Applications of Raman spectroscopy in herbal medicine

Raman spectroscopic techniques are a group of chemical fingerprint detection methods based on molecular vibrational spectroscopy. They are compatible with aqueous solutions and are time saving, nondestructive, and highly informative. With complementary and alternative medicine (CAM) becoming increasingly popular, more people are consuming natural herbal medicines. Thus, chemical fingerprints of herbal medicines are investigated to determine the content of these products. In this study, I review the different types of Raman spectroscopic techniques used in fingerprinting herbal medicines, including dispersive Raman spectroscopy, resonance Raman spectroscopy, Fourier transform (FT)–Raman spectroscopy, surface-enhanced Raman scattering (SERS) spectroscopy, and confocal/microscopic Raman spectroscopy. Lab-grade Raman spectroscopy instruments help detect the chemical components of herbal medicines effectively and accurately without the need for complicated separation and extraction procedures. In addition, portable Raman spectroscopy instruments could be used to monitor the health and safety compliance of herbal products in the consumer market.     

Quantitative analysis of solid-phase mixtures by Raman spectroscopy

We propose a method for using Raman spectroscopy to determine the phase compositions and concentrations in solid-phase equilibrium mixtures. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 416–418, May–June, 2008.     

Recent advances in linear and nonlinear Raman spectroscopy II

Following the first review on recent advances in linear and nonlinear Raman spectroscopy, the present review summarizes papers mainly published in the Journal of Raman Spectroscopy during 2007. This serves to give a fast overview of recent advances in this research field as well as to provide readers of this journal a quick introduction to the various subfields of Raman spectroscopy. It also reflects the current research interests of the Raman community. Similar reviews of highly active areas of Raman spectroscopy will appear in future issues of this journal. Copyright © 2008 John Wiley & Sons, Ltd.     

Nasopharyngeal carcinoma detection by tissue smears using surface-enhanced Raman spectroscopy

Nasopharyngeal carcinoma is one of the most common malignant neoplasms in head and neck. In this work, surface-enhanced Raman spectroscopy technique was used to study the molecular differences between cancerous and noncancerous smear samples which were obtained after clinical biopsy by smearing the tissue on the slides. Principal component analysis combined with linear discriminant analysis provided a sensitivity of 79.4% and a specificity of 81.8% for differentiation between cancerous and noncancerous nasopharyngeal tissue smears. This work provides a good basis for the methodology of nasopharyngeal tissue smear based on surface-enhanced Raman spectroscopy technique and is worth further studying.     

Characterizing variability in in vivo Raman spectroscopic properties of different anatomical sites of normal tissue in the oral cavity

Raman spectroscopy is an inelastic light scattering technique that is capable of probing biochemical and biomolecular structures and conformations of tissue. This study aims to characterize the in vivo Raman spectroscopic properties of different normal oral tissues in the fingerprint region (800–1800 cm⁻¹) and to assess distinctive biochemical variations of different anatomical regions in the oral cavity. A specially designed fiber‐optic Raman probe with a ball lens was utilized for real‐time, in vivo Raman measurements of various oral tissue sites (i.e. inner lip, attached gingiva, floor, dorsal tongue, ventral tongue, hard palate, soft palate, and buccal). The semiquantitative non‐negativity‐constrained least squares minimization fitting of reference biochemicals representing oral tissue constituents (i.e. hydroxyapatite, keratin, collagen, DNA, and oleic acid) and partial least squares‐discriminant analysis (PLS‐DA) were employed to assess the significance of inter‐anatomical variability. A total of 402 high‐quality in vivo oral Raman spectra were acquired from 20 subjects. The histological characteristics of different oral tissues were found to have influence on the in vivo Raman spectra and could be grossly divided into three major clusterings: (1) buccal, inner lip, and soft palate; (2) dorsal, ventral tongue, and floor; (3) gingiva and hard palate. The PLS‐DA multiclass algorithms were able to identify different tissue sites with varying accuracies (inner lip 83.1%, attached gingiva 91.3%, floor 86.1%, dorsal tongue 88.8%, ventral tongue 83.1%, hard palate 87.6%, soft palate 83.3%, and buccal mucosa 85.3%), bringing out the similarities among different oral tissues at the biomolecular level. This study discloses that inter‐anatomical variability is significant and should be considered as an important parameter in the interpretation and rendering of Raman diagnostic algorithms for oral tissue diagnosis and characterization. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman spectroscopy detects melanoma and the tissue surrounding melanoma using tissue-engineered melanoma models

Invasion of melanoma cells from the primary tumor involves interaction with adjacent tissues and extracellular matrix. The extent of this interaction is not fully understood. In this study Raman spectroscopy was applied to cryo-sections of established 3D models of melanoma in human skin. Principal component analysis was used to investigate differences between the tumor and normal tissue and between the peri-tumor area and the normal skin. Two human melanoma cells lines A375SM and C8161 were investigated and compared in 3D melanoma models. Changes were found in protein conformations and tryptophan configurations across the entire melanoma samples, in tyrosine orientation and in more fluid lipid packing only in tumor dense areas, and in increased glycogen content in the peri-tumor areas of melanoma. Raman spectroscopy revealed changes around the perimeter of a melanoma tumor as well as detecting differences between the tumor and the normal tissue.     

Applications of Raman spectroscopy in detection of water quality

Water pollution is hazardous to the health of humans and other organisms, and detection of pollutants in aquatic environments is of primary importance for water quality monitoring. Raman spectroscopy offers an effective tool for qualitative analysis and quantitative detection of contaminants in a water environment. This article focuses on applications of Raman spectroscopy for detection of water quality. In this article, various Raman spectroscopy techniques employed for water quality detection are presented based on the types of pollutants: organics, inorganics, and biological contaminants. Additionally, the relevant detection parameters are reviewed, such as detection materials, limit of detection, detection range, peak positions, and selectivity. Furthermore, the advantages and limitations of various Raman spectroscopy techniques are summarized. Finally, the future development of Raman spectroscopy for detection of water quality is discussed.     

喇曼感生克尔效应光谱的琼斯矩阵分析

介绍喇曼感生克尔效应光谱(RIKES)的琼斯(Jones)矩阵分析方法.探测光束的传输强度不仅由所经过的每一个光学器件的琼斯矩阵所决定,而且还受到强的泵波在非线性介质样品中感生依赖于强度的二向色性和双折射(克尔效应)对琼斯矩阵的影响.同时计及样品和光学器件由强泵波作用下感生应力和其他外部产生的线双折射对喇曼感生克尔效应光谱观察的不利影响,导出测量系统的功率传输函数的完整表达式和喇曼感生克尔效应光谱的实现观察条件,最后简述以甲笨(C_7H_8)液体为试样的喇曼感生克尔效应光谱实验结果分析.     

Quantitative analysis of alcohol-water binary solutions using Raman spectroscopy

Raman spectroscopy was used for rapid and in situ measurements of alcohols in alcohol-water binary systems. An external standard was used to eliminate factors such as laser power or instrumental effects. Band ratios between the Raman bands of the target molecule and that of acetonitrile as external standard were calculated and found to be proportional to the mass fraction of alcohol. Better linearity was achieved as compared with that in the calibration curve obtained by plotting the Raman intensity alone. The equations of the calibration curves were y=0.2747x with R² of 0.9996 and y=0.2189x+1.340×10⁻³ with an R² of 1.000 in methanol-water and in ethanol-water binary systems, with y and x denoting the Raman intensity ratio and the mass fraction of alcohol, respectively.     

凝聚态物质中的光声喇曼效应理论

用热弹性理论系统地分析了凝聚态物质的光声喇曼效应,分别导出了连续和脉冲激光泵浦下的光声喇曼信号表达式,并做了数值估算.     

Raman spectroscopy monitoring of the cellular activities of a tissue‐engineered ex vivo produced oral mucosal equivalent

To ensure quality control and assurance in tissue engineering, noninvasive, real‐time and aseptic evaluation of cell‐based devices is required before product release. In this study, Raman spectroscopy was applied to monitor the cellular activities of an oral mucosa equivalent (EVPOME) produced ex vivo from cultured autogenous oral keratinocytes and acellular dermis—AlloDerm. Raman spectra showed a positive correlation of the peak area ratio of amide I (1655 cm⁻¹)/phenylalanine (1004 cm⁻¹) with a negative linear regression (R² > 0.95) according to the number of cultured days, especially on the 14thand 21st day. This work demonstrates the successful application of Raman spectroscopy for quantitatively monitoring and evaluating the maturity of EVPOME. Copyright © 2010 John Wiley & Sons, Ltd.     

Applications of Raman Spectroscopy in Dentistry: Analysis of Tooth Structure

Abstract: Tooth enamel is the most mineralized tissue in the human body, and in this article the use of Raman spectroscopy for the analysis of tooth structure, a comparison with synthetic apatites, and use in dentistry are described. Spectral peaks that are related to dental hard and soft tissues are discussed, which provide crucial data in understanding the chemical structural properties of dentin and enamel. The Raman spectrum of dentin confirms the presence of crystalline phosphate-based minerals in dentin. Both dentin and enamel consist of two primary components: an inorganic or mineral phase that closely resembles hydroxyapatite and the Raman spectrum of dentin that confirms the presence of crystalline phosphate-based minerals in dentin. Hence, the mineral phase in dentin and enamel may be characterized essentially as nonstoichiometric substituted apatite. The presence of carbonate (A and B type) incorporated in the hydroxyapatite lattice is also confirmed by the presence of spectral bands. The organic phase, which is mainly composed of type I collagen, is confirmed by the spectral bands of amide I and amide II bands, tryptophan, and phenylalanine. Furthermore, these spectral bands associated with organic and inorganic parts of the enamel and dentin are useful in predicting early formation of carries formation.     

Identification of oxygen in dental enamel following tooth bleaching using confocal micro Raman spectroscopy

Oxygen is a polymerization inhibitor of 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloxypropoxy) phenyl]propane (Bis‐GMA) and triethylene glycol dimethacrylate, a basic constituent of most dental adhesive materials. Some hypothesis that oxygen remains in tooth mineralized tissues following some dental treatments and thus reducing adhesive forces and compromising the restorative treatments, have been advanced, but no experimental demonstration has been conducted. We used for the first time a confocal micro Raman technique to successfully identify the presence of oxygen generated by tooth bleaching products in tooth enamel surface, hence, helping to provide confirmation for this theory. This new data result from a multidisciplinary research approach between physics and dentistry is pioneering and could in the future support dental treatment protocol changes, increasing productivity and patient's benefits. Copyright © 2012 John Wiley & Sons, Ltd.     

激光拉曼光谱分析氢同位素的应用

拉曼光谱作为一种物质结构和成分分析的测试手段而被广泛应用.介绍分析了激光拉曼光谱法用于氢同位素分析的可行性,并综述介绍了国内外研究人员利用激光拉曼光谱在氚参与的放射反应监测分析、氢同位素定性检测、定量分析方法研究等方面开展的工作.     

Recent Advances in linear and nonlinear Raman spectroscopy I

Raman spectroscopy has advanced considerably in the last several years due to rapid developments in instrumentation and the availability of theoretical methods for accurate calculation of Raman spectra, thus enormously facilitating the interpretation of Raman data. This review is restricted to cover papers mainly published in the Journal of Raman Spectroscopy, which serve to give a fast overview of recent advances in this research field as well as to provide readers of this journal a quick introduction to the various subfields of Raman spectroscopy. It also reflects the current research interests of the Raman community. Similar reviews of highly active areas of Raman spectroscopy will appear in future issues of this journal. Copyright © 2007 John Wiley & Sons, Ltd.     

Raman spectroscopic investigation of frozen and deparaffinized tissue sections of pediatric tumors: neuroblastoma and ganglioneuroma

Raman spectroscopy is a nondestructive technique that can provide information at the molecular level about the biochemicals in tissues. We have investigated the cellular regions in neuroblastoma and ganglioneuroma using Raman spectroscopy and compared their spectral characteristics with those of the corresponding normal adrenal gland. Thin sections from both the frozen and the corresponding formalin‐fixed paraffin‐processed (FFPP) tissues were studied in conjunction with the pathological examination of the tissues. Investigation of the spectral data shows that the normal adrenal gland tissues have higher levels of carotenoids, lipids, and cholesterol compared with the neuroblastoma and ganglioneuroma frozen tissues. However, in comparison with the frozen tissues, the FFPP tissues show a significant alteration of several biochemicals, including the complete removal of carotenoids, lipids, and cholesterol in the adrenal tissues. A quantitative analysis using chemometric methods of principal component analysis and discriminant function analysis of the Raman spectral data obtained from the frozen tissues show a clear‐cut classification among pathological groups with high sensitivity and specificity. We have validated the classification results of the FFPP tissues against a training set data obtained from the archived FFPP tissues of nine other patients. The validation process correctly identified and grouped the data with the training set of normal adrenal gland (>97% of the time) and neuroblastoma (100% of the time) tissues, whereas the validation was not so strong for ganglioneuroma. This study shows that Raman spectroscopy combined with chemometric methods can be successfully used to distinguish neuroblastoma and ganglioneuroma at cellular level in frozen tissue sections. This study also shows that formalin fixation and paraffinization/deparaffinization of tissues can alter their biochemical composition. Copyright © 2012 John Wiley & Sons, Ltd.     

In vitro analysis of immersed human tissues by Raman microspectroscopy

Raman microspectroscopy is a powerful tool for the analysis of tissue sections, providing a molecular map of the investigated samples. Nevertheless, data pre‐processing and, particularly, the removal of the broad background to the spectra remain problematic. Indeed, the physical origin of the background has not been satisfactorily determined. Using 785 nm as source in a confocal geometry, it is demonstrated for the example of the protein kappa‐elastin that the background and resulting quality of the recorded spectrum are dependent on the morphology of the sample. Whereas a fine powder yields a dominant broad background, compressed pellets and solution‐cast thin films produce, respectively, improved quality spectra and significantly reduced spectral background. As the chemical composition of the samples is identical, the background is ascribed to stray light due to diffuse scattering rather than an intrinsic photoluminescence. The recorded spectra from a tissue sample exhibit a large and spatially variable background, resulting in poorly defined spectral features. A significant reduction of the background signal as well as improvement of the spectral quality is achieved by immersion of the sample in water and measurement with an immersion objective. The significant improvement in signal to background is attributed to a reduction of the diffuse scattering due to a change in the effective morphology as a result of an improved index matching at the water/tissue interface compared to the air/tissue interface. Compared to sections measured in air, the background is reduced to that of the water, and pre‐processing is reduced to the subtraction of the substrate and water signal and correction for the instrument response, both of which are highly reproducible. Data pre‐processing is thus greatly simplified and the results significantly more reliable. Copyright © 2010 John Wiley & Sons, Ltd.     

Application of portable Raman spectroscopy and benchtop spatially offset Raman spectroscopy to interrogate concealed biomaterials

In this paper, we demonstrate the ability of portable Raman spectroscopy and benchtop spatially offset Raman spectroscopy (SORS) techniques to rapidly identify real and fake ivory samples. Both techniques were able to identify exposed genuine from fake ivory samples. In contrast to conventional Raman spectroscopy, SORS was, in addition, able to identify ivory concealed by plastics, paints, varnishes and cloth. Application of the SORS technique allows the interrogation of biomaterial samples through materials in which conventional Raman spectroscopic instrumentation cannot penetrate. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopy for the analysis of coal: a review

The advances in the characterization of amorphous carbons by Raman spectroscopy over the last four decades are of interest to many industries, especially those involving the combustion, gasification and pyrolysis of coal. Many researchers report on the Raman character of the natural organic matter in carbon‐containing compounds, such as coal, and relate the Raman bands to the structural order of the amorphous carbons. The basis of most of these studies evolved around the assignment of the G (graphitic, ∼1580 cm⁻¹) band to crystalline graphite and any other bands, called D bands, (disorder, various from 1100 to 1500 cm⁻¹) to any type of structural disorder in the graphitic structure. Concerning coal analysis, the information gained by Raman investigations has been used to describe char evolution as a function of temperature, the presence of catalysts and different gasification conditions. In addition, researchers looked at maturation, grade, doppleritization and many more aspects of interest. One aspect that has, however, not been addressed by most of the researchers is the natural inorganic matter (NIM) in the carbon‐containing compounds. Micro‐Raman spectroscopy (MRS) has many advantages over other characterization tools, i.e. in situ analysis, nondestructive, no sample preparation, low detection limit, micrometer‐scale characterization, versatility and sensitivity to many amorphous compounds. With the distinct advantages it has over that of other molecular characterization tools, such as powder X‐ray diffraction (PXRD), Fourier‐transform infrared spectrometry (FT‐IR) and scanning electron microscopy with X‐ray detection (SEM/EDS), it is surprising that it has not yet been fully exploited up to this point for the characterization of the NIM in coal and other amorphous carbons. This paper reviews the work published on the Raman characterization of the natural organic matter (NOM) of coals and reports on preliminary results of the NIM character of various South African coals, whereby various inorganic compounds and minerals in the coal have been characterized. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopy in experimental oral carcinogenesis: investigation of abnormal changes in control tissues

Oral cancer is a major cause of mortality in South Asian men owing to rampant tobacco abuse. Cancers are also reported in non‐tobacco habitués, especially women, attributed to chronic irritations from irregular/sharp teeth, improper fillings, and poorly fit dentures. Conventional screening approaches are shown to be effective for high‐risk groups (tobacco/alcohol habitués). Raman spectroscopy (RS) is being extensively explored as an alternate/adjunct tool for diagnosis and management of oral cancers. In a previous Raman study on sequential oral carcinogenesis using hamster buccal pouch model, misclassifications between spectra from control and carcinogen [7,12‐dimethylbenz(a)anthracene (DMBA)]‐treated tissues were observed. Histopathology of some control tissues suggested pathological changes, attributable to repeated forceps‐induced irritations/trauma during animal handling. To explore these changes, in the present study, we recorded spectra from three different types of controls – vehicle control (n = 45), vehicle contralateral (n = 45), and DMBA contralateral (n = 70) – exposed to varying degree of forceps handling, along with DMBA‐treated pouches (n = 70) using a 14‐week carcinogenesis protocol. Spectra certified on the basis of histopathology and abnormal cell proliferation (cyclin D1 expression) were used to build models that were evaluated by independent test spectra from an exclusive set of DMBA‐treated and control animals. Many DMBA‐contralateral, vehicle‐control, and vehicle‐contralateral spectra were identified as higher pathologies, which subsequently corroborated with histopathology/cyclin D1 expression. Repeated forceps‐mediated injuries/irritations, during painting and animal handling, may elicit inflammatory responses, leading to neoplasm. The findings of the study suggest that RS could identify micro‐changes. Further, RS‐based in vivo imaging can serve as a promising label‐free tool for screening even in the non‐habitué population where conventional screening is shown to be not effective. Copyright © 2016 John Wiley & Sons, Ltd.