26 - Risk management and regulatory aspects of carbon nanomaterials

Abstract

Our atmosphere contains a substantial number of nanoparticles, including unintentionally produced nanoparticles as well as ultrafine particles or intentionally produced engineered nanoparticle (ENPs). Among all ENPs, the carbon-based ENPs, for example, single-walled and multiwalled carbon nanotubes (SWCNTs and MWCNTs), spherical fullerenes, and dendrimers, are attracting much attention. Because of the inert nature of pristine CNTs, they need to be functionalized to make them reactive with other organic and inorganic materials. The process of functionalization leads to the addition of various functional groups, which makes them dispersible in many solvents and suitable for numerous applications. However, the biocompatibility test of functionalized CNTs and their composites needs to be performed before real-time applications in the physiological system. Fixing CNT toxicity is the most determined question in nanotechnology. Contradictory reports on CNT toxicity often emerge in the literature, and a monotonous explanation of the reported toxicity remains unclear. Results from numerous experimental tests on cells have been complicated. The mechanism of CNT toxicity includes interference of transmembrane electron transfer, oxidation of cell elements, and formulation of secondary products such as dissolved heavy metal ions or reactive oxygen species (ROS). The toxicity of a CNT sample is reliant on its composition besides its geometry and surface functionalization. Numerous studies have insinuated that well-functionalized CNTs are innoxious to animal cells while raw CNTs or CNTs without functionalization manifest significant toxicity to animal or human cells at even a modest dosage.