Magnetic bead-based electrochemical detection of interaction between epigallocatechin-3-gallate and STAT proteins

In this report, the interaction of the signal transducer and activator of transcription (STAT3 and STAT5) proteins with a green tea polyphenol epigallocatechin-3-gallate (EGCG) was investigated using differential pulse voltammetry (DPV) at carbon paste electrodes (CPEs). Superparamagnetic agarose nickel beads were modified with His-tagged STAT proteins and exposed to EGCG in solution. After magnetic separation of the beads, the electrochemical oxidation of the remaining EGCG in the supernatant was monitored at ∼0.18 V (vs. Ag/AgCl). The changes in the peak current signal displayed the interaction of EGCG with STAT proteins. Our electrochemical results were in agreement with the surface plasmon resonance (SPR) method that indicated the KD values of EGCG for STAT3 and STAT5 proteins were 19.33 ± 2.11 μM and 19.53 ± 2.37 μM, respectively. To the best of our knowledge, the electrochemical detection of interaction between STAT proteins and EGCG is reported here for the first time. The voltammetric method described here provides a promising platform for the rapid and cost-effective screening of small electro-active molecules that interact with STAT proteins and other clinically important proteins.