Detection biomarkers of lung cancer using mini-GC-PID system integrated with micro GC column and micro pre-concentrator
© Sun et al.; licensee Springer. 2014
Received: 10 June 2014
Accepted: 21 August 2014
Published: 15 October 2014
The survival rate of lung cancer can be significantly improved by monitoring biomarkers in exhaled air that indicate diseases in early stage, so it is very important to develop micro analytical systems which can offer a fast, on-site, real-time detecting biomarkers in exhaled air. In this paper, a mini-gas chromatography (GC)-photo-ionization detector (PID) system integrated with a micro GC column and a micro pre-concentrator was developed for forming an inexpensive, fast, and non-invasive diagnostic tool for lung cancer. This system has very strong concentrate ability owing to its integrated micro pre-concentrator, which make the detection of trace components in exhaled air very easy. In addition, the integrated micro GC column can separate complex mixtures, which overcome low resolution and poor anti-interference ability of other instruments. The results indicated that the mini-GC-PID system can effectively separate and detect the biomarkers at parts-per-billion (ppb) level.
Lung cancer is the leading cause of death in the world today; its diagnosis very often happens late in the course of the disease since available diagnostic methods are not sufficiently sensitive and specific. So, early diagnosis is very important to significantly improve the survival rate of the patients. There are strong evidences [1–4] to suggest that lung cancer can be detected by molecular analysis of exhaled air in the early stage. Breath analysis represents a new diagnostic technique that is without risk for the patient; therefore, it is very important to develop microanalytical systems which can offer a fast, label-free, low cost, no damage and on-site monitoring biomarkers of lung cancer in exhaled air. In recent years, this research direction is under intensive research owing to its potential application, and numerous studies have focused on working on development of miniaturized instrumentations for detecting biomarkers of lung cancer in exhaled air.
Phillips et al. [1–3] had screened 22 VOC components (including benzene, toluene, ethylbenzene, styrene, pentane, nonane, decane, etc.) as biomarkers of lung cancer, and patients can be diagnosed by monitoring biomarkers in exhaled air. Gordon et al.  developed a nanoelectronic nose which can diagnose cancers and kidney failure by monitoring breath biomarkers, thus opening up a new approach for diagnosing diseases in the early stage.
At present, many efforts were performed to develop new approaches or mini instruments to diagnose lung cancer in the early stage. Gang et al.  diagnosed lung cancer in exhaled breath using gold nanoparticles. However, this method must be in combination with solid-phase microextraction (SPME) and gas chromatography (GC)/mass spectrometry, which makes the detection relatively slow and complex. Schwarz et al.  developed a PTR-MS to determine concentration patterns of volatile compounds in exhaled air. However, resolution of the detection is relatively low. Ligor et al.  determined volatile organic compounds appearing in exhaled air of lung cancer patients by SPME and gas chromatography/mass spectrometry, but SPME is a relatively insensitive method and compounds not observed in exhaled breath may be present at a concentration lower than the limit of detection (LOD). Olavi et al.  developed a laser spectroscopy to monitor exhaled air. However, the detectable components were very few (including HCN, NH3, C2H2, etc.). Many other works [9–17] also had played important contributions in early diagnosis of lung cancer by monitoring biomarkers in exhaled breath.
To fabricate an inexpensive, fast, and non-invasive diagnostic tool for lung cancer, in this paper, a mini-GC-photo-ionization detector (PID) system integrated with a micro GC column and a micro pre-concentrator was developed, and this system had very strong concentrate ability, which makes detection of trace components in exhaled air very easy. In addition, the integrated micro GC column can separate complex mixtures, which overcome low resolution and poor anti-interference ability of other instruments. The results indicated that the mini-GC-PID system can effectively separate and detect biomarkers at ppb level. The goal of this work was to present design, fabrication, and characterization of the mini-GC-PID system.
Fabrication of micro pre-concentrator
Then, one end of the pre-concentrator was connected with a capillary which was emerged into the Tenax-TA powder, and the other end of the pre-concentrator was connected with a micro pump. After these channels were filled with Tenax-TA powder (80 to 100 mesh), the pre-concentrator was put into a temperature programmed oven under a nitrogen flow inside. The temperature of the oven was firstly increased gradually by 5°C/min until 200°C, and then the temperature of the oven was kept at 200°C for 4 h.
Fabrication of micro dryer and purifier
Fabrication of micro GC column
The integrated mini-GC-PID system
Materials and reagents
In this paper, the biomarkers of lung cancer were detected using the proposed mini-GC-PID system. The pure He was used as carrier gas, sample I (provided by the Beijing Hua Yuan Gas Chemical Industry Co., Ltd, Beijing, China) was composed of benzene with a concentration of 5 ppm, and sample II (provided by the Beijing Hua Yuan Gas Chemical Industry Co., Ltd) was composed of 7 components (concentrations of benzene, toluene, ethylbenzene, styrene, pentane, nonane, and decane are 10, 7, 6, 10, 5, 8, and 6 ppm, respectively). Tenax-TA and OV-101 were purchased from Sigma-Aldrich (St. Louis, MO, USA). In order to accurately simulate the actual samples, these standard samples were diluted 100 times, thus making concentration of these standard samples close to the actual samples.
Results and discussion
The characterization of the micro pre-concentrator
Rapid detection of biomarkers
The comparison of the peak area calculated from these chromatograms
Peak area with pre-concentrator
Peak area without pre-concentrator
Because cooperation with hospital is still underway, actual samples were difficult to obtain. Monitoring and detecting the actual patient samples will be performed in the future. However, the above results still demonstrated the mini-GC-PID system was able to effectively detect the biomarkers in the exhaled air that indicates diseases in the early stage.
The work here demonstrates that it is possible to fabricate a mini-GC-PID system integrated with a micro pre-concentrator and a micro GC column. Based on above experimental results, this system has strong concentrate ability and overcomes low resolution and poor anti-interference ability of other instruments owing to its integrated micro pre-concentrator and micro GC column. The results also indicated that the mini-GC-PID system effectively separated and detected the biomarkers at ppb level. However, the standard sample instead of the actual sample was used for performing the experiments due to absence of actual sample. But the work will be performed in the future and the results will be reported in next works.
The authors greatly acknowledge the financial support from the National Science Foundation of China under Grant numbers: 61176112 and 60976088. The authors greatly acknowledge the financial support from the Beijing science and technology plan project under Grant number: Z141100003414003.
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