Functional Construction Of MXene Based Nanocomposites And Investigation Of Their Carcinoembryonic Antigen Immunosensing Properties

The diagnosis rate and fatality of cancer in China are increasing year by year,thus how to diagnose various cancers efficiently is an important research direction nowadays.The presence of cancer markers is important for rapid and accurate detection of cancer,for example,carcinoembryonic antigen(CEA)as a cancer marker is associated with a variety of cancers including colorectal,gastric,pancreatic and ovarian cancers.Electrochemical immunosensor has been widely used in the identification and analysis of cancer markers due to its simple operation,fast response,strong selectivity and high sensitivity.This thesis was intended for the study of the high-performance CEA immunosensing electrode material.Aiming at solving the problems of poor adhesion of nanomaterials on the electrode substrate and slow interfacial electron transfer,two types of CEA immunosensing electrodes,label-free and labeled,were constructed based on MXene nanocomposites from the perspective of material microstructure modulation,and excellent immunosensing performances were obtained,providing an experimental basis for the construction of a high-performance tumor indicator sensing platform.The main research contents of this study are as follows:(1)Stable and high-efficiency few-layer MXene/polyaniline(PANI)/gold nanoparticles/βcyclodextrin composite electrode was prepared on a conductive glass electrode(FTO)by a facile two-step electrodeposition method,and a label-free CEA electrochemical immunosensor was constructed using potassium ferricyanide as an electronic probe.The microscopic morphology,structure and electrochemical properties of the composite electrode materials were analyzed by Scanning Electron Microscopy(SEM),Transmission Electron Microscopy(TEM),X-Ray Diffraction(XRD)and X-Ray Photoelectron Spectroscopy(XPS),Cyclic Voltammetry(CV),impedance method(EIS)and other characterization methods.The optimal technical parameters were obtained through comparative experiments:the electrophoretic deposition time was 2 min;the concentration of the electrophoretic solution was 2 mg/mL and the voltage was 20 V;the optimal electrodeposition time for AuNPs and β-CD was 500 s;the optimal pH value of the electrolyte used in the electrochemical tests was 7;the optimal time for antibody incubation was 40 min.The prepared label-free immunosensing electrode exhibited notable performance,and the linear range of detection for CEA antigen was 0.5～350 ng/mL,with a detection limit as low as 0.0429 ng/mL.Furthermore,it is also highly applicable to the detection of CEA in real human serum samples on the fabricated sensors,which is of good application and reference significance.The excellent sensing performance of the sensor was mainly attributed to the synergistic effects in the composite materials:(i)the stable composites of the few-layer MXene-Ti3C2 and the conducting polymer polyaniline(PANI)through Ti-N bonding effectively avoided the agglomeration and oxidation of the few-layer MXene,and obtains a uniform electrode substrate with large specific surface area,abundant active sites,high electrical conductivity and fast electron transfer efficiency;(ii)gold nanoparticles and βcyclodextrin formed a stable host-guest inclusion complex through organic,inorganic and biologic guest molecules,which further enhanced the electrical conductivity,hydrophilicity and stability of the nanocomposite electrode and achieved efficient loading of CEA antibodies,hence improving the sensitivity of the immunoelectrode for CEA detection.(2)A novel sandwich-type electrochemical immunosensor of Ab2-NH2-Ti3C2/CEA/BSA/Ab1/AuNPs/NiCo2O4/FTO with high selectivity and sensitivity was fabricated by electrochemical deposition and incubation methods.In this work,nickel-cobaltate deposited with gold nanoparticles was used as an electrode substrate for highly efficient loading of primary antibody(Ab1),and aminated few-layer MXene(NH2-Ti3C2)with abundant active sites and high conductivity was used as a marker for secondary antibody(Ab2)to sufficiently amplify the electrical signal.The morphology,physical phase,electronic structure and electrochemical properties of the composites were characterized via various technical instruments,and the optimum experimental conditions were obtained by optimizing the key experimental parameters:the optimal conditions chosen for the preparation of NiCo2O4/FTO electrodes were aNi:Co ratio of 1:6 and the calcination temperature was 300℃;the electrodeposition of AuNPs were conducted at a voltage of-1.4 V in a concentration of 0.75 mM of chloroauric acid for 200 s;the pH value of the electrolyte was 7;the incubation time of the immunoelectrode was 90 min;the concentration of the marker NH2-Ti3C2 was 3 mg/mL.The experiments showed that the proposed sandwich-type labeled immunosensor has a wide detection linear range of 5 ng/mL～800 ng/mL for CEA,with a detection limit as low as 2.252 pg/mL,and displayed excellent adaptability in the detection of human serum samples.This work enriched the electrode range of MXene composite-based labeled immunosensors and explored the effective ultilization of transition metal-based oxides NiCo2O4 in immunosensors,thus broadening research ideas for the design and construction of efficient immunosensors for tumor markers.