The Preparation Of Porous Nanocomposites Loaded With Silver Nanoparticles And Its Application In Electrochemical Immunosensors

Tumor markers are one of the most important indicators for early cancer detection.As a new sensor analysis method,electrochemical immunosensor has the advantages of high sensitivity,good selectivity and rapid detection,which is of great significance to the detection of tumor markers.Nanomaterials with excellent properties such as good catalytic properties and electrical conductivity are applied to the components of electrochemical immunosensors,which provides support for the optimization of electrochemical immunosensor performance.In this paper,porous nanocomposites loaded with silver nanoparticles were applied to electrochemical immunosensors,and two different electrochemical immunosensors to detect tumor markers were designed and constructed.Specific research contents are as follows:1. An ultrasensitive sandwich-type electrochemical immunosensor was designed by using gold nanoparticles（Au NPs）as the substrate material and microporous carbon spheres（CS）loading silver nanoparticles（Ag NPs）spaced Hemin/reduced graphene oxide（Hemin/r GO）porous composite materials（Ag NPs@CS-Hemin/r GO）as the detection antibodies（Ab₂）label for detecting carcinoembryonic antigen（CEA）.The Au NPs with good electrical conductivity and biocompatibility could accelerate the electron transfer on the electrode interface and enhance the load capacity of capture antibodies（Ab₁）.As a peroxidase-like substance,Hemin has excellent catalytic ability for H₂O₂ reduction.Ag NPs@CS)as the spacer inserts into Hemin/r GO sheet can overcome the irreversible stacking of r GO,and form complex porous structure.Ag NPs@CS-Hemin/r GO used as the Ab₂ label has a large working surface area and high utilization rate,which heightens the catalytic ability for H₂O₂ reduction to amplify the current signal effectually.The current signal and the logarithm of CEA concentration presented a wide linear response range of 20 fg m L^-1 to 200 ng m L^-1,and the detection limit of CEA was 6.7 fg m L^-1.Furthermore,the designed immunosensor exhibited a good reproducibility,selectivity and stability.2. An electrochemical immunosensor with high sensitivity was fabricated for alpha fetoprotein（AFP）detection.Cobalt-iron Prussian blue analog（Co Fe PBA）loading palladium-silver hybrid nanodendrites（Pd Ag NDs,Pd Ag NDs@Co Fe PBA）was designed and used as the label of secondary antibody for achieving signals amplification.With the synergy of Pd Ag NDs and Co Fe PBA,Pd Ag NDs@Co Fe PBA exhibited good conductivity and excellent catalytic activity,as well as high specific surface area and suitable biocompatibility.Gold nanoparticles（Au NPs）with good conductivity and biocompatibility were used as sensing platform for accelerating the electron transfer on the surface of electrodes and immobilizing primary antibodies（Ab₁）.Therefore,the designed immunosensor showed a wide liner range from 100.0 fg m L^-1 to 200.0 ng m L^-1,with a low detection limit of 33.3 fg m L^-1 for AFP.Besides,the designed immunosensor demonstrated excellent selectivity as well as reproducibility and stability.