Boron-doped Diamond Electrodes Modified with Fe sub(3)O sub(4)u Magnetic Nanocomposites as Sensitive Platform for Detection of a Cancer Biomarker, Interleukin-8

Interleukin-8 (IL-8), a dimeric protein composed of two identical subunits, is overexpressed in different human cancers, among them pancreatic cancers and head and neck cancers. There is a strong demand for monitoring of this biomarker protein for early cancer detection. A new concept of label-free impedimetric immunosensors for IL-8 detection is described in this work. A nanocomposite of gold nanoparticles (AuNPs) decorating a magnetic Fe sub(3)O sub(4) core is synthesized using cysteamine as linker, and characterized using TEM and UV-Vis spectrometry. After immobilization of these Fe sub(3)O sub(4)u magnetic nanocomposites on a boron doped diamond (BDD) electrode using a simple magnet, anti-human IL-8 monoclonal antibody is linked to the AuNPs, previously functionalized with thioctic acid. The functionalization of the immunosensor was characterized using two electrochemical techniques: cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), performed in phosphate buffer with ferro/ferricyanide as the redox probe. The EIS technique was used for affinity assays: antibody-Antigen binding. A linear relationship between the increment in the electron transfer resistance (R sub(CT)) and the logarithmic value of IL-8 concentration was observed between 0.1pg/mL and 1000pg/mL. The limit of detection (LOD) was estimated at 0.03pg/mL.