Novel Colorimetric Sensors Based On Hydrogels And Artificial Enzymes

Colorimetric sensors are an important part of biosensors.The signal of most colorimetric sensors mainly relies on the naked eyes to conduct semi-quantitative detection on the color shades.However,similar color can easily lead to misjudgment of test results.Therefore,how to improve the accuracy of traditional colorimetry has always been an important scientific problem for researchers.Distance is a signal on accurately quantifying,such as thermometers,by observing the height of the liquid column.Besides,the easy inactivation of natural enzymes also restricts the quantitative detection of colorimetric sensors.In view of this,combines the colorimetric reaction with gel to construct a colorimetric sensor in this paper.The colorimetric results are presented in the form of distance in the gel.At the same time,we synthesized a series of inorganic materials to construct a colorimetric sensor and used it for the inhibitor and activity of alkaline phosphatase detection.The mainly works are as follows:1)3D gel colorimetric sensor was designed by using acrylamide gel.We use glucose,glucose oxidase,horseradish peroxidase and a blue dye to produce free radicals in a cascade reaction,which then initiates the polymerization of liquid acrylamide to form a solid three-dimensional gel.At the same time,the color of the blue dye changes in the gel,and the color changes in a distance from the outside to the inside.The change of distance was linearly correlated with the amount of glucose added.The quantitative detection of glucose was realized by observing the distance of the change of color.The lower limit of glucose detection was about 1 m M,and the detection interval was about 1.4-60 m M,demonstrating good specificity.In addition,we also studied the reason of the variation of distance in the gel.The 3D gel sensor is simple to prepare and can be mixed with each component.Detection can be achieved by visual observation of phase changing and reading of the changing distance on color,directly.It is suitable for resource-poor or limited conditions,including remote villages,home health care and emergency situations.2)In the previous chapter,the 3D gel colorimetric sensor has some defects.For example,the operation that all liquid components need to be fully mixed is still not conducive for portable.The lower limit of glucose detection is about 1 m M,and its detection sensitivity needs to be further improved.We further simplified the operation.Glucose oxidase,horseradish peroxidase and dye were loaded into agarose gel in advance.After glucose was added,the color the of the dye also changed in distance.At the same time,we experimented with various dyes and obtained a readout of multiple signals simultaneously.Therefore,a simple colorimetric sensor was proposed and used in urine glucose detection.It is easy to operate,the signal output mode is intuitive and the form is various,and it is expected to develop a portable detection system.3)A novel colorimetry sensor for screening alkaline phosphatase（ALP）inhibitors was constructed by combining the traditional colorimetric with the oxidase properties of manganese dioxide（Mn O₂）nanosheets.In this chapter,we have carried out a series of characterization of Mn O₂,proved that Mn O₂nanosheets can be degraded by ascorbic acid,and also proved that they have good stability in different p H environments.After the addition of inhibitors,the activity of ALP was inhibited,and the Mn O₂nanosheets could normally oxidize the substrate,which realized the purpose of screening ALP inhibitors by colorimetric.The experimental conditions were optimized,and the detection performance was tested（including linearity and anti-jamming ability for complex samples）.It is proved that the sensor can be used as a platform for detection of ALP inhibitors,which can realize the unlabeled,low-cost,intuitive and specific screening of ALP inhibitors.4)We further synthesized new Mn-hemin MOF material on the basis of Mn O₂nanosheets in the last chapter by hydrothermal.The material was characterized in a series of ways and its acid and alkali resistance was evaluated.Results shows that MOF also has strong oxidizing,which can oxide the chromogenic substrate directly without addition of hydrogen peroxide.This property can alleviate the toxic effect of hydrogen peroxide on biological enzymes.At the same time,we designed a new colorimetric sensing method based on Mn-Hemin MOF material for the detection of alkaline phosphatase activity.The detection of ALP based on Mn-Hemin MOF material is quickly and efficiently,and has no interference with the enzyme,which can be an effective tool for clinical diagnosis and drug screening.