Study On The Rapid Detection Of Heavy Metal Ions Based On Functional Nucleic Acids

The problem of heavy metals pollution has became extremely critical in China,which can cause environmental pollution and even threat human health.Though the traditional methods for the detection of heavy metals have excellent sensitivity and high accuracy,most of them fail to meet the requirement of real-time detection.Therefore,it is very important to development simple,rapid and high sensitive methods.Recent years have witnessed the rapid development of using functional nucleic acids（FNAs）as the molecular recognition.As the FNAs are stable,harmfulless and can be synthesized easily,they have displayed more superior characteristics than other biologic tools such as antibodies and enzymes.FNAs have been widely used in analytical testing field,thus research on them have attracted considerable attentions.In this paper,several new fluorescent methods based on FNAs for the detection of Ag⁺,Hg²⁺and Pb²⁺have been established and the major conclusions are summarized below:（1）Detemination of Ag⁺base on the aggregation of gold nanoparticles caused by silver-specific DNA（Ag-CC）,and its effect on the fluorescence of Rhodamine B（Rho B）.In this assay,Au NPs has excellent quenching properties which depending on its dispersed or aggregated status,dispersed Au NPs can greatly quench the fluorescence of Rho B and aggregated Au NPs has weak effect on quenching the fluorescence of Rho B.The optimal detection condition was determined as 250μL Au NPs,0.12 M Na NO₃,15n M Ag-CC and 8μM Rho B were contained in the sensing system of 500μL.Ag⁺could be selectively detected from 2.73 to 1500 ppb,with a detection limit of 2.73 ppb.（2）Detemination of Hg²⁺based on the aggregation of gold nanoparticles caused by mercury-specific DNA,and its effect on the fluorescence of Rho B.The optimal detection condition was determined as 200μL Au NPs,0.12 M Na Cl,20 n M Hg²⁺-specific DNA and 8μM Rho B were contained in the sensing system of 500μL.Hg²⁺could be detected from 2.16 to 1000 ppb,with a detection limit of 2.16 ppb.（3）A label-free fluorescence sensor for the detction of Pb²⁺and Hg²⁺based on integrate functional nucleic acids was developed.SYBR Green I（SG）interacted with different conformation nuleic acids will present different fluorescence intensity in the sensing system.The optimal detection for Pb²⁺detection was determined as 50 n M modified T30695 and 6μL of400×SG in the sensing system of 500μL and that for Hg²⁺detection was50 n M modified T30695 and 6μL of 400×SG.As a result,the Pb²⁺and Hg²⁺can be detected from 2.09 to 500 ppb and 1.14 to 300 ppb,with detection limits of 2.09 ppb and 1.14 ppb respectively.This study showed novelty in detecting Ag⁺based on C-Ag⁺-C hairpin conformation,determing Hg²⁺based on T-Hg²⁺-T and designing integrated functional nucleic acid for double targets detection.Limitations remain in that much effort should be carried out before those methods could be applied in pratical application.