title: Nanoscale chemical imaging of Bacillus subtilis spores by combining tip-enhanced Raman scattering and advanced statistical tools.
abstract: Tip-enhanced Raman Scattering (TERS) has recently emerged as a powerful spectroscopic technique capable of providing subdiffraction morphological and chemical information on samples. In this work, we apply TERS spectroscopy for surface analysis of the Bacillus subtilis spore, a very attractive biosystem for a wide range of applications regulated by the spore surface properties. The observed spectra reflect the complex and heterogeneous environment explored by the plasmonic tip, therefore exhibiting significant point-to-point variations at the nanoscale. Herein, we demonstrate that TERS data processing via principal component analysis allows handling such spectral changes, thus enabling an unbiased correlative imaging based on TERS. Our experimental outcomes suggest a denser arrangement of both proteins and carbohydrates on specific spore surface regions simultaneously revealed by AFM phase imaging. Successful TERS analysis of spores' surface is useful for bacterial surface-display systems and drug delivery applications.
authors.affiliation: Department of Physics and ‡Department of Biology, University of Naples Federico II , via Cintia, 80126-I Naples, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Rusciano
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Zito
authors.forename: Rachele
authors.initials: R
authors.lastname: Isticato
authors.forename: Teja
authors.initials: T
authors.lastname: Sirec
authors.forename: Ezio
authors.initials: E
authors.lastname: Ricca
authors.forename: Elena
authors.initials: E
authors.lastname: Bailo
authors.forename: Antonio
authors.initials: A
authors.lastname: Sasso
mesh_terms: D001412:Bacillus subtilis; D036103:Nanotechnology / Q000379:methods*; D025341:Principal Component Analysis; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013171:Spores, Bacterial
keywords: Bacillus subtilis; chemical imaging; principal component analysis (PCA); tip-enhanced Raman scattering