| Recently, lung cancer has the continuously greatest incidence and mortality among all cancers. Because lung cancer is almost asymptomatic in the early stages, it is always detected in advanced stage when the curative intervention is no longer possible. It is obviously that screening is the only systematic means of finding lung tumors at early stage. However, the present detection tools for lung cancer is not available to a general high-risk population. Breath test is a non-invasive and low-cost detecting method which has potential to be a screening tool. Additionally, exhaled breath air originates in the respiratory system, which makes it more specific to lung cancer than any other cancers.The present research is devoted to exploring lung cancer markers in exhaled gas and condensate, developing detecting instruments and detecting technology which would meet the requirements of physical examination. It is expected that the early diagnosis of lung cancer will be realized after developing a detection technology which can be applied conveniently in regular medical checkup. The major contents and innovation work of this thesis are listed below.1. An effective method for identification of volatile organic compounds was investigated. As result,5 markers which is independent of non-malignant pulmonary disease.This study employed 79 lung cancer patients,54 non-malignant lung disease patients and 38 healthy subjects to contribute their exhaled air. VOCs (volatile organic compounds) in samples were collected and analyzed. Through a series of comparisons among lung cancer patients, non-malignant lung diseases patients and healthy participants,5 VOCs were selected as markers for lung cancer diagnosis. Concentrations of these markers are irrelevant to non-malignant disease. In addition, 78 subjects were employed as validation group, whose breath samples were analyzed. Even though distribution of non-malignant patients is unknown,5 markers could still discriminate subjects with or without lung cancer well. Comparing with the existed researches on selection of volatile lung cancer markers, it is the first time that the effects of non-malignant diseases and sampling methods were eliminated. As a result, 5 volatile lung cancer markers with better prospect of medical application were determined.2. A non-linear discriminant model (NLDM) were proposed, which contributed to optimization of the electronic nose design.We designed a hybrid electronic nose system (HENS) before. The detection units of HENS consist of metal oxide semiconductor sensors and surface acoustic wave sensor. In total,138 feature values could be extracted from responses of detection units. In the present research, an NLDM algorithm was developed to analyze the multivariate data. For clinical diagnosis of different patient, physicians often take different factors into account. Using that for reference, when analyzing a certain breath sample, NLDM determines which feature values could enter the model by assigning different diagnostic importance to each value. Comparing with artificial neural network (ANN) used in HENS before, NLDM shows better discriminant capacity and low complexity.3. To our knowledge, it is the first time that combination of carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC) and neural specific enolase (NSE) has been measured in exhaled breath condensate (EBC). In addition, it has been proved they can be potential markers in early lung cancer.A modified EBC collecting device was used, which made it possible to collect proteins with large molecular weight.105 lung cancer patients and 56 healthy subjects participated our study and donated their EBC. Chemiluminescence immunoassay was used to detect concentrations of CEA, SCC and NSE in EBC. Fasting venous blood samples were collected from patients and healthy individuals for comparing studies. A significantly higher concentration level of each marker was found in lung cancer patients than healthy controls. Markers in EBC had a higher positive rate and were more specific to histologic types than markers in serum. Tumor markers in EBC may have a better diagnostic performance for LC than those in serum.4. Gold nanoparticle enhancement strategy is employed, which significantly amplified the sensitivity of Love-wave immunosensor for detection of tumor markers in exhaled breath condensate.Coating antibodies are immobilized onto the sensitive area of Love-wave sensors through protein A. Markers to be detected are captured by coating antibodies. The specificity of immunosensor results from the specific recognition between antibody and antigen. In addition, the detecting antibodies are labeled by gold nanoparticles. A "sandwich" immunoassay is performed on a Love-wave sensor. Subsequently, gold staining solution is introduced, which results in catalyzed deposition of gold (III) on to the gold nanoparticles. The deposition amplifies the mass loading on immunosensor and makes it possible to detect tumor markers in EBC. The limits of detection (LODs) are 0.967ng/ml for CEA detection,0.663ng/ml for SCC detection and 1.598ng/ml for NSE detection, respectively. Considering those LODs of the measurement system are lower than the corresponding cut-off values, the described Love-wave immunosensor has potential to detect lung cancer in clinic.5. A detecting instrument was designed for detecting of exhaled breath condensate, and a software running on iPad was developed, which implement real-time detection of tumor markers in EBC.We designed an instrument to detect responses of the above Love-wave immunosensors. Automatic inject system, control circuit and mobile software were developed to implement mechanized detection which could reduce The experimental error brought about by manual operation. Simultaneously, remote monitoring of detection procedure and data-sharing among multi-platform have been achieved. The detection results of sensors measured by the present instrument is consistent with those measured by commercial network analyzer. Additionally, it was applied to detection of EBC sampled from 17 lung cancer patients and 13 healthy participants. The results showed that higher levels of CEA, NSE and SCC could be detected in EBC of patients than in EBC of controls, which suggests the promising application of this instrument for early detection of lung cancer. |
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