Technological challenges bring ever new nanomaterials to the market that are so small that they easily enter our body. Some of these nanomaterials damage the pulmonary barrier, and some cause acute or even chronic inflammation, which can develop into even more severe forms of the disease. In order to be able to establish whether certain nanomaterials are safe in the long run to humans and the environment, such materials need to be tested, for which animal testing is usually used and long-term studies are being performed. This kind of testing is expensive and slow, so alternative methods are being developed.
One of these alternative methods of testing for chronic inflammatory triggering was published by Kokot et al. (Advanced Materials 2020). In their study, they demonstrated the mechanism and the possibility of prediction on a limited selection of nanomaterials from metal oxides. In the present work, we selected four additional nanomaterials relevant in various industries for which we wanted to test the possibility of using the mentioned alternative in vitro model for toxicity analysis and prediction of triggering inflammatory conditions. Thus, in addition to titanium dioxide, we also selected barium sulfate, cerium dioxide, molybdenum trioxide and tungsten oxide as nanoparticles of metal oxides, which are often used in industry due to their unique properties.
In in vivo studies in mice and rats, researchers have shown that most of these nanomaterials, except barium sulfate, cause at least acute inflammation in the lungs. Barium sulphate causes only a slight transient inflammatory response that does not cause irreversible effects on health. On the other hand, cerium dioxide e.g. triggers not only acute but also chronic inflammation in the lungs. The development of inflammatory conditions potentially triggered by nanoparticles is influenced by their various physicochemical properties, among which it is very difficult to select those that contribute to the triggering of long-term health complications.
To evaluate the latter, we performed detections of various early molecular events on a combination of cell cultures. Such alternative in vitro testing is faster, cheaper, easier to replicate, ethically less problematic, and at the same time can provide more relevant information. Due to many advantages, we decided to examine the possibility of predicting inflammatory conditions for these nanomaterials based on microscopy and expression of signal proteins in vitro. We have shown that the results obtained by in vitro testing are consistent with the results of in vivo studies, which may be the basis for the further development of alternative methods for determining the toxicity of nanomaterials.
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