Construction Of Biosensor Based On Luminol Electrochemiluminescence Nanomaterials And Nucleic Acid Signal Amplification Strategy For MicroRNA Detection

Electrochemiluminescence（ECL）technology has the advantages of high sensitivity,low background signal,low operating requirements and simple optical settings,which has attracted continuous attention and research in the field of analytical sensing.As a method with relatively high sensitivity in analytical detection,ECL technology has been widely used in life science research in recent years.At present,researchers’efforts to improve the sensitivity of ECL analysis can be summarized into the following two points:（1）exploring new ECL materials to increase their luminous intensity;（2）combining signal amplification strategies to achieve effective response to the target.Therefore,this thesis developed new types of luminol-based composites as ECL emitters and combined it with efficient DNA nanomachine nucleic acid signal amplification strategies to achieve sensitive detection of tumor marker.1.A brief overview of electrochemiluminescence technology and several different types of electrochemiluminescence reaction principles and applications are introduced in detail.This chapter reviewed the development of some nucleic acid detection methods and their applications in electrochemiluminescence biosensors.In addition,this chapter also introduced the related work of using luminol as ECL materials to construct biosensor to detect micro RNA-21.2.The ECL biosensor was constructed on the basis of amino-modified3,4,9,10-perylenete-tracarboxylic dianhydride/luminol（PTC-NH₂/Lu）nanocomposite as emitter and bipedal DNA walker signal amplification strategy for ultrasensitive detection of micro RNA-21（mi RNA-21）.The PTC-NH₂/Lu nanocomposite was prepared as signal tag viaπ-πstacking molecular assembly,in which amino-modified3,4,9,10-perylenete-tracarboxylic dianhydride（PTC-NH₂）as a novel co-reaction accelerator significantly enhanced the ECL emission of luminol-H₂O₂ system.Moreover,target mi RNA-21 triggered bipedal DNA walker was powered by toehold-mediated strand displacement reaction（TSDR）for signal amplification.Consequently,the proposed ECL biosensor achieved ultrasensitive detection of mi RNA-21 with linear range from 100 a M to 100 p M and the limit of detection is 33 a M.Simultaneously,the biosensor was also successfully applied to detect target mi RNA-21 in lysates from human cancer cells.As a result,this work constructed a new signal amplification platform,exhibiting great application potential in biomedical analysis and early clinical diagnostics.3.Herein,positively charged nanocomposites Lu/Mo S₂ QDs@ZIF-8 were prepared via the simultaneously immobilization of luminol and molybdenum disulfide quantum dots（Mo S₂ QDs）in metal-organic frameworks ZIF-8,where luminol and Mo S₂ QDs as luminophor and coreaction accelerator involved in ECL process,respectively.The abundant metal ions of ZIF-8 were demonstrated as relatively independent reaction sites to coordinate with luminol and the cavity skeletons distributed in ZIF-8 provided confined but dense space to embed Mo S₂ QDs.Therefore,the nanocomposites tended to immobilize plentiful luminophore and co-reaction accelerator,and accordingly,followed by more superoxide anions(O₂^·-)generated with an imposed voltage.In addition,the positively charged nanocomposites facilitated the enrichment of O₂^·-on the electrode surface and in cavities.The narrow cavities greatly reduced the accessible distance between O₂^·-and luminol,which significantly improved reaction efficiency of the ternary ECL system.Remarkably,the integrated nanocomposites achieved strong ECL phenomenon,and the calculated ECL efficiency was 12.7 times that of the luminol-H₂O₂ system,with a dramatic enhancement compared to traditional ternary systems in which the ECL efficiency has been reported could only be increased by 1.5to 4 times.What’s more,employing Lu/Mo S₂ QDs@ZIF-8 as emitter,an ECL biosensor was constructed on the basis of an endogenous ATP-driven signal amplification strategy achieving ultrasensitive detection of mi RNA-21 with the limit of detection low to 14.6a M.Not only provided a promising mi RNA-21 monitor platform for early clinical diagnosis of tumor,but more importantly this work also pointed out a universal path for improving the ECL efficiency which could apply to other ECL systems.