Study On Biosensing Analysis Based On Quantum Dot Electrochemiluminescence And Signal Amplification Technology

In recent years,the researchers make efforts to develop efficient biosensors for the sensitive detection of multiple biomarkers in the field of surface enhanced Raman spectroscopy,electrochemiluminescence,fluorescence,electrochemistry and photoelectrochemistry.Among them,ECL biosensors based on quantum dot has attracted more and more research interests in many biological assays due to their high sensitivity,wide detection range and low background signal.This article mainly explored the ECL biosensing method based on quantum dot probes and enzyme-assisted cyclic amplification techniques,and achieved highly sensitive detection of miRNA,CEA and ATP.This article mainly studied the following three aspects:1.We proposed an electrochemiluminescence biosensor based on target induced cycle amplification method and walker DNA technology to achieve sensitive detection of target miRNA.In the presence of target microRNA-21,a three-way junction structure was formed to trigger enzyme-aided multiple DNA amplification,and thus exponentially amplified triggers were generated.Then,the trigger DNA could hybridize with the blocking DNA on the electrode to release walker DNA,which specifically combined with the quantum dots?QDs?-DNA probe,and formed a recognition site for Nt.BbvCI.The movement of DNA walker is powered by the nicking endonuclease that cleaves specific QDs-DNA probe on the track.Thus one walker DNA can automatically cleave multiple QDs probes on the electrode during the movement,resulting in significantly amplified changes of ECL signal.On the basis of these results,an ECL aptasensor was fabricated and could be used in the sensitive and selective detection of mi RNA-21 in the range of 10 fM to 100 nM with a detection limit of 1.5 fM.2.A novel electrochemiluminescence biosensor based on enzyme-aided cycling amplification and DNAzyme-triggered DNA walker was designed to achieve highly sensitive detection of CEA.When the target CEA was combined with the aptamer,trigeminal DNA structures were formed under the action of primers and templates.The cleavage and cyclic amplification reactions were performed with the aid of enzymes,resulting in a large number of walker product chains,which contain the specific sequence of DNAzyme.When the DNA walker hybridized with the CdSe QDs signal probe on the electrode surface,and used a Pb²⁺-assisted DNAzyme as a driving force,the DNA signal probe was circularly cleaved,causing a significant decrease in the ECL signal of the QDs.The results show that the change of ECL signal has a good linear relationship with the logarithm of CEA concentration in the range from 1.0 fg/mL to 100 ng/m L,and the detection limit was 0.21 fg/mL.3.An electrochemiluminescence biosensor based on the double quenching effects of silver nanoclusters and multiple cycle amplification technique was proposed for sensitive detection of target ATP.When the target ATP binds to its aptamer,the hairpin DNA was opened and part of the sequence was exposed.Then the exposed sequence could bind with the template DNA,and achieve multiple cyclic amplification reactions with the help of polymerase and cleavage enzyme,generating a large sum of DNA sequences.At the same time,Ag NCs were synthesized in situ using DNA as a template,and Ag NCs-DNA was attached to the electrode in the presence of the generated DNA sequences.The ECL-RET between the Ag NCs with CdS quantum dots and the consumption of coreactants near the electrode surface led to double ECL quenching of QDs.The constructed ATP sensor has good linearity within a concentration range varying from 1.0 aM to 1.0 pM,reversible responsibility and high selectivity toward ATP with a detection limit of 0.27 aM.