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Molecules
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The Role of Raman Spectroscopy in Analytical Sciences
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The Role of Raman Spectroscopy in Analytical Sciences

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Analytical Chemistry".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 10303

Special Issue Editors

Prof. Dr. Igor Chourpa

E-Mail Website
Guest Editor
Faculty of Pharmacy, University of Tours, 37000 Tours, France
Interests: Raman and surface-enhanced Raman spectroscopy; plasmonic nanosystems; hyperspectral imaging; bioanalytical chemistry
Dr. Franck Bonnier

E-Mail Website
Guest Editor
Faculty of Pharmacy, University of Tours, 37000 Tours, France
Interests: vibrational spectroscopy; analytical chemistry; quality control; quantitative analysis; hyperspectral imaging; chemometrics; biomedical applications; cosmetic sciences

Special Issue Information

Dear Colleagues, 

Raman spectroscopy (RS) is a vibrational spectroscopy technique delivering the specific molecular fingerprint of various samples based on their interaction with light (inelastic scattering), in a non-destructive and label-free manner. Raman spectral signatures allow for the specific identification of molecules and thus encompass information about the chemical composition of the sample, in terms of major species and sometimes of impurities or contaminants. As a result, a Raman spectrum is considered a unique profile with signal intensity directly proportional to concentration. Raman spectroscopy is also suited to the study of molecular conformations and interactions. Less numerous than in IR spectra due to different selection rules, Raman bands enable better resolution of mixed signals, and are useful for multiplex detection as well as the analysis of complex samples. In addition to a semi-quantitative analysis of complex samples where the relative band intensities are connected to the relative content of the species, determination of their absolute concentrations becomes possible with the advent of multivariate analysis.

Developments in multivariate analysis as well as the progress in Raman instrumentation have opened a new era with very promising perspectives for RS in the analytical sciences. The role of RS has strengthened over the last several decades and it is on the verge of becoming an established tool for routine analysis in research facilities, as well as in industry for applications such as quality control or PAT (Process Analytical Technology). The field has significantly broadened in recent years with an enriched spectrum of devices, starting from portable and handheld Raman instruments and going to PAT-dedicated set-ups and reaching powerful imaging tools such as coherent anti-Stokes Raman spectroscopy (CARS) and stimulated Raman scattering (SRS).

The current Special Issue aims to gather a collection of papers illustrating current analytical applications and challenges of Raman spectroscopy, both the conventional technology and its variants, based either on nanotechnology (e.g., surface-enhanced Raman spectroscopy (SERS) or tip-enhanced Raman spectroscopy (TERS)) or on non-linear microscopy (e.g., CARS and SRS). A broad range of fields (biomedical, chemistry, pharmaceutics, cosmetics, food industry, etc.) are expected to be represented.

Prof. Dr. Igor Chourpa
Dr. Franck Bonnier
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Raman spectroscopy
  • analytical applications
  • data pre-processing
  • data analysis
  • benchtop Raman analysis
  • handheld
  • microscopy
  • imaging
  • quantitative analysis
  • chemical mapping

Published Papers (5 papers)

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Research

15 pages, 2897 KiB  
Article
Single versus Double Coffee-Ring Effect Patterns in Thin-Layer Chromatography Coupled with Surface-Enhanced Raman Spectroscopic Analysis of Anti-Diabetic Drugs Adulterated in Herbal Products
by Dao Thi Cam Minh, Le Thi Bao Tram, Nguyen Hai Phong, Hoang Thi Lan Huong, Le Van Vu, Le Anh Thi, Nguyen Thi Kieu Anh and Pham Thi Thanh Ha
Molecules 2023, 28(14), 5492; https://doi.org/10.3390/molecules28145492 - 18 Jul 2023
Viewed by 1115
Abstract
In thin-layer chromatography coupled with surface-enhanced Raman spectroscopy (TLC-SERS), the coffee ring effect (CRE) describes the formation of a ring-shape spot (blank in the middle and darker on the edge) caused by the aggregation of silver nanoparticles (Ag NPs), alone (single CRE) or [...] Read more.
In thin-layer chromatography coupled with surface-enhanced Raman spectroscopy (TLC-SERS), the coffee ring effect (CRE) describes the formation of a ring-shape spot (blank in the middle and darker on the edge) caused by the aggregation of silver nanoparticles (Ag NPs), alone (single CRE) or with the analytes (double CRE). In this work, the SCRE and DCRE were investigated in two anti-diabetic drugs, hydrophobic glibenclamide (GLB) and more hydrophilic metformin (MET). The SCRE occurred in GLB analysis, as opposed to the DCRE that occurred in MET. It was proven that for optimization of the TLC-SERS analytical procedure, it is necessary to distinguish the CRE patterns of analytes. Additionally, MET and GLB were analyzed with the developed TLC-SERS method and confirmed by another validated method using high-performance liquid chromatography. Four herbal products collected on the market were found to be adulterated with GLB or/and MET; among those, one product was adulterated with both MET and GLB, and two products were adulterated with GLB at a higher concentration than the usual GLB prescription dose. The TLC-SERS method provided a useful tool for the simultaneous detection of adulterated anti-diabetic herbal products, and the comparison of the SCRE and DCRE provided more evidence to predict CRE patterns in TLC-SERS. Full article
(This article belongs to the Special Issue The Role of Raman Spectroscopy in Analytical Sciences)
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22 pages, 4563 KiB  
Article
Quantitative Raman Analysis of Carotenoid Protein Complexes in Aqueous Solution
by Joy Udensi, Ekaterina Loskutova, James Loughman and Hugh J. Byrne
Molecules 2022, 27(15), 4724; https://doi.org/10.3390/molecules27154724 - 24 Jul 2022
Cited by 10 | Viewed by 2057
Abstract
Carotenoids are naturally abundant, fat-soluble pigmented compounds with dietary, antioxidant and vision protection advantages. The dietary carotenoids, Beta Carotene, Lutein, and Zeaxanthin, complexed with in bovine serum albumin (BSA) in aqueous solution, were explored using Raman spectroscopy to differentiate and quantify their spectral [...] Read more.
Carotenoids are naturally abundant, fat-soluble pigmented compounds with dietary, antioxidant and vision protection advantages. The dietary carotenoids, Beta Carotene, Lutein, and Zeaxanthin, complexed with in bovine serum albumin (BSA) in aqueous solution, were explored using Raman spectroscopy to differentiate and quantify their spectral signatures. UV visible absorption spectroscopy was employed to confirm the linearity of responses over the concentration range employed (0.05–1 mg/mL) and, of the 4 Raman source wavelengths (785 nm, 660 nm, 532 nm, 473 nm), 532 nm was chosen to provide the optimal response. After preprocessing to remove water and BSA contributions, and correct for self-absorption, a partial least squares model with R2 of 0.9995, resulted in an accuracy of the Root Mean Squared Error of Prediction for Beta Carotene of 0.0032 mg/mL and Limit of Detection 0.0106 mg/mL. Principal Components Analysis clearly differentiated solutions of the three carotenoids, based primarily on small shifts of the main peak at ~1520 cm−1. Least squares fitting analysis of the spectra of admixtures of the carotenoid:protein complexes showed reasonable correlation between norminal% and fitted%, yielding 100% contribution when fitted with individual carotenoid complexes and variable contributions with multiple ratios of admixtures. The results indicate the technique can potentially be used to quantify the carotenoid content of human serum and to identify their differential contributions for application in clinical analysis. Full article
(This article belongs to the Special Issue The Role of Raman Spectroscopy in Analytical Sciences)
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20 pages, 4002 KiB  
Article
A New Alternative Tool to Analyse Glycosylation in Monoclonal Antibodies Based on Drop-Coating Deposition Raman imaging: A Proof of Concept
by Sabrina Hamla, Pierre-Yves Sacré, Allison Derenne, Ben Cowper, Erik Goormaghtigh, Philippe Hubert and Eric Ziemons
Molecules 2022, 27(14), 4405; https://doi.org/10.3390/molecules27144405 - 09 Jul 2022
Viewed by 1607
Abstract
Glycosylation is considered a critical quality attribute of therapeutic proteins as it affects their stability, bioactivity, and safety. Hence, the development of analytical methods able to characterize the composition and structure of glycoproteins is crucial. Existing methods are time consuming, expensive, and require [...] Read more.
Glycosylation is considered a critical quality attribute of therapeutic proteins as it affects their stability, bioactivity, and safety. Hence, the development of analytical methods able to characterize the composition and structure of glycoproteins is crucial. Existing methods are time consuming, expensive, and require significant sample preparation, which can alter the robustness of the analyses. In this context, we developed a fast, direct, and simple drop-coating deposition Raman imaging (DCDR) method combined with multivariate curve resolution alternating least square (MCR-ALS) to analyze glycosylation in monoclonal antibodies (mAbs). A database of hyperspectral Raman imaging data of glycoproteins was built, and the glycoproteins were characterized by LC-FLR-MS as a reference method to determine the composition in glycans and monosaccharides. The DCDR method was used and allowed the separation of excipient and protein by forming a “coffee ring”. MCR-ALS analysis was performed to visualize the distribution of the compounds in the drop and to extract the pure spectral components. Further, the strategy of SVD-truncation was used to select the number of components to resolve by MCR-ALS. Raman spectra were processed by support vector regression (SVR). SVR models showed good predictive performance in terms of RMSECV, R2CV. Full article
(This article belongs to the Special Issue The Role of Raman Spectroscopy in Analytical Sciences)
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20 pages, 4751 KiB  
Article
Estimating the Analytical Performance of Raman Spectroscopy for Quantification of Active Ingredients in Human Stratum Corneum
by Hichem Kichou, Emilie Munnier, Yuri Dancik, Kamilia Kemel, Hugh J. Byrne, Ali Tfayli, Dominique Bertrand, Martin Soucé, Igor Chourpa and Franck Bonnier
Molecules 2022, 27(9), 2843; https://doi.org/10.3390/molecules27092843 - 29 Apr 2022
Cited by 9 | Viewed by 1910
Abstract
Confocal Raman microscopy (CRM) has become a versatile technique that can be applied routinely to monitor skin penetration of active molecules. In the present study, CRM coupled to multivariate analysis (namely PLSR—partial least squares regression) is used for the quantitative measurement of an [...] Read more.
Confocal Raman microscopy (CRM) has become a versatile technique that can be applied routinely to monitor skin penetration of active molecules. In the present study, CRM coupled to multivariate analysis (namely PLSR—partial least squares regression) is used for the quantitative measurement of an active ingredient (AI) applied to isolated (ex vivo) human stratum corneum (SC), using systematically varied doses of resorcinol, as model compound, and the performance is quantified according to key figures of merit defined by regulatory bodies (ICH, FDA, and EMA). A methodology is thus demonstrated to establish the limit of detection (LOD), precision, accuracy, sensitivity (SEN), and selectivity (SEL) of the technique, and the performance according to these key figures of merit is compared to that of similar established methodologies, based on studies available in literature. First, principal components analysis (PCA) was used to examine the variability within the spectral data set collected. Second, ratios calculated from the area under the curve (AUC) of characteristic resorcinol and proteins/lipids bands (1400–1500 cm−1) were used to perform linear regression analysis of the Raman spectra. Third, cross-validated PLSR analysis was applied to perform quantitative analysis in the fingerprint region. The AUC results show clearly that the intensities of Raman features in the spectra collected are linearly correlated to resorcinol concentrations in the SC (R2 = 0.999) despite a heterogeneity in the distribution of the active molecule in the samples. The Root Mean Square Error of Cross-Validation (RMSECV) (0.017 mg resorcinol/mg SC), The Root Mean Square of Prediction (RMSEP) (0.015 mg resorcinol/mg SC), and R2 (0.971) demonstrate the reliability of the linear regression constructed, enabling accurate quantification of resorcinol. Furthermore, the results have enabled the determination, for the first time, of numerical criteria to estimate analytical performances of CRM, including LOD, precision using bias corrected mean square error prediction (BCMSEP), sensitivity, and selectivity, for quantification of the performance of the analytical technique. This is one step further towards demonstrating that Raman spectroscopy complies with international guidelines and to establishing the technique as a reference and approved tool for permeation studies. Full article
(This article belongs to the Special Issue The Role of Raman Spectroscopy in Analytical Sciences)
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17 pages, 3602 KiB  
Article
Confocal Raman Spectroscopic Imaging for Evaluation of Distribution of Nano-Formulated Hydrophobic Active Cosmetic Ingredients in Hydrophilic Films
by Louise Van Gheluwe, Emilie Munnier, Hichem Kichou, Kamilia Kemel, Frédéric Mahut, Marylène Vayer, Christophe Sinturel, Hugh J. Byrne, Florent Yvergnaux, Igor Chourpa and Franck Bonnier
Molecules 2021, 26(24), 7440; https://doi.org/10.3390/molecules26247440 - 08 Dec 2021
Cited by 5 | Viewed by 2649
Abstract
Film-forming systems are highly relevant to the topical administration of active ingredients (AI) to the body. Enhanced contact with the skin can increase the efficacy of delivery and penetration during prolonged exposure. However, after the evaporation of volatile solvents to form a thin [...] Read more.
Film-forming systems are highly relevant to the topical administration of active ingredients (AI) to the body. Enhanced contact with the skin can increase the efficacy of delivery and penetration during prolonged exposure. However, after the evaporation of volatile solvents to form a thin film, the distribution of the ingredient should remain homogenous in order to ensure the effectiveness of the formula. This is especially critical for the use of hydrophobic molecules that have poor solubility in hydrophilic films. In order to address this concern, hydroxyphenethyl esters (PHE) of Punica granatum seed oil were prepared as a nanosuspension stabilised by poloxamers (NanoPHE). NanoPHE was then added to a formulation containing polyvinyl alcohol (PVA) as a film forming agent, Glycerol as a plasticiser and an antimicrobial agent, SepicideTM HB. Despite their reliability, reference methods such as high-performance liquid chromatography are increasingly challenged due to the need for consumables and solvents, which is contrary to current concerns about green industry in the cosmetics field. Moreover, such methods fail to provide spatially resolved chemical information. In order to investigate the distribution of ingredients in the dried film, Confocal Raman imaging (CRI) coupled to Non-negatively Constrained Least Squares (NCLS) analysis was used. The reconstructed heat maps from a range of films containing systematically varying PHE concentrations highlighted the changes in spectral contribution from each of the ingredients. First, using NCLS scores it was demonstrated that the distributions of PVA, Glycerol, SepicideTM HB and PHE were homogenous, with respective relative standard deviations (RSD) of 3.33%, 2.48%, 2.72% and 6.27%. Second, the respective relationships between ingredient concentrations in the films and their Raman responses, and the spectral abundance were established. Finally, a model for absolute quantification for PHE was be constructed using the percentage of spectral abundance. The prepared %w/w concentrations regressed against predicted %w/w concentrations, displaying high correlation (R2 = 0.995), while the Root Mean Squared Error (0.0869% w/w PHE) confirmed the precision of the analysis. The mean percent relative error of 3.75% indicates the accuracy to which the concentration in dried films could be determined, further supporting the suitability of CRI for analysis of composite solid film matrix. Ultimately, it was demonstrated that nanoformulation of hydrophobic PHE provides homogenous distribution in PVA based film-forming systems independent of the concentration of NanoPHE used in the formula. Full article
(This article belongs to the Special Issue The Role of Raman Spectroscopy in Analytical Sciences)
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