In-Situ Forming and Self-Healing Hydrogels

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Applications".

Deadline for manuscript submissions: closed (31 August 2020) | Viewed by 29443

Special Issue Editors


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Guest Editor
Department of Chemistry, University of Memphis, Memphis, TN, USA
Interests: biodegradable polymers; block copolymers; micelles; hydrogels; drug delivery systems; tissue regeneration; nanostructures; membranes; 3D printing
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Guest Editor
Institute for Advanced Co-Creation Studies at Osaka University, and Dept. of Macromolecular Science, Graduate School of Science at Osaka University, Osaka, Japan
Interests: macromolecular chemistry; supramolecular science; metallic catalyzed polymerization; host-guest chemistry; self-healing materials

Special Issue Information

Dear Colleagues,

In situ forming and self-healing hydrogels have drawn increasing interest for their broad applications. For example, in situ thermo-gelling materials can be injected into a body without surgery, and photoreactive solutions can be used as a bioink for stereolithography 3D printing. Self-healing hydrogels mimic the healing of tissues, recovering structural damages, and functions after being ruptured. Both forming and healing of these hydrogels can be achieved through chemical crosslinking (coupling reaction, coordination bond, oxidation-reduction, cleavable bond, etc.) and/or physical interactions (hydrophobic, electrostatic, host-guest interactions, hydrogen bonding, etc.). Many of such systems also respond to a variety of stimuli such as temperature, light, pH, biomolecules, and chemicals.

This Special Issue will overview recent development on in situ forming and self-healing hydrogels with a wide range of research focuses such as design, synthesis, structures, functions, mechanisms, and applications. Both original articles and reviews are welcome.

Prof. Tomoko Fujiwara
Prof. Yoshinori Takashima
Guest Editors

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Keywords

  • In situ forming hydrogels
  • Self-healing hydrogels
  • Stimuli-responsive hydrogels
  • Synthesis and functionalization
  • Chemical bonding
  • Physical interaction
  • Mechanisms
  • Host-guest chemistry
  • Self-assembly
  • Drug delivery
  • Injectable implants
  • 3D printing

Published Papers (5 papers)

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Research

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10 pages, 2870 KiB  
Article
Fluid–Structure Interaction Analysis of Perfusion Process of Vascularized Channels within Hydrogel Matrix Based on Three-Dimensional Printing
by Shuai Yang, Jianping Shi, Jiquan Yang, Chunmei Feng and Hao Tang
Polymers 2020, 12(9), 1898; https://doi.org/10.3390/polym12091898 - 24 Aug 2020
Cited by 1 | Viewed by 1799
Abstract
The rise of three-dimensional bioprinting technology provides a new way to fabricate in tissue engineering in vitro, but how to provide sufficient nutrition for the internal region of the engineered printed tissue has become the main obstacle. In vitro perfusion culture can not [...] Read more.
The rise of three-dimensional bioprinting technology provides a new way to fabricate in tissue engineering in vitro, but how to provide sufficient nutrition for the internal region of the engineered printed tissue has become the main obstacle. In vitro perfusion culture can not only provide nutrients for the growth of internal cells but also take away the metabolic wastes in time, which is an effective method to solve the problem of tissue engineering culture in vitro. Aiming at user-defined tissue engineering with internal vascularized channels obtained by three-dimensional printing experiment in the early stage, a simulation model was established and the in vitro fluid–structure interaction finite element analysis of tissue engineering perfusion process was carried out. Through fluid–structure interaction simulation, the hydrodynamic behavior and mechanical properties of vascularized channels in the perfusion process was discussed when the perfusion pressure, hydrogel concentration, and crosslinking density changed. The effects of perfusion pressure, hydrogel concentration, and crosslinking density on the flow velocity, pressure on the vascularized channels, and deformation of vascularized channels were analyzed. The simulation results provide a method to optimize the perfusion parameters of tissue engineering, avoiding the perfusion failure caused by unreasonable perfusion pressure and hydrogel concentration and promoting the development of tissue engineering culture in vitro. Full article
(This article belongs to the Special Issue In-Situ Forming and Self-Healing Hydrogels)
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11 pages, 1587 KiB  
Communication
Thiol-Substituted Poly(2-oxazoline)s with Photolabile Protecting Groups—Tandem Network Formation by Light
by Niklas Jung, Fiona Diehl and Ulrich Jonas
Polymers 2020, 12(8), 1767; https://doi.org/10.3390/polym12081767 - 07 Aug 2020
Cited by 9 | Viewed by 3319
Abstract
Herein, we present a novel polymer architecture based on poly(2-oxazoline)s bearing protected thiol functionalities, which can be selectively liberated by irradiation with UV light. Whereas free thiol groups can suffer from oxidation or other spontaneous reactions that degrade polymer performance, this strategy with [...] Read more.
Herein, we present a novel polymer architecture based on poly(2-oxazoline)s bearing protected thiol functionalities, which can be selectively liberated by irradiation with UV light. Whereas free thiol groups can suffer from oxidation or other spontaneous reactions that degrade polymer performance, this strategy with masked thiol groups offers the possibility of photodeprotection on demand with spatio-temporal control while maintaining polymer integrity. Here, we exploit this potential for a tandem network formation upon irradiation with UV light by thiol deprotection and concurrent crosslinking via thiol-ene coupling. The synthesis of the novel oxazoline monomer 2-{2-[(2-nitrobenzyl)thio]ethyl}-4,5-dihydrooxazole (NbMEtOxa) carrying 2-nitrobenzyl-shielded thiol groups and its cationic ring-opening copolymerization at varying ratios with 2-ethyl-2-oxazoline (EtOxa) is described. The tandem network formation was exemplarily demonstrated with the photoinitator 2-hydroxy-2-methylpropiophenone (HMPP) and pentaerythritol tetraacrylate (PETA), a commercially available, tetrafunctional vinyl crosslinker. The key findings of the conducted experiments indicate that a ratio of ~10% NbMEtOxa repeat units in the polymer backbone is sufficient for network formation and in-situ gelation in N,N-dimethylformamide. Full article
(This article belongs to the Special Issue In-Situ Forming and Self-Healing Hydrogels)
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13 pages, 2256 KiB  
Article
Self-Healing Thermoplastic Polyurethane Linked via Host-Guest Interactions
by Changming Jin, Garry Sinawang, Motofumi Osaki, Yongtai Zheng, Hiroyasu Yamaguchi, Akira Harada and Yoshinori Takashima
Polymers 2020, 12(6), 1393; https://doi.org/10.3390/polym12061393 - 22 Jun 2020
Cited by 35 | Viewed by 5748
Abstract
High toughness with self-healing ability has become the ultimate goal in materials research. Herein, thermoplastic polyurethane (TPU) was linked via host-guest (HG) interactions to increase its mechanical properties and self-healing ability. TPU linked via HG interactions was prepared by the step-growth bulk polymerization [...] Read more.
High toughness with self-healing ability has become the ultimate goal in materials research. Herein, thermoplastic polyurethane (TPU) was linked via host-guest (HG) interactions to increase its mechanical properties and self-healing ability. TPU linked via HG interactions was prepared by the step-growth bulk polymerization of hexamethylene diisocyanate (HDI), tetraethylene glycol (TEG), and HG interactions between permethylated amino βCD (PMeAmβCD) and adamantane amine (AdAm). TPU linked with 10 mol% of HG interactions (HG(10)) showed the highest rupture stress and fracture energy (GF) of 11 MPa and 25 MJ·m−3, which are almost 40-fold and 1500-fold, respectively, higher than those of non-functionalized TEG-based TPU (PU). Additionally, damaged HG(10) shows 87% recovery after heated for 7 min at 80 °C, and completely cut HG(10) shows 80% recovery after 60 min of reattachment at same temperature. The HG interactions in TPU are an important factor in stress dispersion, increasing both its mechanical and self-healing properties. The TPU linked via HG interactions has great promise for use in industrial materials in the near future. Full article
(This article belongs to the Special Issue In-Situ Forming and Self-Healing Hydrogels)
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Review

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36 pages, 7444 KiB  
Review
Polysaccharide-Based In Situ Self-Healing Hydrogels for Tissue Engineering Applications
by Sheila Maiz-Fernández, Leyre Pérez-Álvarez, Leire Ruiz-Rubio, Jose Luis Vilas-Vilela and Senentxu Lanceros-Mendez
Polymers 2020, 12(10), 2261; https://doi.org/10.3390/polym12102261 - 01 Oct 2020
Cited by 34 | Viewed by 5430
Abstract
In situ hydrogels have attracted increasing interest in recent years due to the need to develop effective and practical implantable platforms. Traditional hydrogels require surgical interventions to be implanted and are far from providing personalized medicine applications. However, in situ hydrogels offer a [...] Read more.
In situ hydrogels have attracted increasing interest in recent years due to the need to develop effective and practical implantable platforms. Traditional hydrogels require surgical interventions to be implanted and are far from providing personalized medicine applications. However, in situ hydrogels offer a wide variety of advantages, such as a non-invasive nature due to their localized action or the ability to perfectly adapt to the place to be replaced regardless the size, shape or irregularities. In recent years, research has particularly focused on in situ hydrogels based on natural polysaccharides due to their promising properties such as biocompatibility, biodegradability and their ability to self-repair. This last property inspired in nature gives them the possibility of maintaining their integrity even after damage, owing to specific physical interactions or dynamic covalent bonds that provide reversible linkages. In this review, the different self-healing mechanisms, as well as the latest research on in situ self-healing hydrogels, is presented, together with the potential applications of these materials in tissue regeneration. Full article
(This article belongs to the Special Issue In-Situ Forming and Self-Healing Hydrogels)
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27 pages, 8910 KiB  
Review
Implantation of Recyclability and Healability into Cross-Linked Commercial Polymers by Applying the Vitrimer Concept
by Mikihiro Hayashi
Polymers 2020, 12(6), 1322; https://doi.org/10.3390/polym12061322 - 10 Jun 2020
Cited by 72 | Viewed by 12545
Abstract
Vitrimers are a new class of cross-linked materials that are capable of network topology alternation through the associative dynamic bond-exchange mechanism, which has recently been invented to solve the problem of conventional cross-linked materials, such as poor recyclability and healability. Thus far, the [...] Read more.
Vitrimers are a new class of cross-linked materials that are capable of network topology alternation through the associative dynamic bond-exchange mechanism, which has recently been invented to solve the problem of conventional cross-linked materials, such as poor recyclability and healability. Thus far, the concept of vitrimers has been applied to various commercial polymers, e.g., polyesters, polylactides, polycarbonates, polydimethylsiloxanes, polydienes, polyurethanes, polyolefins, poly(meth)acrylates, and polystyrenes, by utilizing different compatible bond-exchange reactions. In this review article, the concept of vitrimers is described by clarifying the difference from thermoplastics and supramolecular systems; in addition, the term “associative bond-exchange” in vitrimers is explained by comparison with the “dissociative” term. Several useful functions attained by the vitrimer concept (including recyclability and healability) are demonstrated, and recent molecular designs of vitrimers are classified into groups depending on the types of molecular frameworks. This review specifically focuses on the vitrimer molecular designs with commercial polymer-based frameworks, which provide useful hints for the practical application of the vitrimer concept. Full article
(This article belongs to the Special Issue In-Situ Forming and Self-Healing Hydrogels)
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