Oriented Immobilization of Anti-IgG on Amine Functionalized Carbon Nanotubes for Electrochemical Sensing of Human IgG

The oriented immobilization of antibody is the most critical step in preparation of a highly sensitive immunosensor. In the present report multiwalled carbon nanotubes were treated with nitric acid followed by ethylenediamine to produce amine functionalized carbon nanotubes. To obtain a properly oriented immobilization, initially the sugar chain of antibody (anti-IgG) was oxidized to aldehyde using periodate and then the aldehyde groups were allowed to react with amine groups of carbon nanotubes. The antibody immobilization was verified using the techniques such as field emission scanning electron microscope, Fourier transform infrared, UV-Vis spectroscopy and electrochemistry. Finally determination of antigen (human IgG) was performed in the presence of conjugated horseradish peroxidase as a label, and H2O2 and potassium iodide as the enzyme substrates. At the optimum pH of 7.2, the detection limit of 16.6 ng/ml was obtained for determination of human IgG.