Construction Of Electrochemiluminescent Sensor And Applications In Biological And Medical Analysis

Electrochemiluminescence（ECL）is the emission process of specific luminophor excitated by electrochemical redox reaction.As an emerging analytical technique,ECL possess several advantages of low backgourd signal,high sensitivity,wide linear range,less equipment requirements and easy operation,and has been widely used in environmental monitoring,food safety and clinical diagnosis field.The ECL assay has become a common analytical platform for sensing biomarkers to diagnose a variety of serious diseases in clinical practice.However,the detection limit of traditional ECL assay are unable to satisfy growing requirement for the quantitative detection of targets with low concentration or targets exist in complex martrix.Therefore,in this paper,the advantageous nucleic acids-based signal amplification strategies and efficient ECL emitters were designed to construct the novel ECL biosensor for biological and medical sensing.1.Dual signal amplified electrochemiluminescence biosensor for ATP detectionDeveloping reliable and sensitive detection methods for adenosine triphosphate（ATP）is vital for both clinical diagnosis and food safety.In this work,by coupling aptazyme-and catalytic hairpin assembly（CHA）-based amplification process,a cascaded signal amplification strategy was obtained.The aptazyme-triggered cleavage of the DNA substrate and the CHA reaction both led to the circular release of trigger DNA,resulting in a significant dual signal amplification,with unprecedented enhancement up to 940-fold.Then,an ultrasensitive biosensor for sensing ATP was fabricated using Ru（bpy）3²⁺-doped silica nanoparticles（Ru Si O2）as ECL probes and a ferrocene-functionalized hairpin（hairpin-Fc）as quencher.Moreover,the bioconjugation of the DNA substrate with Au@Fe3O4 facilitated the separation and purification of the released trigger DNA,and effectively reduced the background signal.As a result,the as-prepared ECL biosensor exhibited a much wider linear range of 0.1-1000 p M,and a much lower detection limit of 0.054 p M for ATP compared to those in previous reports,and showed high reliability for ATP detection in both spiked serum samples and Staphylococcus aureus.This work offers a new perspective for designing nucleic acid-based signal amplification for detecting ATP in bacterial analysis and clinical diagnosis.2.Dual functional self-enhanced electrochemiluminescent nanohybrid for label-free micro RNA-21 detectionIn this work,a one-pot co-condensation strategy was proposed for the systhesis Ru（bpy）3²⁺and DEAMTES co-dopped Si O2 nanoparticles（DEAMTES@Ru Si O2）.Owing to the shortened mass and electron transfer distance between ECL emitter and coreactant and the limited energy loss,ECL efficiency of DEAMTES@Ru Si O2 was strengthened,which was 4.3-fold and 3-fold higher than Ru（bpy）3²⁺/TPA and Ru（bpy）3²⁺/DEAMTES in the traditional ECL pathway,respectively.On the other hand,the film-forming ability of DEAMTES@Ru Si O2 was enhanced with the help of both the physical adsorption of Si O2 on the electrode surface and the hydrogen-bonding interaction between DEAMTES and electrode.Furthermore,by coupling the CHA-mediated strategy with amplification factor of 175.5 and dual functional ECL emitter,a sensitive and selective label-free ECL biosensor for detecting mi RNA-21 was constructed.The proposed biosensor shows a wide linear range of 0.01-1000 p M with a LOD of 8.19 f M,and exhibits promising sensing performance for spiked serum samples.3.Preparation and characterization of copper nanocluster based efficient ECL emitterThe ECL emitters with the features of high efficiency,low-cost and easy preparation are urgently needed.In this work,the 4,6-Dimethyl-2-mercaptopyrimidine（DMPM）protected copper nanocluster（DMPM-Cu NCs）was first synthesized by using DMPM as both reductant and stabilizer.The self-assembly of DMPM-Cu NCs was launched by dispersing DMPM-Cu NCs into aqueous solution,producing a large quantity of well-defined nanosheets（SA-DMPM-Cu NCs）.The self-assembly behavior,which was possibly driven by the intercluster cuprophilic interaction andπ-πinteraction,endows SA-DMPM-Cu NCs with 15.1-fold enhanced luminescence and significantly improved stability compared to DMPM-Cu NCs.Most importantly,the ECL efficiency(Φ_ECL)of SA-DMPM-Cu NCs in the coreactant-type ECL reaction was remarkably promoted,which was calculated to 39%,an equivalent level to the best noble metal nanocluster-based ECL emitters in previous reports.In present work,the advantageous strategy to impove the FL,ECL effiencicy and stability of copper nanocluster was firstly proposed,and an effiecient,inexpensive Cu NCs-based ECL emitter was obtained,which would pave the way for the application of metal nanocluster in ECL and the further establishment of low-cost ECL assay.