Mr. Smith, stock broker for a famous firm, has interest in technology. So he always update his home electrical appliances and other gadgets regularly as there are no money constraints for him. Recently he purchased a new silver nanotechnology based washing machine. The sales person describe nanotechnology is the current highest technology which keeps the clothes away from bacteria and bad odour. A sales person knowing that much is good. He insisted on the beneficial part of nanoparticles and nanotechnology. Does he forget the other face of nanomaterials?! The toxic nature of nanoparticles, unfortunately, has become a major concern for environmentalists rather than general public.
Do nanoparticles are toxic? Yes, nanoparticles are toxic but with high dosage concentrations. The study of nanoparticle toxicology is being carried out in many labs around the world and also publishing the results in many journals of various big publishers. The scientific community is concerned over the toxicity of the nanoparticles more than the policy makers and public. Nanoparticles are the smallest particles of metal or non metal or oxides etc., which are of the order thousand time lesser than micron size. Such small nanoparticles can reach to very end of the lungs, if inhaled, and very end of the blood vessels in the tissue if entered. Such a kind of particles are generally threat to the human body but thanks to god for giving such a strong immune system mechanism and defence processes, that the particles can be eliminated by RES system mostly, Urination etc. The problem comes when the dosage is high.
The high dosage of nanoparticles is toxic to cells which are the fundamental units of human body. The malfunction of a cell division leads to the generation of a bunch of immortal cells called as tumor and famous with the name "Cancer". Upto now we are talking about the toxicity of nanoparticles to healthy cells by dose dependent manner. Can't we use this aspect for the killling of cancer cells! A recent report in Nano Today authored by Stefan J. Soenen  reviewed the same aspect elaborately. The cancer cells are more prone to nanoparticle toxicity than the healthy cells which is an advantage to fight against cancer. The fluidity of the cancer cells enables the easy intake of nanoparticles which can act by two mechanisms. One way is to elicit the apoptosis pathway and the other one is the long term metal leaching. In the first mechanism, the nanoparticles are receptor mediated uptaken or by endocytosis stays for a long time inside the endosomes. The degeneration of the nanoparticles cause pH changes in endosomes which then give signals to the nucleus to self destruct which is nothing but apoptosis. The other mechanism is the long term staying of the particle inside the cell and releasing the metal ions for a longer periods. These metal ions will be toxic to cells. It was proved that the metal ions alone given to cells are not affected than the cells given metal nanoparticles. The scientific understanding of the behaviour of nanoparticles toxicity to cells help in understanding the dose concentration and also the nanoparticle properties.
Toxicity studies of nanoparticles play a crucial role in understanding the demon of high dosage nanoparticles which can also become an angel in killing cancer cells. The two faces of nanoparticles is beneficial as per their application. The vibrant future of nanotechnology in providing the beneficial and commercial products is ahead.
Stefaan J. Soenen, Jo Demeester, Stefaan C. De Smedt, Kevin Braeckmans. Turning a frown upside down: Exploiting nanoparticle toxicity for anticancer therapy.Nano Today (2013) 8, 121—125.