Non-Woven Infection Prevention Fabrics Coated with Biobased Cranberry Extracts Inactivate Enveloped Viruses Such as SARS-CoV-2 and Multidrug-Resistant Bacteria.

The Coronavirus Disease (COVID-19) pandemic is demanding the rapid action of the authorities and scientific community in order to find new antimicrobial solutions that could inactivate the pathogen SARS-CoV-2 that causes this disease. Gram-positive bacteria contribute to severe pneumonia associated with COVID-19, and their resistance to antibiotics is exponentially increasing. In this regard, non-woven fabrics are currently used for the fabrication of infection prevention clothing such as face masks, caps, scrubs, shirts, trousers, disposable gowns, overalls, hoods, aprons and shoe covers as protective tools against viral and bacterial infections. However, these non-woven fabrics are made of materials that do not exhibit intrinsic antimicrobial activity. Thus, we have here developed non-woven fabrics with antimicrobial coatings of cranberry extracts capable of inactivating enveloped viruses such as SARS-CoV-2 and the bacteriophage phi 6 (about 99% of viral inactivation in 1 min of viral contact), and two multidrug-resistant bacteria: the methicillin-resistant Staphylococcus aureus and the methicillin-resistant Staphylococcus epidermidis. The morphology, thermal and mechanical properties of the produced filters were characterized by optical and electron microscopy, differential scanning calorimetry, thermogravimetry and dynamic mechanical thermal analysis. The non-toxicity of these advanced technologies was ensured using a Caenorhabditis elegans in vivo model. These results open up a new prevention path using natural and biodegradable compounds for the fabrication of infection prevention clothing in the current COVID-19 pandemic and microbial resistant era.

Special Issue: "Polymer-Based Biomaterials and Tissue Engineering".

Polymers in the form of films, fibers, nano- and microspheres, composites, and porous supports are promising biomaterials for a wide range of advanced biomedical applications: wound healing, controlling drug delivery, anti-cancer therapy, biosensors, stem cell therapy, and tissue engineering [...].

Biocompatible Alginate Film Crosslinked with Ca2+ and Zn2+ Possesses Antibacterial, Antiviral, and Anticancer Activities.

Alginate is a highly promising biopolymer due to its non-toxic and biodegradable properties. Alginate hydrogels are often fabricated by cross-linking sodium alginate with calcium cations and can be engineered with highly desirable enhanced physical and biological properties for biomedical applications. This study reports on the anticancer, antiviral, antibacterial, in vitro, and in vivo toxicity, water absorption, and compound release properties of an alginate hydrogel crosslinked with calcium and different amounts of zinc cations. The results showed that the calcium alginate hydrogel film crosslinked with the highest amount of zinc showed similar water sorption properties to those of calcium alginate and released a suitable amount of zinc to provide anticancer activity against melanoma and colon cancer cells and has antibacterial properties against methicillin-resistant Staphylococcus epidermidis and antiviral activity against enveloped and non-enveloped viruses. This film is non-toxic in both in vitro in keratinocyte HaCaT cells and in vivo in the Caenorhabditis elegans model, which renders it especially promising for biomedical applications.

Engineered Highly Porous Polyvinyl Alcohol Hydrogels with Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Graphene Nanosheets for Musculoskeletal Tissue Engineering: Morphology, Water Sorption, Thermal, Mechanical, Electrical Properties, and Biocompatibility.

Electroactive composite materials are very promising for musculoskeletal tissue engineering because they can be applied in combination with electrostimulation. In this context, novel graphene-based poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/polyvinyl alcohol (PHBV/PVA) semi-interpenetrated networks (semi-IPN) hydrogels were engineered with low amounts of graphene (G) nanosheets dispersed within the polymer matrix to endow them with electroactive properties. The nanohybrid hydrogels, obtained by applying a hybrid solvent casting-freeze-drying method, show an interconnected porous structure and a high water-absorption capacity (swelling degree > 1200%). The thermal characterization indicates that the structure presents microphase separation, with PHBV microdomains located between the PVA network. The PHBV chains located in the microdomains are able to crystallize; even more after the addition of G nanosheets, which act as a nucleating agent. Thermogravimetric analysis indicates that the degradation profile of the semi-IPN is located between those of the neat components, with an improved thermal stability at high temperatures (>450 °C) after the addition of G nanosheets. The mechanical (complex modulus) and electrical properties (surface conductivity) significantly increase in the nanohybrid hydrogels with 0.2% of G nanosheets. Nevertheless, when the amount of G nanoparticles increases fourfold (0.8%), the mechanical properties diminish and the electrical conductivity does not increase proportionally, suggesting the presence of G aggregates. The biological assessment (C2C12 murine myoblasts) indicates a good biocompatibility and proliferative behavior. These results reveal a new conductive and biocompatible semi-IPN with remarkable values of electrical conductivity and ability to induce myoblast proliferation, indicating its great potential for musculoskeletal tissue engineering.

Active methods in electricity and magnetism courses: Influence of degree, academic level and gender on student performance.

The performance of first-year students in electromagnetism (E&M) courses of different engineering degrees at a Spanish public university was measured using the Brief Electricity and Magnetism Assessment (BEMA), a standard research-based instrument to assess students' understanding after attending introductory courses in electricity and magnetism. In all cases, Flipped classroom (FC) built on information and communications technology was used. The objective of this paper is to analyse if the gain in the BEMA pre and post-test results is influenced by several factors such as the degree, the students' academic grade, and gender. Moreover, as some studies have shown that the students' retention of the concepts was significantly stronger in active learning than in traditional approaches, a third BEMA test was performed by the students to analyse the long-term retention gain dependence on the same factors. Students from different engineering degree programs were asked to complete two BEMA tests during the course and a third one after a few months. ANOVA tests were used to analyse the existence of significant differences in gain between student degree programs, student academic level and student gender. Results have shown no differences in the BEMA performance by degree program, but significant differences were found by academic level and gender. Retention did not depend on the degree course but on the academic level. Mean gain value by academic level, and gender was obtained and concluded that the best students presented the best gain results and that gain depends on the students' gender: males outperformed females in the BEMA tests, although there were no significant differences in the course grades. It is thus necessary to understand these differences and to implement measures in daily teaching work to improve women's performance.

Scaffolds in the microbial resistant era: Fabrication, materials, properties and tissue engineering applications.

Due to microbial infections dramatically affect cell survival and increase the risk of implant failure, scaffolds produced with antimicrobial materials are now much more likely to be successful. Multidrug-resistant infections without suitable prevention strategies are increasing at an alarming rate. The ability of cells to organize, develop, differentiate, produce a functioning extracellular matrix (ECM) and create new functional tissue can all be controlled by careful control of the extracellular microenvironment. This review covers the present state of advanced strategies to develop scaffolds with antimicrobial properties for bone, oral tissue, skin, muscle, nerve, trachea, cardiac and other tissue engineering applications. The review focuses on the development of antimicrobial scaffolds against bacteria and fungi using a wide range of materials, including polymers, biopolymers, glass, ceramics and antimicrobials agents such as antibiotics, antiseptics, antimicrobial polymers, peptides, metals, carbon nanomaterials, combinatorial strategies, and includes discussions on the antimicrobial mechanisms involved in these antimicrobial approaches. The toxicological aspects of these advanced scaffolds are also analyzed to ensure future technological transfer to clinics. The main antimicrobial methods of characterizing scaffolds' antimicrobial and antibiofilm properties are described. The production methods of these porous supports, such as electrospinning, phase separation, gas foaming, the porogen method, polymerization in solution, fiber mesh coating, self-assembly, membrane lamination, freeze drying, 3D printing and bioprinting, among others, are also included in this article. These important advances in antimicrobial materials-based scaffolds for regenerative medicine offer many new promising avenues to the material design and tissue-engineering communities.

Pro-Myogenic Environment Promoted by the Synergistic Effect of Conductive Polymer Nanocomposites Combined with Extracellular Zinc Ions.

A new strategy based on the combination of electrically conductive polymer nanocomposites and extracellular Zn2+ ions as a myogenic factor was developed to assess its ability to synergically stimulate myogenic cell response. The conductive nanocomposite was prepared with a polymeric matrix and a small amount of graphene (G) nanosheets (0.7% wt/wt) as conductive filler to produce an electrically conductive surface. The nanocomposites' surface electrical conductivity presented values in the range of human skeletal muscle tissue. The biological evaluation of the cell environment created by the combination of the conductive surface and extracellular Zn2+ ions showed no cytotoxicity and good cell adhesion (murine C2C12 myoblasts). Amazingly, the combined strategy, cell-material interface with conductive properties and Zn bioactive ions, was found to have a pronounced synergistic effect on myoblast proliferation and the early stages of differentiation. The ratio of differentiated myoblasts cultured on the conductive nanocomposites with extracellular Zn2+ ions added in the differentiation medium (serum-deprived medium) was enhanced by more than 170% over that of non-conductive surfaces (only the polymeric matrix), and more than 120% over both conductive substrates (without extracellular Zn2+ ions) and non-conductive substrates with extracellular Zn2+. This synergistic effect was also found to increase myotube density, myotube area and diameter, and multinucleated myotube formation. MyoD-1 gene expression was also enhanced, indicating the positive effect in the early stages of myogenic differentiation. These results demonstrate the great potential of this combined strategy, which stands outs for its simplicity and robustness, for skeletal muscle tissue engineering applications.

Zinc Chloride: Time-Dependent Cytotoxicity, Proliferation and Promotion of Glycoprotein Synthesis and Antioxidant Gene Expression in Human Keratinocytes.

The use of ionic metals such as zinc (Zn2+) is providing promising results in regenerative medicine. In this study, human keratinocytes (HaCaT cells) were treated with different concentrations of zinc chloride (ZnCl2), ranging from 1 to 800 µg/mL, for 3, 12 and 24 h. The results showed a time-concentration dependence with three non-cytotoxic concentrations (10, 5 and 1 µg/mL) and a median effective concentration value of 13.5 µg/mL at a cell exposure to ZnCl2 of 24 h. However, the zinc treatment with 5 or 1 µg/mL had no effect on cell proliferation in HaCaT cells in relation to the control sample at 72 h. The effects of the Zn2+ treatment on the expression of several genes related to glycoprotein synthesis, oxidative stress, proliferation and differentiation were assessed at the two lowest non-cytotoxic concentrations after 24 h of treatment. Out of 13 analyzed genes (superoxide dismutase 1 (SOD1), catalase (CAT), matrix metallopeptidase 1 (MMP1), transforming growth factor beta 1 (TGFB1), glutathione peroxidase 1 (GPX1), fibronectin 1 (FN1), hyaluronan synthase 2 (HAS2), laminin subunit beta 1 (LAMB1), lumican (LUM), cadherin 1 (CDH1), collagen type IV alpha (COL4A1), fibrillin (FBN) and versican (VCAN)), Zn2+ was able to upregulate SOD1, CAT, TGFB1, GPX1, LUM, CDH1, FBN and VCAN, with relative expression levels of at least 1.9-fold with respect to controls. We found that ZnCl2 promoted glycoprotein synthesis and antioxidant gene expression, thus confirming its great potential in biomedicine.

Non-Markovian Methods in Glass Transition.

A model for the heterogeneity of local dynamics in polymer and other glass-forming materials is provided here. The fundamental characteristics of the glass transition phenomenology emerge when simulating a condensed matter open cluster that has a strong interaction with its heterogeneous environment. General glass transition features, such as non-exponential structural relaxations, the slowing down of relaxation times with temperature and specific off-equilibrium glassy dynamics can be reproduced by non-Markovian dynamics simulations with the minimum computer resources. Non-Markovian models are shown to be useful tools for obtaining insights into the complex dynamics involved in the glass transition phenomenon, including whether or not there is a need for a growing correlation length or the relationship between the non-exponentiality of structural relaxations and dynamic heterogeneity.

Novel Semi-Interpenetrated Polymer Networks of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/Poly (Vinyl Alcohol) with Incorporated Conductive Polypyrrole Nanoparticles.

This paper reports the preparation and characterization of semi-interpenetrating polymer networks (semi-IPN) of poly(3-hydroxybutirate-co-3-hydroxyvalerate), PHBV, and poly (vinyl alcohol), PVA, with conductive polypirrole (PPy) nanoparticles. Stable hybrid semi-IPN (PHBV/PVA 30/70 ratio) hydrogels were produced by solvent casting, dissolving each polymer in chloroform and 1-methyl-2-pyrrolidone respectively, and subsequent glutaraldehyde crosslinking of the PVA chains. The microstructure and physical properties of this novel polymeric system were analysed, including thermal behaviour and degradation, water sorption, wettability and electrical conductivity. The conductivity of these advanced networks rose significantly at higher PPy nanoparticles content. Fourier transform infrared spectroscopy (FTIR) and calorimetry characterization indicated good miscibility and compatibility between all the constituents, with no phase separation and strong interactions between phases. A single glass transition was observed between those of pure PHBV and PVA, although PVA was dominant in its contribution to the glass transition process. Incorporating PPy nanoparticles significantly reduced the hydrogel swelling, even at low concentrations, indicating molecular interactions between the PPy nanoparticles and the hydrogel matrix. The PHBV/PVA semi-IPN showed higher thermal stability than the neat polymers and PHBV/PVA blend, which also remained in the tertiary systems.

Bio-Nanocomposite Hydrogel Based on Zinc Alginate/Graphene Oxide: Morphology, Structural Conformation, Thermal Behavior/Degradation, and Dielectric Properties.

Bio-nanocomposite hydrogels based on sodium alginate (SA) as polymer matrix and graphene oxide (GO) nanosheets with zinc as crosslinking agent were synthesized with the aim of incorporating the intrinsic properties of their constituents (bioactivity and antimicrobial activity). Thus, stable and highly interconnected networks were obtained from GO nanosheets dispersed in SA matrices through interactions with low amounts of zinc. The GO nanosheets were successfully incorporated into the alginate matrix in the form of a complex nano-network involving different interactions: Bonds between alginate chains induced by Zn ions (egg box structure), interactions between GO nanosheets through Zn ions and hydrogen bonds between alginate chains, and GO nanosheets. The molecular interactions and morphology were confirmed by Fourier-transform infrared spectroscopy and transmission electron microscopy. The composite's structural organization showed enhanced thermal stability. The glass transition temperature shifted to a higher temperature due to the reduced mobility induced by additional crosslinking bonds after incorporating the GO nanosheets and Zn into the polymer matrix. Finally, the dielectric behavior revealed that charge carrier mobility was hampered by the compact structure of the nanonetwork, which reduced conductivity. The combined properties of these nanocomposite hydrogels make them attractive biomaterials in the field of regenerative medicine and wound care since both surface bioactivity and antibacterial behavior are two critical factors involved in the success of a biomaterial.

Zinc Maintains Embryonic Stem Cell Pluripotency and Multilineage Differentiation Potential via AKT Activation.

Embryonic stem cells (ESCs) possess remarkable abilities, as they can differentiate into all cell types (pluripotency) and be self-renewing, giving rise to two identical cells. These characteristics make ESCs a powerful research tool in fundamental embryogenesis as well as candidates for use in regenerative medicine. Significant efforts have been devoted to developing protocols to control ESC fate, including soluble and complex cocktails of growth factors and small molecules seeking to activate/inhibit key signaling pathways for the maintenance of pluripotency states or activate differentiation. Here we describe a novel method for the effective maintenance of mouse ESCs, avoiding the supplementation of complex inhibitory cocktails or cytokines, e.g., LIF. We show that the addition of zinc to ESC cultures leads to a stable pluripotent state that shares biochemical, transcriptional and karyotypic features with the classical LIF treatment. We demonstrate for the first time that ESCs maintained in long-term cultures with added zinc, are capable of sustaining a stable ESCs pluripotent phenotype, as well as differentiating efficiently upon external stimulation. We show that zinc promotes long-term ESC self-renewal (>30 days) via activation of ZIP7 and AKT signaling pathways. Furthermore, the combination of zinc with LIF results in a synergistic effect that enhances LIF effects, increases AKT and STAT3 activity, promotes the expression of pluripotency regulators and avoids the expression of differentiation markers.

Engineered microenvironments for synergistic VEGF - Integrin signalling during vascularization.

We have engineered polymer-based microenvironments that promote vasculogenesis both in vitro and in vivo through synergistic integrin-growth factor receptor signalling. Poly(ethyl acrylate) (PEA) triggers spontaneous organization of fibronectin (FN) into nanonetworks which provide availability of critical binding domains. Importantly, the growth factor binding (FNIII12-14) and integrin binding (FNIII9-10) regions are simultaneously available on FN fibrils assembled on PEA. This material platform promotes synergistic integrin/VEGF signalling which is highly effective for vascularization events in vitro with low concentrations of VEGF. VEGF specifically binds to FN fibrils on PEA compared to control polymers (poly(methyl acrylate), PMA) where FN remains in a globular conformation and integrin/GF binding domains are not simultaneously available. The vasculogenic response of human endothelial cells seeded on these synergistic interfaces (VEGF bound to FN assembled on PEA) was significantly improved compared to soluble administration of VEGF at higher doses. Early onset of VEGF signalling (PLCγ1 phosphorylation) and both integrin and VEGF signalling (ERK1/2 phosphorylation) were increased only when VEGF was bound to FN nanonetworks on PEA, while soluble VEGF did not influence early signalling. Experiments with mutant FN molecules with impaired integrin binding site (FN-RGE) confirmed the role of the integrin binding site of FN on the vasculogenic response via combined integrin/VEGF signalling. In vivo experiments using 3D scaffolds coated with FN and VEGF implanted in the murine fat pad demonstrated pro-vascularization signalling by enhanced formation of new tissue inside scaffold pores. PEA-driven organization of FN promotes efficient presentation of VEGF to promote vascularization in regenerative medicine applications.

Role of chemical crosslinking in material-driven assembly of fibronectin (nano)networks: 2D surfaces and 3D scaffolds.

Poly(ethyl acrylate) (PEA) induces the formation of biomimetic fibronectin (FN) (nano)networks upon simple adsorption from solutions, a process referred to as material-driven FN fibrillogenesis. The ability of PEA to organize FN has been demonstrated in 2D and 2.5D environments, but not as yet in 3D scaffolds, which incorporate three-dimensionality and chemical crosslinkers that may influence its fibrillogenic potential. In this paper we show for the first time that while three-dimensionality does not interfere with PEA-induced FN fibrillogenesis, crosslinking does, and we determined the maximum amount of crosslinker that can be added to PEA to maintain FN fibrillogenesis. For this, we synthesised 2D substrates with different amounts of crosslinker (1-10% of ethylene glycol dimethacrylate) and studied the role of crosslinking in FN organization using AFM. The glass transition temperature was seen to increase with crosslinking density and, accordingly, polymer segmental mobility was reduced. The organization of FN after adsorption (formation of FN fibrils) and the availability of the FN cell-binding domain were found to be dependent on crosslinking density. Surface mobility was identified as a key parameter for FN supramolecular organization. PEA networks with up to 2% crosslinker organize the FN in a similar way to non-crosslinked PEA. Scaffolds prepared with 2% crosslinker also had FN (nano)networks assembled on their walls, showing PEA's ability to induce FN fibrillogenesis in 3D environments as long as the amounts of crosslinker is low enough.

Controlled Assembly of Fibronectin Nanofibrils Triggered by Random Copolymer Chemistry.

Fibronectin fibrillogenesis is the physiological process by which cells elaborate a fibrous FN matrix. Poly(ethyl acrylate), PEA, has been described to induce a similar process upon simple adsorption of fibronectin (FN) from a protein solution-in the absence of cells-leading to the so-called material-driven fibronectin fibrillogenesis. Poly(methyl acrylate), PMA, is a polymer with very similar chemistry to PEA, on which FN is adsorbed, keeping the globular conformation of the protein in solution. We have used radical polymerization to synthesize copolymers with controlled EA/MA ratio, seeking to modulate the degree of FN fibrillogenesis. The physicochemical properties of the system were studied using dynamic-mechanical analysis, differential scanning calorimetry, and water contact angle. Both the degree of FN fibrillogenesis and the availability of the integrin binding region of FN directly depend on the percentage of EA in the copolymer, whereas the same total amount of FN was adsorbed regardless the EA/MA ratio. Cell morphology adhesion and differentiation of murine C2C12 were shown to depend on the degree of FN fibrillogenesis previously attained on the material surface. Myogenic differentiation was enhanced on the copolymers with higher EA content, i.e. more interconnected FN fibrils.