This article reviews some of the recent advances in Raman spectroscopy, in areas related to natural tissues and cell biology. It summarizes some of the most widely used peak frequencies and their assignments. The aim of this study is to prepare a database of molecular fingerprints, which will help researchers in defining the chemical structure of the biological tissues introducing most of the important peaks present in the natural tissues. In spite of applying different methods, there seems to be a considerable similarity in defining the peaks of identical areas of the spectra. As a result, it is believed that preparing a unique collection of the frequencies encountered in Raman spectroscopic studies can lead to significant improvements both in the quantity and quality of spectral data and their outcomes. This article is the first review of its kind to provide a precise database on the most important Raman characteristic peak frequencies for researchers aiming to analyze natural tissues by Raman ...

Raman spectroscopy of biological tissues

This article reviews some of the recent advances on FTIR spectroscopy in areas related to natural tissues and cell biology. It is the second review publication resulting from a detailed study on the applications of spectroscopic methods in biological studies and summarizes some of the most widely used peak frequencies and their assignments. The aim of these studies is to prepare a database of molecular fingerprints, which will help researchers in defining the chemical structure of the biological tissues introducing most of the important peaks present in the natural tissues. In spite of applying different methods, there seems to be a considerable similarity in defining the peaks of identical areas of the FTIR spectra. As a result, it is believed that preparing a unique collection of the frequencies encountered in FTIR spectroscopic studies can lead to significant improvements both in the quantity and quality of research and their outcomes. This article is the first review of its kind that provides...

Fourier Transform Infrared (FTIR) Spectroscopy of Biological Tissues

https://web.uvic.ca/~agbrolo/ACA_GFS_MF_2011.pdf

A review on the fabrication of substrates for surface enhanced Raman spectroscopy and their applications in analytical chemistry.

The nature and properties of surface-enhanced vibrational spectra of molecules adsorbed on surfaces that can enhance the absorption and the emission of electromagnetic radiation are discussed. Examples of surface-enhanced resonant Raman scattering, surface-enhanced Raman scattering in the near-infrared and surface-enhanced infrared are given. The rough surfaces used are metal island films coated with a nanometric organic film using the Langmuir-Blodgett technique or deposited by vacuum evaporation.

/pdf/surface-enhanced-vibrational-spectroscopy-2cv91632hb.pdf

Surface enhanced vibrational spectroscopy

A rapid detection protocol suitable for use by first-responders to detect anthrax spores using a low-cost, battery-powered, portable Raman spectrometer has been developed. Bacillus subtilis spores, harmless simulants for Bacillus anthracis, were studied using surface-enhanced Raman spectroscopy (SERS) on silver film over nanosphere (AgFON) substrates. Calcium dipicolinate (CaDPA), a biomarker for bacillus spores, was efficiently extracted by sonication in nitric acid and rapidly detected by SERS. AgFON surfaces optimized for 750 nm laser excitation have been fabricated and characterized by UV-vis diffuse reflectance spectroscopy and SERS. The SERS signal from extracted CaDPA was measured over the spore concentration range of 10(-14)-10(-12) M to determine the saturation binding capacity of the AgFON surface and to calculate the adsorption constant (Kspore=1.7 x 10(13) M(-1)). At present, an 11 min procedure is capable of achieving a limit of detection (LOD) of approximately 2.6 x 10(3) spores, below the anthrax infectious dose of 10(4) spores. The data presented herein also demonstrate that the shelf life of prefabricated AgFON substrates can be as long as 40 days prior to use. Finally, these sensing capabilities have been successfully transitioned from a laboratory spectrometer to a field-portable instrument. Using this technology, 10(4) bacillus spores were detected with a 5 s data acquisition period on a 1 month old AgFON substrate. The speed and sensitivity of this SERS sensor indicate that this technology can be used as a viable option for the field analysis of potentially harmful environmental samples.

Rapid detection of an anthrax biomarker by surface-enhanced Raman spectroscopy.

The ability of surface-enhanced Raman spectroscopy (SERS) to measure the chemotherapy drug 5-fluorouracil in saliva is presented. A silver-doped sol–gel provided SERS and also some chemical selectivity. 5-Fluorouracil and physiological thiocyanate produced SERS, whereas large biochemicals, such as enzymes and proteins, did not, supporting the expectation that the larger molecules do not diffuse through the sol–gel to any appreciable extent. In addition, 5-fluorouracil samples of 2 µg ml−1 were easily measured, and an estimated limit of detection of 150 ng ml−1 in 5 min should provide sufficient sensitivity to perform pharmacokinetic studies and to monitor and regulate patient dosage. This would fill a critical need for this highly used drug, since genetic-based variations in its metabolism can range by as much as five-fold from one patient to another. Copyright © 2004 John Wiley & Sons, Ltd.

Analysis of 5-fluorouracil in saliva using surface-enhanced Raman spectroscopy

focusing the 488 nm laser beam ;2 mm deep into the bulk of the crystals to avoid contributions from potential depletion layers. As shown in Fig. 1b, the dependence of the Raman shift on the degree of deuteration is almost perfectly linear and  ts very well with D 5 22.684cm*R 1 2452.6, where D is the degree of deuteration (in %) and R is the spectral mean of the PO4 vibration in cm21. A linear correlation coef cient of 0.998 indicates an excellent linear dependence of the Raman peak shift with degree of deuteration. This result shows that the shift of the PO 4 peak is simply caused by the linear increase in atomic mass due to isotope substitution, which decreases the length of hydrogen-like bonds. This excellent linear dependence allows us to map the pro le of the D/H exchange layer at the surface of DKDP crystals by acquiring Raman spectra and determining the position of the PO 4 peak for various depths. This method is preferable over other methods such as determining the strength of the OD vibration directly (e.g., at 715 cm21), because the position of the most intense peak in the Raman spectrum can be measured more precisely than the intensity of some of the weakest peaks in the spectrum. This is demonstrated in Fig. 2, where depth-dependent Raman spectra (Fig. 2a) and the resulting exchange layer pro les for two DKDP crystals are shown (Fig. 2b). The spectra in Fig. 2a were obtained from a depth scan of a DKDP crystal with 75% degree of deuteration in the bulk, grown at 45 8C. The spectra start out as DKDP with ;30% deuteration close to the surface and approach the bulk DKDP spectrum within a few micrometers of depth. The fact that the relative degree of deuteration does not extend to 0% D is due to the limited depth resolution of the Raman microprobe, which averages over ;4 mm in depth. Figure 2b depicts the resulting D/H exchange layer pro les for this and a second crystal grown at 63 8C, respectively. Both crystals had the same exposure to ambient conditions and their main difference is the temperature at which they were grown. The different exchange layer pro les indicate that crystals grown at different temperatures have differen t proton conductiv ities ,13 which leads to a difference in their rate of deuterium depletion. The parameters controlling this behavior are currently the objective of a detailed study, the results of which will be reported elsewhere.

Rapid Dipicolinic Acid Extraction from Bacillus Spores Detected by Surface-Enhanced Raman Spectroscopy

Approximately one-third of all drugs can form hydrates, and therefore an in-depth understanding of the factors affecting anhydrate-to-hydrate transformation kinetics in a variety of environments is of interest. In this work, real-time analytical methods, in the form of Raman spectroscopy and optical microscopy, were used to establish representative transformation profiles and growth kinetics for hydrate formation of several drug substances. By comparing and contrasting the behavior of these different hydrates in terms of their specific properties such as solubility, dissolution rate, and growth rate of hydrate phase, and the influence of external factors such as seeding and agitation conditions, an increased understanding of hydrate formation has been achieved. The overall transformation rate from anhydrous to hydrate form was found to be not only a function of compound-specific properties, but was also strongly affected by surface properties and external factors such as the presence of seeds and the degr...

Toward an understanding of the factors influencing anhydrate-to-hydrate transformation kinetics in aqueous environments

The ability of surface-enhanced Raman spectroscopy (SERS) to measure 5-fluorouracil (5-FU) in saliva is presented. The approach is based on the capacity of Raman spectroscopy to provide a unique spectral signature for virtually every chemical, and the ability of SERS to provide microg/mL sensitivity. A simple sampling method, that employed 1-mm glass capillaries filled with silver-doped sol-gels, was developed to isolate 5-FU from potential interfering chemical components of saliva and simultaneously provide SERSactivity. The method involved treating a 1 mL saliva sample with 1 mL of acetic acid, drawing 10 microL of sample into a SERS-active capillary by syringe, and then measuring the SER spectrum. Quality SER spectra were obtained for samples containing as little as 2 microg of 5-FU in 1 mL saliva. The entire process, the acid pretreatment, extraction and spectral measurement, took less than 5 minutes. The SERS of 5-fluorouridine and 5-fluoro-2'-deoxyuridine, two major metabolites of 5-FU, were also measured and shown to have unique spectral peaks. These measurements suggest that disposable SERS-active capillaries could be used to measure 5-FU and metabolite concentrations in chemotherapy patient saliva, thereby providing metabolic data that would allow regulating dosage. Tentative vibrational mode assignments for 5-FU and its metabolites are also given.

https://www.mdpi.com/1420-3049/13/10/2608/pdf

Surface-enhanced Raman spectral measurements of 5-fluorouracil in saliva.

Detection of chemical agents as poisons in water supplies not only requires μg/L sensitivity, but also requires the ability to distinguish their hydrolysis products. We have been investigating the ability of surface-enhanced Raman spectroscopy (SERS) to detect chemical agents at these concentrations. Here we expand these studies and present the SERS spectra of the nerve agent VX (ethyl S-2-diisopropylamino ethyl methylphosphonothioate) and its hydrolysis products, ethyl S-2-diisopropylamino methylphosphonothioate, 2(diisopropylamino) ethanethiol, ethyl methylphosphonic acid, and methylphosphonic acid. Vibrational mode assignments for the observed SERS peaks are also provided. Overall, each of these chemicals produces a series of peaks between 450 and 900 cm−1 that are sufficiently unique to allow identification. SERS measurements were performed in silver-doped sol-gel-filled capillaries that are being developed as part of an extractive point sensor.

Alan D. Gift

Papers

Analysis of 5-fluorouracil in saliva using surface-enhanced Raman spectroscopy

Rapid Dipicolinic Acid Extraction from Bacillus Spores Detected by Surface-Enhanced Raman Spectroscopy

Toward an understanding of the factors influencing anhydrate-to-hydrate transformation kinetics in aqueous environments

Surface-enhanced Raman spectral measurements of 5-fluorouracil in saliva.

Surface-enhanced Raman spectra of VX and its hydrolysis products.