Study On Electrochemical Sensor Based On Nanomaterials For Enhancing Tumor Marker Detection Signals

Electrochemical biosensors convert a signal of a target molecule and its reaction into an electrical signal（current,potential,impedance,capacitance,etc.）byspecificrecognitionbetweenbiological macromolecules（antigens,antibodies,enzymes,hormones,etc.）,thereby qualitative or quantitative detects the macromolecules.Electrochemical biosensors have the characteristics of fast response,good selectivity,high sensitivity and low cost.They have been widely used in the detection of biological macromolecules and,therefore,study on electrochemical biosensors that can detect tumor markers quickly,sensitively and accurately is of great significance in clinical cancer screening,disease diagnosis and monitoring.In this thesis,we were constructed a sandwich-type of double electrical signal amplification and molecularly bioimprinted technology of specific recognition for detecting carcinoembryonic antigen and alpha-fetoprotein.The main research contents of this thesis are as follows:1.Fabrication and application of sandwich type electrochemical biosensorsSandwich-type electrochemical biosensors were prepared based on reduced graphene oxide/chitosan/gold nanoparticles（rGO/CS/AuNPs）as sensing platform and polysulfonium-gold nanoparticle（PTh-AuNPs）complex as signal labeles to sensitively detect carcinoembryonic antigen（CEA）.A sandwich-type electrochemical biosensor was obtained from reduced graphene oxide（rGO）,chitosan（CS）,gold nanoparticles（AuNPs）,primary antibody（Ab₁）,bovine serum albumin（BSA）,carcinoembryonic antigen（CEA）and a secondary antibody（Ab₂）on glassy carbon electrode（GCE）,which was used for detecting carcinoembryonic antigen.Under the optimal experimental conditions,the concentration of carcinoembryonic antigen was in the range of 0.3ng/mL³0 ng/mL,and the DPV peak current was positively correlated with the concentration of carcinoembryonic antigen.The linear equation was:I_p（μA）=0.4900 logC+11.09,linear correlation coefficient R²=0.9972.The detection limit was as low as 0.1471 pg/mL.The sandwich type electrochemical biosensor was applied to detect carcinoembryonic antigen in human serum samples.The experimental resultsshowthatthesandwichelectrochemicalbiosensors Ab₂-PTh-AuNPs/CEA/BSA/Ab₁/AuNPs/CS/rGO/GCE have high sensitivity,good stability and good selectivity,providing a new detection platform for early cancer diagnosis.2.Fabrication and application of molecularly imprinted polymer electrochemical biosensors.Two novel molecularly imprinted polymer（MIP）electrochemical biosensors were fabricated,one is carcinoembryonic antigen-MIP（CEA-MIP）electrochemical biosensor for carcinoembryonic antigen detection,andtheotherisalpha-fetoprotein-MIP（AFP-MIP）electrochemical biosensor applied for the detection of alpha fetoprotein.When fabricating MIP electrochemical biosensors polysulfide（PTh）and gold nanoparticles（AuNPs）were used to modify electrodes to effectively enhancethedetectionsignals.Throughelectropolymerization,carcinoembryonic antigen（alpha-fetoprotein）as a template molecule and dopamine（DA）as a functional monomer were changed,to obtain"PDA-CEA"（"PDA-AFP"）complex,after the elution of the free functional monomer,the specific cavity formed can adsorb the target molecules.Under the best experimental conditions,differential pulse voltammetry（DPV）wasusedfordetection.ForCEA-MIP electrochemical biosensors,the peak current of DPV decreases with the increase in the concentration of carcinoembryonic antigen.The linear response range of MIP electrochemical biosensor ranges from 0.001ng/mL to 1000 ng/mL.The linear equation is:I_p（μA）=-0.9158 logC-1.912.The correlation coefficient was R²=0.9984 and the detection limit was as low as 0.2589 pg/mL.For AFP-MIP electrochemical biosensors,the DPV peak current decreases with the increase in alpha-fetoprotein concentration.The response range of AFP-MIP electrochemical biosensor is 0.001 ng/mL⁸00 ng/mL.The linear equation is:I_p（μA）=-2.4344logC-9.3309,linear correlation coefficient R²=0.9905,detection limit was 0.8138 pg/mL.These two MIP electrochemical biosensors can detect carcinoembryonic antigen and alpha-fetoprotein in human serum samples,and the results are satisfactory,which provides a new detection method for detecting tumor markers.