An Integral Recognition and Signaling for Electrochemical Assay of Protein Kinase Activity and Inhibitor by Reduced Graphene Oxide-Polydopamine-Silver Nanoparticle-Ti(4+) Nanocomposite

A novel electrochemical biosensing method for protein kinase (PKA) activity was demonstrated by using a reduced graphene oxide-polydopamine-silver nanoparticle-Ti(4+) (rGO-PDA-AgNPs-Ti(4+)) nanocomposite. The obtained nanocomposite possessed an integral capability for phosphopeptide recognition and signal readout. The polydopamine modified reduced graphene oxide (rGO-PDA) was firstly prepared based on a self-polymerization method of dopamine. The silver ions were adsorbed onto polydopamine (PDA) layer and directly reduced into silver nanoparticles (AgNPs), which was used for electrochemical signal reporting. Then, the Ti(4+) cations were attached onto the PDA layer for phosphopeptide recognition according to the strong coordination ability of PDA with Ti(4+) and phosphate group. The prepared rGO-PDA-AgNPs-Ti(4+) nanocomposites were characterized with different methods. The developed rGO-PDA-AgNPs-Ti(4+) nanocomposites were then employed for electrochemical analysis of PKA-catalyzed kemptide phosphorylation. The sensitive detection toward PKA activity was realized with an experimental detection limit of about 0.01 U/mL. It may be also extended for the inhibitor evaluation. Thus, it provided a facile and sensitive means for electrochemical analysis of PKA activity and inhibitor screening.