Silver nanoparticles (AgNPs) are widely used in diverse sectors such as medicine, food, cosmetics, household items, textiles and electronics. Given the extent of human exposure to AgNPs, information about the toxicological effects of such products is required to ensure their safety. For this reason, we performed a bibliographic review of the genotoxicity studies carried out with AgNPs over the last six years. A total of 43 articles that used well-established standard assays (i.e., in vitro mouse lymphoma assays, in vitro micronucleus tests, in vitro comet assays, in vivo micronucleus tests, in vivo chromosome aberration tests and in vivo comet assays), were selected. The results showed that AgNPs produce genotoxic effects at all DNA damage levels evaluated, in both in vitro and in vivo assays. However, a higher proportion of positive results was obtained in the in vitro studies. Some authors observed that coating and size had an effect on both in vitro and in vivo results. None of the studies included a complete battery of assays, as recommended by ICH and EFSA guidelines, and few of the authors followed OECD guidelines when performing assays. A complete genotoxicological characterization of AgNPs is required for decision-making.

Worldwide antimicrobial resistance is partly caused by the overuse of antibiotics as growth promoters. Based on the known bactericidal effect of silver, a new material containing silver in a clay base was developed to be used as feed additive. An in vitro genotoxicity evaluation of this silver-kaolin clay formulation was conducted, which included the mouse lymphoma assay in L5178Y TK+/− cells and the micronucleus test in TK6 cells, following the principles of the OECD guidelines 490 and 487, respectively. As a complement, the standard and Fpg-modified comet assays for the evaluation of strand breaks, alkali labile sites and oxidative DNA damage were also performed in TK6 cells. The formulation was tested without metabolic activation after an exposure of 3 h and 24 h; its corresponding release in medium, after the continuous agitation of the silver-kaolin for 24 h was also evaluated. Under the conditions tested, the test compound did not produce gene mutations, chromosomal aberrations or DNA damage (i.e., strand breaks, alkali labile sites or oxidized bases). Considering the results obtained in the present study, the formulation seems to be a promising material to be used as antimicrobial in animal feed.

Graphene-based materials (GBMs) are a broad family of novel carbon-based nanomaterials with many nanotechnology applications. The increasing market of GBMs raises concerns on their possible impact on human health. Here, we review the existing literature on the genotoxic potential of GBMs over the last ten years. A total of 50 articles including in vitro, in vivo, in silico, and human biomonitoring studies were selected. Graphene oxides were the most analyzed materials, followed by reduced graphene oxides. Most of the evaluations were performed in vitro using the comet assay (detecting DNA damage). The micronucleus assay (detecting chromosome damage) was the most used validated assay, whereas only two publications reported results on mammalian gene mutations. The same material was rarely assessed with more than one assay. Despite inhalation being the main exposure route in occupational settings, only one in vivo study used intratracheal instillation, and another one reported human biomonitoring data. Based on the studies, some GBMs have the potential to induce genetic damage, although the type of damage depends on the material. The broad variability of GBMs, cellular systems and methods used in the studies precludes the identification of physico-chemical properties that could drive the genotoxicity response to GBMs.

Airborne micro and nano-plastics (MNPs) have been detected in both indoor and outdoor settings, raising concerns about potential adverse effects upon inhalation. Yet, their potential pulmonary toxicity has not been studied extensively. Herein, we evaluated the pulmonary toxicity and clearance of nanometric Poly-Ethylene Terephthalate (PET; ~50-200 nm) fragments from plastic bottles and two nanometric polystyrene (PS; 50 and 200 nm) beads. Adult mice were exposed to a unique dose of 50 ug in 30uL/mouse of PET, PS-50, PS-200, or vehicle by pharyngeal aspiration. The lungs, broncho-alveolar lavage fluids (BALF) and lymph nodes were collected at 1, 7 and 28 days after exposure. MNPs presence in lung tissue, accumulation in alveolar cells, and clearance from the alveolar cavity and lungs were assessed using confocal Raman microscopy (CRM). Inflammation and tissue damages were evaluated by histology, immunostaining and ELISA. PET and PS nanoplastics were detected by CRM in lungs and alveolar phagocytes. Evaluation of MNPs elimination and translocation to lymph nodes is underway. Pulmonary exposure to MNPs induced immune cell infiltration respective of MNP type or size. Recruitment of neutrophils at day 1 and eosinophils at day 7 was more pronounced for the PS-50 than for the other two MNPs. Recruitment of lymphocytes was noted at day 7, yet only for PS-50 nm. Potential long-term impact (genotoxicity, fibrosis) is under investigation. These results will inform the design of future chronic low-dose exposure studies, and path the way to new policies about the impact of MNPs on human health.