Construction Of A Novel Immunosensor Based On Nanomimetic Enzymes

Compared with the native enzyme,nanomaterials mimic enzyme has attractedmore and more attention of researchers because of their good stability,high reaction activity,large specific surface area,and easy modification with all types of functional molecules or proteins.In this thesis,Pd/PAMAM composites,Ag/Pd/Pt nanocomposites,Pd-Ir bimetallic materials and Cu-MOF/Au composite materials with good bio-compatibility and strong catalytic properties were synthesized to construct novel bioimmunosensor for the detection of C-reactive protein(CRP)and carcinoembryonic antigen(CEA).The details are as follows:(1)Utilizing the high combination ability between Pd nanocubes and aminationG4-polyamidoamine dendrimer(PAMAM),a novel electrochemical immunosensor was constructed for the detection of CRP.The as-prepared Pd/PAMAM composite was used as the label of secondary anti-CRP antibody for the catalytic reduction of H₂O₂to produce a new electrochemical signal.The primary anti-CRP was fixed on the glassy carbon(GC)electrode through NH₂-graphene.After incubated with CRP,the immunosensor can bind with Pd/PAMAM labeled anti-CRP further due to the immune reaction.After the fabrication of the sandwich structure,the Pd/PAMAM composites catalyze the reduction of H₂O₂ to produce a current signal which is proportioned to the concentration of CRP.The sensor has excellent response to CRP in the range of 1 ng/m L to 150 ng/m L,and the detection limit is 0.33 ng/m L.Experimental results show that the sensor is of high sensitivity and good selectivity.(2)Hollow cystic silver–palladium-platinum composite nanomaterial was synthesized and used as label to construct electrochemical immunosensor for rapid detection of CEA.The immunosensor was fabricated based on the traditional sandwich protocol with primary anti-CEA antibody immobilized on the surface of gold electrode through Au-SH bond,followed by the capture of CEA and the hollow cystic silver–palladium-platinum labeled secondary anti-CEA composite as detection probe onto electrode sequentially through the antibody–antigen reaction.Hollow cystic silver–palladium-platinum composites catalyze the reduction of H₂O₂ to produce a current signal which is proportional to the concentration of CEA.Cultivation time,concentration of immobilized antibody,and other experimental conditions affected the performance of the immunosensor were optimized.Under the optimized condition,the current signal of the immunosensor has good linearity with concentration of CEA ranging from 0.1 ng/m L to 40 ng/m L with detection limit of0.03 ng/m L.(3)A label-free bioimmunosensor based on Pd-Ir bimetallic nanoparticles as acatalyst for rapid detection of CEA was reported.Anti-CEA antibody was fixed on GC electrode through the adsorption effect of Pd-Ir nanoparticles which were modified on the electrode using chitosan..When CEA antibody combines with CEA antigen,the formed immunocomplexs blocks the catalytic activity of Pd-Ir bimetallic nanoparticles to the reduction of H₂O₂,leading to decrease in the current response signal.The decrease of the current response of the immunosensor has a linear relationship with the concentration of CEA ranging from 0.05ng/m L to 50 ng/m L with a detection limit of 0.017ng/m L at 3?.The sensor provides a new simple method for the determination of CEA.(4)Cu-MOF was synthesized and characterized using trimesic acid(H₃BTC)asorganic ligands to react with of copper nitrate by solvothermal method.Then,gold nanoparticles were loaded on the Cu-MOF to form Cu-MOF/Au composite materials,which has good catalytic properties to the oxidation of ascorbic acid.Using amino graphene quantum dots as the immobilized matrix and Cu-MOF/Au composite material as label,a novel carcinoembryonic antigen sandwich-type sensor was prepared.The current response of sensor has a linear relationship with the concentration of CEA ranging from 0.1ng/m L to 70 ng/m L with linear correlation coefficient of 0.9886,the detection limit was 0.02ng/m L.