Advances in Cellulose-Based Hydrogels (2nd Edition)

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

Deadline for manuscript submissions: closed (20 November 2023) | Viewed by 31785

Special Issue Editors

Department of Engineering for Innovation, University of Salento, Via per Monteroni, 73100 Lecce, Italy
Interests: biomaterials; scaffold; tissue engineering; material characterization; viscoelasticity; hydrogels; green chemistry; natural polymers
Special Issues, Collections and Topics in MDPI journals
Department of Chemistry, Materials and Chemical Engineering “G. Natta”, Politecnico di Milano, 20131 Milano, Italy
Interests: cellulose nanofibers; biopolymers; aerogels; advanced cellulose-based systems; applied chemistry
Special Issues, Collections and Topics in MDPI journals
Department of Civil Engineering and Architecture (DICAr), Università degli Studi di Pavia, 27100 Pavia, Italy
Interests: hydrogels; gels; natural polymers; biopolymers; biomaterials; responsive polymers; smart polymers; cellulose; cellulose derivatives; materials characterization; rheology; scaffold; biomedical; tissue engineering; regenerative medicine
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Cellulose is the most abundant natural biopolymer on Earth. With an estimated annual production of ~1.5 x 1012 tons globally and the possibility of its extraction even from waste sources, it is considered an almost inexhaustible source of raw material capable of making up for the growing demand for environmentally friendly and biocompatible products.

Within this framework, cellulose-based hydrogels usually combine hydrophilicity, biodegradability, non-toxicity, and biocompatibility together with low costs and massive availability, which make them extremely attractive in both academic and industrial fields. Possible application fields include biomedical engineering (e.g., tissue engineering and regenerative medicine, drug/cell delivery systems, 3D printing and bioprinting), progress in smart systems (e.g., sensors, actuators, soft robotics) and stimuli-responsive systems (e.g., pH- or thermo-responsive hydrogels), the agricultural sector (e.g., soil conditioning, nutrient carriers, water reservoirs), and water purification.

This Special Issue aims to collect papers presenting the recent progress in cellulose-based hydrogels, including gels prepared from natural cellulose and its derivatives, cellulose graft co-polymers, and composite gels based on cellulose. We encourage submissions covering key aspects of cellulose-based hydrogels, including design, characterization, and application-focused research.

As Guest Editors, we kindly invite you to contribute a research paper or a review on any topic related to this theme.

Dr. Christian Demitri
Dr. Laura Riva
Dr. Lorenzo Bonetti
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

  • cellulose
  • nanocellulose
  • cellulose derivatives
  • cellulose-based composites
  • hydrogels
  • design
  • characterization
  • applications

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Published Papers (17 papers)

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19 pages, 7234 KiB  
Article
Facile Fabrication of NIR-Responsive Alginate/CMC Hydrogels Derived through IEDDA Click Chemistry for Photothermal–Photodynamic Anti-Tumor Therapy
by Ali Rizwan, Israr Ali, Sung-Han Jo, Trung Thang Vu, Yeong-Soon Gal, Yong Hyun Kim, Sang-Hyug Park and Kwon Taek Lim
Gels 2023, 9(12), 961; https://doi.org/10.3390/gels9120961 - 07 Dec 2023
Viewed by 1228
Abstract
Novel chemically cross-linked hydrogels derived from carboxymethyl cellulose (CMC) and alginate (Alg) were prepared through the utilization of the norbornene (Nb)–methyl tetrazine (mTz) click reaction. The hydrogels were designed to generate reactive oxygen species (ROS) from an NIR dye, indocyanine green (ICG), for [...] Read more.
Novel chemically cross-linked hydrogels derived from carboxymethyl cellulose (CMC) and alginate (Alg) were prepared through the utilization of the norbornene (Nb)–methyl tetrazine (mTz) click reaction. The hydrogels were designed to generate reactive oxygen species (ROS) from an NIR dye, indocyanine green (ICG), for combined photothermal and photodynamic therapy (PTT/PDT). The cross-linking reaction between Nb and mTz moieties occurred via an inverse electron-demand Diels–Alder chemistry under physiological conditions avoiding the need for a catalyst. The resulting hydrogels exhibited viscoelastic properties (G′ ~ 492–270 Pa) and high porosity. The hydrogels were found to be injectable with tunable mechanical characteristics. The ROS production from the ICG-encapsulated hydrogels was confirmed by DPBF assays, indicating a photodynamic effect (with NIR irradiation at 1–2 W for 5–15 min). The temperature of the ICG-loaded hydrogels also increased upon the NIR irradiation to eradicate tumor cells photothermally. In vitro cytocompatibility assessments revealed the non-toxic nature of CMC–Nb and Alg–mTz towards HEK-293 cells. Furthermore, the ICG-loaded hydrogels effectively inhibited the metabolic activity of Hela cells after NIR exposure. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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25 pages, 11434 KiB  
Article
Exceptionally Fast Temperature-Responsive, Mechanically Strong and Extensible Monolithic Non-Porous Hydrogels: Poly(N-isopropylacrylamide) Intercalated with Hydroxypropyl Methylcellulose
by Beata Strachota, Adam Strachota, Leana Vratović, Ewa Pavlova, Miroslav Šlouf, Samir Kamel and Věra Cimrová
Gels 2023, 9(12), 926; https://doi.org/10.3390/gels9120926 - 24 Nov 2023
Cited by 1 | Viewed by 1221
Abstract
Exceptionally fast temperature-responsive, mechanically strong, tough and extensible monolithic non-porous hydrogels were synthesized. They are based on divinyl-crosslinked poly(N-isopropyl-acrylamide) (PNIPAm) intercalated by hydroxypropyl methylcellulose (HPMC). HPMC was largely extracted after polymerization, thus yielding a ‘template-modified’ PNIPAm network intercalated with a modest residue of [...] Read more.
Exceptionally fast temperature-responsive, mechanically strong, tough and extensible monolithic non-porous hydrogels were synthesized. They are based on divinyl-crosslinked poly(N-isopropyl-acrylamide) (PNIPAm) intercalated by hydroxypropyl methylcellulose (HPMC). HPMC was largely extracted after polymerization, thus yielding a ‘template-modified’ PNIPAm network intercalated with a modest residue of HPMC. High contents of divinyl crosslinker and of HPMC caused a varying degree of micro-phase-separation in some products, but without detriment to mechanical or tensile properties. After extraction of non-fixed HPMC, the micro-phase-separated products combine superior mechanical properties with ultra-fast T-response (in 30 s). Their PNIPAm network was highly regular and extensible (intercalation effect), toughened by hydrogen bonds to HPMC, and interpenetrated by a network of nano-channels (left behind by extracted HPMC), which ensured the water transport rates needed for ultra-fast deswelling. Moreover, the T-response rate could be widely tuned by the degree of heterogeneity during synthesis. The fastest-responsive among our hydrogels could be of practical interest as soft actuators with very good mechanical properties (soft robotics), while the slower ones offer applications in drug delivery systems (as tested on the example of Theophylline), or in related biomedical engineering applications. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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13 pages, 13050 KiB  
Article
Injectable In Situ Crosslinking Hydrogel for Autologous Fat Grafting
by Kristin Oskarsdotter, Catherine T. Nordgård, Peter Apelgren, Karin Säljö, Anita A. Solbu, Edwin Eliasson, Sanna Sämfors, Henriette E. M. Sætrang, Lise Cathrine Asdahl, Eric M. Thompson, Christofer Troedsson, Stina Simonsson, Berit L. Strand, Paul Gatenholm and Lars Kölby
Gels 2023, 9(10), 813; https://doi.org/10.3390/gels9100813 - 12 Oct 2023
Viewed by 1076
Abstract
Autologous fat grafting is hampered by unpredictable outcomes due to high tissue resorption. Hydrogels based on enzymatically pretreated tunicate nanocellulose (ETC) and alginate (ALG) are biocompatible, safe, and present physiochemical properties capable of promoting cell survival. Here, we compared in situ and ex [...] Read more.
Autologous fat grafting is hampered by unpredictable outcomes due to high tissue resorption. Hydrogels based on enzymatically pretreated tunicate nanocellulose (ETC) and alginate (ALG) are biocompatible, safe, and present physiochemical properties capable of promoting cell survival. Here, we compared in situ and ex situ crosslinking of ETC/ALG hydrogels combined with lipoaspirate human adipose tissue (LAT) to generate an injectable formulation capable of retaining dimensional stability in vivo. We performed in situ crosslinking using two different approaches; inducing Ca2+ release from CaCO3 microparticles (CMPs) and physiologically available Ca2+ in vivo. Additionally, we generated ex situ-crosslinked, 3D-bioprinted hydrogel-fat grafts. We found that in vitro optimization generated a CMP-crosslinking system with comparable stiffness to ex situ-crosslinked gels. Comparison of outcomes following in vivo injection of each respective crosslinked hydrogel revealed that after 30 days, in situ crosslinking generated fat grafts with less shape retention than 3D-bioprinted constructs that had undergone ex situ crosslinking. However, CMP addition improved fat-cell distribution and cell survival relative to grafts dependent on physiological Ca2+ alone. These findings suggested that in situ crosslinking using CMP might promote the dimensional stability of injectable fat-hydrogel grafts, although 3D bioprinting with ex situ crosslinking more effectively ensured proper shape stability in vivo. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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12 pages, 2591 KiB  
Article
Highly Conductive, Anti-Freezing Hemicellulose-Based Hydrogels Prepared via Deep Eutectic Solvents and Their Applications
by Lisong Hu, Shishuai Gao, Lihui Zhao, Lili Dai, Daihui Zhang, Chunpeng Wang, Xuezhi Fang and Fuxiang Chu
Gels 2023, 9(9), 725; https://doi.org/10.3390/gels9090725 - 06 Sep 2023
Viewed by 1073
Abstract
Hydrogels containing renewable resources, such as hemicellulose, have received a lot of attention owing to their softness and electrical conductivity which could be applied in soft devices and wearable equipment. However, traditional hemicellulose-based hydrogels generally exhibit poor electrical conductivity and suffer from freezing [...] Read more.
Hydrogels containing renewable resources, such as hemicellulose, have received a lot of attention owing to their softness and electrical conductivity which could be applied in soft devices and wearable equipment. However, traditional hemicellulose-based hydrogels generally exhibit poor electrical conductivity and suffer from freezing at lower temperatures owing to the presence of a lot of water. In this study, we dissolved hemicellulose by employing deep eutectic solvents (DESs), which were prepared by mixing choline chloride and imidazole. In addition, hemicellulose-based DES hydrogels were fabricated via photo-initiated reactions of acrylamide and hemicellulose with N, N′-Methylenebisacrylamide as a crosslinking agent. The produced hydrogels demonstrated high electrical conductivity and anti-freezing properties. The conductivity of the hydrogels was 2.13 S/m at room temperature and 1.97 S/m at −29 °C. The hydrogel’s freezing point was measured by differential scanning calorimetry (DSC) to be −47.78 °C. Furthermore, the hemicellulose-based DES hydrogels can function as a dependable and sensitive strain sensor for monitoring a variety of human activities. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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10 pages, 3741 KiB  
Article
Preparation and Characterization of Porous Cellulose Acetate Nanofiber Hydrogels
by Lijie Jiang, Xingyu Huang, Chaochao Tian, Yidan Zhong, Ming Yan, Chen Miao, Ting Wu and Xiaofan Zhou
Gels 2023, 9(6), 484; https://doi.org/10.3390/gels9060484 - 13 Jun 2023
Cited by 7 | Viewed by 1978
Abstract
The currently reported methods for preparing cellulose acetate hydrogels use chemical reagents as cross-linking agents, and the prepared ones are non-porous structured cellulose acetate hydrogels. Nonporous cellulose acetate hydrogels limit the range of applications, such as limiting cell attachment and nutrient delivery in [...] Read more.
The currently reported methods for preparing cellulose acetate hydrogels use chemical reagents as cross-linking agents, and the prepared ones are non-porous structured cellulose acetate hydrogels. Nonporous cellulose acetate hydrogels limit the range of applications, such as limiting cell attachment and nutrient delivery in tissue engineering. This research creatively proposed a facile method to prepare cellulose acetate hydrogels with porous structures. Water was added to the cellulose acetate–acetone solution as an anti-solvent to induce the phase separation of the cellulose acetate–acetone solution to obtain a physical gel with a network structure, where the cellulose acetate molecules undergo re-arrangement during the replacement of acetone by water to obtain hydrogels. The SEM and BET test results showed that the hydrogels are relatively porous. The maximum pore size of the cellulose acetate hydrogel is 380 nm, and the specific surface area reaches 62 m2/g. The porosity of the hydrogel is significantly higher than that of the cellulose acetate hydrogel reported in the previous literature. The XRD results show that the nanofibrous morphology of cellulose acetate hydrogels is caused by the deacetylation reaction of cellulose acetate. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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17 pages, 7462 KiB  
Article
Cross-Linking of Oxidized Hydroxypropyl Cellulose in Paper: Influence of Molecular Weight and Polymer Distribution on Paper Wet Strength Development
by David Seelinger and Markus Biesalski
Gels 2023, 9(3), 206; https://doi.org/10.3390/gels9030206 - 09 Mar 2023
Cited by 1 | Viewed by 1490
Abstract
With the overarching aim for the development of sustainable, nontoxic wet strength agents for paper, a novel polymer gel system based on oxidized hydroxypropyl cellulose (keto-HPC) cross-linked with polyamines was investigated in detail to gain a deeper insight into the wet strength mechanism. [...] Read more.
With the overarching aim for the development of sustainable, nontoxic wet strength agents for paper, a novel polymer gel system based on oxidized hydroxypropyl cellulose (keto-HPC) cross-linked with polyamines was investigated in detail to gain a deeper insight into the wet strength mechanism. When applied to paper, this wet strength system significantly increases the relative wet strength by using only low amounts of polymer, and it is therefore comparable with established wet strength agents based on fossil resources, such as polyamidoamine epichlorohydrin resins. With the help of ultrasonic treatment, keto-HPC was degraded with respect to its molecular weight and further cross-linked in paper using polymeric amine-reactive counterparts. The resulting polymer-cross-linked paper mechanical properties were analyzed with respect to the dry and wet tensile strength, respectively. In addition, we analyzed the polymer distribution using fluorescence confocal laser scanning microscopy (CLSM). If high-molecular-weight samples are being used for cross-linking, we do find accumulation of the polymer mainly on the surface of the fibers and at fiber crossing points, accompanied with enhancing strong effects on paper’s wet tensile strength. In contrast, if low-molecular-weight (i.e., degraded) keto-HPC is being applied, the macromolecules are capable of entering the inner porous structure of the paper fibers, and almost no accumulation at the fiber crossing points is observed, which also results in a lowered wet paper tensile strength, respectively. This insight into wet strength mechanisms of the keto-HPC/polyamine system can thus lead to new opportunities for the development of alternative biobased wet strength agents where molecular weight dependence of the wet tensile properties allows for a fine tuning of mechanical properties in the wet state. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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33 pages, 7268 KiB  
Article
Bioengineered Water-Responsive Carboxymethyl Cellulose/Poly(vinyl alcohol) Hydrogel Hybrids for Wound Dressing and Skin Tissue Engineering Applications
by Nádia Sueli Vieira Capanema, Alexandra Ancelmo Piscitelli Mansur, Isadora Cota Carvalho, Sandhra Maria Carvalho and Herman Sander Mansur
Gels 2023, 9(2), 166; https://doi.org/10.3390/gels9020166 - 18 Feb 2023
Cited by 7 | Viewed by 2657
Abstract
The burden of chronic wounds is growing due to the increasing incidence of trauma, aging, and diabetes, resulting in therapeutic problems and increased medical costs. Thus, this study reports the synthesis and comprehensive characterization of water-responsive hybrid hydrogels based on carboxymethyl cellulose (CMC) [...] Read more.
The burden of chronic wounds is growing due to the increasing incidence of trauma, aging, and diabetes, resulting in therapeutic problems and increased medical costs. Thus, this study reports the synthesis and comprehensive characterization of water-responsive hybrid hydrogels based on carboxymethyl cellulose (CMC) and poly(vinyl alcohol) (PVA) using citric acid (CA) as the chemical crosslinking agent, with tunable physicochemical properties suitable to be applied as a wound dressing for soft tissue engineering applications. They were produced through an eco-friendly process under mild conditions. The hydrogels were designed and produced with flexible swelling degree properties through the selection of CMC molecular mass (Mw = 250 and 700 kDa) and degree of functionalization (DS = 0.81), degree of hydrolysis of PVA (DH > 99%, Mw = 84–150 kDa) associated with synthesis parameters, CMC/PVA ratio and extension of chemical crosslinking (CA/CMC:PVA ratio), for building engineered hybrid networks. The results demonstrated that highly absorbent hydrogels were produced with swelling degrees ranging from 100% to 5000%, and gel fraction from 40% to 80%, which significantly depended on the concentration of CA crosslinker and the presence of PVA as the CMC-based network modifier. The characterizations indicated that the crosslinking mechanism was mostly associated with the chemical reaction of CA carboxylic groups with hydroxyl groups of CMC and PVA polymers forming ester bonds, rendering a hybrid polymeric network. These hybrid hydrogels also presented hydrophilicity, permeability, and structural features dependent on the degree of crosslinking and composition. The hydrogels were cytocompatible with in vitro cell viability responses of over 90% towards model cell lines. Hence, it is envisioned that this research provides a simple strategy for producing biocompatible hydrogels with tailored properties as wound dressings for assisting chronic wound healing and skin tissue engineering applications. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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25 pages, 11896 KiB  
Article
Swelling and Viscoelastic Properties of Cellulose-Based Hydrogels Prepared by Free Radical Polymerization of Dimethylaminoethyl Methacrylate in Cellulose Solution
by Roko Blažic, Katarina Marušić and Elvira Vidović
Gels 2023, 9(2), 94; https://doi.org/10.3390/gels9020094 - 21 Jan 2023
Cited by 6 | Viewed by 1869
Abstract
The grafting of a stimuli-responsive polymer (poly(dimethylaminoethyl methacrylate)) onto cellulose was achieved by performing free radical polymerization of a vinyl/divinyl monomer in cellulose solution. The grafting and crosslinking efficiency in the material have been increased by subsequent irradiation of the samples with ionizing [...] Read more.
The grafting of a stimuli-responsive polymer (poly(dimethylaminoethyl methacrylate)) onto cellulose was achieved by performing free radical polymerization of a vinyl/divinyl monomer in cellulose solution. The grafting and crosslinking efficiency in the material have been increased by subsequent irradiation of the samples with ionizing radiation (doses of 10, 30, or 100 kGy). The relative amount of poly(dimethylaminoethyl methacrylate) in the prepared hydrogels was determined by infrared spectroscopy. The swelling behavior of the hydrogels was studied thoroughly, including microgelation extent, equilibrium swelling, and reswelling degree, as well as the dependence on the gelation procedure. The dynamic viscoelastic behavior of prepared hydrogels was also studied. The tan δ values indicate a solid-like behavior while the obtained hydrogels have a complex modulus in the range of 14–39 kPa, which is suitable for hydrogels used in biomedical applications. In addition, the incorporation of Ag particles and the adsorption of Fe3+ ions were tested to evaluate the additional functionalities of the prepared hydrogels. It was found that the introduction of PDMAEMA to the hydrogels enhanced their ability to synthesize Ag particles and absorb Fe3+ ions, providing a platform for the potential preparation of hydrogels for the treatment of wounds. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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15 pages, 3034 KiB  
Article
Opportunities for Ivory Nut Residue Valorization as a Source of Nanocellulose Colloidal Suspensions
by Enrique Javier Carvajal-Barriga, Jean-Luc Putaux, Pablo Martín-Ramos, Jennifer Simbaña, Patricia Portero-Barahona and Jesús Martín-Gil
Gels 2023, 9(1), 32; https://doi.org/10.3390/gels9010032 - 30 Dec 2022
Cited by 3 | Viewed by 1565
Abstract
Ivory nut seeds have been traditionally exploited in Central and South America for obtaining vegetable ivory. The residues from this industry are susceptible to valorization as a source of fatty acids (by organic extraction) and mannans (by alkaline dissolution and regeneration). Nonetheless, cellulose [...] Read more.
Ivory nut seeds have been traditionally exploited in Central and South America for obtaining vegetable ivory. The residues from this industry are susceptible to valorization as a source of fatty acids (by organic extraction) and mannans (by alkaline dissolution and regeneration). Nonetheless, cellulose may also be recovered at the end of this fractionation process by acid hydrolysis and functionalization, with associated advantages over other lignocellulosic sources due to the absence of lignin in the endospermic tissue. In this work, various experimental parameters (sulfuric acid concentration, temperature, and hydrolysis time) were investigated to optimize the processing conditions for preparing stable nanocellulose suspensions after ultrasonication. The most stable nanocellulose gel (1 wt% solid content) was obtained after 4-h hydrolysis at 60 °C with 8 M H2SO4 and was characterized by using complementary tech-niques, including dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), nano-fibril sulfation measurements, vibrational and solid-state nuclear magnetic resonance (CP/MAS 13C-NMR) spectroscopies, and thermal analysis. This nanocellulose hydrogel is susceptible to further utilization in various applications and fields, e.g., in agricul-ture for controlling the release of agrochemicals, in pharmaceutics for developing new dosage forms, and in the treatment of wastewater from the textile and paper industries. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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14 pages, 5737 KiB  
Article
Double-Network Hydrogel Films Based on Cellulose Derivatives and κ-Carrageenan with Enhanced Mechanical Strength and Superabsorbent Properties
by Jiseon Kang and Seok Il Yun
Gels 2023, 9(1), 20; https://doi.org/10.3390/gels9010020 - 27 Dec 2022
Cited by 2 | Viewed by 1971
Abstract
Covalently crosslinked sodium carboxymethyl cellulose (CMC)–hydroxyethyl cellulose (HEC) hydrogel films were prepared using citric acid (CA) as the crosslinking agent. Thereafter, the physically crosslinked κ-carrageenan (κ-CG) polymer was introduced into the CMC–HEC hydrogel structure, yielding κ-CG/CMC–HEC double network (DN) hydrogels. The κ-CG physical [...] Read more.
Covalently crosslinked sodium carboxymethyl cellulose (CMC)–hydroxyethyl cellulose (HEC) hydrogel films were prepared using citric acid (CA) as the crosslinking agent. Thereafter, the physically crosslinked κ-carrageenan (κ-CG) polymer was introduced into the CMC–HEC hydrogel structure, yielding κ-CG/CMC–HEC double network (DN) hydrogels. The κ-CG physical network provided sacrificial bonding, which effectively dissipated the stretching energy, resulting in an increase in the tensile modulus, tensile strength, and fracture energy of the DN hydrogels by 459%, 305%, and 398%, respectively, compared with those of the CMC–HEC single network (SN) hydrogel. The dried hydrogels exhibited excellent water absorbency with a maximum water-absorption capacity of 66 g/g in distilled water. Compared with the dried covalent SN gel, the dried DN hydrogels exhibited enhanced absorbency under load, attributed to their improved mechanical properties. The water-absorption capacities and kinetics were dependent on the size of the dried gel and the pH of the water. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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12 pages, 3523 KiB  
Article
Viscoelastic Analysis of Pectin Hydrogels Regenerated from Citrus Pomelo Waste by Gelling Effects of Calcium Ion Crosslinking at Different pHs
by Tu Minh Tran Vo, Takaomi Kobayashi and Pranut Potiyaraj
Gels 2022, 8(12), 814; https://doi.org/10.3390/gels8120814 - 10 Dec 2022
Cited by 7 | Viewed by 1572
Abstract
Pectin was extracted from citrus pomelo waste, and the effects of calcium ions (Ca2+) on the gelation and hydrogels properties were investigated over a pH range of 3.2–8 by using viscoelastic analysis. The gelatinization of Ca2+-pectin was examined at [...] Read more.
Pectin was extracted from citrus pomelo waste, and the effects of calcium ions (Ca2+) on the gelation and hydrogels properties were investigated over a pH range of 3.2–8 by using viscoelastic analysis. The gelatinization of Ca2+-pectin was examined at concentrations of 0.9, 1.8, 2.4, and 3.6 M of Ca2+ in aqueous pectin solutions of 1%, 2%, 3%, and 4%. The gel transition of Ca2+-pectin solution to hydrogels was determined by measuring the storage modulus (G’) and loss modulus (G”) under mechanical strain from 0.01 to 100%. In a hydrogel of 3% pectin at Ca2+ = 2.4 M, as pH increased to 7, the G’ at 0.01 strain % was 3 × 104 Pa, and 3 × 103 Pa at pH 5, indicating that the crosslinking weakened at acidic pH. Due to the crosslinking between the calcium ions and the ionized carboxylic acid groups of pectin, the resulting hydrogel became stiff. When the mechanical strain % was in the range of 0.01–1%, G’ was unchanged and G” was an order of magnitude smaller than G’, indicating that the mechanical stress was relieved by the gel. In the range of 1–100%, the gel deformation progressed and both the moduli values were dropped. Collapse from the gel state to the solution state occurred at 1–10 strain %, but the softer hydrogels with G’ of 103 Pa had a larger strain % than the stiffer hydrogels with G’ of 104 Pa. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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16 pages, 3192 KiB  
Article
Inorganic/Biopolymers Hybrid Hydrogels Dual Cross-Linked for Bone Tissue Regeneration
by Alexandra I. Cernencu, Andreea I. Dinu, Sorina Dinescu, Roxana Trușcă, Mircea Istodorescu, Adriana Lungu, Izabela C. Stancu and Horia Iovu
Gels 2022, 8(12), 762; https://doi.org/10.3390/gels8120762 - 23 Nov 2022
Cited by 2 | Viewed by 1507
Abstract
In tissue engineering, the potential of re-growing new tissue has been considered, however, developments towards such clinical and commercial outcomes have been modest. One of the most important elements here is the selection of a biomaterial that serves as a “scaffold” for the [...] Read more.
In tissue engineering, the potential of re-growing new tissue has been considered, however, developments towards such clinical and commercial outcomes have been modest. One of the most important elements here is the selection of a biomaterial that serves as a “scaffold” for the regeneration process. Herein, we designed hydrogels composed of two biocompatible natural polymers, namely gelatin with photopolymerizable functionalities and a pectin derivative amenable to direct protein conjugation. Aiming to design biomimetic hydrogels for bone regeneration, this study proposes double-reinforcement by way of inorganic/biopolymer hybrid filling composed of Si-based compounds and cellulose nanofibers. To attain networks with high flexibility and elastic modulus, a double-crosslinking strategy was envisioned—photochemical and enzyme-mediated conjugation reactions. The dual cross-linked procedure will generate intra- and intermolecular interactions between the protein and polysaccharide and might be a resourceful strategy to develop innovative scaffolding materials. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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16 pages, 2939 KiB  
Article
(Hydroxypropyl)methyl Cellulose-Chitosan Film as a Matrix for Lipase Immobilization—Part ΙΙ: Structural Studies
by Evdokia Vassiliadi, Marta Tsirigotis-Maniecka, Henry E. Symons, Pierangelo Gobbo, Frédéric Nallet, Aristotelis Xenakis and Maria Zoumpanioti
Gels 2022, 8(9), 595; https://doi.org/10.3390/gels8090595 - 17 Sep 2022
Cited by 1 | Viewed by 2015
Abstract
The present work reports on the structural study of a film made of a hybrid blend of biopolymers used as an enzyme carrier. A cellulose derivative (HPMC) and chitosan (CS) were combined in order to formulate a film on which Mucor miehei lipase [...] Read more.
The present work reports on the structural study of a film made of a hybrid blend of biopolymers used as an enzyme carrier. A cellulose derivative (HPMC) and chitosan (CS) were combined in order to formulate a film on which Mucor miehei lipase was immobilized. The film was successfully used as a biocatalyst; however, little is known about the structure of the system. Therefore, small-angle X-ray scattering, Fourier transform infrared spectroscopy (FTIR), optical microscopy, and scanning electron microscopy (SEM), as well as microindentation measurements, were used to shed light on the structure of the promising biocatalyst. Among the results, intermolecular hydrogen bonds were observed between the amide groups of the two polymers and the lipase. The presence of the enzyme does not seem to affect the mechanical properties of the matrix. The used film after 35 cycles of reaction seemed to be fatigued and had lost part of its humidity, explaining the reduction of the enzyme activity. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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21 pages, 31099 KiB  
Article
Hydroxypropyl Cellulose/Pluronic-Based Composite Hydrogels as Biodegradable Mucoadhesive Scaffolds for Tissue Engineering
by Daniela Filip, Doina Macocinschi, Mirela-Fernanda Zaltariov, Bianca-Iulia Ciubotaru, Alexandra Bargan, Cristian-Dragos Varganici, Ana-Lavinia Vasiliu, Dragos Peptanariu, Mihaela Balan-Porcarasu and Mihaela-Madalina Timofte-Zorila
Gels 2022, 8(8), 519; https://doi.org/10.3390/gels8080519 - 19 Aug 2022
Cited by 11 | Viewed by 1973
Abstract
Recently, the development of new materials with the desired characteristics for functional tissue engineering, ensuring tissue architecture and supporting cellular growth, has gained significant attention. Hydrogels, which possess similar properties to natural cellular matrixes, being able to repair or replace biological tissues and [...] Read more.
Recently, the development of new materials with the desired characteristics for functional tissue engineering, ensuring tissue architecture and supporting cellular growth, has gained significant attention. Hydrogels, which possess similar properties to natural cellular matrixes, being able to repair or replace biological tissues and support the healing process through cellular proliferation and viability, are a challenge when designing tissue scaffolds. This paper provides new insights into hydrogel-based polymeric blends (hydroxypropyl cellulose/Pluronic F68), aiming to evaluate the contributions of both components in the development of new tissue scaffolds. In order to study the interactions within the hydrogel blends, FTIR and 1HNMR spectroscopies were used. The porosity and the behavior in moisture medium were highlighted by SEM and DVS analyses. The biodegradability of the hydrogel blends was studied in a simulated biological medium. The hydrogel composition was determinant for the scaffold behavior: the HPC component was found to have a great influence on the BET and GAB areas, on the monolayer values estimated from sorption–desorption isotherms and on mucoadhesivity on small intestine mucosa, while the Pluronic F68 component improved the thermal stability. All blends were also found to have good mechanical strength and increased biocompatibility on the NHDF cell line. Based on their particular compositions and increased mucoadhesivity on small intestine mucosa, these polymeric blends could be effective in the repair or recovery of damaged cell membranes (due to the contribution of Pluronic F68) or in control drug-delivery intestinal formulations. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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Review

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27 pages, 8522 KiB  
Review
Recent Advances in Cellulose-Based Hydrogels Prepared by Ionic Liquid-Based Processes
by Siriporn Taokaew
Gels 2023, 9(7), 546; https://doi.org/10.3390/gels9070546 - 05 Jul 2023
Cited by 1 | Viewed by 2104
Abstract
This review summarizes the recent advances in preparing cellulose hydrogels via ionic liquid-based processes and the applications of regenerated cellulose hydrogels/iongels in electrochemical materials, separation membranes, and 3D printing bioinks. Cellulose is the most abundant natural polymer, which has attracted great attention due [...] Read more.
This review summarizes the recent advances in preparing cellulose hydrogels via ionic liquid-based processes and the applications of regenerated cellulose hydrogels/iongels in electrochemical materials, separation membranes, and 3D printing bioinks. Cellulose is the most abundant natural polymer, which has attracted great attention due to the demand for eco-friendly and sustainable materials. The sustainability of cellulose products also depends on the selection of the dissolution solvent. The current state of knowledge in cellulose preparation, performed by directly dissolving in ionic liquids and then regenerating in antisolvents, as described in this review, provides innovative ideas from the new findings presented in recent research papers and with the perspective of the current challenges. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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24 pages, 39267 KiB  
Review
State-of-the-Art Insights and Potential Applications of Cellulose-Based Hydrogels in Food Packaging: Advances towards Sustainable Trends
by Ajit Kumar Singh, Pontree Itkor and Youn Suk Lee
Gels 2023, 9(6), 433; https://doi.org/10.3390/gels9060433 - 24 May 2023
Cited by 4 | Viewed by 2357
Abstract
Leveraging sustainable packaging resources in the circular economy framework has gained significant attention in recent years as a means of minimizing waste and mitigating the negative environmental impact of packaging materials. In line with this progression, bio-based hydrogels are being explored for their [...] Read more.
Leveraging sustainable packaging resources in the circular economy framework has gained significant attention in recent years as a means of minimizing waste and mitigating the negative environmental impact of packaging materials. In line with this progression, bio-based hydrogels are being explored for their potential application in a variety of fields including food packaging. Hydrogels are three-dimensional, hydrophilic networks composed of a variety of polymeric materials linked by chemical (covalent bonds) or physical (non-covalent interactions) cross-linking. The unique hydrophilic nature of hydrogels provides a promising solution for food packaging systems, specifically in regulating moisture levels and serving as carriers for bioactive substances, which can greatly affect the shelf life of food products. In essence, the synthesis of cellulose-based hydrogels (CBHs) from cellulose and its derivatives has resulted in hydrogels with several appealing features such as flexibility, water absorption, swelling capacity, biocompatibility, biodegradability, stimuli sensitivity, and cost-effectiveness. Therefore, this review provides an overview of the most recent trends and applications of CBHs in the food packaging sector including CBH sources, processing methods, and crosslinking methods for developing hydrogels through physical, chemical, and polymerization. Finally, the recent advancements in CBHs, which are being utilized as hydrogel films, coatings, and indicators for food packaging applications, are discussed in detail. These developments have great potential in creating sustainable packaging systems. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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40 pages, 6036 KiB  
Review
Insights on Some Polysaccharide Gel Type Materials and Their Structural Peculiarities
by Ioana Alexandra Duceac, Magdalena-Cristina Stanciu, Marioara Nechifor, Fulga Tanasă and Carmen-Alice Teacă
Gels 2022, 8(12), 771; https://doi.org/10.3390/gels8120771 - 26 Nov 2022
Cited by 7 | Viewed by 2743
Abstract
Global resources have to be used in responsible ways to ensure the world’s future need for advanced materials. Ecologically friendly functional materials based on biopolymers can be successfully obtained from renewable resources, and the most prominent example is cellulose, the well-known most abundant [...] Read more.
Global resources have to be used in responsible ways to ensure the world’s future need for advanced materials. Ecologically friendly functional materials based on biopolymers can be successfully obtained from renewable resources, and the most prominent example is cellulose, the well-known most abundant polysaccharide which is usually isolated from highly available biomass (wood and wooden waste, annual plants, cotton, etc.). Many other polysaccharides originating from various natural resources (plants, insects, algae, bacteria) proved to be valuable and versatile starting biopolymers for a wide array of materials with tunable properties, able to respond to different societal demands. Polysaccharides properties vary depending on various factors (origin, harvesting, storage and transportation, strategy of further modification), but they can be processed into materials with high added value, as in the case of gels. Modern approaches have been employed to prepare (e.g., the use of ionic liquids as “green solvents”) and characterize (NMR and FTIR spectroscopy, X ray diffraction spectrometry, DSC, electronic and atomic force microscopy, optical rotation, circular dichroism, rheological investigations, computer modelling and optimization) polysaccharide gels. In the present paper, some of the most widely used polysaccharide gels will be briefly reviewed with emphasis on their structural peculiarities under various conditions. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels (2nd Edition))
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