So far no study has yet reported on the synthesis of silica modified with phytic acid. Herein, SiO2–PA ionomer nanoparticles were synthesized based on electrostatic interaction between PA and SiO2 that was pretreated with (3-aminopropyl) triethoxysilane (APTES) and then SiO2–PA nanospheres were successfully immobilized on GCE.