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

Background

Release of radionuclides, such as ¹³⁷Cs and ⁹⁰Sr, into the atmosphere and the ocean presents an important problem because internal exposure to ¹³⁷Cs and ⁹⁰Sr 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 ¹³⁷Cs or ⁹⁰Sr from the body. We evaluated the potential of Chlorella as a decorporation agent in vitro and in vivo, using ⁸⁵Sr instead of ⁹⁰Sr.

Methods

In vitro experiments of adsorption of ¹³⁷Cs and ⁸⁵Sr to Chlorella were performed under wide pH conditions. The maximum sorption capacity of Chlorella to strontium was estimated using the Langmuir model. A ⁸⁵Sr solution was orally administrated to mice pretreated with Chlorella. At 48 h after ⁸⁵Sr administration, the biodistribution of radioactivity was determined.

Results

In the in vitro experiments, although ⁸⁵Sr barely adsorbed to Chlorella at low pH, the ⁸⁵Sr adsorption ratio to Chlorella increased with increasing pH. The maximum sorption capacity of Chlorella to strontium was 9.06 mg / g. ¹³⁷Cs barely adsorbed to Chlorella under any pH conditions. In the biodistribution experiments, bone accumulation of radioactivity after ⁸⁵Sr 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 ⁹⁰Sr into the blood and enhance the elimination of ⁹⁰Sr 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.