title: Rapid detection of an anthrax biomarker by surface-enhanced Raman spectroscopy.
abstract: A rapid detection protocol suitable for use by first-responders to detect anthrax spores using a low-cost, battery-powered, portable Raman spectrometer has been developed. Bacillus subtilis spores, harmless simulants for Bacillus anthracis, were studied using surface-enhanced Raman spectroscopy (SERS) on silver film over nanosphere (AgFON) substrates. Calcium dipicolinate (CaDPA), a biomarker for bacillus spores, was efficiently extracted by sonication in nitric acid and rapidly detected by SERS. AgFON surfaces optimized for 750 nm laser excitation have been fabricated and characterized by UV-vis diffuse reflectance spectroscopy and SERS. The SERS signal from extracted CaDPA was measured over the spore concentration range of 10(-14)-10(-12) M to determine the saturation binding capacity of the AgFON surface and to calculate the adsorption constant (Kspore=1.7 x 10(13) M(-1)). At present, an 11 min procedure is capable of achieving a limit of detection (LOD) of approximately 2.6 x 10(3) spores, below the anthrax infectious dose of 10(4) spores. The data presented herein also demonstrate that the shelf life of prefabricated AgFON substrates can be as long as 40 days prior to use. Finally, these sensing capabilities have been successfully transitioned from a laboratory spectrometer to a field-portable instrument. Using this technology, 10(4) bacillus spores were detected with a 5 s data acquisition period on a 1 month old AgFON substrate. The speed and sensitivity of this SERS sensor indicate that this technology can be used as a viable option for the field analysis of potentially harmful environmental samples.
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Zhang
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Young
authors.forename: Olga
authors.initials: O
authors.lastname: Lyandres
authors.forename: Richard P
authors.initials: RP
authors.lastname: Van Duyne
mesh_terms: D001408:Bacillus anthracis / Q000737:chemistry*; D015415:Biomarkers / Q000032:analysis; D002118:Calcium / Q000032:analysis; D049329:Nanostructures / Q000737:chemistry; D010848:Picolinic Acids / Q000032:analysis*; D012834:Silver / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013171:Spores, Bacterial / Q000737:chemistry
chemical_list: D015415:Biomarkers; D010848:Picolinic Acids; D012834:Silver; D002118:Calcium; C004860:dipicolinic acid