BIOLOGICAL EFFECTS OF NANOPARTICLES (NPs) WITH SPECIAL REFERENCE TO ZnO NPs AND EARTHWORM.

Nanotechnology has tremendous potential to improve many sectors of science and technology such as industries, physical, chemical and biological engineering, consumer products, medical, environmental and agricultural sciences and so on. Due to specific physicochemical properties, nanoparticles behave differently from bulk materials. The extremely small size of nanoparticle enhances surface area-to-volume ratio making it highly reactive. Such unique and advantageous properties of NPs increase their applications in various fields. Huge amount of NPs is produced annually world-wide. The immense and diversified uses impose potential danger on environment and organisms. Toxicological studies of nanoparticles have opened a new branch of science i.e. nanotoxicology. There are three routes of entry of nanoparticles inside the body viz. inhalation, skin and gastrointestinal tract. Since the earthworm is a megadrile resource of pedoecosystem and occupies an important tropic level, many studies have focussed on this below-ground organism. Earthworms respire through skin and ingest soil so NPs enter through skin and/or gastrointestinal tract. Nanoparticle toxicity depends on particle size, shape, quality, coating, chemical properties and concentration of NPs as well as nature of encountering organisms. Nanoparticles have negative impact on survival, growth, development, reproduction and biochemical machinery of animals including earthworms. Literatures revealed that the behaviour, survival, biomass and fecundity of earthworm are greatly affected by nanoparticle exposure. NPs penetrate the cell and its organelles and disrupt cellular metabolism which eventually lead to cell death. In addition, NPs may break DNA helices, disrupt gene expression and impair mitochondrial functions. They generate reactive oxygen species in cells and cause oxidative stress. It embarks the need to ameliorate toxicological effects of nanoparticles through antioxidant-rich food, which can inhibit the process of oxidation and prevent formation of free radicals. In the present scenario, wide and indiscriminate use of nanoparticles should be avoided or minimized as far as possible to protect the health of animal world. [ABSTRACT FROM AUTHOR]