Construction Of Enzyme-free And Labeled-free Biosensors For Food Safety Detection

Copper ion widely exists in environment and plays important roles for life,which can help to generate red blood cells and act as neurotransmitters and cofactor of various enzymes for physiological functions.However,abnormal amount of copper ion has significant negative effect on health of human being.Because of its non-biodegraded and remaining in ecological system indefinitely,it is important and necessary to develop accurate and sensitive strategy to monitor copper ion for human health.Antioxidants(TBHQ)can prevent or slow down the oxidation reaction and extend the shelf life of effect,but excessive add antioxidants will pose a threat to human health,can cause cancer and other serious consequences.In the present study,we found it for the first time that Cu2+ exhibits excellent peroxidase-like catalytic activity to oxidize non-fluorescent substrate of amplex red(AR)into product of resofurin with outstanding fluorescence emission under help of hydrogen peroxide(H2O2).Thus,an enzyme-free and label-free sensing system was constructed for copper ion detection with quite simple operation.To ensure.the detection sensitivity and reproducibility,the amount of H2O2 and incubation time were optimized.The optimum condition is 8 mM H2O2 and 7 h reaction time.This sensor displayed a linear response in the Cu2+ concentration range from 1-100 nM with a detection limit of 1 nM,the correlation was 0.996.In addition,the developed assay demonstrated excellent specificity and could be utilized to detect copper ion in water samples including tap water and bottled purified water with outstanding recovery values were found to vary form 97%to 120%and 105%to 120%respectively.The programmable property of DNA endows its powerful application in molecular computing.In our study,it is found that DNA exhibits excellent peroxidase-like activity on colorimetric system of TMB/H2O2/Hemin(TMB,3,3',5,5'-Tetramethylbenzidine)in the presence of K+ and Cu2+ while,which is significantly inhibited by antioxidant(TBHQ).According to the modulated catalytic activity of DNA-based catalyst,multiple cascade logic gates including AND-OR-INH,AND-INH as well as OR-INH have been successfully constructed.The optimum condition is 400 nM G-DNA,20 mM K+,40 ?M and 20 ?M Cu2+.At the same time,the sensor displayed a linear response in the TBHQ concentration range from 5-800 nM with a detection limit of 5 nM,the correlation was 0.998.