The past, present and future of hydrogels

doi:10.1016/j.eurpolymj.2015.08.032

European Polymer Journal

Volume 72, November 2015, Pages 341-343

https://doi.org/10.1016/j.eurpolymj.2015.08.032 Get rights and content

Abstract

An overview of developments in the field of hydrogels is provided. The gradual increase in functionality and in complexity of hydrogels is highlighted in the light of the Special Issue on hydrogels. This contribution provides a concise overview of the majority of contributions to this Special Issue and aims to link it to historical developments in the field.

Graphical abstract

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Direct ink writing of biocompatible chitosan/non-isocyanate polyurethane/cellulose nanofiber hydrogels for wound-healing applications
2024, International Journal of Biological Macromolecules
The demand for new biocompatible and 3D printable materials for biomedical applications is on the rise. Ideally, such materials should exhibit either biodegradability or recyclability, possess antibacterial properties, and demonstrate remarkable biocompatibility with no cytotoxic effects. In this research, we synthesized biocompatible and 3D printable hydrogels tailored for biomedical applications, such as wound healing films, by combining antibacterial double-quaternized chitosan (DQC) with cystamine-based non-isocyanate polyurethane (NIPU-Cys) - a material renowned for enhancing both the flexibility and mechanical properties of the hydrogels. To improve the rheological behavior, swelling attributes, and printability, cellulose nanofibrils were introduced into the matrix. We investigated the impact of DQC on degradability, swelling capacity, rheological behavior, printability, and cell biocompatibility. The slightly cytotoxic nature associated with quaternary chitosan was evaluated, and the optimal concentration of DQC in the hydrogel was determined to ensure biocompatibility. The resulting hydrogels were found to be suitable materials for 3D printing via a direct ink writing technique (DIW), producing porous, biocompatible hydrogels endowed with valuable attributes suitable for various wound-healing applications.
Fabrication and characterization of wheat gliadin hydrogels with high strength and toughness
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Citation Excerpt :
Hydrogels are composed of a three-dimensional hydrophilic network and a large amount of water entrapped inside, both of which maintain the network structure integrity and therefore the gel property (Nnyigide et al., 2017; Zhang et al., 2015; Costa and Mano, 2015). However, traditionally prepared hydrogels commonly display poor mechanical properties due to their high-water content (Vermonden and Klumperman, 2015). Therefore, it has been increasing interest of how to enhance the mechanical strength of hydrogels in the material field (Costa and Mano, 2015; Vermonden and Klumperman, 2015).
Fabricating a hydrogel with high strength and toughness is still a challenge in many fields. Here, we prepared gliadin-based hydrogels by chemical cross-linking gliadin in acetic acid solution (GS) with glutaraldehyde (GA). Subsequently, the overall properties of the fabricated hydrogels were systematically investigated in terms of their mechanical properties, swelling ratio, weight loss, thermal stability, and the chemical/physical interactions in hydrogels. Results showed that the gliadin-based chemically cross-linked hydrogels exhibited excellent mechanical properties. The optimized hydrogel exhibited the compressive stress of 1.8 MPa at a strain of 70%, and an excellent self-recovery property after 30 cycles of loading-unloading treatments. The strength and toughness of the hydrogels could be tailored by adjusting the ratio of GS/GA. The chemical cross-linking (aldehyde-ammonia reaction) was the main molecular interaction in the hydrogels, including single-/multi-site crosslinking, and the hydrogen bond was the only physical cross-linking in the hydrogels. Moreover, the swelling ratio of the fabricated hydrogels performed a concentration negative-dependency in GA or GS concentration. And a higher GS concentration (40%) with an appropriate GA content (3.0%) could resist the degradation of hydrogels. In addition, the thermodynamic properties of hydrogels also improved by the GA addition. Overall, these findings suggested that gliadin can be applied for fabricating hydrogels with tunable mechanical properties, which will unlock the high-utilization of gliadin as biopolymer and biocompatible materials.
Antibacterial polypeptide/heparin composite hydrogels carrying growth factor for wound healing
2020, Materials Science and Engineering C
Citation Excerpt :
It is thus reasonable to incorporate growth factors to a structurally supporting biomaterial that mimics the ECM when developing a growth factor delivery platform. Hydrogels, which regarded as ECM mimics, absorb and retain large amounts of water in three-dimensional polymeric networks [4–7]. They have been extensively used in various biomedical applications including drug/protein delivery, wound dressing and tissue engineering [8–15].
We report an efficient growth factor delivering system based on polypeptide/heparin composite hydrogels for wound healing application. Linear and star-shaped poly(l-lysine) (l-PLL and s-PLL) were chosen due to not only their cationic characteristics, facilitating the efficient complexation of negatively charged heparin, but also the ease to tune the physical and mechanical properties of as-prepared hydrogels simply by varying polypeptide topology and chain length. The results showed that polymer topology can be an additional parameter to tune hydrogel properties. Our experimental data showed that these composite hydrogels exhibited low hemolytic activity and good cell compatibility as well as excellent antibacterial activity, making them ideal as wound dressing materials. Unlike other heparin-based hydrogels, these composite hydrogels with heparin densely deposited on the surface can increase the stabilization and concentration of growth factor, which can facilitate the healing process as confirmed by our in vivo animal model. We believe that these PLL/heparin composite hydrogels are promising wound dressing materials and may have potential applications in other biomedical fields.
A review on latest innovations in natural gums based hydrogels: Preparations & applications
2019, International Journal of Biological Macromolecules
Citation Excerpt :
These hydrated polymeric networks that display higher strength and elasticity [8,9] are insoluble in water [10]. These polymeric hydrogels are highly responsive when their surroundings such as electric field pH, pressure, solvent composition and temperature are altered [11–14]. They are of interest as biomimetic/intelligent/smart materials which have applications in sensor and/or actuators and more often they are being designed as self-oscillating gels, moreover their practical importance is tremendously increasing day by day [15].
The prospective uses of natural gum polysaccharides in various aspects of food, water, energy, biotechnology, environment and medicine industries, have garnered a great deal of attention recently. Natural gums have gained widespread attention due to their availability, low cost, structural diversity and remarkable properties as ‘green’ bio-based renewable materials. Natural gums are obtainable as natural polysaccharides from various tree genera possessing exceptional properties, including their renewable, biocompatible, biodegradable, and non-toxic nature and their ability to undergo easy chemical modifications. Hydrogels based on natural gums offer several valuable properties when equated to synthetic origin. The fundamental objective of this review is to compile different strategies for the preparation of hydrogels based on several important commercially available gums (arabic, guar, gellan, ghatti, karaya, kondagogu, konjac, locust bean tamarind, tragacanth, tara and xanthan) for the greener synthesis and stabilization of metal/metal oxide NPs, production of electrospun fibers, water purification, drug delivery, tissue engineering, agriculture and for antimicrobial and biomedical applications.
Ultrafast in situ forming poly(ethylene glycol)-poly(amido amine) hydrogels with tunable drug release properties via controllable degradation rates
2019, European Journal of Pharmaceutics and Biopharmaceutics
Citation Excerpt :
Hydrogels are three-dimensional polymer networks whose properties resemble those of natural soft tissues due to their high water content [1–3].
Fast in situ forming, chemically crosslinked hydrogels were prepared by the amidation reaction between N-succinimidyl ester end groups of multi-armed poly(ethylene glycol) (PEG) and amino surface groups of poly(amido amine) (PAMAM) dendrimer generation 2.0. To control the properties of the PEG/PAMAM hydrogels, PEGs were used with different arm numbers (4 or 8) as well as different linkers (amide or ester) between the PEG arms and their terminal N-succinimidyl ester groups. Oscillatory rheology measurements showed that the hydrogels form within seconds after mixing the PEG and PAMAM precursor solutions. The storage moduli increased with crosslink density and reached values up to 2.3 kPa for hydrogels based on 4-armed PEG. Gravimetrical degradation experiments demonstrated that hydrogels with ester linkages between PEG and PAMAM degrade within 2 days, whereas amide-linked hydrogels were stable for several months. The release of two different model drugs (fluorescein isothiocyanate-dextran with molecular weights of 4·10³ and 2·10⁶ g/mol, FITC-DEX4K and FITC-DEX2000K, respectively) from amide-linked hydrogels was characterized by an initial burst followed by diffusion-controlled release, of which the rate depended on the size of the drug. In contrast, the release of FITC-DEX2000K from ester-containing hydrogels was governed mainly by degradation of the hydrogels and could be modulated via the ratio between ester and amide linkages. In vitro cytotoxicity experiments indicated that the PEG/PAMAM hydrogels are non-toxic to mouse fibroblasts. These in situ forming PEG/PAMAM hydrogels can be tuned with a broad range of mechanical, degradation and release properties and therefore hold promise as a platform for the delivery of therapeutic agents.
Novel synergistic transparent k-Carrageenan/Xanthan gum/Gellan gum hydrogel film: Mechanical, thermal and water barrier properties
2018, International Journal of Biological Macromolecules
The aim is to develop novel synergistic transparent k-Carrageenan/Xanthan gum/Gellan gum (k-C/X/G) hydrogel films with different weight ratio composition and to study the effect of these compositions on the physical properties of the films. The structure and morphological properties of the films were investigated by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimeter (DSC). Results for FT-IR, DSC and SEM analysis showed a clear interaction between k-C, X, and G to form a new material. The mechanical, thermal and water barrier properties such as water vapor permeability (WVP), water contact angle (WCA) and moisture content were determined. The temperature at 5% weight loss (T_5%) are in the range of 64.2–121.9 °C. The WVP exhibits are in the range of 1.8–2.4, contact angle are in the range of 32–65.8° and moisture content 16.5–21.51. The hydrogel film had good tensile strength of 19.1–31.0 MPa and elongation at break of 13–19% and tensile modulus of 1.6–2.4 GPa. The UV results indicate that the films were very transparent. The range of properties of the ternary k-C/X/G hydrogel films suggest that the presence molecular interaction and cross linking within the blends.

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Editorial itemsThe past, present and future of hydrogels

Abstract

Graphical abstract

J. Controll. Release

Adv. Drug Deliv. Rev.

Adv. Mater.

Adv. Mater.

Adv. Mater.

Materials

Adv. Mater.

Adv. Mater.

Macromolecules

Polym. Chem.

Adv. Funct. Mater.

Eur. Polym. J.

Hydrogels in biomedical applications

Br. Polym. J.

Design and processing of nanogels as delivery systems for peptides and proteins

Ther. Deliv.

Click hydrogels, microgels and nanogels: emerging platforms for drug delivery and tissue engineering

Biomaterials

Editorial items
The past, present and future of hydrogels