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Research Advances in Natural Polymer-Based Hydrogels

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Biomaterials".

Deadline for manuscript submissions: closed (20 April 2022) | Viewed by 49634

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Special Issue Editor

Dr. Diana Elena Ciolacu

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Laboratory of Polymer Physical Chemistry, “Petru Poni” Institute of Macromolecular Chemistry, Iasi, Romania
Interests: cellulose; hydrogel; cross-linking; nanocellulose; lignin; polyssacharides; drug release
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Special Issue Information

Dear Colleagues,

Hydrogels have tremendous potential in various applications because of their high water content, softness, flexibility, tunable physical and mechanical properties, relatively low cytotoxicity, and increased biocompatibility. The current trend in designing natural-based hydrogels is focused on improving the manufacturing process by using non-toxic cross-linking agents or safe chemical processes, and by getting products that respond to the current environmental and health concerns. There is a visible tendency to use more environmentally friendly materials for the preparation of hydrogels, and natural polymers provide promising opportunities for both fundamental and applied research.

In this regard, it is our pleasure to invite you to contribute full papers, review articles, and short communications to the upcoming Special Issue of Materials, which focuses on the recent advances and developments related to the natural polymer-based hydrogels, with particular attention to engineering and biomedical applications.

We welcome any submissions related to the three-dimensional (3D) structure of hydrogels prepared using physical or chemical cross-linking reactions, from natural polymers (such as polysaccharides and polypeptides) or composite hydrogels in different forms (microgels, nanogels, films, membranes, beads, etc.).

Recent progress on the design and synthesis of hydrogels and their properties, revealed by different complementary techniques, which offer insight into the structure–property relationships, as well as the challenges that need to be overcome in order to achieve applications in pharmaceutical and medical fields are also welcome. The smart behavior of natural polymer-based hydrogels that is displayed in response to external stimuli, such as pH, temperature, ionic strength, and so on, can also be discussed.

All of the features associated with engineering aspects related to the manufacture of natural-polymer-based hydrogels, such as the drug delivery systems, wound dressing, tissue engineering scaffolds, self-healing materials, or biosensors, are of particular interest to this Special Issue.

Dr. Diana Ciolacu
Guest Editor

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Keywords

natural polymers
hydrogel
chemical cross-linking
composite hydrogel
stimuli-responsive
drug delivery
tissue engineering

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Published Papers (12 papers)

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Research

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15 pages, 5235 KiB

Open AccessArticle

Tunable Properties via Composition Modulations of Poly(vinyl alcohol)/Xanthan Gum/Oxalic Acid Hydrogels

by Alin Alexandru Enache, Diana Serbezeanu, Tăchiță Vlad-Bubulac, Alina-Mirela Ipate, Dana Mihaela Suflet, Mioara Drobotă, Mihaela Barbălată-Mândru, Radu Mihail Udrea and Cristina Mihaela Rîmbu

Materials 2022, 15(7), 2657; https://doi.org/10.3390/ma15072657 - 4 Apr 2022

Cited by 10 | Viewed by 2269

Abstract

The design of hydrogel networks with tuned properties is essential for new innovative biomedical materials. Herein, poly(vinyl alcohol) and xanthan gum were used to develop hydrogels by the freeze/thaw cycles method in the presence of oxalic acid as a crosslinker. The structure and morphology of the obtained hydrogels were investigated by means of scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and swelling behavior. The SEM analysis revealed that the surface morphology was mostly affected by the blending ratio between the two components, namely, poly(vinyl alcohol) and xanthan gum. From the swelling study, it was observed that the presence of oxalic acid influenced the hydrophilicity of blends. The hydrogels based on poly(vinyl alcohol) without xanthan gum led to structures with a smaller pore diameter, a lower swelling degree in pH 7.4 buffer solution, and a higher elastic modulus. The antimicrobial activity of the prepared hydrogels was tested and the results showed that the hydrogels conferred antibacterial activity against Gram positive bacteria (Staphylococcus aureus 25923 ATCC) and Gram negative bacteria (Escherichia coli 25922 ATCC). Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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21 pages, 5039 KiB

Open AccessArticle

New Composite Hydrogel Based on Whey and Gelatin Crosslinked with Copper Sulphate

by Pompilia Mioara Purcea Lopes, Dumitriţa Moldovan, Marioara Moldovan, Rahela Carpa, Codruţa Saroşi, Petru Păşcuţă, Amalia Mazilu Moldovan, Radu Fechete and Violeta Popescu

Materials 2022, 15(7), 2611; https://doi.org/10.3390/ma15072611 - 1 Apr 2022

Cited by 8 | Viewed by 3070

Abstract

By-products from the meat and dairy industries are important sources of high biological value proteins. This paper explores possibilities for improving the swelling and integrity of a cross-linked whey and gelatin hydrogel with different amounts of CuSO₄ × 5H₂O. Overall, swelling tests demonstrate that cross-linked samples show a better hydration capacity and stability in the hydration medium, but different copper concentrations lead to different swelling behavior. At concentrations smaller than 0.39%, the sample lasts for 75 h in a water environment before beginning to disintegrate. At a concentration of copper sulphate higher than 0.55%, the stability of the sample increased substantially. The swelling kinetics has been investigated. The diffusion constant values increased with the increase in copper concentration, but, at the highest concentration of copper (0.86%), its value has decreased. Spectroscopy analyses such as Fourier transform infrared (FT-IR), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-VIS), and nuclear magnetic resonance (NMR) relaxometry analyses revealed changes in the secondary and tertiary structure of proteins as a result of the interaction of Cu²⁺ ions with functional groups of protein chains. In addition to its cross-linking ability, CuSO₄ × 5H₂O has also shown excellent antibacterial properties over common bacterial strains responsible for food spoilage. The result of this research demonstrates the potential of this hydrogel system as a unique material for food packaging. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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25 pages, 5053 KiB

Open AccessArticle

Poloxamer 407-Based Thermosensitive Emulgel as a Novel Formulation Providing a Controlled Release of Oil-Soluble Pharmaceuticals—Ibuprofen Case Study

by Kamil P. Grela, Dominik M. Marciniak and Bożena Karolewicz

Materials 2021, 14(23), 7266; https://doi.org/10.3390/ma14237266 - 27 Nov 2021

Cited by 4 | Viewed by 2629

Abstract

This article covers the design and evaluation of a novel drug vehicle: a thermosensitive, injectable, high-oil-content (50% w/w) emulgel providing a controlled release of lipophilic pharmaceuticals. Different vegetable (castor, canola, olive, peanut, grapeseed, linseed), mineral (paraffin) and semisynthetic (isopropyl myristate, oleic acid) oils were screened for ibuprofen (IBU) solubility and for their capacity for high-shear emulsification in a 17% (w/w) aqueous solution of poloxamer 407. Chosen emulgels were subject to a rheological evaluation, a syringeability test (TA.XT texture analyser; 2 mL syringe; 18 G, 20 G and 22 G needles) and a drug release study (48 h; cellulose membrane; 0.05 mol/L phosphate buffer at pH 7.4). Castor oil turned out to be an optimal component for IBU incorporation. Blank and drug-loaded castor oil emulgels were susceptible to administration via a syringe and needle, with the absolute injection force not exceeding 3 kg (29.4 N). The drug release test revealed dose-dependent, quasi-linear kinetics, with up to 44 h of controlled, steady, linear release. The results indicate the significant potential of high-oil-content, oil-in-water thermosensitive emulgel formulations as vehicles for the controlled release of lipophilic APIs. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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15 pages, 2291 KiB

Open AccessArticle

The Influence of Enzymatic Hydrolysis of Whey Proteins on the Properties of Gelatin-Whey Composite Hydrogels

by Violeta Popescu, Andreia Molea, Marioara Moldovan, Pompilia Mioara Lopes, Amalia Mazilu Moldovan and George Liviu Popescu

Materials 2021, 14(13), 3507; https://doi.org/10.3390/ma14133507 - 23 Jun 2021

Cited by 16 | Viewed by 3004

Abstract

Amino-acids, peptides, and protein hydrolysates, together with their coordinating compounds, have various applications as fertilizers, nutritional supplements, additives, fillers, or active principles to produce hydrogels with therapeutic properties. Hydrogel-based patches can be adapted for drug, protein, or peptide delivery, and tissue healing and regeneration. These materials have the advantage of copying the contour of the wound surface, ensuring oxygenation, hydration, and at the same time protecting the surface from bacterial invasion. The aim of this paper is to describe the production of a new type of hydrogel based on whey protein isolates (WPI), whey protein hydrolysates (WPH), and gelatin. The hydrogels were obtained by utilizing a microwave-assisted method using gelatin, glycerol, WPI or WPH, copper sulfate, and water. WPH was obtained by enzymatic hydrolysis of whey protein isolates in the presence of bromelain. The hydrogel films obtained have been characterized by FT-IR and UV-VIS spectroscopy. The swelling degree and swelling kinetics have also been determined. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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17 pages, 2577 KiB

Open AccessCommunication

Functionalization of Cellulose-Based Hydrogels with Bi-Functional Fusion Proteins Containing Carbohydrate-Binding Modules

by Mariana Barbosa, Hélvio Simões and Duarte Miguel F. Prazeres

Materials 2021, 14(12), 3175; https://doi.org/10.3390/ma14123175 - 9 Jun 2021

Cited by 6 | Viewed by 2727

Abstract

Materials with novel and enhanced functionalities can be obtained by modifying cellulose with a range of biomolecules. This functionalization can deliver tailored cellulose-based materials with enhanced physical and chemical properties and control of biological interactions that match specific applications. One of the foundations for the success of such biomaterials is to efficiently control the capacity to combine relevant biomolecules into cellulose materials in such a way that the desired functionality is attained. In this context, our main goal was to develop bi-functional biomolecular constructs for the precise modification of cellulose hydrogels with bioactive molecules of interest. The main idea was to use biomolecular engineering techniques to generate and purify different recombinant fusions of carbohydrate binding modules (CBMs) with significant biological entities. Specifically, CBM-based fusions were designed to enable the bridging of proteins or oligonucleotides with cellulose hydrogels. The work focused on constructs that combine a family 3 CBM derived from the cellulosomal-scaffolding protein A from Clostridium thermocellum (CBM3) with the following: (i) an N-terminal green fluorescent protein (GFP) domain (GFP-CBM3); (ii) a double Z domain that recognizes IgG antibodies; and (iii) a C-terminal cysteine (CBM3C). The ability of the CBM fusions to bind and/or anchor their counterparts onto the surface of cellulose hydrogels was evaluated with pull-down assays. Capture of GFP-CBM3 by cellulose was first demonstrated qualitatively by fluorescence microscopy. The binding of the fusion proteins, the capture of antibodies (by ZZ-CBM3), and the grafting of an oligonucleotide (to CBM3C) were successfully demonstrated. The bioactive cellulose platform described here enables the precise anchoring of different biomolecules onto cellulose hydrogels and could contribute significatively to the development of advanced medical diagnostic sensors or specialized biomaterials, among others. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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10 pages, 2852 KiB

Open AccessArticle

Utilizing Edible Agar as a Carrier for Dual Functional Doxorubicin-Fe₃O₄ Nanotherapy Drugs

by Yu-Jyuan Wang, Pei-Ying Lin, Shu-Ling Hsieh, Rajendranath Kirankumar, Hsin-Yi Lin, Jia-Huei Li, Ya-Ting Chen, Hao-Ming Wu and Shuchen Hsieh

Materials 2021, 14(8), 1824; https://doi.org/10.3390/ma14081824 - 7 Apr 2021

Cited by 16 | Viewed by 2311

Abstract

The purpose of this study was to use agar as a multifunctional encapsulating material to allow drug and ferromagnetism to be jointly delivered in one nanoparticle. We successfully encapsulated both Fe₃O₄ and doxorubicin (DOX) with agar as the drug carrier to obtain DOX-Fe₃O₄@agar. The iron oxide nanoparticles encapsulated in the carrier maintained good saturation of magnetization (41.9 emu/g) and had superparamagnetism. The heating capacity test showed that the specific absorption rate (SAR) value was 18.9 ± 0.5 W/g, indicating that the ferromagnetic nanoparticles encapsulated in the gel still maintained good heating capacity. Moreover, the magnetocaloric temperature could reach 43 °C in a short period of five minutes. In addition, DOX-Fe₃O₄@agar reached a maximum release rate of 85% ± 3% in 56 min under a neutral pH 7.0 to simulate the intestinal environment. We found using fluorescent microscopy that DOX entered HT-29 human colon cancer cells and reduced cell viability by 66%. When hyperthermia was induced with an auxiliary external magnetic field, cancer cells could be further killed, with a viability of only 15.4%. These results show that agar is an efficient multiple-drug carrier, and allows controlled drug release. Thus, this synergic treatment has potential application value for biopharmaceutical carrier materials. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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10 pages, 2083 KiB

Open AccessArticle

High Mechanical Performance Based on Physically Linked Double Network (DN) Hydrogels

by Li Niu, Yutao Zhang, Liyu Shen, Qiuyue Sheng, Shuai Fu, Shiyan Chen, Yun Du, Ying Chen and Yupeng Liu

Materials 2019, 12(20), 3333; https://doi.org/10.3390/ma12203333 - 12 Oct 2019

Cited by 2 | Viewed by 3059

Abstract

A new design strategy was proposed to improve the mechanical performance of double network (DN) hydrogels by introducing polyhydroxy compounds into the DN structure and form a physically linked double network through the interaction of hydrogen bonding. Herein, agar/poly(acrylic acid)/hydroxyethyl cellulose composite hydrogels could be prepared by a simple one-pot method. The resulting hydrogels exhibit highly mechanical properties and excellent recoverability, which have potential applications in biomedical fields. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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11 pages, 1149 KiB

Open AccessArticle

Fabrication and Characterization of Low Methoxyl Pectin/Gelatin/Carboxymethyl Cellulose Absorbent Hydrogel Film for Wound Dressing Applications

by Pensak Jantrawut, Juthamart Bunrueangtha, Juthamart Suerthong and Nutthapong Kantrong

Materials 2019, 12(10), 1628; https://doi.org/10.3390/ma12101628 - 17 May 2019

Cited by 57 | Viewed by 5753

Abstract

In this study, hydrogel films composed of low methoxyl pectin (LMP), gelatin, and carboxymethyl cellulose (CMC) were fabricated. Glycerin was used as a plasticizer while glutaraldehyde (Glu) and calcium chloride (CaCl₂) were used as crosslinking agents in film preparation. Hydrogel films were morphologically characterized and evaluated for mechanical properties. In addition, the investigations for fluid uptake ability, water retention capacity, water vapor transmission rate, and integrity value of the invented films were performed. The results showed that F-Glu-Ca-G30 film demonstrated superior properties when compared to other prepared films. It demonstrated a high percentage of elongation at break (32.80%), fluid uptake ability (88.45% at 2 h), water retention capacity (81.70% at 2 h), water vapor transmission rate (1889 g/m²/day), and integrity value (86.42%). F-Glu-Ca-G30 film was subsequently selected for 10% w/w povidone iodine (PI) loading and tested for anti-Staphylococcus aureus activity using an agar diffusion assay. Notably, F-Glu-Ca-G30-PI film demonstrated a dramatic ability to inhibit microbial growth, when compared to both a blank film and iodine solution control. Our LMP/gelatin/CMC hydrogel film promises to be an effective dressing material with high fluid absorption capacity, fluid holding ability, and water vapor transmission rate. Incorporation of antibiotics such as povidone iodine into the films conferred its antimicrobial property thereby highlighting its potential dermatological use. However, further clinical studies of the application of this hydrogel film as wound dressing material is recommended. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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15 pages, 3326 KiB

Open AccessArticle

Physical Hydrogels of Oxidized Polysaccharides and Poly(Vinyl Alcohol) for Wound Dressing Applications

by Raluca Ioana Baron, Madalina Elena Culica, Gabriela Biliuta, Maria Bercea, Simona Gherman, Daniela Zavastin, Lacramioara Ochiuz, Mihaela Avadanei and Sergiu Coseri

Materials 2019, 12(9), 1569; https://doi.org/10.3390/ma12091569 - 13 May 2019

Cited by 48 | Viewed by 4731

Abstract

Two natural polymers, i.e., cellulose and water soluble pullulan, have been selectively oxidized employing the TEMPO-mediated protocol, to allow the introduction of C₆-OOH groups. Thereafter, the composite hydrogels of poly(vinyl alcohol) (PVA) and different content of the oxidized polysaccharides were prepared by the freezing/thawing method. The Fourier transform infrared spectroscopy (FTIR) has been used to discuss the degree of interaction between the hydrogels constituents into the physical network. The homogeneity of the prepared hydrogels as revealed by the SEM show an excellent distribution of the oxidized polysaccharides inside the PVA matrix. The samples exhibit self-healing features, since they quickly recover the initial structure after being subjected to a large deformation. The cell viability was performed for the selected hydrogels, all of them showing promising results. The samples are able to load L-arginine both by physical phenomena, such as diffusion, and also by chemical phenomena, when imine-type bonds are likely to be formed. The synergism between the two constituents, PVA and oxidized polysaccharides, into the physical network, propose these hydrogels for many other biomedical applications. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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20 pages, 5240 KiB

Open AccessArticle

Analysis of the Effect of Processing Conditions on Physical Properties of Thermally Set Cellulose Hydrogels

by Tim Huber, Sean Feast, Simone Dimartino, Wanwen Cen and Conan Fee

Materials 2019, 12(7), 1066; https://doi.org/10.3390/ma12071066 - 1 Apr 2019

Cited by 31 | Viewed by 6122

Abstract

Cellulose-based hydrogels were prepared by dissolving cellulose in aqueous sodium hydroxide (NaOH)/urea solutions and casting it into complex shapes by the use of sacrificial templates followed by thermal gelation of the solution. Both the gelling temperatures used (40–80 °C), as well as the method of heating by either induction in the form of a water bath and hot press or radiation by microwaves could be shown to have a significant effect on the compressive strength and modulus of the prepared hydrogels. Lower gelling temperatures and shorter heating times were found to result in stronger and stiffer gels. Both the effect of physical cross-linking via the introduction of additional non-dissolving cellulosic material, as well as chemical cross-linking by the introduction of epichlorohydrin (ECH), and a combination of both applied during the gelation process could be shown to affect both the mechanical properties and microstructure of the hydrogels. The added cellulose acts as a physical-cross-linking agent strengthening the hydrogen-bond network as well as a reinforcing phase improving the mechanical properties. However, chemical cross-linking of an unreinforced gel leads to unfavourable bonding and cellulose network formation, resulting in drastically increased pore sizes and reduced mechanical properties. In both cases, chemical cross-linking leads to larger internal pores. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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Review

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39 pages, 6692 KiB

Open AccessReview

Insight into the Latest Medical Applications of Nanocellulose

by Alina Ghilan, Raluca Nicu, Diana E. Ciolacu and Florin Ciolacu

Materials 2023, 16(12), 4447; https://doi.org/10.3390/ma16124447 - 17 Jun 2023

Cited by 15 | Viewed by 2947

Abstract

Nanocelluloses (NCs) are appealing nanomaterials that have experienced rapid development in recent years, with great potential in the biomedical field. This trend aligns with the increasing demand for sustainable materials, which will contribute both to an improvement in wellbeing and an extension of human life, and with the demand to keep up with advances in medical technology. In recent years, due to the diversity of their physical and biological properties and the possibility of tuning them according to the desired goal, these nanomaterials represent a point of maximum interest in the medical field. Applications such as tissue engineering, drug delivery, wound dressing, medical implants or those in cardiovascular health are some of the applications in which NCs have been successfully used. This review presents insight into the latest medical applications of NCs, in the forms of cellulose nanocrystals (CNCs), cellulose nanofibers (CNFs) and bacterial nanocellulose (BNC), with an emphasis on the domains that have recently experienced remarkable growth, namely wound dressing, tissue engineering and drug delivery. In order to highlight only the most recent achievements, the presented information is focused on studies from the last 3 years. Approaches to the preparation of NCs are discussed either by top-down (chemical or mechanical degradation) or by bottom-up (biosynthesis) techniques, along with their morphological characterization and unique properties, such as mechanical and biological properties. Finally, the main challenges, limitations and future research directions of NCs are identified in a sustained effort to identify their effective use in biomedical fields. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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35 pages, 5633 KiB

Open AccessReview

A Review on the Design and Hydration Properties of Natural Polymer-Based Hydrogels

by Abdalla H. Karoyo and Lee D. Wilson

Materials 2021, 14(5), 1095; https://doi.org/10.3390/ma14051095 - 26 Feb 2021

Cited by 140 | Viewed by 9003

Abstract

Hydrogels are hydrophilic 3D networks that are able to ingest large amounts of water or biological fluids, and are potential candidates for biosensors, drug delivery vectors, energy harvester devices, and carriers or matrices for cells in tissue engineering. Natural polymers, e.g., cellulose, chitosan and starch, have excellent properties that afford fabrication of advanced hydrogel materials for biomedical applications: biodegradability, biocompatibility, non-toxicity, hydrophilicity, thermal and chemical stability, and the high capacity for swelling induced by facile synthetic modification, among other physicochemical properties. Hydrogels require variable time to reach an equilibrium swelling due to the variable diffusion rates of water sorption, capillary action, and other modalities. In this study, the nature, transport kinetics, and the role of water in the formation and structural stability of various types of hydrogels comprised of natural polymers are reviewed. Since water is an integral part of hydrogels that constitute a substantive portion of its composition, there is a need to obtain an improved understanding of the role of hydration in the structure, degree of swelling and the mechanical stability of such biomaterial hydrogels. The capacity of the polymer chains to swell in an aqueous solvent can be expressed by the rubber elasticity theory and other thermodynamic contributions; whereas the rate of water diffusion can be driven either by concentration gradient or chemical potential. An overview of fabrication strategies for various types of hydrogels is presented as well as their responsiveness to external stimuli, along with their potential utility in diverse and novel applications. This review aims to shed light on the role of hydration to the structure and function of hydrogels. In turn, this review will further contribute to the development of advanced materials, such as “injectable hydrogels” and super-adsorbents for applications in the field of environmental science and biomedicine. Full article

(This article belongs to the Special Issue Research Advances in Natural Polymer-Based Hydrogels)

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