Construction and evaluation of an α-particle-irradiation exposure apparatus

Abstract

Purpose

The development of an exposure apparatus for in situ α-irradiation studies of cells. The construction of the apparatus is simple and the apparatus is maintenance free, easy to use and of low cost. This small device can be placed in an incubator, where the exposure environment is controlled. Moreover the vapor saturated incubator protects the cells from drying out, allowing long irradiation intervals.

Materials and methods

The system includes a ²³⁴U alpha (α)-source of total activity 0.77 ± 0.03 MBq in the form of a thin disk deposited on an aluminum substrate. The α-particles emitted in the air have a mean energy of 4.9 MeV at the disk surface. Source homogeneity has been studied via Rutherford Backscattering Spectrometry. Using SRIM 2013 and Monte Carlo (MC) simulations via the MCNP6.1 code, LET and energy deposition values have been calculated for various filling gasses. Furthermore, based on these simulations, the assembly’s dimensions and equivalent irradiation rate have been determined. With respect to the aforementioned dimensions, the experimental setup is constructed in a way to provide uniform irradiation of the sample. Using Sacalc3v1.4 irradiation radial homogeneity has been studied. In order to evaluate biologically our apparatus, a well-established chromosomal aberration assay has been utilized, applied in exponentially growing hamster (CHO) cells. Furthermore, immunofluorescence gamma-H2AX/53BP1 foci assay has been performed as a ‘biological detector’, in order to validate α-particles surface density.

Results

Source surface homogeneity: emission deviations do not exceed 10–15%. The optimal distance between the source and the cells for irradiation is determined to be 14.8 mm. Irradiation radial homogeneity: a deviation of 5% occurs at the first 8 mm from the center of the irradiation area, and a 10% deviation occurs after 12 mm. Chromosomal aberrations were found in good agreement with the corresponding in bibliography.

Conclusions

The current technical report describes analytically the development and evaluation stages of this experimental housing; from MC simulations to the irradiation of mammalian cells and data analysis. Moreover, guidance is provided as well as a report of the variables on which critical parameters are depended, so as to make this work useful to anyone who wants to construct a similar in-house α-irradiation apparatus for radiobiological studies using mammalian cells.

Keywords:

• α-particle irradiation
• radiation exposure apparatus
• simulations of damage
• MCNP
• SRIM
• Sacalc
• biodosimetry
• chromosomal aberrations
• immunofluorescence

Author contributions

AGG and MK conceived and supervised the study. ZN and EC performed the MC and experimental results analysis and wrote initial manuscript. ZN, SK, SAK, AGG and GIT performed, analyzed and evaluated the biological evaluation experiments. All authors participated in the writing of final manuscript and have approved it.

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

Z.N. is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Reinforcement of Postdoctoral Researchers - 2nd Cycle” [MIS-5033021], implemented by the State Scholarships Foundation (IKY).

Notes on contributors

Zacharenia Nikitaki

Ms Evangelia Choulilitsa, is currently a Postgraduate Student of Radiation Physics at University College London (UCL). Prior to that, she earned a 5-year Diploma in Applied Mathematical and Physical Sciences from the National Technical University of Athens (NTUA). This publication represents the research findings of her thesis, in collaboration with the DNA Damage Lab of NTUA.

Evangelia Choulilitsa

Dr. Zacharenia Nikitaki, PhD, since 2017 is a Post-Doctoral Research Associate at the DNA Damage Lab of the National Technical University of Athens (NTUA), Greece. She holds a PhD in Radiobiology, an MSc in Nanotechnology and an MSc in Applied Physics, all received from NTUA.

Spyridon A. Kalospyros

Mr. Spyridon A. Kalospyros is a PhD student at the Department of Physics of the School of Applied Mathematical and Physical Sciences (National Technical University of Athens) in Greece. He holds a BSc in Physics and a MSc in Mechanics, Astronomy and Astrophysics (School of Physics in the National and Kapodistrian University of Athens). He works as a radiographer-physicist in the Radiology Department (Computed Tomography and Magnetic Resonance Imaging) of Bioclinic Hospital in Athens (Greece).

Sofia Kaisaridi

Ms Sofia Kaisaridi is a Postgraduate student of Medical Physics – Radiation Physics at National and Kapodistrian University of Athens (UOA). She earned a 5-year Diploma in Applied Mathematical and Physical Sciences from the National Technical University of Athens (NTUA).

Georgia I. Terzoudi

Dr Georgia I. Terzoudi is a Director of Research in the Health Physics, Radiobiology & Cytogenetics Laboratory, Institute of Nuclear & Radiological Science & Technology, Energy & Safety (INRASTES), National Center for Scientific Research “Demokritos” in Athens, Greece. She holds a Ph.D. in Radiation Biology from the National and Kapodistrian University of Athens, Greece, a M.Sc. in Radiation Biology and Radiation Protection from the University of London, UK, and a B.Sc. in Physics from the National and Kapodistrian University of Athens, Greece.

Mike Kokkoris

Dr. Mike Kokkoris is a Professor of Experimental Nuclear Physics and Applications at the National Technical University of Athens since 2017. He carried out his Ph.D. research at NCSR 'Demokritos' and he got his M.Sc. degree at Texas A&M University in USA. He has more than 250 publications in peer reviewed journals of the field.

Alexandros G. Georgakilas

Dr. Alexandros G. Georgakilas is a Professor in the Physics Department of NTUA’s School of Applied Mathematical and Physical Sciences. He received his PhD in Radiation Biology (1999) and completed his post-doc research in the Biology Department at Brookhaven National Laboratory, USA. He developed his own research laboratory as an Associate Professor at the Biology Department of East Carolina University until 2012 and since then in National Technical University of Athens (NTUA). He has received many awards, such as the Young Investigator Travel Award from Radiation Research Society, Radiation Research Society SIT Award, ECU Thomas Harriot College Research Award and the prestigious Terashima Award from Japan Radiation Research Society. His work at ECU and NTUA as Principal Investigator has been funded by various sources. He has more than 130 publications in peer-reviewed, high-profile journals and more than 10500 citations (h index = 50). He has also been appointed Editor-in-Chief in the Journal of Biochemical Technology 2012–2015, Associate Editor Position for Cancer Letters, Radiation Research and in several other well-recognized journals. Prof. Georgakilas has been invited as a Guest Editor for a many high-impact journals and has hold invited Editorial positions for various book projects. His research interests include Radiation Biology, DNA Damage and Repair, Biophysics, Biomarker discovery for efficient radiation therapy and Bioinformatics