Gum Arabic: A promising candidate for the construction of physical hydrogels exhibiting highly stretchable, self-healing and tensility reinforcing performances

Drug delivery using reduction-responsive hydrogel based on carboxyethyl-succinoglycan with highly improved rheological, antibacterial, and antioxidant properties

The development of exopolysaccharide-based polymers is gaining increasing attention in various industrial biotechnology fields for materials such as thickeners, texture modifiers, anti-freeze agents, antioxidants, and antibacterial agents. High-viscosity carboxyethyl-succinoglycan (CE-SG) was directly synthesized from succinoglycan (SG) isolated from Sinorhizobium meliloti Rm 1021, and its structural, rheological, and physiological properties were investigated. The viscosity of CE-SG gradually increased in proportion to the degree of carboxyethylation substitution. In particular, when the molar ratio of SG and 3-chloropropionic acid was 1:100, the viscosity was significantly improved by 21.18 times at a shear rate of 10 s-1. Increased carboxyethylation of SG also improved the thermal stability of CE-SG. Furthermore, the CE-SG solution showed 90.18 and 91.78 % antibacterial effects against Escherichia coli and Staphylococcus aureus and effective antioxidant activity against DPPH and hydroxyl radicals. In particular, CE-SG hydrogels coordinated with Fe3+ ions, which improved both viscosity and rheological properties, while also exhibiting reduction-responsive drug release through 1,4-dithiothreitol. The results of this study suggest that SG derivatives, such as CE-SG, can be used as functional biomaterials in various fields such as food, cosmetics, and pharmaceutical industries.

Preparation and antitumor study of intelligent injectable hydrogel: Carboxymethyl chitosan-aldehyde gum Arabic composite graphene oxide hydrogel

In this study, we used polyaldehyde gum Arabic (OGA) and carboxymethyl chitosan (CMCS) as a gel matrix to form an injectable self-healing hydrogel by Schiff-base bonding. Further, graphene oxide (GO) was loaded with doxorubicin (DOX) to the hydrogel, which resulted in a CMCS-OGA/GO@DOX hydrogel. We achieved a DOX drug loading capacity of 43.80 ± 1.13 %. Rheological studies showed that GO hydrogels have improved mechanical properties. The in vitro release profile showed pH responsiveness with 88.21 % DOX release at pH 5.5. Biocompatibility studies showed that the hydrogel composition had good cytocompatibility with L929 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed a cell survival rate of 93.88 % within 48 h. The DOX-loaded hydrogel exhibited higher cell mortality in breast cancer cells (4 T1), with an inhibition rate of 79.4 % at 48 h. Acridine orange/ethidium bromide staining experiments on 4 T1 cells showed that when loaded with the same DOX concentration, the hydrogel significantly reduced the toxic effects on normal cells, whereas it had significant cytotoxic effects on cancer cells. This result indicates that the prepared GO hydrogel drug delivery system can serve as a novel approach for localized breast cancer treatment.

Self-healing hydrogels based on biological macromolecules in wound healing: A review

The complete healing of skin wounds has been a challenge in clinical treatment. Self-healing hydrogels are special hydrogels formed by distinctive physicochemically reversible bonds, and they are considered promising biomaterials in the biomedical field owing to their inherently good drug-carrying capacity as well as self-healing and repair abilities. Moreover, natural polymeric materials have received considerable attention in skin tissue engineering owing to their low cytotoxicity, low immunogenicity, and excellent biodegradation rates. In this paper, we review recent advances in the design of self-healing hydrogels based on natural polymers for skin-wound healing applications. First, we outline a variety of natural polymers that can be used to construct self-healing hydrogel systems and highlight the advantages and disadvantages of different natural polymers. We then describe the principle of self-healing hydrogels in terms of two different crosslinking mechanisms-physical and chemical-and dissect their performance characteristics based on the practical needs of skin-trauma applications. Next, we outline the biological mechanisms involved in the healing of skin wounds and describe the current application strategies for self-healing hydrogels based on these mechanisms. Finally, we analyze and summarize the challenges and prospects of natural-material-based self-healing hydrogels for skin applications.

Genipin versus Ferric Chloride cross-linked unmodified Gum Arabic/Chitosan/nano-Hydroxyapatite nanocomposite hydrogels as potential scaffolds for bone regeneration

Ferric chloride (FeCl3) and Genipin were utilized as cross-linkers to create two types of nanocomposite hydrogels through physical and covalent cross-linking methods, respectively. The hydrogels were composed of unmodified Gum Arabic (GA), Chitosan (Ch), and natural nano-Hydroxyapatite (nHA) using an acrylic acid solvent. Both the natural nHA and the FeCl3 vs. genipin cross-linked GA/Ch/nHA nano-composite hydrogels were prepared and characterized using various in vitro and in vivo analysis techniques. The use of FeCl3 and genipin cross-linkers resulted in the formation of novel hydrogels with compressive strengths of (15.43-22.20 MPa), which are comparable to those of natural cortical bone. In vivo evaluation was conducted by creating calvarial defects (6 mm) in Sprague-Dawley male rats. The results showed the formation of new, full-thickness bone at the implantation sites in all groups, as evidenced by digital planar tomography and histological staining with Hematoxylin and Eosin stain (H & E). Additionally, the use of genipin as a cross-linker positively affected the hydrogel's hydrophilicity and porosity. These findings justify further investigation into the potential of these nanocomposite hydrogels for bone regeneration applications.

Biodegradable Gel Electrolyte Suppressing Water-Induced Issues for Long-Life Zinc Metal Anodes

Owing to the inherent properties of aqueous electrolytes, aqueous zinc-ion batteries are considered to be a promising energy storage system. Unfortunately, the water-induced issues, such as hydrogen evolution and corrosion reaction, inevitably occur on the Zn anode surface during cycling, which leads to poor electrochemical performance. The gel polymer electrolyte would reduce the parasitic reactions associated with water. However, the nondegradable polymer is harmful to the environment. Herein, with the aim to alleviate the serious issues derived from water and environmental problems, a biodegradable gum arabic has been proposed to serve as a hydrogel electrolyte for aqueous zinc-ion batteries. The electrochemical activity of water could be reduced by the hydrogen-bond network between the gum arabic and water. Thus, the corrosion and hydrogen evolution reaction (HER) can be restrained by employing the prepared gel electrolyte. Evidenced by the online mass spectrometry, it is found that the less produced H₂ is detected in the biodegradable gel electrolyte-based Zn||Zn symmetric cell during the processes of Zn plating/stripping, showing the inhibited HER. Moreover, the by-product on the Zn anode is barely observed during cycling when using the obtained gel electrolyte. Uniform zinc-ion distribution can be achieved to mitigate Zn dendrite growth in the gel electrolyte. Therefore, the Zn||Zn symmetric cell based on the gel electrolyte exhibits a long lifespan of more than 1300 h, which is longer than that in the aqueous electrolyte. Moreover, the Zn||LiFePO₄ hybrid ion battery based on the gel electrolyte shows improved capacity retention by suppressing the reactions related to water.

Unmodified Gum Arabic/Chitosan/Nanohydroxyapatite Nanocomposite Hydrogels as Potential Scaffolds for Bone Regeneration

In this work, physical cross-linking was used to create nanocomposite hydrogels composed of unmodified gum arabic (GA), chitosan (Ch), and natural nanohydroxyapatite (nHA), using an acrylic acid (AA) solvent. Different GA/chitosan contents (15%, 25%, and 35% of the used AA) as well as different nHA contents (2, 5, and 10 wt.%), were used and studied. The natural nHA and the fabricated GA/Ch/nHA nanocomposite hydrogels were characterized using different analysis techniques. Using acrylic acid solvent produced novel hydrogels with compressive strength of 15.43–22.20 MPa which is similar to that of natural cortical bone. The addition of natural nHA to the hydrogels resulted in a significant improvement in the compressive strength of the fabricated hydrogels. In vitro studies of water absorption and degradation—and in vivo studies—confirmed that the nanocomposite hydrogels described here are biodegradable, biocompatible, and facilitate apatite formation while immersed in the simulated body fluid (SBF). In light of these findings, the GA/Ch/nHA nanocomposite hydrogels are recommended for preparing bioactive nanoscaffolds for testing in bone regeneration applications.

A novel self-healing triple physical cross-linked hydrogel for antibacterial dressing

The poor mechanical properties of wound dressings have always been a challenge in their application as wound protective barriers. In particular, when the hydrogel dressing absorbs the tissue fluid, the mechanical properties of the hydrogel will decrease greatly due to the swelling effect. In this study, an original antibacterial hydrogel dressing was prepared by a one-step process with acrylic acid, 1-vinyl-3-butylimidazolium, COOH-modified gum arabic, and aluminium chloride. The mechanical properties of this hydrogel were improved after water absorption due to hydrophobic interactions, so the hydrogel dressing could maintain good mechanical properties after absorption of the tissue fluid. Furthermore, 1-vinyl-3-butylimidazolium as an ionic liquid was introduced into the polymer backbone of hydrogels via covalent bonds and could promote the self-healing of hydrogels by facilitating the migration of aluminum ions with charge. The obtained hydrogels showed good self-healing properties, with a strain self-healing rate of 98.2% and a stress self-healing rate of 92.3%. In addition, this hydrogel exhibited excellent antibacterial activity against E. coli, S. aureus, and C. albicans. The results of the study on rat wound closure indicated that this hydrogel effectively accelerated the healing of a full-thickness skin defect. Therefore, this novel hydrogel has a broad application prospect in the field of wound dressing.

Vehiculation of Methyl Salicylate from Microcapsules Supported on Textile Matrix

In recent years, textile industries have focused their attention on the development of functional finishing that presents durability and, consequently, controlled release. However, in the case of methyl salicylate microcapsules supported on a textile matrix, studies indicate only the interactions between substrate and microcapsules and the drug delivery system, not applying the release equations. This study reports the mechanism and kinetics of controlled release of microcapsules of gelatin and gum Arabic containing methyl salicylate as active ingredient incorporated into textile matrices. According to the results presented, it was possible to verify that the wall materials participated in the coacervation process, resulting in microcapsules with well-defined geometry, besides promoting the increase of the thermal stability of the active principle. The samples (100% cotton, CO, and 100% polyamide, PA) functionalized with microcapsules released methyl salicylate in a controlled manner, based on the adjustment made by the Korsmeyer–Peppas model, indicating a Fickian mechanism. The influence of temperature was noticeable when the samples were subjected to washing, since with higher temperature (50 °C), the release was more pronounced than when subjected to lower temperature (37 °C). The results presented in this study indicate that the mechanism of backbone release is influenced by the textile matrix and by the durability of the microcapsule during the wash cycles.

Self-Healing and Injectable Hydrogels for Anticancer Drug Delivery: A Study with Multialdehyde Gum Arabic and Succinic Anhydride Chitosan

Gum arabic with multialdehyde groups (GAMA) was synthesized and utilized as a naturally derived macromolecular and nontoxic cross-linker to develop biocompatible and smart succinic anhydride-modified chitosan (SCS)-based injectable hydrogels for the first time. Aqueous solutions of GAMA and SCS were mixed at 37 °C to obtain hydrogels through pH-responsive, dynamic, and biodegradable Schiff base linkages. The effect of concentration of GAMA on hydrogel stiffness, swelling, morphology, and drug release behavior was investigated. These hydrogels exhibited outstanding self-healing and mechanical properties. Nanocurcumin as a chemotherapeutic agent was synthesized and loaded into these hydrogels for release studies carried out at pH 7.4 and 5.5. MTT assay revealed that these hydrogels are nontoxic to human embryonic kidney cell line (HEK-293). Loaded hydrogels demonstrated significant cytotoxicity against breast cancer cell line (MCF-7). Thus, the present strategy may find promising application for controlled delivery of anticancer drugs for treating locally accessible cancers.

A novel xanthan gum-based conductive hydrogel with excellent mechanical, biocompatible, and self-healing performances

Tough and conductive hydrogels are promising materials for various applications. However, it remains a great challenge to develop an integrated hydrogel combining outstanding mechanical, conductive, and self-healing performances. Herein, we prepared a conductive, self-healing, and tough hydrogel by constructing synergistic multiple interaction among montmorillonite (MMT), Poly (acrylamide-co-acrylonitrile) (P(AAm-co-AN)), xanthan gum (XG) and ferric ion (Fe³⁺). The obtained xanthan gum/montmorillonite/Poly (acrylamide-co-acrylonitrile) (XG/MMT/PAAm) hydrogels showed high strain stress (0.48 MPa) and compressive stress (5.9 MPa) as well as good shape recovery after multiple loading-unloading cycle tests. Moreover, the XG/MMT/PAAm hydrogels have distinctive features such as remarkable resistance to fatigue and harsh environments, insensitivity to notch, conductive, biocompatible, pH-dependent swelling behaviors and self-healing. Therefore, the as-fabricated hydrogel delivers a new prospect for its applications in various fields, such as flexible conductive device and tissue engineering.

Periodate-Modified Gum Arabic Cross-linked PVA Hydrogels: A Promising Approach toward Photoprotection and Sustained Delivery of Folic Acid

The chemically oxidized gum arabic was prepared and used as a naturally derived nontoxic and pH-responsive cross-linker to develop smart polyvinyl alcohol (PVA)-based hydrogels for the first time. The formulated hydrogels exhibited high mechanical properties, good porosity, and pH sensitivity, which facilitated their application as promising biomaterials for sustained delivery of folic acid. Further, the synthesized cross-linked PVA hydrogels displayed no cytotoxicity toward the human embryonic kidney cell line and exhibited higher blood compatibility. The hydrolytic degradation study confirmed their biodegradable nature. While the sustained delivery along with photoprotective properties of these hydrogels confirmed their multifunctional characteristics, these results suggest that these hydrogels may act as an efficient photoprotective material and find their application in the field of drug delivery.

A Highly Stretchable, Tough, Fast Self-Healing Hydrogel Based on Peptide⁻Metal Ion Coordination

Metal coordination bonds are widely used as the dynamic cross-linkers to construct self-healing hydrogels. However, it remains challenging to independently improve the toughness of metal coordinated hydrogels without affecting the stretchability and self-healing properties, as all these features are directly correlated with the dynamic properties of the same metal coordination bonds. In this work, using histidine-Zn2+ binding as an example, we show that the coordination number (the number of binding sites in each cross-linking ligand) is an important parameter for the mechanical strength of the hydrogels. By increasing the coordination number of the binding site, the mechanical strength of the hydrogels can be greatly improved without sacrificing the stretchability and self-healing properties. By adjusting the peptide and Zn2+ concentrations, the hydrogels can achieve a set of demanding mechanical features, including the Young's modulus of 7-123 kPa, fracture strain of 434-781%, toughness of 630-1350 kJ m-3, and self-healing time of ~1 h. We anticipate the engineered hydrogels can find broad applications in a variety of biomedical fields. Moreover, the concept of improving the mechanical strength of metal coordinated hydrogels by tuning the coordination number may inspire the design of other dynamically cross-linked hydrogels with further improved mechanical performance.

Nanoparticle-Hydrogel Composites: From Molecular Interactions to Macroscopic Behavior

Hydrogels are materials used in a variety of applications, ranging from tissue engineering to drug delivery. The incorporation of nanoparticles to yield composite hydrogels has gained substantial momentum over the years since these afford tailor-making and extend material mechanical properties far beyond those achievable through molecular design of the network component. Here, we review different procedures that have been used to integrate nanoparticles into hydrogels; the types of interactions acting between polymers and nanoparticles; and how these underpin the improved mechanical and optical properties of the gels, including the self-healing ability of these composite gels, as well as serving as the basis for future development. In a less explored approach, hydrogels have been used as dispersants of nanomaterials, allowing a larger exposure of the surface of the nanomaterial and thus a better performance in catalytic and sensor applications. Furthermore, the reporting capacity of integrated nanoparticles in hydrogels to assess hydrogel properties, such as equilibrium swelling and elasticity, is highlighted.

Fabrication and Characterization of Starch Nanohydrogels via Reverse Emulsification and Internal Gelation

Biopolymer-based nanohydrogels have great potential for various applications, including in food, nutraceutical, and pharmaceutical industries. Herein, starch nanohydrogels were prepared for the first time via reverse emulsification coupled with internal gelation. The effects of starch type (normal corn, potato, and pea starches), amylose content, and gelation time on the structural, morphological, and physicochemical properties of starch nanohydrogels were investigated. The diameter of starch nanohydrogel particles was around 100 nm after 12 h of retrogradation time. The relative crystallinity and thermal properties of starch nanohydrogels increased gradually with an increasing amylose content and gelation time. The swelling behavior of starch nanohydrogels was dependent upon the amylose content, and the swelling ratios were between 2.0 and 14.0, with the pea starch nanogels exhibiting the lowest values and the potato starch nanogels exhibiting the highest values.