The term “nanotechnology” is derived from the Greek word “nano,” meaning ”dwarf. It is the production of materials at atomic and molecular level. It involves the synthesis of molecules in the nanoscale (i.e., 10−9 m) size range. From the perspective of chemistry as well as material sciences , the idea of development of new products and materials using nanomaterials is pretty exciting because for a given particle type and size when one moves down the nanoscale, the fundamental physical and chemical properties of a material appear to change often yielding completely new and different product having very different physical and chemical properties. The size of nanomaterials is similar to that of the most of the biological molecules and thus can be useful for both in vivo and in-vitro biomedical research and applications .
Though , nanotechnology promises to improve the quality of human life, but it has also provoked concerns about potential adverse health effects on workers, the environment and consumers. Humans are exposed to nanomaterials through inhalation , skin contact , ingestion, and also injection . The tiny size of nanomaterials allows them to pass more easily through cell membranes and other biological barriers, and so therefore, nanomaterials can be easily taken up by living organisms and cause cellular dysfunction . Also, because of their unique properties, including high surface-to-volume ratios, nanomaterials are reactive or catalytic, and thus can be potentially toxic.
NANOMATERIALS AND TOXICITY
The range of nanotechnology products is wide and they can be classified as metals, metal oxides, carbon, silica, and semiconductor nanomaterials . Predicted to be two-thirds of a trillion-euro industry by 2015,n anotechnology can already be found in hundreds of consumer products, including items related to food, like fertilizers, kitchenware and tea. The very young field of nanotoxicity has already linked some nanoparticles to:
• Asbestos-like pathogencity
• Disruption of cellular functionand production of reactive oxygen species
• Damage to DNA
• Destruction of beneficial bacteria in waste water treatment systems
• Gill damage, respiratory problems and oxidative stress in fish
• Neurologic problems
• Organ damage, including significant lesions in the liver and kidneys
• Stunted root growth in corn, soybeans, carrots and cucumber
The track record of asbestos, DDT, PCBs and radiation substances that were heralded as the technological breakthroughs that would change everything should serve as a warning sign that we cannot continue to neglect the potential hazards associated with nanotechnology . The carbon nanotubes employed in their manufacturing might ultimately make a big difference to the health of humans and the environment . Some nanoparticles, liable on their composition and size, can develop permanent destruction to cells by oxidative stress or organelle injury. The size of a cell and its organelles associated with nanoparticles of numerous sizes, making it easy to understand why nanoparticles remain capable to enter cells and interact with numerous cell constituents such as nucleus, mitochondria, etc. The toxicity of nanoparticles rest on different factors, together with: size, aggregation, composition, cystallinity, and surface functionalization with surrounding tissue.
SHAPE AND SIZE OF THE PARTICLES
Toxicologists should characterize the following physicochemical properties prior to conducting hazard studies with nanoparticle-types: Particle size and size distribution (wet state) and surface area (dry state) in the relevant media being utilized—depending upon the route of exposure ; crystal structure ; aggregation status in the relevant media ; composition/surface coatings ; surface reactivity ; method of nanomaterial synthesis and its preparation including postsynthetic modifications; and purity of the sample .
Nano particles can easily penetrate cell membranes and other biological barriers into living organisms and cause cellular dysfunction.
MECHANISM OF NANOTOXICITY
The most advanced effort to date has recommended that ROS generation that can be moreover protecting or destructive throughout biological interactions and subsequent oxidative stress are persistently detected with nanoparticle toxicity.The generation of ROS and the subsequent production of oxidative stress is a predominant mechanism leading to nanotoxicity, including DNA damage, unregulated cell signaling, changes in cell motility, cytotoxicity, apoptosis, and cancer initiation and promotion. Compared to their bulk-size counterparts, engineered nanomaterials possess a small size, high specific surface area, and high surface reactivity, leading to the production of higher levels of ROS, and resulting in cytotoxicity and genotoxicity. A variety of nanomaterials has been found to induce toxicity mediated by ROS in many biological systems, such as human erythrocytes and skin fibroblasts. Silica nanoparticles induced cytotoxicity and resultant oxidative stress in a dose-dependent manner, mediated by the induction of ROS and lipid peroxidation in the cell membrane. ROS and free radical generation is one of the basic mechanisms of nanomaterial toxicity it may consequence in oxidative stress, inflammation, and subsequent destruction to proteins, membranes and DNA .
Not all nano-metal-oxide-induced toxicity is mediated by ROS. Studies by Karlesson have showed the cytotoxicity, DNA damage, and oxidative stress of different nano-metal oxides (CuO, TiO2, ZnO ), carbon nanoparticles, and multiwalled CNTs in the human lung epithelial cell line. They determined that nano-CuO was the most potent in inducing cytotoxicity, DNA damage, oxidative lesions, and significantly increasing intracellular ROS. Nano-ZnO showed cytotoxicity and DNA damage. Nano-TiO2, containing both rutile and anatase forms, caused DNA damage. Nano-CuZn Fe2O4 was potent in inducing DNA lesions. CNTs led to cytotoxicity and caused DNA damage. These results indicate that nano-CuO exhibits the highest cytotoxicity and genotoxicity, and is the only studied nanomaterial that induces ROS.
EFFECTS ON THE ENVIRONMENT
It has been studied and analyzed that the nanoparticles will eventually wash down our drains and into our water systems, creating problems
With water resources, fishing, and farmland. The ultimate fate of nanoparticles once released into the environment remains very much unexplored. In addition to polluting waterways, nanoparticles could also have a negative impact on farmland, which is also serving as an unwitting testing ground for nano-sized innovations. The nano material could wipe out good or beneficial bacteria that is responsible for the neutralization of ammonia in the waste water treatment systems. Studies have also proven that nano-silver that is extremely toxic is capable of harming or destroying altogether benign species of bacteria that are utilized in waste water treatment and hinders the reproductive activity of good bacteria which is extremely essential for breaking down of all the organic waste or matter from the waste water.