Nanotoxicology and in vitro studies: The need of the hour

Assessing nanoparticle toxicity in cell-based assays: influence of cell culture parameters and optimized models for bridging the in vitro–in vivo gap

“…Nel et al have first raised this thought in 2006, emphasizing on the necessity to optimize the classical in vitro toxicity assays as they show several shortcomings when they are being applied for NP toxicity evaluation 28 . We believe that the major issues with the current in vitro methods are (i) the lack of a complete characterization of the particles, (ii ) the lack of standardisation and guidelines on how to perform a toxicological evaluation in vitro, (iii) the possibility of NP interfering with the assay and therefore lack of appropriate methods to evaluate nanotoxicity and (iv) the shortcomings inherent to the most used classical 2D monocultures 11,82,93,104,105 . It is therefore clear that further research on the optimization of methods is highly recommended in order to obtain reproducible data that would allow drawing firm conclusions regarding NP toxicity.…”

“…This issue is very complex since total exposure includes intentional and unintentional exposure for consumers as well as for workers at the production site via different exposure routes with the respiratory system, the GI tract and the skin being the main portals of entry 11,74,115 . Additionally exposure may occur during every stage of the NP's lifecycle, being the development, manufacturing, use and disposal of the NP 123 .…”

“…In order to try and overcome this predicament, the European Commission launched a recommendation on a definition of nanomaterials in 2011 that states that a nanomaterial is: "A naturel, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range from 1 -100 nm 8 ." As every definition has its limitations and introduces technical challenges, regulatory bodies have not yet come to a global agreement of the correct definition, but the most used criterion is the size limitation [9][10][11] . Nanotechnology itself can subsequently be described as the manipulation and application of particles and systems with at least one dimension below 100 nm 10 .…”

High throughput toxicity screening and intracellular detection of nanomaterials

“…The heterogeneity of NMs severely limits the feasibility of producing general toxicity protocols to address NM risk assessment. However, reliable, robust and validated protocols for testing NP/NM toxicity (Table 1) are essential for human and environmental risk assessment 5, 8, 9…”

“…However, obtaining toxicological data from in vitro assays alone has potential limitations since the behavior of cells with NMs in culture differs from their behavior in the complex biological systems of the whole organism 9. This is attributed to what is known as ‘coordinated tissue response,’ perhaps the most under‐researched area in the field of toxicology 5. Ideally, when considering screening novel NMs for toxic effects we should use a combination of in vitro methods simulating as closely as possible in vivo conditions.…”