Construction Of Acrylamide-based DNA Gel Biosensor And Research On Visual Detection

This article aims to construct a biosensor with simple and rapid quantitative and visual detection capabilities.Based on the color effect of 3,3’,5,5’-tetramethylbenzidine（TMB）and the characteristic absorption spectrum at 652 nm of one-electron oxidation product of TMB（ox TMB）.The visual and quantitative detection of DNA,silver ions and ascorbic acid is realized.The specific content is summarized as follows:（1）Using polyacrylamide as the main body,synthesize a DNA-responsive smart hydrogel at room temperature,and use the quantitative relationship between the gel release and the target DNA concentration to achieve quantitative DNA detection.Through quantitative analysis of catalytic reaction,kinetic analysis of catalytic reaction,and gel encapsulation and release control experiments,the feasibility of gel biosensor was discussed in detail.The absorption spectrum of ox TMB produced by the TMB-H₂O₂system catalyzed by the release of HRP from the gel under different target DNA concentrations was detected by an ultraviolet-visible spectrophotometer,and the linear relationship between the absorption intensity of the system at 652 nm and the target concentration was obtained,and a linear curve was drawn.The theoretical detection limit is 10 n M,and the detection interval is 0-4μM.At the same time,using the photothermal effect of the blue single-electron oxidation product of TMB,the DNA quantitative detection read by a portable thermometer is realized.By discussing the influence of different irradiation time on the performance of the sensor,the feasibility of the temperature readout method for DNA quantitative detection was explored.The detection range of photothermal sensor is 0-4μM,and the theoretical detection limit is 7.8 n M.（2）The TMB bidirectional colorimetric"on-off"sensor was constructed to detect Ag⁺and ascorbic acid（AA）.Since Ag⁺can catalyze the oxidation of TMB in the solution to show blue color,ascorbic acid can reduce ox TMB to colorless TMB,the two-way colorimetric"on-off"sensor constructed in this experiment can quickly detect Ag⁺and AA in the same system.By discussing the influence of different temperature,p H and reaction time,the feasibility of using the same system to detect Ag⁺and ascorbic acid in two directions was explored.The experimental results show that within a certain range,the Ag⁺concentration has a good linear relationship with the change in the absorption value of the system at 652 nm,with a linear correlation coefficient of 0.9882;the AA concentration has a good linear relationship with the change in the absorption value of the system at 652nm,The linear correlation coefficient is 0.9887.The two-way colorimetric"on-off"sensor does not require complicated experimental procedures and expensive instruments,and provides theoretical and experimental support for exploring two-way colorimetric sensing strategies.