A novel TiO 2 nanowire bundle microelectrode based immunosensor was demonstrated as a more sensitive, specific, and rapid technology for detection of Listeria monocytogenes. TiO 2 nanowire bundle was prepared through a hydrothermal reaction of alkali with TiO 2 powder and connected to gold microelectrodes with mask welding. Monoclonal antibodies were immobilized on the surface of a TiO 2 nanowire bundle to specifically capture L. monocytogenes. Impedance change caused by the nanowire-antibody-bacteria complex was measured and correlated to bacterial number. This nanowire bundle based immunosensor could detect as low as 10 (2) cfu/ml of L. monocytogenes in 1 h without significant interference from other foodborne pathogens.