Application Of Fluorescent Metal Nanoclusters And Two-dimensional Graphene-like Substances In Fluorescent Biosensors

In recent years,the research of fluorescent biosensors has attracted the interest of many people in the field of analytical chemistry and biochemistry,andhas made in-depth studies.Fluorescent biosensors use fluorescence signals as detection means to determine and detect metal ions based on the peak position and fluorescence intensity.They have the advantages of simple operation,low cost,high sensitivity,and good selectivity.At present,it has become a hot research topic in the field of chemical sensors.In recent years,nanomaterials have played an important role in the field of fluorescent biosensors.In this field,fluorescent metal nanoclusters and two-dimensional graphene-like substances have been discovered and studied because of their special properties.With the development of science,people increasingly need fluorescent biosensors with high sensitivity,good selectivity,low cost,and no toxicity.Therefore,several fluorescence biosensors have been studied in this paper.The details are as follows:1.The fluorescence biosensor were briefly summarized,and the synthesis and application of fluorescent metal nanoclusters,graphene and two-dimensional graphene-like substances were introduced in detail.At the same time,the main content and significance of the paper are clarified.2.A novel method for label-free mercury(Ⅱ)ions(Hg2+)detection based on exonuclease Ⅲ-induced target signal recycling amplification using double-stranded DNA(dsDNA)templated copper nanoclusters(CuNCs)was described.The synthesis of CuNCs was based on a specific dsDNA template.In the hairpin structure single-stranded DNA(ssDNA)of dsDNA template,the middle stem of the ssDNA is hybridized,and each of the 3’ and 5’ ends of the ssDNA has three thymine(T)bases.In addition,the hairpin structure ssDNA has a prominent 3’ end and shows no activity against exo Ⅲ.However,in the presence of Hg2+ ions,a T-Hg2+-T mismatch sequence structure is formed,and the protruding 3’ end of the hairpin structure ssDNA becomes a blunt 3’ end.Exo Ⅲ digests the hairpin ssDNA and releases Hg2+ ions,allowing it toparticipate in the next cycle.The reduction of ssDNA results in no hybridization of dsDNA.Therefore,the fluorescence intensity of the system is significantly reduced.The CuNCs fluorescence sensor is simple,low cost,and easy to operate.This method was successfully applied to the detection of Hg2+ in tap water.3.A simple and sensitive method for detecting heparin was established by using fluorescent CuNCs probed with dsDNA template.In the presence of copper ion(Cu2+),sodium ascorbate and dsDNA,CuNCs could be easily synthesized.After the introduction of N-rich protamine,the fluorescence intensity of CuNCs was significantly enhanced.However,the addition of heparin with a high negative charge density can form heparin-protamine complexes,thereby reducing the fluorescence intensity of the system.The method is simple,sensitive,selective,and low cost.This method was successfully applied to the determination of heparin in human serum samples.4.A new method for the determination of Hg2+ by fluorescence was designed.Among them,the carboxyfluorescein(FAM)is modified at the 3’ end of the ssDNA probe.After the introduction of tungsten disulfide(WS2),the labeled FAM fluorophore was adsorbed on WS2,and the fluorescence quenches due to resonance energy transfer of fluorescence energy.However,when Hg2+ is present,the T-Hg2+-T mismatch structure is formed due to the three T bases at each of the 3’ and 5’ ends of the ssDNA,and at the same time,the middle stem of the ssDNA is hybridized and the labeled FAM fluorophore is desorbed from WS2,so the fluorescence intensity of the system increases.The method has the advantages of simple operation,high detection speed and good selectivity.