Nanoparticles: Towards Predicting Their Toxicity and Physico-Chemical Properties

Introduction

During the last three decades there has been a dramatic increase of attention directed towards chemistry and technology of nanoparticles. The search by Google word search engine through publications for the period 1800-2008 indicates an enormous rise in frequency of the use of words “nano” and “nanoparticle” starting from 1980s. So, what is a nanoparticle? Nanoparticles are building blocks for nanotechnology, and are defined as particles (structures) with at least one dimension of less than 100 nm (Buzea et al, 2007). In fact, particles in these size ranges have been used by humankind for thousands of years. However, there has been a recent renaissance in this area because of the technological progress and therefore an ability to synthesize and manipulate such materials (Rotello, 2004). Nanomaterials are being currently used as electronics, optoelectronics, in biomedical, environmental, material and energy related areas, as cosmetics, pharmaceuticals, and catalysts. Nanomaterials exhibit unique physical/chemical properties and impart enhancements to engineered materials, including better magnetic properties, improved electrical activity, and increased optical properties. Because of the potential output of this technology, a worldwide increase in applications and investment in nanotechnology research are on rise (Srivastava et al, 2001; Klabunde, 2001; Feldheim, 2001; Edelstein & Cammarata, 1998). Moreover, the use of nanomaterials in various industries is projected to increase dramatically in the future and as a consequence, contamination of environment by these materials is expected, or at least such possibility cannot be disregarded. In fact, nanotechnology could lead to serious environmental problems. This is because it is still largely unknown how nanoparticles will impact the environment. Besides, there is still a substantial need to comprehensively investigate all physicochemical and then biological properties of nanoparticles to predict their possible impact on environment (Pitkethly, 2004; Oberdörster et al, 2005).

There is a clear need for short-term testing of their potential hazard in order to gain information towards risk assessment related to nanoparticles (Seatona & Donaldson, 2005; Seaton, 2007; Warheit et al, 2007). However, the large number of nanoparticles and the variety of their characteristics including sizes and coatings indicates that the only rational approach that avoids testing every single nanoparticle is to find relationship between physicochemical characteristics of a nanoparticle and its toxicity. For this purpose such approaches as Quantitative Structure-Activity Relationship (QSAR) can be applied (Puzyn et al, 2010; Puzyn et al, 2009). So, this approach can be applied not only to “classical” organic compounds (Kušić et al, 2009; Rasulev et al, 2007; Rasulev et al, 2010; Turabekova et al, 2008), but also for nanoparticles. If a QSAR model is developed then, ideally, toxicity of untested nanoparticle can be predicted on the basis of its physico-chemistry. Actually, there is a strong need to extend the traditional QSAR paradigm to nanoparticles, and some results related to this direction will be shown here.