Special Issue "Processing, Characterization and Uses of Aerogels for Biomedical and Environmental Applications"

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

Deadline for manuscript submissions: 31 October 2020.

Special Issue Editors

Dr. Carlos A. García-González
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Guest Editor
Department of Pharmacology, Pharmacy and Pharmaceutical Technology, University of Santiago de Compostela, 15782 - Santiago de Compostela, Spain
Interests: aerogels; supercritical fluids; regenerative medicine; pharmaceutical technology; 3D-bioprinting; porous materials; scaffolds; biomedical applications
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Prof. Dr. Luísa Durães
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Guest Editor
University of Coimbra, Chemical Process Engineering and Forest Products Research Centre, Department of Chemical Engineering, 3030-790 - Coimbra, Portugal
Interests: aerogels; nanoparticles; soft-solution synthesis; thermal insulation materials; environmental remediation; adsorption; heavy metals; VOC
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Prof. Dr. Tatiana Budtova
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Guest Editor
Center for Materials Forming, MINES ParisTech
Interests: polymer solution; gels and aerogels; complex fluids; bioplastics; composites with natural fibers
Prof. Dr. Falk Liebner
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Guest Editor
1. Institute for Chemistry of Renewable Resources, Department of Chemistry, University of Natural Resources and Life Sciences Vienna, 3430 Tulln, Austria
2. Department of Chemistry, Aveiro Institute of Materials (CICECO), University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
Interests: biopolymer materialchemistry; hydrogels, aerogels and carbon aerogels; tailoring of biopolymer aerogels for technical and biomedical applications; supercritical carbon dioxide in biopolymer processing; chemistry of natural and artificial humic substances
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Prof. Dr. Urszula Stachewicz
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Guest Editor
AGH Univeristy of Science and Technology, Krakow, Poland
Interests: electrospinning, electrospray, fibers, scaffolds, membranes, porous mats, 3D tomography, FIB-SEM, microscopy, wetting, nanomechanics, surface properties, biomimetics,
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Aerogels are unique nanostructured porous materials with special properties adapted to fit certain advanced applications. Namely, the biomedical and environmental fields are two emerging market opportunities for these materials.
Aerogel-based materials can be used in biomedical applications such as drug carriers, synthetic bone grafts for regenerative medicine and advanced wound dressings. For environmental applications, heat and sound insulators, as well as absorbents, adsorbents, sensors and catalysts for wastewater treatment and for air and water pollutants detection are among the uses being explored for aerogels.
Technological developments in terms of novel designs, processes, modelling tools, characterization techniques and uses for aerogels should be aligned to boost the progresses on the topic. This Special Issue aims at showing the most recent scientific-technological advances in aerogels on a wide range of fundamental topics and applied for biomedical and environmental uses.
This Special Issue is an initiative of the AERoGELS (CA18125 - Advanced Engineering and Research of aeroGels for Environment and Life Sciences) Action (https://cost-aerogels.eu) by COST (European Cooperation in Science and Technology) that aims to boost the development of aerogels for biomedical and environmental applications by setting up a multidisciplinary knowledge-based network from technological, scientific and market points of view.

Prof. Dr. Carlos A. García-González
Prof. Dr. Luísa Durães
Prof. Dr. Tatiana Budtova
Prof. Dr. Falk Liebner
Prof. Dr. Urszula Stachewicz
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 papers will be 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. Polymers 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

  • aerogels
  • modelling
  • nanostructured materials
  • bio-based aerogels
  • advanced materials
  • composites
  • process engineering
  • scale-up
  • supercritical drying
  • health risk assessment

Published Papers (7 papers)

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Research

Open AccessArticle
Preparation of Hybrid Alginate-Chitosan Aerogel as Potential Carriers for Pulmonary Drug Delivery
Polymers 2020, 12(10), 2223; https://doi.org/10.3390/polym12102223 - 27 Sep 2020
Abstract
This study aims to prepare hybrid chitosan-alginate aerogel microparticles without using additional ionic crosslinker as a possible pulmonary drug delivery system. The microparticles were prepared using the emulsion gelation method. The effect of the mixing order of the biopolymer within the emulsion and [...] Read more.
This study aims to prepare hybrid chitosan-alginate aerogel microparticles without using additional ionic crosslinker as a possible pulmonary drug delivery system. The microparticles were prepared using the emulsion gelation method. The effect of the mixing order of the biopolymer within the emulsion and the surfactant used on final particle properties were investigated. Physicochemical characterizations were performed to evaluate particle size, density, morphology, surface area, surface charge, and the crystallinity of the preparation. The developed preparation was evaluated for its acute toxicity in adult male Sprague-Dawley rats. Measurements of zeta potential suggest that the surface charge depends mainly on the surfactant type while the order of biopolymer mixing has less impact on the surface charge. Chitosan amphiphilic properties changed the hydrophilic-lipophilic balance (HLB) of the emulsifying agents. The specific surface area of the prepared microparticles was in the range of (29.36–86.20) m2/g with a mesoporous pore size of (12.48–13.38) nm and pore volume of (0.09–0.29) cm3/g. The calculated aerodynamic diameter of the prepared particles was in the range of (0.17–2.29 µm). Toxicity studies showed that alginate-chitosan carrier developed herein caused mild lung inflammation with some renal and hepatic toxicities. Full article
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Open AccessArticle
Chitosan-Based Aerogel Particles as Highly Effective Local Hemostatic Agents. Production Process and In Vivo Evaluations
Polymers 2020, 12(9), 2055; https://doi.org/10.3390/polym12092055 - 10 Sep 2020
Abstract
Chitosan aerogels with potential applications as effective local hemostatic agents were prepared using supercritical carbon dioxide drying to preserve the chitosan network structure featuring high internal surfaces and porosities of up to 300 m²/g and 98%, respectively. For the first time, hemostatic efficacy [...] Read more.
Chitosan aerogels with potential applications as effective local hemostatic agents were prepared using supercritical carbon dioxide drying to preserve the chitosan network structure featuring high internal surfaces and porosities of up to 300 m²/g and 98%, respectively. For the first time, hemostatic efficacy of chitosan-based aerogel particles was studied in vivo on a model of damage of a large vessel in the deep wound. Pigs were used as test animals. It was shown that primary hemostasis was achieved, there were no signs of rebleeding and aerogel particles were tightly fixed to the walls of the wound canal. A dense clot was formed inside the wound (at the femoral artery), which indicates stable hemostasis. This study demonstrated that chitosan-based aerogel particles have a high sorption capacity and are highly effective as local hemostatic agents which can be used to stop massive bleeding. Full article
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Open AccessArticle
Experimental Investigation and CFD Modeling of Supercritical Adsorption Process
Polymers 2020, 12(9), 1957; https://doi.org/10.3390/polym12091957 - 29 Aug 2020
Abstract
The kinetics of the supercritical adsorption process was experimentally studied by the example of ”ibuprofen-silica aerogel” composition obtainment at various parameters: Pressure 120–200 bar and temperature 40–60 °C. Computational Fluid Dynamics (CFD) model of the supercritical adsorption process in a high-pressure apparatus based [...] Read more.
The kinetics of the supercritical adsorption process was experimentally studied by the example of ”ibuprofen-silica aerogel” composition obtainment at various parameters: Pressure 120–200 bar and temperature 40–60 °C. Computational Fluid Dynamics (CFD) model of the supercritical adsorption process in a high-pressure apparatus based on the provisions of continuum mechanics is proposed. Using supercritical adsorption process kinetics experimental data, the dependences of the effective diffusion coefficient of active substance in the aerogel, and the maximum amount of the adsorbed active substance into the aerogel on temperature and pressure are revealed. Adequacy of the proposed model is confirmed. The proposed mathematical model allows predicting the behavior of system (fields of velocity, temperature, pressure, composition, density, etc.) at each point of the studied medium. It makes possible to predict mass transport rate of the active substance inside the porous body depending on the geometry of the apparatus, structure of flow, temperature, and pressure. Full article
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Open AccessArticle
Ferrocene Introduced into 5-Methylresorcinol-Based Organic Aerogels
Polymers 2020, 12(7), 1582; https://doi.org/10.3390/polym12071582 - 16 Jul 2020
Abstract
The polycondensation sol–gel reaction of 5-methylresocinol and formaldehyde with additional compounds in reaction media is a relatively simple way to produce modified aerogels. In order to obtain aerogels with a large surface area and high porosity, the conditions for gel formation, the solvent [...] Read more.
The polycondensation sol–gel reaction of 5-methylresocinol and formaldehyde with additional compounds in reaction media is a relatively simple way to produce modified aerogels. In order to obtain aerogels with a large surface area and high porosity, the conditions for gel formation, the solvent exchange process before drying, and the supercritical drying process were optimized. A successful attempt was made to introduce ferrocene units into 5-methylresocinol-formaldehyde-based aerogels. The resulting aerogels are amorphous substrates, and no aggregated ferrocene units were found in their structures. All of the aerogel samples that were obtained are structurally similar despite differences in the original ferrocene units and their initial concentration. It was found that the inclusion limit of ferrocene structural blocks into an aerogel is ~6% wt. The structures of the inclusions in which all of the Fe atoms in the aerogel substrates were present in ferrocene/ferrocenium at an approximate ratio of 60/40 to 55/45 were confirmed by X-ray photoelectron spectroscopy and Mössbauer spectroscopy. Aerogels with ferrocene/ferrocenium inclusions are likely to exhibit reversible redox activity in reactions with gaseous reagents. Full article
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Open AccessArticle
Optimization of Polyamide Pulp-Reinforced Silica Aerogel Composites for Thermal Protection Systems
Polymers 2020, 12(6), 1278; https://doi.org/10.3390/polym12061278 - 03 Jun 2020
Abstract
The present work describes for the first time the preparation of silica-based aerogel composites containing tetraethoxysilane (TEOS) and vinyltrimethoxysilane (VTMS) reinforced with Kevlar® pulp. The developed system was extensively investigated, regarding its physical, morphological, thermal and mechanical features. The obtained bulk density [...] Read more.
The present work describes for the first time the preparation of silica-based aerogel composites containing tetraethoxysilane (TEOS) and vinyltrimethoxysilane (VTMS) reinforced with Kevlar® pulp. The developed system was extensively investigated, regarding its physical, morphological, thermal and mechanical features. The obtained bulk density values were satisfactory, down to 208 kg·m−3, and very good thermal properties were achieved—namely a thermal conductivity as low as 26 mW·m−1·K−1 (Hot Disk®) and thermal stability up to 550 °C. The introduction of VTMS offers a better dispersion of the polyamide fibers, as well as a higher hydrophobicity and thermal stability of the composites. The aerogels were also able to withstand five compression-decompression cycles without significant change of their size or microstructure. A design of experiment (DOE) was performed to assess the influence of different synthesis parameters, including silica co-precursors ratio, pulp amount and the solvent/Si molar ratio on the nanocomposite properties. The data obtained from the DOE allowed us to understand the significance of each parameter, offering reliable guidelines for the adjustment of the experimental procedure in order to achieve the optimum properties of the studied aerogel composites. Full article
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Open AccessArticle
Large, Rapid Swelling of High-cis Polydicyclopentadiene Aerogels Suitable for Solvent-Responsive Actuators
Polymers 2020, 12(5), 1033; https://doi.org/10.3390/polym12051033 - 02 May 2020
Cited by 1
Abstract
High-cis polydicyclopentadiene (PDCPD) aerogels were synthesized using ring opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) with a relatively air-stable ditungsten catalytic system, Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 (W2; [...] Read more.
High-cis polydicyclopentadiene (PDCPD) aerogels were synthesized using ring opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) with a relatively air-stable ditungsten catalytic system, Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 (W2; (W3W)6+, a′2e′4), and norbornadiene (NBD)as a co-initiator. These aerogels are compared in terms of chemical structure and material properties with literature PDCPD aerogels obtained using well-established Ru-based alkylidenes as catalysts. The use of NBD as a co-initiator enhances the degree of crosslinking versus the more frequently used phenylacetylene (PA), yielding materials with a controlled molecular structure that would persist solvent swelling. Indeed, those PDCPD aerogels absorb selected organic solvents (e.g., chloroform, tetrahydrofuran) and swell rapidly, in some cases up to 4 times their original volume within 10 min, thus showing their potential for applications in chemical sensors and solvent-responsive actuators. The advantage of aerogels versus xerogels or dense polymers for these applications is their open porosity, which provides rapid access of the solvent to their interior, thus decreasing the diffusion distance inside the polymer itself, which in turn accelerates the response to the solvents of interest. Full article
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Open AccessArticle
Jet Cutting Technique for the Production of Chitosan Aerogel Microparticles Loaded with Vancomycin
Polymers 2020, 12(2), 273; https://doi.org/10.3390/polym12020273 - 29 Jan 2020
Cited by 5
Abstract
Biopolymer-based aerogels can be obtained by supercritical drying of wet gels and endowed with outstanding properties for biomedical applications. Namely, polysaccharide-based aerogels in the form of microparticles are of special interest for wound treatment and can also be loaded with bioactive agents to [...] Read more.
Biopolymer-based aerogels can be obtained by supercritical drying of wet gels and endowed with outstanding properties for biomedical applications. Namely, polysaccharide-based aerogels in the form of microparticles are of special interest for wound treatment and can also be loaded with bioactive agents to improve the healing process. However, the production of the precursor gel may be limited by the viscosity of the polysaccharide initial solution. The jet cutting technique is regarded as a suitable processing technique to overcome this problem. In this work, the technological combination of jet cutting and supercritical drying of gels was assessed to produce chitosan aerogel microparticles loaded with vancomycin HCl (antimicrobial agent) for wound healing purposes. The resulting aerogel formulation was evaluated in terms of morphology, textural properties, drug loading, and release profile. Aerogels were also tested for wound application in terms of exudate sorption capacity, antimicrobial activity, hemocompatibility, and cytocompatibility. Overall, the microparticles had excellent textural properties, absorbed high amounts of exudate, and controlled the release of vancomycin HCl, providing sustained antimicrobial activity. Full article
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