Potential use of nanotechnology in developing radioprotectors

The cellular damage by ionising radiation is predominantly mediated through generation of Reactive Oxygen Species(ROS) which cause lesions in DNA leading to cell death and mutations. Water radiolysis generates molecules of hydrogen peroxide (H2O2), molecular hydrogen (H2), and a number of highly active free radicals such as hydrogen radical (H·), hydroxyl radical (OH·), hydroperoxyl radical (HO2·), and superoxide anion radical (O2 -·) and these molecules cause radiation injury to living cells. Chemical alterations in DNA, breaks in base-sugar, sugar oxidation, breaks in sugar phosphate back bone leading to strand breaks of the single and double strand types and release of terminal phosphates, etc. are the consequences of reactions of these free radicals. Living cells normally respond to DNA damage through coordinated and integrated DNA-damage checkpoints and repair pathways; however, failures do occur occasionally leading to mutations or cancer. Protection against ionising radiation is of paramount importance during accidental and unavoidable exposures to radiation and development of novel and effective approaches to combat radiation damages using non-toxic radioprotectors are of considerable interest for defence, nuclear industries, radiation accidents, space travels, etc., besides the protection of normal tissues during radiotherapy of tumours and medical diagnostic exposures. Recently, nanoparticles are gaining interest in the field of radioprotection. Cerium oxide nanoparticles, yttrium oxide nanoparticles, carbon nanoparticles, etc. were reported to possess antioxidant properties and several works have shown the ability of these nanoparticles to offer protection against radiation damages. Nanoparticles due to the electron clouds that surround them could have high reactivity with free radicals. Silver nanoparticles have applications in medicine, catalysis, electronics and optoelectronics. In our studies, silver nanoparticles were prepared using the phytoceutical and nutraceuticals such as glycyrrhizic acid, gallic acid, lipoic acid, ascorbic acid derivatives etc and the resultant complexes of the nanoparticles were explored for their radiation protecting properties under in vitro conditions on mammalian cells and under in vivo conditions using animal models. The results reveal the potential of using these nanocomplexes for counteracting the deleterious effects of ionizing radiation. (author)