Nanorods with Biocatalytically Induced SelfElectrophoresis

Nanorods with motion enhanced through biocatalytically induced self-electrophoresis are described. To obtain such nanorods, the polymer half of polypyrrole-gold (PPy-Au) nanorods is decorated with horseradish peroxidase (HRP) and their metal half with cytochromec (Cytc). If such nanorods are suspended in enzymatically generated mixtures of O₂(-) and H₂O₂, the immobilized Cytc is reduced by O₂(-), and the immobilized HRP is oxidized by H₂O₂. As both hemeproteins are capable of direct electron transfer to/from solid substrates, the oxidized HRP is subsequently reduced with electrons received, through the nanorod, from the reduced Cytc. The combined processes cause species from the electrical double layer of the nanorods to move from one end of the nanorod to the other, which powers the motion of the nanorods in the opposite direction. The diffusive motion of the hemeprotein-modified nanorods is characterized by a diffusion coefficient 30% larger in the presence of O₂(-) and H₂O₂ than in their absence. Unmodified nanorods do not show such behavior.