General Fluorescence Sensing Strategy For Functional Nucleic Acids Based On Energy Transfer Between DNA Silver Nanoclusters And Gold Nanorods

The residues of chemical contaminant such as pesticides,veterinary drugs,biotoxins,pathogenic bacteria and heavy metals commonly found in food and the environment have posed serious threats to the ecosystem and human health.Among them,the overuse of antibiotics in agricultural breeding and the accumulation of heavy metals in the environment have become increasingly serious.At present,the commonly used detection methods of antibiotics and heavy metals are expensive and complicated.Therefore,the development of simple,rapid and reliable methods for the detection of antibiotics and heavy metal residues in food and the environment is of great significance.DNA silver nanoclusters（DNA-Ag NCs）are easy to synthesize and have strong fluorescence and good stability.Therefore,DNA-Ag NCs have been widely used as a new label-free fluorescence probe in the field of analysis and detection.Gold Nanorods（GNRs）are widely used in biomedicine and food detection due to its simple preparation and rich chemical and physical properties.Combining the high sensitivity and selectivity of Functional acids（FNAs）with the surface energy transfer（SET）between DNA-Ag NCs and GNRs,using aptamer and deoxyribozyme as recognition elements,a simple,low-cost,universal and label-free fluorescence nucleic acid sensing strategy has been developed for the rapid detection of tetracycline and lead ions.The details are as follows:（1）DNA sequences complementary to tetracycline aptamer（TET Aptamer）were linked to five thymine spacers（T₅）and templates（C₆G₅C₆）to synthesize c DNA-Ag NCs.Based on the electrostatic adsorption capacity of positively charged GNRs to double-stranded DNA and the principle of SET between c DNA-Ag NCs and GNRs,a label-free aptamer fluorescence sensing strategy was developed to detect TET.When TET was present,TET specifically bound to TET aptamer.At this time,due to the low surface negative charge density of the single chain and weak adsorption of GNRs,c DNA-Ag NCs were released from the surface of GNRs,reducing the SET efficiency.The fluorescence of c DNA-Ag NCs in the detection system was restored.Under the optimal experimental conditions,the concentration of TET was linearly correlated with fluorescence intensity in the range of 5-500 n M,and the detection limit was 4.411n M.This method has been successfully applied to the detection of TET in milk samples,and the pretreatment process of milk samples is simple and rapid.It is a time-saving and efficient method,and can be extended to other target detection.（2）In this experiment,Pb²⁺-dependent GR5 deoxyribozyme（GR5 DNAzyme）was selected as the probe,the GR5 DNAzyme,composed of an enzyme chain（GR5 E）and a substrate chain（sub-C₆G₅C₆）connected to the template（C6G5C6）.Sub-C6G5C6was synthesized into DNA templated Silver nanoclusters（Sub-Ag NCs）.A label-free deoxyribozyme fluorescence sensor was developed to detect Pb²⁺based on the adsorption of GNRs with positive charge to sub-Ag NCs/GR5 double chain and the SET principle between Sub-Ag NCs and GNRs.In the presence of Pb²⁺,GR5 E specifically cleaved sub-Ag NCs to break them into two parts.The single-stranded DNA containing Ag NCs will be released from the surface of GNRs due to the low surface negative charge density,resulting in the reduction of SET efficiency.At this point,the fluorescence of Ag NCs recovered.Under the optimal experimental conditions,Pb²⁺was linearly correlated with the fluorescence intensity in the concentration range of 5-60 n M,and the detection limit was 1.416 n M.This method has been successfully applied to the detection of Pb²⁺in river water.This method has been successfully applied to the detection of Pb²⁺in the Songhua River water,which is simple,time-saving and efficient.