Localized surface plasmon (SP)-based amplification of sensitivity in a phase-sensitive SP resonance (SPR) biosensor is investigated numerically. SP is localized by surface-relief periodic nanowires. An optimum sample obtained by modeling DNA hybridization and water-glycerin mixture employed a gold grating with 300 nm period and 10 nm thickness on a gold film and an SF10 glass substrate. The localized SPR structure was shown to have the sensitivity enhanced by more than 10 times than conventional SPR for detecting DNA hybridization at an identical film thickness of 40 nm. The enhancement was found to be associated with field localization near the nanostructure. The results suggest a novel approach of improving the sensitivity of SPR detection. (C) 2009 Elsevier B.V. All rights reserved.