Label-Free SERS Discrimination and In Situ Analysis of Life Cycle in Escherichia coli and Staphylococcus epidermidis

Abstract

Surface enhanced Raman spectroscopy (SERS) has been proven suitable for identifying and characterizing different bacterial species, and to fully understand the chemically driven metabolic variations that occur during their evolution. In this study, SERS was exploited to identify the cellular composition of Gram-positive and Gram-negative bacteria by using mesoporous silicon-based substrates decorated with silver nanoparticles. The main differences between the investigated bacterial strains reside in the structure of the cell walls and plasmatic membranes, as well as their biofilm matrix, as clearly noticed in the corresponding SERS spectrum. A complete characterization of the spectra was provided in order to understand the contribution of each vibrational signal collected from the bacterial culture at different times, allowing the analysis of the bacterial populations after 12, 24, and 48 h. The results show clear features in terms of vibrational bands in line with the bacterial growth curve, including an increasing intensity of the signals during the first 24 h and their subsequent decrease in the late stationary phase after 48 h of culture. The evolution of the bacterial culture was also confirmed by fluorescence microscope images.

Dual-Approach Electrochemical Surface-Enhanced Raman Scattering Detection of Mycobacterium tuberculosis in Patient-Derived Biological Specimens: Proof of Concept for a Generalizable Method to Detect and Identify Bacterial Pathogens

“…Moreover, in the current study, another visually distinguishable mode typically observed across all four mycobacterium-based SERS spectra is the band at ∼ 730 (±2) cm −1 , which typically represents the ring breathing mode of adenine and also may be ascribed to the presence of extracellular DNA (or other common adenine-containing molecules). 39 Other characteristic bands common to all four spectra include representative modes for the following (i) nucleic acid-related phosphate group-based (∼1132−1133 cm −1 ), (ii) protein-related amide III-based (∼1227−1231 cm − ), (iii) lipid/fatty acid-based (∼1315−1447 cm −1 ), (iv) amide II-based (∼1534−1539 cm −1 ), and (v) protein-based (∼1572−1575 cm − ) spectra. It must also be emphasized that depending on the mycobacterial species/strain, these common features are accompanied by small but notable differences in SERS wavenumbers, line widths, and relative peak intensities (exact assignments and positions are tabulated in Table S1).…”

Combining acoustic bioprinting with AI-assisted Raman spectroscopy for high-throughput identification of bacteria in blood

“…25) [55,[60][61][62][63][64][65][66][67][68][69][70]. We specifically note that peaks at 732.5 and 1330 cm -1 from our S. epi -containing samples are attributed to purine ring-breathing modes [65] and the Adenine part of the flavin derivatives or glycosidic ring mode of polysaccharides [64]; peaks at 755 and 1450 cm -1 from our E. coli -containing samples are attributed to Tryptophan ring breathing [70] and CH 2 /CH 3 deformation of proteins and lipids [62]; and peaks at 482 and 1124 cm -1 from our RBC-containing samples are attributed to γ12 out of plane deformation of porphyrin, a main component of hemoglobin [67], and ν13 or ν42 valence [68]. Further peak assignments can be found in Supplementary Table 1.…”

Applications of Surface-Enhanced Raman Scattering in Biochemical and Medical Analysis

“…For example, a SERS-active platform based on a polymer nanofiber mat has been shown to be a reliable SERS surface for detecting Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella typhimurium in blood plasma at a concentration of 10 3 colony forming unit/ml (Witkowska et al, 2017). Also, the identification of the cellular composition of Gram-positive and Gram-negative bacteria by using mesoporous silicon-based substrates decorated with silver nanoparticles was carried out, and spectral differences were noticeable regarding their different cell cycles (Paccotti et al, 2018).…”