Morphological and binding properties of interleukin-6 on thin ZnO films grown on (1 0 0) silicon substrates for biosensor applications

To develop effective protein immobilization technology with minimal amounts of protein for high sensitivity surface acoustic wave biosensors, we determined the binding properties, and morphological characteristics of human interleukin-6 (IL-6), a pro-inflammatory cytokine, on the surface of ZnO, and SiO2 films grown onto (1 0 0) Si substrates, for the first time. Interleukin-6 was immobilized in the range of 0.276–10 pg/ml on the surface of ZnO and SiO2, and visualized at each stage, while protein–protein interactions were measured with the antigen/antibody immunoassay of solid-phase ELISA, which we modified for these types of substrates. A relative mass value was determined in each case. ELISA detected upward of 1 and 6 ng/ml of protein applied on ZnO and SiO2, respectively. It is concluded that the more reactive ZnO surface is a new and more effective template for protein immobilization.