Study On Aptamer Based Electrochemiluminescence Biosensor And Their Analytical Applications

In this thesis, combines the merits of high selectivity of aptamer and highsensitivity of electrochemiluminescence (ECL), and also combines the advantage thethe ECL amplify capability of tris(2,2′-bipyridyl)ruthenium(II)-doped silicananoparticles (Ru-SiNPs), three different aptamer based biosenor had beendeveloped.The thesis includes four chapters. In chapter1, the historical perspective ofECL, classifications and mechanisms of ECL and the analytical applications of ECL,the prospect and the analytical applications of aptamers in ECL bisosensor; theapplication of nanomaterials in ECL and the purpose and significant of this thesiswere discribed.In chapter2, a highly sensitive and selective electrochemiluminescence biosensorfor detection of thrombin based on the strategy of target-induced conjunction of splitaptamer fragments was developed. In this study, tris(2,2′-bipyridyl)ruthenium(II)-dopedsilica nanoparticles (Ru-SiNPs) had been synthesis and applied as the ECL reagent.Since every particles contains thousands of Ru(bpy)32+, when modified on theelectrode surface, it can be used as ECL amplification. The ECL intensity had a linearrelationship with the logarithm of thrombin concentration in the range of3.3×10-13~3.3×10-11mol/L and the detection limit was2.0×10-13mol/L.In chapter3, a novel aptamer based ECL biosensor for the detection of adenosinewas developed based on the quench of Ru(bpy)32+by ferrocene. Ferrocene andRu-SiNPs were labeled to the ends of the detection probe containing adenosineaptamer sequence and its complementary capture probe, respectively. Then the probeswere immobilized onto surface of gold electrode through Au-S interaction to formaptamer/DNA duplex structure and the composition of biosensing electrode. In thepresence of adenosine, the aptamer prefers to form aptamer/adenosine thanaptamer/DNA complex, and then the aptamer tagged with Fc removed from theelectrode, which result in an recovering ECL signal. And The integrated ECL intensityversus the concentration of adenosine was linear in the range from5.0×10-8to1.0×10-10mol/L, and the detection limit was3.1×10-11mol/L. In chapter4, a novel ECL “sandwich” biosensor had been developed to detectcocaine. The “sandwich” biosensor was fabricated based on the fact that the singleaptamer could be split into two fragments and the two dissociated parts could form afolded, associated complex in the presence of targets. One fragments had beenmodified on the electrode surface and the other one had been modified with Ru-SiNPs.Due to the weak interaction between the two fragments, the sensor exhibited low ECLsignal in the absence of cocaine. After the addition of the target cocaine into thesolution, it would induce associated of the two fragments and stabilized the associatedcomplexes, leading to immobilization of Ru-SiNPs on the electrode surface and theECL detected on the electrode surface would enhanced. The enhanced ECL intensityhas a direct linear with the logarithm of cocaine concentration in the range of1.0×10-9~1.0×10-11mol/L with the detection limit of3.7×10-12mol/L. The developed biosensorhad been applied to detect the trace amount of cocaine on the banknote with satisfiedresults.