  Ionizing radiation (gamma and x-ray) is widely used in industry and medicine,
but it can also pose a significant hazardous effect on health and induce
cancer, physical deformity and even death, due to DNA damages and invasion of
free radicals. There is therefore an urgent unmet demand in designing highly
efficient radioprotectants with synergetic integration of effective renal
clearance and low toxicity. In this study, we designed ultrasmall (sub-5 nm)
highly catalytically active and cysteine-protected MoS2 dots as
radioprotectants and investigated their application in protection against
ionizing radiation. In vivo preclinical studies showed that the surviving
fraction of MoS2-treated mice can appreciably increase to up to 79 % when they
were exposed to high-energy ionizing radiation. Furthermore, MoS2 dots can
contribute in cleaning up the accumulated free radicals within the body,
repairing DNA damages and recovering all vital chemical and biochemical
indicators, suggesting their unique role as free radical scavengers. MoS2 dots
showed rapid and efficient urinary excretion with more than 80 % injected dose
(I.D.) eliminated from the body after 24 hours due to their ultrasmall
hydrodynamic size and did not cause any noticeable toxic responses up to 30
days.
