The Design Of High Sensitive Probe Based On Noble Metal And Its Application In Immunoassays

Enzyme-linked immunosorbent assay（ELISA）and immunohistochemistry are classical immunoassays for the detection of biomarkers in bioanalysis and clinical diagnosis.However,it can not meet the detection of biomarkers in the early stage of the disease due to its low sensitivity.This work aims to amplify the signal of these immunoassays.First,based on the signal amplification system using repetitive unit,the AuNP-PAMAM probe was prepared and applied for the detection of hCG.Senond,based on the dual catalysis of nanozyme and HRP signal amplification system,the nanozyme-HRP probe was prepared to detect the hCG.Thirdly,several nanozymes were prepared in this work,of which Pd-Ru-Ir exhibit the highest activity and was used for signal amplification in immunohistochemistry.1.A necklace-like aggnegate was obtained by inducing gold nanoparticles with thiolated and biotinlated modified PAMAM.This aggregate consisted of multiple gold nanoparticles with an average size of 156 nm.Compared to traditional BA-ELISA（0.8 IU/L）,this AuNP-PAMAM probe was stronger,with detection sensitivity up to 0.03 IU/L and liner range from 0.10 to 6.40 IU/L.Meanwhile,the necklaced-licke AuNP-PAMAM probe was greater than traditional gold nanoparticle-based signal amplification methods.2.The Au@Pt-HRP probe based on the dual-catalyst Au@Pt and HRP was prepared.The probe was used to detect hCG with a sensitivity of 0.10 IU/L,and the linear range is0.40-12.80 IU/L.Compared with the traditional BA-ELISA,the advantage is obvious-the signal is increased nearly 8 times.In the results,the surface-bound HRP of Au@Pt nanoparticle was calculated with 21-22 HRP molecules binding to the surface of Au@Pt nanoparticle,which is beyond the traditional signal amplification gold nanoparticles carrier（11-12）.3.Three kinds of nanozymes,the hollow materials Ag-Pt,Ag-Pd and porous nanozyme Pd-Pt,were synthesized.The catalytic performance of these three materials were detected.Of which Pd-Pt nanozyme showed the highist catalytic activity.The Pd-Pt-HRP probe was prepared based on the dual-catalyst concenpt.The probe was used to detect hCG with a sensitivity of 0.07 IU/L.According to the XPS,TEM,nitrogen adsorption desorption experiments,etc.,we found that HRP molecules could enter the pores on the surface of Pd-Pt.The number of HRP molecules on the surface of the nanozyme was calculated to be 31-32.Two basic crystal forms of the nanozyme were synthesized.The Pd-Pt（111）facet showed advantage in the TMB-H₂O₂ system.4.The catalytic activity of Ru,Rh,Pt and Ir were compared in this part.Ir is suitable for the TMB-H₂O₂ system.Based on this result,The ternary metallic nanocube Pd-M-Ir（M=Ru,Rh and Ir）was prepared and applied in the TMB-H₂O₂ system.As for Ir,catalytic activity increased with the decrease of d-band.The Pd-Ru-Ir,possessing the highest catalytic activity,was then used in immunohistochemistry.The average optical density obtained was 8.7 times higher than that of the commercial immunohistochemistry.