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Hydrogels: Preparation, Characterization, and Applications

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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 December 2024) | Viewed by 19138

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Prof. Dr. Li-Ming Zhang

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Guest Editor

Material Science and Engineering School, Sun Yat-sen (Zhongshan) University, Guangzhou 510275, China
Interests: hydrogels; preparation; characterization; applications
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Fei Song

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Guest Editor

College of Chemistry, Sichuan University, Chengdu 610064, China
Interests: hydrogels; preparation; characterization; applications

Special Issue Information

Dear Colleagues,

Hydrogels with three-dimensional (3D) network structures are commonly prepared through the physical, chemical, and enzymatic cross-linking of hydrophilic compounds. These hydrogels, which are swell in water while retaining a significant amount of it within their 3D structures, have widespread applications in the biomedical field, environmental protection, food engineering, wearable devices, etc. In recent years, substantial progress has been made in fabricating diverse functional hydrogel materials by designing functional monomers, dynamic cross-linking networks, and topological architectures. Consequently, in this Special Issue, we aim to invite original research and review articles on advanced functional hydrogels, addressing the latest advancements in the design, preparation, characterization, and application of hydrogels across various domains, including food, the environment, energy, medicine, biology, and smart wearable systems.

Prof. Dr. Li-Ming Zhang
Prof. Dr. Fei Song
Guest Editors

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Keywords

hydrogels
preparations
characterization
applications

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Published Papers (9 papers)

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Research

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31 pages, 4890 KiB

Open AccessArticle

Characteristics of Hydrogels as a Coating for Microneedle Transdermal Delivery Systems with Agomelatine

by Monika Wojtyłko, Ariadna B. Nowicka, Anna Froelich, Mirosław Szybowicz, Tobiasz Banaszek, Dorota Tomczak, Wiesław Kuczko, Radosław Wichniarek, Irena Budnik, Barbara Jadach, Oliwia Kordyl, Antoni Białek, Julia Krysztofiak, Tomasz Osmałek and Dimitrios A. Lamprou

Molecules 2025, 30(2), 322; https://doi.org/10.3390/molecules30020322 - 15 Jan 2025

Cited by 1 | Viewed by 1643

Abstract

Agomelatine (AGM) is an effective antidepressant with low oral bioavailability due to intensive hepatic metabolism. Transdermal administration of agomelatine may increase its bioavailability and reduce the doses necessary for therapeutic effects. However, transdermal delivery requires crossing the stratum corneum barrier. For this purpose, the use of microneedles may increase the efficiency of administration. The aim of this study was to prepare an agomelatine-loaded hydrogel suitable for coating microneedles for the transdermal drug delivery of AGM. The optimized formulations were subjected to spectroscopic and rheological characterization and mechanical tests, as well as tested for release through an artificial membrane and permeation through human skin ex vivo. Both hydrogels were found to have suitable parameters for coating microneedles using the dip-coating method, including the stability of the substance at the process temperature, shear-thinning behavior, and appropriate textural parameters such as adhesion or hardness. Additionally, two formulations were tested for potential application to the skin alone because the gels showed suitable mechanical properties for the skin application. In this case, the ethanol gel was characterized by higher skin permeability and better spreadability. The information obtained in this study will allow the preparation of coated microneedles for the transdermal administration of agomelatine. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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15 pages, 5902 KiB

Open AccessArticle

In Situ Crosslinked Biodegradable Hydrogels Based on Poly(Ethylene Glycol) and Poly(ε-Lysine) for Medical Application

by Xia Ding, Bing Yang and Zhaosheng Hou

Molecules 2024, 29(22), 5435; https://doi.org/10.3390/molecules29225435 - 18 Nov 2024

Cited by 1 | Viewed by 1158

Abstract

Hydrogels have emerged as promising biomaterials due to their excellent performance; however, their biocompatibility, biodegradability, and absorbability still require improvement to support a broader range of medical applications. This paper presents a new biofunctionalized hydrogel based on in situ crosslinking between maleimide-terminated four-arm-poly(ethylene glycol) (4–arm–PEG–Mal) and poly(ε-lysine) (ε–PL). The PEG/ε–PL hydrogels, named LG–n, were rapidly formed via amine/maleimide reaction by mixing 4–arm–PEG–Mal and ε–PL under physiological conditions. The corresponding dry gels (DLG–n) were obtained through a freeze-drying technique. ¹H NMR, FT–IR, and SEM were utilized to confirm the structures of 4–arm–PEG–Mal and LG–n (or DLG–n), and the effects of solid content on the physicochemical properties of the hydrogels were investigated. Although high solid content could increase the swelling ratio, all LG–n samples exhibited a low equilibrium swelling ratio of less than 30%. LG–7, which contained moderate solid content, exhibited optimal compression properties characterized by a compressive fracture strength of 45.2 kPa and a deformation of 69.5%. Compression cycle tests revealed that LG–n demonstrated good anti-fatigue performance. In vitro degradation studies confirmed the biodegradability of LG–n, with the degradation rate primarily governing the drug (ceftibuten) release efficiency, leading to a sustained release duration of four weeks. Cytotoxicity tests, cell survival morphology observation, live/dead assays, and hemolysis tests indicated that LG–n exhibited excellent cytocompatibility and low hemolysis rates (<5%). Furthermore, the broad-spectrum antibacterial activity of LG–n was verified by an inhibition zone method. In conclusion, the developed LG–n hydrogels hold promising applications in the medical field, particularly as drug sustained-release carriers and wound dressings. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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15 pages, 1890 KiB

Open AccessArticle

Studies of the Sorption-Desorption of Pesticides from Cellulose-Based Derivative Nanocomposite Hydrogels

by Fabrício C. Tanaka, Uilian G. Yonezawa, Marcia R. de Moura and Fauze A. Aouada

Molecules 2024, 29(20), 4932; https://doi.org/10.3390/molecules29204932 - 18 Oct 2024

Viewed by 856

Abstract

This study analyzed the effect of cellulose derivatives, namely methylcellulose (MC) and carboxymethylcellulose (CMC), on the stability of zeolite in a polymeric solution that would synthesize a three-dimensional network of poly(methacrylic acid)-co-polyacrylamide (PMAA-co-PAAm). Additionally, it investigated the effect of pH on the release of paraquat (PQ) and difenzoquat (DFZ) herbicides. Similar to previous studies with hydrogels containing CMC, the presence of bi and trivalent salts, such as Ca⁺² and Al⁺³, also drastically reduced their swelling degree from 6.7 g/g in NaCl (0.15 mol·L⁻¹) to 2.1 g/g in an AlCl₃ solution (0.15 mol·L⁻¹) for the MC nanocomposite. The viscosity results may suggest that the formation of a polysaccharide-zeolite complex contributed to the zeolite stabilization. As for the adsorption results, all samples adsorbed practically the entire concentration of both herbicides in an aqueous solution. Finally, it was also observed that the valence of the salts and molecular weight of the herbicide affect the release process, where DFZ was the herbicide with the highest concentration released. Both nanostructured hydrogels with CMC and MC exhibited lower release at pH = 7.0. These results demonstrated that a more in-depth evaluation of the phenomena involved in the application of these materials in controlled-release systems could help mitigate the impact caused by pesticides. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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11 pages, 2617 KiB

Open AccessArticle

Composite Hydrogels with Rapid Self-Healing, Stretchable, Moldable and Antibacterial Properties Based on PVA/ε-Poly-l-lysine/Hyaluronic Acid

by Na Sun, Xiangnan Liu, Wenqi Lv, Chunlin Xu, Ailing Zhang and Panpan Sun

Molecules 2024, 29(19), 4666; https://doi.org/10.3390/molecules29194666 - 30 Sep 2024

Viewed by 1616

Abstract

Self-healing, stretchable, and moldable hydrogels have a great potential application in tissue engineering and soft robotics. Despite great success in reported hydrogels, it is still a great challenge to construct the moldable hydrogels with an ultrafast self-healing performance. Herein, the composite hydrogels (PBLH) with ultrafast self-healing, stretchable, and moldable properties were successfully constructed by poly (vinyl alcohol) (PVA), borate (B), ε-poly-l-lysine (EPL), and hyaluronic acid (HA) based on an efficient one-pot method. Fourier transform infrared spectroscopy, X-ray diffraction, and rheological measurements confirmed the formation of a dynamic network among PVA, B, EPL, and HA through the cross-linking of dynamic borate bonds, electrostatic interaction, and hydrogen bonding. Having fabricated the dynamic network structure, the damage gap of the composite hydrogels can heal within 1 min, presenting an excellent self-healing ability. Simultaneously, the composite hydrogels can be molded into various shapes, and the length of the composite hydrogels can be stretched to 15 times their original length. In addition, the composite hydrogels exhibited an excellent antibacterial property against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Our results illustrated that the composite hydrogels not only retain the advantages of traditional hydrogels but also possess ultrafast self-healing, outstanding stretchable and antibacterial properties, presenting a prospective candidate for constructing biomedical materials. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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16 pages, 4083 KiB

Open AccessArticle

Multi-Sensitive Au NCs/5-FU@Carr-LA Composite Hydrogels for Targeted Multimodal Anti-Tumor Therapy

by Chunxia Qi, Ang Li, Baoming Wu and Peisan Wang

Molecules 2024, 29(17), 4051; https://doi.org/10.3390/molecules29174051 - 27 Aug 2024

Cited by 2 | Viewed by 1132

Abstract

Multifunctional targeted drug delivery systems have been explored as a novel cancer treatment strategy to overcome limitations of traditional chemotherapy. The combination of photodynamic therapy and chemotherapy has been shown to enhance efficacy, but the phototoxicity of traditional photosensitizers is a challenge. In this study, we prepared a multi-sensitive composite hydrogel containing gold nanoclusters (Au NCs) and the temperature-sensitive antitumor drug 5-fluorourac il (5-FU) using carboxymethyl cellulose (Carr) as a dual-functional template. Au NCs were synthesized using sodium borohydride as a reducing agent and potassium as a promoter. The resulting Au NCs were embedded in the Carr hydrogel, which was then conjugated with lactobionic acid (LA) as a targeting ligand. The resulting Au NCs/5-FU@Carr-LA composite hydrogel was used for synergistic photodynamic therapy (PDT), photothermal therapy (PTT), and chemotherapy. Au NCs/5-FU@Carr-LA releases the drug faster at pH 5.0 due to the acid sensitivity of the Carr polymer chain. In addition, at 50 °C, the release rate of Au NCs/5-FU@Carr-LA is 78.2%, indicating that the higher temperature generated by the photothermal effect is conducive to the degradation of Carr polymer chains. The Carr hydrogel stabilized the Au NCs and acted as a matrix for drug loading, and the LA ligand facilitated targeted delivery to tumor cells. The composite hydrogel exhibited excellent biocompatibility and synergistic antitumor efficacy, as demonstrated by in vitro and in vivo experiments. In addition, the hydrogel had thermal imaging capabilities, making it a promising multifunctional platform for targeted cancer therapy. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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18 pages, 7989 KiB

Open AccessArticle

Injectable Hydrogels Based on Hyaluronic Acid and Gelatin Combined with Salvianolic Acid B and Vascular Endothelial Growth Factor for Treatment of Traumatic Brain Injury in Mice

by Guoying Zhou, Yajie Cao, Yujia Yan, Haibo Xu, Xiao Zhang, Tingzi Yan and Haitong Wan

Molecules 2024, 29(8), 1705; https://doi.org/10.3390/molecules29081705 - 10 Apr 2024

Cited by 3 | Viewed by 2451

Abstract

Traumatic brain injury (TBI) leads to structural damage in the brain, and is one of the major causes of disability and death in the world. Herein, we developed a composite injectable hydrogel (HA/Gel) composed of hyaluronic acid (HA) and gelatin (Gel), loaded with vascular endothelial growth factor (VEGF) and salvianolic acid B (SAB) for treatment of TBI. The HA/Gel hydrogels were formed by the coupling of phenol-rich tyramine-modified HA (HA-TA) and tyramine-modified Gel (Gel-TA) catalyzed by horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H₂O₂). SEM results showed that HA/Gel hydrogel had a porous structure. Rheological test results showed that the hydrogel possessed appropriate rheological properties, and UV spectrophotometry results showed that the hydrogel exhibited excellent SAB release performance. The results of LIVE/DEAD staining, CCK-8 and Phalloidin/DAPI fluorescence staining showed that the HA/Gel hydrogel possessed good cell biocompatibility. Moreover, the hydrogels loaded with SAB and VEGF (HA/Gel/SAB/VEGF) could effectively promote the proliferation of bone marrow mesenchymal stem cells (BMSCs). In addition, the results of H&E staining, CD31 and α-SMA immunofluorescence staining showed that the HA/Gel/SAB/VEGF hydrogel possessed good in vivo biocompatibility and pro-angiogenic ability. Furthermore, immunohistochemical results showed that the injection of HA/Gel/SAB/VEGF hydrogel to the injury site could effectively reduce the volume of defective tissues in traumatic brain injured mice. Our results suggest that the injection of HA/Gel hydrogel loaded with SAB and VEGF might provide a new approach for therapeutic brain tissue repair after traumatic brain injury. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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Review

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40 pages, 5811 KiB

Open AccessReview

New Perspectives of Hydrogels in Chronic Wound Management

by Adina Alberts, Andreea Gabriela Bratu, Adelina-Gabriela Niculescu and Alexandru Mihai Grumezescu

Molecules 2025, 30(3), 686; https://doi.org/10.3390/molecules30030686 - 4 Feb 2025

Cited by 5 | Viewed by 1898

Abstract

Chronic wounds pose a substantial healthcare concern due to their prevalence and cost burden. This paper presents a detailed overview of chronic wounds and emphasizes the critical need for novel therapeutic solutions. The pathophysiology of wound healing is discussed, including the healing stages and the factors contributing to chronicity. The focus is on diverse types of chronic wounds, such as diabetic foot necrosis, pressure ulcers, and venous leg ulcers, highlighting their etiology, consequences, and the therapeutic issues they provide. Further, modern wound care solutions, particularly hydrogels, are highlighted for tackling the challenges of chronic wound management. Hydrogels are characterized as multipurpose materials that possess vital characteristics like the capacity to retain moisture, biocompatibility, and the incorporation of active drugs. Hydrogels’ effectiveness in therapeutic applications is demonstrated by how they support healing, including preserving ideal moisture levels, promoting cellular migration, and possessing antibacterial properties. Thus, this paper presents hydrogel technology’s latest developments, emphasizing drug-loaded and stimuli-responsive types and underscoring how these advanced formulations greatly improve therapy outcomes by enabling dynamic and focused reactions to the wound environment. Future directions for hydrogel research promote the development of customized hydrogel treatments and the incorporation of digital health tools to improve the treatment of chronic wounds. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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26 pages, 3891 KiB

Open AccessReview

Development of Slow-Release Fertilizers with Function of Water Retention Using Eco-Friendly Starch Hydrogels

by Yue Song, Litao Ma, Qingfei Duan, Huifang Xie, Xinyi Dong, Huaran Zhang and Long Yu

Molecules 2024, 29(20), 4835; https://doi.org/10.3390/molecules29204835 - 12 Oct 2024

Cited by 9 | Viewed by 4384

Abstract

Over the past two decades, the development and commercialization of slow-release fertilizers (SRFs) have significantly advanced, with the primary aim of mitigating environmental issues associated with excessive fertilizer use. A range of methodologies, including chemical and physical reactions, incorporation into carriers with porous and layered structures, and coating techniques, have been explored and refined. On the other hand, global challenges such as drought and desertification further underscore the need for SRFs that not only control nutrient release but also improve soil moisture retention. This paper reviews the development and application of eco-friendly starch hydrogels as fertilizer carriers and water retention for SRFs, particularly starch-based superabsorbent polymers (SAPs) produced through grafting copolymerization with acrylamide. This review explores both scientific issues, such as the microstructures and releasing mechanisms of SAPs, and technical development, involving copolymerization technologies, multi-initialization processes, methods of loading fertilizer into hydrogel, etc. Starch, as both a biodegradable and renewable carbohydrate polymer, offers distinct advantages due to its excellent chemical stability and high reactivity. The fabrication techniques of SAPs have been developed from traditional batch polymerization in aqueous solutions to more efficient, solvent-free reactive extrusion. The benefits of SRFs based on SAPs encompass enhanced soil aeration, the prevention of soil deterioration, the minimization of water evaporation, environmental pollution control, reduction in plant mortality, and prolonged nutrient retention within soil. In this review, we summarize the current progress, identify limitations in existing technologies, and propose future research directions to further enhance the performance of starch-based SRFs. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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37 pages, 13271 KiB

Open AccessReview

Laponite^®—From Dispersion to Gel—Structure, Properties, and Applications

by Cristina-Eliza Brunchi and Simona Morariu

Molecules 2024, 29(12), 2823; https://doi.org/10.3390/molecules29122823 - 13 Jun 2024

Cited by 6 | Viewed by 2789

Abstract

Laponite^® (LAP) is an intensively studied synthetic clay due to the versatility given by its layered structure, which makes it usable in various applications. This review describes the multifaceted properties and applications of LAP in aqueous dispersions and gel systems. The first sections of the review discuss the LAP structure and the interactions between clay discs in an aqueous medium under different conditions (such as ionic strength, pH, temperature, and the addition of polymers) in order to understand the function of clay in tailoring the properties of the designed material. Additionally, the review explores the aging phenomenon characteristic of LAP aqueous dispersions as well as the development of shake-gels by incorporating LAP. The second part shows the most recent studies on materials containing LAP with possible applicability in the drilling industry, cosmetics or care products industry, and biomedical fields. By elucidating the remarkable versatility and ease of integration of LAP into various matrices, this review underscores its significance as a key ingredient for the creation of next-generation materials with tailored functionalities. Full article

(This article belongs to the Special Issue Hydrogels: Preparation, Characterization, and Applications)

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