Engineering And Application Of The Smart Biosensors With High Sensitivity Based On DNA-templated Silver Nanoclusters

In the field of food safety,the sensitive detection of heavy metal pollution,the quantitative analysis of amino acids are important for human health.Copper ionis awidely used amicronutrient elementin biological systems.It is well known that Copper ions,ranks the third among the essential micronutrient elements in the human body,plays a significant role in metabolic processes.The copper ions intake of deficiency or overdose will cause the imbalance of homeostasis and cellular toxicity.As essential amino acid,Cysteine(Cys)and Histidine(His)have aroused great public attention due to their crucial roles in many biological functions such as protein synthesis,metabolism and detoxification.Either excessive or deficiency of Cys and His can cause serious diseases and greatly threaten public health.In our investigation,a series of smart biosensors have been constructed based on the DNA-templated silver nanocluster(DNA/AgNCs).DNA/AgNCs shows a low fluorescence emission at 560 nm and a strong fluorescence emission at 595 nm.In the addition of coppor ion,it was found that the emission intensity at 595 nm is significantly quenched,however,the emission intensity at 560 nm was enhanced.The copper ions can be detected by the ratio of F560/F595 of fluorescence intensity.TEM of DNA/AgNCs sizes,the DNA of GT15R as the sequence,is the 1.6±0.4 nm,the optimization buffer of PB pH is 7.4.The detection of copper ions can be selectively detected within concentration range of 5.0 nM-250.0 nM with a correlation coefficient(R2)of 0.96 and 250.0 nM-5.0 ?M with a correlation coefficient(R2)of 0.995,respectively.The copper ions can be specially detected by the ratiometric fluorescence biosensor,which indicates the perfect stability from 0 to 15 days.The recoveries of copper ions from tap water and lake water are between 93%-105%and 92%-110%,respectively,which recoveries are in agreement with the ICP-MS.Ratiometric fluoresent biosensor based on dual emission of DNA/AgNCs highly and sensitively detects the amino acid.Considering the strong interaction between His/Cys and Cu2+,it can form the complex of Cu2+/His or Cu2+/Cys.A ratiometric fluorescence biosensor for high sensitive and selective detection of His and Cys has been successfully constructed.The optimization concentration of copper ions is 1.0 ?M.The detection of Cys and His are range from 0.01-2.0 ?M with a correlation coefficient(R2)of 0.990 and range from 0.01-1.5 ?M with a correlation coefficient(R2)of 0.991,respectively.To individual detection His from Cys,the Ni2+ or N-ethylmaleinide(NEM)shows a corresponding recognized masking effect for His or Cys.The detection of Cys and His are range from 0.01-2.0 ?M with a correlation coefficient(R2)of 0.993 and range from 0.01-1.5?M with a correlation coefficient(R2)of 0.990,respectively.The bisosensor of ratiometric fluorescence can specially detect the Cys or His.