Development of a Microfluidic Biosensing Platform for Quantification of Radiation-Induced DNA Damage

Abstract

Unexpected nuclear leakage in accidents causes severe environmental contamination. For instance, radioactive isotopes originating from the Fukushima nuclear accident happened in 2011 have been found in the Pacific biota, which further aroused the publics’ attentions on the nuclear safety worldwide. As a result, there are tremendous demands on developing an effective and reliable radiation detector, which offers a prompt response of radioactivity in samples, e.g. drinkable water. In particular, the release of α emitting radionuclides in nuclear contaminants can be more harmful than β- and γ- radiations if inhaled or swallowed, as the α-particles can be easily absorbed by cells and tissues and causes carcinogenetic or other physiological diseases. Besides high absorption in materials, α-particle has a high linear energy transfer, it deteriorates quickly during transmission and disappears within an extremely short penetration depth in media, causing the detection very challenging and largely limiting the detection sensitivity.

Although there have been many kinds of α-radiation detectors developed by other researchers, they may need specific instruments or chemical treatments. And in addition, their applications are largely limited by the high cost and the long data processing time. Therefore, we developed a microfluidic radiation biosensing system for effective and reliable radiation monitoring with reduced cost. This system is realized by transgenic technology, microfluidics and biosensor technology. The working principle is based on the β-galactosidase generation of genetically modified bacteria Deinococcus Radiodurans PZ0423 (DRPZ423) upon exposure of the radiation. β-galactosidase is expressed under its own deoxyribonucleic acid (DNA) damage-inducible gene promoter (dr_0423) and can be detected through standard amperometry method. Experiments with genetoxic chemical sodium selenite and X-Ray radiation were conducted respectively to further investigate DNA-damage response capability of DRPZ423 and our results demonstrated that β-galactosidase was successfully generated and detected.

With the purpose of detecting α-particles, a bacteria trapper was further developed to increase cell numbers under exposure of α-radiation source to enhance the sensitivity and our results verified this performance. Another set of experiment was conducted to guarantee that the trapping process did not affect amperometry detection. Additionally, the ultra-thin transparent membrane and micro-interdigitated electrodes were also employed to realize the proposed α-radiation detection system. We tested α-particles penetration efficiency of the ultra-thin transparent membrane and found that less than 5% of α-particles lost during the transmission which ensured the effective irradiation. In the end, we conducted experiments with α-radiation source and the results demonstrated that the proposed detection system was capable to detect a wide range of ionizing radiations. Moreover, a micro mixer was developed to mix irradiated bacteria and p-aminophenyl-β-D-galacto-pyranoside (PAPG) to shorten mixing time and reduce the loss of p-aminophenol (PAP) and thus to improve the detection performance. Altogether, this work has demonstrated a novel microfluidic radiation biosensing technique for achieving reliable radiation monitoring with reduced cost. To the best of our knowledge, we are presenting the first microfluidic chip combined with biosensor for radiation detection through an electrochemical method.

Date of Award	15 Dec 2017
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Hiu Wai Raymond LAM (Supervisor)