Synthetic silica fibers of different length, diameter and shape: synthesis and interaction with rat (NR8383) and human (THP-1) macrophages in vitro, including chemotaxis and gene expression profile.

BACKGROUND: Inhalation of biopersistent fibers like asbestos can cause strong chronic inflammatory effects, often resulting in fibrosis or even cancer. The interplay between fiber shape, fiber size and the resulting biological effects is still poorly understood due to the lack of reference materials. RESULTS: We investigated how length, diameter, aspect ratio, and shape of synthetic silica fibers influence inflammatory effects at doses up to 250 µg cm-2. Silica nanofibers were prepared with different diameter and shape. Straight (length ca. 6 to 8 µm, thickness ca. 0.25 to 0.35 µm, aspect ratio ca. 17:1 to 32:1) and curly fibers (length ca. 9 µm, thickness ca. 0.13 µm, radius of curvature ca. 0.5 µm, aspect ratio ca. 70:1) were dispersed in water with no apparent change in the fiber shape during up to 28 days. Upon immersion in aqueous saline (DPBS), the fibers released about 5 wt% silica after 7 days irrespectively of their shape. The uptake of the fibers by macrophages (human THP-1 and rat NR8383) was studied by scanning electron microscopy and confocal laser scanning microscopy. Some fibers were completely taken up whereas others were only partially internalized, leading to visual damage of the cell wall. The biological effects were assessed by determining cell toxicity, particle-induced chemotaxis, and the induction of gene expression of inflammatory mediators. CONCLUSIONS: Straight fibers were only slightly cytotoxic and caused weak cell migration, regardless of their thickness, while the curly fibers were more toxic and caused significantly stronger chemotaxis. Curly fibers also had the strongest effect on the expression of cytokines and chemokines. This may be due to the different aspect ratio or its twisted shape.

Reproductive toxicity assessment of cellulose nanofibers, citric acid, and branched polyethylenimine in sea urchins: Eco-design of nanostructured cellulose sponge framework (Part B).

In the framework of a safe-by-design approach, we previously assessed the eco-safety of nanostructured cellulose sponge (CNS) leachate on sea urchin reproduction. It impaired gamete quality, gamete fertilization competence, and embryo development possibly due to the leaching of chemical additives used during the CNS synthesis process. To extend this observation and identify the component(s) that contribute to CNS ecotoxicity, in the present study, we individually screened the cytotoxic effects on sea urchin Arbacia lixula and Paracentrotus lividus gametes and embryos of the three main constituents of CNS, namely cellulose nanofibers, citric acid, and branched polyethylenimine. The study aimed to minimize any potential safety risk of these components and to obtain an eco-safe CNS. Among the three CNS constituents, branched polyethylenimine resulted in the most toxic agent. Indeed, it affected the physiology and fertilization competence of male and female gametes as well as embryo development in both sea urchin species. These results are consistent with those previously reported for CNS leachate. Moreover, the characterisation of CNS leachate confirmed the presence of detectable branched polyethylenimine in the conditioned seawater even though in a very limited amount. Altogether, these data indicate that the presence of branched polyethylenimine is a cause-effect associated with a significant risk in CNS formulations due to its leaching upon contact with seawater. Nevertheless, the suggested safety protocol consisting of consecutive leaching treatments and conditioning of CNS in seawater can successfully ameliorate the CNS ecotoxicity while maintaining the efficacy of its sorbent properties supporting potential environmental applications.

Characterization and safety assessment of bamboo shoot shell cellulose nanofiber: Prepared by acidolysis combined with dynamic high-pressure microfluidization.

The preparation of cellulose nanofiber (CNF) using traditional methods is currently facing challenges due to concerns regarding environmental pollution and safety. Herein, a novel CNF was obtained from bamboo shoot shell (BSS) by low-concentration acid and dynamic high-pressure microfluidization (DHPM) treatment. The resulting CNF was then characterized, followed by in vitro and in vivo safety assessments. Compared to insoluble dietary fiber (IDF), the diameters of HIDF (IDF after low-concentration acid hydrolysis) and CNF were significantly decreased to 167.13 nm and 70.97 nm, respectively. Meanwhile, HIDF and CNF showed a higher crystallinity index (71.32 % and 74.35 %). Structural analysis results indicated the successful removal of lignin and hemicellulose of HIDF and CNF, with CNF demonstrating improved thermostability. In vitro, a high dose of CNF (1500 µg/mL) did not show any signs of cytotoxicity on Caco-2 cells. In vivo, no death was observed in the experimental mice, and there was no significant difference between CNF (1000 mg/kg·bw) and control group in hematological index and histopathological analysis. Overall, this study presents an environmentally friendly method for preparing CNF from BSS while providing evidence regarding its safety through in vitro and in vivo assessments, laying the foundation for its potential application in food.

Polycaprolactone/polyacrylic acid/graphene oxide composite nanofibers as a highly efficient sorbent to remove lead toxic metal from drinking water and apple juice.

Due to the characteristics of electrospun nanofibers (NFs), they are considered a suitable substrate for the adsorption and removal of heavy metals. Electrospun nanofibers are prepared based on optimized polycaprolactone (PCL, 12 wt%) and polyacrylic acid (PAA, 1 wt%) polymers loaded with graphene oxide nanoparticles (GO NPs, 1 wt%). The morphological, molecular interactions, crystallinity, thermal, hydrophobicity, and biocompatibility properties of NFs are characterized by spectroscopy (scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis), contact angle, and MTT tests. Finally, the adsorption efficacy of NFs to remove lead (Pb2+) from water and apple juice samples was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). The average diameter for PCL, PCL/PAA, and PCL/PAA/GO NFs was 137, 500, and 216 nm, respectively. Additionally, the contact angle for PCL, PCL/PAA, and PCL/PAA/GO NFs was obtained at 74.32º, 91.98º, and 94.59º, respectively. The cytotoxicity test has shown non-toxicity for fabricated NFs against the HUVEC endothelial cell line by more than 80% survival during 72 h. Under optimum conditions including pH (= 6), temperature (25 °C), Pb concentration (25 to 50 mg/L), and time (15 to 30 min), the adsorption efficiency was generally between 80 and 97%. The adsorption isotherm model of PCL/PAA/GO NFs in the adsorption of lead metal follows the Langmuir model, and the reaction kinetics follow the pseudo-second-order. PCL/PA/GO NFs have shown adsorption of over 80% in four consecutive cycles. The adsorption efficacy of NFs to remove Pb in apple juice has reached 76%. It is appropriate and useful to use these nanofibers as a high-efficiency adsorbent in water and food systems based on an analysis of their adsorption properties and how well they work.

Molecular mechanism for combined toxicity of micro(nano)plastics and carbon nanofibers to freshwater microalgae Chlorella pyrenoidosa.

The understanding of the environmental consequences resulting from the presence of micro(nano)plastics and carbon nanofibers (CNFs) in aquatic ecosystems is currently limited. This research endeavor sought to investigate the underlying molecular mechanisms by which engineered polystyrene-based microplastics (MPs)/nanoplastics (NPs) and CNFs, both individually and in combination, elicit toxic effects on an algal species Chlorella pyrenoidosa. The findings revealed that the combined toxicity of MPs/NPs and CNFs depended on the concentration of the mixture. As the concentration increased, the combined toxicity of MPs/NPs and CNFs was significantly greater than the toxicity of each component on its own. Furthermore, the combined toxicity of NPs and CNFs was higher than that of MPs and CNFs. The study integrated data on cell membrane integrity, oxidative stress, and antioxidant modulation to create an Integrated Biomarker Response index, which demonstrated that the co-exposure of algae to NPs and CNFs resulted in more severe cellular stress compared to exposure to NPs alone. Similarly, the combination of NPs and CNFs caused greater cellular stress than the combination of MPs and CNFs. Additionally, significant changes in the expression of stress-related genes caused by MPs/NPs alone and in combination with CNFs indicated that oxidative stress response, glucose metabolism, and energy metabolism played critical roles in particle-induced toxicity. Overall, this study provides the first insight into the toxicological mechanism of MPs/NPs and CNFs mixtures at the molecular level in freshwater microalgae.

Thermo-Chemical Cues-Mediated Strategy to Control Peptide Self-Assembly and Charge Transfer Complexation.

Peptide amphiphiles (PAs) are known for their remarkable ability to undergo molecular self-assembly, a process that is highly responsive to the local microenvironment. Herein, we design a pyrene tethered peptide amphiphile Py-VFFAKK, 1 that exhibits pathway-driven self-assembly from metastable nanoparticles to kinetically controlled nanofibers and thermodynamically stable twisted bundles upon modulations in pH, temperature, and chemical cues. The presence of the pyrene moiety ensures donation of the electron to an electron acceptor, namely, 7,7,8,8-tetracyanoquinodimethane (TCNQ), to form a supramolecular charge transfer complex in aqueous solution that was studied in detail with microscopic and spectroscopic techniques. Excitation of the donor species in its excimer state facilitates electron donation to the acceptor moiety, paving away a long-lived charge-separated state that persists for over a nanosecond, as ascertained through transient absorption spectroscopy. Finally, the self-assembled charge transfer complex is explored toward antimicrobial properties with Escherichia coli while maintaining biocompatibility toward L929 mice fibroblast cells.

Effect of different antibacterial agents doping in PET-based electrospun nanofibrous membranes on air filtration and antibacterial performance.

In order to reduce the particulate matter pollution to human health in producing environments, series of polyethylene terephthalate/polyvinyl alcohol (PET/PVA) based nanofibrous membranes were fabricated and investigated the dust collection and antibacterial activity. Silver nanoparticles (AgNPs), berberine (Ber) and titanium oxide nanoparticles (TiO2NPs) were selected as antibacterial agents. These novel membranes were well-characterized using SEM, FTIR, TG, etc. techniques. Results of the dust filtration showed that PET/PVA/Ag membrane had the best filtration efficiency of 99.87% for sodium chloride (NaCl) and 99.89% for dioctyl sebacate (DEHS), held low pressure drop of 160.1 Pa for NaCl and 165.3 Pa for DEHS, and posed a high tensile strength of 4.91 MPa. The bacteriostasis studies exhibited that PET/PVA/TiO2 and PET/PVA/Ag membrane showed the highest bacteriological effect on Escherichia coli (98.7%) and Staphylococcus aureus (95.9%), respectively. Meanwhile, in vitro cytotoxicity test indicated no potential cytotoxicity existed in the cell culture process of these two antibacterial membranes. Moreover, the charge distribution in the nanofibers was increased by these antibacterial agents to improve the filtration performance. The dust filtration process synergistically promoted with the antibacterial process in the antibacterial membranes. It was expected that these membranes could be efficient filter medias with broad application prospects in the field of individual protection.

Carbon nanotubes and nanofibers seen as emerging threat to fish: Historical review and trends.

Since the discovery of the third allotropic carbon form, carbon-based one-dimensional nanomaterials (1D-CNMs) became an attractive and new technology with different applications that range from electronics to biomedical and environmental technologies. Despite their broad application, data on environmental risks remain limited. Fish are widely used in ecotoxicological studies and biomonitoring programs. Thus, the aim of the current study was to summarize and critically analyze the literature focused on investigating the bioaccumulation and ecotoxicological impacts of 1D-CNMs (carbon nanotubes and nanofibers) on different fish species. In total, 93 articles were summarized and analyzed by taking into consideration the following aspects: bioaccumulation, trophic transfer, genotoxicity, mutagenicity, organ-specific toxicity, oxidative stress, neurotoxicity and behavioral changes. Results have evidenced that the analyzed studies were mainly carried out with multi-walled carbon nanotubes, which were followed by single-walled nanotubes and nanofibers. Zebrafish (Danio rerio) was the main fish species used as model system. CNMs' ecotoxicity in fish depends on their physicochemical features, functionalization, experimental design (e.g. exposure time, concentration, exposure type), as well as on fish species and developmental stage. CNMs' action mechanism and toxicity in fish are associated with oxidative stress, genotoxicity, hepatotoxicity and cardiotoxicity. Overall, fish are a suitable model system to assess the ecotoxicity of, and the environmental risk posed by, CNMs.

Contaminant microorganisms in the in vitro evaluation of cellular responses of cellulose nanofibers and their microbial inactivation using gamma irradiation.

Cellulose nanofibers (CNFs) are fibrous nanomaterials produced from plants. Since some nanomaterials are toxic, toxicity evaluation, including in vitro examinations using cultured cells, is essential for the effective use of CNFs. On the other hand, microorganisms in the environment can contaminate CNF suspensions. The contamination of CNF samples and the effects of contaminating microorganisms on in vitro examinations were investigated in this study. Microorganism contamination in CNF samples was examined, and microbial inactivation of CNF suspensions using gamma irradiation was evaluated. After gamma-ray irradiation at absorbed doses of 0.5, 1, 5, and 10 kGy, the cellular effects of CNF suspensions were examined using 6 types of cultured cell, HaCaT, A549, Caco-2, MeT-5A, THP-1, and NR8383 cells. CNF samples were contaminated with bacteria and CNF suspensions exhibited endotoxin activity. Gamma irradiation effectively inactivated the microorganisms contained in the CNF suspensions. When the absorbed dose was 10 kGy, the fiber length of CNF was shortened, but the effect on CNF was small at 1.0 kGy or less. CNF suspensions showed lipopolysaccharides (LPS)-like cellular responses and strongly induced interleukin-8, especially in macrophages. Absorbed doses of at least 10 kGy did not affect the LPS-like activity. In this study, it was shown that the CNF suspension may be contaminated with microorganisms. Gamma irradiation was effective for microbial inactivation of suspension for invitor toxicity evaluation of CNF. In vitro evaluation of CNFs requires attention to the effects of contaminants such as LPS.

Effects of polypropylene nanofibers on soft corals.

Current information regarding the effects of both micro- and nano-plastic debris on coral reefs is limited; especially the toxicity onto corals from nano-plastics originating from secondary sources such as fibers from synthetic fabrics. Within this study, we exposed the alcyonacean coral Pinnigorgia flava to different concentrations of polypropylene secondary nanofibers (0.001, 0.1, 1.0 and 10 mg/L) and then assayed mortality, mucus production, polyps retraction, coral tissue bleaching, and swelling. The assay materials were obtained by artificially weathering non-woven fabrics retrieved from commercially available personal protective equipment. Specifically, polypropylene (PP) nanofibers displaying a hydrodynamic size of 114.7 ± 8.1 nm and a polydispersity index (PDI) of 0.431 were obtained after 180 h exposition in a UV light aging chamber (340 nm at 0.76 Wˑm-2ˑnm-1). After 72 h of PP exposure no mortality was observed but there were evident stress responses from the corals tested. Specifically, the application of nanofibers at different concentrations caused significant differences in mucus production, polyps retraction and coral tissue swelling (ANOVA, p < 0.001, p = 0.015 and p = 0.015, respectively). NOEC (No Observed Effect Concentration) and LOEC (Lowest Observed Effect concentration) at 72 h resulted 0.1 mg/L and 1 mg/L, respectively. Overall, the study indicates that PP secondary nanofibers can cause adverse effects on corals and could potentially act as a stress factor in coral reefs. The generality of the method of producing and assaying the toxicity of secondary nanofibers from synthetic textiles is also discussed.

Metabolomics of V2O5 nanoparticles and V2O5 nanofibers in human airway epithelial BEAS-2B cells.

Vanadium is a toxic metal listed by the IARC as possibly carcinogenic to humans. Manufactured nanosize vanadium pentoxide (V2O5) materials are used in a wide range of industrial sectors and recently have been developed as nanomedicine for cancer therapeutics, yet limited information is available to evaluate relevant nanotoxicity. In this study we used high-resolution metabolomics to assess effects of two V2O5 nanomaterials, nanoparticles and nanofibers, at exposure levels (0.01, 0.1, and 1 ppm) that did not cause cell death (i.e., non-cytotoxic) in a human airway epithelial cell line, BEAS-2B. As prepared, V2O5 nanofiber exhibited a fibrous morphology, with a width approximately 63 ± 12 nm and length in average 420 ± 70 nm; whereas, V2O5 nanoparticles showed a typical particle morphology with a size 36 ± 2 nm. Both V2O5 nanoparticles and nanofibers had dose-response effects on aminosugar, amino acid, fatty acid, carnitine, niacin and nucleotide metabolism. Differential effects of the particles and fibers included dibasic acid, glycosphingolipid and glycerophospholipid pathway associations with V2O5 nanoparticles, and cholesterol and sialic acid metabolism associations with V2O5 nanofibers. Examination by transmission electron microscopy provided evidence for mitochondrial stress and increased lysosome fusion by both nanomaterials, and these data were supported by effects on mitochondrial membrane potential and lysosomal activity. The results showed that non-cytotoxic exposures to V2O5 nanomaterials impact major metabolic pathways previously associated with human lung diseases and suggest that toxico-metabolomics may be useful to evaluate health risks from V2O5 nanomaterials.

Potential issues specific to cytotoxicity tests of cellulose nanofibrils.

Cellulose nanofibrils (also called cellulose nanofibers or nanofibrillated cellulose [CNFs]) are novel polymers derived from biomass with excellent physicochemical properties and various potential applications. However, the introduction of such new materials into the market requires thorough safety studies to be conducted. Recently, toxicity testing using cultured cells has attracted attention as a safety assessment that does not rely on experimental animals. This article reviews recent information regarding the cytotoxicity testing of CNFs and highlights the issues relevant to evaluating tests. In the literature, we found that a variety of cell lines and CNF exposure concentrations was evaluated. Furthermore, the results of cytotoxicity results tests differed and were not necessarily consistent. Numerous reports that we examined had not evaluated endotoxin/microbial contamination or the interaction of CNFs with the culture medium used in the tests. The following potential specific issues involved in CNF in vitro testing, were discussed: (1) endotoxin contamination, (2) microbial contamination, (3) adsorption of culture medium components to CNFs, and (4) changes in aggregation/agglomeration and dispersion states of CNFs resulting from culture medium components. In this review, the available measurement methods and solutions for these issues are also discussed. Addressing these points will lead to a better understanding of the cellular effects of CNFs and the development of safer CNFs.

Cytotoxicity evaluation of poly(ethylene) oxide nanofibre in MCF-7 breast cancer cell line.

Biocompatible polymers have received significant interest from researchers for their potential in diagnostic applications. This type of polymer can perform with an appropriate host response or carrier for a specific purpose. The current study aims to fabricate and characterise poly(ethylene) oxide (PEO) nanofibres with different concentrations for cytotoxicity evaluation in human breast cancer cell lines (MCF-7) and to get an optimal PEO nanofibre concentration (permissible limit) as a suitable polymer matrix or carrier with potential use in diagnostic applications. The fabrication of PEO nanofibres was done using electrospinning and was characterised by structure and morphology, surface roughness, chemical bonding and release profiles. The functional effects of PEO nanofibres were evaluated with MTS assay and colony formation assay in MCF-7 cells. The results showed that viscosity plays a vital role in synthesising a polymer solution in electrospinning for producing beadless nanofibrous mats ranging from 4.7 Pa·s to 77.7 Pa·s. As the PEO concentration increases, the nanofibre diameter and thickness will increase, but the surface roughness will be decreased. The average fibre diameter for 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 129 ± 70 nm, 185 ± 55 nm and 192 ± 53 nm, respectively. In addition, the fibre thickness for 4 wt% PEO, 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 269 ± 3 µm, 664 ± 4 µm, 758 ± 7 µm and 1329 ± 44 µm, respectively. Contrarily, the surface roughness for 4 wt% PEO, 5 wt% PEO, 6 wt% PEO and 7 wt% PEO nanofibres were 55.6 ± 9 nm, 42.8 ± 6 nm, 42.7 ± 7 nm and 36.6 ± 1 nm, respectively. PEO nanofibres showed the same burst release pattern and rate due to the same molecular weight of PEO with a stable release rate profile after 15 min. It also demonstrates that the percentage of PEO nanofibre release increased with the increasing PEO concentration due to the fibre diameter and thickness. The findings showed that all PEO nanofibres formulations were non-toxic to MCF-7 cells. It is suggested that 5 wt% PEO nanofibre exhibited non-cytotoxic characteristics by maintaining the cell viability from dose 0-1000 µg/ml and did not induce the number of colonies. Therefore, 5 wt% PEO nanofibre is the optimal nanofibre concentration and was suggested as a suitable base polymer matrix or carrier with potential use for diagnostic purposes. The findings in this study have demonstrated the influence of cell growth and viability, including the effects of PEO nanofibre formulations on cancer progress characteristics to achieve a permissible PEO nanofibre concentration limit that can be a benchmark in medical applications, particularly diagnostic applications.

Antibacterial Z-scheme ZnIn2S4/Ag2MoO4 composite photocatalytic nanofibers with enhanced photocatalytic performance under visible light.

Considering the biocompatibility of natural proteins and the strong photo-redox capability of Z-scheme heterojunctions, we fabricated Z-scheme ZnIn2S4/Ag2MoO4@Zein (Z ZA) photocatalytic membranes via electrospinning and in-situ precipitation for enrofloxacin (ENR) degradation. Z ZA exhibit a fiber structure wrapped with ZnIn2S4/Ag2MoO4 heterojunctions. Photocatalytic studies and various characterization results certified that the Z-scheme structure between ZnIn2S4 and Ag2MoO4 significantly increases the lifetime and separation efficiency of photogenerated carriers, which in turn enhances the photodegradation of ENR. The degradation rate of Z ZA-10 (ZnIn2S4/10 wt% Ag2MoO4@Zein) with the highest catalytic activity could reach 100% within 120 min compared with other samples. For ENR degradation, •O2- radicals were certified to be the primary active species by trapping experiments, and several possible conversion pathways of ENR in photocatalytic reactions were proposed. Furthermore, the antibacterial rates of Z ZA-20 (ZnIn2S4/20 wt% Ag2MoO4@Zein) against B. subtilis, P. aeruginosa, S. aureus, and E. coli could reach 90.09%, 89.78%, 84.34%, and 95.31%, respectively. Antibacterial evaluations and cytotoxicity assays demonstrated that Z ZA photocatalytic films had desirable antibacterial properties and low cytotoxicity, rendering them safe and effective for use in the treatment of antibiotic wastewater.

Effect of Surface Modification on the Pulmonary and Systemic Toxicity of Cellulose Nanofibrils.

Cellulose nanofibrils (CNFs) have emerged as sustainable options for a wide range of applications. However, the high aspect ratio and biopersistence of CNFs raise concerns about potential health effects. Here, we evaluated the in vivo pulmonary and systemic toxicity of unmodified (U-CNF), carboxymethylated (C-CNF), and TEMPO (2,2,6,6-tetramethyl-piperidin-1-oxyl)-oxidized (T-CNF) CNFs, fibrillated in the same way and administered to mice by repeated (3×) pharyngeal aspiration (14, 28, and 56 µg/mouse/aspiration). Toxic effects were assessed up to 90 days after the last administration. Some mice were treated with T-CNF samples spiked with lipopolysaccharide (LPS; 0.02-50 ng/mouse/aspiration) to assess the role of endotoxin contamination. The CNFs induced an acute inflammatory reaction that subsided within 90 days, except for T-CNF. At 90 days post-administration, an increased DNA damage was observed in bronchoalveolar lavage and hepatic cells after exposure to T-CNF and C-CNF, respectively. Besides, LPS contamination dose-dependently increased the hepatic genotoxic effects of T-CNF.

Nanofibrous materials affect the reaction of cytotoxicity assays.

Nanofibrous materials are widely investigated as a replacement for the extracellular matrix, the 3D foundation for cells in all tissues. However, as with every medical material, nanofibers too must pass all safety evaluations like in vitro cytotoxicity assays or in vivo animal tests. Our literature research showed that differences in results of widely used cytotoxicity assays applied to evaluate nanofibrous materials are poorly understood. To better explore this issue, we prepared three nanofibrous materials with similar physical properties made of poly-L-lactic acid, polyurethane, and polycaprolactone. We tested five metabolic cytotoxicity assays (MTT, XTT, CCK-8, alamarBlue, PrestoBlue) and obtained different viability results for the same nanofibrous materials. Further, the study revealed that nanofibrous materials affect the reaction of cytotoxicity assays. Considering the results of both described experiments, it is evident that validating all available cytotoxicity assays for nanofibrous materials and possibly other highly porous materials should be carefully planned and verified using an additional analytical tool, like scanning electron microscopy or, more preferably, confocal microscopy.

Surface functionalization and size modulate the formation of reactive oxygen species and genotoxic effects of cellulose nanofibrils.

BACKGROUND: Cellulose nanofibrils (CNFs) have emerged as a sustainable and environmentally friendly option for a broad range of applications. The fibrous nature and high biopersistence of CNFs call for a thorough toxicity assessment, but it is presently unclear which physico-chemical properties could play a role in determining the potential toxic response to CNF. Here, we assessed whether surface composition and size could modulate the genotoxicity of CNFs in human bronchial epithelial BEAS-2B cells. We examined three size fractions (fine, medium and coarse) of four CNFs with different surface chemistry: unmodified (U-CNF) and functionalized with 2,2,6,6-tetramethyl-piperidin-1-oxyl (TEMPO) (T-CNF), carboxymethyl (C-CNF) and epoxypropyltrimethylammonium chloride (EPTMAC) (E-CNF). In addition, the source fibre was also evaluated as a non-nanosized material. RESULTS: The presence of the surface charged groups in the functionalized CNF samples resulted in higher amounts of individual nanofibrils and less aggregation compared with the U-CNF. T-CNF was the most homogenous, in agreement with its high surface group density. However, the colloidal stability of all the CNF samples dropped when dispersed in cell culture medium, especially in the case of T-CNF. CNF was internalized by a minority of BEAS-2B cells. No remarkable cytotoxic effects were induced by any of the cellulosic materials. All cellulosic materials, except the medium fraction of U-CNF, induced a dose-dependent intracellular formation of reactive oxygen species (ROS). The fine fraction of E-CNF, which induced DNA damage (measured by the comet assay) and chromosome damage (measured by the micronucleus assay), and the coarse fraction of C-CNF, which produced chromosome damage, also showed the most effective induction of ROS in their respective size fractions. CONCLUSIONS: Surface chemistry and size modulate the in vitro intracellular ROS formation and the induction of genotoxic effects by fibrillated celluloses. One cationic (fine E-CNF) and one anionic (coarse C-CNF) CNF showed primary genotoxic effects, possibly partly through ROS generation. However, the conclusions cannot be generalized to all types of CNFs, as the synthesis process and the dispersion method used for testing affect their physico-chemical properties and, hence, their toxic effects.

Antibacterial, cytotoxicity and biodegradability studies of polycaprolactone nanofibers holding green synthesized Ag nanoparticles using atropa belladonna extract.

Atropa belladonna is one of the herbs used to treat wounds and prevent inflammation. This study provides a scientific assessment for the wound healing potential of biodegradable nanofibers containing Ag nanoparticles encapsulated with atropa belladonna extract (eAgNPs). Ultraviolet-visible (UV-vis) spectroscopy was used to observe the localized surface plasmon resonance (LSPR) band of AgNPs synthesized from atropa belladonna extract prepared under different conditions. Polycaprolactone (PCL) nanofibers with eAgNPs were fabricated using the electrospinning technique. The distribution of AgNPs and eAgNPs and the size of nanofibers were characterized with scanning and transmission electron microscopy (SEM, TEM) before and after degradation at the end of 18 weeks. Fourier transform infrared (FTIR) spectroscopy showed the surface interactivity between AgNPs, atropa belladonna extract and PCL nanofibers and also approved the modification of PCL nanofibers with eAgNPs. X-ray diffraction analysis (XRD) defined the formation of the crystalline AgNPs and appreciated the orientation of the nanofibers. Results of tension tests revealed that modification of PCL nanofibers with pure AgNPs and eAgNPs significantly increased strength and tensile modulus. Due to the hydrophobic nature of PCL, modification with pure AgNPs and eAgNPs slightly reduced its hydrophobicity. Biodegradation tests of PCL nanofibers with eAgNPs exhibited a higher degradation rate than neat PCL nanofibers. In vitro MTT results revealed that eAgNPs doped PCL samples have better cell viability than AgNPs doped and neat PCL nanofibers. Owing to their antibacterial properties, biodegradation rates, low cytotoxicity, mechanical and surface morphologic properties of AgNPs modified PCL nanofibers containing atropa belladonna are considered to have a great potential for skin regeneration.

Nematic Templated Complex Nanofiber Structures by Projection Display.

Oriented arrays of nanofibers are ubiquitous in nature and have been widely used in recreation of the biological functions such as bone and muscle tissue regenerations. However, it remains a challenge to produce nanofiber arrays with a complex organization by using current fabrication techniques such as electrospinning and extrusion. In this work, we propose a method to fabricate the complex organization of nanofiber structures templated by a spatially varying ordered liquid crystal host, which follows the pattern produced by a maskless projection display system. By programming the synchronization of the rotated polarizer and projected segments with different shapes, various configurations of nanofiber organization ranging from a single to two-dimensional lattice of arbitrary topological defects are created in a deterministic manner. The nanofiber arrays can effectively guide and promote neurite outgrowth. The application of nanofibers with arced profiles and topological defects on neural tissue organization is also demonstrated. This finding, combined with the versatility and programmability of nanofiber structures, suggests that they will help solve challenges in nerve repair, neural regeneration, and other related tissue engineering fields.

Histopathology of the broad class of carbon nanotubes and nanofibers used or produced in U.S. facilities in a murine model.

BACKGROUND: Multi-walled carbon nanotubes and nanofibers (CNT/F) have been previously investigated for their potential toxicities; however, comparative studies of the broad material class are lacking, especially those with a larger diameter. Additionally, computational modeling correlating physicochemical characteristics and toxicity outcomes have been infrequently employed, and it is unclear if all CNT/F confer similar toxicity, including histopathology changes such as pulmonary fibrosis. Male C57BL/6 mice were exposed to 40 µg of one of nine CNT/F (MW #1-7 and CNF #1-2) commonly found in exposure assessment studies of U.S. facilities with diameters ranging from 6 to 150 nm. Human fibroblasts (0-20 µg/ml) were used to assess the predictive value of in vitro to in vivo modeling systems. RESULTS: All materials induced histopathology changes, although the types and magnitude of the changes varied. In general, the larger diameter MWs (MW #5-7, including Mitsui-7) and CNF #1 induced greater histopathology changes compared to MW #1 and #3 while MW #4 and CNF #2 were intermediate in effect. Differences in individual alveolar or bronchiolar outcomes and severity correlated with physical dimensions and how the materials agglomerated. Human fibroblast monocultures were found to be insufficient to fully replicate in vivo fibrosis outcomes suggesting in vitro predictive potential depends upon more advanced cell culture in vitro models. Pleural penetrations were observed more consistently in CNT/F with larger lengths and diameters. CONCLUSION: Physicochemical characteristics, notably nominal CNT/F dimension and agglomerate size, predicted histopathologic changes and enabled grouping of materials by their toxicity profiles. Particles of greater nominal tube length were generally associated with increased severity of histopathology outcomes. Larger particle lengths and agglomerates were associated with more severe bronchi/bronchiolar outcomes. Spherical agglomerated particles of smaller nominal tube dimension were linked to granulomatous inflammation while a mixture of smaller and larger dimensional CNT/F resulted in more severe alveolar injury.