Titanium and gold nanoparticles in asthma: the bad and the ugly

Abstract

Engineered nanomaterials (ENMs) are defined as having at least one dimension ≤100 nm 1. When ENMs have three dimensions ≤100 nm they are called nanoparticles (NPs). ENMs have attracted a great deal of attention recently because their many technologically interesting properties have led to technological growth with ensuing economic rewards 2. Technologies involving ENMs are envisaged to become the cornerstone for a number of industrial sectors, such as micro-electronics, materials, paper, textiles, energy, cosmetics and medical devices, all capable of incorporating some nanoscale-enabled properties into their products 2. By 2015, the annual profit from ENM-based products is estimated to be US$1.1–2.5 trillion 3. Today, ENMs can be found in more than 1,000 consumer products 4. By 2015, 2 million workers will be needed to support nanotechnology industries worldwide 5. However, some of the properties of ENMs that are unique and beneficial for technological applications may also endanger human health, inducing cyto- and genotoxic effects, inflammation and even cancer 6–12. Inflammatory effects are particularly important 13–15. Free radical activity or oxidative capacity of particulate matter might be essential for provoking these inflammatory responses. The physico-chemical features of ENMs that account for their deleterious health effects include a large ratio of surface area to mass and associated increased surface reactivity, altered physico-chemical properties, such as changes in melting point, solubility or electrical conductivity, or changes, for example, in the crystalline structure of the materials 16–20. Therefore, detailed evaluation of these characteristics is critical for the understanding of the mechanisms by which ENMs elicit biological responses. The respiratory system is a critical route of exposure to aerosolised ENM, by accident or by occupational exposure. A rapidly increasing number of studies have evaluated the respiratory effects …