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Recent Advances in Crosslinked Gels
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Special Issue "Recent Advances in Crosslinked Gels"

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

Deadline for manuscript submissions: 10 August 2023 | Viewed by 6276

Special Issue Editors

Dr. Melike Firlak

E-Mail Website
Guest Editor
Department of Chemistry, Faculty of Science, Gebze Technical University, Gebze 41400, Turkey
Interests: hydrogels; stimuli-responsive polymers; polypyrroles; conducting polymers; applications of hydrogels; polymeric fluorescence sensors; controlled release
Dr. John G. Hardy

E-Mail Website
Guest Editor
1. Department of Chemistry, Faraday Building, Lancaster University, Lancaster LA1 4YB, Lancashire, UK
2. Materials Science Institute, Faraday Building, Lancaster University, Lancaster LA1 4YB, Lancashire, UK
Interests: polymer synthesis; supramolecular materials; biomaterials; stimuli-responsive materials; drug delivery; tissue engineering; sustainability
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The concept of gelation was first introduced by W.H. Carothers to describe systems in which a sample spanning three-dimensional (3D) networks of polymers/particles immobilizes the solvent in which they are dispersed/dissolved. The 3D network of polymers/particles is connected via covalent and/or non-covalent bonds, and it is important to note that the solvent content of such materials can be >90%. Gels have a variety of applications based on their properties, and those that respond to internal and/or external stimuli such as temperature, pH, solvent composition, ionic composition, magnetic field, electric field and light, etc. are described as “stimuli-responsive gels” or “smart gels”; this property of gels has attracted the attention of researchers working in different fields to generate gels for applications including but not limited to adsorption, recovery, drug delivery, tissue engineering, sensors, petroleum industry, etc.

This Special Issue serves as a focal point for high-quality research papers as well as review articles addressing crosslinked polymeric gels, their preparation, characterization, and various applications in the fields of chemistry, engineering, and biotechnology.

Dr. Melike Firlak
Dr. John G. Hardy
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 1800 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

  • Polymeric gels
  • Crosslinked gels
  • Supramolecular gels
  • Synthesis of polymers
  • Characterization of gels
  • Smart gels
  • Stimuli-responsive gels
  • Applications
  • Drug delivery
  • Sensors
  • Tissue engineering
  • Adsorption

Published Papers (6 papers)

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Research

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Article
Formation of Alginate/Chitosan Interpenetrated Networks Revealed by EPR Spectroscopy
by
Jean-Patrick Joly
,
Ludmila Aricov
,
George-Alin Balan
,
Elena Irina Popescu
,
Sorin Mocanu
,
Anca Ruxandra Leonties
,
Iulia Matei
,
Sylvain R. A. Marque
and
Gabriela Ionita
Gels 2023, 9(3), 231; https://doi.org/10.3390/gels9030231 - 16 Mar 2023
Viewed by 230
Abstract
This study analyzes the physico-chemical properties of interpenetrated polymer networks (IPNs) and semi-IPN resulting from cross-linking chitosan with glutaraldehyde and alginate with Ca2+ cations, as a function of the order in which the cross-linking agents are added to the polymer mixture. Three [...] Read more.
This study analyzes the physico-chemical properties of interpenetrated polymer networks (IPNs) and semi-IPN resulting from cross-linking chitosan with glutaraldehyde and alginate with Ca2+ cations, as a function of the order in which the cross-linking agents are added to the polymer mixture. Three physico-chemical methods were used to assess the differences between systems: rheology, IR spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. While rheology and IR spectroscopy are commonly used to characterize gel materials, EPR spectroscopy is rarely used, but has the advantage of providing local information about the dynamics of a system. The rheological parameters, which describe the global behavior of the samples, show that semi-IPN systems have a weaker gel behavior and the order of introducing the cross-linker in the polymer systems plays a role. The IR spectra of samples resulting by adding only Ca2+ or Ca2+ as the first cross-linker are similar to that of the alginate gel, while the spectra of samples in which glutaraldehyde is firstly added resemble the chitosan gel spectrum. Using spin-labeled alginate and spin-labeled chitosan, we monitored the changes occurring in the dynamic of the spin labels due to the formation of IPN and semi-IPN. The results show that the order of adding the cross-linking agents influences the dynamic of the IPN network, and that the formation of the alginate network determines the characteristics of the entire IPN system. The EPR data were correlated with the rheological parameters and IR spectra of the analyzed samples. Full article
(This article belongs to the Special Issue Recent Advances in Crosslinked Gels)
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Article
Thermal Behavior of Water in Sephadex® G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry
by
Noriko Onoda-Yamamuro
,
Hiroaki Minato
,
Eiji Nakayama
and
Norio Murase
Gels 2023, 9(2), 126; https://doi.org/10.3390/gels9020126 - 02 Feb 2023
Viewed by 395
Abstract
Water in a crosslinked dextran gel, Sephadex® G25, is known to remain partially unfrozen during cooling and undergoes ice crystallization during rewarming. However, the mechanism of ice crystallization during rewarming is still unclear. To elucidate the frozen state of water in the [...] Read more.
Water in a crosslinked dextran gel, Sephadex® G25, is known to remain partially unfrozen during cooling and undergoes ice crystallization during rewarming. However, the mechanism of ice crystallization during rewarming is still unclear. To elucidate the frozen state of water in the gel, thermal behavior at low temperatures was investigated by using adiabatic calorimetry. Heat capacities and enthalpy-relaxation rates of the gel-containing water of mass ratio h (=g H2O/g dry G25) = 1.00 were measured between 80 and 300 K during rewarming, where the gel was intermittently heated at the rate of 50–100 mK min−1. Although an exotherm indicating ice crystallization during rewarming was confirmed with the gel precooled rapidly, at 5 K min−1, it disappeared when precooled slowly, at 20 mK min−1. During rewarming after the rapid cooling, two glass transitions were observed at ca. 175 K and 240–242 K. A higher-temperature glass transition due to the water trapped by the polymer network was not so clear, as it was overlapped with an endotherm due to the melting of small ice crystals, which indicates that the ice crystals formed have a broad size-distribution and that water in the gel is vitrified when ice crystals of even the smallest size cannot be formed. Full article
(This article belongs to the Special Issue Recent Advances in Crosslinked Gels)
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Article
Formulation Development and In Vitro/In Vivo Characterization of Methotrexate-Loaded Nanoemulsion Gel Formulations for Enhanced Topical Delivery
by
Muhammad Shahid Latif
,
Asif Nawaz
,
Mufarreh Asmari
,
Jalal Uddin
,
Hidayat Ullah
and
Saeed Ahmad
Gels 2023, 9(1), 3; https://doi.org/10.3390/gels9010003 - 22 Dec 2022
Viewed by 899
Abstract
Methotrexate-loaded oil-in-water nanoemulsion formulations were prepared using the high shear homogenization technique. A drug excipient study (ATR-FTIR) was carried out to investigate the compatibility between the drug, the polymers, and its admixtures. The thermal stability of the nanoemulsion formulations was evaluated by subjecting [...] Read more.
Methotrexate-loaded oil-in-water nanoemulsion formulations were prepared using the high shear homogenization technique. A drug excipient study (ATR-FTIR) was carried out to investigate the compatibility between the drug, the polymers, and its admixtures. The thermal stability of the nanoemulsion formulations was evaluated by subjecting them to a heating and cooling cycle. The prepared nanoemulsion formulations (FNE1 to FNE6) were evaluated for particle size, PDI value, and entrapment efficiency (EE). They were analyzed for morphological information using transmission electron microscopy. The drug (methotrexate)-loaded nanoemulsion formulations (FNE2, FNE4, and FNE6) were then converted into nanoemulsion gel formulations by adding 1% chitosan (polymer) as a gelling agent. The nanoemulsion gel formulations (FNEG2, FNEG4, and FNEG6) were investigated for physicochemical parameters, viscosity, spreadability, extrudability, drug content, and skin irritation. Various penetration enhancers (olive oil, clove, and almond oil) were employed to examine the potency of the prepared nanoemulsion gel formulations. In vitro drug release, ex vivo permeation, skin drug retention, and stability tests were carried out for evaluation of the prepared nanoemulsion gel formulations (FNEG2, FNEG4, and FNEG6). The data obtained from the in vitro study were subjected to the kinetic model, and the Korsemeyer–Peppas model was best fitted to the data. The nanoemulsion gel formulation FNEG6 showed the maximum controlled drug release and followed an anomalous, non-Fickian release mechanism. The use of almond oil in the preparation of the nanoemulsion gel formulation FNEG6 helped the penetration of the drug across stratum corneum and the restructuring of the properties of skin and resulted in a higher penetration and retention of methotrexate in a deeper layer of the skin. The current study concluded that the methotrexate-loaded nanoemulsion gel formulation FNEG6 showed the best optimum release, permeation, and retention results as compared to the available oral tablets’ formulations, followed by a low serum concentration and the maximum drug retention, which is beneficial in treating skin infections and reducing systemic toxicity. Full article
(This article belongs to the Special Issue Recent Advances in Crosslinked Gels)
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Article
Thermo-Sensitive mPEG-PA-PLL Hydrogel for Drug Release of Calcitonin
by
Yu-En Cheng
,
I-En Wu
,
Yi-Chen Chen
and
I-Ming Chu
Gels 2022, 8(5), 282; https://doi.org/10.3390/gels8050282 - 02 May 2022
Cited by 2 | Viewed by 1616
Abstract
The oral route is the most popular way of drug administration because of good patient compliance and ease of use. However, the oral delivery of peptides and proteins is difficult, mainly due to poor oral bioavailability. In past decades, researchers have developed several [...] Read more.
The oral route is the most popular way of drug administration because of good patient compliance and ease of use. However, the oral delivery of peptides and proteins is difficult, mainly due to poor oral bioavailability. In past decades, researchers have developed several strategies to improve oral bioavailability by avoiding losing activity in the gastrointestinal (GI) tract and enhancing the intestinal permeability of these drugs. Methoxy poly(ethylene glycol)-poly(l-alanine) (mPEG-PA) is a thermo-sensitive hydrogel exhibiting a sol-to-gel phase transition property. This characteristic is appropriate for encapsulating peptide or protein drugs. To enhance the adhesion ability to intestinal mucus, a thermo-sensitive polymer, mPEG-PA, modified with charged amino acid lysine was developed. This positively charged material would help to bind the negatively charged mucin in mucus. The synthesis was conducted by individually synthesizing mPEG-PA and poly(l-lysine) (PLL) of different lengths via ring-opening polymerization. Then, mPEG-PA and PLL were combined using an NHS ester reaction to synthesize the triblock copolymer (mPEG-PA-PLL). Biocompatibility and the release of calcitonin from the synthesized hydrogel particles under different pH were examined. The initial data showed that the newly design material had a promising potential for the oral delivery of peptide drugs. Full article
(This article belongs to the Special Issue Recent Advances in Crosslinked Gels)
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Article
Do Polymeric Nanoparticles Really Enhance the Bioavailability of Oral Drugs? A Quantitative Answer Using Meta-Analysis
by
Rania M. Hathout
Gels 2022, 8(2), 119; https://doi.org/10.3390/gels8020119 - 14 Feb 2022
Cited by 1 | Viewed by 936
Abstract
The oral route remains one of the most popular and important routes of administration for drugs—one that warrants the development of advanced drug delivery systems, such as polymeric nanoparticles capable of enhancing the absorption and bioavailability of the used drugs. In this work, [...] Read more.
The oral route remains one of the most popular and important routes of administration for drugs—one that warrants the development of advanced drug delivery systems, such as polymeric nanoparticles capable of enhancing the absorption and bioavailability of the used drugs. In this work, a systematic review of published works on several databases, followed by a meta-analysis, were utilized in order to navigate the published studies and access literature-based evidence about the capability of polymeric nanoparticulate systems to augment the absorption and bioavailability of orally administered drugs. The pharmacokinetic parameter of the area under the curve (AUC) was utilized as the “effect” of this meta-analytical study. The meta-analysis demonstrated a significant increase in AUC compared to conventional formulations. Furthermore, comparing the synthetic polymeric nanoparticles, versus their naturally-based administered counterparts, as subgroups of the meta-analysis, revealed no significant differences. Full article
(This article belongs to the Special Issue Recent Advances in Crosslinked Gels)
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Review

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Review
A Comprehensive Review of Cross-Linked Gels as Vehicles for Drug Delivery to Treat Central Nervous System Disorders
by
Leshasha T. Mashabela
,
Mahlako M. Maboa
,
Ntombi F. Miya
,
Taiwo O. Ajayi
,
Rumbidzai S. Chasara
,
Marnus Milne
,
Shoeshoe Mokhele
,
Patrick H. Demana
,
Bwalya A. Witika
,
Xavier Siwe-Noundou
and
Madan S. Poka
Gels 2022, 8(9), 563; https://doi.org/10.3390/gels8090563 - 06 Sep 2022
Cited by 2 | Viewed by 1355
Abstract
Gels are attractive candidates for drug delivery because they are easily producible while offering sustained and/or controlled drug release through various mechanisms by releasing the therapeutic agent at the site of action or absorption. Gels can be classified based on various characteristics including [...] Read more.
Gels are attractive candidates for drug delivery because they are easily producible while offering sustained and/or controlled drug release through various mechanisms by releasing the therapeutic agent at the site of action or absorption. Gels can be classified based on various characteristics including the nature of solvents used during preparation and the method of cross-linking. The development of novel gel systems for local or systemic drug delivery in a sustained, controlled, and targetable manner has been at the epitome of recent advances in drug delivery systems. Cross-linked gels can be modified by altering their polymer composition and content for pharmaceutical and biomedical applications. These modifications have resulted in the development of stimuli-responsive and functionalized dosage forms that offer many advantages for effective dosing of drugs for Central Nervous System (CNS) conditions. In this review, the literature concerning recent advances in cross-linked gels for drug delivery to the CNS are explored. Injectable and non-injectable formulations intended for the treatment of diseases of the CNS together with the impact of recent advances in cross-linked gels on studies involving CNS drug delivery are discussed. Full article
(This article belongs to the Special Issue Recent Advances in Crosslinked Gels)
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Displaying articles 1-6

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Title: Recent Advances in Cross-linked Gels as Drug Carriers for Drug Delivery to the Central Nervous System: A Systemic Review

Abstract: Gels are semisolid, homogeneous formulations comprising a dispersion of substance in a suitable hydrophobic or hydrophilic three-dimensional polymer network system. Gels have a wide range of applications, including in food, cosmetics, biotechnology, and medicines. Gels are attractive candidates as drug delivery systems because they are easily to producible while offering sustained and/or controlled drug release through various routes as they intimately place the therapeutic agent at the site of action or absorption. Development of novel gel systems for local or systemic drug delivery in a sustained, controlled, and targetable manner has been at the epitome of recent advances in drug delivery systems. This preceded research on the design of gel-based systems that respond to specific biological or external stimuli like pH, temperature, ionic charges, enzymes, antigens, light, magnetic field, ultrasound, and electric current. Hydrogels are three-dimensional, crosslinked networks of water-soluble polymers that undergo physical transformation in the presence of water while maintaining the structural integrity. Hydrogels are widely exploited for their self-regulated drug-delivery mechanisms. Hydrogels have made an immense contribution in the development of the different drug delivery systems (DDS) over the last decade. They have been appraised as “smart gel systems” and continue to be researched extensively for various applications. In this review, the literature concerning hydrogel systems, particularly recent advances in crosslinked gels for targeted drug delivery to the central nervous system are explored. The different types of advanced formulations reported will be discussed, presenting the most recent patents according to the clinical applications.

 

2. Title: Thermal studies of water confined in cross-linked dextran gel Sephadex G-25 by adiabatic calorimetry

 Abstract: Thermal behaviors of water confined in crosslinked dextran gel Sephadex G-25 were investigated by adiabatic calorimetry.  Heat capacities and enthalpy relaxation phenomena of the sample of water to anhydrate mass ratio /h/ = 1.00 was measured between 80 and 300 K. After rapid cooling (3-5 K min^-1 ), gradual heat evolution was observed in the wide temperature range of 170-242 K and the melting of ice began at 242 K. Immediately afterthe beginning of melting, crystallization due to glassy water which uncrystallized during cooling occurred at 248 K.  The melting of ice covered a wide temperature range of 242-272 K.  After super slow cooling (10-20 mK min^-1 ), only a melting of ice was observed at 242-272 K.  Enthalpy relaxation behavior peculiar to glass transitionwas observed at 140-200 K. Melting Enthalpy of 4.43 kJ (H2O 1 mol)^-1 corresponds to 73 % of bulk water, suggesting that 27% water in /h/ = 1.00 sample doesn’t crystalize due to strong interaction with sephadex. The enthalpy of crystallization due to glassy water, about 4 % of melting enthalpy.  The enthalpy of gradual heat evolution depended on the cooling speed. Detailed discussion will be presented.

 

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