Properties and environmental sustainability of fungal chitin nanofibril reinforced cellulose acetate films and nanofiber mats by solution blow spinning.

Materials from biological origin composed by renewable carbon facilitate the transition from linear carbon-intensive economy to a sustainable circular economy. Accordingly, we use solution blow spinning to develop fully biobased cellulose acetate films and nanofiber mats reinforced with fungal chitin nanofibrils (ChNFs), an emerging bio-colloid with lower carbon footprint compared to crustacean-derived nanochitin. This study incorporates fungal ChNFs into spinning processes for the first time. ChNF addition reduces film surface roughness, modifies film water affinity, and tailors the nanofiber diameter of the mats. The covalently bonded ß-D-glucans of ChNFs act as a binder to improve the interfacial properties and consequently load transference to enhance the mechanical properties. Accordingly, the Young's modulus of the films increases from 200 ± 18 MPa to 359 ± 99 MPa with 1.5 wt% ChNFs, while the elongation at break increases by ~45 %. Life cycle assessment (LCA) is applied to quantify the environmental impacts of solution blow spinning for the first time, providing global warming potential values of 69.7-347.4 kg·CO2-equiv.·kg-1. Additionally, this work highlights the suitability of ChNFs as reinforcing fillers during spinning and proves the reinforcing effect of mushroom-derived chitin in bio-based films, opening alternatives for sustainable materials development beyond nanocelluloses in the near future.

"Nano in Nano"-Incorporation of ZnO Nanoparticles into Cellulose Acetate-Poly(Ethylene Oxide) Composite Nanofibers Using Solution Blow Spinning.

In this work, the preparation and characterization of composites from cellulose acetate (CA)-poly(ethylene oxide) (PEO) nanofibers (NFs) with incorporated zinc oxide nanoparticles (ZnO-NPs) using solution blow spinning (SBS) is reported. CA-PEO nanofibers were produced by spinning solution that contained a higher CA-to-PEO ratio and lower (equal) CA-to-PEO ratio. Nanoparticles were added to comprise 2.5% and 5% of the solution, calculated on the weight of the polymers. To have better control of the SBS processing conditions, characterization of the spinning suspensions is carried out, which reveals a decrease in viscosity (two- to eightfold) upon the addition of NPs. It is observed that this variation of viscosity does not significantly affect the mean diameters of nanofibers, but does affect the mode of the nanofibers' size distribution, whereby lower viscosity provides thinner fibers. FESEM-EDS confirms ZnO NP encapsulation into nanofibers, specifically into the CA component based on UV-vis studies, since the release of ZnO is not detected for up to 5 days in deionized water, despite the significant swelling of the material and accompanied dissolution of water-soluble PEO. Upon the dissolution of CA nanofibers into acetone, immediate release of ZnO is detected, both visually and by spectrometer. ATR-FTIR studies reveal interaction of ZnO with the CA component of composite nanofibers. As ZnO nanoparticles are known for their bioactivity, it can be concluded that these CA-PEO-ZnO composites are good candidates to be used in filtration membranes, with no loss of incorporated ZnO NPs or their release into an environment.

Effect of Collector Rotational Speed on the Morphology and Structure of Solution Blow Spun Polylactic Acid (PLA).

Apart from structure and composition, morphology plays a significant role in influencing the performance of materials in terms of both bulk and surface behavior. In this work, polylactic acid (PLA) constituted by submicrometric fibers is prepared. Using a modified electrospinning (ES) device to carry out solution blow spinning (SBS), the fibrillar morphology is modified, with the aim to induce variations in the properties of the material. The modification of the ES device consists of the incorporation of a source of pressurized gas (air) and a 3D-printed nozzle of our own design. For this work, the morphology of the PLA submicrometric fibers is modified by varying the rotational speed of the collector in order to understand its influence on different properties and, consequently, on the performance of the material. The rotational speed of a cylindrical collector (250, 500, 1000 and 2000 rpm) is considered as variable for changing the morphology. Morphological study of the materials was performed using scanning electron microscopy and image analysis carried out with ImageJ 1.54f software. Besides a morphology study, structural characterization by Fourier transformed infrared spectroscopy using attenuated total reflectance of prepared materials is carried out. Finally, the morphology and structure of produced PLA fibrous mats were correlated with the analysis of mechanical properties, wettability behavior and adhesion of DH5-α E. coli bacteria. It is of interest to highlight how small morphological and chemical structure variations can lead to important changes in materials' performance. These changes include, for example, those above 30% in some mechanical parameters and clear variations in bacterial adhesion capacity.

Solution blow co-spinning of cellulose acetate with poly(ethylene oxide). Structure, morphology, and properties of nanofibers.

Cellulose acetate (CA) nanofibers are prepared using solution blow co-spinning (SBS) with poly(ethylene oxide) (PEO). The pure CA membranes are obtained by washing water-soluble PEO from the fibrous CA-PEO blend. Nanofibrous membranes are characterized using optical and scanning electron microscopy (SEM), differential scanning calorimetry (DSC), infrared spectroscopy (ATR-FTIR), and surface zeta potential measurements. Thermal transitions from DSC and ATR-FTIR spectra analysis were used to confirm the removal of the PEO. Although the characteristic signals of PEO are not observed by FTIR, an additional thermal step transition in CA nanofibers indicates the embedding of a small amount of PEO (up to 6 wt%). SEM analysis shows that CA-PEO blends are constituted by fibers with mean diameters from 671 to 857 nm (depending on the SBS parameters), while after PEO removal, diameters range from 567 to 605 nm. We propose a new method for staining CA-PEO membranes with iodine solution in absolute ethanol that allows the differentiation of CA and PEO components with an optical microscope. The microscopy results suggest that PEO assists in the spinning by enveloping CA nanofibers, allowing uninterrupted processing. The successful deacetylation to cellulose using an aqueous KOH solution is confirmed with zeta potential measurements and ATR-FTIR.

Active Cellulose Acetate/Chitosan Composite Films Prepared Using Solution Blow Spinning: Structure and Electrokinetic Properties.

Cellulose acetate (CA), a very promising derivative of cellulose, has come into the focus of research due to its highly desired good film-forming ability for food packaging applications. Frequently, this derivative is used in combination with other compounds (polymers, nanoparticles) in order to obtain active materials. Here, we report the preparation of thin films made of cellulose acetate loaded with chitosan (CS) using the solution blow spinning (SBS) method. Films are prepared by SBS processing of the polymers mixture solution, considering the following variables: (i) the concentration of cellulose acetate and chitosan in the solution and (ii) the solvent system consisting of acetic or formic acid. The prepared materials are characterized in terms of physical properties, roughness (optical profilometer), porosity, wettability (contact angle measurements), chemical structure (Fourier transform infrared spectrometry), and electrokinetic properties (zeta potential). SBS enables the preparation of CA/CS films with high water vapor permeability, high porosity, and also higher water contact angle compared with pure CA films. The electrokinetic properties of composites are influenced by the inclusion of chitosan, which causes a shift of the isoelectric point (IEP) towards higher pH values, but the magnitude of the shift is not in correlation with chitosan concentration. Adsorption kinetic studies using bovine serum albumin (BSA) as a model protein reveal that chitosan modified cellulose acetate films manifest low affinity towards proteins that suggests prevention of biofilm formation on its surface.

Obtaining Medical Textiles Based on Viscose and Chitosan/Zinc Nanoparticles with Improved Antibacterial Properties by Using a Dielectric Barrier Discharge.

This study aimed to obtain functional viscose textiles based on chitosan coatings with improved antibacterial properties and washing durability. For that reason, before functionalization with chitosan/zinc nanoparticles (NCH+Zn), the viscose fabric was modified by nonthermal gas plasma of dielectric barrier discharge (DBD) to introduce into its structure functional groups suitable for attachment of NCH+Zn. NCH+Zn were characterized by measurements of hydrodynamic diameter and zeta potential and AFM. DBD-plasma-modified and NCH+Zn-functionalized fabrics were characterized by zeta potential measurements, ATR-FTIR spectroscopy, the calcium acetate method (determination of content of carboxyl and aldehyde groups), SEM, breaking-strength measurements, elemental analysis, and ICP-OES. Their antibacterial activity was determined under dynamic contact conditions. In addition to SEM, the NCH+Zn distributions on viscose fabrics were also indirectly characterized by measuring their absorbent capacities before and after functionalization with NCH+Zn. Washing durability was monitored through changes in the zeta potential, chitosan and zinc content, and antibacterial activity after 1, 3, and 5 washing cycles. The obtained results showed that DBD plasma modification contributed to the simultaneous improvement of NCH+Zn sorption and antibacterial properties of the viscose fabric functionalized with NCH+Zn, and its washing durability, making it suitable for the production of high-value-added medical textiles.

Cellulose-Based Nanofibers Processing Techniques and Methods Based on Bottom-Up Approach-A Review.

In the past decades, cellulose (one of the most important natural polymers), in the form of nanofibers, has received special attention. The nanofibrous morphology may provide exceptional properties to materials due to the high aspect ratio and dimensions in the nanometer range of the nanofibers. The first feature may lead to important consequences in mechanical behavior if there exists a particular orientation of fibers. On the other hand, nano-sizes provide a high surface-to-volume ratio, which can have important consequences on many properties, such as the wettability. There are two basic approaches for cellulose nanofibers preparation. The top-down approach implies the isolation/extraction of cellulose nanofibrils (CNFs) and nanocrystals (CNCs) from a variety of natural resources, whereby dimensions of isolates are limited by the source of cellulose and extraction procedures. The bottom-up approach can be considered in this context as the production of nanofibers using various spinning techniques, resulting in nonwoven mats or filaments. During the spinning, depending on the method and processing conditions, good control of the resulting nanofibers dimensions and, consequently, the properties of the produced materials, is possible. Pulp, cotton, and already isolated CNFs/CNCs may be used as precursors for spinning, alongside cellulose derivatives, namely esters and ethers. This review focuses on various spinning techniques to produce submicrometric fibers comprised of cellulose and cellulose derivatives. The spinning of cellulose requires the preparation of spinning solutions; therefore, an overview of various solvents is presented showing their influence on spinnability and resulting properties of nanofibers. In addition, it is shown how bottom-up spinning techniques can be used for recycling cellulose waste into new materials with added value. The application of produced cellulose fibers in various fields is also highlighted, ranging from drug delivery systems, high-strength nonwovens and filaments, filtration membranes, to biomedical scaffolds.

Iso- and Anisotropic Etching of Micro Nanofibrillated Cellulose Films by Sequential Oxygen and Nitrogen Gas Plasma Exposure for Tunable Wettability on Crystalline and Amorphous Regions.

The surface of cellulose films, obtained from micro nanofibrillated cellulose produced with different enzymatic pretreatment digestion times of refined pulp, was exposed to gas plasma, resulting in a range of surface chemical and morphological changes affecting the mechanical and surface interactional properties. The action of separate and dual exposure to oxygen and nitrogen cold dielectric barrier discharge plasma was studied with respect to the generation of roughness (confocal laser and atomic force microscopy), nanostructural and chemical changes on the cellulose film surface, and their combined effect on wettability. Elemental analysis showed that with longer enzymatic pretreatment time the wetting response was sensitive to the chemical and morphological changes induced by both plasma gases, but distinctly oxygen plasma was seen to induce much greater morphological change while nitrogen plasma contributed more to chemical modification of the film surface. In this novel study, it is shown that exposure to oxygen plasma, subsequently followed by exposure to nitrogen plasma, leads first to an increase in wetting, and second to more hydrophobic behaviour, thus improving, for example, suitability for printing using polar functional inks or providing film barrier properties, respectively.

Effect of plasma treatment on chemical composition, structure and sorption properties of lignocellulosic hemp fibers (Cannabis sativa L.).

Hemp fibers with different amount of hemicelluloses and lignin were subjected to atmospheric pressure dielectric barrier discharge under different conditions (40 W and 80 W power of discharge, const. time 120 s) in order to study influence of plasma treatment on their structure and sorption properties. Wettability of plasma treated samples, compared with precursors, increased due to the changes in hemp fiber surface chemistry confirmed by ATR FTIR spectroscopy and increased roughness as a consequence of intensive surface etching, observed by SEM. After plasma treatment, wettability was the highest for hemp fibers with lower content of hemicelluloses (increase up to 9 times), while wettability of raw hemp fibers and fibers with lower content of lignin increased about 5 and 2 times, respectively. This investigation shows that plasma can be successfully used for improvement of raw hemp fibers wettability, even to substitute the chemical treatment for some applications of hemp.

Crude bacterial extracts of two new Streptomyces sp. isolates as bio-colorants for textile dyeing.

Renewed demand for incorporation of natural dyes (bio-colorants) in textile industry could be met through biotechnological production of bacterial pigments. Two new Streptomyces strains (NP2 and NP4) were isolated for the remarkable ability to produce diffusible deep blue and deep red pigment into fermentation medium. Crude mycelial extracts of both strains were used as bio-colorants in conventional textile dyeing procedures avoiding downstream purification procedures. The yields of bio-colorants obtained in this way were 62 and 84 mg per g of mycelia for Streptomyces sp. NP2 and Streptomyces sp. NP4, respectively. Through nuclear magnetic resonance analysis of crude extracts before and after dyeing procedures, it was shown that both extracts contained prodigiosin-like family of compounds that exhibited different dyeing capabilities towards different textile fibers. Polyamide and acrylic fibers were colored to the deepest shade, polyester and triacetate fibers to a noticeable, but much lower shade depth, while cotton and cellulosic fibers stained weakly. These results confirmed that crude bacterial extracts had the characteristics similar to those of ionic and disperse dyes, which was consistent with the identified polypyrrolic prodigiosin-like structures.