Fabrication Of Electrochemical Sensors Based On Functionalized Nanomaterials For Determination Of Carcinoembryonic Antigen

Cancer is the second leading cause of death in developed countries.It's meaingful to achieve early and precisely diagnosis of cancer since the survival rate can be maximized if the patients get effective treatment at an early stage.Carcinoembryonic antigen(CEA)is considered to be the most important clinical tumor biomarker.Developing rapid and sensitive method for the determination of trace amounts of CEA has become a very important research topic.It's well-accepted that electrochemical sensors have a variety of advantages,such as simplicity,sensitivity and rapidity.With the rapid development of nanotechnology,electrochemical sensors based on nanomaterials have attracted considerable attention due to their superior properties.In this dissertation,graphene quantum dots(GODs)with peroxidase activity were synthesized.In combination with other nanomaterials to amplify response signals,several non-enzymatic electrochemical sensors were constructed for the sensitive detection of CEA.This dissertation is divided into four chapters.1.Summarized the importance of detecting CEA and the advantages of electrochemical immunosensors.A list of several typical types of nanomaterials and their characteristics in electrochemical immunosensors was presented.Afterwards,the background and contents of this paper were proposed.2.In this chapter,graphene quantum dots were synthesized and characterized by infrared spectroscopy,fluorescence and TEM.Gold nanoparticles have large specific surface area and can promote the transfer of electrons.In this work,they were used as carriers to adsorb a large number of signal molecules.Besides,reduced graphene oxide(rGO)and gold nanoparticles were used to modify glassy carbon electrode(GCE).This sensor had excellent sensitivity and specificity.Under the optimal conditions,CEA was proportional to the response current in the range of 50 pg/mL to 500 pg/mL with a detection limit of 9.1 pg/mL.3.On the basis of the previous chapter,we selected carbon nano tubes as carriers to loading signal molecules because of the large-surface-area are capable of accelerating the electron transfer rate,as well as capturing a large number of GQDs and Ab2.The prepared SWCNTs-GODs-Ab2 was confirmed by TEM and SEM images and it was obvious that a large number of Ab2 and GQDs were modified on single-walled carbon nanotubes.The rGO-AuNPs were used to modify the electrode surface,and the electrochemical properties of rGO-AuNPs were investigated.It was found that rGO-AuNPs could significantly reduce the impedance of the electrode surface and amplify the response current signal.The responsive signal was 7.5 times higher than that of unmodified GCE.Thus,CEA was measured rapidly and efficiently.Under the optimal conditions,CEA was proportional to the response current in the range of 50 pg/mL to 650 pg/mL with a detection limit of 5.3 pg/mL.We also applied it to the actual sample detection,and the recovery rate was 91.0%?103.6%.Compared with the sensor constructed with gold nanoparticles,the detection limit was further reduced and the linear range was enlarged.4.CuO nanocubes as a kind of p-type semiconductors with a narrow band gap have excellent electrochemical performance and cost-effectiveness.In this chapter,the electrochemical properties of the CuO nanocubes/chitosan modified electrode were explored.The CuO nanocubes/chitosan modified electrode can amplify current signal efficiently.The sensor based on CuO nanocubes/chitosan had a linear correlation with the CEA concentration in the range of 100 pg/mL to 600 pg/mL.The limit of detection was 6.5 pg/mL.