Nanomateriales: Actividad biológica y evaluación toxicológica de la alúmina nanoestructurada, un nuevo insecticida

STADLER, T.

Buenos Aires

Congreso; XVIII CONGRESO ARGENTINO DE TOXICOLOGÍA; 2013

ATA

The worldwide need to produce an inexpensive and abundant food supply for a growing population is a great challenge that is further complicated by concerns about risks to environmental stability and human health triggered by the use of pesticides. Thus, sustainable agriculture demands new environmentally friendly pesticides that adhere to strict international regulations, raising the need for new reduced-risk pest control strategies and promoting an intensive search for new products. Part of the research on new biorational pesticides focuses on natural products such as plant extracts, oils, and inorganic materials. Insecticidal dusts represent the oldest group of substances used by men for pest management and their efficacy is based essentially on physical phenomena that have received but scant and unsystematic attention up to now. These products made a come-back as insecticides with the discovery of hidrophobic kaolin in the 90?s and recently, the discovery of nanoinsecticides brings new alternatives to expand the spectrum of applications of inorganic dusts. Among the recent technological advances in agricultural science, nanotechnology shows considerable promise, although its development for use in crop protection is in its initial stages. Recently, a novel type of particulate material, nanostructured alumina (NSA), has been found to induce mortality in insects exposed to stored grain treated with NSA dust. Stadler et al (2010 a) reported for the first time the insecticidal effect of NSA using two insect pest species as model organisms, Sitophilus oryzae L. and Rhyzopertha dominica (F.), which are major insect pests in stored food supplies throughout the world. Both species experienced significant mortality after 3 days of continuous exposure to NSA treated wheat. Nine days alter treatment, the median lethal doses (LD50) observed ranged from 127 to 235 mg kg−1. Further, Stadler et al (2012) studies have shown the insecticide efficacy of NSA compared with diatomaceous earth (DE) using dry dust applications. Results showed that NSA was more effective in killing S. oryzae than DE and was equally toxic to R. dominica. Treatment with both products also reduced progeny production in both insect species. In addition, insecticide efficacy of NSA was tested successfully on leaf-cutting ants (Acromyrmex lobicornis) [unpublished results], an important forest pest in several regions in South America, that can cause up to a 60% loss in wood production. Comparison of these results with recommended rates for commercial insecticidal dusts suggests that NSA may provide a cheap and reliable alternative for control of insect pests. NSA is characterized by 40-60ηm particles and a specific surface area of 14m2.g-1 (Mimani & Patil, 2001), which form large aggregates. From the chemical standpoint, NSA is aluminum oxide (Al2O3), a substance ubiquitous in nature, which together Silica is the major clays ingredient (Hurlbut & Klein, 1985). Unlike naturally alumina, NSA is the result of a manufacturing process by chemical synthesis and the final product is a homogeneous powder with a high degree of purity, uniform characteristics and specific physical-chemical properties, which are responsible for insecticidal activity. The mechanism of insecticidal action of the NSA depends, in principle, on particle electric charges. NSA particles are permanent dipoles, where the dipole-dipole interaction promotes the formation of aggregates with resistance to dissociation forces. In those insects that exhibit electrical body charge generated by triboelecrificación (McGonigle et al., 2002), NSA aggregates stick strongly to body surface and the cuticular waxes are adsorbed by the NSA particles due to their high specific surface activity (Cook et al., 2008), a phenomenon that leads to the insect death by dehydration (Stadler et al., 2010 b). Development and registry of nanomaterials is based on the idea that they are not new materials, although they have different properties than the products with the same chemical structure, given that novel properties emerge from products when they are at the nanoscale. For example, reactivity, specific area, electric charge and quantum effects may differ. These substances with new properties are promising as tools for crop protection and food production, opening new frontiers for nanoinsecticides in pest management. The NSA, in particular, possesses some of the characteristics of an ideal insecticide, given that it is a natural substance, not reactive, economical, with reduced probabilities of generating resistance in insects, and it is more effective than other commercially available insecticidal dusts. The current use of nanotechnology in a wide array of fields and products as well as the recent discovery of their potential in crop protection suggests that nanomaterials have a great potential for development of new products that will impact agriculture. Given the recent and widespread use of nanomaterials, there is an urgent need to study the impact of these products on human health and on non target organisms, as well as to search for more efficient and safer delivery technologies. The current levels of application of nanoparticles and the expected developments to come, suggest that nanotechnology will have a direct impact on the evolution of pest management practices in agriculture.