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Gels
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Polysaccharide Hydrogels
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Polysaccharide Hydrogels

A special issue of Gels (ISSN 2310-2861).

Deadline for manuscript submissions: closed (29 March 2019) | Viewed by 59033

Special Issue Editor

Prof. Dr. Bjørn Torger Stokke

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Guest Editor
Biophysics and Medical Technology, Department of Physics, NTNU The Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
Interests: biopolymers; biopolymer mesoscale structure formation (PEC, multilayers, hydrogels, and fibrills); microfluidics assisted soft materials asssembly; hydrogel structure; bioresponsive hydrogels; biosensors; biopolymers at the single molecule level
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polysaccharides are an attractive source for hydrogels. This is due to various reasons, such as their abundant occurrence; they are almost exclusively originating from renewable sources, they offer a rich source in terms of building blocks and connectivity; polysaccharides exploit various types of principles for interactions supporting gel formation; they offer chemical groups readily modified to alter and enhance their functionality. Polysaccharides exist either as homopolymers or heteropolymers. In the latter group, variations in the number of constituents, their sequential arrangements and connectivity in terms of branching, can be found. This group of materials has also been reported to possess capacities that are biocompatible or that stimulate biological responses. There is an increasing interest in hydrogel materials, driven by a blend of the outlined facets. The particularities of the gel state, its formation, and how the molecular features of the polysaccharides underpin the hydrogel structure formation and final properties, are often challenging to elucidate. These challenges of generating a comprehensive understanding are best addresses using a multi-tool approach combining information at various length scales. Furthermore, the experimental approaches supplemented with theoretical and numerical studies, appear to provide a more comprehensive description.

The aim of this Special Issue is to bring together researchers that are active in field of polysaccharide hydrogels. Various topics are welcome, addressing, e.g., structure formation during gelation, structure function relationships, modification of polysaccharides and their use to exploit novel gelation mechanisms, applications of polysaccharide hydrogels, environmental aspects, hydrogel molding, printing with polysaccharide hydrogels, to mention a few.

Prof. Bjørn Torger Stokke
Guest Editor

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

  • Polysaccharide sol gel transition, gelation mechanisms, gel structure
  • Novel gelation mechanisms
  • Polysaccharide double network hydrogels, synergy
  • Polysaccharide hydrogel molding
  • Polysaccharide hydrogel printing
  • Applications of polysaccharide hydrogels

Published Papers (10 papers)

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Editorial

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2 pages, 154 KiB  
Editorial
Polysaccharide Hydrogels
by Bjørn Torger Stokke
Gels 2019, 5(3), 38; https://doi.org/10.3390/gels5030038 - 29 Jul 2019
Cited by 8 | Viewed by 3006
Abstract
Polysaccharides are a unique source of organic materials in terms of abundance, structural diversity and functionalities [...] Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)

Research

Jump to: Editorial, Review

19 pages, 2345 KiB  
Article
Mechanical Properties of Ca-Saturated Hydrogels with Functionalized Alginate
by Marianne Ø. Dalheim, Line Aa. Omtvedt, Isabel M. Bjørge, Anita Akbarzadeh, João F. Mano, Finn L. Aachmann and Berit L. Strand
Gels 2019, 5(2), 23; https://doi.org/10.3390/gels5020023 - 19 Apr 2019
Cited by 23 | Viewed by 5617
Abstract
In this work, the mechanical properties and stability of alginate hydrogels containing functionalized alginates (peptide and β-cyclodextrin) were studied. There is an increasing interest in the modification of alginates to add functions such as cell attachment and increased solubility of hydrophobic drugs, for [...] Read more.
In this work, the mechanical properties and stability of alginate hydrogels containing functionalized alginates (peptide and β-cyclodextrin) were studied. There is an increasing interest in the modification of alginates to add functions such as cell attachment and increased solubility of hydrophobic drugs, for better performance in tissue engineering and drug release, respectively. Functionalization was achieved in this study via periodate oxidation followed by reductive amination, previously shown to give a high and controllable degree of substitution. Young’s modulus and the stress at rupture of the hydrogels were in general lowered when exchanging native alginate with the modified alginate. Still, the gel strength could be adjusted by the fraction of modified alginate in the mixed hydrogels as well as the degree of oxidation. No notable difference in deformation at rupture was observed while syneresis was influenced by the degree of oxidation and possibly by the nature and amount of the grafted molecules. The mixed hydrogels were less stable than hydrogels with only native alginate, and modified alginate was released from the hydrogels. Furthermore, the hydrogels in general rather disintegrated than swelled upon saline treatments. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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12 pages, 3564 KiB  
Article
Supramolecular Strategy Effects on Chitosan Bead Stability in Acidic Media: A Comparative Study
by Andrew J. Worthen, Kelly S. Irving and Yakov Lapitsky
Gels 2019, 5(1), 11; https://doi.org/10.3390/gels5010011 - 25 Feb 2019
Cited by 15 | Viewed by 4462
Abstract
Chitosan beads attract interest in diverse applications, including drug delivery, biocatalysis and water treatment. They can be formed through several supramolecular pathways, ranging from phase inversion in alkaline solutions, to the ionic crosslinking of chitosan with multivalent anions, to polyelectrolyte or surfactant/polyelectrolyte complexation. [...] Read more.
Chitosan beads attract interest in diverse applications, including drug delivery, biocatalysis and water treatment. They can be formed through several supramolecular pathways, ranging from phase inversion in alkaline solutions, to the ionic crosslinking of chitosan with multivalent anions, to polyelectrolyte or surfactant/polyelectrolyte complexation. Many chitosan bead uses require control over their stability to dissolution. To help elucidate how this stability depends on the choice of supramolecular gelation chemistry, we present a comparative study of chitosan bead stability in acidic aqueous media using three common classes of supramolecular chitosan beads: (1) alkaline solution-derived beads, prepared through simple precipitation in NaOH solution; (2) ionically-crosslinked beads, prepared using tripolyphosphate (TPP); and (3) surfactant-crosslinked beads prepared via surfactant/polyelectrolyte complexation using sodium salts of dodecyl sulfate (SDS), caprate (NaC10) and laurate (NaC12). Highly variable bead stabilities with dissimilar sensitivities to pH were achieved using these methods. At low pH levels (e.g., pH 1.2), chitosan/SDS beads were the most stable, requiring roughly 2 days to dissolve. In weakly acidic media (at pH 3.0–5.0), however, chitosan/TPP beads exhibited the highest stability, remaining intact throughout the entire experiment. Beads prepared using only NaOH solution (i.e., without ionic crosslinking or surfactant complexation) were the least stable, except at pH 5.0, where the NaC10 and NaC12-derived beads dissolved slightly faster. Collectively, these findings provide further guidelines for tailoring supramolecular chitosan bead stability in acidic media. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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13 pages, 3287 KiB  
Article
Local Structure of Ca2+ Alginate Hydrogels Gelled via Competitive Ligand Exchange and Measured by Small Angle X-Ray Scattering
by Kyoko Yamamoto, Yoshiaki Yuguchi, Bjørn Torger Stokke, Pawel Sikorski and David C. Bassett
Gels 2019, 5(1), 3; https://doi.org/10.3390/gels5010003 - 09 Jan 2019
Cited by 18 | Viewed by 4498
Abstract
Alginates, being linear anionic co-polymers of 1,4-linked residues β-d-ManA (M) and α-l-GulA (G), are widely applied as hydrogel biomaterials due to their favourable in vivo biocompatibility and convenient ionic crosslinking. The “egg-box” model is the prevailing description of the [...] Read more.
Alginates, being linear anionic co-polymers of 1,4-linked residues β-d-ManA (M) and α-l-GulA (G), are widely applied as hydrogel biomaterials due to their favourable in vivo biocompatibility and convenient ionic crosslinking. The “egg-box” model is the prevailing description of the local structure of junction zones that form between the alginate chains and divalent cations, such as Ca2+, when ionic gelation occurs. In the present study we address to what extent signatures of lateral dimerization and further lateral association of junction zones also represent a valid model for the gelation of alginate using the recently reported method of competitive ligand exchange of chelated Ca2+ ions as a method for introducing gelling ions at constant pH. Small angle X-ray scattering with a q range from 0.1 to 3.3 nm−1 was employed to determine local structure in the hydrogel, using a custom-made fluid sample cell inserted in the X-ray beam. The scattering volume was intended to be localized to the contact zone between the two injected aqueous alginate solutions, and data was captured to resolve the kinetics of the structure formation at three different conditions of pH. The data show evolution of the local structure for the Ca2+ induced formation of junction zones in an alginate with 68% G residues, characterized by cross-sectional radii that could be accounted for by a two-component, broken rod like model. The evolution of the two component weight fractions apparently underpinned the connectivity, as reflected in the rheological data. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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11 pages, 2059 KiB  
Article
New Insights on the Role of Urea on the Dissolution and Thermally-Induced Gelation of Cellulose in Aqueous Alkali
by Luis Alves, Bruno Medronho, Alexandra Filipe, Filipe E. Antunes, Björn Lindman, Daniel Topgaard, Irina Davidovich and Yeshayahu Talmon
Gels 2018, 4(4), 87; https://doi.org/10.3390/gels4040087 - 11 Dec 2018
Cited by 27 | Viewed by 5114
Abstract
The gelation of cellulose in alkali solutions is quite relevant, but still a poorly understood process. Moreover, the role of certain additives, such as urea, is not consensual among the community. Therefore, in this work, an unusual set of characterization methods for cellulose [...] Read more.
The gelation of cellulose in alkali solutions is quite relevant, but still a poorly understood process. Moreover, the role of certain additives, such as urea, is not consensual among the community. Therefore, in this work, an unusual set of characterization methods for cellulose solutions, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR) and diffusion wave spectroscopy (DWS) were employed to study the role of urea on the dissolution and gelation processes of cellulose in aqueous alkali. Cryo-TEM reveals that the addition of urea generally reduces the presence of undissolved cellulose fibrils in solution. These results are consistent with PTssNMR data, which show the reduction and in some cases the absence of crystalline portions of cellulose in solution, suggesting a pronounced positive effect of the urea on the dissolution efficiency of cellulose. Both conventional mechanical macrorheology and microrheology (DWS) indicate a significant delay of gelation induced by urea, being absent until ca. 60 °C for a system containing 5 wt % cellulose, while a system without urea gels at a lower temperature. For higher cellulose concentrations, the samples containing urea form gels even at room temperature. It is argued that since urea facilitates cellulose dissolution, the high entanglement of the cellulose chains in solution (above the critical concentration, C*) results in a strong three-dimensional network. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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8 pages, 1827 KiB  
Communication
Evaluation of Hydrogels Based on Oxidized Hyaluronic Acid for Bioprinting
by Matthias Weis, Junwen Shan, Matthias Kuhlmann, Tomasz Jungst, Jörg Tessmar and Jürgen Groll
Gels 2018, 4(4), 82; https://doi.org/10.3390/gels4040082 - 09 Oct 2018
Cited by 33 | Viewed by 6578
Abstract
In this study, we evaluate hydrogels based on oxidized hyaluronic acid, cross-linked with adipic acid dihydrazide, for their suitability as bioinks for 3D bioprinting. Aldehyde containing hyaluronic acid (AHA) is synthesized and cross-linked via Schiff Base chemistry with bifunctional adipic acid dihydrazide (ADH) [...] Read more.
In this study, we evaluate hydrogels based on oxidized hyaluronic acid, cross-linked with adipic acid dihydrazide, for their suitability as bioinks for 3D bioprinting. Aldehyde containing hyaluronic acid (AHA) is synthesized and cross-linked via Schiff Base chemistry with bifunctional adipic acid dihydrazide (ADH) to form a mechanically stable hydrogel with good printability. Mechanical and rheological properties of the printed and casted hydrogels are tunable depending on the concentrations of AHA and ADH cross-linkers. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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16 pages, 2928 KiB  
Article
Photocrosslinked Dextran-Based Hydrogels as Carrier System for the Cells and Cytokines Induce Bone Regeneration in Critical Size Defects in Mice
by Ulrike Ritz, Marc Eberhardt, Anja Klein, Petra Frank, Hermann Götz, Alexander Hofmann, Pol Maria Rommens and Ulrich Jonas
Gels 2018, 4(3), 63; https://doi.org/10.3390/gels4030063 - 20 Jul 2018
Cited by 12 | Viewed by 4066
Abstract
Modified biomaterials have for years been the focus of research into establishing new bone substitutes. In our preceding in vitro study employing different cell cultures, we developed chemically and mechanically characterized hydrogels based on photocrosslinkable dextran derivatives and demonstrated their cytocompatibility and their [...] Read more.
Modified biomaterials have for years been the focus of research into establishing new bone substitutes. In our preceding in vitro study employing different cell cultures, we developed chemically and mechanically characterized hydrogels based on photocrosslinkable dextran derivatives and demonstrated their cytocompatibility and their beneficial effects on the proliferation of osteoblasts and endothelial cells. In the present in vivo study, we investigate photocrosslinked dextran-based hydrogels in critical size defects in mice to evaluate their potential as carrier systems for cells or for a specific angiogenesis enhancing cytokine to induce bone formation. We could demonstrate that, with optimized laboratory practice, the endotoxin content of hydrogels could be reduced below the Food and Drug Administration (FDA)-limit. Dextran-based hydrogels were either loaded with a monoculture of endothelial cells or a co-culture of human osteoblasts with endothelial cells, or with stromal-derived-growth factor (SDF-1). Scaffolds were implanted into a calvarial defect of critical size in mice and their impact on bone formation was assessed by µCt-analyses, histology and immunohistology. Our study demonstrates that promotion of angiogenesis either by SDF-1 or a monoculture of endothelial cells induces bone regeneration at a physiological level. These in vivo results indicate the potential of dextran-based hydrogel composites in bone regeneration to deliver cells and cytokines to the defect site. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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9 pages, 2819 KiB  
Article
Gelation and Structural Formation of Amylose by In Situ Neutralization as Observed by Small-Angle X-ray Scattering
by Kyoko Yamamoto, Shiho Suzuki, Shinichi Kitamura and Yoshiaki Yuguchi
Gels 2018, 4(3), 57; https://doi.org/10.3390/gels4030057 - 26 Jun 2018
Cited by 6 | Viewed by 4016
Abstract
The gelation and structural formation of two types of amylose in alkaline solution by in situ neutralization was monitored with time-resolved small-angle X-ray scattering (tr-SAXS). Sharp increases of SAXS profile in lower angle region were observed after gelation. The results showed that aggregation [...] Read more.
The gelation and structural formation of two types of amylose in alkaline solution by in situ neutralization was monitored with time-resolved small-angle X-ray scattering (tr-SAXS). Sharp increases of SAXS profile in lower angle region were observed after gelation. The results showed that aggregation of amylose chains led to a gel point with crystal growth. The aggregation appeared to function as a junction zone, and the aggregate structure depended on the molecular weight of amylose. A high-molecular-weight sample was fitted using a Debye-Bueche function, and a low-molecular-weight sample was fitted using a stretched exponential function. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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Review

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29 pages, 4166 KiB  
Review
Concepts for Developing Physical Gels of Chitosan and of Chitosan Derivatives
by Pasquale Sacco, Franco Furlani, Gaia De Marzo, Eleonora Marsich, Sergio Paoletti and Ivan Donati
Gels 2018, 4(3), 67; https://doi.org/10.3390/gels4030067 - 09 Aug 2018
Cited by 78 | Viewed by 10410
Abstract
Chitosan macro- and micro/nano-gels have gained increasing attention in recent years, especially in the biomedical field, given the well-documented low toxicity, degradability, and non-immunogenicity of this unique biopolymer. In this review we aim at recapitulating the recent gelling concepts for developing chitosan-based physical [...] Read more.
Chitosan macro- and micro/nano-gels have gained increasing attention in recent years, especially in the biomedical field, given the well-documented low toxicity, degradability, and non-immunogenicity of this unique biopolymer. In this review we aim at recapitulating the recent gelling concepts for developing chitosan-based physical gels. Specifically, we describe how nowadays it is relatively simple to prepare networks endowed with different sizes and shapes simply by exploiting physical interactions, namely (i) hydrophobic effects and hydrogen bonds—mostly governed by chitosan chemical composition—and (ii) electrostatic interactions, mainly ensured by physical/chemical chitosan features, such as the degree of acetylation and molecular weight, and external parameters, such as pH and ionic strength. Particular emphasis is dedicated to potential applications of this set of materials, especially in tissue engineering and drug delivery sectors. Lastly, we report on chitosan derivatives and their ability to form gels. Additionally, we discuss the recent findings on a lactose-modified chitosan named Chitlac, which has proved to form attractive gels both at the macro- and at the nano-scale. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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15 pages, 516 KiB  
Review
Application of Polysaccharide-Based Hydrogels as Probiotic Delivery Systems
by Iwona Kwiecień and Michał Kwiecień
Gels 2018, 4(2), 47; https://doi.org/10.3390/gels4020047 - 22 May 2018
Cited by 82 | Viewed by 9582
Abstract
Polysaccharide hydrogels have been increasingly utilized in various fields. In this review, we focus on polysaccharide-based hydrogels used as probiotic delivery systems. Probiotics are microorganisms with a positive influence on our health that live in the intestines. Unfortunately, probiotic bacteria are sensitive to [...] Read more.
Polysaccharide hydrogels have been increasingly utilized in various fields. In this review, we focus on polysaccharide-based hydrogels used as probiotic delivery systems. Probiotics are microorganisms with a positive influence on our health that live in the intestines. Unfortunately, probiotic bacteria are sensitive to certain conditions, such as the acidity of the gastric juice. Polysaccharide hydrogels can provide a physical barrier between encapsulated probiotic cells and the harmful environment enhancing the cells survival rate. Additionally, hydrogels improve survivability of probiotic bacteria not only under gastrointestinal track conditions but also during storage at various temperatures or heat treatment. The hydrogels described in this review are based on selected polysaccharides: alginate, κ-carrageenan, xanthan, pectin and chitosan. Some hydrogels are obtained from the mixture of two polysaccharides or polysaccharide and non-polysaccharide compounds. The article discusses the efficiency of probiotic delivery systems made of single polysaccharide, as well as of systems comprising more than one component. Full article
(This article belongs to the Special Issue Polysaccharide Hydrogels)
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