Able to detect chemicals present in very low concentration in the breath, the electronic noses allow diagnosing lung tumors still early in its evolution.
The team Hossam Haick, the Technion, Haifa, Israel, has developed an electronic nose, based on gold nanoparticles, which could serve as a diagnostic test for cancer of the lung. This nanoreceptor breath detects minute quantities of small carbonaceous molecules, the volatile organic compounds (VOCs), whose quantity changes in people who suffer from this type of cancer. An early detection of lung cancer – the leading cause of cancer mortality worldwide with 900,000 deaths per year and less than 15% survival at five years – theoretically increase the chances of cure or survival of patients, the treatment still less late.
Differences in concentrations of VOCs are not artifacts. In fact, carcinogenesis – is also the case with other pathologies – is accompanied by a different cellular metabolism, particularly the production of free radicals that degrade fatty acids of cell membranes (peroxidation). This degradation leads to alkanes such as ethane and pentane, which are excreted in the form volatile exhaled air, or the sweat and in urine (researchers from Monell Chemical Senses Center in Philadelphia (USA) announced on 2008, have detected so skin cancer)). For other compounds, the concentration tends to decrease, because normal cells consume a greater amount.
H. Haick and colleagues evaluated a system miniaturized and ultrasensitive diagnostics of lung cancer. Initially, raised the breath of 40 patients with advanced cancer, and 56 healthy volunteers. To avoid any external contamination, participants minutes breathed through a filter that retained organic compounds from the air. Hence, researchers became visible 42 molecules representing biomarkers of lung cancer: they appeared, in fact, at least 83 percent of patients, but less than in healthy people, and its abundance in breath was modified. It was already known VOC 83 – alkanes such as styrene and toluene, or benzene derivatives – and nine new OVC hitherto never identified in the exhaled air and specific patient, such as metiloctano and dimetilhexano.
Subsequently, researchers have devised an array of nanocaptores capable of reacting biomarkers shown at 42, with a detection limit of 1-5 microliters per liter of air. These sensors comprise nanopartículças gold functionalized, ie, on which are grafted various thiols (decanotiol, butanethiol, hexanotiol, etc.), Chemical groups that can react with VOCs. When the volatile compounds therein are fixed, the electrical resistance of the sensor is modified to form a unique signature, according to the combination of compounds thus detected.
This electronic nose would apply to early diagnosis of lung cancer? The results of the Israeli group are not enough to say, patients who were enrolled in the study with advanced cancer, only clinical trials confirm. Anyway, their effectiveness on the decline of mortality and its cost should be compared with those of low-dose thoracic scanner. This is the only method of screening ongoing rigorous clinical trial (NELSON randomized trial, coordinated by Rob van Klaveren, Rotterdam (Netherlands), that are expected to brief the intermediate results, and the National Lung Screening Trial, the United United, whose initial findings will appear in 2010).
However, in daily clinical practice, there is no doubt that now enables the scanner to detect cancers of few millimeters, and it allows better treat them, says Christian Brambilla, director of the Institute Albert Bonniot in Grenoble (France) – (Inserm U823 , University Joseph Fourier). But you need to consider the diversity of cancers of the lung and the fact that other tumors “field characterization” tobacco-induced airway are often hidden and can prove deadly when lung cancer has been cured himself. Ultrasensíveis techniques such as electronic noses, able to differentiate different types of cancer may therefore prove to be useful and complementary.
PLScience (Translation MIA).