| With the vigorous development of the global fruit industry and the upgrading of people's consumption structure,people are increasingly concerned about the monitoring of the nutritional quality of fruits and pesticide residues.However,traditional analysis methods mainly rely on sophisticated instruments and professional operations,which is difficult to people's demand for real-time and rapid detection on site.Therefore,the development of low-cost,convenient,efficient and user-friendly rapid detection methods for fruit nutrition and pesticide residues has very important theoretical and practical significance.Microfluidic Paper-based Analytical Devices(?PADs),as a chip laboratory with paper chips as its main sensing devices,has greatly promoted the miniaturization and integration of analysis laboratories with its remarkable advantages of low cost,no need of external driving force,high portability and environmental friendliness since it was put forward.Among them,?PADs based on colorimetry is widely used and reported especially in the fields of point-of-care,environmental monitoring and food on-site real-time detection due to visual visualization of detection results.However,there are few reports on real-time detection of multiple nutrients and pesticide residues in fruits based on?PADs.Therefore,it has certain potential value to construct a high throughput and high performance?PADs which can be used for on-site detection of multiple nutrients and pesticide residues in fruits.In this project,a biochemical detection system of zwitterionic polycarboxybetaine methacrylate(p CBMA)functional paper-based microfluidic chips(p CBMA-?PADs)combined with enzyme-chromogenic agent was successfully constructed and applied to the high-throughput rapid visual detection of multiple nutrients and pesticide residues in fruits.The main research contents are as follows:(1)In order to satisfy the high performance of detection in the real complex fruit system,p CBMA with super hydrophilicity and anti-protein adsorption performance was selected in this work.Using 2-bromoisobutyryl bromide(BIBB)as the initiator,the synthesized carboxybetaine methacrylate monomer(CBMA)was grafted and copolymerized onto a bare paper chip(Cellulose filter paper,CF)to prepare a p CBMA functional paper-based microfluidic chip(p CBMA-?PADs)by atom transfer radical polymerization method.In order to verify whether p CBMA was successfully modified on the surface of paper substrate,the experiment further carried out Fourier-infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),ink flow rate-time and sensing performance verification on the paper chips before and after modification.The results show that p CBMA is not only successfully modified on the CF surface,but also the hydrophilicity of the modified functional paper chip is greatly improved,and the specific response and sensing performance to the target are more sufficient and superior.At the same time,the hydrophobic reagent polydimethylsiloxane(PDMS)was used to build the hydrophobic substrate on the glass substrate,and then the functional paper-based sensing detection platform was assembled and constructed.(2)In this study,vitamin C,glucose,sucrose and fructose in fruits were first taken as the targets to be tested,and the constructed functional paper-based detection system was combined with target-specific enzymes and chromogenic agent to explore and optimize the experimental conditions of each target nutrient component,respectively.Under the optimal experimental environment,a standard curve was established according to the relationship between the target nutrient concentration and the mean relative intensity.The results showed that under the optimal detection conditions,there is a good linear correlation between vitamin C and the mean relative intensity in the concentration range of 0.1 m M?10 m M.The correlation equation is y=33.809+5.175x,R~2=0.993,and the detection limit(LOD)is 0.149 m M;and there is a good correlation between glucose concentration and mean relative intensity in the range of 2 m M to 100 m M.The correlation equation is y=-0.113+30.066*lg(x),R~2=0.988,and the LOD is as low as0.095 m M;In the concentration range of 6 m M?80 m M,there is a good linear correlation between the sucrose concentration and the mean relative intensity with its correlation equation is y=-5.334+34.858*lg(x),R~2=0.996,LOD=0.097 m M;In the concentration range of 0.0056 M to 0.1M,there is a good linear correlation between fructose concentration and mean relative intensity,and the correlation equation is y=4.996+23.325*lg(x),R~2=0.994,LOD=0.140 m M.Finally,the p CBMA functional sensing platform constructed above was applied to the rapid detection of nutritional components of 9 kinds of fresh fruit targets.Compared with standard methods,it has better accuracy and consistency.For further evaluate the practical potential of p CBMA-?PADs,the experiment further evaluated the nutrition of kiwifruit from different varieties and different origins.The results show that the portable multi-functional p CBMA-?PADs platform has potential application value in the rapid evaluation of fruit nutrition,and has certain practical guiding significance for food quality and nutrition evaluation in agricultural production and marketing.(3)To further improve the detection efficiency,reduce human error,and realize the intelligentization of the detection process and the scientification of the detection results,the experiment further designed a higher-throughput,automated and objective paper-based microarray detection system based on the automatic extraction strategy of digital image feature values.Then it was successfully applied to the rapid detection of pesticide residue chlorpyrifos.In the experiment,the automatic extraction method of image color feature value was successfully established with a series of density inks,and the method was evaluated and verified.Then the pesticide residue chlorpyrifos was rapidly detected by combining the enzyme inhibition principle.Under the optimal detection environment,there is a good linear relationship between chlorpyrifos concentration and characteristic color intensity in the concentration range of 0.1?g/L?100?g/L(y=74.296-28.098*lg C,R~2=0.986).Compared with the kit,the paper-based microarray sensing platform based on the strategy of automatic extraction of image feature values has not only excellent detection performance,but also timely and rapid analysis,which can realize batch processing in a short time and greatly promote the automation and intelligence of the detection process. |
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