Characterization of the Surface Enhanced Raman Scattering (SERS) of Bacteria

Abstract

The surface enhanced Raman scattering (SERS) of a number of species and strains of bacteria obtained on novel gold nanoparticle (approximately 80 nm) covered SiO(2) substrates excited at 785 nm is reported. Raman cross-section enhancements of >10(4) per bacterium are found for both Gram-positive and Gram-negative bacteria on these SERS active substrates. The SERS spectra of bacteria are spectrally less congested and exhibit greater species differentiation than their corresponding non-SERS (bulk) Raman spectra at this excitation wavelength. Fluorescence observed in the bulk Raman emission of Bacillus species is not apparent in the corresponding SERS spectra. Despite the field enhancement effects arising from the nanostructured metal surface, this fluorescence component appears "quenched" due to an energy transfer process which does not diminish the Raman emission. The surface enhancement effect allows the observation of Raman spectra of single bacterial cells excited at low incident powers and short data acquisition times. SERS spectra of B. anthracis Sterne illustrate this single cell level capability. Comparison with previous SERS studies reveals how the SERS vibrational signatures are strongly dependent on the morphology and nature of the SERS active substrates. The potential of SERS for detection and identification of bacterial pathogens with species and strain specificity on these gold particle covered glassy substrates is demonstrated by these results.

Raman spectroscopy: techniques and applications in the life sciences

“…Bacteria discrimination was first shown with Ag colloid SERS, showing discrimination at the strain level for E. Coli [319]. Differences in SERS spectra of various other bacteria species was also shown shortly after [320], and was shown to be potentially useful for bacteria 'barcoding' using multivariate statistics [321]. Different Ag NPs used for SERS were investigated for their antibacterial activity, and it was found that smaller (18 nm) were more toxic to bacteria than 80nm [322].…”

Plataformas nanoestructuradas de plata para identificación cualitativa de Escherichia coli mediante espectroscopia Raman intensificada por efecto de superficie “prueba de concepto del sistema”

“…Posteriormente, producto de la presencia de las bacterias y su interacción con el láser incidente, los pilares se alinean entre sí creando de este modo hot spots (zonas de aumento de campo electromagnético) que incrementan la intensidad de la señal Raman. Este mismo efecto ha sido utilizado para explicar el efecto SERS en otros estudios, utilizando sustratos diferentes [3,7,[16][17][18][19].…”

“…Entre las más utilizadas se encuentran: evaporación al vacío, deposición electroquímica, pulverización catódica (sputtering) y plateo electroquímico [2][3][4]. Otra alternativa la constituyen los métodos basados en la nanoimpresión de metales sobre superficies de silicio, técnica conocida como nanolitografía.…”

Surface-enhanced Raman scattering biomedical applications of plasmonic colloidal particles

“…Increasing in complexity, the detection and classification of pathogenic micro-organisms (viruses, bacteria, yeast, fungi and protozoa) (Alexander 2008;Jarvis & Goodacre 2008;Tripp et al 2008) and bacteria (Premasiri et al 2005;Evanoff et al 2006), as well as the study of complex tissues (Pinzaru et al 2008), have been largely improved through improvements in optical spectroscopy (i.e. spectral spatial resolution) and nanoparticle synthesis.…”