The Fabrication And Application Of Electrochemical Immunosensor Based On Bimetallic Core-shell Nanocomposites

It is well known that non-communicable disease（NCD）has become one of the serious problems affecting human health,it has high morbidity and mortality.Early detection and treatment is the key to cure NCD,and detection of biomarker is an important way to detect NCD early.In this paper,a series of composite nanomaterials were prepared by combining the excellent electrochemical properties of bimetallic core-shell composite nanomaterials with the immunosensor technology,which were applied to the construction of electrochemical immunosensor to realize sensitive detection of different biomarkers.The main research contents are as follows:（1）Sulfonic acid groups functionalized multi-walled carbon nanotubes（MWCNTs-SO₃H）loaded with dendritic Rh/Pd bimetallic core-shell nanoparticles（Rh@Pd NDs）to form Rh@Pd NDs/MWCNTs-SO₃H nanocomposites.Rh@Pd NDs not only provide abundant catalytic activity sites,but also effectively increase the load of antibodies and improve the sensitivity of immunoassay.In addition,MWCNTs-SO₃H have the advantages of good conductivity,good solubility and large surface area,which can further improve the electrochemical properties of the materials.Based on the synergistic effect of Rh@Pd NDs and MWCNTs-SO₃H,the Rh@Pd NDs/MWCNTs-SO₃H was prepared for the construction of label-free electrochemical immunosensor for the detection of carcino embryonic antigen（CEA）.Under the optimal experimental conditions,the constructed label-free immunosensor has a detection range of 25fg/m L～100 ng/m L for CEA and a detection limit of 8.3 fg/m L,with good reproducibility and high sensitivity,which can be applied to the detection of CEA in human serum.（2）Dendritic gold platinum core-shell nanoparticles and Cu²⁺functionalized nitrogen-doped graphene to form Au@Pt DNs/NG/Cu²⁺nanocomposites.Dendritic gold platinum core-shell nanoparticles（Au@Pt DNs）have abundant catalytic activity sites,which can effectively improve the capacity of electrocatalytic hydrogen peroxide（H₂O₂）.Nitrogen-doped graphene（NG）has good conductivity and large specific surface area,and can immobilize a large amount of Au@Pt DNs.After Cu²⁺adsorption,the catalytic capacity of nanocomposite for H₂O₂ reaction was further improved.A sandwich-type electrochemical immunosensor was prepared using Au nanoparticles functionalized polydopamine（Au@PDA）as the substrate material and Au@Pt DNs/NG/Cu²⁺as the secondary antibody biomarkers.Under the optimal experimental conditions,the immunosensor can realize the quantitative detection of CEA,with the detection range of 0.5 pg/m L～50 ng/m L and the detection limit of0.167 pg/m L,and have a good reproducibility,the selectivity and high sensitivity,the detection of CEA in serum for the human body got satisfactory results.（3）Gold platinum core-shell multi-branched nanoparticles and thionine functionalized nitrogen-sulfur co-doped graphene oxide to form N/S-c GO/L-lys/Au@Pt MBs/Thi nanocomposite.In the proposed N/S-c GO/L-lys/Au@Pt MBs/Thi,the covalent combination of Thi molecules on the surface of N/S-c GO/L-lys/Au@Pt MBs can present a strong current signal of differential pulse voltammetry（DPV）without the addition of redox substances,and show a high electrocatalytic activity for the reduction of H₂O₂.The gold nanorod functionalized polydopamine（Au NR@PDA）has high adsorption capacity and excellent electrical conductivity,and can be used as an effective substrate for the primary antibody（Ab₁）.A sandwich-type electrochemical immunosensor for the detection of cardiac troponin I（c Tn I）was constructed using N/S-c GO/L-lys/Au@Pt MBs/Thi as double signal.The constructed double-mode electrochemical immunosensor for detecting c Tn I obtained a wide detection range（50 fg/m L～250 ng/m L,750 fg/m L～100 ng/m L）and a low detection limit（16.7 fg/m L,250 fg/m L）by chronoamperometry method and DPV.The immunosensor constructed in this experiment has good reproducibility,high sensitivity and good stability,and has a broad application prospect in clinical biological analysis.