Next Article in Journal
Fast Transformation of PbTe Using a Multiphase Mixture of Precursors: First Insights
Previous Article in Journal
A Solid-State Three-Stage Nd:YVO4 Laser Amplifier System Based on AOM Pulse Picker-Integrated Modulator
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
QuBS
Volume 9
Issue 3
10.3390/qubs9030023
qubs-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

DNA Damage Induced by Fast Neutron and Gamma Rays Evaluated Using qPCR

by
Youichirou Matuo
1,*,
Miyabi Yanami
1,
Shingo Tamaki
2,
Yoko Akiyama
2,
Yoshinobu Izumi
3,
Fuminobu Sato
2,
Isao Murata
2 and
Kikuo Shimizu
2,3
1
Department of Nuclear Power and Safety Engineering, University of Fukui, 1-3-33 Kanawa-chou, Tsuruga 914-0055, Fukui, Japan
2
Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871, Osaka, Japan
3
Research Institute of Nuclear Engineering, University of Fukui, 1-3-33 Kanawa-chou, Tsuruga 914-0055, Fukui, Japan
*
Author to whom correspondence should be addressed.
Quantum Beam Sci. 2025, 9(3), 23; https://doi.org/10.3390/qubs9030023
Submission received: 17 March 2025 / Revised: 23 May 2025 / Accepted: 23 June 2025 / Published: 7 July 2025
(This article belongs to the Section Medical and Biological Applications)
Browse Figures
Versions Notes

Abstract

We developed a novel dosimetric method using DNA molecules as a radiation sensor. The amount of neutron or gamma rays irradiated DNA damage was determined by evaluating the amount of DNA serving as a template for qPCR. The absorbed doses in the samples were estimated using the tally of the “t-product” in the data from the PHITS Monte Carlo particle transport simulation code. The neutron fluence for each sample was measured using the niobium activation reaction 93Nb (n, 2n) 92mNb, and the absorbed dose per neutron fluence was estimated to be 7.1 × 10−11 Gy/(n/cm2). Based on the PHITS modeling, the effects of neutron beams are attributed to the combination of proton and alpha particle beams. The results from qPCR showed that neutrons caused more DNA damage than gamma rays. The qPCR method demonstrated that neutron irradiation caused 1.13-fold more DNA damage compared to gamma ray irradiation; however, this result did not show a statistically significant difference. This method we developed, using DNA molecules as a radiation sensor, may be useful for biodosimetry.

1. Introduction

Biodosimetry uses biological indicators to evaluate the biological damage caused by radiation. If personal dosimeters are not functioning or not worn, biodosimetry tools are required to quickly assess dose and risk in emergency nuclear accidents, triage exposed persons, and take immediate medical action. There are two standard methods for biodosimetry. The first method involves the analysis of peripheral blood cell counts to detect a decrease in the number of peripheral blood leukocytes. After radiation exposure, leukocytes, especially radiation-sensitive lymphocytes, decrease in a dose-dependent manner [1]. Measuring the peripheral blood leukocyte count in exposed patients can provide an estimate of the exposure dose range. However, fluctuations in blood cell counts vary greatly among individuals, making the measurement unreliable. Conversely, the lymphocyte depletion assay uses kinetics to measure the absorbed dose, resulting in less individual variation compared with single measurements. Nonetheless, kinetic measurements must be performed within 1–2 days after irradiation, before lymphocyte counts bottom out. Additionally, a pre-constructed dose–response curve is commonly used to calculate an individual’s exposed dose [2]. The second method is cytogenetic biodosimetry, which assesses the frequency of chromosome aberrations in peripheral blood lymphocytes collected from exposed patients. Although the dicentric assay is widely accepted as the gold standard for cytogenetic biodosimetry, it has several limitations. The primary challenge lies in the instability of dicentric abnormalities, which are often lost during cell division, thereby hindering their use in estimating past exposure.
Another common technique used to evaluate DNA damage in cell nuclei is the comet assay, which assesses single-strand breaks (SSB) and double-strand breaks (DSB). The comet assay technique is generally performed under alkaline conditions and is widely used not only for radiation effects but also for evaluating the genotoxicity of chemical substances and environmental pollutants [3,4]. Moreover, the γ-H2AX fluorescent antibody method uses a type of histone protein (H2AX) that is rapidly and extensively phosphorylated, forming γ-H2AX. γ-H2AX accumulates near DSB sites; thus, DSBs in cell nuclei can be visualized using fluorescent antibodies [5]. The yield and distribution of DSBs can be assessed by detecting the γ-H2AX foci, providing a lower limit of dose estimation of 10 mGy [6]. Although this method is highly sensitive, it requires that cells be collected and processed within 30 min after exposure.
We developed a novel method for evaluating the absorbed dose, using the amount of DNA chain cleavage as an index, which is determined using quantitative polymerase chain reaction (qPCR). A qPCR-based biodosimetry approach is advantageous because the results can be obtained more quickly (within a few hours) and the analysis methods can be standardized. A simple description of how to quantify DNA is outlined as follows. In qPCR, after each cycle, the amount of DNA is measured using fluorescent dyes that produce increasing fluorescent signals proportional to the number of PCR product molecules generated. Data collected during the exponential phase of the reaction provides quantitative information on the initial quantity of the amplification target.
Herein, we evaluated the amount of DNA damage by performing qPCR on artificially synthesized DNA. In the future, assessing the amount of template DNA damage using PCR on DNA extracted from irradiated cells is possible. Fluorescent reporters used in qPCR include double-stranded DNA-binding dyes, dye molecules attached to qPCR primers, and probes that hybridize with qPCR products during amplification. Since the amplification rate of qPCR is proportional to the amount of template DNA in the sample, the quantity of damaged DNA can be evaluated by measuring the amount of amplified, undamaged template DNA. In other words, the observed DNA damage inhibits the polymerase reaction. For example, DNA strand break sites inhibit polymerase reactions, and the oxidation of single bases, such as 8-oxo-deoxypurines, has been reported to inhibit polymerase reactions [7]. Previous studies have evaluated DNA damage using qPCR, focusing on UV irradiation [8,9]. Our group reported on the DNA damage caused by ionizing radiation, evaluated using qPCR [10]. However, there is a lack of reports on various types of ionizing radiation damage detected using qPCR.
Neutrons are encountered in nuclear technology, space missions, and neutron boron capture therapy. Thus, the risk of disease arising from neutron-induced DNA damage is gaining attention [11,12,13]. Neutrons exhibit different behaviors compared with charged particles and gamma rays because they have no charge and only act on atomic nucleus. Since there is a significant amount of water in living organisms, 70–90% of fast neutrons affect living organisms through recoil protons. However, there are few reports on DNA damage caused by neutrons as fast as 14 MeV. Fast neutrons on the order of MeV are generated when nuclear fission of uranium, plutonium, and other transuranium elements occurs. Particle beams in therapy and cosmic rays, such as high-energy protons, generate fast neutrons during nuclear interactions, and there is concern that they may pose a risk during radiation exposure. Furthermore, 14 MeV neutrons are used in fusion reactor material research, activation analysis, nuclear data measurements, and reactor experiments. Research on fusion reactors is expected to progress in the future; thus, it is necessary to develop DNA-based biodosimetry for 14 MeV neutrons, in addition to gamma rays, beta rays, alpha rays, and thermal neutrons. Nuclear reactions from fast neutrons are characterized by the generation of a complex array of MeV-order hydrogen, deuterium, tritium, and alpha particles, as well as recoil protons. Compared with other fast neutron sources, such as 252Cf and 241AmBe, the 14 MeV neutron source generated by the nuclear fusion of deuterium and tritium using an accelerator has high intensity, monochromatic energy, and a high neutron-to-gamma ray ratio. The accelerator-based neutron source is extremely useful for studies in various fields; therefore, it is necessary to consider the contributions of these particles. In this study, qPCR was performed to investigate the effects of 14 MeV neutrons on DNA, and we evaluated DNA damage caused by neutrons and gamma rays. This research aims to provide a simple and effective method for dose assessment in emergency nuclear accidents.

2. Materials and Methods

2.1. Sample Preparation

Genomic DNA from a wild strain of Saccharomyces cerevisiae (S288c) was purified using the Blood & Tissue Kit from QIAGEN™, and the sample was dissolved in TE buffer (10 mM Tris-HCl, 1 mM EDTA, pH 8.0, manufactured by Nacalai Tesque, Kyoto, Japan). The URA3 gene region (804 bp) was amplified using PCR (MiniOpticon, manufactured by Bio-Rad, Hercules, CA, USA), using genomic DNA as a template. The following primers (Sigma-Aldrich, St. Louis, MO, USA) were used for PCR: reverse primer, 5′-TAAATTGAAGCTCTAATTTGTGAGT-3′; forward primer, 5′-ATTGCCCAGTATTCTTAACCCAACT-3′. The thermal profile involved 35 cycles of denaturation at 94 °C for 30 s, primer annealing at 60 °C for 40 s, and extension at 72 °C for 60 s. The PCR products were purified using the QIAGEN™ PCR Purification Kit (QIAGEN, Hilden, Germany). The sample was dissolved in TE buffer, and the final concentration was 1 μg/mL, which was determined using a BioSpec-nano spectrophotometer (SHIMADZU Co., Kyoto, Japan). The 260 nm/280 nm ratio of the sample was confirmed to be approximately 1.8.

2.2. Irradiation Experiment

A DNA sample (1 μg/mL) was sealed in a 1.5 mL polypropylene tube and irradiated with gamma rays (linear energy transfer of 0.2 keV/um) at doses of 10–100 Gy using a 60Co gamma-ray source at SANKEN, Osaka University (dose rate: 0.17–1.67 Gy/min).
Fast neutron irradiation on DNA samples was conducted using an accelerator-based neutron generator, namely OKTAVIAN at Osaka University [14,15]. OKTAVIAN is a Cockcroft–Walton accelerator. The deuterium ion beam is produced using a duoplasmatron ion source, and 14 MeV neutrons are generated via a deuterium–tritium fusion reaction wherein the deuterium ion beam is incident on the titanium-based tritium storage layer. The maximum intensity of the continuous neutron source at the titanium–tritium target in the intense irradiation room is 3 × 1010 neutrons per second. Neutron fluence was measured via foil activation using the 93Nb(n, 2n)92mNb interaction.

2.3. Evaluation of DNA Damage Using qPCR

qPCR was performed on template DNA samples using the MJ MiniOpticon PTC-1148 thermal cycler (Bio-Rad, Hercules, CA, USA). SYBR Green Premix (Bio-Rad, Hercules, CA, USA) was used as a fluorescent reagent for monitoring the qPCR amplification products. The following primers (Sigma-Aldrich) were used for qPCR: reverse primer, 5′-TTGGCGGATAATGCCTTTAGCGGCTT-3′; forward primer, 5′-ACATATAAGGAACG-3′. The region amplified by qPCR comprised 236 bp of the sample, targeted at 804 bp. The thermal profile involved 35 cycles of denaturation at 95 °C for 30 s, primer annealing at 55 °C for 30 s, and extension at 72 °C for 30 s. The qPCR amplification products were evaluated using CFX Manager software, ver. 1.5 (Bio-Rad, Hercules, CA, USA). The number of irradiation experiments was one. Six (for neutron) or four (for gamma rays) reactions from one sample were analyzed using qPCR for each dose condition. The initial template DNA concentration of the irradiated sample was calculated from the calibration curve using a standard sample serially diluted to 1, 0.1, and 0.01 µg/mL.
Based on the qPCR results, the undamaged qPCR template DNA rate was evaluated using Equation (1), then the DNA damage was calculated using Equation (2). The undamaged qPCR template DNA was obtained because there were no damaged DNA samples that halted qPCR within the amplification range. Therefore, note that we are ultimately dealing with a portion of damaged DNA for DNA damage assessment, not the undamaged qPCR template DNA. The experimental results were fitted using a linear least-squares method. Two-way analysis of variance (ANOVA) was used to test for differences in slopes of the percent DNA damage rates between the gamma ray and neutron DNA samples.
Undamaged qPCR template DNA rate [%] = (Undamaged PCR template DNA from xGy)/(Undamaged PCR template DNA from 0 Gy) × 100
DNA damage [%] = 100 [%] − Undamaged PCR template DNA rate [%]

2.4. PHITS Analysis

The absorbed doses of neutrons in the samples were evaluated based on the coefficient of absorbed dose per neutron fluence obtained using the Particle and Heavy Ion Transport code System (PHITS) [16]. PHITS is a Monte Carlo simulation code developed by the Japan Atomic Energy Agency for various applications in the field of radiation physics and nuclear engineering. The code is designed to simulate the transport and interaction of numerous particles, including photons, electrons, neutrons, protons, and heavy ions, in complex materials and geometries. In this study, the default nuclear data library was installed in PHITS (Ver. 3.24), JENDL-4.0 [17]. The 3D structure model of the neutron generator was created from the design drawings of OKTAVIAN. The simulation model of DNA was a sphere of mainly water molecules. Neutron fluence was evaluated using a tally named T-Track in PHITS. A tally named T-Deposit was used to evaluate the absorbed doses of high-energy charged particles produced in nuclear reactions. The number of fast neutrons from the source was 108. The statistical error in the absorbed dose was less than 10%.
Fast neutrons are highly transparent compared with thermal neutrons. The shape of the sample was assumed to be spherical, with a diameter of 4 mm, simulating the shape of the tube containing the DNA sample used in the experiment, although there was less dependence on the shape because the sample was small. Fluence is generally defined as the number of particles passing through a small spherical volume, as described in ICRP Publication 116, 2010 [18].

3. Results and Discussion

High-LET recoil protons generally appear during collisions between hydrogen nuclei (1H(n, n’)p) in tissues and are produced by fast neutrons (>10 keV) in the neutron beam. The biological effect of 14 MeV neutrons is estimated by performing calculations corresponding to a proton beam with an LET of approximately 5 keV/μm [19]. Furthermore, charged particle beams, such as proton beams, are expected to induce clustered DNA damage. Clustered DNA damage is defined as two or more lesions generated within 10–20 bp of DNA. Research using plasmid DNA has shown that the total yields induced by protons are approximately 6-fold greater for isolated damage and 14-fold greater for clustered damage than those induced by gamma rays [20]. Herein, the absorbed doses of the samples, which were assumed to be in the form of water spheres, were estimated using the tally of the “t-product” in the PHITS simulation data. The tally, also defined as t-let in PHITS, is an analytical method used for calculating particles and nuclei produced by nuclear reactions. Moreover, the tally was used herein to obtain information on track lengths and energy losses as a function of the LET of given materials for charged particles and nuclei. The DNA sample was set at 1 cm from the neutron source, and Figure 1 shows the 14 MeV neutron fluence distribution calculated using PHITS.
Figure 2 shows the measured energy spectrum of the neutrons and secondary gamma rays obtained at the sample position. The neutron energy spectrum shows an intense peak at 14 MeV and a broad peak between 1 MeV and 0.1 eV. Recoils and high-energy charged particles in 14 MeV neutron interactions were generated via nuclear reactions, including (n, n), (n, n’), (n, 2n), (n, p), (n, α), (n, d), and (n, t), whereas the particles in epithermal and thermal neutron interactions were generated based on neutron capture (n, γ). Secondary gamma rays were produced according to their neutron nuclear reactions. In the experiment, niobium foils were placed next to the qPCR tubes filled with the DNA samples, and the neutron fluence for the sample was measured using the niobium activation reaction 93Nb (n, 2n) 92mNb.
The absorbed dose per neutron fluence was estimated to be 7.1 × 10−11 Gy/(n/cm2). For example, an absorbed dose of 100 Gy requires a neutron fluence of 1.41 × 108 n/cm2. Figure 3 shows the contribution of recoils and high-energy charged particles to the absorbed dose. Protons caused mainly by H(n, n)H interactions have the highest contribution. The second largest factor is alpha particles (4He) caused by 16O(n, α)13C and 16O(n, nα)12C. From Figure 3, approximately 36% of the recoil nuclei have sufficient LET to be the predominant source of complex DNA damage, over protons. Moreover, the 16O, 13C, and 12C components add to the complex DNA damage. Complex DNA damage makes polymerase reactions more difficult and may increase the amount of damage measured from neutrons compared with that from proton irradiation.
Figure 4 shows the LET of the recoils and high-energy charged particles generated by the nuclear reactions. The distribution of the LET for protons is approximately 3 to 80 keV/μm, and that for alpha particles is 40 to 300 keV/μm.
Figure 5 shows the results of the DNA damage rate due to 14 MeV neutron and gamma rays. In this experiment, statistical comparisons using t-tests were performed, resulting in the detection limits of gamma and neutron irradiations being 33 Gy and 32 Gy, respectively. These obtained values indicate that this dose results in a significant difference in the amount of DNA damage detected in irradiated and non-irradiated samples. For gamma ray irradiation, the rate of DNA damage increased with the absorbed dose. However, in the case of neutron beams, the slope of the DNA damage rate became less steep above 50 Gy. This suggests that neutrons induce DNA damage through a more complicated process compared with gamma rays. As mentioned previously, the DNA damage caused by 14 MeV neutrons is likely influenced by the effects of proton beams and alpha particles. We compared the slopes of DNA damage caused by gamma ray and neutron irradiation using the method of least approximation and found that neutron-based DNA damage inhibits qPCR more. From the slopes, we also found that 14 MeV neutrons caused 1.13 times more DNA damage than gamma rays. There are few in vitro studies on DNA damage caused by 14 MeV neutrons; thus, we compared our results with those of live cell studies. The RBE for 10% survival of bone marrow stem cells by colony-forming units-spleen was 1.4 for 14 MeV neutrons and 1.2 for 15 MeV neutrons. These RBE results using fast neutrons are generally consistent with our results [21]. However, the two-way ANOVA showed no significant difference between the results obtained for gamma ray and neutron irradiation. The difference in the amount of DNA damage caused by neutron and gamma ray irradiation was within the error range of the qPCR method. Future improvements are expected to reduce errors and provide more conclusive results regarding the relative DNA damage observed during neutron and gamma irradiation.
It is also necessary to consider what type of DNA damage can inhibit qPCR. DSBs are considered to have more severe biological effects, whereas SSBs and base damage, such as damage to the abasic site (AP site), are thought to be easily repaired and have minor effects [22,23]. Notably, qPCR is inhibited not only by DNA strand breaks but also by oxidative damage to bases. The oxidants of the adenine base, 8-oxo-7,8-dihydro-2′-deoxyadenosine, and AP sites have been reported to markedly reduce the efficiency of qPCR [7]. Gamma rays induce base oxidation and AP site damage, but the oxidative damage of bases by neutrons may be limited. This is because the amount of 8-oxodG, an oxidant of the guanine base, produced by the 2.1 MeV neutron beam of 252Cf is reported to be approximately 1.75 per 106 bp per 10 Gy [24], whereas the concentration of 8-oxodG in whole blood and lymphocytes when irradiated with 0.1 Gy of gamma rays is 1.09 ± 0.27 per 105 guanine bases (not for all bases) [25]. These results suggest that DNA is oxidized less frequently by neutrons than by gamma irradiation.
We estimate that 14 MeV neutron irradiation has approximately 73% proton and 13% alpha particle contributions. Furthermore, the LET distribution for protons is approximately 3 to 80 keV/μm, whereas the alpha particles are 40 to 300 keV/μm. Differences in ionizing radiation-induced DSBs are primarily the result of radiation with high or low LET. X-ray and gamma ray irradiation are characterized by low LET, inducing sparse damage and mostly SSBs. In contrast, high-LET alpha particles or heavy ions result in localized DNA damage, containing a large amount of DSBs [26,27]. Overall, the 14 MeV neutron is expected to induce more DNA strand breaks and complex DNA damage compared with gamma rays. Therefore, it is thought that neutron beams, which are considered to be high-LET radiation, inhibit qPCR more than gamma rays, which are considered to be low-LET radiation. The effects of single DNA damage and complex DSBs on qPCR efficiency need to be studied. In our qPCR results, the amount of DNA damage caused by neutron irradiation was appropriate and consistent with the LET effect. Our results demonstrated the feasibility of evaluating DNA damage using PCR. However, the qPCR method showed no significant difference between the results obtained for gamma ray and neutron irradiation. PCR-based methods for assessing DNA damage need improvement. Digital PCR may be more effective than the qPCR used in this study to reduce the errors, as it enables absolute quantification of DNA molecules.

4. Conclusions

We reported a dose-dependent relationship for the damaged template DNA observed after neutron irradiation. The distribution of the LET for protons caused by 14 MeV neutrons was approximately 3 to 80 keV/μm. The results from qPCR showed that neutrons caused more DNA damage than gamma rays, which was consistent with previous studies. The qPCR method demonstrated that neutron irradiation caused 1.13-fold more DNA damage compared to gamma irradiation; however, this result did not show a statistically significant difference.

Author Contributions

Conceptualization, K.S.; data curation, Y.M., M.Y., S.T., F.S. and I.M.; funding acquisition, K.S.; Supervision, Y.I., F.S. and K.S.; writing—original draft, Y.M., F.S. and K.S.; writing—review and editing, Y.A., Y.I., F.S. and K.S. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by JSPS Kakenhi grants 18H01919 and 21H01861.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

We used the SANKEN facility at Osaka University, and this work was supported by JSPS Kakenhi grants 18H01919 and 21H01861 for K.S. The authors would like to thank Yoshiki Buchimaru for his collaboration on this work.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. UNSCEAR. Sources, Effects and Risks of Ionizing Radiation; United Nations: New York, NY, USA, 1998. [Google Scholar]
  2. IAEA. Cytogenetic Dosimetry: Applications in Preparedness for and Response to Radiation Emergencies; IAEA: Vienna, Austria, 2011; Volume 229. [Google Scholar]
  3. Singh, N.P.; McCoy, M.T.; Tice, R.R.; Schneider, E.L. A simple technique for quantitation of low levels of DNA damage in individual cells. Exp. Cell Res. 1988, 175, 184–191. [Google Scholar] [CrossRef] [PubMed]
  4. Tice, R.R.; Agurell, E.; Anderson, D.; Burlinson, B.; Hartmann, A.; Kobayashi, H.; Miyamae, Y.; Rojas, E.; Ryu, J.C.; Sasaki, Y.F. Single cell gel/comet assay: Guidelines for in vitro and in vivo genetic toxicology testing. Environ. Mol. Mutagen. 2000, 35, 206–221. [Google Scholar] [CrossRef]
  5. Riballo, E.; Kühne, M.; Rief, N.; Doherty, A.; Smith, G.C.; Recio, M.J.; Reis, C.; Dahm, K.; Fricke, A.; Krempler, A.; et al. A pathway of double-strand break rejoining dependent upon ATM, Artemis, and proteins locating to γ-H2AX foci. Mol. Cell 2004, 16, 715–724. [Google Scholar] [CrossRef] [PubMed]
  6. Garty, G.; Karam, A.; Brenner, D.J. Infrastructure to support ultra high throughput biodosimetry screening after a radiological event. Int. J. Radiat. Biol. 2011, 87, 754–765. [Google Scholar] [CrossRef]
  7. Sikorsky, J.A.; Primerano, D.A.; Fenger, T.W.; Denvir, J. Effect of DNA damage on PCR amplification efficiency with the relative threshold cycle method. Biochem. Biophys. Res. Commun. 2004, 323, 823–830. [Google Scholar] [CrossRef]
  8. Hegedüs, M.; Fekete, A.; Módos, K.; Kovács, G.; Rontó, G.; Lammer, H.; Panitz, C. Response of bacteriophage T7 biological dosimeter to dehydration, and extraterrestrial solar UV radiation. Acta Astronaut. 2007, 60, 445–450. [Google Scholar] [CrossRef]
  9. Rudi, K.; Hagen, I.; Johnsrud, B.C.; Skjefstad, G.; Tryland, I. Different Length (DL) qPCR for Quantification of Cell Killing by UV-induced DNA Damage. Int. J. Environ. Res. Public Health 2010, 7, 3376–3381. [Google Scholar] [CrossRef]
  10. Shimizu, K.; Matuo, Y.; Izumi, Y.; Ikeda, T. Fundamental study of the radiation monitoring system based on evaluation of DNA lesions. Radiat. Prot. Dosim. 2011, 146, 62–64. [Google Scholar] [CrossRef]
  11. Kildea, J. The Canadian Neutron-Induced Carcinogenic Effects Research Program. Radiat. Environ. Biophys. 2017, 6, 55–61. [Google Scholar]
  12. Ohnishi, T.; Takahashi, A.; Ohnishi, K. Studies about Space Radiation Promote New Fields in Radiation Biology. J. Radiat. Res. 2002, 43, S7–S12. [Google Scholar] [CrossRef]
  13. Maliszewska-Olejniczak, K.; Kaniowski, D.; Araszkiewicz, M.; Tymińska, K.; Korgul, A. Molecular Mechanisms of Specific Cellular DNA Damage Response and Repair Induced by the Mixed Radiation Field During Boron Neutron Capture Therapy. Front. Oncol. 2021, 11, 676575. [Google Scholar] [CrossRef] [PubMed]
  14. Sumita, K.; Takahashi, A.; Iida, T.; Yamamoto, J. Status of OKTAVIAN I and Proposal for OKTAVIAN II. Nucl. Sci. Eng. 1990, 106, 249–265. [Google Scholar] [CrossRef]
  15. Tamaki, S.; Panuntun, F.; Uedoi, K.; Wang, H.; Kusaka, S.; Manabe, Y.; Akiyama, Y.; Tanaka, T.; Sato, F.; Murata, I. Radioactivation Analysis of Concrete Wall in OKTAVIAN Facility. Plasma Fusion Res. 2022, 17, 1405001. [Google Scholar] [CrossRef]
  16. Sato, T.; Iwamoto, Y.; Hashimoto, S.; Ogawa, T.; Furuta, T.; Abe, S.; Kai, T.; Tsai, P.E.; Matsuda, N.; Iwase, H.; et al. Features of Particle and Heavy Ion Transport code System (PHITS) version 3.02. J. Nucl. Sci. Technol. 2018, 55, 684–690. [Google Scholar] [CrossRef]
  17. Shibata, K.; Iwamoto, O.; Nakagawa, T.; Iwamoto, N.; Ichihara, A.; Kunieda, S.; Chiba, S.; Furutaka, K.; Otuka, N.; Ohsawa, T.; et al. JENDL-4.0: A New Library for Nuclear Science and Engineering. J. Nucl. Sci. Technol. 2011, 48, 1–30. [Google Scholar] [CrossRef]
  18. ICRP. Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures; ICRP Publication 116; Elsevier: Amsterdam, The Netherlands, 2010. [Google Scholar]
  19. Jones, B. Fast neutron energy based modelling of biological effectiveness with implications for proton and ion beams. Phys. Med. Biol. 2021, 66, 045028. [Google Scholar] [CrossRef]
  20. Sui, L.; Wang, Y.; Wang, X.; Kong, F.Q.; Liu, J.C.; Zhou, P.K. Clustered DNA damage induced by protons radiation in plasmid DNA. Chin. Sci. Bull. 2013, 58, 3217–3223. [Google Scholar] [CrossRef]
  21. Ainsworth, E.; Kelly, L.S.; Mahlmann, L.J.; Schooley, J.C.; Thomas, R.H.; Howard, J.; Alpen, E.L. Response of Colony-Forming Units-Spleen to Heavy Charged Particles. Radiat. Res. 1983, 96, 180–197. [Google Scholar] [CrossRef]
  22. Lieber, M.R. The mechanism of double-strand DNA break repair by the nonhomologous DNA end-joining pathway. Annu. Rev. Biochem. 2010, 79, 181–211. [Google Scholar] [CrossRef]
  23. Chapman, J.R.; Taylor, M.R.; Boulton, S.J. Playing the end game: DNA double-strand break repair pathway choice. Mol. Cell 2012, 47, 497–510. [Google Scholar] [CrossRef]
  24. Pang, D.; Nico, J.S.; Karam, L.; Timofeeva, O.; Blakely, W.F.; Dritschilo, A.; Dizdaroglu, M.; Jaruga, P. Significant disparity in base and sugar damage in DNA resulting from neutron and electron irradiation. J. Radiat. Res. 2014, 55, 1081–1088. [Google Scholar] [CrossRef] [PubMed]
  25. Sudprasert, W.; Navasumrita, P.; Ruchirawat, M. Effects of low-dose gamma radiation on DNA damage, chromosomal aberration and expression of repair genes in human blood cells. Int. J. Hyg. Environ. Health 2006, 209, 503–511. [Google Scholar] [CrossRef]
  26. Aten, J.A.; Stap, J.; Krawczyk, P.M.; Van Oven, C.H.; Hoebe, R.A.; Essers, J.; Kanaar, R. Dynamics of DNA double-strand breaks revealed by clustering of damaged chromosome domains. Science 2004, 303, 92–95. [Google Scholar] [CrossRef] [PubMed]
  27. Eccles, L.J.; O’Neill, P.; Lomax, M.E. Delayed repair of radiation induced clustered DNA damage: Friend or foe? Mutat. Res. Fundam. Mol. Mech. Mutagen. 2011, 711, 134–141. [Google Scholar] [CrossRef] [PubMed]
Qubs 09 00023 g001
Figure 1. The 14 MeV neutron fluence distribution calculated using PHITS.
Figure 1. The 14 MeV neutron fluence distribution calculated using PHITS.
Qubs 09 00023 g001
Qubs 09 00023 g002
Figure 2. Energy spectra of the neutrons and secondary gamma rays obtained at the sample position, located 1 cm from the neutron source.
Figure 2. Energy spectra of the neutrons and secondary gamma rays obtained at the sample position, located 1 cm from the neutron source.
Qubs 09 00023 g002
Qubs 09 00023 g003
Figure 3. Contributions of recoil particles and high-energy charged particles to the absorbed dose.
Figure 3. Contributions of recoil particles and high-energy charged particles to the absorbed dose.
Qubs 09 00023 g003
Qubs 09 00023 g004
Figure 4. LET of the recoil particles and high-energy charged particles.
Figure 4. LET of the recoil particles and high-energy charged particles.
Qubs 09 00023 g004
Qubs 09 00023 g005
Figure 5. DNA damage caused by 14 MeV neutron and gamma-ray irradiation, evaluated using qPCR (number of samples = 6). The error bars represent ± 1 SD. The slope was calculated using a linear least squares analysis of the data. Two-tailed-t-tests were performed, and p-values were determined. ** represents p < 0.01 and * represents p < 0.05, measured based on two tailed t-tests assuming equal variance.
Figure 5. DNA damage caused by 14 MeV neutron and gamma-ray irradiation, evaluated using qPCR (number of samples = 6). The error bars represent ± 1 SD. The slope was calculated using a linear least squares analysis of the data. Two-tailed-t-tests were performed, and p-values were determined. ** represents p < 0.01 and * represents p < 0.05, measured based on two tailed t-tests assuming equal variance.
Qubs 09 00023 g005
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Matuo, Y.; Yanami, M.; Tamaki, S.; Akiyama, Y.; Izumi, Y.; Sato, F.; Murata, I.; Shimizu, K. DNA Damage Induced by Fast Neutron and Gamma Rays Evaluated Using qPCR. Quantum Beam Sci. 2025, 9, 23. https://doi.org/10.3390/qubs9030023

AMA Style

Matuo Y, Yanami M, Tamaki S, Akiyama Y, Izumi Y, Sato F, Murata I, Shimizu K. DNA Damage Induced by Fast Neutron and Gamma Rays Evaluated Using qPCR. Quantum Beam Science. 2025; 9(3):23. https://doi.org/10.3390/qubs9030023

Chicago/Turabian Style

Matuo, Youichirou, Miyabi Yanami, Shingo Tamaki, Yoko Akiyama, Yoshinobu Izumi, Fuminobu Sato, Isao Murata, and Kikuo Shimizu. 2025. "DNA Damage Induced by Fast Neutron and Gamma Rays Evaluated Using qPCR" Quantum Beam Science 9, no. 3: 23. https://doi.org/10.3390/qubs9030023

APA Style

Matuo, Y., Yanami, M., Tamaki, S., Akiyama, Y., Izumi, Y., Sato, F., Murata, I., & Shimizu, K. (2025). DNA Damage Induced by Fast Neutron and Gamma Rays Evaluated Using qPCR. Quantum Beam Science, 9(3), 23. https://doi.org/10.3390/qubs9030023

Article Metrics

Back to TopTop