A New Transduction Mechanism for Detecting Biological Radiation Damage Using Metabolic Response of Yeast as a Surrogate Marker

Chang Keun Yoon, Purdue University

Abstract

Radiation was a serendipitous discovery in the late 19th century and since then has been an effective tool utilized in many different fields such as energy, weaponry, medical diagnosis/treatment, food sterilization, and archaeological. As its demand increased in multiple areas, it became necessary to control it more precisely and cautiously, and so began the accelerated development of radiation detectors. Such radiation sensors (or dosimeters) have existed since the beginning of the 20th century in various forms. Most radiation dosimeters in use today are targeted for healthcare and industrial workers who work around high levels of radiation (e.g., hospital personnel and physicians working in nuclear medicine and radiology departments). Although the safety regulations and procedures are well established in these areas, the importance of preparing any unforeseen tragic disasters (e.g., Fukushima and Chernobyl disasters) should be never underestimated in working sites. In addition to industrial workers, other citizens occasionally experience small radiation doses from nature, and they are mostly unaware of the risks of seldom, but long-term exposure. To prevent health complications caused by such inadvertent radiation exposure scenarios, those at higher risk can don passive non-real-time dosimeters (film-type badges); these typically rely on trapped charges resulted from the passage of the ionizing radiation inside and inorganic crystal (e.g., NaI in thermoluminescent detectors). Despite their convenient portability, they usually must be shipped to facilities equipped with special dose read-out systems. Additionally, such dosimeters still face the problem of a directly quantifying the dose received by a film (inorganic material) as well as its biological severity (to humans and other biological tissue). It is, therefore, difficult to estimate the actual damage to reproductive organs and germ cells by considering only the dose absorbed as measured by contemporary charge-based radiation dosimeters. To enable the manufacturing of sensors that can more accurately assess radiation damage to biological tissue, this research focuses on the development of a bio-hybrid platform that utilizes a simple readout system to measure the radiation-induced metabolic response of biological microorganisms such as yeast immediately after exposure. The sensor can be manufactured in large quantities with a low fabrication cost using screen printing or roll-to-roll techniques and provide a response that has a direct biological correlation to the radiation exposure (in terms of either DNA or protein damage in cell). In this thesis, I first discuss a preliminary prototype developed and tested in the lab (a MEMS-type device with a deflectable polymer membrane switch); then I will discuss mainly a film-type capacitive radiation sensor using yeast as a surrogate for detecting biological radiation damage. The complete optimization of sensitivity, response time, and dynamic range of the sensor are discussed. Finally, I present an experiment conducted to classify the cause of metabolic instability of yeast after radiation exposure (studied using fluorescence microscopy).

Degree

Ph.D.

Advisors

Ziaie, Purdue University.

Subject Area

Engineering|Biomedical engineering|Electrical engineering

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