Construction And Application Of Electrochemical Biosensor For Carcinoembryonic Antigen Detection

For a long time,cancer has been a major public health issue worldwide.The onset and progression of cancer have obvious multi-stage characteristics.Therefore,early diagnosis of cancer is a necessary means to increase treatment opportunities and help successful treatment.Tumor markers are the general name of biological molecules that will change during cancer.As a typical malignant tumor marker,carcinoembryonic antigen（CEA）plays an important role in cancer screening,diagnosis and prognosis.Electrochemical biosensors play an irreplaceable role in CEA analysis,detection,and diagnosis due to their easy modification,strong specificity,and high sensitivity.Therefore,in this paper,the broad-spectrum tumor marker CEA was taken as the detection object to construct two different types of electrochemical biosensors,sandwich type and competitive type,respectively,with the help of electrochemical sensing technology and multiple signal amplification methods,hoping to provide effective technical reference for the early clinical diagnosis of cancer.1.Amperometric sandwich electrochemical biosensors which were based antibody and aptamer（Apt）were constructed.When target was present,it was captured by the capture elements modified on the electrode surface to form classic sandwich structure with the reporting element.At the same time,horseradish peroxidase and metalloperoxidase mimetic enzyme Au@Pt Nanoparticles were introduced respectively at the end of the detection element,catalyzing the substrate in the detection solution and releasing electrochemical signals.Under optimal conditions,the detection ranges of these two sensors were 1～50ng·m L^-1and 0.1～100 ng·m L^-1,respectively with detection limit of 0.98 ng·m L^-1and 0.31ng·m L^-1.Finally,by comparing the fixation method of recognition elements,response signal size,and sensitivity of the above two biosensors,it was found that using Apt as the recognition element for the construction of sandwich electrochemical biosensors could achieve better detection performance.2.A competitive electrochemical aptamer sensor based on Rec J_fexonuclease assisted target cycle amplification and rolling circle amplification（RCA）dual amplification strategy was constructed.In the presence of CEA,with the help of magnetic biological complexes and the unique cutting mode of Rec J_fexonuclease,the target was recovered from the Apt/CEA conjugate and the complementary DNA（c DNA）single strand was released.Then,the long chain DNA molecule was formed based on the c DNA through RCA technology,and the electrical signals were output after it was folded into hemin/G-quadruplex complex with electrical activity signals.The whole process was triggered by solution mixing,which not only improved the reaction efficiency and reduced the detection limit(with a minimum detection limit of 1.26 fg·m L^-1),but also avoided the cumbersome process of electrode fixation and improved the storage requirements of the sensing platform.Of course,this strategy was not limited to the types of electrode matrix,and could be widely used for various electrodes,such as gold column electrode and screen-printed electrode,completing the analysis and detection of the target within a wider range of 0.1 pg·m L^-1～200 ng·m L^-1.In addition,the sensor performed well in terms of reproducibility and stability:the relative standard deviation of the data obtained from five independent electrodes under the same conditions is 2.12%.The signal value of this biosensor stored at 4°C for 30 days could still retain 95.1%of the initial detection value.The above advantages provided a promising scheme for building a simple and highly sensitive electrochemical sensing platform to detect tumor markers.