Nano-toxicology is the discrete size results and huge area to volume ratio, nanomaterials have distinctive characteristics in contrast with their larger equivalent that influence their toxicity. In particular, nanoparticles have been shown to offer greater specificity with enhanced bioavailability and less detrimental side effects as compared to the existing conventional therapies in nanomedicine. Therefore, bio-nanotechnology has received massive concentration in recent years. However, despite the extensive use of nanoparticles today, there's still a limited understanding of nanoparticle-mediated toxicity. Both in vivo and in vitro studies have shown that nanoparticles are closely associated with toxicity by increasing intracellular reactive oxygen species (ROS) levels and/or the levels of pro-inflammatory mediators. Nanoparticles are also known to up-regulate the transcription of various pro-inflammatory genes, including tumor necrosis factor-? and IL (interleukins)-1, IL-6 and IL-8, by activating nuclear factor-kappa B (NF-?B) signaling. However, the precise molecular mechanisms underlying nanotoxicity aren't fully understood. This lack of knowledge is a significant impediment in the use of nanoparticles in vivo. Nanotoxicology includes the study of the toxicity of nanomaterials to better understand and assess the health risks involved in the use of nanoparticles. The physicochemical properties of nanoparticles, like small size, large area and versatile chemical composition/structure that favor their use in nanomedicine, have also been found to contribute to their enhanced toxicological side effects. Specifically, particle size and area are considered important factors that contribute directly and significantly to toxicity of nanoparticles, with smaller sized nanoparticles exhibiting higher toxic effects thanks to increased surface area. Other than size and structure the shape of the nanoparticle also donate to nanotoxicity. For example, studies with carbon nanofibers, single-wall nanotubes (SWCNTs) and multi-wall nanotubes (MWCNTs), have revealed that the toxicity of carbon material with high-aspect ratio is determined by particle form and dimensions. Moreover, the nanoparticle surface dictates the adsorption of ions and biomolecules, thus influencing the cellular responses elicited, and thereby contributing to nanoparticle induced toxicity. Humans can be exposed to nanomaterials via several routes such as inhalation, injection, oral ingestion and the dermal route. Specifically, the respiratory system, gastrointestinal tract, the circulatory system as well as the central nervous system are known to be adversely affected by nanoparticles. In vivo experiments have revealed that carbon nanotubes are found to cause dose-dependent epithelioid granulomatous lesions in the lung and persistent interstitial inflammation on chronic exposure. Furthermore, ceramic nanoparticles, commonly used for drug delivery, have been reported to exhibit oxidative stress/cytotoxic activity in the lungs, liver, heart, and brain, as well as have teratogenic/carcinogenic effects. In addition to causing detrimental respiratory effects, nanoparticles administered via injection are shown to enter the circulation , causing secondary complications within the cardiovascular system and further gain access to the central nervous system. Engineered carbon nanoparticles and nanotubes were found to induce the aggregation of platelets in vitro, and thus enhance vascular thrombosis in rat carotid artery. Such perception is in great part supported exaggerated reporting within the popular press, leading to a “Nanotoxicity-Hype Correlation.

Nanotoxicology is meant to deal with the toxicological activities of nanoparticles and their products to work out whether and to what extent they'll pose a threat to the environment and to human health, and defined because the study of the character and mechanism of toxic effects of nanoscale materials/particles on living organisms and other biological systems. It also deals with the quantitative assessment of the severity and frequency of nanotoxic effects in reference to the exposure of the organisms.

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