Investigation of Exhaled Breath Biomarkers for LUNG Cancer By TD-GC-MS
Authors: Rai Sujeet Kumar , Lee Meng-Rui , Lee Chien-Feng , Lee Jye-Luen , Chou Ting-I , Chiu Shih-Wen , Liang Sheng-Kai , Ko Jen-Chung , Tang Kea Tiong 
Published: May 2020

Introduction
Human exhaled breath contains more than 1,000 of the vast variety of volatile organic compounds (VOCs), providing valuable information about the metabolic process in human beings. The information of breath could include current state of disease, leading to great potential of noninvasive diagnosis in medical industry 1-6. The concentration of the exhaled breath VOCs varies in sub-ppm or even lower in ppb level in healthy people7. However, when disease occurs in the human body, the metabolic process becomes disbalance. Hence, the concentration profile of exhaled breath VOCs drastically increases. Recently, deaths caused by lung cancer have reached 1.6 million each year8. Early screening and diagnosing of lung cancer are big challenges in the healthcare industry. There are many technologies to detect and diagnose lung cancer, such as low-dose chest computed tomography (CT), which enhances the likelihood of early-stage tumor diagnosis9, resulting in an increase in the survival rate10. However, the aforementioned technique still suffers from a large rate of false positive due to cross reactive responses10. In addition, due to the existence of a low dose of ionizing radiation in the CT, employing this technique increases the risk of cancer. Therefore, a noninvasive technology for breath analysis is desired to diagnose lung cancer. In this paper, we report a fast screening method of the lung cancer biomarker in exhaled breath by using gas chromatography-mass spectroscopy coupled with thermal desorption (TD-GC-MS), which is one of the noninvasive technologies that is able to perform this task. In the experiments, Tenax TA material is used as absorbent to absorb the exhaled breath VOCs, thermal desorption system is used to desorb the VOCs, which are separated by the gas chromatography column and further detected by the mass spectrometer.

Method

A 1 Liter Tedlar bag was used to sample the exhaled breath for the lung cancer patients at the NTU hospital Hsinchu. Further, the breath sample was transferred from Tedlar bag to Tenax TA tube with a flow rate of 40 cc/min for 25 minutes. An Agilent type7890A GC system with 5975C inert MSD with a triple-axis detector along with Perkin Elmer thermal desorption system (Turbo matrix 100) was used. Breath VOCs were separated by Elite-5 MS column (30 m × 0.25 mm, film thickness 0.25μm, Perkin Elmer) while working in a constant pressure mode (10 psi). The mass spectrometer was set to scan mode. The program of column temperature was maintained at 80 for 4 min, and then increased at a rate of 15 per min, to 230 and held at 230 for 4 min11. After breath sampling, Tenax TA absorbent was used to absorb the volatile organic compound, then the Tenax TA was connected to the Perkin Elmer thermal desorption system.

Results and Conclusions

Gas chromatography mass Spectro meter coupled with the thermal desorption system was used in the detection of lower concentration of the volatile organic compound in the exhaled breath for lung cancer patients. The thermal desorption process was used to desorb the volatile organic compound from the Tenax TA absorbent. The desorbed samples from Tenax TA absorbent were transferred through the column. The VOCs were moved into the column by the inert gas mobile phase; then, they were separated by the stationary phase fixed into the column. The separation efficiency depended upon the gas chromatography column. The detection principle of the GC-MS was based on the mass to charge ratio (M/Z) of the ionized atom for the detection of biomarkers in the lung cancer patients. After separation in gas chromatography, VOCs were detected by the mass spectrometer. The peak area of various kind of VOCs for lung cancer have been obtained. We have found some biomarkers from lung cancer’s exhaled breath such as acetone, toluene, ethyl benzene, decane, etc. In future, we will sample the breath for the control group, after analysis by GC-MS compare the result with lung cancer patient to identify the unique biomarkers. The Figure 1 shows the profile of the peak area with respect to the various kind of VOCs for the lung cancer patient. Therefore, the TD-GC-MS is an effective technique for noninvasive diagnosis by employing exhaled breath VOCs for the health care industry. These exhaled breath biomarkers can be used to screen the early lung cancerous disease to save millions of lives worldwide.

Figure 1