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Advances in Functional Gel
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Advances in Functional Gel

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

Deadline for manuscript submissions: closed (30 November 2023) | Viewed by 22749

Special Issue Editors

Dr. Maria Rosaria Plutino

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Guest Editor
Institute for the Study of Nanostructured Materials, ISMN–CNR, Palermo, c/o Department ChiBioFarAm, University of Messina, 98166 Messina, Italy
Interests: materials chemistry; green chemistry; nanotechnology; environmental remediation; advanced materials; functional coating; colloidal nanoparticles; smart and hi-tech textiles; (waste)water treatment; multifunctional hybrid materials and nanocomposites; sensing technologies; bio-based blended polymers; circular economy
Special Issues, Collections and Topics in MDPI journals
Dr. Silvia Sfameni

E-Mail Website
Guest Editor
Institute for the Study of Nanostructured Materials, ISMN—CNR, Palermo, c/o Department of ChiBioFarAm, University of Messina, 98166 Messina, Italy
Interests: material chemistry; nanotechnology; sol–gel chemistry; polymer science; Hi-tech textiles; functional coatings; sustainability; stimuli-responsive polymers
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In the last few years, due to the increasing demands of modern society for sustainability, environmental protection and pollution prevention, there has been a growing global need for more efficient, eco-friendly and long-life materials.

In this framework, it appears to be quite necessary to encompass a range of strategies that can help in the transition towards a circular economy, by supporting:

  • a reduction in primary raw material consumption, fossil-based reagents and waste production;
  • the development of multifunctional products that can help in saving money and reducing pollution, by decreasing the number of products in our everyday life;
  • the maintenance of the final product performances over time, by improving their resistance to external agents and to consumption by end users, thus extending the product life cycle.

Using this reasoning, recent research studies in materials chemistry are moving towards the development of innovative and smart (multi)functional gel-based materials, featuring a wide range of interesting properties for applications in biomedical, sensing, textiles, catalysis, building, cultural heritage, blue-growth, automotive and environmental industrial sectors.

Additionally, nanotechnology has been shown to be a determinant in the rational design of these novel functional nanostructured gel formulations, leading to advanced nano-hybrid or nanocomposite gels, also useful as coatings for surface properties’ implementation, such as anti-vegetative or antibacterial, hydrophobic, anti-stain, fire-retardant, controlled drug release, molecule detection, protection and mechanical resistance.

In this regard, gel technologies are receiving considerable attention for the design and development of functional hybrid organic and inorganic systems, based on hosting (blended) polymeric matrices and opportune functional nanofillers, thanks to the advantages, such as low process temperature, no cytotoxicity, high final product homogeneity, hazardous solvent absence, high versatility and stably binding to functional molecules or surfaces.

Furthermore, green and eco-friendly gel-based synthetic protocols can be established in combination with natural-derived polymers and bio-based or secondary raw materials, thus resulting in new eco-friendly products, able to be recycled and re-used.

Dr. Maria Rosaria Plutino
Dr. Silvia Sfameni
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

  • smart gel systems
  • nanohybrid gels
  • nanocomposite gels
  • innovative advanced gels
  • bio-based gel materials
  • sol–gel technique
  • functional gel coatings

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Published Papers (16 papers)

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15 pages, 1397 KiB  
Article
From Hemp Waste to Bioactive Nanofiber Composites: Deep Eutectic Solvents and Electrospinning in Upcycling Endeavors
by Cláudia Mouro, Ana P. Gomes and Isabel C. Gouveia
Gels 2024, 10(1), 1; https://doi.org/10.3390/gels10010001 - 19 Dec 2023
Cited by 1 | Viewed by 1428
Abstract
Natural fibers have attracted increasing interest as an alternative to produce environmentally friendly and sustainable materials. Particularly, hemp fibers have been widely used in various industrial applications due to their extremely unique properties. However, hemp can generate a large amount of agro-waste, and [...] Read more.
Natural fibers have attracted increasing interest as an alternative to produce environmentally friendly and sustainable materials. Particularly, hemp fibers have been widely used in various industrial applications due to their extremely unique properties. However, hemp can generate a large amount of agro-waste, and it results in an attractive source of biopolymers for the development of low-cost materials as an alternative to the raw materials and conventional petroleum-based plastics. In addition, deep eutectic solvents (DESs), a new type of truly green solvents, have been shown to remove gums, lignin, and other non-cellulosic components from hemp fibers. Reusing these components dissolved into the DESs to fabricate new materials directly by electrospinning is a very attractive but still unexplored endeavor. Thus, this innovative research to venture new upcycling pathways is focused on the fabrication of composite nanofibers by electrospinning of a gel-based blend of Poly(vinyl alcohol) (PVA) and hemp agro-waste (HW) dissolved into choline chloride (ChCl):Glycerol (1:2) and ChCl:Urea (1:2) DES mixtures. The results obtained revealed that the produced nanofibers displayed uniform appearance with diameters ranging from 257.7 ± 65.6 nm to 380.8 ± 134.0 nm. In addition, the mechanical properties of the electrospun composite nanofibers produced from the gel-based blends of HW dissolved in DESs and PVA (HW-DESs_PVA) were found to be superior, resulting in an enhanced tensile strength and Young’s modulus. Furthermore, the incorporation of HW into the nanofibers was able to provide bioactive antioxidant and antibacterial properties. Overall, this study demonstrated a promising, more sustainable, and eco-friendly way to produce electrospun composite nanofibers using HW in a circular economy perspective. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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18 pages, 3905 KiB  
Article
Enhancing Soil Resilience: Bacterial Alginate Hydrogel vs. Algal Alginate in Mitigating Agricultural Challenges
by Flavia Dorochesi, Cesar Barrientos-Sanhueza, Álvaro Díaz-Barrera and Italo F. Cuneo
Gels 2023, 9(12), 988; https://doi.org/10.3390/gels9120988 - 17 Dec 2023
Viewed by 968
Abstract
Erosion and tillage changes negatively the soil physical structure, which directly impacts agricultural systems and consequently food security. To mitigate these adverse modifications, different polymeric materials from synthetic and natural sources, have been used as soil conditioners to improve the hydro-mechanical behavior of [...] Read more.
Erosion and tillage changes negatively the soil physical structure, which directly impacts agricultural systems and consequently food security. To mitigate these adverse modifications, different polymeric materials from synthetic and natural sources, have been used as soil conditioners to improve the hydro-mechanical behavior of affected soils. One of the most interesting and used natural polymers is the alginate hydrogel. Although commercially available alginate hydrogels are primarily sourced from algal, they can also be sourced from bacteria. The gelation capacity of these hydrogels is determined by their molecular properties, which, in turn, are influenced by the production conditions. Bacterial alginate hydrogel production offers the advantage of precise control over environmental conditions during cultivation and extraction, thereby maintaining and enhancing their molecular properties. This, in turn, results in higher molecular weight and improved gelation capacity. In this study, we compared the effects of bacterial alginate (BH) and algal alginate (AH) hydrogels over the mechanical, hydraulic, and structural behavior of coarse quartz sand as a model soil. Mechanically, it was observed that the treatment with the lowest concentration of bacteria alginate hydrogel (BH1) reached higher values of yield strength, Young’s modulus (E), shear modulus (G) and strain energy (U) than those treatments with algal alginate hydrogel (AH). Furthermore, the increase in the aggregate stability could be associated with the improvement of mechanical parameters. On the other hand, a greater water retention capacity was observed in the BH treatments, as well as a greater decrease in hydraulic conductivity with respect to the AH and control treatments. All these changes could be explained by the formation of bridge-like structures between the sand particles and the hydrogel, and this alteration may result in a shift in the mechanical and wettability characteristics of the treated soils. Finally, our findings emphasize the superior impact of bacterial alginate hydrogel on enhancing the mechanical and hydraulic properties of coarse quartz sand compared to traditional algal alginate. Besides, the use of bacterial alginate hydrogel could be useful to counteract erosion and water scarcity scenarios in agricultural systems. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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14 pages, 7020 KiB  
Article
Wound Microenvironment Self-Adjusting Hydrogels with Thermo-Sensitivity for Promoting Diabetic Wound Healing
by Jia Li, Jing Guo, Bo-Xiang Wang, Yue Zhang, Qiang Yao, De-Hong Cheng and Yan-Hua Lu
Gels 2023, 9(12), 987; https://doi.org/10.3390/gels9120987 - 17 Dec 2023
Viewed by 1117
Abstract
The hard-healing chronic wounds of diabetics are still one of the most intractable problems in clinical skin injury repair. Wound microenvironments directly affect wound healing speed, but conventional dressings exhibit limited efficacy in regulating the wound microenvironment and facilitating healing. To address this [...] Read more.
The hard-healing chronic wounds of diabetics are still one of the most intractable problems in clinical skin injury repair. Wound microenvironments directly affect wound healing speed, but conventional dressings exhibit limited efficacy in regulating the wound microenvironment and facilitating healing. To address this serious issue, we designed a thermo-sensitive drug-controlled hydrogel with wound self-adjusting effects, consisting of a sodium alginate (SA), Antheraeapernyi silk gland protein (ASGP) and poly(N-isopropylacrylamide) (PNIPAM) for a self-adjusting microenvironment, resulting in an intelligent releasing drug which promotes skin regeneration. PNIPAM has a benign temperature-sensitive effect. The contraction, drugs and water molecules expulsion of hydrogel were generated upon surpassing lower critical solution temperatures, which made the hydrogel system have smart drug release properties. The addition of ASGP further improves the biocompatibility and endows the thermo-sensitive drug-controlled hydrogel with adhesion. Additionally, in vitro assays demonstrate that the thermo-sensitive drug-controlled hydrogels have good biocompatibility, including the ability to promote the adhesion and proliferation of human skin fibroblast cells. This work proposes an approach for smart drug-controlled hydrogels with a thermo response to promote wound healing by self-adjusting the wound microenvironment. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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12 pages, 8872 KiB  
Article
Magnetic and Magnetostrictive Properties of Sol–Gel-Synthesized Chromium-Substituted Cobalt Ferrite
by Chandra Sekhar Beera, B. Dhanalakshmi, D. Nirmala Devi, D. Vijayalakshmi, Akanksha Mishra, S. Ramesh, B. Parvatheeswara Rao, P. Shyamala, Melita Menelaou, Nadyah Alanazi and Abdullah N. Alodhayb
Gels 2023, 9(11), 873; https://doi.org/10.3390/gels9110873 - 2 Nov 2023
Viewed by 1399
Abstract
Chromium (Cr)-doped cobalt ferrite nanoparticles were synthesized using a sol–gel autocombustion method, with the chemical formula CoCrxFe2xO4. The value of x ranged from 0.00 to 0.5 in 0.1 increments. X-ray diffraction analysis confirmed the development of highly [...] Read more.
Chromium (Cr)-doped cobalt ferrite nanoparticles were synthesized using a sol–gel autocombustion method, with the chemical formula CoCrxFe2xO4. The value of x ranged from 0.00 to 0.5 in 0.1 increments. X-ray diffraction analysis confirmed the development of highly crystalline cubic spinel structures for all samples, with an average crystallite size of approximately 40 to 45 nm determined using the Scherrer equation. Pellets were prepared using a traditional ceramic method. The magnetic and magnetostrictive properties of the samples were tested using strain gauge and VSM (vibrating sample magnetometer) techniques. The results of the magnetic and magnetostrictive tests showed that the chromium-substituted cobalt ferrites exhibited higher strain derivative magnitudes than pure cobalt ferrite. These findings indicated that the introduction of chromium into the cobalt ferrite structure led to changes in the material’s magnetic properties. These changes were attributed to anisotropic contributions, resulting from an increased presence of Co2+ ions at B-sites due to the chromium substitutions. In summary, this study concluded that introducing chromium into the cobalt ferrite structure caused alterations in the material’s magnetic properties, which were explained by changes in the cationic arrangement within the crystal lattice. This study successfully explained these alterations using magnetization and coercivity data and the probable cationic dispersion. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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13 pages, 2330 KiB  
Article
Forward Light Scattering of First to Third Generation Vitreous Body Replacement Hydrogels after Surgical Application Compared to Conventional Silicone Oils and Vitreous Body
by Maximilian Hammer, Jonathan Herth, Marcel Muuss, Sonja Schickhardt, Alexander Scheuerle, Ramin Khoramnia, Grzegorz Łabuz, Philipp Uhl and Gerd Uwe Auffarth
Gels 2023, 9(10), 837; https://doi.org/10.3390/gels9100837 - 21 Oct 2023
Cited by 2 | Viewed by 1304
Abstract
To treat certain vitreoretinal diseases, the vitreous body, a hydrogel composed of mostly collagen and hyaluronic acid, must be removed. After vitrectomy surgery, the vitreous cavity is filled with an endotamponade. Previously, pre-clinical hydrogel-based vitreous body substitutes either made from uncrosslinked monomers (1st [...] Read more.
To treat certain vitreoretinal diseases, the vitreous body, a hydrogel composed of mostly collagen and hyaluronic acid, must be removed. After vitrectomy surgery, the vitreous cavity is filled with an endotamponade. Previously, pre-clinical hydrogel-based vitreous body substitutes either made from uncrosslinked monomers (1st generation), preformed crosslinked polymers (2nd generation), or in situ gelating polymers (3rd generation) have been developed. Forward light scattering is a measure of Stray light induced by optical media, when increased, causing visual disturbance and glare. During pinhole surgery, the hydrogels are injected into the vitreous cavity through a small 23G-cannula. The aim of this study was to assess if and to what extent forward light scattering is induced by vitreous body replacement hydrogels and if Stray light differs between different generations of vitreous body hydrogel replacements due to the different gelation mechanisms and fragmentation during injection. A modified C-Quant setup was used to objectively determine forward light scattering. In this study, we found that the 1st and 3rd generation vitreous body replacements show very low stray light levels even after injection (2.8 +/− 0.4 deg2/sr and 0.2 +/− 0.2 deg2/sr, respectively) as gel fragmentation and generation of interfaces is circumvented. The 2nd generation preformed hydrogels showed a permanent increase in stray light after injection that will most likely lead to symptoms such as glare when used in patients (11.9 +/− 0.9 deg2/sr). Stray light of the 2nd generation hydrogels was 3- and 2-fold increased compared to juvenile and aged vitreous bodies, respectively. In conclusion, this significant downside in the forward light scattering of the 2nd generation hydrogels should be kept in mind when developing vitreous body replacement strategies, as any source of stray light should be minimized in patients with retinal comorbidities. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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16 pages, 2703 KiB  
Article
Evaluation of In Vitro Antioxidant, Anti-Obesity, and Anti-Diabetic Activities of Opuntia ficus Cladodes Gel and Its Application as a Preservative Coating for Shrimp during Refrigerated Storage
by Alaa S. Mohamed, Essam Mohamed Elsebaie, Wesam Mohammed Abdelrhman, Nabila Yahia Mahmoud Abdulmaguid, Rasha M. Bahnasy, Manal Salah Abbas Elgendy, Arwa Mohamed Mohamed Mahmoud Elashry, Marwa Fawzy El-Hassanin, Nora Hamdy Mouhamed El-Wakeil, Azhar Mostafa Mohamed Khalil and Hesham F. Amin
Gels 2023, 9(9), 716; https://doi.org/10.3390/gels9090716 - 4 Sep 2023
Cited by 1 | Viewed by 1110
Abstract
Opuntia ficus cladodes (OFC) are considered one of the wastes that result from opuntia cultivation, and their disposal by traditional methods results in many environmental problems. Therefore, this study was conducted with two aims. The first was the production of OFC gel, and [...] Read more.
Opuntia ficus cladodes (OFC) are considered one of the wastes that result from opuntia cultivation, and their disposal by traditional methods results in many environmental problems. Therefore, this study was conducted with two aims. The first was the production of OFC gel, and the evaluation of its in vitro antioxidant (by two methods, DPPH and ABTS), anti-obesity, and anti-diabetic activities. The second was an investigation of the effects of different concentrations of this gel (0, 50, and 100%) as an edible coating on the quality of shrimp during 8 days of refrigerated storage. The results showed that this gel was characterised by a high content of ash (10.42%), total carbohydrates (75.17%), and total phenols (19.79 mg GAE/g). OFC gel contained six types of sugars: arabinose, xylose, galactose, rhamnose, glucose, and uronic acid, and the most abundant was xylose (36.72%). It is also clear from the results that the OFC gel had high antioxidant properties, which were higher against DPPH than ABTS at the same concentration. OFC gel showed a high inhibition activity against lipase, α-glycosidase, and α-amylase enzymes, and their IC50 values were 1.43 mg/mL, 0.78 mg/mL, and 0.57 mg/mL, respectively. The results also stated that shrimp coated with OFC gel had lower pH, drip loss, TVB-N, and TBA values through the days of refrigerated storage. Moreover, the shrimp coated with 100% OFC gel were better than those coated with 50% OFC gel. In conclusion, OFC gel showed high potency as active antioxidant, for its enzyme anti-activities, and as an edible coating for shrimp. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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18 pages, 5209 KiB  
Article
Effect of the Preparation Method on the Properties of Eugenol-Doped Titanium Dioxide (TiO2) Sol-Gel Coating on Titanium (Ti) Substrates
by Julia Both, Anita-Petra Fülöp, Gabriella Stefania Szabó, Gabriel Katona, Alexandra Ciorîță and Liana Maria Mureșan
Gels 2023, 9(8), 668; https://doi.org/10.3390/gels9080668 - 18 Aug 2023
Cited by 2 | Viewed by 988
Abstract
The focus of this study was the preparation of sol–gel titanium dioxide (TiO2) coatings, by the dip-coating technique, on Ti6Al4V (TiGr5) and specific Ti implant substrates. In order to confer antibacterial properties to the layers, Eugenol was introduced in the coatings [...] Read more.
The focus of this study was the preparation of sol–gel titanium dioxide (TiO2) coatings, by the dip-coating technique, on Ti6Al4V (TiGr5) and specific Ti implant substrates. In order to confer antibacterial properties to the layers, Eugenol was introduced in the coatings in two separate ways: firstly by introducing the Eugenol in the sol (Eug–TiO2), and secondly by impregnating into the already deposed TiO2 coating (TiO2/Eug). Optimization of Eugenol concentration as well as long term were performed in orderboth short- and long-term Eugenol concentration was performed to investigate the prepared samples thoroughly. The samples were investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves (PDP). To investigate their resistance against Gram-negative Escherichia coli bacteria, microbiological analysis was performed on coatings prepared on glass substrates. Structural studies (FT-IR analysis, Raman spectroscopy) were performed to confirm Eugenol–TiO2 interactions. Coating thicknesses and adhesion were also determined for all samples. The results show that Eug–TiO2 presented with improved anticorrosive effects and significant antibacterial properties, compared to the other investigated samples. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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18 pages, 8485 KiB  
Article
Upcycling Wool Waste into Keratin Gel-Based Nanofibers Using Deep Eutectic Solvents
by Cláudia Mouro, Rodrigo Martins, Ana P. Gomes and Isabel C. Gouveia
Gels 2023, 9(8), 661; https://doi.org/10.3390/gels9080661 - 17 Aug 2023
Cited by 3 | Viewed by 1374
Abstract
Millions of tons of wool waste are produced yearly by textile industries, which may become a serious environmental hazard in the near future. Given this concern, it is crucial to explore strategies to reduce the amount of wool waste generated worldwide and adopt [...] Read more.
Millions of tons of wool waste are produced yearly by textile industries, which may become a serious environmental hazard in the near future. Given this concern, it is crucial to explore strategies to reduce the amount of wool waste generated worldwide and adopt more sustainable practices for dissolving and regenerating wool keratin (WK) from textile waste. Most traditional methods involve the use of expensive, toxic, harmful, and poorly biodegradable compounds. To overcome these limitations and facilitate the reuse of wool waste through a cascade valorization strategy, researchers have started testing the use of deep eutectic solvents (DES) as a more sustainable and eco-friendly alternative for WK dissolution and regeneration. In this study, the potential of two different DES mixtures, Choline chloride (ChCl): Urea and L-Cysteine (L-Cys): Lactic acid (LA), was explored for dissolving wool waste. Subsequently, the gels obtained based on DES-WK were blended with polyvinyl alcohol (PVA) in different ratios to produce nanofibers using the electrospinning technique. The PVA/L-Cys: LA DES-WK proved to be the most effective DES mixture for fabricating WK gel-based nanofibers. Furthermore, their antioxidant and antimicrobial abilities were evaluated, thus confirming their bioactivity. The results obtained revealed that this approach to valorizing textile waste offers a unique avenue for the development of sustainable functional materials with potential applications in various biomedical and industrial fields. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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12 pages, 3383 KiB  
Article
Non-Electroneutrality Generated by Bacteriorhodopsin-Incorporated Membranes Enhances the Conductivity of a Gelatin Memory Device
by U-Ting Chiu, Bo-Fan Lee, Ling-Ning Ko, Chii-Shen Yang and Ling Chao
Gels 2023, 9(8), 635; https://doi.org/10.3390/gels9080635 - 7 Aug 2023
Viewed by 907
Abstract
We have previously demonstrated the potential of gelatin films as a memory device, offering a novel approach for writing, reading, and erasing through the manipulation of gelatin structure and bound water content. Here, we discovered that incorporating a bacteriorhodopsin (BR)–lipid membrane into the [...] Read more.
We have previously demonstrated the potential of gelatin films as a memory device, offering a novel approach for writing, reading, and erasing through the manipulation of gelatin structure and bound water content. Here, we discovered that incorporating a bacteriorhodopsin (BR)–lipid membrane into the gelatin devices can further increase the electron conductivity of the polypeptide-bound water network and the ON/OFF ratio of the device by two folds. Our photocurrent measurements show that the BR incorporated in the membrane sandwiched in a gelatin device can generate a net proton flow from the counter side to the deposited side of the membrane. This leads to the establishment of non-electroneutrality on the gelatin films adjacent to the BR-incorporated membrane. Our Raman spectroscopy results show that BR proton pumping in the ON state gelatin device increases the bound water presence and promotes polypeptide unwinding compared to devices without BR. These findings suggest that the non-electroneutrality induced by BR proton pumping can increase the extent of polypeptide unwinding within the gelatin matrix, consequently trapping more bound water within the gelatin-bound water network. The resulting rise in hydrogen bonds could expand electron transfer routes, thereby enhancing the electron conductivity of the memory device in the ON state. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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25 pages, 15623 KiB  
Article
Thermal Evaluation of Silica-Based Insulated Magnet Wires from the Sol–Gel Process
by Giovana Pereira dos Santos Lima, Sonia Ait-Amar, Gabriel Velu, Philippe Frezel, Abdelhamid Boudiba, Soumaya Lafqir, Arnaud Nicolay, Pierre-yves Herze and Mireille Poelman
Gels 2023, 9(8), 619; https://doi.org/10.3390/gels9080619 - 31 Jul 2023
Viewed by 914
Abstract
The conventional enameling process used in the fabrication of magnet wires requires harmful processes and products. The target of the industry in the actual context of electrification is to increase the electrical machines’ efficiency. Indeed, the electrical insulation systems (EIS) of an electrical [...] Read more.
The conventional enameling process used in the fabrication of magnet wires requires harmful processes and products. The target of the industry in the actual context of electrification is to increase the electrical machines’ efficiency. Indeed, the electrical insulation systems (EIS) of an electrical machine undergo various environmental constraints that can shorten their lifespans. Consequently, aspects of the insulation need to be improved, such as its thermal resistance. One of the challenges is to implement sustainable technology without losing performance. This work consists of the thermal performance evaluation of new magnet wires insulated by three types of composites of silica-based solution from the Sol–gel process and amorphous polyamide-imide (PAI). These composite coats are overcoated by an extruded thermoplastic resin with and without fillers. Different types of insulation are tested and compared to determine the better configuration. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) analysis, scanning electron microscopy (SEM) analysis, curing characteristics by tangent delta curve, and thermal-aging tests at three temperatures were carried out on the different EIS systems. Dielectric measurements were made between thermal-aging cycles. Their basic mechanical, electrical, and thermal characteristics are promising: the cut-through temperature is situated above 430 °C, their breakdown voltage values are between 5 kV and 9 kV (grade 3), and a good adhesion (overcoming more than 140 turns on a peel test). The thermal-aging results have been consistent with the TGA analysis results. The thermal index following the IEC standards was estimated for the selected EIS, which would have the main basic characteristics of a magnet wire of 200 class; moreover, it would be a greener enameled wire compared to the conventional one. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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14 pages, 3147 KiB  
Article
Proniosomal Gel-Loaded Phosphodiesterase Inhibitors (Sildenafil, Vardenafil, and Tadalafil): Prospects for Topical Penile Therapy of Tadalafil for Treatment of Erectile Dysfunction
by Soad A. Mohamed, Remon Roshdy Rofaeil, Hesham Salem, Mahmoud Elrehany, Yahya I. Asiri, Adel Al Fatease and Hamdy Abdelkader
Gels 2023, 9(8), 597; https://doi.org/10.3390/gels9080597 - 25 Jul 2023
Cited by 1 | Viewed by 1613
Abstract
Oral phosphodiesterase inhibitors have emerged as a game changer for the treatment of erectile dysfunction (ED) since attaining FDA approval for its first member, sildenafil, in 1998. Topical penile therapy could be a viable replacement for oral medication that would transform the treatment [...] Read more.
Oral phosphodiesterase inhibitors have emerged as a game changer for the treatment of erectile dysfunction (ED) since attaining FDA approval for its first member, sildenafil, in 1998. Topical penile therapy could be a viable replacement for oral medication that would transform the treatment of ED for many decades to come. This innovative idea could offer a safer topical alternative with less vision and cardiovascular side effects than the oral route. This work aims at developing proniosomal gels for three selected members (sildenafil, vardenafil, and tadalafil) and investigating the proniosomal gels on a rodent model. Niosomes derived from the parent proniosomal gels were characterized for entrapment efficiency (EE%), size, polydispersity index (PDI), zeta potential, and morphology. Proniosomal gels were evaluated for skin permeation, in vivo mating behaviors, and biochemical assays of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) post penile topical administrations. The optimized proniosomes loaded with tadalafil (F1-T) were compared with oral tablets (Cialis®). Proniosomal gels demonstrated significant enhancement of skin penetration by up to 5.5-fold, compared to control topical suspension. Tadalafil-loaded proniosomes showed superior skin permeability over sildenafil- and vardenafil-loaded proniosomes. In addition, significant improvement was noticed regarding intromission number, intromission ratio, NO, and cGMP for the proniosomal gel F1-T, compared to the untreated control. No statistically significant (p > 0.05) differences in sexual performance or biochemical parameters (NO and cGMP levels) were recorded among orally and topically (tadalafil proniosomal gel) administered groups. These findings support tadalafil topical penile therapy as a promising alternative to the oral route. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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15 pages, 8239 KiB  
Article
3D Printing, Histological, and Radiological Analysis of Nanosilicate-Polysaccharide Composite Hydrogel as a Tissue-Equivalent Material for Complex Biological Bone Phantom
by Petar Valchanov, Nikolay Dukov, Stoyan Pavlov, Andreas Kontny and Tsanka Dikova
Gels 2023, 9(7), 547; https://doi.org/10.3390/gels9070547 - 5 Jul 2023
Viewed by 1173
Abstract
Nanosilicate-polysaccharide composite hydrogels are a well-studied class of materials in regenerative medicine that combine good 3D printability, staining, and biological properties, making them an excellent candidate material for complex bone scaffolds. The aim of this study was to develop a hydrogel suitable for [...] Read more.
Nanosilicate-polysaccharide composite hydrogels are a well-studied class of materials in regenerative medicine that combine good 3D printability, staining, and biological properties, making them an excellent candidate material for complex bone scaffolds. The aim of this study was to develop a hydrogel suitable for 3D printing that has biological and radiological properties similar to those of the natural bone and to develop protocols for their histological and radiological analysis. We synthesized a hydrogel based on alginate, methylcellulose, and laponite, then 3D printed it into a series of complex bioscaffolds. The scaffolds were scanned with CT and CBCT scanners and exported as DICOM datasets, then cut into histological slides and stained using standard histological protocols. From the DICOM datasets, the average value of the voxels in Hounsfield Units (HU) was calculated and compared with natural trabecular bone. In the histological sections, we tested the effect of standard histological stains on the hydrogel matrix in the context of future cytological and histological analysis. The results confirmed that an alginate/methylcellulose/laponite-based composite hydrogel can be used for 3D printing of complex high fidelity three-dimensional scaffolds. This opens an avenue for the development of dynamic biological physical phantoms for bone tissue engineering and the development of new CT-based imaging algorithms for the needs of radiology and radiation therapy. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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12 pages, 2870 KiB  
Article
Regenerated Fibers from Rennet-Treated Casein Micelles during Acidification
by Ronald Gebhardt and Novin Darvishsefat
Gels 2023, 9(7), 538; https://doi.org/10.3390/gels9070538 - 3 Jul 2023
Cited by 1 | Viewed by 1213
Abstract
Micellar casein fibers of defined size and internal structure can be produced by the extrusion of cold-renneted casein micelles into a warm, calcium-rich coagulation bath. Calcium phosphate contacts within the casein matrix are important for fiber stability and production but become less important [...] Read more.
Micellar casein fibers of defined size and internal structure can be produced by the extrusion of cold-renneted casein micelles into a warm, calcium-rich coagulation bath. Calcium phosphate contacts within the casein matrix are important for fiber stability and production but become less important under acidic pH conditions. We demonstrate this with swelling experiments in media with pH < 2, which we adjust with citric acid of different molarities. In contrast to the simple swelling of dried casein fibers in water, a two-phase process takes place in citric acid similar to swelling in 1 N HCl. However, instead of a second deswelling step, we observe in citric acid that the fiber swells further. The observation is explained by a pH-dependent transition from a rennet casein gel to an acidified rennet gel. This can be simulated with a kinetic model that couples two second-order rate equations via a time-varying ratio. The final swelling values decrease with increasing proton concentration via a scaling relation, which is also confirmed by swelling in other acids (HCl or acetic acid) in this pH range. We attribute this to a decrease in the molecular weights of the aggregated casein structures within the strands of the gel network. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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16 pages, 2717 KiB  
Article
Effects of Steam Sterilization on the Properties of Stimuli-Responsive Polymer-Based Hydrogels
by Inês Ferreira, Ana Camila Marques, Paulo Cardoso Costa and Maria Helena Amaral
Gels 2023, 9(5), 385; https://doi.org/10.3390/gels9050385 - 6 May 2023
Cited by 3 | Viewed by 2154
Abstract
Hydrogels based on stimuli-responsive polymers can change their characteristics in response to small variations in environmental conditions, such as temperature, pH, and ionic strength, among others. In the case of some routes of administration, such as ophthalmic and parenteral, the formulations must meet [...] Read more.
Hydrogels based on stimuli-responsive polymers can change their characteristics in response to small variations in environmental conditions, such as temperature, pH, and ionic strength, among others. In the case of some routes of administration, such as ophthalmic and parenteral, the formulations must meet specific requirements, namely sterility. Therefore, it is essential to study the effect of the sterilization method on the integrity of smart gel systems. Thus, this work aimed to study the effect of steam sterilization (121 °C, 15 min) on the properties of hydrogels based on the following stimuli-responsive polymers: Carbopol® 940, Pluronic® F-127, and sodium alginate. The properties of the prepared hydrogels—pH, texture, rheological behavior, and sol-gel phase transition—were evaluated to compare and identify the differences between sterilized and non-sterilized hydrogels. The influence of steam sterilization on physicochemical stability was also investigated by Fourier-transform infrared spectroscopy and differential scanning calorimetry. The results of this study showed that the Carbopol® 940 hydrogel was the one that suffered fewer changes in the studied properties after sterilization. By contrast, sterilization was found to cause slight changes in the Pluronic® F-127 hydrogel regarding gelation temperature/time, as well as a considerable decrease in the viscosity of the sodium alginate hydrogel. There were no considerable differences in the chemical and physical characteristics of the hydrogels after steam sterilization. It is possible to conclude that steam sterilization is suitable for Carbopol® 940 hydrogels. Contrarily, this technique does not seem adequate for the sterilization of alginate or Pluronic® F-127 hydrogels, as it could considerably alter their properties. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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Review

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25 pages, 2249 KiB  
Review
Cellulose-Based Metallogels—Part 3: Multifunctional Materials
by Aleksandra Mikhailidi, Elena Ungureanu, Dan Belosinschi, Bogdan-Marian Tofanica and Irina Volf
Gels 2023, 9(11), 878; https://doi.org/10.3390/gels9110878 - 6 Nov 2023
Cited by 1 | Viewed by 1661
Abstract
The incorporation of the metal phase into cellulose hydrogels, resulting in the formation of metallogels, greatly expands their application potential by introducing new functionalities and improving their performance in various fields. The unique antiviral, antibacterial, antifungal, and anticancer properties of metal and metal [...] Read more.
The incorporation of the metal phase into cellulose hydrogels, resulting in the formation of metallogels, greatly expands their application potential by introducing new functionalities and improving their performance in various fields. The unique antiviral, antibacterial, antifungal, and anticancer properties of metal and metal oxide nanoparticles (Ag, Au, Cu, CuxOy, ZnO, Al2O3, TiO2, etc.), coupled with the biocompatibility of cellulose, allow the development of composite hydrogels with multifunctional therapeutic potential. These materials can serve as efficient carriers for controlled drug delivery, targeting specific cells or pathogens, as well as for the design of artificial tissues or wound and burn dressings. Cellulose-based metallogels can be used in the food packaging industry to provide biodegradable and biocidal materials to extend the shelf life of the goods. Metal and bimetallic nanoparticles (Au, Cu, Ni, AuAg, and AuPt) can catalyze chemical reactions, enabling composite cellulose hydrogels to be used as efficient catalysts in organic synthesis. In addition, metal-loaded hydrogels (with ZnO, TiO2, Ag, and Fe3O4 nanoparticles) can exhibit enhanced adsorption capacities for pollutants, such as dyes, heavy metal ions, and pharmaceuticals, making them valuable materials for water purification and environmental remediation. Magnetic properties imparted to metallogels by iron oxides (Fe2O3 and Fe3O4) simplify the wastewater treatment process, making it more cost-effective and environmentally friendly. The conductivity of metallogels due to Ag, TiO2, ZnO, and Al2O3 is useful for the design of various sensors. The integration of metal nanoparticles also allows the development of responsive materials, where changes in metal properties can be exploited for stimuli-responsive applications, such as controlled release systems. Overall, the introduction of metal phases augments the functionality of cellulose hydrogels, expanding their versatility for diverse applications across a broad spectrum of industries not envisaged during the initial research stages. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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22 pages, 2129 KiB  
Review
Stimuli-Responsive Hydrogels for Protein Delivery
by Rafaela Malta, Ana Camila Marques, Paulo Cardoso da Costa and Maria Helena Amaral
Gels 2023, 9(10), 802; https://doi.org/10.3390/gels9100802 - 6 Oct 2023
Cited by 2 | Viewed by 1661
Abstract
Proteins and peptides are potential therapeutic agents, but their physiochemical properties make their use as drug substances challenging. Hydrogels are hydrophilic polymeric networks that can swell and retain high amounts of water or biological fluids without being dissolved. Due to their biocompatibility, their [...] Read more.
Proteins and peptides are potential therapeutic agents, but their physiochemical properties make their use as drug substances challenging. Hydrogels are hydrophilic polymeric networks that can swell and retain high amounts of water or biological fluids without being dissolved. Due to their biocompatibility, their porous structure, which enables the transport of various peptides and proteins, and their protective effect against degradation, hydrogels have gained prominence as ideal carriers for these molecules’ delivery. Particularly, stimuli-responsive hydrogels exhibit physicochemical transitions in response to subtle modifications in the surrounding environment, leading to the controlled release of entrapped proteins or peptides. This review is focused on the application of these hydrogels in protein and peptide delivery, including a brief overview of therapeutic proteins and types of stimuli-responsive polymers. Full article
(This article belongs to the Special Issue Advances in Functional Gel)
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