New Portable Device Rapidly Measures Radiation Exposure

Picture the scene of the Fukushima nuclear accident. The Daiichi nuclear reactors were hit by an earthquake of magnitude 9.0, then flooded by the resulting 15-meter deep tsunami which caused a nuclear meltdown and release of radioactive materials. Over 100,000 people were evacuated from their homes due to the threat of radiation contamination. Although no deaths occurred due to the nuclear accident, there was potential for mass casualties since radiation can induce immediate and persistent damage to internal organs.

In a large-scale radiological incident like the Fukushima nuclear disaster, emergency medical personnel need a rapid way to assess radiation exposure and identify those who require immediate care. This radiation-dosimetry technology needs to be sensitive, accurate, fast and easy to use in a non-clinical setting.

Local scientists have developed a small, portable device that can quickly test the level of radiation exposure victims have suffered in such radiological emergencies. This technology was developed by scientists from Berkeley Lab, Stanford University and several other institutions, as reported in a journal article recently published in Scientific Reports. The lead researchers were Dr. Shan Wang from Stanford University and Dr. Andrew Wyrobek from Berkeley Lab.

This new dosimetry device is a novel type of immunoassay. Immunoassays are chemical tests used to detect or measure the quantity of a specific substance in a body fluid sample using a reaction of the immune system. For example, a common immunoassay test for pregnancy measures the concentration of the human chorionic gonadotropin hormone in a woman’s blood or urine sample.

In order to measure a person’s radiation dose, the new device measures blood samples for the concentration of particular proteins that change after radiation exposure. Scientists, including those in Wyrobek’s group, have previously identified these target proteins as excellent biological markers for radiation dosimetry; blood exposed to radiation has a special biochemical signature.

But scientists needed more than just target proteins. They also needed an accurate, sensitive way to quickly measure the proteins’ concentrations in a few drops of blood. So at the heart of the new device is a biochip developed by Wang’s group. This biochip uses magnetic nanoparticles and giant magnetoresistive nanosensors, so it is more sensitive and faster than conventional immunoassay techniques.

The biochip system relies on a sandwich structure where a target protein is trapped between a capture antibody and a detection antibody. The capture antibodies are immobilized on the surface of the biochip sensor. When a drop of blood is placed on the biochip, those antibodies capture the target proteins and the other proteins are washed away. Detection antibodies labeled with magnetic nanoparticles are then added, forming a sandwich structure that traps the target proteins. When an external oscillating magnetic field is then applied, the magnetic nanoparticles generate an electrical signal that is read out. This signal measures the number of magnetic nanoparticles bound to the surface, and this indicates the number of target proteins that have been trapped.

They tested the biochip system using blood from mice that had been exposed to varying levels of radiation. These novel immunoassay results were validated by comparing them with conventional ELISA immunoassay measurements. Overall, the scientists demonstrated that the new biochip dosimetry system is fast, accurate, sensitive and robust. In addition, the whole system is the size of a shoebox so it is very portable.

“You add a drop of blood, wait a few minutes, and get results,” explained Wyrobek in a press release. “The chip could lead to a much-needed way to quickly triage people after possible radiation exposure.” Although the technology is still underdevelopment, hopefully it will be available before the next radiological accident or terrorist attack occurs.