Application Of Visual Colorimetric Sensors For Detecting Exhaled Breath Disease Markers

Objective:The changes in the level of disease markers in human exhaled breath can dynamically reflect the metabolic situation of the body,through the detection of exhaled breath markers can assess the health of the human and assist doctors in disease diagnosis and early disease screening.Therefore,it is important to develop a low-cost,simple and efficient exhaled gas marker detection technology.Visual gas sensors are considered a promising method of non-invasive early disease screening due to their cheap,accurate,portable and visual characteristics.In this study,it is proposed to develop a visual gas sensor with high response to exhaled breath disease marker gases by means of visual colorimetric sensing technology to provide new methods and ideas for early disease screening and diagnosis.Methods:In this thesis,on the basis of strategy of combining colorimetric gas sensing materials with hydrogels,two visual colorimetric gas sensors were constructed by dissolving and embedding the sensing materials into the hydrogels.Using the colorimetric sensor to different concentrations of gas response value to achieve the detection and analysis of the target gas,thereby assisting doctors in the early detection and diagnosis of disease.Result:In this thesis,based on the excellent moisture resistance of hydrogel and the obvious color response of colorimetric sensor material to target gas,two visual colorimetric gas sensors are constructed,which are respectively used for the detection of oral disease marker gas of H₂S and diabetes marker gas of acetone.The main content consists of the following two parts:（1）The preparation of visualization gas sensor based on Copper（II）-based pyridinediazonaphthol hydrogel and its application for the detection of H₂SIn this experiment,a visual colorimetric gas sensor was constructed based on Copper（II）-based pyridinediazonaphthol（Cu-PAN）hydrogel,the sensor is mainly composed of Cu-PAN complex and agarose hydrogel.Using Cu-PAN complex to detect H₂S gas is a new rapid optical detection technology.Agarose hydrogel has a micro-droplet environment,which can be used as a humidity buffer and regulator in the colorimetric sensing system to improve the resistance of the sensor to humidity interference.In addition,it helps to capture and convert acidic H₂S gas into S^2-,improving the sensitivity of the Cu-PAN hydrogel to H₂S.The experimental results show that the prepared Cu-PAN hydrogel visualization colorimetric gas sensor shows good linearity in response to H₂S gas,and good selectivity and stability.Besides,the feasibility of the Cu-PAN hydrogel sensor in actual halitosis diagnosis was successfully verified by exposing it to simulated breath containing traces of H₂S and other interfering gases,providing a new way and an effective candidate for the auxiliary diagnosis of oral diseases.（2）The construction of visual gas sensor based on composite hydrogel of methyl yellow dye and its application for the detection of acetone gasIn this work,a visual colorimetric acetone sensor with high sensitivity and selectivity was prepared by embedding hydroxylamine sulfate and methyl yellow dye in an acrylamide-agarose hydrogel.The formation of sulfuric acid from acetone and hydroxylamine sulfate causes the methyl yellow dye to change color.A smartphone digital camera was used to obtain the color signal of the hydrogel before and after the reaction to quantify the acetone gas concentration.The experimental results show that the visualized colorimetric acetone sensor exhibits an outstanding linearity relationship（R²=0.999）with different concentrations of acetone at room temperature.By exposing the visual colorimetric acetone sensor to the exhaled gas of simulated diabetic patients for detecting acetone.The results showed that the visual colorimetric acetone sensor could reliably detect the exhaled acetone.The sensor provides a new method for the specific detection of diabetic exhaled acetone gas at room temperature.Meanwhile,it also provides a new idea and way to develop the next generation of inexpensive,high-performance,portable gas sensing devices.Conclusion:In this thesis,two visual gas sensors based on colorimetric sensing hydrogels were successfully constructed to achieve high sensitivity for the detection of H₂S and acetone gases at room temperature.It was shown that the micro-droplet environment and high hydrophilicity of the hydrogels enhanced the sensitivity of the colorimetric sensors and improved the moisture resistance of the sensors.It provides a new way and working basis for the visual detection of exhaled breath disease markers.