Hazard characterization of graphene nanomaterials in the frame of their food risk assessment: A review

Different applications have been suggested for graphene nanomaterials (GFNs) in the food and feed chain. However, it is necessary to perform a risk assessment before they become market-ready, and when consumer exposure is demonstrated. For this purpose, the European Food Safety Authority (EFSA) has published a guidance that has been recently updated. In this sense, the aim of this study is to identify and characterise toxicological hazards related to GFNs after oral exposure. Thus, existing scientific literature in relation to in vitro degradation studies, in vitro and in vivo genotoxicity, toxicokinetics data, in vivo oral studies, and other in-depth studies such as effects on the microbiome has been revised. The obtained results showed that the investigations performed up to now did not follow internationally agreed-upon test guidelines. Moreover, GFNs seemed to resist gastrointestinal digestion and were able to be absorbed, distributed, and excreted, inducing toxic effects at different levels, including genotoxicity. Also, dose has an important role as it has been reported that low doses are more toxic than high doses because GFNs tend to aggregate in the digestive system, changing the internal exposure scenario. Thus, further studies including a thorough toxicological evaluation are required to protect consumer's safety.Junta de Andalucía US-1259106, P18-RT-199

In Vitro Toxicity of Reduced Graphene Oxide in the Hepato-gastrointestinal System: a Review

Recientemente, el interés por el óxido de grafeno reducido (OGr) se ha visto incrementado debido a sus numerosas propiedades. Considerando que el uso de estos materiales ha aumentado en los últimos años, esto puede suponer un mayor riesgo para la salud humana. La vía oral es una de las principales rutas de exposición, por lo que es importante determinar cuáles son los principales efectos tóxicos sobre el sistema hepato-gastrointestinal. En este sentido, el objetivo de este estudio es revisar los posibles efectos tóxicos in vitro del OGr en las principales líneas celulares de los sistemas intestinal y hepático. Los resultados muestran que el OGr podría ser tóxico en modelos in vitro; sin embargo, son necesarios un mayor número de investigaciones para determinar los posibles mecanismos de toxicidad.Recently, the interest in reduced graphene oxide (rGO) has increased due to its myriad of properties. Considering the higher use of this material in the last years, it is important to evaluate its potential risk on human health. The oral pathway is one of the main exposure routes, therefore, it is important to assess its toxic effects on the hepato- gastrointestinal system. In this sense, the aim of this study is to review the potential in vitro toxic effects of rGO on gastrointestinal and liver cell lines. The results obtained showed that rGO could be toxic in in vitro models; however, further toxicological studies are required to define its mechanisms of toxicity.Fondo Europeo de Desarrollo Regional US-1259106Junta de Andalucía P18-RT-199

In Vitro Safety Assessment of Reduced Graphene Oxide in Human Monocytes and T Cells.

Considering the increase in the use of graphene derivatives in different fields, the environmental and human exposure to these materials is likely, and the potential consequences are not fully elucidated. This study is focused on the human immune system, as this plays a key role in the organism's homeostasis. In this sense, the cytotoxicity response of reduced graphene oxide (rGO) was investigated in monocytes (THP-1) and human T cells (Jurkat). A mean effective concentration (EC50-24 h) of 121.45 ± 11.39 μg/mL and 207.51 ± 21.67 μg/mL for cytotoxicity was obtained in THP-1 and Jurkat cells, respectively. rGO decreased THP-1 monocytes differentiation at the highest concentration after 48 h of exposure. Regarding the inflammatory response at genetic level, rGO upregulated IL-6 in THP-1 and all cytokines tested in Jurkat cells after 4 h of exposure. At 24 h, IL-6 upregulation was maintained, and a significant decrease of TNF-α gene expression was observed in THP-1 cells. Moreover, TNF-α, and INF-γ upregulation were maintained in Jurkat cells. With respect to the apoptosis/necrosis, gene expression was not altered in THP-1 cells, but a down regulation of BAX and BCL-2 was observed in Jurkat cells after 4 h of exposure. These genes showed values closer to negative control after 24 h. Finally, rGO did not trigger a significant release of any cytokine at any exposure time assayed. In conclusion, our data contributes to the risk assessment of this material and suggest that rGO has an impact on the immune system whose final consequences should be further investigated.Fondo Europeo de Desarrollo Regional US-1259106Junta de Andalucía P18-RT-199

Immunomodulatory Effects of Cylindrospermopsin in Human T Cells and Monocytes

Cylindrospermopsin (CYN) is a cyanotoxin with an increasing occurrence, and therefore it is important to elucidate its toxicity profile. CYN has been classified as a cytotoxin, although the scientific literature has already revealed that it affects a wide range of organs and systems. However, research on its potential immunotoxicity is still limited. Thus, this study aimed to evaluate the impact of CYN on two human cell lines representative of the immune system: THP-1 (monocytes) and Jurkat (lymphocytes). CYN reduced cell viability, leading to mean effective concentrations (EC50 24 h) of 6.00 ± 1.04 µM and 5.20 ± 1.20 µM for THP-1 and Jurkat cells, respectively, and induced cell death mainly by apoptosis in both experimental models. Moreover, CYN decreased the differentiation of monocytes to macrophages after 48 h of exposure. In addition, an up-regulation of the mRNA expression of different cytokines, such as interleukin (IL) 2, IL-8, tumor necrosis factor-alpha (TNF-α) and interferon-gamma (INF-γ), was also observed mainly after 24 h exposure in both cell lines. However, only an increase in TNF-α in THP-1 supernatants was observed by ELISA. Overall, these results suggest the immunomodulatory activity of CYN in vitro. Therefore, further research is required to evaluate the impact of CYN on the human immune system.Ministerio de Ciencia e Innovación PID 2019-104890RB-I0, PRE 2020-094412Acciones Marie Sklodowska-Curie 823860Universidad de Sevilla CITIUS–VIIPPIT-2023-I.

Genotoxicity evaluation of graphene derivatives by a battery of in vitro assays

The interest of graphene materials has increased markedly in the recent years for their promising applications in many fields as food packing. These new applications have caused some concern regarding their safety for consumers since the intake of these materials may increase. In this sense, a battery of in vitro test is required before its use as a food contact material. Then, the aim of this study was to assess the potential mutagenicity and genotoxicity of graphene oxide (GO) and reduced-graphene oxide (rGO) following the recommendations of the European Food Safety Authority (EFSA). Thus, the mouse lymphoma assay (MLA) and the micronucleus test (MN) were performed in L5178YTk ± cells, and the Caco-2 cells were used for the standard and modified comet assays. The results indicated that GO (0–250 μg/mL) was not mutagenic in the MLA. However, rGO revealed mutagenic activity from 250 μg/mL and 125 μg/mL after 4h and 24h of exposure, respectively. In the MN test, negative results were obtained for both compounds at the concentrations assayed (0–250 μg/mL) for GO/rGO. Moreover, no DNA strand breaks, or oxidative DNA damage were detected in Caco-2 cells exposed to GO (0–250 μg/mL) and rGO (0–176.3 μg/mL for 24h and 0–166.5 μg/mL for 48h). Considering the mutagenic potential of rGO observed further investigation is needed to describe its toxic profile

Impact of Gastrointestinal Digestion In Vitro Procedure on the Characterization and Cytotoxicity of Reduced Graphene Oxide

The growing interest in graphene derivatives is a result of their variety of applications in many fields. Due to their use, the oral route could be a potential way of entrance for the general population. This work assesses the biotransformation of reduced graphene oxide (rGO) after an in vitro digestion procedure (mouth, gastric, intestinal, and colon digestion), and its toxic effects in different cell models (HepG2, Caco-2, and 3D intestinal model). The characterization of rGO digestas evidenced the agglomeration of samples during the in vitro gastrointestinal (g.i.) digestion. Internalization of rGO was only evident in Caco-2 cells exposed to the colonic phase and no cellular defects were observed. Digestas of rGO did not produce remarkable cytotoxicity in any of the experimental models employed at the tested concentrations (up to 200 µg/mL), neither an inflammatory response. Undigested rGO has shown cytotoxic effects in Caco-2 cells, therefore these results suggest that the digestion process could prevent the systemic toxic effects of rGO. However, additional studies are necessary to clarify the interaction of rGO with the g.i. tract and its biocompatibility profile.Fondo Europeo de Desarrollo Regional US-1259106, P18-RT1993Junta de Andalucía POSTDOC_21_0013

Scientific Dissemination Conference: Contributions of Toxicology in Substance Safety Research and for Society

Las “Jornadas de divulgación científica: Aportaciones de la Toxicología en la investigación de la seguridad de las sustancias y para la sociedad” se celebraron el 19 de mayo de 2023 en la Facultad de Farmacia de la Universidad de Sevilla, gracias a una Ayuda recibida por el VII Plan Propio de la Universidad de Sevilla (VII PPIT-US) para actividades de divulgación científica. El objetivo fue divulgar entre nuestros alumnos los conocimientos científicos por parte de personal docente e investigador altamente cualificado, y también dar a conocer a la sociedad en general el trabajo de investigación científica de alto nivel que se está realizando en la US. La actividad iba dirigida a los alumnos de las asignaturas de “Toxicología”, “Quimioinformática, Investigación e Historia de la Farmacia”, “Laboratorio de Farmacia” (del Grado en Farmacia, Grado en Óptica y Optometría, y Doble Grado en Farmacia y Óptica y Optometría), y las asignaturas de “Toxicología de las Drogas de Abuso” o “Introducción a las Ciencias Forenses” (Grado en Criminología). Durante las Jornadas, que duraron 5,5 horas, se impartieron un total de 6 comunicaciones orales con diferente temática: el grafeno, las cianotoxinas, los aditivos aliáceos en alimentación humana y animal, los estilbenos en los vinos, o los bioplaguicidas; todas ellas sintetizadas en unos trípticos divulgativos repartidos entre los asistentes para su divulgación en su entorno social. Asimismo, se realizaron 2 ponencias invitadas por parte de expertos en Toxicología Forense y Ambiental, respectivamente. La actividad contó con casi un total de 75 asistentes y los resultados de las encuestas mostraron en general un alto grado de satisfacción con las mismas, mostrando las Jornadas como una enriquecedora actividad de divulgación científica, por la variedad de temas tratados, los nuevos conocimientos adquiridos y el acercamiento a la investigación e interés suscitado entre los asistentes.The " Scientific dissemination conference: Contributions of Toxicology in substance safety research and for society" were held on May 19th, 2023 at the Faculty of Pharmacy of the University of Seville, thanks to a financial support received by the VII Plan Propio of the University of Seville (VII PPIT-US) for scientific dissemination activities. The objective was to disseminate scientific knowledge among our students by highly qualified teaching and scientific personnel, and also to inform society in general of the high-level scientific research work that is being carried out in the University of Seville. The activity was aimed at students of the subjects of "Toxicology", "Chemoinformatics, Research and History of Pharmacy", " Laboratory of Pharmacy" (of the Degree in Pharmacy, Degree in Optics and Optometry, and Double Degree in Pharmacy and Optics and Optometry), and the subjects of "Toxicology of the Drugs of Abuse" or "Introduction to Forensic Sciences" (Degree in Criminology). During the Conference, which lasted 5.5 hours, 6 oral communications were given on graphene, cyanotoxins, alliaceous additives in human and animal feed, stilbenes in wines, or biopesticides. All of them were synthesized in informative triptychs distributed among the attendees for their dissemination in their social environment. Likewise, 2 invited presentations were given by experts in Forensic and Environmental Toxicology, respectively. The activity had 75 attendees and the results of the surveys generally showed a high degree of satisfaction with them, showing the Conference as an enriching outreach activity, due to the variety of topics covered, the new knowledge acquired and the approach to research and interest aroused among attendees

In vitro toxicity evaluation of graphene oxide and reduced graphene oxide on Caco-2 cells

Graphene derivatives are expected to have a great impact in a wide range of applications, among them as food packaging materials. This is one of the sources of potential human oral exposure to them. However, studies devoted to investigating their putative toxic effects at the intestinal level are underrepresented in the scientific literature. Thus, this study aimed to investigate the in vitro toxicity of reduced graphene oxide (rGO) and gra- phene oxide (GO) in the human intestinal Caco-2 cell line. rGO and GO were firstly characterized and later, cell viability was assessed after exposure to 0–250 μg/mL rGO/GO for 24 and 48 h. Internalization was evidenced for both materials using transmission electron microscopy. A mean effective concentration (24 h) of 176.3 ± 7.6 μg/ mL for cytotoxicity was obtained for rGO, whereas GO did not induce any change at the concentration range evaluated. However, both of them altered oxidative stress biomarkers, causing increased reactive oxygen species (ROS) and depletion of the glutathione content (GSH) after exposures up to 24 h. Further studies, particularly with rGO, are required to elucidate their toxicity profile in experimental models relevant for oral exposures.Fondo Europeo de Desarrollo Regional (FEDER) y la Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía - FEDER 2014–2020/US-1259106Consejería de Transformación Económica, Industria, Conocimiento y Universidades, Junta de Andalucía (PAIDI-2020/FEDER)-P18-RT- 1993Plan VI Propio de Investigación de la Universidad de Sevill