Nanomaterials toxic effects

Degradability is an important factor in the assessment of the toxicity of nanomaterials [71]. Nondegradable nanomaterials may in fact accumulate in organs and/or intracellularly, where they would exert toxic effects. 

The increase in environmental awareness and the acute effects of some toxic compounds have raised questions over the safety of using many chemicals invented for agricultural and industrial applications. A great deal of current research addresses the management and remediation of old contaminated sites. Recent concerns regard the safety of consumer chemicals, especially nanomaterials the effect of pharmaceuticals on ecosystems and the combined effect that chemical cocktails have on human and ecosystem health. 

Table 3.3 Nanomaterial effects as the basis for pathophysiology and toxicity. Effects supported by limited experimental evidence are marked with asterisks effects supported by limited clinical evidence are marked with daggers. From Nel A, Xia T, Madler L, Li N (2006) Toxic potential of materials at the nanolevel. Science 311 622-627. Reprint with permission from AAAS...

Nanomaterials may in their own right possess novel and useful properties or as a composite of the same or different materials to form larger useful structures. Safety consideration is therefore of paramount importance since completely inert materials have the ability to exhibit toxic effects by virtue of a reduction in their size and associated increase in surface area-mass ratio, let alone materials manipulated specifically to impart novel properties. 

The toxic effects of nanoparticles have not been clearly characterized. Based on analogy to fibers and particles and what we know about their toxicity and mechanisms, it seems possible that some nanomaterials may act similarly as those carcinogenic fibers and particles. It has been suggested that carbon nanotubes could have features of both nanoparticles and fibers and may exhibit some of their effects through oxidative stress and infianunation (Donaldson et al. 2006). Nanoparticles of... 

Lungs are another part of the body which is particularly exposed to silver nanoparticies. Experiments investigating the effect of inhaled nanomaterials demonstrated that lungs are an easy target for nanosilver, which may additionally migrate via the nasal pathway to the brain. However, there is a limited amount of evidence concerning toxic effects on lung cells (Soto et al., 2007). 

Size and shape Particle size has obvious effect on the toxicity of nanomaterials. An inverse relation between size and potential toxic effects is usually established small NPs offer a higher surface area and as a result a higher number of potentially reactive molecules in comparison with larger ones (given equal mass) [20]. Decreasing the size of NPs triggers the potential reactivity of these materials in an exponential way [21]... 

Reijnders, L (2010) Hazards of Ti02 and amorphous Si02 nanopartides, in Toxic Effects of Nanomaterials (ed. H. Khan), Bentham Sdence Publishers. 

Respiratory tract exposure is the most common and widely studied pathway of particulate matter invasion [14, 32, 35, 51, 84], and the same is true for nanomaterials. The inhalation of airborne natural particulate matter or engineered nanomaterials may lead to serious toxic effects for example, the prolonged exposure and uptake of these materials in the human lung can cause chronic obstructive pulmonary disease and pulmonary morbidity, both of which may lead to death [32]. Therefore, it is crucial to understand how these materials enter and reside in... 

Recently, the toxic effects of engineered photoactive nanomaterials have undergone extensive investigation, notably the toxicity of quantum dots [14, 32, 33, 35],... 

Pulmonary exposure is the most popular route for in vivo investigations of nanomaterials-induced toxidty. In order to better understand the toxic effect of amorphous silica nanomaterials, the nanomaterials were instilled into the respiratory tract [38, 44—46, 100] and, after a period of treatmenf the acute and subacute pulmonary toxic effects were monitored. However, this phenomenon was an induced transient toxicity, and pulmonary function was fully recovered after several days post-exposure. Compared to the persistent pulmonary inflammation caused by crystalline silica nanomaterials, the negative effect of amorphous silica nanomaterials was considered insignificant. 

The toxicity of amorphous silica nanomaterials has been investigated both in in vitro and in vivo. Although the severity of the toxic reaction increases as the size of the amorphous silica is reduced to the nanometer scale, compared to metal-containing nanomaterials silica nanomaterials exhibit a relatively lower toxicity, due to their amorphous sihca structure. Among in vitro studies, no significant toxic effect was observed for sihca nanomaterials at concentrations up to lOOngmT ... 

Currently available information suggests that the shape of nanomaterials can affect their toxicity in two ways. First, the shape has an effect on the rate of its cellular uptake and second, it can affect the extent of nanomaterial aggregation, altering its cytotoxic properties. A recent in vitro toxicity study showed spherical nanomaterials to be more toxic than rods [120]. It was also shown to be more difficult for elliptical nanomaterials to penetrate the skin layer than spherical nanomaterials [121]. 

A detailed discussion of experimental in vitro and in vivo testing methodologies and results is not the purpose of this chapter. There are some comprehensive reviews covering this topic. For instance, the contribution by Oberdorster et al. [45] who have summarized recent data and highlighted gaps in this field two works [60, 61] review data on environmental and human effects of carbon nanotubes in relation to their properties a paper [62] that discusses toxicological endpoints of combustion-derived nanoparticles a review [63] of quantum dots toxicity an excellent review devoted to toxicity of particular nanomaterials classes by Borm et al. [26] and many others. 

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