Raman Spectroscopy: New Perspectives for Its Clinical Application in Diagnosis

First preliminary study on identification of bacterial fish pathogens with Raman spectroscopy

Accurate and rapid determination of bacterial disease agents of fish is an important step for sustainable and efficient aquaculture production. In general, biochemical and molecular methods are used for pathogen detection but they are usually time-consuming and required qualified personnel. Recently spectroscopic methods are preferred in clinical and food microbiology and declared as a promising alternative method for pathogens diagnosis with many advantages. In this study, the significant spectra of three important bacterial fish pathogens (Lactococcus garvieae, Vibrio anguillarum and Yersinia ruckeri) were determined by Raman spectroscopy. The first data of the pathogens were obtained and the distinctive differences in polysaccharides, nucleic acids, fatty acids and amino acids were identified. This preliminary study aimed to be pioneer for further studies in aquaculture and veterinary microbiology toward developing an alternative method for routine identification.

Atomic force microscopy and Raman spectra profile of blood components associated with exposure to cigarette smoking

Tobacco smoke contains several compounds with oxidant and pro-oxidant properties with the capability of producing structural changes in biomolecules, as well as cell damage. This work aimed to describe and analyse the effect of tobacco smoke on human blood components, red blood cell (RBC) membrane, haemoglobin (Hb) and blood plasma by Atomic Force Microscopy (AFM) and Raman spectroscopy. Our results indicate that tobacco induced RBC membrane nano-alterations characterized by diminished RBC diameter and increased nano-vesicles formation, and RBC fragility. The Raman spectra profile suggests modifications in chemical composition specifically found in peaks 1135 cm⁻¹, 1156 cm⁻¹, 1452 cm⁻¹ and intensity relation of peaks 1195 cm⁻¹ and 1210 cm⁻¹ of blood plasma and by change of peaks 1338 cm⁻¹, 1357 cm⁻¹, 1549 cm⁻¹ and 1605 cm⁻¹ associated with the pyrrole ring of Hb. The relevance of these results lies in the identification of a profile of structural and chemical alterations that serves as a biomarker of physiological and pathological conditions in the human blood components induced by tobacco exposure using AFM and the Raman spectroscopy as tools for monitoring them.

Tobacco smoke contains several compounds with oxidant and pro-oxidant properties with the capability of producing structural changes in biomolecules, as well as cell damage.

A new device concept for bacterial sensing by Raman spectroscopy and voltage-gated monolayer graphene

Electron-phonon coupling in monolayer graphene results in a modification of its Raman spectra upon charge transfer processes induced by interaction with its chemical environment or the presence of strain or defects in its structure. Modification of Raman spectra is examined in order to develop ultra-sensitive biosensing techniques for the detection, identification, differentiation and classification of bacteria associated with infectious diseases. Specifically, the electrochemical properties of top gated monolayer graphene on SiO2/Si substrates, in the absence and presence of interaction with Gram-positive bacteria (Enterococcus faecalis, Bacillus subtilis) and Gram-negative bacteria (Escherichia coli and Salmonella typhimurium), are probed by Raman spectroscopy in an applied voltage range from 0 V to 3 V. Bacteria and monolayer graphene interactions are thus electrostatically tuned. The resulting correlation of specific bacterial chemical properties and Raman spectral characteristics is reported, along with density functional theory simulations of the charge transfer mechanism. The intensities of the G and D Raman vibrational modes are modulated as a function of the applied voltage in the presence of bacteria, but remain unchanged in bare monolayer graphene. A fingerprint region is also identified in the range of 200 cm-1 to 600 cm-1, with disulfide bonds observed at 490 cm-1, associated with bacterial membrane proteins. Significantly, such observations are detected even in the absence of bacterial culturing, a time-consuming step.

Isolation and identification of bacteria by means of Raman spectroscopy

Bacterial detection is a highly topical research area, because various fields of application will benefit from the progress being made. Consequently, new and innovative strategies which enable the investigation of complex samples, like body fluids or food stuff, and improvements regarding the limit of detection are of general interest. Within this review the prospects of Raman spectroscopy as a reliable tool for identifying bacteria in complex samples are discussed. The main emphasis of this work is on important aspects of applying Raman spectroscopy for the detection of bacteria like sample preparation and the identification process. Several approaches for a Raman compatible isolation of bacterial cells have been developed and applied to different matrices. Here, an overview of the limitations and possibilities of these methods is provided. Furthermore, the utilization of Raman spectroscopy for diagnostic purposes, food safety and environmental issues is discussed under a critical view.