Evaluation of the Skin Sensitization Potential of Carbon Nanotubes Using Alternative In Vitro and In Vivo Assays

In vitro assessment of skin irritation and corrosion properties of graphene-related materials on a 3D epidermis

The increasing use of graphene-related materials (GRMs) in many technological applications, ranging from electronics to biomedicine, needs a careful evaluation of their impact on human health. Skin contact can be considered one of the most relevant exposure routes to GRMs. Hence, this study is focused on two main adverse outcomes at the skin level, irritation and corrosion, assessed following two specific Test Guidelines (TGs) defined by the Organization for Economic Co-operation and Development (OECD) (439 and 431, respectively) that use an in vitro 3D reconstructed human epidermis (RhE) model. After the evaluation of their suitability to test a large panel of powdered GRMs, it was found that the latter were not irritants or corrosive. Only GRMs prepared with irritant surfactants, not sufficiently removed, reduced RhE viability at levels lower than those predicting skin irritation (≤50%, after 42 min exposure followed by 42 h recovery), but not at levels lower than those predicting corrosion (<50%, after 3 min exposure or <15% after 1 h exposure). As an additional readout, a hierarchical clustering analysis on a panel of inflammatory mediators (interleukins: IL-1α, IL-1β, IL-6, and IL-18; tumor necrosis factor-α and prostaglandin E2) released by RhE exposed to these materials supported the lack of irritant and pro-inflammatory properties. Overall, these results demonstrate that both TGs are useful in assessing GRMs for their irritant or corrosion potential, and that the tested materials did not cause these adverse effects at the skin level. Only GRMs prepared using toxic surfactants, not adequately removed, turned out to be skin irritants.

Waterless Dyeing and In Vitro Toxicological Properties of Biocolorants from Cortinarius sanguineus

As a part of an ongoing interest in identifying environmentally friendly alternatives to synthetic dyes and in using liquid CO2 as a waterless medium for applying the resulting colorants to textiles, our attention turned to yellow-to-red biocolorants produced by Cortinarius sanguineus fungus. The three principal target anthraquinone colorants (emodin, dermocybin, and dermorubin) were isolated from the fungal bodies using a liquid-liquid separation method and characterized using 700 MHz NMR and high-resolution mass spectral analyses. Following structure confirmations, the three colorants were examined for dyeing synthetic polyester (PET) textile fibers in supercritical CO2. We found that all three biocolorants were suitable for dyeing PET fibers using this technology, and our attention then turned to determining their toxicological properties. As emodin has shown mutagenic potential in previous studies, we concentrated our present toxicity studies on dermocybin and dermorubin. Both colorants were non-mutagenic, presented low cellular toxicity, and did not induce skin sensitization. Taken together, our results indicate that dermocybin and dermorubin possess the technical and toxicological properties needed for consideration as synthetic dye alternatives under conditions that are free of wastewater production.

Application of ARE-reporter systems in drug discovery and safety assessment

The human body is continuously exposed to xenobiotics and internal or external oxidants. The health risk assessment of exogenous chemicals remains a complex and challenging issue. Alternative toxicological test methods have become an essential strategy for health risk assessment. As a core regulator of constitutive and inducible expression of antioxidant response element (ARE)-dependent genes, nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in maintaining cellular redox homeostasis. Consistent with the properties of Nrf2-mediated antioxidant response, Nrf2-ARE activity is a direct indicator of oxidative stress and thus has been used to identify and characterize oxidative stressors and redox modulators. To screen and distinguish chemicals or environmental insults that affect the cellular antioxidant activity and/or induce oxidative stress, various in vitro cell models expressing distinct ARE reporters with high-throughput and high-content properties have been developed. These ARE-reporter systems are currently widely applied in drug discovery and safety assessment. In the present review, we provide an overview of the basic structures and applications of various ARE-reporter systems employed for discovering Nrf2-ARE modulators and characterizing oxidative stressors.

Nanomaterials-induced toxicity on cardiac myocytes and tissues, and emerging toxicity assessment techniques

The extensive production and use of nanomaterials have resulted in the continuous release of nano-sized particles into the environment, and the health risks caused by exposure to these nanomaterials in the occupational population and the general population cannot be ignored. Studies have found that particle exposure is closely related to cardiovascular disease. In addition, there have been many reports that nanomaterials can enter the heart tissue, accumulate and then cause damage. Therefore, in the present article, literature related to nanomaterials-induced cardiotoxicity in recent years was collected from the PubMed database, and then organized and summarized to form a review. This article mainly discusses heart damage caused by nanomaterials from the following three aspects: Firstly, we summarize the research 8 carbon nanotubes, etc. Secondly, we discuss in depth the possible underlying mechanism of the damage to the heart caused by nanoparticles. Oxidative stress damage, mitochondrial damage, inflammation and apoptosis have been found to be key factors. Finally, we summarize the current research models used to evaluate the cardiotoxicity of nanomaterials, highlight reliable emerging technologies and in vitro models that have been used for toxicity evaluation of environmental pollutants in recent years, and indicate their application prospects.

Prediction of Skin Sensitization Potential of Silver and Zinc Oxide Nanoparticles Through the Human Cell Line Activation Test

The development of nanotechnology has propagated the use of nanoparticles (NPs) in various fields including industry, agriculture, engineering, cosmetics, or medicine. The use of nanoparticles in cosmetics and dermal-based products is increasing owing to their higher surface area and unique physiochemical properties. Silver (Ag) NPs' excellent broad-spectrum antibacterial property and zinc oxide (ZnO) NPs' ability to confer better ultraviolet (UV) protection has led to their maximal use in cosmetics and dermal products. While the consideration for use of nanoparticles is increasing, concerns have been raised regarding their potential negative impacts. Although used in various dermal products, Ag and ZnO NPs' skin sensitization (SS) potential has not been well-investigated using in vitro alternative test methods. The human Cell Line Activation Test (h-CLAT) that evaluates the ability of chemicals to upregulate the expression of CD86 and CD54 in THP-1 cell line was used to assess the skin sensitizing potential of these NPs. The h-CLAT assay was conducted following OECD TG 442E. NPs inducing relative fluorescence intensity of CD86 ≥ 150% and/or CD54 ≥ 200% in at least two out of three independent runs were predicted to be positive. Thus, Ag (20, 50, and 80 nm) NPs and ZnO NPs were all predicted to be positive in terms of SS possibility using the h-CLAT prediction model. Although further confirmatory tests addressing other key events (KEs) of SS adverse outcome pathway (AOP) should be carried out, this study gave an insight into the need for cautious use of Ag and ZnO NPs based skincare or dermal products owing to their probable skin sensitizing potency.

Skin Sensitization Evaluation of Carbon-Based Graphene Nanoplatelets

Graphene nanoplatelets (GNPs) are one of the major types of carbon based nanomaterials that have different industrial and biomedical applications. There is a risk of exposure to GNP material in individuals involved in their large-scale production and in individuals who use products containing GNPs. Determining the exact toxicity of GNP nanomaterials is a very important agenda. This research aimed to evaluate the skin sensitization potentials induced by GNPs using two types of alternative to animal testing. We analyzed the physicochemical characteristics of the test material by selecting a graphene nanomaterial with a nano-size on one side. Thereafter, we evaluated the skin sensitization effect using an in vitro and an in vivo alternative test method, respectively. As a result, we found that GNPs do not induce skin sensitization. In addition, it was observed that the administration of GNPs did not induce cytotoxicity and skin toxicity. This is the first report of skin sensitization as a result of GNPs obtained using alternative test methods. These results suggest that GNP materials do not cause skin sensitization, and these assays may be useful in evaluating the skin sensitization of some nanomaterials.