Research On Electrochemiluminescence Sensorbased On Novel Inorganic Luminophore And Signal Amplification Strategy

Electrochemiluminescence(ECL),as a branch of electrochemical technology,is a simple,efficient and sensitive analysis method in analytical chemistry research field,which can quickly realize quantitative analysis of biomolecules,micro RNAs(mi RNAs)and drugs.ECL combining the advantages of electrochemistry and chemiluminescence is an important detection method with low background signal and high sensitivity,and has been widely used in clinical disease diagnosis,drug detection,food safety,environmental monitoring,pathogenic microorganism research and other fields.ECL is a kind of light emission process,which is generated by the oxidation or reduction of luminophores on the surface of the electrode.Luminophores play a key role in the construction of the ECL sensors.Although classical ECL materials(luminol,ruthenium complexes,quantum dots,noble metal nanoclusters)have been widely studied and applied,they still have the following problems:(1)The synthesis process is complex,the yield is low and the cost is high;(2)some luminophores have to be at a high potential to produce a strong ECL emission.Nevertheless,the high potential will cause the emission of oxygen in the electrolyte and damage the modified electrode and target,which greatly limits the practical application;(3)the luminophores may fall off the surface of electrode and cause the signal loss during the detection process,resulting in poor stability;(4)How to achieve the direct ECL emission of lanthanides.In recent years,a series of nucleic acid signal amplification strategies and DNA nanomachines have been widely used in ECL sensor to further improve the sensitivity of the sensor and achieve the purpose of trace or even trace detection of the target.Based on the above,novel inorganic luminophores were also synthesized.then,a highly sensitive ECL sensor is constructed for trace detection of target with the help of nucleic acid signal amplification strategies and DNA nanomachines,which provides a robust pathway for new ECL luminophore in analysis.The research contents are listed as follows:(1)Multiplexed electrochemiluminescence resonance energy transfer and target recycling amplification technology utilized in a three-dimensional DNA nanomachine based biosensor for electroanalysisTris(4,4?-dicarboxylicacid-2,2?-bipyridyl)ruthenium(II)dichloride(Ru(dcbpy)₃²⁺),as a classic inorganic luminophore,has some shortcomings in the construction of sensors,such as difficult modification and unstable luminescent signal.In this work,a novel electrochemiluminescence(ECL)biosensor was fabricated by a three-dimensional(3D)DNA nanomachine,which induced by Pb²⁺dependent DNAzyme assisted target recycling amplification technology and multiplexed ECL resonance energy transfer(ECL-RET)system.At the same time,Ru(dcbpy)₃²⁺was linked to the 3D DNA nanomachine probe via amide bond,which prevented the luminophore falling off of the electrode during the detection process,and improved the stability of the sensor.In the present of Pb²⁺,the substrate sequence of the DNAzyme was cleaved,resulting in that trace target was transduced to a large number of secondary target(A3).Afterward,A3 was employed to hybridize with the probe of 3D DNA nanomachine,triggering the movement of the nanomachine and forming the multiplexed ECL-RET system.In this multiplexed ECL-RET system,alexa fluor(AF),served as an effective energy transfer donor,which can transfer energy to Pt NCs and Ru(dcbpy)₃²⁺directly.Meanwhile,Pt NCs,both as the acceptor and donor,can accept energy from AF and transfer it to Ru(dcbpy)₃²⁺.As a result,the biosensor achieved high ECL efficiency,which was 1.78 times than that of the classic luminophore tris(2,2?-bipyridyl)ruthenium(II)dichloride(Ru(bpy)₃²⁺).Also,the proposed biosensor exhibited good sensitivity for mi RNA-141 detection with the line range from 1.0×10^-17 mol·L^-1 to 1.0×10^-8 nmol·L^-1,and the low limit of detection was 3.3×10-¹⁸ mol·L-¹.(2)A novel luminescent nanostructured coordination polymer:facile fabrication and application in electrochemiluminescence biosensor for electroanalysisIn the previous chapter,we introduced Ru(dcbpy)₃²⁺onto the electrode surface through the amide bond.However,due to chemical reaction conditions,its load is limited.Therefore,how to make Ru(dcbpy)₃²⁺into an insoluble luminophore and fix it on the surface of the electrode,how to improve its ECL intensity and efficiency,and reduce the potential scanning range are the key to construct the ECL sensor.A series of novel luminescent nanostructured coordination polymers(Ce-Ru-NCPs)with tunable morphologies have been successfully synthesized on a large scale at room temperature by a facile and rapid solution phase method using Ce³⁺and tris(4,4?-dicarboxylicacid-2,2?-bipyridyl)ruthenium(II)dichloride(Ru(dcbpy)₃²⁺).Among them,the flower-like Ce-Ru-NCP shows good cathodic electrochemiluminescence(ECL)characteristic.The ECL efficiency of Ce-Ru-NCP/S₂O₈^2-system is about 2.3 times that of the classic tris(2,2?-bipyridyl)ruthenium(II)dichloride/S₂O₈^2-(Ru(bpy)₃²⁺/S₂O₈^2-)system.The potential sweep range of Ce-Ru-NCP(0--0.9 V)is narrower than that of traditional cathodic luminophores,such as quantum dots,metal nanoclusters,tetraphenylethene derivatives,Ru(bpy)₃²⁺and so on.On the other hand,we combined two one-legged 3D DNA walkers together to form a bipedal 3D DNA walking machine to further improve the sensitivity of the sensor.Through the bipedal 3D DNA walking machine,trace targets can be converted to substantial secondary targets(marked with the quencher dopamine),and a significant quenching effect on ECL signal will be achieved.As a result,the proposed biosensor exhibits relatively good sensitivity for mi RNA-141 detection.The line ranges were 1.0×10^-16–1.0×10^-6 mol·L^-1,respectively.The low limits of detection(S/N=3)were at 3.3×10^-17 mol·L^-1.The Ce-Ru-NCP with tunable morphologies and high ECL efficiency,intensity and stability as well as the bipedal 3D DNA walking machine with high sensitivity,possesses potential applications in ECL analysis.(3)Multi-functional electrochemiluminescence aptasensor based on resonance energy transfer between Au nanoparticles and lanthanum ion-doped cadmium sulfide quantum dotsThe previous system study found that lanthanides(Ce³⁺)can improve the luminescence performance ofCe-Ru-NCP.This is mainly due to the unique optical properties of lanthanides,such as high quantum yield and long luminescence lifetime.Therefore,how to introduce lanthanides into the luminophore to improve the ECL intensity and lifetime is the main content of this chapter.In this work,a new type of inorganic luminophore(Cd S:La QDs)was synthesized by doping La³⁺into cadmium sulfide quantum dots(Cd S QDs).Cd S:La QDs possess high ECL intensity(signal on),which is 5 times that of traditional Cd S QDs.To verify the application of the new luminophore in sensor,a distance-dependent ECL intensity enhanced or quenched system between Cd S:La QDs and gold nanoparticles(Au NPs)was designed.In the presence of Hg²⁺,the oligonucleotide conformation changed from linear chain to hairpin due to the thymine–Hg²⁺–thymine(T–Hg²⁺–T)base pairs.ECL quenching(signal off)achieved lie in resonance energy transfer(RET)between the Cd S:La QDs and the proximal Au NPs at a close distance.Finally,after being incubated with TB,a strong and stable TB–aptamer complex was generated,which led to the release of Au NP–ss DNA 2 conjugates.The ECL signal of the Cd S:La QDs was ultimately recovered(signal on again).The“on–off–on”approach was used to sensitively detect Hg²⁺and TB,respectively.The line ranges were 1.0×10^-12–1.0×10^-5 mol·L^-1 and 1.0×10^-16–1.0×10^-6 mol·L^-1,respectively.The low limits of detection(S/N=3)were at 3.0×10^-13 mol·L^-1 and 3.0×10^-17 mol·L^-1.Moreover,the ECL sensor exhibited high selectivity and good stability,and was successfully applied to the detection of TB in real sample.(4)A super-stability luminescent lanthanide metal organic gel utilized in electrochemiluminescence sensor for electroanalysis with a narrow potential sweep rangeMetal organic gels(MOGs),especially lanthanide MOGs,as a new type of porous soft-hybrid supramolecular materials have attracted widespread interest in various aspects due to their unique optical properties.In this work,we report a novel ECL emission(679 nm)lanthanide MOG(Tb-Ru-MOG),which has been synthesized by a simple and rapid method at room temperature.The experimental results show that Tb-Ru-MOG possess the properties of reversible mechanical response behavior,the acid resistance,alkali resistance,heat resistance and ultrasonic resistance.Interestingly,the ECL intensity only decreased2.0%and 0.1%after continuous scanning for 8000 s and storing at room temperature for three months.Compared with the classic system of Ru(bpy)₃²⁺/S₂O₈^2-,the Tb-Ru-MOG/S₂O₈^2-owns a narrower potential sweep range(0.00--0.85 V),more stable and stronger ECL signal.Inspired by the unique luminescence characteristics of Tb-Ru-MOG,the application in electroanalytical chemistry was identified by the ECL on-off response for epinephrine with a linear range from 1.0×10^-10 to 1.0×10^-3 mol·L^-1 and a detection limit of 5.2×10^-11 mol·L^-1.The results suggest that the as-proposed Tb-Ru-MOG will provide a robust pathway for new ECL luminophores in the area of sensors.(5)Novel and enhanced Tb PO4:Ce³⁺electrochemiluminescence probes based energy transfer and antenna effect:facile synthesized and used for biosensorDespite the recent surge in interest in ECL of lanthanide rare earth elements,research in this field is still in its infancy due to the low ECL intensity.In this work,we innovatively synthesized a series of Ce³⁺-doped Tb PO₄(Tb PO₄:Ce,here the molar ratio of Tb:Ce is 9:0,9:1,9:3,9:5,9:7,0:9 respectively)in different proportions through the mechanical stirring route and co-precipitation method at room temperature.Interestingly,the morphology of the self-assembled Tb PO₄:Ce underwent a change from nanowire to nanorod,to nanoflower,and finally to nanorod with the increase of Ce³⁺.Meanwhile,through the studying the ECL properties of this series of Tb PO₄:Ce,we found that the maximum ECL intensity was obtained when the doping ratio of Tb to Ce is 9:1.The ECL intensity enhancement is mainly attributed to the antenna effect,energy transfer between Tb and Ce,and coreactant(potassium persulfate).On the other hand,in order to verify the application of Tb PO₄:Ce(9:1)in electroanalytical chemistry,a simple and sensitive mucin1(MUC1)detection ECL sensing platform was constructed.As expected,the proposed ECL sensing platform showed good stability,acceptable selectivity and reproducibility and successfully achieved sensitive detection of MUC1 with a linear range from 1.0×10^-15 to 1.0×10^-8 mol·L^-1 and a detection limit down to 5.0×10^-16 mol·L^-1.Significantly,this work may pave a new avenue for the study of direct ECL emission of lanthanide rare earth and also provides a thought for the research of new ECL luminophores in the electroanalysis.