Controllable gold-capped nanoporous anodic alumina chip for label-free, specific detection of bacterial cells

Abstract

We describe the development of a gold-capped nanostructured porous anodic alumina (PAA) chip, which makes use of localized surface plasmon resonance and interferometry for the label-free and specific detection of pathogenic bacterial cells via changes in relative reflected intensity (RRI) and wavelength shift. This chip is composed of PAA and gold layers that provide a reproducible and sensitive RRI and wavelength shift. We investigated the effects of varying the thicknesses of the PAA and gold layers on the optical responses of the chip. With this chip, we successfully detected and identified Pseudomonas aeruginosa in a proof-of-concept experiment; this chip can detect bacterial cells in a quantitative manner with a detection limit of 20 CFU per assay. Further, this chip based system can clearly identify target bacterial species in a multiplexed mode with high specificities on a single chip, so will be useful for the detection of various pathogenic microbes.