Electrochemiluminescence Immunosensor Based On Quantum Dots And Peroxydisulfate

The main contents are summarized as follows:1. In chapter one of this thesis, we reviewed the electrochemiluminescence (ECL) and its application in immunoassay in the recent years. Firstly, we gave a brief introduction on the immunoassay, then the development history of electrochemiluminescence and its mechanism. Based on the relationship between the ECL intensity and the concentration of the antigen or antibody under test, we divided the immunoassay into two types, the enhanced and quenched immunoassay. Further we gave a brief introduction of the recent progress in the ECL immunoassay.2. In chapter two, the highly enhanced electrochemiluminescencefrom a novel hybrid CdTe-Fe3O4has been reported, and successfully applied to develop an ultra-sensitive ECL immunosensor for the detection of human IgG. The preparation of a new kind of magnetic andelectrochemiluminescence CdTe-FesO4nanohybridswas prepared through the coordination of the amino groups on the surfacesof Fe3O4and the carboxyl groups on CdTe QD. The structure and properties ofas-synthesized nanocomposites were characterized. The results showed that the nanocomposites exhibit high and stable ECL emitting. Composed with the GE-Au nanocomposites, we proposed ECL immunosensor for the detection of human IgG. The quenching effect of the immunoreaction on the intensity of the ECL was used to establish a calibration plot which is linear in the range from0.005to100ng/mL, the detection limit is0.9pg/mL.The proposed ECL sensor showed high sensitivity, stability and satisfactory reproducibility and openeda new avenue to apply ECL in more biological assays.3. In chapter three, we report a label-free electrochemiluminescence(ECL) immunosensor for a-fetoprotein (AFP).It is based on the use of CdSe quantum dots that wereelectrodeposited directly on a gold electrode from an electrolyte(containing cadmium sulfate, EDTA and seleniumdioxide) by cycling the potential between0and-1.2V (vs.SCE) for60s. The electrodeposited dots were characterizedby scanning electron microscopy and energy dispersivespectroscopy. Under optimal conditions, the specific immunoreactionbetween AFP and anti-AFP resulted in a decreaseof the ECL signal because of the steric hindrance and thetransfer inhibition by peroxodisulfate. The quenching effectof the immunoreaction on the intensity of the ECL was usedto establish a calibration plot which is linear in the rangefrom0.05to200ng/mL. The detection limit is2pg/mL.The assay is highly sensitive and satisfactorily reproducible.In our opinion it opens new avenues to apply ECL in labelfree biological assays.4. In chapter four, we proposed a novel electrochemiluminescenceimmunosensor for sensitive determination of Human IgG (HIgG). We found the nanocoposite GE-PDDA-ILs could efficiently enhancethe direct electrochemiluminescence from peroxydisulfate K2S2O8, which provided a novel sensing strategy for bio-molecules. The water-soluble and electroactive graphene-PDDA (GE-PDDA) nanocomposites were synthesized in one pot, and the Ionic liquids (ILs) were designed to disperse the nanocomposites. The obtained nanocomposite was characterized with transmission electron microscopy (TEM). The electrochemiluminescence behavior of K2O8at GE-PDDA-ILs/GCE was studied by cyclic voltammetry. A leaner response from0.1to20ng/mL was obtained between the concentration of the target molecular HIgGand ECL intensity with a detection limit of0.02ng/mL (S/N=3).The assay is highly sensitive and satisfactorily reproducible. In our opinion it opens new avenues to apply grapheneand ILs in ECL label free biological assays.5. In chapter five, we found that the direct electrochemiluminescence (ECL) from peroxydisulfate K2S2O8, a common ECL co-reactants, can been efficiently enhanced by nanocomposite of electrochemically reduced graphene oxide (abbreviated ERGO) and gold nanoparticles, which provided a novel sensing strategy for bio-molecules. The nano-Au-ERGOcomposites were electrochemically prepared by a two-step reduction method, in which graphene oxide (GO) was firstly reduced to graphene at the electrode surface, and then followed by electrochemicalreduction of HAuCl4. As15times enhanced ECL intensity of K2S2O8was observed with the formationof nanocomposite at glassy carbon electrode (GCE) and immunoreaction occurred at electrode surfacecan suppress corresponding ECL emissions, a new immunoassay strategy was developed with HumanlgG (HIgG) as model molecule. A leaner response from0.02to100ng/mL was obtained between theconcentration of the target molecular and ECL intensity with a detection limit of1.3pg/mL (S/N=3).The proposed ECL sensor showed high sensitivity, stability and satisfactory reproducibility and openeda new avenue to apply ECL in more biological assays. Besides, this method is economical, efficient, andpotentially attractive for clinical lmmunoassays.