We
demonstrate a single-step ultrasonic in situ complexation of
salicylic acid during the growth of Fe3O4-reduced
graphene oxide nanoparticles (∼10 nm) to improve the antioxidant
and antiproliferative effects of pristine drug molecules. These nanoparticles
have a precisely defined electronic molecular structure with salicylic
acid ligands specifically complexed to Fe(III)/Fe(II) sites, four
orders of magnitude larger electric surface potential, and enzymatic
activity modulated by ascorbic acid molecules. The diminishing efficiency
of hydroxyl radicals by Fe3O4-rGO-SA nanoparticles
is tenfold higher than that by pristine salicylic acid in the electro-Fenton
process. The H+ production of these nanoparticles can be
switched by the interaction with ascorbic acid ligands and cause the
redox deactivation of iron or enhanced antioxidation, where rGO plays
an important role in enhanced charge transfer catalysis. Fe3O4-rGO-SA nanoparticles are nontoxic to erythrocytes,
i.e., human peripheral blood mononuclear cells, but surpassingly inhibit
the growth of three cancer cell lines, HeLa, HepG2, and HT29, with
respect to pristine salicylic acid molecules.