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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.

In the past two decades, a growing body of research regarding the utilization of natural bacterial pigments or dyes for textile dyeing has emerged. Bacterial pigments are bacterial secondary metabolites that usually have bright colors and some special properties (e.g., antimicrobial, antioxidative, UV protective etc.). In addition to their high production yield, these special properties led scientists to research and develop methods for utilizing bacterial pigments in textile dyeing. This study presents the current state this field of research, with a focus on the dyeing potential of bacterial pigments for different types of textile material. The potential future directions of research in this area are also highlighted. In addition to the durable dyeing of textiles, bacterial pigments with special properties, such as antimicrobial activity, can add multifunctionality to dyed materials, thus increasing the value of the final product. This emerging field of research will also have a great impact on sustainability and the environment, contributing to the decreased usage of synthetic dyes in the textile industry.

Halochromic (pH-responsive) material was obtained by dyeing functionalized viscose fabric with a crude extract from Streptomyces sp. strain NP4. The functionalization of the fabric before dyeing was performed to make cellulose susceptible to coloration with NP4 extract. Two combined pre-treatment steps were used, oxidation to obtain dialdehyde cellulose and chitosan deposition after oxidation. Chitosan was deposited onto untreated fabric as well, while only oxidized viscose was also investigated for dyeing. Functionalization by both protocols made viscose susceptible to dyeing with the notion that the deposition of chitosan onto oxidized viscose produced the darkest shade on the material. Dyed fabrics showed visual pH responsiveness in the range pH 4–10, with a color change from pink to red (pH 4–pH 7) and a major color change from red to blue (pH 7–pH 10) whereby fabric was tested and could withstand 10 color-changing cycles. Cytotoxicity assay confirmed the non-toxic nature of dyed material, which indicates its possible use as wound dressing’s indicators.Graphic abstract

In this work, alkali and oxidative treatments were employed to obtain flax fibers with different content of hemicelluloses and lignin, in order to study the influence of chemical composition on structure and sorption properties of flax fibers. The flax fibers were characterized using FTIR spectroscopy and FESEM microscopy, and by determination of chemical composition, carboxyl group content, electrokinetic and sorption properties. Adsorption of silver ions was used to evaluate flax fiber sorption properties, but also to obtain antimicrobial fibers whose antimicrobial activity was tested against Gram-negative bacteria Escherichia coli , Gram-positive bacteria Staphylococcus aureus and fungi Candida albicans . The progressive removal of hemicelluloses or lignin influenced the sorption properties through the increased liberation of elementary fibers and accessibility of functional surface groups of flax fibers. Removal of hemicelluloses led to increase of iodine sorption without significant change in functional groups content and electrokinetic properties. On the other hand, lignin removal led to an increase of functional groups content, namely carboxyl groups, which in turn influenced better moisture and silver ions sorption. Flax fibers with incorporated silver exhibit fair antimicrobial activity against Gram (−) E. coli , Gram (+) S. aureus and fungi C. albicans .

The electrokinetic properties of materials give useful insight into the behavior of surfaces in contact with liquids and other compounds and their quantification is a powerful tool to predict their behavior during further processing and application, especially in textile materials. In this work, we perform a comparative analysis of influence of the two most common selective oxidative protocols for viscose (regenerated cellulose) fabrics on subsequent functionalization with chitosan, and cellulose fabrics’ electrokinetic properties, zeta potential in a pH range of approx. 3–10, and isoelectric point (IEP). For oxidation before deposition of chitosan, sodium periodate and 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) were used. The content of functional groups in oxidized cellulose fabric (carboxyl and carbonyl groups) was determined by titration methods, while amino functional groups’ availability in samples with chitosan was determined using the CI acid orange 7 dye absorption method. This study reveals that the periodate oxidation (PO) of cellulose is more effective for binding chitosan onto material, which gave rise to higher availability of amino groups onto cellulose/chitosan material, which also influenced the shift in zeta potential curve towards positive values at a pH below 5. Analysis of a relationship between zeta potential increase at pH 4.4 and amino groups’ amount measured using absorption of CI acid orange 7 dye at pH 4.4 revealed dependency that can be fitted linearly or exponentially, with the latter providing the better fit (R2 = 0.75).

In this work, a possibility to use atmospheric pressure plasma treatment to clean cotton fibers surface was investigated. Dielectric barrier discharge (DBD) operating in air was used as plasma source. After plasma treatment, cotton fibers were characterized using several surface techniques: SEM, XPS, ATR-FTIR and zeta potential measurement; also wettability was evaluated using capillary height measurement. Results of investigation showed that plasma treatment primarily affects cuticle and primary wall of cotton which provides cleaning of the fibers surface. This caused increase of polar groups accessibility and better wettability of cotton samples. An attempt has been made to locate influence of plasma treatment on different structural layers of cotton fibers using different surface techniques. In addition, surface charge was investigated through measuring streaming potential and a connection was established between zeta potential and plasma treatment time. Furthermore, it was shown that measuring of zeta potential could be used as an additional technique to track changes and elucidate mechanisms of plasma treatment influence on cotton fibers.

In this work, materials with potential biomedical applications constituted by fibrous poly(ethylene oxide), PEO, are prepared by solution blow spinning (SBS). The SBS setup has a cylindrical collector for which the rotational speed and size are varied to study its effect on the final morphology of the materials. The morphology is inspected using field emission scanning electron microscopy and studied using image analysis. As a result, many doubts were generated because of the use of different methods of image analysis, therefore a simpler and more conventional method using Image J open-source software was used to ensure the accuracy of the final interpretation. It is shown that fiber size and orientation depend on the linear speed associated with the surface of the collector more than on its rotational speed; therefore, it can be said that the morphology of materials prepared by SBS will depend on the size, shape, and rotational speed of the collector. When the linear speed of the cylindrical collector increases, fibers get thinner, less entangled, and more oriented. It is clear, therefore, that the linear speed of material collection by solution blow spinning is a very important parameter of processing to control the final morphology of materials manufactured by that method. Since morphology can affect the final properties of the materials the simple variation of the linear speed might have important implications on their final performance for different biomedical applications.

Silk, traditionally acclaimed as the “queen of fiber,” has been widely used thanks to its brilliant performance such as gentleness, smoothness and comfortableness. Owing to its mechanical characteristics and biocompatibility silk has a definitive role in biomedical applications, both as fibroin and fabric. In this work, the simultaneous dyeing and functionalization of silk fabric with pigments from Streptomyces anulatus BV365 were investigated. This strain produced high amounts of orange extracellular pigments on mannitol-soy flour agar, identified as actinomycin D, C2 and C3. The application of purified actinomycins in the dyeing of multifiber fabric was assessed. Actinomycins exhibited a high affinity towards protein fibers (silk and wool), but washing durability was maintained only with silk. Acidic condition (pH5) and high temperature (65°C) facilitated the silk dyeing. The morphologies and chemical components of the treated silk fabrics were analyzed using scanning electron microscopy and Fourier transform infrared spectroscopy. The results showed the pigments bind to the silk through interaction with the carbonyl group in silk fibroin rendering the functionalized, yet surface that does not cause skin irritation. The treated silk exhibited a remarkable antibacterial effect, while the biocompatibility test performed with 3D-reconstructed human epidermis model indicated safe biological properties, paving the way for future application of this material in medicine.

Cellulose fabrics (viscose and cotton) were treated with atmospheric pressure dielectric barrier discharge (DBD) in air. After DBD treatment, samples were characterized and volume electrical resistance was measured under different relative humidity conditions (φ=40-55 %). Results have shown that DBD treatment increases wettability and polar surface functional groups content, which consequently causes a decrease of volume electrical resistivity of cellulose fabrics in measured relative humidity range (φ=40-55 %). Metal ions (silver, copper, and zinc) were incorporated in untreated and plasma treated samples through sorption from aqueous solutions and incorporation of metal ions into plasma treated cellulose samples decreased electrical resistivity even further. Resistivity of cotton and viscose fabrics with incorporated metal ions followed the order Zn2+ > Cu2+ > Ag+. The most pronounced decrease, for entire order of a magnitude, was obtained by modification of cotton fabric with DBD and silver ions, where value of resistivity dropped from GΩ to a several dozens of MΩ.

The objective of this research was to impart antimicrobial properties to hemp fibers by incorporation of silver ions in hemp fibers by chemisorption. Sorption properties of hemp fibers were improved by non-selective oxidation using hydrogen peroxide and potassium permanganate. The optimal conditions for silver ions sorption by hemp fibers were determined by changing sorption conditions: pH value and concentration of aqueous silver nitrate solution, as well as duration of sorption. The maximum sorption capacity of modified hemp fibers was 1.84 mmol of Ag + ions per gram of fibers. Antimicrobial activity of silver-loaded hemp fibers against different pathogens: Staphylococcus aureus, Escherichia coli , and Candida albicans was evaluated in vitro . Obtained silver-loaded hemp fibers show antimicrobial activity against tested pathogens.