. One approach to understand the network is to examine the effect of the concentration on the rheological properties, such that G′∝ c^x, where G′ is the storage modulus and c is the concentration. A number of reports link the exponent x to a specific type of network. Here, we discuss a small library of gels formed using functionalized dipeptides, and describe the underlying networks of these gels, using microscopy, small angle scattering and rheology. We show that apparently different networks can give very similar values of x. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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17 pages, 2662 KiB

Open AccessFeature PaperArticle

Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification

by Dipankar Ghosh, Matthew T. Mulvee and Krishna K. Damodaran

Molecules 2019, 24(19), 3472; https://doi.org/10.3390/molecules24193472 - 25 Sep 2019

Cited by 13 | Viewed by 3777

Abstract

The factors affecting the self-assembly process in low molecular weight gelators (LMWGs) were investigated by tuning the gelation properties of a well-known gelator N-(4-pyridyl)isonicotinamide (4PINA). The N―H∙∙∙N interactions responsible for gel formation in 4PINA were disrupted by altering the functional groups of 4PINA, which was achieved by modifying pyridyl moieties of the gelator to pyridyl N-oxides. We synthesized two mono-N-oxides (INO and PNO) and a di-N-oxide (diNO) and the gelation studies revealed selective gelation of diNO in water, but the two mono-N-oxides formed crystals. The mechanical strength and thermal stabilities of the gelators were evaluated by rheology and transition temperature (T_gel) experiments, respectively, and the analysis of the gel strength indicated that diNO formed weak gels compared to 4PINA. The SEM image of diNO xerogels showed fibrous microcrystalline networks compared to the efficient fibrous morphology in 4PINA. Single-crystal X-ray analysis of diNO gelator revealed that a hydrogen-bonded dimer interacts with adjacent dimers via C―H∙∙∙O interactions. The non-gelator with similar dimers interacted via C―H∙∙∙N interaction, which indicates the importance of specific non-bonding interactions in the formation of the gel network. The solvated forms of mono-N-oxides support the fact that these compounds prefer crystalline state rather than gelation due to the increased hydrophilic interactions. The reduced gelation ability (minimum gel concentration (MGC)) and thermal strength of diNO may be attributed to the weak intermolecular C―H∙∙∙O interaction compared to the strong and unidirectional N―H∙∙∙N interactions in 4PINA. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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17 pages, 4493 KiB

Open AccessArticle

Enzyme Entrapment in Amphiphilic Myristyl-Phenylalanine Hydrogels

by Natashya Falcone, Tsuimy Shao, Roomina Rashid and Heinz-Bernhard Kraatz

Molecules 2019, 24(16), 2884; https://doi.org/10.3390/molecules24162884 - 08 Aug 2019

Cited by 13 | Viewed by 3827

Abstract

Supramolecular amino acid and peptide hydrogels are functional materials with a wide range of applications, however, their ability to serve as matrices for enzyme entrapment have been rarely explored. Two amino acid conjugates were synthesized and explored for hydrogel formation. These hydrogels were characterized in terms of strength and morphology, and their ability to entrap enzymes while keeping them active and reusable was explored. It was found that the hydrogels were able to successfully entrap two common and significant enzymes—horseradish peroxidase and α-amylase—thus keeping them active and stable, along with inducing recycling capabilities, which has potential to further advance the industrial biotransformation field. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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16 pages, 3264 KiB

Open AccessArticle

Carbon Nanomaterial Doped Ionic Liquid Gels for the Removal of Pharmaceutically Active Compounds from Water

by Carla Rizzo, Salvatore Marullo, Nadka Tz. Dintcheva and Francesca D’Anna

Molecules 2019, 24(15), 2788; https://doi.org/10.3390/molecules24152788 - 31 Jul 2019

Cited by 11 | Viewed by 2984

Abstract

Due to large drug consumption, pharmaceutically active compounds (PhACs) can be found as water contaminants. The removal of PhACs is a significant issue, as they can easily overtake traditional purification methods. Because of their surface properties, carbon nanomaterials are among the most efficient materials able to adsorb PhACs. However, their limitation is their recovery after use and their possible leakage into the aquatic system. Consequently, new hybrid supramolecular ionic liquid gels (HILGs) have been designed for the adsorption of some antibiotic drugs (ciprofloxacin and nalidixic acid) from water. The chemical–physical properties of gels, such as the temperature of the gel–sol transition, morphology, and rheology, have been studied for their use as sorbents. These properties influence the gel removal efficiency of PhAC, i.e., the best system is the gel that presents weaker colloidal forces. A fast removal (RE = 51%) is obtained in 3 h for ciprofloxacin, while a slower adsorption process is observed for nalidixic acid (RE = 88% in 24 h). HILGs can be recycled up to seven cycles and regenerated. In addition, they can be used with higher concentrations or volumes of PhAC and in a realistic apparatus like dialysis membranes. These peculiarities suggest that HILGs can be competitive with more complex sorbent systems. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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10 pages, 2575 KiB

Open AccessCommunication

Multicellular Co-Culture in Three-Dimensional Gelatin Methacryloyl Hydrogels for Liver Tissue Engineering

by Juan Cui, Huaping Wang, Qing Shi, Tao Sun, Qiang Huang and Toshio Fukuda

Molecules 2019, 24(9), 1762; https://doi.org/10.3390/molecules24091762 - 07 May 2019

Cited by 34 | Viewed by 4684

Abstract

Three-dimensional (3D) tissue models replicating liver architectures and functions are increasingly being needed for regenerative medicine. However, traditional studies are focused on establishing 2D environments for hepatocytes culture since it is challenging to recreate biodegradable 3D tissue-like architecture at a micro scale by using hydrogels. In this paper, we utilized a gelatin methacryloyl (GelMA) hydrogel as a matrix to construct 3D lobule-like microtissues for co-culture of hepatocytes and fibroblasts. GelMA hydrogel with high cytocompatibility and high structural fidelity was determined to fabricate hepatocytes encapsulated micromodules with central radial-type hole by photo-crosslinking through a digital micromirror device (DMD)-based microfluidic channel. The cellular micromodules were assembled through non-contact pick-up strategy relying on local fluid-based micromanipulation. Then the assembled micromodules were coated with fibroblast-laden GelMA, subsequently irradiated by ultraviolet for integration of the 3D lobule-like microtissues encapsulating multiple cell types. With long-term co-culture, the 3D lobule-like microtissues encapsulating hepatocytes and fibroblasts maintained over 90% cell viability. The liver function of albumin secretion was enhanced for the co-cultured 3D microtissues compared to the 3D microtissues encapsulating only hepatocytes. Experimental results demonstrated that 3D lobule-like microtissues fabricated by GelMA hydrogels capable of multicellular co-culture with high cell viability and liver function, which have huge potential for liver tissue engineering and regenerative medicine applications. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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11 pages, 5390 KiB

Open AccessArticle

Microfluidics-Based Fabrication of Cell-Laden Hydrogel Microfibers for Potential Applications in Tissue Engineering

by Gen Wang, Luanluan Jia, Fengxuan Han, Jiayuan Wang, Li Yu, Yingkang Yu, Gareth Turnbull, Mingyu Guo, Wenmiao Shu and Bin Li

Molecules 2019, 24(8), 1633; https://doi.org/10.3390/molecules24081633 - 25 Apr 2019

Cited by 26 | Viewed by 4191

Abstract

Fibrous hydrogel scaffolds have recently attracted increasing attention for tissue engineering applications. While a number of approaches have been proposed for fabricating microfibers, it remains difficult for current methods to produce materials that meet the essential requirements of being simple, flexible and bio-friendly. It is especially challenging to prepare cell-laden microfibers which have different structures to meet the needs of various applications using a simple device. In this study, we developed a facile two-flow microfluidic system, through which cell-laden hydrogel microfibers with various structures could be easily prepared in one step. Aiming to meet different tissue engineering needs, several types of microfibers with different structures, including single-layer, double-layer and hollow microfibers, have been prepared using an alginate-methacrylated gelatin composite hydrogel by merely changing the inner and outer fluids. Cell-laden single-layer microfibers were obtained by subsequently seeding mouse embryonic osteoblast precursor cells (MC3T3-E1) cells on the surface of the as-prepared microfibers. Cell-laden double-layer and hollow microfibers were prepared by directly encapsulating MC3T3-E1 cells or human umbilical vein endothelial cells (HUVECs) in the cores of microfibers upon their fabrication. Prominent proliferation of cells happened in all cell-laden single-layer, double-layer and hollow microfibers, implying potential applications for them in tissue engineering. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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13 pages, 1523 KiB

Open AccessArticle

How Humic Acids Affect the Rheological and Transport Properties of Hydrogels

by Martina Klucakova, Jiri Smilek and Petr Sedlacek

Molecules 2019, 24(8), 1545; https://doi.org/10.3390/molecules24081545 - 19 Apr 2019

Cited by 12 | Viewed by 2957

Abstract

Humic acids are often regarded as substances with a supramolecular structure which plays an important role in Nature. Their addition into hydrogels can affect their behavior and functioning in different applications. This work is focused on the properties of widely-used hydrogel based on agarose after addition of humic acids–the protonated H-form of humic acids and humic acids with methylated carboxylic groups. Hydrogels enriched by humic acids were studied in terms of their viscoelastic and transport properties. Rotational rheometry and methods employing diffusion cells were used in order to describe the influence of humic acids on the properties and behavior of hydrogels. From the point of view of rheology the addition of humic acids mainly affected the loss modulus corresponding to the relaxation of hydrogel connected with its flow. In the case of diffusion experiments, the transport of dyes (methylene blue and rhodamine) and metal ions (copper and nickel) through the hydrogel was affected by interactions between humic acids and the diffusion probes. The time lag in the hydrogel enriched by humic acids was prolonged for copper, methylene blue and rhodamine. In contrast, the presence of humic acids in hydrogel slightly increased the mobility of nickel. The strongest influence of the methylation of humic acids on diffusion was observed for methylene blue. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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15 pages, 6308 KiB

Open AccessArticle

Biodegradable and pH Sensitive Peptide Based Hydrogel as Controlled Release System for Antibacterial Wound Dressing Application

by Jie Zhu, Hua Han, Ting-Ting Ye, Fa-Xue Li, Xue-Li Wang, Jian-Yong Yu and De-Qun Wu

Molecules 2018, 23(12), 3383; https://doi.org/10.3390/molecules23123383 - 19 Dec 2018

Cited by 55 | Viewed by 6771 | Correction

Abstract

The stimuli-sensitive and biodegradable hydrogels are promising biomaterials as controlled drug delivery systems for diverse biomedical applications. In this study, we construct hybrid hydrogels combined with peptide-based bis-acrylate and acrylic acid (AAc). The peptide-based bis-acrylate/AAc hybrid hydrogel displays an interconnected and porous structure by scanning electron microscopy (SEM) observation and exhibits pH-dependent swelling property. The biodegradation of hybrid hydrogels was characterized by SEM and weight loss, and the results showed the hydrogels have a good enzymatic biodegradation property. The mechanical and cytotoxicity properties of the hydrogels were also tested. Besides, triclosan was preloaded during the hydrogel formation for drug release and antibacterial studies. In summary, the peptide-based bis-acrylate/AAc hydrogel with stimuli sensitivity and biodegradable property may be excellent candidates as drug delivery systems for antibacterial wound dressing application. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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Review

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22 pages, 480 KiB

Open AccessReview

Chemically Responsive Hydrogel Deformation Mechanics: A Review

by Eanna Fennell and Jacques M. Huyghe

Molecules 2019, 24(19), 3521; https://doi.org/10.3390/molecules24193521 - 28 Sep 2019

Cited by 24 | Viewed by 8959

Abstract

A hydrogel is a polymeric three-dimensional network structure. The applications of this material type are diversified over a broad range of fields. Their soft nature and similarity to natural tissue allows for their use in tissue engineering, medical devices, agriculture, and industrial health products. However, as the demand for such materials increases, the need to understand the material mechanics is paramount across all fields. As a result, many attempts to numerically model the swelling and drying of chemically responsive hydrogels have been published. Material characterization of the mechanical properties of a gel bead under osmotic loading is difficult. As a result, much of the literature has implemented variants of swelling theories. Therefore, this article focuses on reviewing the current literature and outlining the numerical models of swelling hydrogels as a result of exposure to chemical stimuli. Furthermore, the experimental techniques attempting to quantify bulk gel mechanics are summarized. Finally, an overview on the mechanisms governing the formation of geometric surface instabilities during transient swelling of soft materials is provided. Full article

(This article belongs to the Special Issue Supramolecular Gel)

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