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Development Of Solid-state Electrochemiluminescence Sensor For Thrombin And Mercury Ion Detection

Posted on:2019-04-06Degree:MasterType:Thesis
Country:ChinaCandidate:Y J HuFull Text:PDF
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Electrochemiluminescence?ECL?is a light emission process in a redox reaction of electrogenerated reactants,which possesses the advantages of electrochemical and chemiluminescence.ECL shows some distinguished advantages such as low background values,high selectivity,simplified optical setup and fast response.In recent years,solid-state ECL sensors have received much attention owing to the low cost and less pollution.However,the improvement in sensitivity and life-time still remains as a great challenge for the fabrication of solid-state ECL biosensors.Therefore,the goal of the paper is to develop novel solid-state ECL biosensors by using excellent-performance nanomaterials.Moreover,the specific recognition between aptamer and target,the structure transition of melecular beacon are also used to selectively detect thrombin and Hg2+.The main contents of this paper include:1.A solid-state ECL aptamer-based biosensing system based on special ferrocene-labeled molecular beacon aptamer has been developed successfully for thrombin detection.The ss-DNA capture probe?ss-DNA?was firstly immobilized onto glass carbon electrode?GCE?via gelatin cross-linking.The immobilized ss-DNA probe was composed of a ss-DNA sequence to adopt two distinct structures----a DNA double strand with a complementary DNA sequence tagged with a ECL signal producer tris?2,2'-bipyridyl?ruthenium?Ru-DNA1?derivative and a DNA duplex with a thrombin-binding aptamer tagged with a ECL quencher ferrocene?Fc-DNA2?.In the presence of thrombin,the aptamer sequence prefers to form the aptamer-thrombin complex,and the switch of the binding partners opened,which resulted in a strong ECL signal owing to the the decreased quenching effect of ferrocene to the ECL substrate.Under the optimized experimental conditions,The integrated ECL intensity(IECL)versus the logarithm of thrombin concentration?lgc?was linear in the range from 2.0×10-1010 mol/L to7.0×10-8 mol/L,with a detection limit of 3.0×10-11 mol/L?S/N=3?.Furthermore,the fabricated aptamer-based ECL sensor showed good selectivity.2.A solid-state ECL switch biosensor using Ru?bpy?32+/?-cyclodextrin-Pd nanoparticles??-CY-PdNPs?/Gel complex and ferrocene-labeled DNA probe?Fer-DNA?for the detection of Hg2+was successfully developed.The ECL biosensor includes an ECL substrate and an ECL signal switch.Ru?bpy?32+/?-CY-PdNPs/Gel composite modified on the glassy carbon electrode was used as the ECL substrate,which could bring about a clear and stable ECL signal by Ru?bpy?32+.Meantime,hairpin-like Fer-DNA probe acted as the ECL signal switch,which was designed by molecular recognition strategy and attached to?-CY-PdNPs through host-guest interaction between?-CY and ferrocene.Our investigation indicated that,when Hg2+was absent,the Fer-DNA probe retained its hairpin structure and led to an obvious quenching effect of Ru?bpy?32+signal.However,when the biosensor incubated with Hg2+,the specific T-Hg2+-T interaction brought about a change of the of Fer-DNA conformation,and such conformation adjustment resulted in a clear signal recovery of Ru?bpy?32+owing to the reduced quenching effect of ferrocene.The ECL switch biosensor offered good linear responses for Hg2+in the range of 3.0×10-126.0×10-7 g/mL with a detection limit of 1.5×10-12 g/mL at the 3sblank level.3.A novel ECL biosensing interface for Hg2+analysis was constructed based on the enhanced ECL signal from CdS QDs by reduced graphene oxide-Au nanoparticles?RGO-AuNPs?nanocomposites.RGO-AuNPs were prepared by the heat-treatment of graphene oxide and HAuCl4 solution under alkaline environment.The prepared RGO-AuNPs composites were dispersed in Gel and dropped onto the surface of GCE.Double-stranded DNA modified with amino at one end was then immobilized on the RGO-AuNPs/GCE surface in the presence of 1-pyrenebutyric acid N-hydroxysuccinimide linker,following which the avidin-modified CdS QDs were linked to double-stranded DNA labeled with biotin at another end through the formation of biotin–avidin complex.The excellent electrical conductivity of RGO-AuNPs nanocomposites and the high charge transfer efficiencies of the double-stranded DNA with T-Hg2+-T complex,which produced high-intensity electron transfer interface and improved the sensitivity of the biosensor.After Hg2+was added into the detection solution,the increased ECL signals showed good correlation with Hg2+concentration.The linear range of the sensor was5.0×10-131.0×10-9 M with a detection limit of 2.0×10-13 M?S/N=3?.This ECL biosensor showed satisfactory results when used for detecting Hg2+in real lake water.
Keywords/Search Tags:Electrochemiluminescence, Biosensor, Tris(2,2'-bipyridyl) ruthenium, Aptamer, Thrombin, ?-cyclodextrin-Pd nanoparticles, Reduced graphene oxide-Au nanoparticles, Hg2+
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