Research On Paper-Based Pb(Ⅱ) Detection Assisted By Smartphone

Pb(Ⅱ)is a common heavy metal ion pollutant,which can cause serious harm to human health.Most of the existing Pb(Ⅱ)detection methods are complicated to operate,time-consuming,expensive,and dependent on large-scale instruments,and these methods are not suitable for on-site detection.Therefore,it is very urgent to develop a biosensor with simple operation,high sensitivity and strong specificity for the on-site detection of Pb(Ⅱ).Smartphones have built-in cameras,central processing units,and data storage space,with the capabilities of data analysis and processing as well as signal transmission,and give obvious advantages for analysis.Paper-based detection devices own the advantages of low price,user-friendliness and good biocompatibility,exhibiting great application potential in analytical field.In this dissertation,two new colorimetric biosensors are designed by using the advantages of smartphone and paper-based device for on-site detection of Pb(Ⅱ).The main research contents are given as follows:1.Study on paper-based colorimetric sensor for Pb(Ⅱ) detection based on G4 DNAzymeIn this part,we construct a simple,fast,and low-cost paper-based colorimetric sensor using 3D printing technology as well as the image capture and processing capabilities of smartphones.Pb(Ⅱ)can competitively bind the G-quadruplex induced by potassium ion and change its conformation,inhibiting the color reaction of TMB catalyzed by G4 DNAzyme.The whole color reaction process is carried out on the paper.Moreover,a cassette is prepared by 3D printing technology with the installion of an OLED light source and a mobile APP is develop to analyze the RGB value of the reaction results picture captured by a smartphone and process data to give the g value(color intensity).The g value is positively correlated with the concentration of Pb(Ⅱ)(R~2=0.9956),and the detection linear range is between 0.1 n M and 100 n M,with high selectivity for Pb(Ⅱ).The sensor has been successfully applied to detect Pb(Ⅱ)in various tea beverages and milk samples.In conclusion,the smartphone-assisted G4DNAzyme paper-based colorimetric sensor has the advantages of simple operation,low cost,high sensitivity and good specificity in the on-site detection of Pb(Ⅱ).It provides a new idea for the application of smart phone-assisted paper-based detection device in real-time detection.2.Research on paper-based microfluidics for Pb(Ⅱ) detection based on CRISPR-Cas12a systemIn this part,we combine a smartphone with a paper-based microfluidic chip to develop a simple and low-cost method for on-site detection of Pb(Ⅱ).In the presence of Pb(Ⅱ),G-rich DNA sequences can form G-quadruplex structures to inhibit the activation of the CRISPR-Cas12a system,thereby reducing the cleavage efficiency of ss DNA strands on the surface of gold nanoparticles.The surface-modified gold nanoparticles with ss DNA can be captured by the DNA nanoflowers in the detection area of the chip,resulting in a color change in the detection area due to the presence of gold nanoparticles.Using the mobile phone software to analyze the R/G value of the detection area,the concentration of Pb(Ⅱ)in the sample can be directly obtained.The linear detection range of the paper-based microfluidic chip is 0.1μM-10μM,which has been successfully applied to detect Pb(Ⅱ)in various milks.In conclusion,the smartphone-assisted paper-based microfluidic chip has the advantages of low cost,high specificity,strong anti-interference ability,and suitability for on-site detection.