Emerging in vitro models for safety screening of high-volume production nanomaterials under environmentally relevant exposure conditions

The rising production of nanomaterial-based consumer products has raised safety concerns. Testing these with animal and other direct models is neither ethically nor economically viable, nor quick enough. This review aims to discuss the strength of in vitro testing, including the use of 2D and 3D cultures, stem cells, and tissue constructs, etc., which would give fast and repeatable answers of a highly specific nature, while remaining relevant to in vivo outcomes. These results can then be combined and the overall toxicity predicted with relative accuracy. Such in vitro models can screen potentially toxic nanomaterials which, if required, can undergo further stringent studies in animals. The cyto- and phototoxicity of some high-volume production nanomaterials, using in vitro models, is also reviewed. In vivo assessment on the safety of nanomaterials, though the gold standard, is extremely resource intensive, thus rendering this approach economically unviable. Conventional in vitro models, though fast and highly economical, do not perfectly mimic real-life situations. This review delves into emerging in vitro techniques that could bridge the gap between in vivo and in vivo studies, thereby balancing between resource usage and relevance to real-life situations.