Study On The Novel Photoelectrochemical Aptasensing

The rapidly developed photoelectrochemical(PEC)bioanalysis has attracted considerable attention in recent years due to their advantages of low cost,rapid response and great potential in the field of biological analysis.Due to the urgent demand for ultra-sensitive and miniature biological detection,signal amplification has drawn increasing interests in the community of analytical chemistry,and PEC bioanalysis has made some progress in the aspect.Aptamer as a kind of target molecule recognition element have not only well preserved specificity and binding force of antibody,but also been stable and easy to be modified.With its unique features and great promise for future bioanalysis,aptamers flourish in many fields.Moreover,since the quantum size and the surface effect,nanoparticles have the special photoelectrochemical properties that are different from the bulk material.These advantages make nanoparticles used widely in photoelectrochemical biosensor,espeially some biological modification of nanomaterials have prominent role in photoelectric signal amplification.The first work in the paper is about photoelectrochemical protein biosensor.We successfully fabricated an ultrasensitive photoelectrochemical protein biosensor on the basis of energy transfer.We fixed the CdS QDs on ITO electrode and the antithrombin G-quadruplex were immobilized on the CdS QDs by the carbodiimide-assitted amidation reaction for thrombin capture.Aptamer tagged Au NPs could recognize another binding site of thrombin.The single stranded DNA can adjust the distance between the Au NPs and CdS QDs and exciton-plasmon interactions(Exciton-Plasmon Interaction,EPI)could emerge when they were in close.In CdS-Au system,the radiative decay in CdS QDs along with the spontaneous emission would stimulate the plasmon resonance of the proximal Au NPs accompanying the energy transfer between the particles,and the photocurrent quenching of CdS QDs was observed.With this EPI effect,we could realize the signal amplification and ultrasensitive detection of thrombin.Result in the specificity of aptamer,the biosensor has showed good selectivity.The second work is about photoelectrochemical aptasensing.We prepared the Ag core-Au satellite nanoparticle labled with the aptamer,which acts the role of energy-transfer probe.In the present model system,firstly,we fixed the CdS QDs on ITO electrode,and antibody was immobilized on the modified ITO electrode by the carbodiimide-assitted amidation reaction.The PSA was captured by antibody and can be used as bridge molecule to bind with the substrate and the aptamer modified Ag core-Au satellite nanoparticles,forming sandwich structure.The energy transfer between Ag core-Au satellite and CdS QDs can reduce photocurrent intensity of CdS QDs,which makes sensitive detection of PSA.