Functionalized SiO2 labeled 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 SiO(2) nanoparticles 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 Au(3+) 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 SiO(2) nanoparticles labeled secondary antibody (SiO(2)-Ab(2)) for the signal amplification. More importantly, the loading of SiO(2)-Ab(2) can not only cause the construction of the dielectric antigen-antibody immunocomplex layer but also introduce the insulated Nafion coated SiO(2) nanoparticles 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(-1) with a low detection limit of 0.06 U mL(-1) at 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.