Development of Microbeam System using Laser-Plasma X-ray and Identification of DNA double strand breaks in the Cancer Cell

Abstract

Purpose:
The purpose is the development of the microbeam system using a laser-plasma x-ray and is to verify DNA double strand breaks induced by the laser-plasma x-ray irradiation.
Materials and Methods:
A tabletop Ti:Sapphire laser was used to generate the Kα x-ray pulse from a copper (Cu) target. The laser energy, the pulse width, the shot rate, laser spot size on the target surface, the intensity were approximately 150mJ, 70fs, 10Hz, 30μm, and 3x10¹⁷W/cm², respectively. The number of Cu- Kα photon and pulse duration were approximately 3x10¹⁰ photons/4πsr/pulse and 1ps, respectively. The x-ray was focused on human lung adenocarcinoma cell line (A549) by using the polycapillary x-ray lens. The measurement of the x-ray spot size and the dose estimation were confirmed with Gafchromic film EBT. In order to detect the DNA double strand breaks (DSB) induced by laser-plasma x-ray irradiation, the immunofluorescence staining was performed with anti γ-H2AX antibody and anti phosphorylated ATM antibody.
Results and Discussion:
The absorption dose of laser-plasma x-ray was 0.12mGy per laser pulse. Result from immuno fluorescence staining after the laser-plasma x-ray irradiation, γ-H2AX and phosphorylated ATM focus formation in the nucleus was detected. The focus positive cells existed range from 600 to 900μm in diameter, this length almost corresponded with the x-ray spot size. These results show that the laser-plasma x-ray can induce DSB in the cancer cells and apply to radiobiological study. The laser-plasma x-ray have attractive features such as monochromaticity, high brightness, focusing ability, and ultra-short duration compared with conventional x-ray. Near future, we will start to research the radiation response to the ultra intense and short pulse x-ray.