Multiscale characterization of electrospun non-wovens for corneal regeneration: Impact of microstructure on mechanical, optical and biological properties.

The multiscale approach in designing substrates for regenerative medicine endows them with beneficial properties determining their performance in the body. Substrates for corneal regeneration should reveal the proper transparency, mechanical properties and microstructure to maintain the functionality of the regenerated tissue. In our study, series of non-wovens with different fibres orientation (random (R), aligned (A)), topography (shish-kebab (KK), core-shell (CS)) and thickness were fabricated via electrospinning. The samples were assessed for mechanical (static tensile test) and optical properties (spectroscopy UV-Vis). The research evaluated the impact of different microstructures on the viability and morphology of three cell lines (Hs 680, HaCaT and RAW 264.7). The results showed how the fibres arrangement influenced mechanical behaviour of the non-wovens. The randomly oriented fibres were more elongated (up to 50 mm) and had a lower maximum tensile force (up to 0.46 N). In turn, the aligned fibres were characterized by lower elongation (up to 19 mm) and higher force (up to 1.45 N). The conducted transparency tests showed the relation between thickness (of the non-woven and fibres) and morphology of the substrate and light transmission. To simulate the in vivo conditions, prior to the light transmission studies, samples were immersed in water. All the samples exhibited high transparency after immersion in water (>80%). The impact of various morphologies was observed in the in vitro studies. All the samples proved high cells viability. Moreover, the substrate morphology had a significant impact on the orientation and arrangement of the fibroblast cytoskeleton. The aligned fibres were oriented in exactly the same direction. The conducted research proved that, by altering the non-wovens microstructure, the properties can be adjusted so as to induce the desirable cellular reaction. This indicates the high potential of electrospun fibres in terms of modulating the corneal cell behaviour in response to the implanted substrate.

Oat straw pyrolysis with ammonium chloride doping: Analysis of evolved gases, kinetic triplet, and thermodynamic parameters.

The purpose of this work was to determine the effect of the addition of NH4Cl to oat straw on the evolved gases, kinetic triplet, and thermodynamic parameters of the pyrolysis process at 873 K. A complementary approach allowed to assess the effects of the pyrolysis of chlorine- and nitrogen-enriched biomass. The thermal analysis of biomass was performed for four heating rates (5, 10, 20, and 30 K/min). The doping of NH4Cl in the straw favoured i) carbonisation of the chars, ii) formation of C-N bonds, iii) reduction of evolved CH4 and CO2, and iv) an increase in the mean values of the effective activation energy and all thermodynamic parameters. A group of reactions that best fit the experimental data of the pyrolysis process was selected. It was necessary to use unspecified mechanisms to describe the reaction model, particularly for samples enriched with NH4Cl.

Correlation between porosity and physicochemical and biological properties of electrospinning PLA/PVA membranes for skin regeneration.

Electrospinning is an increasingly popular technique for obtaining scaffolds for skin regeneration. However, electrospun scaffolds may also have some disadvantages, as the densely packed fibers in the scaffold structure can limit the penetration of skin cells into the inner part of the material. Such a dense arrangement of fibers can cause the cells to treat the 3D material as 2D one, and thus cause them to accumulate only on the upper surface. In this study, bi-polymer scaffolds made of polylactide (PLA) and polyvinyl alcohol (PVA) electrospun in a sequential or a concurrent system were investigated in a different PLA:PVA ratio (2:1 and 1:1). The properties of six types of model materials were investigated and compared i.e.; the initial materials electrospun by the sequential (PLA/PVA, 2PLA/PVA) and the concurrent system (PLA||PVA) and the same materials with removed PVA fibers (PLA/rPVA, 2PLA/rPVA, PLA||rPVA). The fiber models were intended to increase the porosity and coherent structure parameters of the scaffolds. The applied treatment involving the removal of PVA nanofibers increased the size of interfibrous pores formed between the PLA fibers. Ultimately, the porosity of the PLA/PVA scaffolds increased from 78 % to 99 %, and the time of water absorption decreased from 516 to 2 s. The change in wettability was induced by a synergistic effect of decrease in roughness after washing out and the presence of residual PVA fibers. The chemical analysis carried out confirmed the presence of PVA residues on the PLA fibers (FTIR-ATR study). In vitro studies were performed on human keratinocytes (HaKaT) and macrophages (RAW264.7), for which penetration into the inner part of the PLAIIPVA scaffold was observed. The new proposed approach, which allows the removal of PVA fibers from the bicomponent material, allows to obtain a scaffold with increased porosity, and thus better permeability for cells and nutrients.

Functionalized Halloysite Nanotubes as Potential Drug Carriers.

The aim of the work was to examine the possibility of using modified halloysite nanotubes as a gentamicin carrier and to determine the usefulness of the modification in terms of the effect on the amount of the drug attached, its release time, but also on the biocidal properties of the carriers. In order to fully examine the halloysite in terms of the possibility of gentamicin incorporating, a number of modifications of the native halloysite were carried out prior to gentamicin intercalation with the use of sodium alkali, sulfuric and phosphoric acids, curcumin and the process of delamination of nanotubes (expanded halloysite) with ammonium persulfate in sulfuric acid. Gentamicin was added to unmodified and modified halloysite in an amount corresponding to the cation exchange capacity of pure halloysite from the Polish Dunino deposit, which was the reference sample for all modified carriers. The obtained materials were tested to determine the effect of surface modification and their interaction with the introduced antibiotic on the biological activity of the carrier, kinetics of drug release, as well as on the antibacterial activity against Escherichia coli Gram-negative bacteria (reference strain). For all materials, structural changes were examined using infrared spectroscopy (FTIR) and X-ray diffraction (XRD); thermal differential scanning calorimetry with thermogravimetric analysis (DSC/TG) was performed as well. The samples were also observed for morphological changes after modification and drug activation by transmission electron microscopy (TEM). The conducted tests clearly show that all samples of halloysite intercalated with gentamicin showed high antibacterial activity, with the highest antibacterial activity for the sample modified with sodium hydroxide and intercalated with the drug. It was found that the type of halloysite surface modification has a significant effect on the amount of gentamicin intercalated and then released into the surrounding environment but does not significantly affect its ability to further influence drug release over time. The highest amount of drug released among all intercalated samples was recorded for halloysite modified with ammonium persulfate (real loading efficiency above 11%), for which high antibacterial activity was found after surface modification, before drug intercalation. It is also worth noting that intrinsic antibacterial activity was found for non-drug-intercalated materials after surface functionalization with phosphoric acid (V) and ammonium persulfate in the presence of sulfuric acid (V).

NiO-Ba0.95Ca0.05Ce0.9Y0.1O3-δ as a Modified Anode Material Fabricated by the Tape Casting Method.

The development of new chemically resistant anodes for protonic ceramic fuel cells (PCFCs) is urgently required to avoid the costly deep hydrogen purification method. Ba0.95Ca0.05Ce0.9Y0.1O3-δ (5CBCY), which is more chemically resistant than BaCaCe0.9Y0.1O3-δ, was here tested as a component of a composite NiO-5CBCY anode material. A preparation slurry comprising 5CBCY, NiO, graphite, and an organic medium was tape cast, sintered and subjected to thermal treatment in 10 vol.% H2 in Ar at 700 °C. Differential thermal analysis, thermogravimetry, quadrupole mass spectrometry, X-ray diffraction analysis, scanning electron microscopy, the AC four-probe method and electrochemical impedance spectroscopy were used for the investigation. The electrical conductivity of the Ni-5CBCY in H2-Ar at 700 °C was 1.1 S/cm. In the same gas atmosphere but with an additional 5 vol.% CO2, it was slightly lower, at 0.8 S/cm. The Ni-5CBCY cermet exhibited repeatable electrical conductivity values during Ni-to-NiO oxidation cycles and NiO-to-Ni reduction in the 5CBCY matrix, making it sufficient for preliminary testing in PCFCs.

Rheological Properties of Soft Waste Granulates Produced in the Fabrication Process of Ceramic Tiles and the Possibility of Their Reuse.

The paper presents the results of research on the influence of the granulometric composition on the rheological properties of granulates from soft waste produced in the manufacturing of ceramic tiles using the Lamgea and Continua methods in terms of the possibility of their reuse. The composition of the granulates was modified by removing individual grain fractions in three measurement series. Comparatively, the measurement samples for the production granulates were prepared in the same way. Microscopic observations and granulometric analysis showed significant differences in the grain shape and grain size distribution of granulates. The soft waste granulates also showed much worse flow ability than the production granulates. It was shown that the removal of the smallest fractions significantly improved the rheological properties of soft waste granulates. This tendency was also observed in the case of measurements of changes in the bulk density. A Brookfield powder analyzer was used for rheological tests, and a flow analysis was performed using the numerical Jenike classification.

Modification of TiAlV Alloys with Hybrid Layers Containing Metallic Nanoparticles Obtained by the Sol-Gel Method: Surface and Structural Properties.

The aim of the work was to obtain hybrid coatings containing silver, copper, and zinc nanoparticles on the TiAlV medical alloy via a sol-gel process. The developed layers were designed to bring about a bactericidal and fungicidal effect, as well as for protection against surgical scratches during the implantation of implants used in veterinary medicine. In this work, the authors focused on evaluating the microstructure (SEM + EDS); the structure (XRD, FTIR); and the surface properties, such as wettability, free surface energy, and roughness of layers with various concentrations of metallic nanoparticles (2 and 5 mol %). Our results confirmed that the sol-gel method enables the easy manufacturing of hybrid layers endowed with different porosity values as well as various shapes and sizes of metallic nanoparticles. A higher concentration of nanoparticles was observed on the surface containing 5 mol % of metallic salts. The highest degree of homogeneity was obtained for the layers containing silver nanoparticles. In addition, the silver nanoparticles were round and had the smallest dimensions, even below 20 nm. The FTIR and XRD structural studies confirmed the presence of an organosilicon matrix containing all three types of the metallic particles. We conclude that the higher concentration of nanoparticles influenced the alloy surface parameters.

The Utilisation of Solid Fuels Derived from Waste Pistachio Shells in Direct Carbon Solid Oxide Fuel Cells.

The comprehensive results regarding the physicochemical properties of carbonaceous materials that are obtained from pistachio shells support their usage as solid fuels to supply direct carbon solid oxide fuel cells (DC-SOFCs). The influence of preparation conditions on variations in the chemical composition, morphology of the biochar powders, and degree of graphitization of carbonaceous materials were investigated. Based on structural investigations (X-ray diffraction analysis and Raman spectroscopy), it was observed that disordered carbon particles developed during the application of thermal treatments. The use of X-ray fluorescence enabled a comparative analysis of the chemical composition of the inorganic matter in biocarbon-based samples. Additionally, the gasification of carbonaceous-based samples vs. time at a temperature of 850 °C was investigated in a H2O or CO2 gas atmosphere. The analysis demonstrated the conversion rate of biochar obtained from pistachio shells to H2, CH4 and CO during steam gasification. The electrochemical investigations of the DC-SOFCs that were supplied with biochars obtained from pistachio shells were characterized by satisfactory values for the current and power densities at a temperature range of 700-850 °C. However, a higher power output of the DC-SOFCs was observed when CO2 was introduced to the anode chamber. Therefore, the impact of the Boudouard reaction on the performance of DC-SOFCs was confirmed. The chars that were prepared from pistachio shells were adequate for solid fuels for utilization in DC-SOFCs.

Effects of Montmorillonite and Gentamicin Addition on the Properties of Electrospun Polycaprolactone Fibers.

Electrospinning was used to obtain multifunctional fibrous composite materials with a matrix of poly-ɛ-caprolactone (PCL) and 2 wt.% addition of a nanofiller: montmorillonite (MMT), montmorillonite intercalated with gentamicin sulphate (MMTG) or gentamicin sulphate (G). In the first stage, the aluminosilicate gallery was modified by introducing gentamicin sulfate into it, and the effectiveness of the intercalation process was confirmed on the basis of changes in the clay particle size from 0.5 µm (for MMT) to 0.8 µm (for MMTG), an increase in the interplanar distance d001 from 12.3 Å (for MMT) to 13.9 Å (for MMTG) and altered clay grain morphology. In the second part of the experiment, the electrospinning process was carried out in which the polymer nonwovens with and without the modifier were prepared directly from dichloromethane (DCM) and N,N-dimethylformamide (DMF). The nanocomposite fibrous membranes containing montmorillonite were prepared from the same polymer solution but after homogenization with the modifier (13 wt.%). The degree of dispersion of the modifier was evaluated by average microarray analysis from observed area (EDS), which was also used to determine the intercalation of montmorillonite with gentamicin sulfate. An increase in the size of the fibers was found for the materials with the presence of the modifier, with the largest diameters measured for PCL_MMT (625 nm), and the smaller ones for PCL_MMTG (578 nm) and PCL_G (512 nm). The dispersion of MMT and MMTG in the PCL fibers was also confirmed by indirect studies such as change in mechanical properties of the nonwovens membrane, where the neat PCL nonwoven was used as a reference material. The addition of the modifier reduced the contact angle of PCL nonwovens (from 120° for PCL to 96° for PCL_G and 98° for PCL_MMTG). An approximately 10% increase in tensile strength of the nonwoven fabric with the addition of MMT compared to the neat PCL nonwoven fabric was also observed. The results of microbiological tests showed antibacterial activity of all obtained materials; however, the inhibition zones were the highest for the materials containing gentamicin sulphate, and the release time of the active substance was significantly extended for the materials with the addition of montmorillonite containing the antibiotic. The results clearly show that the electrospinning technique can be effectively used to obtain nanobiocomposite fibers with the addition of nonintercalated and intercalated montmorillonite with improved strength and increased stiffness compared to materials made only of the polymer fibers, provided that a high filler dispersion in the spinning solution is obtained.

Effects of Process Parameters on Structure and Properties of Melt-Blown Poly(Lactic Acid) Nonwovens for Skin Regeneration.

Skin regeneration requires a three-dimensional (3D) scaffold for cell adhesion, growth and proliferation. A type of the scaffold offering a 3D structure is a nonwoven material produced via a melt-blown technique. Process parameters of this technique can be adapted to improve the cellular response. Polylactic acid (PLA) was used to produce a nonwoven scaffold by a melt-blown technique. The key process parameters, i.e., the head and air temperature, were changed in the range from 180-270 °C to obtain eight different materials (MB1-MB8). The relationships between the process parameters, morphology, porosity, thermal properties and the cellular response were explored in this study. The mean fiber diameters ranged from 3 to 120 µm. The average material roughness values were between 47 and 160 µm, whereas the pore diameters ranged from 5 to 400 µm. The calorimetry thermograms revealed a correlation between the temperature parameters and crystallization. The response of keratinocytes and macrophages exhibited a higher cell viability on thicker fibers. The cell-scaffold interaction was observed via SEM after 7 days. This result proved that the features of melt-blown nonwoven scaffolds depended on the processing parameters, such as head temperature and air temperature. Thanks to examinations, the most suitable scaffolds for skin tissue regeneration were selected.

Multifunctional biodegradable polymer/clay nanocomposites with antibacterial properties in drug delivery systems.

PURPOSE: The aim of this study was to investigate the possibility of intercalation of gentamicin and neomycin in montmorillonite (MMT) nanofillers, as well as to study the in vitro antimicrobial properties of nanocomposite films containing a small amount of thus obtained nanofillers. METHODS: The polylactide matrix (PLA) nanocomposite films with drug-intercalated montmorillonite fillers were obtained by casting after intercalation of drugs in aqueous solutions. The efficiency of intercalation has been confirmed by X-ray diffraction (XRD) and Zeta potential measurements. The materials were studied for surface wettability, roughness and mechanical properties during 6 weeks of incubation in phosphate buffer saline, and their bactericidal activity was tested against Escherichia coli bacteria before and after 6 weeks of incubation in distilled water at 37 °C. The presence of antibiotics during the incubation was monitored by conductivity and pH measurements. RESULTS: The results indicate that nanocomposite polylactide films with montmorillonite filler intercalated with gentamicin and neomycin tend to degrade faster that their counterparts with non-intercalated fillers, which affects their mechanical properties. However, drug intercalation provided an antibacterial activity, which was confirmed by the presence of zones inhibiting the growth of Gram-negative bacteria for both antibiotics. It was also confirmed that the interaction of antibiotics with clay and polymer matrix did not adversely affect this bactericidal effect. CONCLUSIONS: Montmorillonite can be successfully intercalated with both gentamicin and neomycin, and then used as active filler for polylactide films having very good antibacterial properties, therefore their use in biomedical applications can be significantly expanded.

Fiber-Based Composite Meshes with Controlled Mechanical and Wetting Properties for Water Harvesting.

Water is the basis of life in the world. Unfortunately, resources are shrinking at an alarming rate. The lack of access to water is still the biggest problem in the modern world. The key to solving it is to find new unconventional ways to obtain water from alternative sources. Fog collectors are becoming an increasingly important way of water harvesting as there are places in the world where fog is the only source of water. Our aim is to apply electrospun fiber technology, due to its high surface area, to increase fog collection efficiency. Therefore, composites consisting of hydrophobic and hydrophilic fibers were successfully fabricated using a two-nozzle electrospinning setup. This design enables the realization of optimal meshes for harvesting water from fog. In our studies we focused on combining hydrophobic polystyrene (PS) and hydrophilic polyamide 6 (PA6), surface properties in the produced meshes, without any chemical modifications, on the basis of new hierarchical composites for collecting water. This combination of hydrophobic and hydrophilic materials causes water to condense on the hydrophobic microfibers and to run down on the hydrophilic nanofibers. By adjusting the fraction of PA6 nanofibers, we were able to tune the mechanical properties of PS meshes and importantly increase the efficiency in collecting water. We combined a few characterization methods together with novel image processing protocols for the analysis of fiber fractions in the constructed meshes. The obtained results show a new single-step method to produce meshes with enhanced mechanical properties and water collecting abilities that can be applied in existing fog water collectors. This is a new promising design for fog collectors with nano- and macrofibers which are able to efficiently harvest water, showing great application in comparison to commercially available standard meshes.

Roughness and Fiber Fraction Dominated Wetting of Electrospun Fiber-Based Porous Meshes.

Wettability of electrospun fibers is one of the key parameters in the biomedical and filtration industry. Within this comprehensive study of contact angles on three-dimensional (3D) meshes made of electrospun fibers and films, from seven types of polymers, we clearly indicated the importance of roughness analysis. Surface chemistry was analyzed with X-ray photoelectron microscopy (XPS) and it showed no significant difference between fibers and films, confirming that the hydrophobic properties of the surfaces can be enhanced by just roughness without any chemical treatment. The surface geometry was determining factor in wetting contact angle analysis on electrospun meshes. We noted that it was very important how the geometry of electrospun surfaces was validated. The commonly used fiber diameter was not necessarily a convincing parameter unless it was correlated with the surface roughness or fraction of fibers or pores. Importantly, this study provides the guidelines to verify the surface free energy decrease with the fiber fraction for the meshes, to validate the changes in wetting contact angles. Eventually, the analysis suggested that meshes could maintain the entrapped air between fibers, decreasing surface free energies for polymers, which increased the contact angle for liquids with surface tension above the critical Wenzel level to maintain the Cassie-Baxter regime for hydrophobic surfaces.

Combustion and kinetic parameters estimation of torrefied pine, acacia and Miscanthus giganteus using experimental and modelling techniques.

A novel approach, linking both experiments and modelling, was applied to obtain a better understanding of combustion characteristics of torrefied biomass. Therefore, Pine, Acacia and Miscanthus giganteus have been investigated under 260°C, 1h residence time and argon atmosphere. A higher heating value and carbon content corresponding to a higher fixed carbon, lower volatile matter, moisture content, and ratio O/C were obtained for all torrefied biomass. TGA analysis was used in order to proceed with the kinetics study and Chemkin calculations. The kinetics analysis demonstrated that the torrefaction process led to a decrease in Ea compared to raw biomass. The average Ea of pine using the KAS method changed from 169.42 to 122.88kJ/mol. The changes in gaseous products of combustion were calculated by Chemkin, which corresponded with the TGA results. The general conclusion based on these investigations is that torrefaction improves the physical and chemical properties of biomass.