Dopamine coated Fe₃O₄ nanoparticles as enzyme mimics for the sensitive detection of bacteria

We report a simple and economical colorimetric bacterial sensing strategy with catalytic amplification using dopamine-capped iron oxide (Dop-Fe₃O₄) nanoparticles. These nanoparticles catalyse the oxidation of a chromogenic substrate in the presence of H₂O₂ into a green colored product. The catalytic activity of the nanoparticles is inhibited in the presence of bacteria, providing naked eye detection of bacteria at 10⁴ cfu mL^-1 and by spectrophotometric detection down to 10² cfu mL^-1.