Design And Biosensing Of Electrochemiluminescent DNA Probes

In recent years,rapid and sensitive detection of specific DNA with ultralow concentrations has attracted considerable interest due to its broad applications in infectious diseases,genetic therapy and early screening of diseases.The detection of gene mutation at the molecular level make it possible in clinical diagnosis.Electrochemiluminescence(ECL)which combined the chemiluminescence with electrochemistry techniques,exhibited its unique advantages,such as its simplified set-up,low background signal and high sensitivity.Using HCV-1b cDNA(hepatitis C virus-lb genotype complementary DNA)and oranl cancer gene as models,based on the site-specifically recognized of the BamHI endonuclease,the excellent ECL activity of graphene quantum dots and coupling electron-transfer mechanism with the electrochemiluminescence energy transfer(ECL-RET)from excited QDs to the ferrocene(Fc),the highly sensitive ECL method was proposed to detect DNA.1.A novel strategy for highly sensitive electrochemiluminescence(ECL)detection of DNA was proposed based on site-specific cleavage of BamHI endonuclease combining with the excellent ECL activity of graphene quantum dots(GQDs)and bidentate chelation of dithiocarbamate DNA(DTC-DNA)probe assembly.The difference between photoluminescence and ECL spectra peaks suggested the negligible defect existed on the GQDs surface for generating ECL signal.The formed DTC-DNA directly attached onto the gold surface by bidentate anchoring(S-Au-S bonds)which conferred a strong affinity between ligands and the Au surface,increasing the robustness of DNA immobilization on the gold surface.BamHI endonuclease site-specifically recognized and cleaved the duplex symmertrical sequence which made the double-strand DNA fragments and the GQDs break off from the electrode surface,inducing the decrease of ECL signal.Using HCV-lb cDNA(hepatitis C virus-lb genotype complementary DNA)as a model,a novel signal-off ECL DNA biosensor was developed based on the variation of ECL intensity before and after digesting the DNA hybrid.This ECL biosensor for HCV-lb cDNA determination exhibited a linear range from 5 fmol L-1 to 100 pmol L-1 with a detection limit of 0.45 fmol L-1 at a signal-to-noise ratio of 3,and showed satisfactory selectivity and good stability,which validated the feasibility of the designed strategy.The proposed strategy may be conveniently combined with other specific biological recognition events for expanding biosensing application,especially in clinical diagnoses.2.Combing with strand-displacement reactions,a novel and highly sensitive"signal-on" electrochemiluminescent(ECL)biosensing platform for detecting DNA.It was proposed based on coupling electron-transfer mechanism with the electrochemiluminescence energy transfer(ECL-RET)from excited QDs to the ferrocene(Fc).The Fc functionalized helper DNA has six complementary bases with probe DNA.When the helper DNA immobilized on the electrode surface through hybridization with probe DNA,the electron and energy transfer from electrochemically reduced QDs to the oxidized Fc(Fc+).A dual quenching effect on cathode ECL emission occured.However,in the presence of target DNA(using the oral cancer gene as a model),the QDs functionalized probe DNA inclined to hybridize with target DNA by their 19 complementary bases,and then the Fc functionalized helper DNA was released from the electrode surface,which produced a distinct recovering of ECL signal.A highly sensitive ECL biosensor for detection of target DNA was designed.This strategy showed satisfactory selectivity,good stability,wide linear range(5 amol L-1 to 0.1 pmol L-1)and low detection limit(2.4 amol L-1),which would provide a novel method for clinic assay and inchoate diagnoses of cancer.