The application of gamma and beta rays in nuclear technology: irradiation techniques in biological research

introduction

Since the mid-20th century, nuclear technology has made significant progress in multiple fields, especially in biological research and agricultural breeding. Gamma (gamma) rays and beta (beta) rays, as important components of nuclear radiation, are widely used in mutagenic breeding, biomedical research, and sterilization of medical devices. This article will start from the basic characteristics of gamma and beta rays and explore their irradiation techniques and applications in biological research.


The basic characteristics of gamma and beta rays

gamma ray 

Gamma rays are high-energy electromagnetic waves released by atomic nuclei during radioactive decay, which have extremely strong penetrating power and can penetrate several centimeters thick lead plates or several meters thick concrete walls. Its energy range is wide, ranging from tens of kiloelectron volts (keV) to tens of megaelectron volts (MeV). Due to the uncharged nature of gamma rays, their interaction with matter is mainly achieved through Compton scattering and photoelectric effects, which can cause damage to large molecules such as DNA and RNA within cells, leading to cell mutation and even death.

BETA Ray 

Beta rays are high-speed electron flows with lower energy, typically not exceeding a few MeV. Unlike gamma rays, beta rays are negatively charged, so they are influenced by Coulomb forces when interacting with matter, resulting in relatively weak penetration. However, even so, beta rays can still penetrate several millimeters thick aluminum plates or centimeters thick organic matter, causing damage to biomolecules within cells.

The application of nuclear technology in biological research

Irradiation breeding

Radiation breeding is an important application of nuclear technology in the field of agriculture. By treating organisms with ionizing radiation, genetic mutations are induced to screen for excellent mutated individuals and cultivate new varieties. This technology was first successful in the 1930s by Indonesian scientist Tollenear M. D. using X-rays to treat tobacco, marking the beginning of radiation induced breeding.

Basic steps

The basic steps of irradiation breeding include: selecting mutagenic parents, determining irradiation dose, planting and selecting seed plant mutagenic materials, and identifying excellent mutants of seed reproductive plants. Among them, the selection of irradiation dose is crucial, ensuring sufficient mutation rate while not causing the majority of sample deaths. The LD50 principle is usually adopted, which refers to the dose corresponding to 50% death of M1 generation plants as a reference.


Types of ionizing radiation

There are many types of ionizing radiation that can be used for irradiation breeding, including X-rays, gamma rays, beta rays, ultraviolet rays, neutrons, protons, and heavy ions. Traditional radiation breeding mainly chooses gamma rays because the gamma rays produced by cobalt sources are low-cost, easy to obtain, and portable. However, with the development of accelerators and nuclear science, research on neutron, proton, and heavy ion irradiation breeding has gradually increased. Neutrons, due to their lack of charge, can penetrate deeper into the interior of matter, causing more complex biological effects; Protons and heavy ions, due to their high energy transfer line density (LET), can induce more chromosomal aberrations and non reconnected DNA double strand breaks, improving mutation efficiency.

success cases

So far, thousands of crop varieties have been bred by radiation breeding technology all over the world, of which the varieties bred in Chinese Mainland account for a considerable proportion. For example, excellent new varieties of crops such as soybeans, rice, alfalfa, and peanuts have been successfully cultivated through fast neutron irradiation breeding. These new varieties not only increase yield and quality, but also enhance stress resistance, bringing significant economic benefits to agricultural production.

Biomedical research 

In the field of biomedicine, gamma and beta rays are also widely used, mainly focused on radioactive nuclide therapy, in vitro radioactive nuclide imaging, and radioactive nuclide laboratory testing.

Radionuclide therapy

Radionuclide therapy utilizes the radioactive killing effect of radioactive nuclides to target and deliver them to tumor tissue, killing tumor cells through the gamma or beta rays emitted, thereby achieving the goal of treating tumors. For example, iodine-131 is often used to treat thyroid cancer. After entering the body orally, it can specifically accumulate in thyroid tissue, releasing beta rays to destroy cancer cells.

Extracorporeal Radionuclide Imaging

Extracorporeal radioactive nuclide imaging is the use of differences in the distribution of radioactive nuclides in the body, by measuring the gamma or beta rays emitted by surface radioactive nuclides, to obtain images of the distribution of radioactive nuclides in the body and diagnose diseases. This method has wide applications in bone scanning, thyroid imaging, kidney imaging, myocardial imaging, and other fields. For example, technetium-99m (Tc-99m) is a commonly used imaging agent, which emits gamma rays that can penetrate human tissue and be detected by detectors to generate clear images, helping doctors diagnose diseases.


Radionuclide laboratory testing

Radionuclide laboratory testing utilizes the radioactive labeling effect of radioactive isotopes to label them onto the substance to be tested. By measuring the gamma or beta rays emitted by radioactive isotopes, the content of the substance to be tested is quantitatively determined. This method plays an important role in fields such as radioimmunoassay, radioligand analysis, and radiotracer analysis.