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Pharmaceutics
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Advances in Low-Frequency Raman Spectroscopy for Pharmaceutical Applications
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Advances in Low-Frequency Raman Spectroscopy for Pharmaceutical Applications

A special issue of Pharmaceutics (ISSN 1999-4923). This special issue belongs to the section "Pharmaceutical Technology, Manufacturing and Devices".

Deadline for manuscript submissions: closed (5 December 2023) | Viewed by 6780

Special Issue Editors

Dr. Sara J. Fraser-Miller

E-Mail Website
Guest Editor
The Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Chemistry, University of Otago, Dunedin 9016, New Zealand
Interests: spectroscopy; Raman and IR spectroscopy; pharmaceutical; diagnosis
Dr. Kārlis Bērziņš

E-Mail Website
Guest Editor
Department of Pharmacy, University of Copenhagen, 2100 Copenhagen, Denmark
Interests: Raman spectroscopy; thermal analysis chemometrics; powder X-ray diffraction; amorphous drug stabilization; physical chemistry and pharmaceuticals

Special Issue Information

Dear Colleagues,

Low-frequency Raman (LFR) is the detection of Raman spectra in the low-wavenumber spectral region (10 to 300 cm-1). This spectral region contains bands associated with inter-molecular vibrations, making it particularly sensitive to the solid-state form of pharmaceutical systems. The relatively strong signals typically obtained, along with the non-destructive nature of the technique, make it a promising candidate for assessing pharmaceutical systems, from drug development to manufacturing process monitoring and product verification.

For this Special Issue, we are seeking reviews and original articles that explore the use of low-frequency Raman spectroscopy in the pharmaceutical sciences. We welcome submissions regarding all aspects of this topic, including (but not limited to): 

  • Assessing composition and/or solid-state form;
  • Process monitoring;
  • Stability and dissolution assessment;
  • Formulation development and characterization;
  • Forensic applications;
  • Data analysis methods and considerations;
  • Characterizing low wavenumber vibrations (e.g., DFT calculations).

Dr. Sara J. Fraser-Miller
Dr. Kārlis Bērziņš
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. Pharmaceutics is an international peer-reviewed open access monthly 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 2900 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

  • low-frequency Raman spectroscopy
  • low wavenumber Raman spectroscopy
  • pharmaceutics
  • solid state analysis

Published Papers (5 papers)

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Research

12 pages, 3760 KiB  
Article
Pharmaceutical Evaluation of Levofloxacin Orally Disintegrating Tablet Formulation Using Low Frequency Raman Spectroscopy
by Yoshihisa Yamamoto, Mizuho Kajita, Yutaro Hirose, Naoki Shimada, Toshiro Fukami and Tatsuo Koide
Pharmaceutics 2023, 15(8), 2041; https://doi.org/10.3390/pharmaceutics15082041 - 29 Jul 2023
Viewed by 1034
Abstract
We evaluated the pharmaceutical properties of levofloxacin (LV) in the form of an orally disintegrating tablet (LVODT) to find a new usefulness of low frequency (LF) Raman spectroscopy. LVODT contained dispersed granules with diameters in the order of several hundred [...] Read more.
We evaluated the pharmaceutical properties of levofloxacin (LV) in the form of an orally disintegrating tablet (LVODT) to find a new usefulness of low frequency (LF) Raman spectroscopy. LVODT contained dispersed granules with diameters in the order of several hundred micrometers, which were composed of the active pharmaceutical ingredient (API), as confirmed by infrared (IR) microspectroscopy. On the contrary, the API and inactive pharmaceutical ingredients (non-APIs) were homogeneously distributed in LV tablet (LVT) formulations. Microscopic IR spectroscopy and thermal analyses showed that LVODT and LVT contained the API in different crystalline forms or environment around the API each other. Furthermore, powder X-ray diffraction showed that LVT contained a hemihydrate of the API, while LVODT showed a partial transition to the monohydrate form. This result was confirmed by microscopic LF Raman spectroscopy. Moreover, this method confirmed the presence of thin layers coating the outer edges of the granules that contained the API. Spectra obtained from these thin layers indicated the presence of titanium dioxide, suggesting that the layers coexisted with a polymer that masks the bitterness of API. The microscopic LF Raman spectroscopy results in this study indicated new applications of this method in pharmaceutical science. Full article
(This article belongs to the Special Issue Advances in Low-Frequency Raman Spectroscopy for Pharmaceutical Applications)
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13 pages, 3166 KiB  
Article
In Situ Monitoring of Drug Precipitation from Digesting Lipid Formulations Using Low-Frequency Raman Scattering Spectroscopy
by Malinda Salim, Sara J. Fraser-Miller, Kārlis Bērziņš, Joshua J. Sutton, Keith C. Gordon and Ben J. Boyd
Pharmaceutics 2023, 15(7), 1968; https://doi.org/10.3390/pharmaceutics15071968 - 17 Jul 2023
Cited by 1 | Viewed by 1262
Abstract
Low-frequency Raman spectroscopy (LFRS) is a valuable tool to detect the solid state of amorphous and crystalline drugs in solid dosage forms and the transformation of drugs between different polymorphic forms. It has also been applied to track the solubilisation of solid drugs [...] Read more.
Low-frequency Raman spectroscopy (LFRS) is a valuable tool to detect the solid state of amorphous and crystalline drugs in solid dosage forms and the transformation of drugs between different polymorphic forms. It has also been applied to track the solubilisation of solid drugs as suspensions in milk and infant formula during in vitro digestion. This study reports the use of LFRS as an approach to probe drug precipitation from a lipid-based drug delivery system (medium-chain self-nanoemulsifying drug delivery system, MC-SNEDDS) during in vitro digestion. Upon lipolysis of the digestible components in MC-SNEDDS containing fenofibrate as a model drug, sharp phonon peaks appeared at the low-frequency Raman spectral region (<200 cm−1), indicating the precipitation of fenofibrate in a crystalline form from the formulation. Two multivariate data analysis approaches (principal component analysis and partial least squares discriminant analysis) and one univariate analysis approach (band ratios) were explored to track these spectral changes over time. The low-frequency Raman data produces results in good agreement with in situ small angle X-ray scattering (SAXS) measurements with all data analysis approaches used, whereas the mid-frequency Raman requires the use of PLS-DA to gain similar results. This suggests that LFRS can be used as a complementary, and potentially more accessible, technique to SAXS to determine the kinetics of drug precipitation from lipid-based formulations. Full article
(This article belongs to the Special Issue Advances in Low-Frequency Raman Spectroscopy for Pharmaceutical Applications)
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20 pages, 11731 KiB  
Article
Low-Frequency Raman Spectroscopy: An Exceptional Tool for Exploring Metastability Driven States Induced by Dehydration
by Yannick Guinet, Laurent Paccou and Alain Hédoux
Pharmaceutics 2023, 15(7), 1955; https://doi.org/10.3390/pharmaceutics15071955 - 15 Jul 2023
Cited by 1 | Viewed by 1027
Abstract
The use of low-frequency Raman spectroscopy (LFRS; ω < 150 cm−1) is booming in the pharmaceutical industry. Specific processing of spectra is required to use the wealth of information contained in this spectral region. Spectra processing and the use of LFRS [...] Read more.
The use of low-frequency Raman spectroscopy (LFRS; ω < 150 cm−1) is booming in the pharmaceutical industry. Specific processing of spectra is required to use the wealth of information contained in this spectral region. Spectra processing and the use of LFRS for analyzing phase transformations in molecular materials are detailed herein from investigations on the devitrification of ibuprofen. LFRS was used to analyze the dehydration mechanism of two hydrates (theophylline and caffeine) of the xanthine family. Two mechanisms of solid-state transformation in theophylline were determined depending on the relative humidity (RH) and temperature. At room temperature and 1% RH, dehydration is driven by the diffusion mechanism, while under high RH (>30%), kinetic laws are typical of nucleation and growth mechanism. By increasing the RH, various metastability driven crystalline forms were obtained mimicking successive intermediate states between hydrate form and anhydrous form achieved under high RH. In contrast, the dehydration kinetics of caffeine hydrate under various RH levels can be described by only one master curve corresponding to a nucleation mechanism. Various metastability driven states were achieved depending on the RH, which can be described as intermediate between forms I and II of anhydrous caffeine. Full article
(This article belongs to the Special Issue Advances in Low-Frequency Raman Spectroscopy for Pharmaceutical Applications)
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15 pages, 2141 KiB  
Article
Low-Frequency Raman Spectroscopy of Pure and Cocrystallized Mycophenolic Acid
by Catherine S. Wallace, Margaret P. Davis and Timothy M. Korter
Pharmaceutics 2023, 15(7), 1924; https://doi.org/10.3390/pharmaceutics15071924 - 11 Jul 2023
Viewed by 956
Abstract
The aqueous solubility of solid-state pharmaceuticals can often be enhanced by cocrystallization with a coformer to create a binary cocrystal with preferred physical properties. Greater understanding of the internal and external forces that dictate molecular structure and intermolecular packing arrangements enables more efficient [...] Read more.
The aqueous solubility of solid-state pharmaceuticals can often be enhanced by cocrystallization with a coformer to create a binary cocrystal with preferred physical properties. Greater understanding of the internal and external forces that dictate molecular structure and intermolecular packing arrangements enables more efficient design of new cocrystals. Low-frequency (sub-200 cm−1) Raman spectroscopy experiments and solid-state density functional theory simulations have been utilized together to investigate the crystal lattice vibrations of mycophenolic acid, an immunosuppressive drug, in its pure form and as a cocrystal with 2,2′-dipyridylamine. The lattice vibrations primarily consist of large-amplitude translations and rotations of the crystal components, thereby providing insights into the critical intermolecular forces governing cohesion of the molecular solids. The simulations reveal that despite mycophenolic acid having a significantly unfavorable conformation in the cocrystal as compared to the pure solid, the cocrystal exhibits greater thermodynamic stability over a wide temperature range. The energetic penalty due to the conformational strain is more than compensated for by the strong intermolecular forces between the drug and 2,2′-dipyridylamine. Quantifying the balance of internal and external energy factors in cocrystal formation indicates a path forward in the development of future mycophenolic acid cocrystals. Full article
(This article belongs to the Special Issue Advances in Low-Frequency Raman Spectroscopy for Pharmaceutical Applications)
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15 pages, 4779 KiB  
Article
Exploring the Solid-State Landscape of Carbamazepine during Dehydration: A Low Frequency Raman Spectroscopy Perspective
by Peter III J. G. Remoto, Kārlis Bērziņš, Sara J. Fraser-Miller, Timothy M. Korter, Thomas Rades, Jukka Rantanen and Keith C. Gordon
Pharmaceutics 2023, 15(5), 1526; https://doi.org/10.3390/pharmaceutics15051526 - 18 May 2023
Cited by 2 | Viewed by 1648
Abstract
The solid-state landscape of carbamazepine during its dehydration was explored using Raman spectroscopy in the low- (−300 to −15, 15 to 300) and mid- (300 to 1800 cm−1) frequency spectral regions. Carbamazepine dihydrate and forms I, III, and IV were also [...] Read more.
The solid-state landscape of carbamazepine during its dehydration was explored using Raman spectroscopy in the low- (−300 to −15, 15 to 300) and mid- (300 to 1800 cm−1) frequency spectral regions. Carbamazepine dihydrate and forms I, III, and IV were also characterized using density functional theory with periodic boundary conditions and showed good agreement with experimental Raman spectra with mean average deviations less than 10 cm−1. The dehydration of carbamazepine dihydrate was examined under different temperatures (40, 45, 50, 55, and 60 °C). Principal component analysis and multivariate curve resolution were used to explore the transformation pathways of different solid-state forms during the dehydration of carbamazepine dihydrate. The low-frequency Raman domain was able to detect the rapid growth and subsequent decline of carbamazepine form IV, which was not as effectively observed by mid-frequency Raman spectroscopy. These results showcased the potential benefits of low-frequency Raman spectroscopy for pharmaceutical process monitoring and control. Full article
(This article belongs to the Special Issue Advances in Low-Frequency Raman Spectroscopy for Pharmaceutical Applications)
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