PNNL

Abstract

A novel electrochemical immunosensor for the detection of tumor necrosis factor-alpha (TNF-a) based on poly(guanine)-functionalized silica nanoparticles (NPs) label is presented. The detection of mouse TNF-a via immunological reaction is based on a dual amplification: 1) a large amount of guanine residues is introduced on the electrode surface through the silica nanoparticle and immunoreaction, 2) mediator-induced catalytic oxidation of guanine, which results in great enhancement of anodic current. The synthesized silica NP conjugates were characterized with atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemistry. These experiments confirmed that poly[G] and avidin were immobilized on the surface of silica NPs. The performance of the electrochemical immunosensor was evaluated and some experiment parameters (e.g., concentration of Ru(bpy)32+, incubation time of TNF-a, etc.) were optimized. The detection of limit for TNF-a is found to be 5.0x10-11 g mL-1 (2.0 pM), which corresponds to 60 attomoles TNF-a in 30 uL. This immunosensor based on the poly[G] functionalized silica NP label offers great promise for rapid, simple, cost-effective analysis of biological samples.