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Gold Nanomaterials at Work in Biomedicine *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Xuan Yang, Miaoxin Yang, Pang Bo, Madeline Vara, Younan Xia
Surface-enhanced Raman scattering refers to an optical phenomenon by which the Raman scattering cross section can be increased by more than 6 orders in magnitude when the probe molecules are deposited on a roughened metal surface [17, 18, 372–376]. This phenomenon was first observed by Fleischmann in 1974 for pyridine molecules adsorbed on the surface of an electrochemically roughened Ag electrode [377], and a plausible mechanism was independently proposed in 1977 by Van Duyne [378] and Creighton [379]. In such a process, the extremely small cross section (typically, 10−31–10−29 cm2 per molecule) of Raman scattering can be drastically augmented to enable the use of Raman spectroscopy as a routine technique for ultrasensitive detection [380]. This technique has found widespread use in both analytical chemistry and life sciences owing to the unique advantages provided by Raman spectroscopy, including (i) ease of sample preparation, (ii) availability of characteristic peaks for label-free “fingerprinting” of an analyte, (iii) narrow peak width for multiplexing, (iv) good stability toward photobleaching, and (v) excitation by a single wavelength laser [380–382].
Molecular Vibrational Imaging by Coherent Raman Scattering
Published in Shoogo Ueno, Bioimaging, 2020
Yasuyuki Ozeki, Hideaki Kano, Naoki Fukutake
Raman scattering is an inelastic light scattering phenomenon involving the molecular vibration of substances that interact with light, providing the vibrational spectrum of molecules. It has been applied to biological microscopic imaging to acquire the spatial distribution of biomolecules. However, the intensity of Raman scattering is quite weak, requiring a long acquisition time. Coherent Raman scattering (CRS) microscopy using two-color and/or broadband laser pulses drastically improved the imaging speed and sensitivity of Raman imaging. CRS microscopy can be classified into several types, including coherent anti-Stokes Raman scattering (CARS) microscopy [1,2] and stimulated Raman scattering (SRS) microscopy [3–5]. Recent advancements in the instrumentations of CRS microscopy have drastically enhanced its chemical specificity and imaging speed. Currently, the advantages and disadvantages of CARS and SRS are growing conspicuous: CARS microscopy is advantageous in acquiring broadband vibrational spectra [6,7], whereas SRS is useful for high-speed and sensitive analysis of vibrational spectra in a relatively narrow bandwidth [8–12]. Currently, CRS microscopy is widely applied to label-free imaging of metabolites and drugs in different types of biological cells and tissues. Furthermore, with the recent advent of Raman-detectable labeling technologies, CRS microscopy has been finding novel applications, such as metabolic analysis of small biomolecules [13–15], which were previously difficult with the earlier fluorescent labeling techniques.
Fluorescent Analysis Technique
Published in Victoria Vladimirovna Roshchina, Fluorescence of Living Plant Cells for Phytomedicine Preparations, 2020
Victoria Vladimirovna Roshchina
The use of Raman spectroscopy in microscopy enables label-free and chemically selective imaging, which has become important in recent years. Molecular identification originates from the specific frequencies of molecular vibrations appearing in a Raman spectrum. A drawback is that spontaneous Raman scattering is a very weak optical effect compared with fluorescence or elastic light scattering. Approximately only one or fewer of 106 photons of scattered light undergoes an energy loss or gain, so-called Stokes and anti-Stokes Raman scattering, through interaction with the molecular vibrations. The imaging of a typical biological sample with Raman microscopy is not always suitable, because it requires very long image acquisition times, even when intense laser beams are used.
Updated insight into the characterization of nano-emulsions
Published in Expert Opinion on Drug Delivery, 2023
Xinyue Wang, Halina Anton, Thierry Vandamme, Nicolas Anton
In another example, Wang et al. [91] used Raman spectroscopy as a quantification method for α-tocopherol content in oil-in-water emulsion, and compared the obtained results with HPLC. Interestingly, Raman spectroscopy showed a comparable accuracy to HPLC. In addition this approach allowed to follow the homogeneity of the α-tocopherol distribution within the droplet, with the evolution of their spectral signature. These authors disclosed a gradual segregation of α-tocopherol in the interfacial region. Although Raman spectroscopy provides a convenient way for component analysis, in the case of complex mixtures, the analysis of the fingerprinting peaks becomes relatively complex. Moreover, low Raman scattering intensity resulting in low sensitivity of the method is the main limit for applying this experimental approach in routine or industrial scale.
In vivo spectroscopy: optical fiber probes for clinical applications
Published in Expert Review of Medical Devices, 2022
Ajaya Kumar Barik, Sanoop Pavithran M, Jijo Lukose, Rekha Upadhya, Muralidhar V Pai, V.B. Kartha, Santhosh Chidangil
In the simplest configuration, a single-fiber probe can be used for both incidence radiation and collection of light radiation emanating from the sample. Separation of the two radiations is achieved at the spectrometer level, using appropriate dichroic mirrors and filters, as shown in Figure 1b. All the other optical components are external to the fiber probe, such a system has several advantages. The main units of the system incidence laser, spectrometer, and all required optics can be enclosed in a single portable unit, with only the flexible probe to be handled by the observer. Such a probe can be easily incorporated into conventional endoscopic equipment allowing the adaptation of suitable endoscopes for spectroscopic studies. The major disadvantage of the single fiber probe is that because only one fiber is used for incidence and collection, the signal collected will be only a fraction of the total Raman/Fluorescence signal. Since fluorescence signals are quite strong, such systems are sufficient for fluorescence spectroscopy; while the inherently low efficiency of the Raman scattering process, these probes are not good for the observation of Raman spectra.
Comparison of Wash-out Properties after Use of the Vital Dye Trypan Blue in the Form of an Ophthalmic Dye and Bound in a Sodium Hyaluronate by Raman Spectroscopy
Published in Current Eye Research, 2021
Andreas F. Borkenstein, Eva-Maria Borkenstein, Johannes Rattenberger, Harald Fitzek, Achim Langenbucher
Raman spectroscopy is based on the inelastic scattering of light to matter, the so-called Raman scattering. Unlike elastic scattering, in which the photon scattering occurs mostly without energy loss (Rayleigh scattering), a very small part of the photons is scattered at a different frequency (Raman scattering). All Raman measurements in our evaluation were performed with the LabRam 800 HR spectrometer (Horiba Jobin Yvon GmbH, Bensheim, Germany) equipped with a 1024 × 256 CCD camera (Peltier-cooled) adapted to an Olympus BX41 microscope. All measurements were carried out with a laser wavelength of 532 nm (5 mW), an integration time of 1 s per sweep and an Olympus x10 MPlanN (NA = 0. 25) lens. Each spectral image that scans pixel by pixel and has a full spectrum per pixel has a total size of 7200 × 6800 μm with a step width of 50 μm and uses the DuoScanTM imaging system to map the laser focus to the pixel size.