TiO2/MWNTs nanocomposites-based electrochemical strategy for label-free assay of casein kinase II activity and inhibition

In this paper, a novel label-free electrochemical strategy has been developed for assay of casein kinase II (CK2) activity and inhibition using TiO2/MWNTs nanocomposites. This detection system takes advantage of specific binding of the phosphate groups with TiO2 nanoparticles and fast electron transfer rate of MWNTs. In this strategy, the synthesized TiO2/MWNTs nanocomposite was firstly deposited on the surface of a glassy carbon electrode (GCE). The presence of MWNTs not only increased the surface area of the electrode but also promoted electron-transfer reaction. In the presence of CK2, the kinase reaction resulted in the phosphorylation of peptide substrates. The phosphorylated peptides were subsequently captured to the surface of GCE modified with TiO2/MWNTs nanocomposite through specific binding of the phosphate groups with TiO2 nanoparticles. Then the access of redox probe [Fe(CN)6]3−/4− to electrode surface was blocked. As a result, the decrease peak currents were related to the concentrations of the CK2, providing a sensing mechanism for monitoring peptides phosphorylation. The electrochemical strategy can be employed to assay CK2 activity with a low detection limit of 0.07 U/mL. The linear range of the assay for CK2 was 0–0.5 U/mL. Furthermore, the interferences experiments of PKA and inhibition of CK2 have been also studied by using this strategy.

► We develop a label-free electrochemical strategy for assay of CK2 and inhibition.
► The electrochemical assay is based on TiO2/MWNTs nanocomposites.
► Specific binding of the phosphate groups with TiO2 nanoparticles.
► Fast electron transfer rate of MWNTs.
► Providing a general platform for monitoring the activity of other kinases.