Bioaerosol characterization by surface-enhanced Raman spectroscopy (SERS)

It is demonstrated that bioaerosols can be characterized by their surface-enhanced Raman spectra. Preliminary studies showed that Raman spectra of aqueous suspensions of Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhimurium can be obtained by mixing them with a nanocolloidal suspension of silver. Adsorption of the microorganisms on the silver quenches fluorescence and yields greatly enhanced spectra. To assist in the interpretation of the spectra we also obtained SERS spectra of N-acetyl glucosamine and the amino acids L-lysine, D-alanine and D-glutamic acid. After baseline studies identified the spectral region of interest and the concentrations of microorganisms and colloid particles needed to maximize the Raman signal, aerosolized microorganisms were impacted and transferred to a colloidal suspension of silver nanoparticles to obtain reproducible Raman spectra.