Construction And Application Of Electrochemiluminescent Biosensor Based On Graphdiyne

Electrochemiluminescence（ECL）is a chemiluminescence produced under certain potential excitation.It not only combines the controllability of electrochemical,but also combines the high sensitivity of chemiluminescence.It has many advantages,such as wide linear range,low detection limit and low background signal.Graphdiyne is a novel carbon-based nanomaterial with narrow band gap,highπconjugation,three-dimensional porous structure and excellent electron transport properties.It has been widely used in catalysis,energy storage and other fields.However,there are few reports on graphdiyne in ECL sensing,and it needs to be further developed and applied in the construction of ECL sensor.In this thesis,graphdiyne is used as the emitter,carrier and catalyst of ECL biosensor,and the performance of ECL system is improved from the following three aspects.Firstly,the surface structural defects of carbon-based materials are regulated,such as doping N or other elements.Secondly,catalysts are used,such as metallic oxide,MOF derived metal materials,etc.Thirdly,DNA amplification techniques are applied,such as DNA walker,hybrid chain reaction（HCR）,etc.The main research contents are as follows:1.Electrochemiluminescence sensor based on graphdiyne quantum dots functionalized MOF-derived Zn O with self-enhancing effect for the detection of radical scavenging drugsGraphdiyne oxide quantum dots（GDYO QDs）,as derivatives of graphdiyne（GDY）,have excellent biological compatibility due to their active acetylene units.MOF-derived Zn O（M-Zn O）not only can enhance the capacity of GDYO QDs through the huge surface area,but also can be served as the co-reaction promoter.In addition,the ECL intensity of GDYO QDs@M-Zn O modified electrode is five times larger than that of GDYO QDs modified electrode.Moreover,since free radical scavenger drugs can reduce the ECL signal of GDYO QDs,a novel electrochemiluminescence sensor based on GDYO QDs@M-Zn O is constructed for the detection of free radical scavenger drugs.The sensors are used for the detection of free radical scavenger drugs such as troxerutin,vitamin C and metformin hydrochloride.The sensitivities,specificities,reproducibilities and stabilities of the sensors are excellent,indicating that the sensors have potential application in free radical scavenger drugs.2.An all-graphdiyne electrochemiluminescence biosensor for ultrasensitive detection of micro RNA-21 based on target tecycling with DNA cascade reaction for signal amplificationBased on AuNPs/GDY,GDYO QDs,combined with 3D DNA walker and hybridization chain reaction（HCR）amplification,an ultrasensitive ECL biosensor for detecting micro RNA-21（mi RNA-21）is constructed.As electrode substrate material,AuNPs/GDY can not only bond with the aptamer CP,but also enhance the conductivity of interface.In the presence of mi RNA-21,3D DNA walker is initiated,producing large amounts of double-stranded H1/H2 on the electrode surface.Subsequently,one end of H3 is attached to the electrode surface by complementary base pairing with double-stranded H1/H2.Meanwhile,the other end of H3 pairs with H4 complementally,and HCR cascades in succession.With the increase of mi RNA-21,3D DNA walker and HCR continuously operate,resulting in the gradual increase of ECL signal.This ECL biosensor demonstrates outstanding performance for the determination of mi RNA-21 and offers a new sensitive idea for clinical analysis of cancer biomarkers.3.The electrochemiluminescence sensor based on triazo-doped graphidiyne,MOF-derived Co/Ni@NC and annular DNA walker triple signal amplification for the detection of micro RNAMetal-organic framework（MOF）is microporous material composed of metal ions and organic ligands,which has large surface area and good catalytic activity,but still has some shortcomings such as poor electrical conductivity.In this study,Co/Ni@NC with larger surface area,better conductivity and OER catalytic ability is obtained by carbonizing ZIF-67@ZIF-8/Ni²⁺.Both Co/Ni@NC and triazo-doped graphidiyne（NGDY）can promote the generation of reactive oxygen species ROS,thus synergically enhancing the ECL strength of luminol system.At the same time,annular DNA walker amplification strategy is used to enhance the ECL signal.When the target mi RNA exists,annular DNA walker is activated,and a large amount of Co/Ni@NC can be captured on the electrode surface.Therefore,an ECL sensor based on AuNPs/NGDY,Co/Ni@NC and annular DNA walker triple signal amplification is constructed for sensitive detection of mi RNA.4.An“on-off-on”electrochemiluminescence and fluorescence dual mode sensor based on nitrogen-doped graphidiyne quantum dots for the determination of captoprilIn this study,nitrogen-doped graphidiyne quantum dots（NGDY QDs）are synthesized from triazo-doped graphidiyne with high nitrogen content as efficient emitter,and an"on-off-on"ECL and fluorescence dual-mode sensor are constructed for the detection of captopril.Because Cu²⁺can bind to the groups on the surface of NGDY QDs,the ECL and fluorescence signals of NGDY QDs can be quenched.When captopril is added,captopril can compete for Cu²⁺on the surface of NGDY QDs to form a stable catoprile-Cu²⁺complex.At this time,ECL and fluorescence signals of NGDY QDs are restored.Captopril is a common drug used in the treatment of arterial hypertension and cardiovascular diseases.The traditional detection methods are mostly single mode,while the dual-mode detection strategy can provide better built-in correction and higher accuracy.The dual-mode sensor is applied to the detection of captopril with satisfactory results.5.An"off-on"electrochemiluminescence aptamer sensor based on graphite-like carbon nitride and flower-like titanium dioxide for the ultrasensitive detection of thrombinThe flower-like titanium dioxide（f1-TiO₂）has a huge specific surface area,which can not only increase the capacity of 2D graphite-like carbon nitride（g-C₃N₄）layer,but also promote the action of coreactants.And the ECL intensity of the electrode modified with f1-TiO₂/g-C₃N₄/PDA is 3 times higher than the electrode modified with g-C₃N₄/PDA.An ultrasensitive"signal-off-on"ECL biosensor is constructed based on f1-TiO₂/g-C₃N₄/PDA for thrombin detection.The carboxylated thrombin aptamer（s DNA）is incubated onto the modified electrode by amide bond,then the complementary strand of thrombin aptamer（t DNA）modified with ferrocene is connected to the electrode surface by complementary base pairing with s DNA.Due to the ferrocene can quench the ECL of g-C₃N₄,the ECL signal decreases,while the ECL signal is restored in the presence of the target thrombin（TB）.When K₂S₂O₈and H₂O₂are used as a co-reactant,the ECL aptassensor shows good specificity,repeatability and stability for TB detection.This novel ECL aptasensor has potential application in human thrombin assay.