Functionalized SiO2labeled CA19-9 antibodies: A new strategy for signal amplification of antigen–antibody sensing processes.

A new strategy was described for amplifying the response of the antigen–antibody sensing processes by functionalizing SiO2nanoparticles labeled secondary antibodies based on a sandwich immunoassay in this work. At first, the multi-walled carbon nanotubes (CNTs) were individually dispersed in the aqueous bovine serum albumin (BSA) to obtain BSA molecules coated CNTs (BSA–CNTs). Then the gold colloids (nano-Au) were absorbed on the BSA–CNTs surface by the amido and disulfide groups of BSA. Later, a functionalized gold/carbon nanotube composite nanohybrid (DpAu/nano-Au/BSA–CNTs) modified electrode was developed by electrochemical deposition of Au3+onto nano-Au/BSA–MWNTs surface. Thus, a sensitive immunosensor for carbohydrate antigen 19-9 (CA19-9) has been constructed by further employment of Nafion coated SiO2nanoparticles labeled secondary antibody (SiO2–Ab2) for the signal amplification. More importantly, the loading of SiO2–Ab2can not only cause the construction of the dielectric antigen–antibody immunocomplex layer but also introduce the insulated Nafion coated SiO2nanoparticles which demonstrate the relatively high resistance, resulting in a strong detection signal. The proposed sensing strategy provides a wide linear dynamic range from 0.15 to 150 U mL−1with a low detection limit of 0.06 U mL−1at 3 times the background noise. Moreover, the extremely high stability of the functionalized gold/carbon nanotube composite nanohybrid monolayer allows the designed biosensing interface to obtain a good stability and long-term life. [ABSTRACT FROM AUTHOR]