Construction Of Ultra-sensitive Electrochemiluminescence Sensors Based On Carbon Nanomaterials And Signal Amplification Technology

In recent years,electrochemiluminescence（ECL）sensor has played an important role in food safety monitoring and early diagnosis of diseases because of its advantages such as simplicity,rapidity,high sensitivity and strong controllability.However,the following challenges still exist in the construction of highly sensitive ECL sensors:（1）the preparation of ECL luminescent materials mostly relies on expensive raw materials,and it is urgent to develop green,economic and environmental friendly luminescent materials;（2）The constructed ECL sensor has a relatively low detection sensitivity and is difficult to be used for the detection of trace substances;（3）Multiple luminaries used in single-step ECL sensor for detection of multiple objects are prone to cross influence,which reduces the detection performance of ECL sensor.In order to solve the above problems,this paper prepared economical,environmental friendly and efficient ECL luminescent materials,simplified the preparation steps of the sensor,and realized the one-step rapid detection of the target object In addition,we combined the nucleic acid signal amplification strategy to construct a new single-step ECL sensor for the detection of multiple targets,effectively avoiding the possible cross-reaction between multiple luminescence and improving the detection performance of the sensor.The specific content is as follows:Part 1.Rapid,ultrasensitive and non-enzyme electrochemiluminescence detection of hydrogen peroxide in food based on the ssDNA/g-C₃N₄ NS nanosheets hybridssDNA/g-C₃N₄ NS have strong catalytic activity.However,the application of ssDNA/g-C₃N₄NS in ECL is rarely reported.To this end,we have established a new non-enzymatic ECL sensor based on ssDNA/g-C₃N₄NS nanocomposites for the detection of hydrogen peroxide（H₂O₂）in food.The ssDNA/g-C₃N₄ NS nanocomposite was prepared by simply mixing g-C₃N₄ NS and ssDNA solution,and modified on the glassy carbon electrode to catalyze the luminol-H₂O₂ECL reaction.The prepared nanocomposite material can effectively improve the activity of peroxidase and increase the rate of the oxidation reaction mediated by H₂O₂,thereby effectively amplifying the ECL luminescence signal.Under the best conditions,the designed sensor exhibits high sensitivity,and the limit of detection（LOD）for H₂O₂ is as low as 33 a M,which is much lower than most reported methods.In addition,the ECL sensor can quickly detect and measure H₂O₂ in fresh milk within 1 minute（min）,which has great market application prospects.Part 2.DNA walker-based“off-on-off”electrochemiluminescence biosensor for ultrasensitive detection of dual cancer micro RNA biomarkersDNA nanomachines based on DNAzyme have also been widely developed for tumor marker detection due to their excellent nucleic acid signal amplification,low cost,easy design,and simple operation.However,when a single-step ECL sensor is used for multiple target detection,the luminophore used is prone to cross-reaction,which affects the detection performance of the sensor.In addition,DNA nanomachines based on DNAzyme are rarely used for multiple target detection.This chapter proposes an ECL sensor based on"off-on-off"DNA nanomachines that uses a single ECL tag to detect two types of Micro RNAs（miRNAs）.First,the DNA nanomachine on the electrode is prepared by functionalizing gold nanoparticles（AuNPs）with hundreds of substrate chains,dozens of capture chains（CP2）,and dozens of locked DNAzyme chains.The carbon dots（CDs）are loaded on the substrate chain as ECL luminescent reagents（CDs-DNA walker）.In the presence of miRNA-21,CDs-DNA walker is connected to the modified electrode through the specific nucleic acid hybridization between miRNA-21,CP1 and CP2 to form a sandwich structure to generate a specific ECL signal corresponding to miRNA-21（signal"On"）.In the presence of miRNA-155,the DNAzyme chain on the DNA nanomachine is activated,and with the assistance of Mn2+,the DNAzyme chain specifically recognizes the r A base on the substrate chain and cuts it off,so that the CDs are separated from the electrode,and the ECL signal is greatly reduced（signal"Off"）.The sensor combines the advantages of DNAzyme nucleic acid signal amplification strategy and ECL analysis technology itself,so that the LOD of the target miRNA-21 is 33 f M,and the LOD of miRNA-155 is 33 a M.In addition,compared with the standard q RT-PCR method,this method has the advantages of low cost,simple design,and simple operation.The single-step ECL sensor is used for the detection of multiple targets,effectively avoiding the possible cross-reaction between the occurrence of multiple luminophores,improving the detection performance of the sensor,and providing a single signal label for the development of DNA nanomachines New ideas and directions.