A team led by Professor Kim Il-doo_김일두 of Korea Advanced Institute of Science and Technology_{한국과학기술원}(KAIST) has developed a sensor that can diagnose diseases through breathing, using animal protein as a catalyst, the institute said Tuesday.

The technology enables early monitoring of diseases through pattern recognition of biomarker gases related to various diseases involved in human exhalation that is more accurate and has a high sensitivity, KAIST said. Not only a variety of single metal particles but also any combination of various particles can be synthesized to a size of 2 nanometers, it added.

Professor Kim Il-doo

The research paper in which Drs. Kim Sang-joon_김상준 and Choi Sun-jin_최선진took part as first authors appeared in the July issue of the "Accounts of Chemical Research" in the international journals of the American Chemical Society as well as in “Advanced Materials” Wiley online library, a German magazine.

Breathing fingerprint sensor technology is a key future technology to detect various illnesses with only breath exhalation without blood smear or imaging. It is possible to judge the health abnormality by checking the concentration change of the specific gases in the breath.

Exhalation gas components include hydrogen, acetone, toluene, ammonia, hydrogen sulfide, nitrogen monoxide in addition to moisture. These gases are biomarker gases emitted at high concentrations in patients with certain diseases such as asthma, lung cancer, Type 1 diabetes, and bad breath.

Diagnosis of the disease is easier because the analysis of the exhalation gas collection “Tedlar” bag is similar to a breathalyzer at a faster rate, and when injected into a small sensor device it can diagnose the disease. Also, detection can be done at the time of disease metabolism, enabling early diagnosis.

However, technological advances are needed to accurately analyze gases in the respiratory stream, which occur at very mild levels, from one-billionth (ppb) to one millionth (ppm). Hundreds of obstructive gases, especially moisture, remain a weak point for resistance-based sensors that selectively analyze certain disease-related biomarker gases.

Conventional gas sensors attempted to improve the sensing characteristics by combining specific catalysts such as platinum and palladium, but there was a limitation in that the natural surface gas sensing characteristics was not high at the ppb concentration.

To overcome the limitations of existing sensors, the research team succeeded in synthesizing various catalyst particles precipitated in a hollow protein shell using Nano-sized proteins present in animal tissues as a sacrificial layer.

The Nano-sized proteins utilized in this study have the great advantage that various kinds of heterogeneous catalysts can implement by combining the elemental materials present in the periodic table.

In particular, it is a remarkable method regarding the synthesis of a catalyst having a novel composition since the composition ratio between two elements can be easily controlled and an intermetallic compound can be produced.

For example, when platinum is the reference catalyst, it can be extended to various heterogeneous catalysts such as platinum palladium (PtPd), platinum nickel (PtNi), platinum ruthenium (PdRu), and platinum yttrium (PtY3).

The research team developed a sensing material that binds the developed heterogeneous catalyst particles to metal oxide nanofibers with a wide specific surface area and porous structure, selectively reacting only to particular bio induced gases, KAIST said. The nanofiber sensors with heterogeneous catalysts were found to have improved detection characteristics by about three to four times that of platinum or palladium catalysts, which are known to have the highest catalytic activity, it added.

Especially, acetone or hydrogen sulfide gas showed the highest sensitivity characteristic that the sensitivity changed to 100 times at one ppm.

The team also developed a disease diagnosis platform that recognizes human fingerprints and recognizes individual breathing patterns by using a sophisticated sensor array system with various kinds of sensing materials, so that the public can quickly identify the health abnormality.

Sixteen types of sensors with different selectivity have been successfully arrayed and since the expiratory concentration changes differently according to the health state of the patient, and the healthcare device.

"By using two-nanometer heterogeneous catalysts that have never been used in sensors, we can implement a sensor material library that responds to disease-related biomarker gases with high sensitivity and high selectivity,” Professor Kim said. "We will be able to develop sensors that can diagnose numerous diseases by securing various catalyst groups in the future.”

He added that sensors that diagnose diseases by breathing would help increase the cost of medical expenses by starting self-diagnosis devices that anyone can easily diagnose themselves.

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