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Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (2nd Edition)
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Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (2nd Edition)

A special issue of Gels (ISSN 2310-2861). This special issue belongs to the section "Gel Analysis and Characterization".

Deadline for manuscript submissions: closed (20 February 2025) | Viewed by 8278

Special Issue Editors

Dr. Valentina Nigro

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Guest Editor
Fusion and Technologies for Nuclear Safety and Security Department, ENEA Frascati Research Centre, 00044 Rome, Italy
Interests: materials science; soft matter; gels; scattering techniques; spectroscopy
Special Issues, Collections and Topics in MDPI journals
Dr. Francesca Limosani

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Guest Editor
Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via Della Ricerca Scientifica, 00133 Rome, Italy
Interests: chemical synthesis; electron transfer processes; hybrid materials for solar energy; electrochemical and biomedical applications; thin films; optical techniques
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We are grateful to all authors, reviewers, and readers for their responses to the first edition of our Special Issue entitled “Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications”. You can access these articles for free via the following link: https://www.mdpi.com/journal/gels/special_issues/L3O48JY2AD.

In recent years, hydrogels have attracted significant interest owing to their fascinating properties, attributes that have revealed an array of application-related opportunities in various fields.

Hydrogels are a highly versatile class of biomaterials, consisting of hydrophilic polymer networks that can be processed into bulk materials, as well as micro- or nanoparticles of both natural and synthetic origin.

Hydrogels are characterized by many fascinating properties, such as swelling, softness and sensitivity to external stimuli. Indeed, cross-linked hydrogel particles with a size ranging from the nanometric to the micrometric, which are known as microgels, can be tailored to achieve the desired degree of multi-functionality.

Their unique character is a result of their hybrid nature between polymers and colloids, leading to a rich phase behavior that can be tuned through easily accessible control parameters. These features make microgels intriguing model colloids for the exploration of phase transitions in complex systems, and highly attractive materials for several technological applications.

Owing to this wide variety of interesting properties, smart hydrogel-based materials have found application as innovative solutions in various fields, such as drug delivery, tissue engineering, agriculture, cultural heritage, sensing and biosensing.

This Special Issue focuses on experiments, simulation, synthesis methods and the application of smart hydrogels, microgels and nanogels. Manuscripts may address synthesis methods, dynamics and structure, phase diagrams and interparticle interactions, and their manifold applications in different fields.

Both original contributions and reviews are welcome.

Dr. Valentina Nigro
Dr. Francesca Limosani
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • hydrogels
  • microgels
  • polymers
  • colloids
  • synthesis
  • characterization
  • applications
  • swelling
  • phase behavior
  • stimuli responsive

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Related Special Issues

Published Papers (6 papers)

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Research

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14 pages, 3801 KiB  
Article
Investigation of PVA Matrix Hydrogel Loaded with Centaurea cyanus Extract for Wound Dressing Applications: Morphology, Drug Release, Antibacterial Efficiency, and In Vitro Evaluation
by Melis Abahuni Ucar, Enis Muhammet Gul, Deniz Uygunoz, Emek Moroydor Derun and Mehmet Burcin Piskin
Gels 2025, 11(4), 264; https://doi.org/10.3390/gels11040264 - 2 Apr 2025
Viewed by 365
Abstract
A polyvinyl alcohol (PVA) matrix hydrogel loaded with Centaurea cyanus extract was created for transdermal wound healing. Secondary metabolites, antibacterial properties, and the cytotoxicity of C. cyanus extract were investigated. The secondary metabolite profiles of the extract were determined by liquid chromatography–mass spectrometry [...] Read more.
A polyvinyl alcohol (PVA) matrix hydrogel loaded with Centaurea cyanus extract was created for transdermal wound healing. Secondary metabolites, antibacterial properties, and the cytotoxicity of C. cyanus extract were investigated. The secondary metabolite profiles of the extract were determined by liquid chromatography–mass spectrometry (LC-MS) technique. It was determined that the extract has metabolites such as quinic acid, caffeoylquinic acid, kaempferol, etc., which contribute to the steps of wound healing. The extract had significant activity against Staphylococcus aureus when compared with ampicillin antibiotic and showed an inhibition zone of 16.9 mm ± 0.8, whereas ampicillin’s inhibition zone was 15.8 mm ± 0.8. The extract did not exhibit cytotoxic effects on 3T3-L1 (CL173) healthy skin fibroblasts, maintained cell viability for 72 h, and exhibited a 19% proliferative effect. Fourier-transform infrared spectroscopy, scanning electron microscopy, ultraviolet visible spectrophotometer, tensile strength analyses, in vitro release, and physicochemical tests were conducted. It was seen that the surfaces of the samples are smooth and homogeneous, patches had a significant amount of water absorption capacity, and 79% of the extract was released within the first 24 h of application; consequently, these results indicate that C. cyanus might be used in wound healing with its antibacterial, growth-promoting properties. Full article
(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (2nd Edition))
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17 pages, 3765 KiB  
Article
A Multifunctional γ-Polyglutamic Acid Hydrogel for Combined Tumor Photothermal and Chemotherapy
by Xiaoqing Jia and Shige Wang
Gels 2025, 11(3), 217; https://doi.org/10.3390/gels11030217 - 20 Mar 2025
Cited by 9 | Viewed by 622
Abstract
Efficient and precise cancer therapy remains a challenge due to limitations in current treatment modalities. In this study, we developed a multifunctional hydrogel system that integrates photothermal therapy (PTT) and chemotherapy to achieve combined tumor treatment. The hydrogel, composed of γ-polyglutamic acid (γ-PGA), [...] Read more.
Efficient and precise cancer therapy remains a challenge due to limitations in current treatment modalities. In this study, we developed a multifunctional hydrogel system that integrates photothermal therapy (PTT) and chemotherapy to achieve combined tumor treatment. The hydrogel, composed of γ-polyglutamic acid (γ-PGA), fifth-generation polyamide-amine dendrimers (G5), and polydopamine (PDA) nanoparticles, exhibits high photothermal conversion efficiency and temperature-responsive drug release properties. The hydrogel exhibited a high photothermal conversion efficiency of 45.6% under 808 nm near-infrared (NIR) irradiation. Drug release studies demonstrated a cumulative hydrophilic anticancer drug doxorubicin DOX release of 79.27% within 72 h under mild hyperthermia conditions (50 °C). In vivo experiments revealed a significant tumor inhibition rate of 82.3% with minimal systemic toxicity. Comprehensive in vitro and in vivo evaluations reveal that the hydrogel demonstrates excellent biocompatibility, photothermal stability, and biodegradability. Unlike conventional hydrogel systems, our γ-PGA-based hydrogel uniquely integrates a biocompatible and biodegradable polymer with polydopamine (PDA) nanoparticles, providing a smart and responsive platform for precise cancer therapy. This multifunctional hydrogel system represents a promising platform that combines PTT precision and chemotherapy efficacy, providing a robust strategy for advanced and safer cancer treatment. Full article
(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (2nd Edition))
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20 pages, 65629 KiB  
Article
Poly(acrylic acid)-Sodium Alginate Superabsorbent Hydrogels Synthesized by Electron-Beam Irradiation—Part II: Swelling Kinetics and Absorption Behavior in Various Swelling Media
by Elena Manaila and Gabriela Craciun
Gels 2024, 10(9), 609; https://doi.org/10.3390/gels10090609 - 23 Sep 2024
Cited by 4 | Viewed by 1614
Abstract
Hybrid hydrogels with superabsorbent properties based on acrylic acid (20%), sodium alginate (0.5%) and poly(ethylene oxide) (0.1%) were obtained by electron-beam irradiation between 5 and 20 kGy, and are characterized by different physical and chemical methods; the first results reported showed gel fractions [...] Read more.
Hybrid hydrogels with superabsorbent properties based on acrylic acid (20%), sodium alginate (0.5%) and poly(ethylene oxide) (0.1%) were obtained by electron-beam irradiation between 5 and 20 kGy, and are characterized by different physical and chemical methods; the first results reported showed gel fractions over 87%, cross-link densities under 9.9 × 103 mol/cm3 and swelling degrees of 400 g/g. Two types of hydrogels (without and with 0.1% initiator potassium persulfate) have been subjected to swelling and deswelling experiments in different swelling media with different pHs, chosen in accordance with the purpose for which these superabsorbent materials were obtained, i.e., water and nutrients carriers for agricultural purposes: 6.05 (distilled water), 7.66 (tap water), 5.40 (synthetic nutrient solution) and 7.45 (organic nutrient solution). Swelling kinetics and swelling dynamics have been also studied in order to investigate the influence of swelling media type and pH on the absorption phenomenon. The swelling and deswelling behaviors were influenced by the hydrogel characteristics and pH of the swelling media. Both the polymeric chain relaxation (non-Fickian diffusion) and macromolecular relaxation (super case II) phenomenon were highlighted as a function of swelling media type. Full article
(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (2nd Edition))
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11 pages, 2656 KiB  
Article
Influence of a Solid Surface on PNIPAM Microgel Films
by Valentina Nigro, Roberta Angelini, Elena Buratti, Claudia Colantonio, Rosaria D’Amato, Franco Dinelli, Silvia Franco, Francesca Limosani, Rosa Maria Montereali, Enrico Nichelatti, Massimo Piccinini, Maria Aurora Vincenti and Barbara Ruzicka
Gels 2024, 10(7), 473; https://doi.org/10.3390/gels10070473 - 18 Jul 2024
Cited by 4 | Viewed by 1536
Abstract
Stimuli-responsive microgels have attracted great interest in recent years as building blocks for fabricating smart surfaces with many technological applications. In particular, PNIPAM microgels are promising candidates for creating thermo-responsive scaffolds to control cell growth and detachment via temperature stimuli. In this framework, [...] Read more.
Stimuli-responsive microgels have attracted great interest in recent years as building blocks for fabricating smart surfaces with many technological applications. In particular, PNIPAM microgels are promising candidates for creating thermo-responsive scaffolds to control cell growth and detachment via temperature stimuli. In this framework, understanding the influence of the solid substrate is critical for tailoring microgel coatings to specific applications. The surface modification of the substrate is a winning strategy used to manage microgel–substrate interactions. To control the spreading of microgel particles on a solid surface, glass substrates are coated with a PEI or an APTES layer to improve surface hydrophobicity and add positive charges on the interface. A systematic investigation of PNIPAM microgels spin-coated through a double-step deposition protocol on pristine glass and on functionalised glasses was performed by combining wettability measurements and Atomic Force Microscopy. The greater flattening of microgel particles on less hydrophilic substrates can be explained as a consequence of the reduced shielding of the water–substrate interactions that favors electrostatic interactions between microgels and the substrate. This approach allows the yielding of effective control on microgel coatings that will help to unlock new possibilities for their application in biomedical devices, sensors, or responsive surfaces. Full article
(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (2nd Edition))
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16 pages, 8434 KiB  
Article
Keratin–PNIPAM Hybrid Microgels: Preparation, Morphology and Swelling Properties
by Elena Buratti, Maddalena Sguizzato, Giovanna Sotgiu, Roberto Zamboni and Monica Bertoldo
Gels 2024, 10(6), 411; https://doi.org/10.3390/gels10060411 - 20 Jun 2024
Cited by 1 | Viewed by 1827
Abstract
Combinations of synthetic polymers, such as poly(N-isopropylacrylamide) (PNIPAM), with natural biomolecules, such as keratin, show potential in the field of biomedicine, since these hybrids merge the thermoresponsive properties of PNIPAM with the bioactive characteristics of keratin. This synergy aims to produce hybrids that [...] Read more.
Combinations of synthetic polymers, such as poly(N-isopropylacrylamide) (PNIPAM), with natural biomolecules, such as keratin, show potential in the field of biomedicine, since these hybrids merge the thermoresponsive properties of PNIPAM with the bioactive characteristics of keratin. This synergy aims to produce hybrids that can respond to environmental stimuli while maintaining biocompatibility and functionality, making them suitable for various medical and biotechnological uses. In this study, we exploit keratin derived from wool waste in the textile industry, extracted via sulfitolysis, to synthesize hybrids with PNIPAM microgel. Utilizing two distinct methods—polymerization of NIPAM with keratin (HYB-P) and mixing preformed PNIPAM microgels with keratin (HYB-M)—resulted in hybrids with 20% and 25% keratin content, respectively. Dynamic light scattering (DLS) and transmission electron microscopic (TEM) analyses indicated the formation of colloidal systems with particle sizes of around 110 nm for HYB-P and 518 nm for HYB-M. The presence of keratin in both systems, 20% and 25%, respectively, was confirmed by spectroscopic (FTIR and NMR) and elemental analyses. Distinct structural differences were observed between HYB-P and HYB-M, suggesting a graft copolymer configuration for the former hybrid and a complexation for the latter one. Furthermore, these hybrids demonstrated temperature responsiveness akin to PNIPAM microgels and pH responsiveness, underscoring their potential for diverse biomedical applications. Full article
(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (2nd Edition))
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Review

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37 pages, 1214 KiB  
Review
Cyclodextrin–Hydrogel Hybrids in Advanced Drug Delivery
by Hossein Omidian, Arnavaz Akhzarmehr and Erma J. Gill
Gels 2025, 11(3), 177; https://doi.org/10.3390/gels11030177 - 28 Feb 2025
Cited by 2 | Viewed by 1683
Abstract
Cyclodextrin (CD)–hydrogel hybrids have emerged as versatile and multifunctional drug delivery systems, offering enhanced solubility, controlled drug release, and improved bioavailability. By combining the inclusion complexation properties of CDs with the swelling and retention capabilities of hydrogels, these hybrid systems overcome key challenges [...] Read more.
Cyclodextrin (CD)–hydrogel hybrids have emerged as versatile and multifunctional drug delivery systems, offering enhanced solubility, controlled drug release, and improved bioavailability. By combining the inclusion complexation properties of CDs with the swelling and retention capabilities of hydrogels, these hybrid systems overcome key challenges in conventional drug formulations. This review explores CD composition, hydrogel polymer selection, fabrication techniques, key drug release factors, and real-world therapeutic applications. Additionally, the latest advancements in stimuli-responsive hydrogels, nanogels, and microneedle-based drug delivery are discussed. While CD–hydrogel systems demonstrate significant potential, scalability, regulatory hurdles, and clinical translation remain key challenges. Future research should focus on smart hydrogels, improved drug loading strategies, and enhanced clinical validation to bridge the gap between laboratory innovations and commercial applications. Full article
(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications (2nd Edition))
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