Research On The Preparation Of Microfluidic Electrochemical Immunosensor Based On Two-Dimensional Nanomaterials

As an important indicator of cancer’s occurrence and proliferation,tumor markers play a significant role in early screening of cancer.However,the content of tumor markers in blood is very low in the early stage of cancer,which requires high sensitivity and low detection limit for sensors.In this paper,we developed an electrochemical microfluidic immunoassay sensor which combined the electrochemical impedance immunosensor with microfluidic chip to construct a three-electrode system for electrochemical detection on microfluidic chip,and nanomaterials with excellent electrical properties and large specific surface area are modified to detection electrode for the detection of ultra-low concentration tumor markers.This sensor has a wide detection range for tumor markers and a very low detection limit,and can meet the needs of clinical detection.Firstly,we designed a microfluidic chip suitable for electrochemical detection.The chip adopts a three-piece structure which contains ITO glass,PDMS runner and PDMS cover block.The chip integrates a three-electrode system of electrochemical impedance detection.The T-channel is used and the three electrodes are reasonably distributed in the runner.Based on the above chips,we introduced polyelectrolyte PDDA and MoS₂ with excellent electrochemical activity to structure MoS₂/PDDA composite films on the surface of working electrode by layer-by-layer self-assembly method.Then we immobilized the anti-AFP on the working electrode surface.Through specific binding between antigens and antibodies,AFP can be effectively captured.Adhesion of tumor markers will change the resistance value of the chip and we can realize high sensitivity detection of tumor markers by detecting the change of impedance signal of the chip.There was a linear relationship between the concentration of tumor markers and impedance signals in a certain range(10^-7-10^-5 mg/mL),and the limit of detection was 0.033 ng/mL.The chip can accurately detect tumor markers in serum and has broad application prospects in the detection of tumor markers.Subsequently,we introduced carboxylated graphene with excellent physical and chemical properties to replace molybdenum disulfide as the assembly unit,and graphene/polyaniline composite films were prepared by layer-by-layer self-assembly with polyaniline.Experiments show that the chip has lower initial impedance.Carcinoembryonic antigen（CEA）specific antibodies were immobilized on graphene/polyaniline composite film electrodes to capture CEA molecule,which led to the impedance change of sensor.The change of impedance is related to the concentration of CEA.The detection of CEA based on this method can be realized.The linear range of detection concentration is 10^-7-10^-5 mg/mL,and the detection limit is 0.055ng/mL,which meets the needs of clinical detection of CEA.In order to achieve better performance of the sensor,prepare sensors with lower initial impedance and the sensor’s working electrode is su·itable for the detection of tumor markers.We use molybdenum disulfide and polyaniline with better conductivity as assembly units to modify the working electrode to prepare electrochemical microfluidic immunosensor based on MoS₂/PANI composite film.The results of experiments show that the detection electrode of the sensor has a high roughness surface morphology,initial impedance has also been optimized.