Rapid Detection of an Anthrax Biomarker by Surface-Enhanced Raman Spectroscopy
INVENTION: Northwestern researchers have created a surface-enhanced Raman biosensor for use in detecting and identifying Bacillus anthracis, a spore-forming bacterium and dangerous pathogen for the disease anthrax. The system promises the potential for detecting other hazardous microorganisms.
ADVANTAGES: The present invention provides an efficient platform and methodology for the rapid detection of anthrax and other microorganisms in a surface-enhanced Raman biosensor, suitable for portable environmental assay.
SUMMARY: Among the potential biological warfare agent candidates, B. anthracis spores are of particular concern. They are robust and can be produced into weapon-grade material. Anthrax is an infectious disease, requiring medical attention within 24-48 hours of initial inhalation of more than 104 B. anthracis spores. However, diagnosis of anthrax is not immediate and may take 1-60 days before symptoms appear in humans. Thus, rapid detection of B. anthracis spores in the environment prior to infection is critical for human safety. A rapid, sensitive and portable detection protocol suitable for first responder use is critical.
Bacillus subtilis spores, harmless simulants for Bacillus anthracis, were detected 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. Improved binding efficiency of the CaDPA adsorption is accomplished by using atomic layer deposition (ALD) to coat the AgFON surface with a layer of alumina, which also protects the underlying noble metal surface.
AgFON surfaces, optimized for 750 nm laser excitation, were employed in an 11 minute procedure that gave a limit of detection (LOD) of approximately 2.6 x 103 spores, below the anthrax infectious dose of 104 spores. Prefabricated AgFON substrates exhibit a shelf life of ~ 40 days prior to use. The sensing capabilities of this invention can be readily incorporated into a field-portable instrument. The speed and sensitivity of this SERS sensor indicate the technology is useful for the field analysis of other potentially harmful environmental agents.
STATUS: A patent has been filed.
Richard Van Duyne, Xiaoyu Zhang, Mathew Young , Olga Lyandres
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