Research And Application Of Electrochemiluminescence Biosensor Based On Poly(Indole-6-Carboxylic Acid) Nanocomposites

Electrochemiluminescence?ECL?,alsoknownaselectrogenerated chemiluminescence,refers to the process that the material generated on the electrode surface undergoes electron transfer reaction to form excited state,then the excited state returns to the ground state to generate optical radiation phenomenon.ECL is an ingenious combination of electrochemical and chemiluminescence,with the advantages of simple operation,low optical background noise,high luminescence purity and high sensitivity.Electrode modification material is one of the key factors affecting the sensitivity of ECL sensors.Polyindole nanomaterials with large specific surface area and good electrical conductivity are often used as electrode modification material in sensors.When functional groups are introduced into the indole monomer,the structure and properties of the polymer can be adjusted and the biologically active substance can be easily immobilized on the surface of the electrode through the interaction of different groups.Flower-like gold nanoparticles?FGNs?are nano-materials with flower-like structure and have excellent electrical conductivity,which can be prepared by electrochemical deposition.When FGNs combined with poly?indole-6-carboxylic acid??PICA?,the properties of the material will be greatly improved.As a new carbon material,graphene quantum dots?GQDs?are one of the popular materials due to the intrinsic properties of environmentally friendly,low toxicity,and good biocompatibility.In this thesis,three kinds of novel ECL biosensors were constructed by using PICA/FGNs nanocomposites as electrode modification materials,and GQDs as ECL luminophores.The contents are as follows:1.TheresearchofpreparationandpropertiesofPICA/FGNs nanocompositesThe FGNs modified electrode was successfully prepared by one-step electrochemical deposition method.Based on this,novel PICA/FGNs nanocomposites were prepared by electrochemical polymerization.Cyclic voltammetry curves showed that PICA/FGNs composites had good electrochemical activity and redox stability.The scanning electron microscope showed that the composite material had loose porous flower-like core-shell structure,which not only had a large specific surface area,but also effectively reduced the ion diffusion distance and improved the conductivity of the electrode.The prepared GQDs have good biocompatibility and high and stable ECL strength.The combination of PICA/FGNs nanocomposites and GQDs can effectively amplify ECL signal and broaden its application potential in the field of ECL sensors.2.Electrochemiluminescence aptasensor for detection of thrombin based on PICA/FGNs nanocompositesAn ECL aptasensor for sensitive determination of thrombin was constructed based on PICA/FGNs nanocomposites and GQDs.As the electrode modified material,PICA/FGNs nanocomposites had large specific surface area and fast electron transfer rate,which can effectively improve the sensitivity of the sensor.The amino-modified thrombin aptamer chain?TBA1?and the carboxyl-containing PICA/FGNs were covalently coupled to the electrode surface by a nucleophilic reaction.AuNP-linked GQDs-DNA S3 and TBA2 were used as ECL signal probes.The presence of AuNP could increase the load of GQDs,and the combination of the two materials could achieve dual signal amplification.The ECL aptasensor exhibited a wide linear range of0.001-10 nM,a low detection limit of 0.05 pM,and good stability,selectivity and reproducibility.Moreover,the aptasensor could be used to detect thrombin in actual human serum samples,providing potential application value for clinical diagnosis of biological proteins.3.A label-free electrochemiluminescence aptasensor based on PICA/FGNs nanocomposites for detection of aflatoxin B1A novel label-free ECL aptasensor was constructed based on PICA/FGNs nanocomposites,GQDs and gold nanorods?AuNRs?for the detection of aflatoxin B1?AFB1?.The core-shell structured flower-like PICA/FGNs nanocomposites were prepared by electrochemical polymerization,which can be used to accelerate electron transfer and increase the specific surface area of the electrode.GQDs and AuNRs were modified to the electrode surface by layer-by-layer dispensing method.AuNRs with excellent electrical conductivity were used to enhance the ECL signals and improve the load capacity of aptamers.Under the optimal conditions,the ECL aptasensor showed accurate and sensitive analysis performance for AFB1 with a detection range of 0.01-100 ng mL^-11 and a detection limit of 3.75 pg mL^-1.At the same time,the aptasensor had good stability,selectivity and reproducibility,revealing potential applications in food safety monitoring and environmental analysis.4.Electrochemiluminescence immunosensor for determination of prostate antigen based on PICA/FGNs nanocompositesA sandwich-type ECL immunosensor for detecting prostate antigen?PSA?was developed based on PICA/FGNs nanocomposites and GQDs.As electrode modified material,the core-shell structured flower-like PICA/FGNs nanocomposites were not only used for fixing the primary antibody?Ab1?,but also used for improving the conductivity of the electrode.GQDs were immobilized on poly?ethyleneimine?functionalized graphene oxide?PEI-GO?by amide bond,and then AuNP was modified on the surface of GQDs-PEI-GO.The obtained AuNP/GQDs-PEI-GO composites were used to connect the secondary antibody?Ab2?.GQDs could be attached to the electrode surface by the specific combination of PSA and Ab1 and Ab2.The synergistic effect of PICA/FGNs nanocomposites,AuNP and PEI-GO effectively increased the ECL signal of GQDs.Under optimal conditions,the ECL immunosensor responded specifically to PSA in the range of 1 pg mL^-1-100 ng mL^-11 with a detection limit of 0.44 pg mL^-1.At the same time,the immunosensor showed good selectivity,stability and reproducibility,and it was expected to open up new detection pathways for real sample detection of PSA and other biomarkers.