Solution Radioactivated by Hadron Radiation Can Increase Sister Chromatid Exchanges.

Area of Science:

• Radiobiology
• Radiation Chemistry
• Nuclear Physics

Background:

• Energetic particles induce radioactivation in matter via nuclear reactions.
• Cellular effects of radioactivation are not fully understood but may relate to bystander effects.
• Hadron radiation therapy involves energetic particles, necessitating understanding of all associated biological effects.

Purpose of the Study:

• To investigate the biological effects of radioactivation in solutions exposed to hadron radiation.
• To determine if radioactivation contributes to DNA damage responses in cells.
• To explore the mechanisms underlying radioactivation-induced cellular effects.

Main Methods:

• Water or saline solutions were activated using proton, carbon, and iron ion beams.
• Activated solutions were applied to Chinese hamster ovary (CHO) cells.
• Sister chromatid exchange (SCE) frequency was measured to assess DNA damage.
• Radioactivation products were identified using a NaI scintillation detector.

Main Results:

• Radioactivated solutions emitted 511 keV gamma-rays with half-lives of approximately 2, 10, and 20 minutes, corresponding to 15O, 13N, and 11C.
• Increased SCE frequencies were observed in CHO cells exposed to radioactivated solutions.
• DNA damage induction was suppressed by delaying solution transfer or using dimethyl sulfoxide (DMSO).

Conclusions:

• Radioactivation of solutions by hadron radiation induces DNA damage in cells, likely mediated by free radicals from gamma-ray annihilation.
• These findings suggest radioactivation may contribute to bystander effects observed in hadron radiation therapy.
• Further research is needed to evaluate the cancer risk associated with radioactivation effects during radiation therapy.