Assessing the DNA Damaging Effectiveness of Ionizing Radiation Using Plasmid DNA

Area of Science:

• Radiation Biology
• Molecular Biology
• Medical Physics

Background:

• Plasmid DNA serves as a sensitive biosensor for detecting DNA damage.
• Ionizing radiation, particularly in radiotherapy, can induce various forms of DNA damage.
• Assessing DNA damage effectiveness requires reliable and transportable detection methods.

Purpose of the Study:

• To evaluate the feasibility of using plasmid DNA detectors to assess DNA damage.
• To compare the DNA damaging effectiveness of two X-ray beam qualities (100 kVp and 6 MV).
• To determine if DNA damage detection is reliable after long-distance inter-institutional shipment.

Main Methods:

• Plasmid DNA (pBR322) detectors were shipped ~8000 km between the USA and Canada.
• Detectors were irradiated with 100 kVp or 6 MV X-ray beams at doses of 10, 20, and 30 Gy.
• DNA damage, including single-strand breaks (SSBs), double-strand breaks (DSBs), and oxidized bases, was quantified post-shipment.

Main Results:

• The rate of DSBs/Gy/plasmid was 2.8±0.7 times greater for 100 kVp irradiation compared to 6 MV.
• The 100 kVp irradiation induced 5±2 times more DSBs per SSB than the 6 MV beam.
• The plasmid DNA detectors demonstrated sensitivity to relative DNA damage effectiveness despite transport.

Conclusions:

• Plasmid DNA detectors are feasible and sensitive tools for assessing DNA damage effectiveness.
• The study confirms that lower energy X-rays (100 kVp) are more effective at inducing DNA double-strand breaks than higher energy beams (6 MV).
• The robustness of plasmid DNA detectors allows for reliable DNA damage assessment even after significant inter-institutional transport.