[Physio-pathological impacts of inhaled nanoparticles]

Abstract

Nanomaterials are defined as materials with any external dimension in the nanoscale or having an internal structure or surface structure in the nanoscale, approximately 1 nm to 100 nm. They exhibit new or reinforced properties as compared to the same material at the micrometric scale, providing a benefit in numerous technological applications. However, their specific surface properties in addition to their shape, composition, size are suspected to elicit adverse responses from biological systems, underlining the need for a thorough hazard assessment. Increasing use of nanomaterials in industrial as well as consumer products extends the possibilities of environmental and occupational human exposures. During all their life cycle, from their production to their destruction through their use, engineered nanoparticles can be released and the respiratory route is one of the main unintentional routes of exposure. Although the respiratory tract is equipped with efficient clearance mechanisms, there is increasing evidence that nanoparticles exhibit an ability to cross biological barriers, getting access to the bloodstream and secondary target organs. Different features of nanomaterials (size, form, surface reactivity...) contribute to their internalization and translocation through the respiratory barrier. Short term inhalation exposure to nanoparticles induces pulmonary inflammation the extent of which is dependent on the type of nanoparticles according to shape, size, solubility...Oxidative stress is considered as a major toxicity pathway triggered by nanomaterials as they can intrinsically produce reactive oxygen species or induced the intracellular production of reactive oxygen species or anti-oxidant depletion upon interaction with cells. Alternative mechanisms are suspected, related to the ability of nanoparticles to interact with proteins. As they get in contact with biological fluids, nanoparticles are covered by a protein corona that modifies their interactions with cells, their fate and their effects. There is still a need to increase our mechanistic understanding of the toxicological events triggered by nanomaterials in order to provide relevant data for risk assessment as well as in helping to develop nanomaterials with a safer design.