Photoelectrochemical Biosensors Based On ZnO For The Detection Of DNA And Proteins

ZnO as a multifunctional nanometer material,it possesses great optical and electronic property,considerable morphological features and stability.Thus,this work has fabricated photoelectrochemical?PEC?methods based on ZnO for the detection of DNAand proteins.?1?An innovative photoelectrochemical?PEC?biosensor has been fabricated for the detection of DNA employed oriented hierarchical ZnO FRs and DNA dendrimers.ZnO FRs posess abundant hydroxyl groups which can react with phosphate groups of DNA by chemical band.When the target DNA?Trigger,T?and the assistants hybridized,DNA dendrimers are formed.Because of the steric-hinerance effect of DNA,the transfer of photo-generated electron is hindered,the photocurrent is decreased and the signal is amplified,so the detection of target DNA can be realized.The PEC biosensor for DNA detection is ranged from 10 f M to 0.1 ?M and achieves a detection limit of 3.7 f M.The linear equation is expressed as ?I??A?= 0.4206 logc?f M?-0.142?R2 = 0.994,S/N = 3?.Herein,PEC biosensor based on ZnO FRs and DNA dendrimers is expected to provide an rapid and inexpensive method for DNA detection.?2?A PEC immunosensor has been developed for the detection of ?-Fetoprotein?AFP?antigen?Ag?.The immunosensor is based on Au nanoparticles?NPs?and ZnO FRs,AuNPs will enhance visiable light absorbance of ZnO due to the surface plasma resonance?SPR?.Under visiable light irradiation,for SPR effect of AuNPs,photo-generated current is formed and photocurrent is enhanced.Further more,AuNPs have excellent biocompatibility and can combine with proteins in covalent bond.The AFP antibody?Ab?is immobilized on the surface of Au-ZnO FRs,detection of AFP can be realized for the changed photocurrent after the specific antibody-antigen immune reaction between Ab and Ag.The decreased photocurrent decrement is linear with the logarithm of AFP antigen?Ag?concentration.The immunosensor is ranged from 0.005 ng·m L-1 to 50 ng·m L-1 and the detection limit is 0.56 pg·m L-1.The linear equation is expressed as ?I??A?= 1.091 logc?pg·m L-1?+ 3.141?R2 = 0.993,S/N = 3?.The PEC immunosensor also exhibits high anti-interference property,acceptable stability,easy establishment and facile operation.The work will provide a hopeful photoelectrochemical strategy for other proteins detection in clinical diagnosis.A highly sensitive and selective PEC aptasensor has been constructed for carcinoembryonic antigen?CEA?detection on the basis of the property that g-C₃N₄-AuNPs hybrids can improve the visible light absorbance of ZnO FRs and enhance the photoelectric property in the visiable spectrum.The amidogen modified probe DNA?NH2-probe1?is immobilized on the electrode surface and hybridized with the sequence of CEA aptamer.Using p-type semiconductor Cu S CNs as hole carriers to capture photo-generated electrons,the photocurrent is reduced and signal changes is magnified.Cu S is combined with a probe sequence modified with amidogen?NH2-probe2?,which hybridizes with the other sequence of CEA aptamer.So the sandwichlike structure is formed through DNA hybridization of NH2-probe1,aptamer and NH2-probe2 which accelerates the recombination of electron-hole pairs,then the photocurrent is reduced.When Ag is introduced,the sandwichlike structure is partial destroyed.Because of the combination of Ag and CEA aptamer,the recombination of electron-hole pairs is hindered and so the photocurrent is enhanced.The changed photocurrent responded to the different concentrations of CEA can realize a quantitative determination for CEA.The PEC aptasensor for CEA determination is ranged from 0.001 ng·m L-1 to 2.5 ng·m L-1 and the detection limit is 0.14 pg·m L-1.The linear equation is expressed as ?I??A?= 0.373 c?ng·m L-1?+ 0.025?R2 = 0.994,S/N = 3?.The proposed aptasensor exhibits satisfactory PEC performance with simple fabrication,rapid detection,great sensitivity and specificity.The designed aptasensor may provide new idea for versatile PEC platform of different molecules determination.