Reactivity of inorganic nanoparticles in biological environments: insights into nanotoxicity mechanisms

Abstract

A deeper understanding of the inorganic nanoparticles behavior in biological media is needed not only to fully control and develop the potential of these materials but also to increase the knowledge of the physical chemistry of inorganic materials when its morphology approaches that of molecular entities. Although this knowledge and control is not yet entirely acquired, industry and society are already using nanomaterials in greater quantities and in consumer products. As normally happens when something new arrives to society, the interest in the broader implications of this emerging technology has grown together with unfounded "nanoeuphoria" and "nanoscares". In this context, only understanding the mechanisms of the nano-bio interaction will be possible to safely develop nanotechnology. In this review, we discuss on how nanoparticles behave once are naturally or intendedly produced and are exposed to humans and the environment. The response of nanoparticles inside organisms or released to the environment is complex and diverse, and depends on a variety of parameters involved. Mainly, they may i) be aggregated into microscopic particles or embedded in exposed materials; ii) the surfaces of the nanoparticles, which determine their bioactivity, experience constant modifications; and iii) nanoparticles may corrode and dissolve or they can suffer morphological modifications.

Toxicity of Ag, CuO and ZnO nanoparticles to selected environmentally relevant test organisms and mammalian cells in vitro: a critical review

“…In summary, as also underlined in the recent paper by Casals et al (2012), it is extremely important to assess the physico-chemical properties of NPs in the media where the biological toxicity tests are performed. As dissolution is one of the main contributors to the toxicity of Ag, CuO and ZnO NPs, in this review their toxicity is discussed in parallel with the toxic effects of the respective ions.…”

“…It has been also emphasized that aqueous solubility of NPs has to be incorporated into the environmental risk assessment models of NPs in addition to other key physico-chemical characteristics relevant to NPs (European Commission 2007). Solubility of NPs and the behavior of released metal ions, that is, the proportion of intact particles, metal ions and metal complexes, depend greatly on the properties of the test environment (for a review and references therein, see Casals et al 2012). The most important parameters of the test environment are pH, dissolved organic carbon content and water hardness (Wiench et al 2009; Fabrega et al 2011).…”

“…While in bulk materials the surface atoms constitute only a few percent of the total number of atoms, in NPs most of the atoms lay close to or at the surface (Casals et al 2012). There is increasing evidence that the unique desired physico-chemical properties of NPs, which make nanomaterials more efficient in industrial applications, render these materials also more harmful to living organisms.…”

Exploring New Synthetic Strategies for the Production of Advanced Complex Inorganic Nanocrystals

“…Thus, NCs are constantly exposed to degradation processes, which may either aggregate them into microscopic objects or reduce them to their constituent atoms either by chemical reactions with the surrounding media or easily because the degradated state is thermodynamically more favourable [111,112]. This fact has important implications not only on the final NC's morphology and structure but also when studying its potential toxicity and safety, frequently related to the ability of NCs to release ions.…”

Modeling the Optical Responses of Noble Metal Nanoparticles Subjected to Physicochemical Transformations in Physiological Environments: Aggregation, Dissolution and Oxidation

“…Due to their higher percentage of surface atoms and their colloidal nature, NPs experience processes that transform them towards more stable thermodynamic states at a faster time scale than their bulk counterparts [10,11], which is translated into high rates of aggregation, oxidation, dissolution and interaction with proteins [4,8,10,[12][13][14]. Aggregation, that is colloidal stability, has a significant influence on the reactivity, bioavailability and pharmacokinetic of NPs, having long been recognized to mediate the toxicity of the particles, as in the case of asbestiform materials, industrial aerosols, and ambient particulate matter [15].…”