Evaluation of Chlorella as a Decorporation Agent to Enhance the Elimination of Radioactive Strontium from Body

BACKGROUND: Release of radionuclides, such as (137)Cs and (90)Sr, into the atmosphere and the ocean presents an important problem because internal exposure to (137)Cs and (90)Sr could be very harmful to humans. Chlorella has been reported to be effective in enhancing the excretion of heavy metals; thus, we hypothesized that Chlorella could also enhance the elimination of (137)Cs or (90)Sr from the body. We evaluated the potential of Chlorella as a decorporation agent in vitro and in vivo, using (85)Sr instead of (90)Sr. METHODS: In vitro experiments of adsorption of (137)Cs and (85)Sr to Chlorella were performed under wide pH conditions. The maximum sorption capacity of Chlorella to strontium was estimated using the Langmuir model. A (85)Sr solution was orally administrated to mice pretreated with Chlorella. At 48 h after (85)Sr administration, the biodistribution of radioactivity was determined. RESULTS: In the in vitro experiments, although (85)Sr barely adsorbed to Chlorella at low pH, the (85)Sr adsorption ratio to Chlorella increased with increasing pH. The maximum sorption capacity of Chlorella to strontium was 9.06 mg / g. (137)Cs barely adsorbed to Chlorella under any pH conditions. In the biodistribution experiments, bone accumulation of radioactivity after (85)Sr administration was significantly decreased in the Chlorella pretreatment group compared with the non-treatment control group. CONCLUSIONS: In conclusion, these results indicated that Chlorella could inhibit the absorption of (90)Sr into the blood and enhance the elimination of (90)Sr from the body through adsorption in intestine. Further studies are required to elucidate the mechanism and the components of Chlorella needed for adsorption to strontium and could promote the development of more effective decorporation agents.