Grouping of Poorly Soluble Low (Cyto)Toxic Particles: Example with 15 Selected Nanoparticles and A549 Human Lung Cells

Cutaneous Evaluation of Fe3O4 Nanoparticles: An Assessment Based on 2D and 3D Human Epidermis Models Under Standard and UV Conditions

Purpose

The high-speed development of nanotechnology industry has fueled a plethora of engineered nanoparticles (NPs) and NP-based consumer products, further leading to massive and uncontrolled human exposure. In this regard, the researches addressing the safety assessment of NPs should be re-approached from the perspective of test parameters variety, closely simulating daily life scenarios. Therefore, the present study adopts complex in vitro models to establish the safety profile of Fe3O4 NPs, by using 2D and 3D human epidermis models under both standard and UV exposure conditions.

Methods

Advanced 3D human reconstructed epidermal tissues and two different monolayers of immortalized human cells (keratinocytes and fibroblasts), using series of in vitro assays were employed in the current study to evaluate multiple biological responses, as follows: i) divers protocols (skin irritation, phototoxicity assay); ii) different conditions (± UV exposure) and iii) a wide variety of quantification methods, such as: MTT, NR and LDH colorimetric tests - performed to evaluate the viability of the cells/microtissues, respectively, the cytotoxicity of the test compounds. In addition, IL-1α ELISA assay was used to quantify the inflammatory activity induced by the test samples, while immunocytochemistry analysis through fluorescent microscopy was employed to provide insightful information regarding the possible mechanism of action of test samples.

Results

The two test samples (S1 and S2) induced a higher cell viability decrease on immortalized human keratinocytes (HaCaT) compared to human fibroblasts (1BR3), while 3D-epidermis microtissues showed similar viabilities when treated with both samples under standard conditions (-UV rays) - for both type of evaluation protocols: skin irritation and phototoxicity. However, UV irradiation of 3D-microtissues pre-exposed to test samples led to different results between the two test samples, revealing that S2 sample induced a significant impairment of human epidermis viability, whereas S1 sample elicited an activity similar to the one recorded under standard conditions (-UV).

Conclusion

The present results indicate significant differences in toxicity between the two in vitro models under UV conditions, highlighting the importance of model selection and exposure parameters in assessing NP safety. Thus, our findings suggest that Fe3O4 NPs may pose some risks under specific environmental conditions, within the limitations of the experimental setup, and further research is needed to refine safety guidelines.

Experimental and Computational Nanotoxicology-Complementary Approaches for Nanomaterial Hazard Assessment

The growing development and applications of nanomaterials lead to an increasing release of these materials in the environment. The adverse effects they may elicit on ecosystems or human health are not always fully characterized. Such potential toxicity must be carefully assessed with the underlying mechanisms elucidated. To that purpose, different approaches can be used. First, experimental toxicology consisting of conducting in vitro or in vivo experiments (including clinical studies) can be used to evaluate the nanomaterial hazard. It can rely on variable models (more or less complex), allowing the investigation of different biological endpoints. The respective advantages and limitations of in vitro and in vivo models are discussed as well as some issues associated with experimental nanotoxicology. Perspectives of future developments in the field are also proposed. Second, computational nanotoxicology, i.e., in silico approaches, can be used to predict nanomaterial toxicity. In this context, we describe the general principles, advantages, and limitations especially of quantitative structure–activity relationship (QSAR) models and grouping/read-across approaches. The aim of this review is to provide an overview of these different approaches based on examples and highlight their complementarity.