Electrochemical Biosensors For Prion Assay Based On Novel Nanomaterials

Electrochemical biosensor is a device that converts chemical signal generated by the biometric reaction into an electrical signal and outputs it.Compare d to other analytical devices,the electrochemical biosensor is lower cost,faster reponse,more simplity and better selectivity,which has received great interest in analytical region.On the other hand,Prion diseases are a series of fatal neurodegenerative disorders accompanied by cognitive impairment,neuronal dysfunction and extensive brain damage.Prion protein plays an important role in prion disease.The misfolded proteins change from native alpha-helical to a very stable beta-sheet structure and propagate in central nervous system?CNS?resulting in t he prion disease.Prion diseases are infectious,which could be transmitted between humans and diferent animal species.The propagation of misfolded proteins cause serious clinical symptoms and finally lead to death.Thus,it is necessary for developing a sensitive sensing platform for PrP^C.Nanomaterials have attracted considerable attention in electrochemical sensors due to their large specific area,diverse morphologies and easily controllable size.Taking advantages of nanomtarials,electrochemical biosensors have been developed for sensitive and selective detection for PrP^C.The main points of this thesis are summarized as follows:?1?Based on Co-Co Prussian blue analogue?Co-Co PBA?,a novel immunosensor has been developed for sensitive detection of p rion protein.Gold nanoparticles?AuNPs?-modified Co-Co PBA nanocubes?PBA-AuNPs?worked as a support to immobilize secondary antibody?Ab2?of prion and also as the signal source for prion assay.When prion protein existed,Ab2-PBA-AuNPs could be introduced to theprimary-antibody?Ab1?-immobilizedelectrodesurface?thegold nanoparticles-modified glassy carbon electrode?AuNPs/GC??through specific antigen-antibody interaction between prion protein and its antibody to form the sandwich immunosensing platform.With the help of KOH aqueous solution,PBA generated a large DPV response.The response peak currents were linear with the logarithmic values of the concentration of prion?PrP^C?in the range from 0.075 pg mL^-1 to 100 pg mL^-1 with the detection limit of 0.014 pg mL^-1.Also,the immunosensor showed good selectivity and reproducibility.Based on the simple sensing structure and good analytical performance,the developed immunosensor may have promising applications in practical assay of infectious isoform of prion(PrP^Sc)and other proteins by simply changing the related antibody.?2?Based on graphene oxide?GO?,a novel electrochemical biosensor has been developed for sensitive detection of prion protein.The signal source(Cu²⁺)absorbed on GO due to the chemical bond,and introduced to the sensing platform without labeling due to the?-?stacking between GO and aptamer.The Ab1 was immobilized on the AuNPs modified GC electrode.When prion protein existed,PrP^C was captured on the electrode owing to the immunoreaction between Ab1 and PrP^C.Then,the PrP^C aptamer absorbed on PrP^C because its high affinity to PrP^C.Finally,GO-Cu²⁺nanocomposites was introduced to the sensing platform without labeling owing to the?-?stacking between GO and PrP^C aptamer and generated a large DPV response.The response peak current s were linear with the logarithmic values of the concentration of prion?PrP^C?in the range from 2.5 pg mL^-1 to 56.25 pg mL^-1 with the detection limit of 0.42 pg mL^-1.At the same time,the immunosensor showed good selectivity and reproducibility.?3?Based on cobalt hydroxide nanosheet?CoOOH?,a novel immunosensor has been developed for sensitive detection of prion protein.In the presence of PrP^C,PrP^C and its aptamer was captured on the AuNPs modified GC electrode.Subsequently,the signal source?Thi?was adsorbed on CoOOH nanosheet and introduced to the sensing platform without labeling due to the?-?stacking between CoOOH and aptamer.CoOOH-Thi nanocomposites worked as the signal source for prion assay also as the catalyst of hydrogen peroxide?H₂O₂?to facilitate the electron transfer processes at the sensing interface and amplified the response current.Finally,a large DPV response was observed.The response peak currents were linear with the logarithmic values of the concentration of prion?PrP^C?in the range from 1.25 pg mL^-11 to 62.5pg mL^-1 with the detection limit of 0.097 pg mL^-1.At the same time,the immunosensor showed good selectivity and reproducibility.