Nanocomposites as Advanced Materials for Aerospace Industry

Polymer nanocomposites, consisting of nanoparticles dispersed in polymer matrix, have gained interest due to the attractive properties of nanostructured fillers, as carbon nanotubes and layered silicates. Low volume additions (1- 5%) of nanoparticles provide properties enhancements comparable to those achieved by conventional loadings (15- 40%) of traditional fillers.Structural nanocomposites represent reinforcement structures based on carbon or glass fibers embedded into polymeric matrix modified with nanofillers.Structural composites are the most important application of nanaocomposites, in aerospace field, as, laminates and sandwich structures. Also, they can by used as anti-lightning, anti-radar protectors and paints. The paper presents the effects of sonic dispersion of carbon nanotubes and montmorrilonite on the mechanical, electrical, rheological and trybological properties of epoxy polymers and laminated composites, with carbon or glass fiber reinforcement, with nanoadditivated epoxy matrix. One significant observation is that nanoclay contents higher than 2% wt generate an increase of the resin viscosity, from 1500 to 50000- 100000 cP, making the matrix impossible to use in high performance composites.Also, carbon nanotubes provide the resin important electrical properties, passing from dielectric to semi- conductive class. These effects have also been observed for fiber reinforced composites.Contrarily to some opinions in literature, the results of carbon nanotubes or nanoclays addition on the mechanical characteristics of glass or carbon fiber composites seem to be rather low

Stability studies of combined ear drops with ciprofloxacin, dexametazone, loratadine and essential basil oil

Catedra de chimie farmaceutică și toxicologică, Universitatea de Stat de Medicină și Farmacie „Nicolae Testemițanu” din Republica MoldovaIntroducere. Stabilitatea unui medicament reprezintă, alături de eficacitate, puritate și inocuitate, un factor important în asigurarea calităţii acestuia. Pentru formele farmaceutice combinate, cu conținut de 2-3 principii activi procesul de degradare poate fi accelerat la depozitare, în special sub influența factorilor de stres. Scopul studiului. Determinarea stabilității picăturilor auriculare combinate cu ciprofloxacină, dexametazonă, loratadină și ulei volatil de busuioc. Material și metode. Depozitare în condiții de stres oxidativ, alcalin, acid, termic, umiditate excesivă, iradiere UV; vâscozimetrul rotațional MultiVisc Rheometer, Fungilab; pH-metrul inoLab 7110. HPLC: Shimadzu LC cu detector UV-VIS, coloana ZORBAX Eclipse XDB- C18, 5 μm, 250mmx4,6cm, 40°C, 1,0mL/min, 20μL; faza mobilă: 0,1% H3PO4-ACN(65:35)-MeOH(80:20) la pH 3,0 cu trietilamină. Picături auriculare serii pilot de laborator; placebo; peroxid de hidrogen; HCl 0,1 mol/l; NaOH 0,1 mol/l. Rezultate. În cromatogramele soluţiilor stres nu au existat picuri corespunzătoare produselor de degradare care să interfere cu picurile substanțelor active. Stresul UV determină o degradare majoră a ciprofloxacinei. Dexametazona degradează la umiditate, iar loratadina este sensibilă în mediu alcalin la majorarea temperaturii. Conținuturile de principii active la depozitare în timp real timp de 6 luni s-au încadrat în limitele admisibile. Valorile pH-ului și a vâscozității nu s-au modificat (4,5- 5,0 și 3080,6cP*102). Concluzii. Au fost stabiliți factorii de stres care influențează stabilitatea picăturilor auriculare combinate. La păstrarea în timp real după 6 luni nu au fost detectate modificări majore ale concentrațiile principiilor active. Studiile de stabilitate continuă.Introduction. The stability of a drug , as well as efficacy, purity and safety is an important factor in ensuring its quality. The degradation process of the coated pharmaceutical forms, containing 2-3 active substances, can be accelerated, especially under the influence of stress factors. The aim of the study. Determination of stability of combined ear drops with ciprofloxacin, dexamethasone, loratadine and volatile basil oil. Material and methods. Storage under stressful conditions: oxidative, alkaline, acidic, thermic, excessive humidity, UV irradiation; rotational viscometer MultiVisc Rheometer, Fungilab; pH-meter inoLab 7110. HPLC: Shimadzu LC with UV-VIS detection, ZORBAX Eclipse XDB-C18 column, 5 μm with dimensions 250 mm x 4,6 cm, 40°C, mobile phase flow rate 1,0 mL/min, 20 μL; mobile phase: 0,1% H3PO4-ACN(65:35)-MeOH(80:20) at pH 3.0 with triethylamine. Laboratory ear drops; placebo; hydrogen peroxide; HCl 0,1 mol/l; NaOH 0,1 mol/l. Results. In the chromatograms of stress solutions, there were no peaks of degradation products, that would interfere with the peaks of active substances. UV stress causes major degradation of ciprofloxacin. Dexamethasone degrades to moisture, and loratadine is sensitive to alkaline at high temperature. The contents of active principles in real time-storage for 6 months, were within the allowed limits. The values of pH and viscosity were not modified (4,5-5,0 and 3080,6 cP*102). Conclusions. Stress factors that influence the stability of the combined ear drops were established. No major changes were detected in the concentrations of the active principles after 6 months of storage. Stability studies continue

Nanofilled EPDM composite for aerospace applications

O-rings are designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface. The joint may be static, or (in a few circumstances) may have relative motion between parts and O-ring (rotating pump shafts and hydraulic cylinders, for example). Starting from the functionality of O-rings, the component materials can be described. Synthetic rubber, EPDM (ethylene-propylene diene monomer) is one of the most popular, versatile and long-lasting elastomeric material that is suitable for a wide range of applications, such as those in the aerospace domain, presenting a good behavior in extreme temperatures and high ozone resistance. The paper presents an experimental study using EPDM − Nordel 4760, butylic rubber (IIR)− Butyl 268 and clorobutylic rubber (Cl-IIR) − Chlorobutyl HT 1066 and a nanometric agent. As the targeted application of these materials is a specific one for extreme temperatures conditions, a testing matrix was developed, aimed to qualify their technical performance. The mechanical resistance of elastomers recommends the quality of its nanomodified version through superior performance. The structure of the analyzed materials proved to be unaltered when subjected to low temperatures, exhibiting good mechanical performance suitable for the targeted application

Assessment of skin sensitization properties of few-layer graphene and graphene oxide through the Local Lymph Node Assay (OECD TG 442B)

: Skin contact is one of the most common exposure routes to graphene-based materials (GBMs) during their small-scale and industrial production or their use in technological applications. Nevertheless, toxic effects in humans by cutaneous exposure to GBMs remain largely unexplored, despite skin contact to other related materials has been associated with adverse effects. Hence, this in vivo study was carried out to evaluate the cutaneous effects of two GBMs, focusing on skin sensitization as a possible adverse outcome. Skin sensitization by few-layer graphene (FLG) and graphene oxide (GO) was evaluated following the Organization for Economic Cooperation and Development (OECD) guideline 442B (Local Lymph Node Assay; LLNA) measuring the proliferation of auricular lymph node cells during the induction phase of skin sensitization. Groups of four female CBA/JN mice (8-12 weeks) were daily exposed to FLG or GO through the dorsal skin of each ear (0.4-40 mg/mL, equal to 0.01-1.00 mg/ear) for 3 consecutive days, and proliferation of auricular lymph node cells was evaluated 3 days after the last treatment. During this period, no clinical signs of toxicity and no alterations in body weight and food or water consumptions were observed. In addition, no ear erythema or edema were recorded as signs of irritation or inflammation. Bromo-deoxyuridine (BrdU) incorporation in proliferating lymphocytes from ear lymph nodes (stimulation indexes <1.6) and the histological analysis of ear tissues excluded sensitizing or irritant properties of these materials, while myeloperoxidase activity in ear biopsies confirmed no inflammatory cells infiltrate. On the whole, this study indicates the absence of sensitization and irritant potential of FLG and GO

Skin irritation potential of graphene-based materials using a non-animal test

Graphene related materials, if prepared with non-irritant exfoliation agents, do not induce skin irritation on a 3D model of human epidermis, following the OECD guideline 439

Role of Oxidative Stress Mediated by Glutathione-S-transferase in Thiopurines' Toxic Effects

Azathioprine (AZA), 6-mercaptopurine (6-MP), and 6-thioguanine (6-TG) are antimetabolite drugs, widely used as immunosuppressants and anticancer agents. Despite their proven efficacy, a high incidence of toxic effects in patients during standard-dose therapy is recorded. The aim of this study is to explain, from a mechanistic point of view, the clinical evidence showing a significant role of glutathione-S-transferase (GST)-M1 genotype on AZA toxicity in inflammatory bowel disease patients. To this aim, the human nontumor IHH and HCEC cell lines were chosen as predictive models of the hepatic and intestinal tissues, respectively. AZA, but not 6-MP and 6-TG, induced a concentration-dependent superoxide anion production that seemed dependent on GSH depletion. N-Acetylcysteine reduced the AZA antiproliferative effect in both cell lines, and GST-M1 overexpression increased both superoxide anion production and cytotoxicity, especially in transfected HCEC cells. In this study, an in vitro model to study thiopurines' metabolism has been set up and helped us to demonstrate, for the first time, a clear role of GST-M1 in modulating AZA cytotoxicity, with a close dependency on superoxide anion production. These results provide the molecular basis to shed light on the clinical evidence suggesting a role of GST-M1 genotype in influencing the toxic effects of AZA treatment

Keratinocytes are capable of selectively sensing low amounts of graphene-based materials: Implications for cutaneous applications

Abstract Skin provides the first interface between body and environment, representing one of the most feasible exposure routes to graphene-based materials (GBMs). However, interactions of GBMs with the skin are poorly understood. In particular, low-concentration effects have not been investigated. Here we explored the ability of endotoxin-free, few-layer graphene (FLG) and dehydrated graphene oxide (d-GO) to initiate an inflammatory response at the cutaneous level by using human HaCaT keratinocytes. HaCaT cell exposure to low concentrations (0.01–1.0 μg/mL) of FLG or d-GO did not affect cell viability. FLG triggered the secretion of pro-inflammatory tumor necrosis factor-α (TNF-α), interleukin (IL)-1α, and IL-6, while d-GO, and to a lesser extent FLG, prompted IL-8 (CXCL8) production. However, conditioned medium from HaCaT cells exposed to FLG or d-GO had no effect on THP-1 monocyte activation. Moreover, co-culture experiments did not show any effect of FLG- or d-GO-treated HaCaT cells on THP-1 cell migration. These results suggest that while GBMs are able to initiate an inflammatory response in keratinocytes, this does not necessarily lead to activation of monocytes. The present findings are relevant for potential dermal exposures to GBMs in occupational settings as well as the use of GBMs for cutaneous applications such as in wearable sensors

Hazard characterization of graphene-based nanomaterials in energy production and storage (GrapHazard)

This publication is the final report of the research project “Hazard characterization of graphene-based nanomaterials in energy production and storage (GrapHazard)”, funded by the Finnish Work Environmental Fund, the Italian National Institute for Insurance against Accidents at Work (INAIL), the Finnish Institute of Occupational Health, and the University of Trieste in the frame of the SAF€RA 2020 program. The report summarizes the findings of the toxicological assessment of different types of graphene-based materials by using an in vitro lung system to investigate the involved mechanisms of action and how different key physicochemical properties of the materials can modulate the toxic response. In addition, recommendations for a safe use of graphene-based materials in occupational settings are provided

Graphene and graphene oxide induce ROS production in human HaCaT skin keratinocytes: The role of xanthine oxidase and NADH dehydrogenase

The extraordinary physicochemical properties of graphene-based nanomaterials (GBNs) make them promising tools in nanotechnology and biomedicine. Considering the skin contact as one of the most feasible exposure routes to GBNs, the mechanism of toxicity of two GBNs (few-layer-graphene, FLG, and graphene oxide, GO) towards human HaCaT skin keratinocytes was investigated. Both materials induced a significant mitochondrial membrane depolarization: 72 h cell exposure to 100 \u3bcg mL 12 1 FLG or GO increased mitochondrial depolarization by 44% and 56%, respectively, while the positive control valinomycin (0.1 \u3bcg mL 121) increased mitochondrial depolarization by 48%. Since the effect was not prevented by cyclosporine-A, it appears to be unrelated to mitochondrial transition pore opening. By contrast, it seems to be mediated by reactive oxygen species (ROS) production: FLG and GO induced time- and concentration- dependent cellular ROS production, significant already at the concentration of 0.4 \u3bcg mL 121 after 24 h exposure. Among a panel of specific inhibitors of the major ROS-producing enzymes, diphenyliodonium, rotenone and allopurinol significantly reverted or even abolished FLG- or GO-induced ROS production. Intriguingly, the same inhibitors also significantly reduced FLG- or GO-induced mitochondrial depolarization and cytotoxicity. This study shows that FLG and GO induce a cytotoxic effect due to a sustained mitochondrial depolarization. This seems to be mediated by a significant cellular ROS production, caused by the activation of flavoprotein-based oxidative enzymes, such as NADH dehydrogenase and xanthine oxidase

Differential cytotoxic effects of graphene and graphene oxide on skin keratinocytes

mpressive properties make graphene-based materials (GBMs) promising tools for nanoelectronics and biomedicine. However, safety concerns need to be cleared before mass production of GBMs starts. As skin, together with lungs, displays the highest exposure to GBMs, it is of fundamental importance to understand what happens when GBMs get in contact with skin cells. The present study was carried out on HaCaT keratinocytes, an in vitro model of skin toxicity, on which the effects of four GBMs were evaluated: A few layer graphene, prepared by ball-milling treatment (FLG), and three samples of graphene oxide (GOs, a research-grade GO1, and two commercial GOs, GO2 and GO3). Even though no significant effects were observed after 24 h, after 72 h the less oxidized compound (FLG) was the less cytotoxic, inducing mitochondrial and plasma-membrane damages with EC 50 s of 62.8 \u3bcg/mL (WST-8 assay) and 45.5 \u3bcg/mL (propidium iodide uptake), respectively. By contrast, the largest and most oxidized compound, GO3, was the most cytotoxic, inducing mitochondrial and plasma-membrane damages with EC 50 s of 5.4 and 2.9 \u3bcg/mL, respectively. These results suggest that only high concentrations and long exposure times to FLG and GOs could impair mitochondrial activity associated with plasma membrane damage, suggesting low cytotoxic effects at the skin level