Rapid Detection Methods Based On The Photothermal Effect Of Nano Materials And Device Development

In recent years,the incidents caused by food safety problems have occurred frequently,which attracted wide attention of the public.Food safety issues are related to people’s life,therefore,it is necessary to establish rapid detection methods for pathogenic bacteria,pesticide and veterinary drug residues in food.Traditional detection methods are time-consuming,requiring large equipments,and the operation steps are complex.The test strip detection method is widely used in many fields such as food,biomedicine and environmental monitoring,which has the advantages of portability,fast,efficient,simple operation and low cost.The colloidal gold（GNPs）test strip has two types of immunochromatography test strip and dot immunogold filtration test strip.However,the traditional test strip detection method has low sensitivity and can only obtain qualitative or semiquantitative results.Therefore,the traditional test strip detection method has been improved in this study,the photothermal effect of nanomaterials has been combined with the test strip detection method,and the linear relationship was established corresponding to the different concentrations of the target analyte and the temperature change value.The propable test strip photothermal card reader device has been fabricated based on the above method,which has the advantages of simple operation,low cost,easy to carry,and has a broad application prospect.In this paper,our work include four parts.:the development of the rapid detection method based on the photothermal effect of GNPs;the fabrication of propable test strip photothermal card reader device based on the photothermal effect of GNPs;the dot immunogold filtration test strip based on the photothermal effect of GNPs for the detection of Salmonella typhimurium;and the dot immunogold filtration test strip based on the photothermal effect of black phosphorus for the detection of 17β-E₂.The results showed that this method can achieve rapid quantitative detection of the samples.Compared with the traditional method,it has the advantages of simple,fast,low cost and free of using expensive instruments.This work mainly consists of six parts,the content is as follows:In the first chapter,the detection methods and research progress of Salmonella typhimurium and 17β-E₂ were summarized.The principle,procedure and application of the test strip detection method were described.The research progress and application based on the photothermal effect of nanomaterials are introduced.In the second chapter,a rapid detection method based on the photothermal effect of GNPs was established,and applied to the detection of commercial GNPs immunochromatographic test strips.Clenbuterol hydrochloride and human chorionic gonadotropin were selected as the representatives of small molecule and large molecule respectively,and simple temperature sensor device was used for photothermal detection,which can significantly improve the sensitivity of detection compared with visual results.For the clenbuterol hydrochloride detection method,the visual detection limit was 6 ng·m L^-1,the standard curve of the simple temperature sensor detection method is y=0.4397x+0.2915,R²=0.9955,and the detection limit was 0.45 ng·m L^-1.The sensitivity of simple temperature sensor device detection method was 13-fold improvement than visual detection method.For the human chorionic gonadotropin detection method,the visual detection limit was 50 m IU·m L^-1,the standard curve of the simple temperature sensor device detection method is y=0.02127x+0.424,R²=0.9951,and the detection limit was 5.5m IU·m L^-1,the sensitivity of simple temperature sensor device detection method was about9-fold improvement than the visual detection method.In the third chapter,the portable test strip photothermal card reader based on photothermal effect of GNPs was fabricated.Based on the previous research of our group,the portable test strip photothermal card reader was completed by using infrared temperature sensor and laser irradiator.In the fourth chapter,the dot immunogold filtration test strip based on the photothermal effect of GNPs for the detection of Salmonella typhimurium was established.The detection area of the immunochromatography test strip is linear shape,which is not perfectly matched with the circular detection area of the portable test strip photothermal card reader,and the sensitivity does not achieve the best effect.In this chapter,owing to the round shape of the detection area of the dot immunogold filtration test strip,it is adopted to further improve the sensitivity of the detection method.The antibody of Salmonella typhimurium was coated on the nitrocellulose membrane,the non-specific adsorption was eliminated by blocking with bovine serum albumin（BSA）,and the synthetic GNPs-antibody complex was incubated with Salmonella typhimurium.Then the complex was added to the membrane for reaction.The more Salmonella typhimurium bacteria,the more GNPs-antibody complexes combined in the nitrocellulose membranes,and the temperature change would be greater,thus a linear relationship was established between the concentration of Salmonella typhimurium and the temperature changes.Then the antibody concentration of the labeled GNPs,the coating liquid and the blocking liquid were optimized.The visual detection limit and the photothermal detection limit based on the portable test strip photothermal card reader were tested.The results showed that the optimal antibody concentration of labeled colloidal gold is 1 m L GNPs added 48μL 50μg·m L^-1 antibody,the optimal coating liquid is 8%methanol,and the optimal blocking solution is 4%BSA.For the Salmonella typhimurium detection method,the visual detection limits and the portable test strip photothermal card reader device detection limits were 5.4×10⁶ CFU·m L^-1 and 4.1×10⁵ CFU·m L^-1,respectively.The sensitivity of the portable test strip photothermal card reader detection method was about 13-fold improvement than the visual detection method.In the fifth chapter,the dot immunogold filtration test strip based on the black phosphorus photothermal effect for the detection of 17β-E₂ was established.As a new type of nanomaterial,black phosphorus has excellent photothermal effect.In this chapter,black phosphorus is used as a marking material to further improve the sensitivity of the detection method.The principle of the method is that the nitrocellulose membrane is coated with 17β-E₂ antigen,the black phosphorus is coupled with the anti-17β-E₂ antibody,and the 17β-E₂ competes with the coated antigen for the binding site of the antibody,thus the quantitative detection can be achieved.Then the experimental conditions were further optimized.The experimental results showed that the optimal laser irradiation time is 80 s,the optimal laser irradiation power is 3.0 W·cm^-2,and the optimal p H of the black phosphorus labeled antibody is 7.5,the portable test strip photothermal card reader device detection limits for 17β-E₂ was 2 ng·m L^-1.The method has the advantages of simple operation and does not need large-scale instruments,which has a good application prospect.In the sixth chapter,the rapid detection method and device based on the photothermal effect of nanomaterials were summarized.The device can be applied to the test strip detection,and achieved the quantitative detection of the sample,which has the advantages of simple,rapid,low cost and does not need large-scale instruments compared with the conventional method.