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Properties of Hydrogels, Aerogels, and Cryogels Composites

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

Deadline for manuscript submissions: closed (10 October 2023) | Viewed by 19073

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Dr. Irina Elena Raschip

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Petru Poni Institute of Macromolecular Chemistry, Grigore Ghica Voda Alley 41A, 700487 Iasi, Romania
Interests: biomaterials; porous gels; cryogel; functional materials
Special Issues, Collections and Topics in MDPI journals

Dr. Raluca Nicoleta Darie-Nita

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Petru Poni Institute of Macromolecular Chemistry, Grigore Ghica Voda Alley 41A, 700487 Iasi, Romania
Interests: reactive processing (natural and synthetic polymers); physico-chemical characterization of polymers and composites (rheological, mechanical, thermal, and surface properties); biodegradable polymers; applications of bio-based materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue on “Properties of Hydrogels, Aerogels, and Cryogels Composites” is dedicated to the latest advances in the preparation, properties, and applications of gel-type materials, highlighting key concepts relevant to the unique properties of hydrogels, aerogels, and cryogels.

Hydrogels have the ability to absorb impressive amounts of water or biological fluids within their peculiar structure of physically or chemically cross-linked 3D polymer networks. Hydrogels can be converted to aerogels following water removal via different approaches. Their distinctive features, such as super-absorbency, fluffiness, biocompatibility, viscoelasticity, and softness, underpin various applications, especially in the biomedical field.

Lately, porous gel materials have been found to offer more benefits than conventional hydrogels when applied as scaffolds for tissue engineering and regenerative medicine, substrates for cell culture, chromatographic materials, and carriers for controlled delivery of drugs or proteins. In this regard, cryogels have revolutionized the field of biomedical research with their super-elasticity and highly interconnected and open macroporous structure obtained by conducting polymerization/cross-linking at subzero temperatures. Furthermore, the development of sustainable composites has been a priority for polymer engineering research over the past two decades. Composite materials have been designed by blending two or more polymers or by entrapping inorganic or natural fillers of nano- or micro-sizes within a polymer matrix in order to tune the physical, chemical, and biological properties of hydrogels, aerogels and cryogels.

This Special Issue will cover new discoveries in the production of hydrogels, aerogels, and cryogels with a broad variety of morphologies and properties, which can be tailored for a particular application.

Dr. Irina Elena Raschip
Dr. Raluca Nicoleta Darie-Nita
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 2600 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

biomaterials
porous gels
functional materials
viscoelasticity
interconnectivity
swelling
biomedical and environmental applications

Published Papers (10 papers)

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Research

18 pages, 3239 KiB

Open AccessArticle

Encapsulation of Concentrated Solution Obtained by Block Freeze Concentration in Calcium Alginate and Corn Starch Calcium Alginate Hydrogel Beads

by Patricio Orellana-Palma, Loren Macias-Bu, Nailín Carvajal-Mena, Guillermo Petzold and Maria Guerra-Valle

Gels 2023, 9(5), 374; https://doi.org/10.3390/gels9050374 - 01 May 2023

Viewed by 1592

Abstract

A model (sucrose and gallic acid) solution was concentrated by block freeze concentration (BFC) at three centrifugation cycles, and the solutions were encapsulated in calcium alginate and corn starch calcium alginate hydrogel beads. Static and dynamic tests determined the rheological behavior, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) established thermal and structural properties, and the release kinetics was evaluated under in vitro simulated digestion experiment. The highest efficiency encapsulation value was close to 96%. As the concentrated solution increased in terms of solutes and gallic acid, the solutions were fitted to the Herschel–Bulkley model. Moreover, from the second cycle, the solutions exhibited the highest values of storage modulus (G′) and loss modulus (G″), contributing to form a more stable encapsulation. The FTIR and DSC results demonstrated strong interactions between corn starch and alginate, establishing a good compatibility and stability in the bead formation. The kinetic release model under in vitro conditions was fitted to the Korsmeyer–Peppas model, demonstrating the significant stability of the model solutions inside the beads. Therefore, the present study proposes a clear and precise definition for the elaboration of liquid foods obtained by BFC and its incorporation inside an edible material that facilitates the controlled release in specific sites. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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21 pages, 4980 KiB

Open AccessArticle

Correlation between Mechanical and Morphological Properties of Polyphenol-Laden Xanthan Gum/Poly(vinyl alcohol) Composite Cryogels

by Irina Elena Raschip, Raluca Nicoleta Darie-Nita, Nicusor Fifere, Gabriela-Elena Hitruc and Maria Valentina Dinu

Gels 2023, 9(4), 281; https://doi.org/10.3390/gels9040281 - 29 Mar 2023

Cited by 8 | Viewed by 1202

Abstract

This study aimed to evaluate the effect of the synthesis parameters and the incorporation of natural polyphenolic extract within hydrogel networks on the mechanical and morphological properties of physically cross-linked xanthan gum/poly(vinyl alcohol) (XG/PVA) composite hydrogels prepared by multiple cryo-structuration steps. In this context, the toughness, compressive strength, and viscoelasticity of polyphenol-loaded XG/PVA composite hydrogels in comparison with those of the neat polymer networks were investigated by uniaxial compression tests and steady and oscillatory measurements under small deformation conditions. The swelling behavior, the contact angle values, and the morphological features revealed by SEM and AFM analyses were well correlated with the uniaxial compression and rheological results. The compressive tests revealed an enhancement of the network rigidity by increasing the number of cryogenic cycles. On the other hand, tough and flexible polyphenol-loaded composite films were obtained for a weight ratio between XG and PVA of 1:1 and 10 v/v% polyphenol. The gel behavior was confirmed for all composite hydrogels, as the elastic modulus (G′) was significantly greater than the viscous modulus (G″) for the entire frequency range. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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19 pages, 5218 KiB

Open AccessArticle

Outstanding Sorption of Copper (II) Ions on Porous Phenothiazine-Imine-Chitosan Materials

by Andrei Bejan and Luminita Marin

Gels 2023, 9(2), 134; https://doi.org/10.3390/gels9020134 - 04 Feb 2023

Viewed by 1426

Abstract

The aim of this work was to investigate the ability of a solid-state material, prepared by crosslinking chitosan with a phenothiazine-based aldehyde, to remove copper (II) ions from aqueous solutions, in a fast and selective manner. The metal uptake experiments, including the retention, sensibility, and selectivity against eight different metal ions, were realized via batch adsorption studies. The capacity of the material to retain copper (II) ions was investigated by spectrophotometric measurements, using poly(ethyleneimine) complexation agent, which allowed detection in a concentration range of 5–500 µM. The forces driving the copper sorption were monitored using various methods, such as FTIR spectroscopy, X-ray diffraction, SEM-EDAX technique, and optical polarized microscopy, and the adsorption kinetics were assessed by fitting the in vitro sorption data on different mathematical models. The phenothiazine-imine-chitosan material proved high ability to recover copper from aqueous media, reaching a maximum retention capacity of 4.394 g Cu (II)/g adsorbent when using a 0.5 M copper solution, which is an outstanding value compared to other chitosan-based materials reported in the literature to this date. It was concluded that the high ability of the studied xerogel to retain Cu (II) ions was the result of both physio- and chemo-sorption processes. This particular behavior was favored on one hand by the porous nature of the material and on the other hand by the presence of amine, hydroxyl, imine, and amide groups with the role of copper ligands. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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18 pages, 3806 KiB

Open AccessArticle

Biomaterials Based on Chitosan and Polyvinyl Alcohol as a Drug Delivery System with Wound-Healing Effects

by Simona Petronela Gherman, Gabriela Biliuță, Adrian Bele, Alina Mirela Ipate, Raluca Ioana Baron, Lăcrămioara Ochiuz, Adrian Florin Șpac and Daniela Elena Zavastin

Gels 2023, 9(2), 122; https://doi.org/10.3390/gels9020122 - 01 Feb 2023

Cited by 9 | Viewed by 2464

Abstract

The excellent biological properties of chitosan (CS) together with the increased oxygen permeability of polyvinyl alcohol (PVA) were the prerequisites for the creation of a wound healing dressing that would also function as a system for L-arginine (L-arg) and caffeine (Caff) delivery. Using the freezing/thawing method, 12 hydrogels were obtained in PVA:CS polymer ratios of 90:10, 75:25, and 60:40, and all were loaded with L-arg, Caff, and the mixture of L-arg and Caff, respectively. Afterwards, an inorganic material (zeolite–Z) was added to the best polymeric ratio (75:25) and loaded with active substances. The interactions between the constituents of the hydrogels were analyzed by FTIR spectroscopy, the uniformity of the network was highlighted by the SEM technique, and the dynamic water vapor sorption capacity was evaluated. In the presence of the inorganic material, the release profile of the active substances is delayed, and in vitro permeation kinetics proves that the equilibrium state is not reached even after four hours. The synergy of the constituents in the polymer network recommends that they be used in medical applications, such as wound healing dressings. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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15 pages, 2937 KiB

Open AccessArticle

Cryostructuring of Polymeric Systems: 64. Preparation and Properties of Poly(vinyl alcohol)-Based Cryogels Loaded with Antimicrobial Drugs and Assessment of the Potential of Such Gel Materials to Perform as Gel Implants for the Treatment of Infected Wounds

by Olga Yu. Kolosova, Astemir I. Shaikhaliev, Mikhail S. Krasnov, Ivan M. Bondar, Egor V. Sidorskii, Elena V. Sorokina and Vladimir I. Lozinsky

Gels 2023, 9(2), 113; https://doi.org/10.3390/gels9020113 - 28 Jan 2023

Cited by 4 | Viewed by 1932

Abstract

Physical macroporous poly(vinyl alcohol)-based cryogels formed by the freeze–thaw technique without the use of any foreign cross-linkers are of significant interests for biomedical applications. In the present study, such gel materials loaded with the antimicrobial substances were prepared and their physicochemical properties were evaluated followed by an assessment of their potential to serve as drug carriers that can be used as implants for the treatment of infected wounds. The antibiotic Ceftriaxone and the antimycotic Fluconazole were used as antimicrobial agents. It was shown that the Ceftriaxone additives caused the up-swelling effects with respect to the cryogel matrix and some decrease in its heat endurance but did not result in a substantial change in the gel strength. With that, the drug release from the cryogel vehicle occurred without any diffusion restrictions, which was demonstrated by both the spectrophotometric recording and the microbiological agar diffusion technique. In turn, the in vivo biotesting of such drug-loaded cryogels also showed that these materials were able to function as rather efficient antimicrobial implants injected in the artificially infected model wounds of laboratory rabbits. These results confirmed the promising biomedical potential of similar implants. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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20 pages, 12722 KiB

Open AccessArticle

Oligo (Poly (Ethylene Glycol) Fumarate)-Based Multicomponent Cryogels for Neural Tissue Replacement

by Mohamed Zoughaib, Kenana Dayob, Svetlana Avdokushina, Marat I. Kamalov, Diana V. Salakhieva, Irina N. Savina, Igor A. Lavrov and Timur I. Abdullin

Gels 2023, 9(2), 105; https://doi.org/10.3390/gels9020105 - 25 Jan 2023

Cited by 2 | Viewed by 2061

Abstract

Synthetic hydrogels provide a promising platform to produce neural tissue analogs with improved control over structural, physical, and chemical properties. In this study, oligo (poly (ethylene glycol) fumarate) (OPF)-based macroporous cryogels were developed as a potential next-generation alternative to a non-porous OPF hydrogel previously proposed as an advanced biodegradable scaffold for spinal cord repair. A series of OPF cryogel conduits in combination with PEG diacrylate and 2-(methacryloyloxy) ethyl-trimethylammonium chloride (MAETAC) cationic monomers were synthesized and characterized. The contribution of each component to viscoelastic and hydration behaviors and porous structure was identified, and concentration relationships for these properties were revealed. The rheological properties of the materials corresponded to those of neural tissues and scaffolds, according to the reviewed data. A comparative assessment of adhesion, migration, and proliferation of neuronal cells in multicomponent cryogels was carried out to optimize cell-supporting characteristics. The results show that OPF-based cryogels can be used as a tunable synthetic scaffold for neural tissue repair with advantages over their hydrogel counterparts. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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13 pages, 2733 KiB

Open AccessArticle

Polypyrrole-Barium Ferrite Magnetic Cryogels for Water Purification

by Konstantin A. Milakin, Oumayma Taboubi, Udit Acharya, Miloslav Lhotka, Václav Pokorný, Magdalena Konefał, Olga Kočková, Jiřina Hromádková, Jiří Hodan and Patrycja Bober

Gels 2023, 9(2), 92; https://doi.org/10.3390/gels9020092 - 20 Jan 2023

Cited by 5 | Viewed by 1968

Abstract

Magnetic polypyrrole-gelatin-barium ferrite (PPy-G-BaFe) cryogels/aerogels were synthesized by one-step oxidative cryopolymerization of pyrrole in the presence of various fractions of barium ferrite (BaFe) nanoparticles, dispersed in aqueous gelatin solution. The successful incorporation of BaFe into the composites was confirmed by elemental analysis and scanning electron microscopy paired with an energy-dispersive X-ray detector. The maximum achieved content of BaFe in the resulting material was 3.9 wt%. The aerogels with incorporated BaFe had significantly higher specific surface area and conductivity, reaching 19.3 m² g⁻¹ and 4 × 10⁻⁴ S cm⁻¹, respectively, compared to PPy-G aerogel, prepared in the absence of BaFe (7.3 m² g⁻¹ and 1 × 10⁻⁵ S cm⁻¹). The model adsorption experiment using an anionic dye, Reactive Black 5, showed that magnetic PPy-G-BaFe aerogel, prepared at 10 wt% BaFe fraction, had significantly higher adsorption rate and higher adsorption capacity, compared to PPy-G (dye removal fraction 99.6% and 89.1%, respectively, after 23 h). Therefore, the prepared PPy-G-BaFe aerogels are attractive adsorbents for water purification due to their enhanced adsorption performance and the possibility of facilitated separation from solution by a magnetic field. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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13 pages, 2514 KiB

Open AccessArticle

Swelling and Antimicrobial Activity Characterization of a GO-Reinforced Gelatin—Whey Hydrogel

by Pompilia Mioara Purcea Lopes, Dumitriţa Moldovan, Radu Fechete, Doina Prodan, Carmen Rodica Pop, Ancuța M. Rotar and Violeta Popescu

Gels 2023, 9(1), 18; https://doi.org/10.3390/gels9010018 - 27 Dec 2022

Cited by 4 | Viewed by 1573

Abstract

Whey-based hydrogel samples with increasing concentrations of graphene oxide (GO) were studied, against a control sample (M), for swelling behavior in light of nuclear magnetic resonance (NMR) and mathematical models of the diffusion process and for antibacterial activity. Graphene oxide (GO) is an optimal filler for whey-based hydrogels, giving them improved mechanical and swelling properties at low concentrations. Crosslinking induces a certain stiffness of the hydrogels, which is why only the first part of the swelling process (<60%) follows the first-order model, while during the whole time interval, the swelling process follows the second-order diffusion model. The NMR relaxometry results are consistent with the swelling behavior of GO-reinforced whey–gelatin composite hydrogels, showing that higher GO concentrations induce a higher degree of cross-linking and, therefore, lower swelling capacity. Only hydrogel samples with higher GO concentrations demonstrated antibacterial activity. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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16 pages, 3269 KiB

Open AccessArticle

Novel Gemini Surfactant for Binding Eu(III)-Polyoxometalate into Hydrogels and Polymer Latexes

by Marin Micutz, Viorel Circu, Monica Ilis and Teodora Staicu

Gels 2022, 8(12), 786; https://doi.org/10.3390/gels8120786 - 30 Nov 2022

Cited by 1 | Viewed by 1558

Abstract

The incorporation of rare-earth ions into polymer matrices can lead to useful materials in various fields such as biomarkers, lasers, luminescent devices, optical storage materials, and so on. Methods of incorporation are either extremely simple, such as mixing the polymer and the ion of interest in adequate solvents, or more sophisticated such as synthesizing predesigned monomers that contain the rare-earth ion or binding the ion on an already formed polymer chain. Cationic gemini surfactants represent a class of surfactants that can be used to incorporate metal-oxygen cluster compounds by means of strong electrostatic interactions. In this study, first, a novel cationic gemini surfactant having double bonds on both side chains was designed and prepared. After characterization, the surfactant was used to synthesize hydrogels with different degrees of crosslinking and also as a surfmer in emulsion polymerization of methyl methacrylate. The resulted polymer matrices were able to bind europium-polyoxometalate Na₉[EuW₁₀O₃₆]^.32H₂O. In case of luminescent lanthanide ions, changing the microenvironment around the metal ion also changes the intensity of some emission peaks as well as other luminescent parameters. Investigation of emission spectra of Eu³⁺ indicates a decrease in the symmetry of the microenvironment, when the polyanions pass from water to latex, to surfactant solution, and to hydrogel. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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21 pages, 3113 KiB

Open AccessArticle

Designing and In Vitro Characterization of pH-Sensitive Aspartic Acid-Graft-Poly(Acrylic Acid) Hydrogels as Controlled Drug Carriers

by Muhammad Suhail, Chih-Wun Fang, I-Hui Chiu, Ming-Chia Hung, Quoc Lam Vu, I-Ling Lin and Pao-Chu Wu

Gels 2022, 8(8), 521; https://doi.org/10.3390/gels8080521 - 19 Aug 2022

Cited by 2 | Viewed by 2087

Abstract

Acetaminophen is an odorless and white crystalline powder drug, used in the management of fever, pain, and headache. The half-life of acetaminophen is very short; thus, multiple intakes of acetaminophen are needed in a day to maintain a constant pharmacological action for an extended period of time. Certain severe adverse effects are produced due to the frequent intake of acetaminophen, especially hepatotoxicity and skin rashes. Therefore, a drug carrier system is needed which not only prolongs the release of acetaminophen, but also enhances the patient compliance. Therefore, the authors prepared novel aspartic acid-graft-poly(acrylic acid) hydrogels for the controlled release of acetaminophen. The novelty of the prepared hydrogels is based on the incorporation of pH-sensitive monomer acrylic acid with polymer aspartic acid in the presence of ethylene glycol dimethacrylate. Due to the pH-sensitive nature, the release of acetaminophen was prolonged for an extended period of time by the developed hydrogels. Hence, a series of studies was carried out for the formulated hydrogels including sol-gel fraction, FTIR, dynamic swelling, polymer volume analysis, thermal analysis, percent porosity, SEM, in vitro drug release studies, and PXRD analysis. FTIR analysis confirmed the grafting of acrylic acid onto the backbone of aspartic acid and revealed the development of hydrogels. The thermal studies revealed the high thermal stability of the fabricated hydrogels as compared to pure aspartic acid. An irregular surface with a few pores was indicated by SEM. PXRD revealed the amorphous state of the developed hydrogels and confirmed the reduction in the crystallinity of the unreacted aspartic acid by the formulated hydrogels. An increase in gel fraction was observed with the increasing concentration of aspartic acid, acrylic acid, and ethylene glycol dimethacrylate due to the availability of a high amount of free radicals. The porosity study was influenced by the various compositions of developed hydrogels. Porosity was increased due to the enhancement in the concentrations of aspartic acid and acrylic acid, whereas it decreased with the increase in ethylene glycol dimethacrylate concentration. Similarly, the pH-responsive properties of hydrogels were evaluated by dynamic swelling and in vitro drug release studies at two different pH levels (1.2 and 7.4), and a greater dynamic swelling and acetaminophen release were exhibited at pH 7.4 as compared to pH 1.2. An increase in swelling, drug loading, and drug release was seen with the increased incorporation of aspartic acid and acrylic acid, whereas a decrease was detected with the increase in the concentration of ethylene glycol dimethacrylate. Conclusively, the formulated aspartic acid-based hydrogels could be employed as a suitable nonactive pharmaceutical ingredient for the controlled delivery of acetaminophen. Full article

(This article belongs to the Special Issue Properties of Hydrogels, Aerogels, and Cryogels Composites)

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