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Smart Hydrogels: From Rational Design to Applications

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

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 26843

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Special Issue Editors

Dr. Bapan Pramanik

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Guest Editor

Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheba 8455902, Israel
Interests: hydrogels; self-assembly; peptide nanostructures; nanomaterials; system chemistry
Special Issues, Collections and Topics in MDPI journals

Dr. Lucy Vojtová

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Guest Editor

CEITE—Central European Institute of Technology, Brno University of Technology, 612 00 Brno, Czech Republic
Interests: biomaterials; synthetic polymers; natural polymers; hydrogels; implantology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue on “Smart Hydrogels: From Rational Design to Applications” is focuses on fundamental aspects and recent developments in rational design, synthesis, characterization, self-assembly mechanism, and applications of hydrogels in the chemical and biological field.

Smart hydrogels are an important class of soft materials with a three-dimensional polymer network in which a large amount of water is entrapped. Interestingly, in the presence of physical stimuli such as heat, light, electric field, magnetic field, and chemical stimuli such as pH, enzymes, redox, ions, etc., these smart hydrogels change their physiochemical properties such as transparency or color, phase behavior, conductivity, and shape or rheological properties. In the last few decades, smart hydrogels have been at the forefront of advanced materials because of their outstanding applications in sensors, programmable drug delivery, actuators, and tissue engineering. Smart hydrogels can be prepared by rational design of appropriate peptide sequences, composite material with the help of extracellular matrix (ECM) proteins, biologically suitable polymer, collagen-like peptide (CLP), etc. In addition, the self-assembly propensity of these smart hydrogels to form nanoscale architecture plays an important role in biomedical applications.

It is incredibly important to cover all aspects of smart hydrogels in one issue, and this Special Issue will cover a few representative examples, also including review articles of recent findings (preferably within last 5 years) explaining the progress in this advanced field with the aim of helping scientists worldwide. Computational science related to smart hydrogels is also welcomed in this Special Issue.

Dr. Bapan Pramanik
Dr. Lucy Vojtová
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

peptides
polymers
composite materials
smart hydrogels
stimuli-responsive
self-assembly
rheological behavior
drug delivery
tissue engineering

Published Papers (10 papers)

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Research

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17 pages, 3535 KiB

Open AccessArticle

Synthesis and Characterisation of Hydrogels Based on Poly (N-Vinylcaprolactam) with Diethylene Glycol Diacrylate

by Elaine Halligan, Billy Shu Hieng Tie, Declan Mary Colbert, Mohamad Alsaadi, Shuo Zhuo, Gavin Keane and Luke M. Geever

Gels 2023, 9(6), 439; https://doi.org/10.3390/gels9060439 - 25 May 2023

Cited by 3 | Viewed by 1366

Abstract

Poly (N-vinylcaprolactam) is a polymer that is biocompatible, water-soluble, thermally sensitive, non-toxic, and nonionic. In this study, the preparation of hydrogels based on Poly (N-vinylcaprolactam) with diethylene glycol diacrylate is presented. The N-Vinylcaprolactam-based hydrogels are synthesised by using a photopolymerisation technique using diethylene glycol diacrylate as a crosslinking agent, and Diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide as a photoinitiator. The structure of the polymers is investigated via Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy. The polymers are further characterised using differential scanning calorimetry and swelling analysis. This study is conducted to determine the characteristics of P (N-vinylcaprolactam) with diethylene glycol diacrylate, including the addition of Vinylacetate or N-Vinylpyrrolidone, and to examine the effects on the phase transition. Although various methods of free-radical polymerisation have synthesised the homopolymer, this is the first study to report the synthesis of Poly (N-vinylcaprolactam) with diethylene glycol diacrylate by using free-radical photopolymerisation, using Diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide to initiate the reaction. FTIR analysis shows that the NVCL-based copolymers are successfully polymerised through UV photopolymerisation. DSC analysis indicates that increasing the concentration of crosslinker results in a decrease in the glass transition temperature. Swelling analysis displays that the lower the concentration of crosslinker present in the hydrogel, the quicker the hydrogels reach their maximum swelling ratio. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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21 pages, 4459 KiB

Open AccessArticle

A Novel Bio-Adhesive Mesh System for Medical Implant Applications: In Vivo Assessment in a Rabbit Model

by Melinda Harman, Kevin Champaigne, William Cobb, Xinyue Lu, Varun Chawla, Liying Wei, Igor Luzinov, O. Thompson Mefford and Jiro Nagatomi

Gels 2023, 9(5), 372; https://doi.org/10.3390/gels9050372 - 1 May 2023

Cited by 2 | Viewed by 1664

Abstract

Injectable surgical sealants and adhesives, such as biologically derived fibrin gels and synthetic hydrogels, are widely used in medical products. While such products adequately adhere to blood proteins and tissue amines, they have poor adhesion with polymer biomaterials used in medical implants. To address these shortcomings, we developed a novel bio-adhesive mesh system utilizing the combined application of two patented technologies: a bifunctional poloxamine hydrogel adhesive and a surface modification technique that provides a poly-glycidyl methacrylate (PGMA) layer grafted with human serum albumin (HSA) to form a highly adhesive protein surface on polymer biomaterials. Our initial in vitro tests confirmed significantly improved adhesive strength for PGMA/HSA grafted polypropylene mesh fixed with the hydrogel adhesive compared to unmodified mesh. Toward the development of our bio-adhesive mesh system for abdominal hernia repair, we evaluated its surgical utility and in vivo performance in a rabbit model with retromuscular repair mimicking the totally extra-peritoneal surgical technique used in humans. We assessed mesh slippage/contraction using gross assessment and imaging, mesh fixation using tensile mechanical testing, and biocompatibility using histology. Compared to polypropylene mesh fixed with fibrin sealant, our bio-adhesive mesh system exhibited superior fixation without the gross bunching or distortion that was observed in the majority (80%) of the fibrin-fixed polypropylene mesh. This was evidenced by tissue integration within the bio-adhesive mesh pores after 42 days of implantation and adhesive strength sufficient to withstand the physiological forces expected in hernia repair applications. These results support the combined use of PGMA/HSA grafted polypropylene and bifunctional poloxamine hydrogel adhesive for medical implant applications. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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19 pages, 4402 KiB

Open AccessEditor’s ChoiceArticle

New Methacrylated Biopolymer-Based Hydrogels as Localized Drug Delivery Systems in Skin Cancer Therapy

by Andreea Luca, Isabella Nacu, Sabina Tanasache, Cătălina Anişoara Peptu, Maria Butnaru and Liliana Verestiuc

Gels 2023, 9(5), 371; https://doi.org/10.3390/gels9050371 - 1 May 2023

Cited by 3 | Viewed by 2029

Abstract

The aim of the present work was to obtain drug-loaded hydrogels based on combinations of dextran, chitosan/gelatin/xanthan, and poly (acrylamide) as a sustained and controlled release vehicle of Doxorubicin, a drug used in skin cancer therapy that is associated with severe side effects. Hydrogels for use as 3D hydrophilic networks with good manipulation characteristics were produced using methacrylated biopolymer derivatives and the methacrylate group’s polymerization with synthetic monomers in the presence of a photo-initiator, under UV light stimulation (365 nm). Transformed infrared spectroscopy analysis (FT-IR) confirmed the hydrogels’ network structure (natural–synthetic composition and photocrosslinking), while scanning electron microscopy (SEM) analysis confirmed the microporous morphology. The hydrogels are swellable in simulated biological fluids and the material’s morphology regulates the swelling properties: the maximum swelling degree was obtained for dextran–chitosan-based hydrogels because of their higher porosity and pore distribution. The hydrogels are bioadhesive on a biological simulating membrane, and values for the force of detachment and work of adhesion are recommended for applications on skin tissue. The Doxorubicin was loaded into the hydrogels and the drug was released by diffusion for all the resulting hydrogels, with small contributions from the hydrogel networks’ relaxation. Doxorubicin-loaded hydrogels are efficient on keratinocytes tumor cells, the sustained released drug interrupting the cells’ division and inducing cell apoptosis; we recommend the obtained materials for the topical treatment of cutaneous squamous cell carcinoma. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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10 pages, 3302 KiB

Open AccessCommunication

Xylan–Porphyrin Hydrogels as Light-Triggered Gram-Positive Antibacterial Agents

by Abdechakour Elkihel, Charlotte Vernisse, Tan-Sothéa Ouk, Romain Lucas-Roper, Vincent Chaleix and Vincent Sol

Gels 2023, 9(2), 124; https://doi.org/10.3390/gels9020124 - 2 Feb 2023

Cited by 2 | Viewed by 1339

Abstract

In the present work, we report on the synthesis of light-triggered antibacterial hydrogels, based on xylan chains covalently bound to meso-tetra(4-carboxyphenyl)porphyrin (TCPP). Not only does TCPP act as a photosensitizer efficient against Gram-positive bacteria, but it also serves as a cross-linking gelator, enabling the simple and easy building of xylan conjugate hydrogels. The hydrogels were characterized by infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), along with swelling and rheological tests. The antimicrobial activity of the hydrogels was tested under visible light irradiation against two Gram-positive bacterial strains, Staphylococcus aureus and Bacillus cereus. The preliminary results showed an interesting activity on these bacteria, indicating that these hydrogels could be of great potential in the treatment of skin bacterial infections with this species by photodynamic antimicrobial chemotherapy (PACT). Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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20 pages, 5675 KiB

Open AccessEditor’s ChoiceArticle

Hemostatic Cryogels Based on Oxidized Pullulan/Dopamine with Potential Use as Wound Dressings

by Raluca Ioana Baron, Ioana A. Duceac, Simona Morariu, Andra-Cristina Bostănaru-Iliescu and Sergiu Coseri

Gels 2022, 8(11), 726; https://doi.org/10.3390/gels8110726 - 9 Nov 2022

Cited by 17 | Viewed by 2729

Abstract

The impetus for research into hydrogels based on selectively oxidized polysaccharides has been stimulated by the diversity of potential biomedical applications. Towards the development of a hemostatic wound dressing in this study, we creatively combined the (hemi)acetal and Schiff base bonds to prepare a series of multifunctional cryogels based on dialdehyde pullulan and dopamine. The designed structures were verified by NMR and FTIR spectroscopy. Network parameters and dynamic sorption studies were correlated with environmental scanning microscopy results, thus confirming the successful integration of the two components and the opportunities for finely tuning the structure–properties balance. The viscoelastic parameters (storage and loss moduli, complex and apparent viscosities, zero shear viscosity, yield stress) and the structural recovery capacity after applying a large deformation were determined and discussed. The mechanical stability and hemostatic activity suggest that the optimal combination of selectively oxidized pullulan and dopamine can be a promising toolkit for wound management. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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22 pages, 4129 KiB

Open AccessArticle

Designing Deferoxamine-Loaded Flaxseed Gum and Carrageenan-Based Controlled Release Biocomposite Hydrogel Films for Wound Healing

by Tayyaba Sadiq, Syed Haroon Khalid, Ikram Ullah Khan, Hira Mahmood and Sajid Asghar

Gels 2022, 8(10), 652; https://doi.org/10.3390/gels8100652 - 14 Oct 2022

Cited by 2 | Viewed by 2003

Abstract

In this study, biocomposite hydrogel films made from flaxseed gum (FSG)/kappa carrageenan (CGN) were fabricated, using potassium chloride as a crosslinker and glycerol as a plasticizer. The composite films were loaded with deferoxamine (DFX), an iron chelator that promotes neovascularization and angiogenesis for the healing of wounds. The properties of the biocomposite hydrogel films, including swelling, solubility, water vapor transmission rate, tensile strength, elongation at break, and Young’s modulus studies, were tested. The films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). In addition, drug release studies in PBS at pH 7.2 were investigated. In vivo analysis was performed by assessing the wound contraction in a full-thickness excisional wound rat model. Hematoxylin & eosin (H & E) and Masson’s trichome staining were performed to evaluate the effect of the films on wound healing progress. The visual and micro-morphological analysis revealed the homogenous structure of the films; however, the elongation at break property decreased within the crosslinked film but increased for the drug-loaded film. The FTIR analysis confirmed the crosslinking due to potassium chloride. A superior resistance towards thermal degradation was confirmed by TGA for the crosslinked and drug-loaded films. Drug release from the optimum film was sustained for up to 24 h. In vivo testing demonstrated 100% wound contraction for the drug-loaded film group compared to 72% for the pure drug solution group. In light of the obtained results, the higher potential of the optimized biocomposite hydrogel film for wound healing applications was corroborated. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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32 pages, 43303 KiB

Open AccessArticle

Ionogels Derived from Fluorinated Ionic Liquids to Enhance Aqueous Drug Solubility for Local Drug Administration

by Carolina Hermida-Merino, David Cabaleiro, Carlos Gracia-Fernández, Jesus Valcarcel, José Antonio Vázquez, Noelia Sanz, Martín Pérez-Rodríguez, Maria Arenas-Moreira, Dipanjan Banerjee, Alessandro Longo, Carmen Moya-Lopez, Luis Lugo, Patrice Bourson, Ana B. Pereiro, Georges Salloum-Abou-Jaoude, Iván Bravo, Manuel M. Piñeiro and Daniel Hermida-Merino

Gels 2022, 8(9), 594; https://doi.org/10.3390/gels8090594 - 16 Sep 2022

Viewed by 2547

Abstract

Gelatin is a popular biopolymer for biomedical applications due to its harmless impact with a negligible inflammatory response in the host organism. Gelatin interacts with soluble molecules in aqueous media as ionic counterparts such as ionic liquids (ILs) to be used as cosolvents to generate the so-called Ionogels. The perfluorinated IL (FIL), 1-ethyl-3-methylpyridinium perfluorobutanesulfonate, has been selected as co-hydrosolvent for fish gelatin due to its low cytotoxicity and hydrophobicity aprotic polar structure to improve the drug aqueous solubility. A series of FIL/water emulsions with different FIL content and their corresponding shark gelatin/FIL Ionogel has been designed to enhance the drug solubility whilst retaining the mechanical structure and their nanostructure was probed by simultaneous SAXS/WAXS, FTIR and Raman spectroscopy, DSC and rheological experiments. Likewise, the FIL assisted the solubility of the antitumoural Doxorubicin whilst retaining the performing mechanical properties of the drug delivery system network for the drug storage as well as the local administration by a syringe. In addition, the different controlled release mechanisms of two different antitumoral such as Doxorubicin and Mithramycin from two different Ionogels formulations were compared to previous gelatin hydrogels which proved the key structure correlation required to attain specific therapeutic dosages. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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Review

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55 pages, 22856 KiB

Open AccessReview

Short Peptide-Based Smart Thixotropic Hydrogels

by Bapan Pramanik

Gels 2022, 8(9), 569; https://doi.org/10.3390/gels8090569 - 7 Sep 2022

Cited by 24 | Viewed by 3630

Abstract

Thixotropy is a fascinating feature present in many gel systems that has garnered a lot of attention in the medical field in recent decades. When shear stress is applied, the gel transforms into sol and immediately returns to its original state when resting. The thixotropic nature of the hydrogel has inspired scientists to entrap and release enzymes, therapeutics, and other substances inside the human body, where the gel acts as a drug reservoir and can sustainably release therapeutics. Furthermore, thixotropic hydrogels have been widely used in various therapeutic applications, including drug delivery, cornea regeneration and osteogenesis, to name a few. Because of their inherent biocompatibility and structural diversity, peptides are at the forefront of cutting-edge research in this context. This review will discuss the rational design and self-assembly of peptide-based thixotropic hydrogels with some representative examples, followed by their biomedical applications. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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13 pages, 2176 KiB

Open AccessReview

Ultrasound-Induced Drug Release from Stimuli-Responsive Hydrogels

by Tyus J. Yeingst, Julien H. Arrizabalaga and Daniel J. Hayes

Gels 2022, 8(9), 554; https://doi.org/10.3390/gels8090554 - 1 Sep 2022

Cited by 16 | Viewed by 3527

Abstract

Stimuli-responsive hydrogel drug delivery systems are designed to release a payload when prompted by an external stimulus. These platforms have become prominent in the field of drug delivery due to their ability to provide spatial and temporal control for drug release. Among the different external triggers that have been used, ultrasound possesses several advantages: it is non-invasive, has deep tissue penetration, and can safely transmit acoustic energy to a localized area. This review summarizes the current state of understanding about ultrasound-responsive hydrogels used for drug delivery. The mechanisms of inducing payload release and activation using ultrasound are examined, along with the latest innovative formulations and hydrogel design strategies. We also report on the most recent applications leveraging ultrasound activation for both cancer treatment and tissue engineering. Finally, the future perspectives offered by ultrasound-sensitive hydrogels are discussed. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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26 pages, 66037 KiB

Open AccessEditor’s ChoiceReview

Peptide-Based Low Molecular Weight Photosensitive Supramolecular Gelators

by Bapan Pramanik and Sahnawaz Ahmed

Gels 2022, 8(9), 533; https://doi.org/10.3390/gels8090533 - 25 Aug 2022

Cited by 15 | Viewed by 4578

Abstract

Over the last couple of decades, stimuli-responsive supramolecular gels comprising synthetic short peptides as building blocks have been explored for various biological and material applications. Though a wide range of stimuli has been tested depending on the structure of the peptides, light as a stimulus has attracted extensive attention due to its non-invasive, non-contaminant, and remotely controllable nature, precise spatial and temporal resolution, and wavelength tunability. The integration of molecular photo-switch and low-molecular-weight synthetic peptides may thus provide access to supramolecular self-assembled systems, notably supramolecular gels, which may be used to create dynamic, light-responsive “smart” materials with a variety of structures and functions. This short review summarizes the recent advancement in the area of light-sensitive peptide gelation. At first, a glimpse of commonly used molecular photo-switches is given, followed by a detailed description of their incorporation into peptide sequences to design light-responsive peptide gels and the mechanism of their action. Finally, the challenges and future perspectives for developing next-generation photo-responsive gels and materials are outlined. Full article

(This article belongs to the Special Issue Smart Hydrogels: From Rational Design to Applications)

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