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The serpentine mineral lizardite displays strong Raman anisotropy in the OH-stretching region, resulting in significant wavenumber shifts (up to ca. 14.5 cm−1) that depend on the orientation of the impinging excitation laser relative to the crystallographic axes. We quantified the relationship between crystallographic orientation and Raman wavenumber using well-characterised samples of Monte Fico lizardite by applying Raman spectroscopy and electron backscatter diffraction (EBSD) mapping on thin sections of polycrystalline samples and grain mounts of selected single crystals, as well as by a spindle stage Raman study of an oriented cylinder drilled from a single crystal. We demonstrate that the main band in the OH-stretching region undergoes a systematic shift that depends on the inclination of the c-axis of the lizardite crystal. The data are used to derive an empirical relationship between the position of this main band and the c-axis inclination of a measured lizardite crystal: y=14.5cos 4 (0.013x+0.02)+(3670±1), where y is the inclination of the c-axis with respect to the normal vector (in degrees), and x is the main band position (wavenumber in cm −1) in the OH-stretching region. This new method provides a simple and cost-effective technique for measuring and quantifying the crystallographic orientation of lizardite-bearing serpentinite fault rocks, which can be difficult to achieve using EBSD alone. In addition to the samples used to determine the above empirical relationship, we demonstrate the applicability of the technique by mapping the orientations of lizardite in a more complex sample of deformed serpentinite from Elba Island, Italy.

Compression-induced destabilization was investigated in various celecoxib amorphous solid dispersions containing hydroxypropyl methylcellulose (HPMC), poly(vinylpyrrolidone)/vinyl acetate copolymer (PVP/VA), or poly(vinylpyrrolidone) (PVP) at a concentration range of 1-10% w/w. Pharmaceutically relevant (125 MPa pressure with a minimal dwell time) and extreme (500 MPa pressure with a 60 s dwell time) compression conditions were applied to these systems, and the changes in their physical stability were monitored retrospectively (i.e., in the supercooled state) using dynamic differential scanning calorimetry (DSC) and low-frequency Raman (LFR) measurements over a broad temperature range (-90 to 200 and -150 to 140 °C, respectively). Both techniques revealed similar changes in the crystallization behavior between samples, where the application of a higher compression force of 500 MPa resulted in a more pronounced destabilization effect that was progressively mitigated with increasing polymer content. However, other aspects such as more favorable intermolecular interactions did not appear to have any effect on reducing this undesirable effect. Additionally, for the first time, LFR spectroscopy was used as a viable technique to determine the secondary or local glass-transition temperature, Tg,β, a major indicator of the physical stability of neat amorphous pharmaceutical systems.

The natural black–brown pigment eumelanin protects humans from high-energy UV photons by absorbing and rapidly dissipating their energy before proteins and DNA are damaged. The extremely weak fluorescence of eumelanin points toward nonradiative relaxation on the timescale of picoseconds or shorter. However, the extreme chemical and physical complexity of eumelanin masks its photoprotection mechanism. We sought to determine the electronic and structural relaxation pathways in eumelanin using three complementary ultrafast optical spectroscopy methods: fluorescence, transient absorption, and stimulated Raman spectroscopies. We show that photoexcitation of chromophores across the UV–visible spectrum rapidly generates a distribution of visible excitation energies via ultrafast internal conversion among neighboring coupled chromophores, and then all these excitations relax on a timescale of ∼4 ps without transferring their energy to other chromophores. Moreover, these picosecond dynamics are shared by the monomeric building block, 5,6-dihydroxyindole-2-carboxylic acid. Through a series of solvent and pH-dependent measurements complemented by quantum chemical modeling, we show that these ultrafast dynamics are consistent with the partial excited-state proton transfer from the catechol hydroxy groups to the solvent. The use of this multispectroscopic approach allows the minimal functional unit in eumelanin and the role of exciton coupling and excited-state proton transfer to be determined, and ultimately reveals the mechanism of photoprotection in eumelanin. This knowledge has potential for use in the design of new soft optical components and organic sunscreens.

This work explores the potential use of spatially offset low-frequency anti-Stokes Raman spectroscopy (SOLFARS) to detect subsurface composition below an emissive surface. A range of bilayer tablets were used to evaluate this approach. Bilayer tablets differed in both the underlying layer composition (active pharmaceutical ingredient to excipient ratio, celecoxib: α-lactose monohydrate) and the upper layer thickness of the fluorescent coating (polyvinylpyrrolidone mixture with sunset yellow FCF dye). Two low- (300 cm

The geometric and spectroscopic properties of four cationic

A new combinatory Raman subtechnique of low-frequency and micro-spatially offset Raman spectroscopy (denoted micro-SOLFRS) is demonstrated via analysis of pharmaceutical solid dosage forms. A variety of different (multilayer/multicomponent) model systems comprising celecoxib, α-lactose (the anhydrous and monohydrate form), and polyvinylpyrrolidone (PVP) were probed to test the potency of this newly developed technique to, for example, provide qualitative and quantitative information on surface and subsurface layer characteristics, including their thicknesses as well as enable monitoring of surface-driven solid-state form transformations. A simultaneous collection of low- and, the more commonly used, mid-frequency data enabled a direct comparison between these spectral regions, where the low-frequency domain (hence, micro-SOLFRS) proved superior for every respective analysis carried out herein.

The optical properties of two Re(CO)3(bpy)Cl complexes in which the bpy is substituted with two donor (triphenylamine, TPA, ReTPA2) as well as both donor (TPA) and acceptor (benzothiadiazole, BTD, ReTPA-BTD) groups are presented. For ReTPA2 the absorption spectra show intense intraligand charge-transfer (ILCT) bands at 460 nm with small solvatochromic behavior; for ReTPA-BTD the ILCT transitions are weaker. These transitions are assigned as TPA → bpy transitions as supported by resonance Raman data and TDDFT calculations. The excited-state spectroscopy shows the presence of two emissive states for both complexes. The intensity of these emission signals is modulated by solvent. Time-resolved infrared spectroscopy definitively assigns the excited states present in CH2Cl2 to be MLCT in nature, and in MeCN the excited states are ILCT in nature. DFT calculations indicated this switching with solvent is governed by access to states controlled by spin-orbit coupling, which is sufficiently different in the two solvents, allowing to select out each of the charge-transfer states.

Plastics are ubiquitous throughout global marine ecosystems. To date, there has been limited research on the prevalence of microplastic ingestion by commercially important marine fish in the southern hemisphere, particularly in the South Pacific. Therefore, this research aimed to quantify ingested microplastics from ten commercially important fish species from southern New Zealand using microscopy and Raman spectroscopy. Overall, we found evidence of microplastic ingestion in 75 % of fish, with an average of 2.5 individual particles per fish. Microplastic fibers were the most commonly ingested. The most common colored microplastics ingested were blue, black and red, and 99.68 % of plastics identified were smaller than 5 mm. Raman spectroscopy of plastics recovered from nine fish species found polyethylene and polypropylene to be the most common plastic polymers ingested. Further research is necessary to ascertain the human ecological and health risks involved when exposed to microplastics through eating plastic contaminated fish.

Co-amorphization of a single drug with amino acid is a technique to improve aerosolization of inhalable spray-dried formulation for inhalation therapy. However, the incorporation of a second drug molecule into drug-amino acid co-amorphous particles to prepare combination formulations has not been explored. Here, we prepared combination powders using two model drugs, ceftazidime and roflumilast, which when concurrently used can potentially improve therapeutic outcome in non-cystic fibrosis bronchiectasis by counteracting both infection and inflammation. The study was performed using a two-step approach. The first step involved the identification of an amino acid and its concentration (%

High dose powder inhalation is evolving as an important approach to to treat lung infections. It is important to its identify applications, consider the factors affecting high dose powder delivery, and assess the effect of high dose drugs in patients.Both current and pipeline high dose inhalers and their applications have been summarized. Challenges and opportunities to high dose delivery have been highlighted after reviewing formulation techniques in the context of factors affecting aerosolization, devices, and patient factors.High dose inhaled delivery of antimicrobials is an innovative way to increase treatment efficacy of respiratory infections, tackle drug resistance, and the scarcity of new antimicrobials. The high dose inhaled technology also has potential for systemic action; however, innovations in formulation strategies and devices are required to realize its full potential. Advances in formulation strategies include the use of excipients or the engineering of particles to decrease the cohesive property of microparticles and their packing density. Similarly, selection of a synergistic drug instead of an excipient can be considered to increase aerosolization and stability. Device development focused on improving dispersion and loading capacity is also important, and modification of existing devices for high dose delivery can also be considered.

Slurry studies are useful for exhaustive polymorph and solid-state stability screening of drug compounds. Raman spectroscopy is convenient for monitoring crystallization in such slurries, as the measurements can be performed

Slurry studies are useful for exhaustive polymorph and solid-state stability screening of drug compounds. Raman spectroscopy is convenient for monitoring crystallization in such slurries, as the measurements can be performed in situ even in aqueous environments. While the mid-frequency region (400-4000 cm(-1)) is dominated by intramolecular vibrations and has traditionally been used for such studies, the low-frequency spectral region (

Spectroscopic methods are a promising approach for providing a point-of-care diagnostic method for gastrointestinal mucosa associated illnesses. Such a tool is desired to aid immediate decision mak...

Krill oil contains eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), long chain omega-3 polyunsaturated fatty acids with essential roles in human health, and astaxanthin, a naturally occu...

Detection of the solid-state forms of pharmaceutical compounds is important from the drug performance point of view. Low-frequency Raman (LFR) spectroscopy has been demonstrated to be very sensitive in detecting the different solid-state forms of pharmaceutically relevant compounds. The potential of LFR spectroscopy to probe the in situ isothermal dehydration was studied using piroxicam monohydrate (PXM) and theophylline monohydrate (TPMH) as the model drugs. The dehydration of PXM and TPMH at four different temperatures (95, 100, 105, and 110 °C and 50, 60, 70, and 80 °C, respectively) was monitored in both the low- (20-300 cm

The successful covalent attachment, via copper(I)-catalyzed azide alkyne cycloaddition (CuAAC), of alkyne-functionalized nickel(II) and copper(II) macrocyclic complexes onto azide (N3)-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) films on ITO-coated glass electrodes is reported. To investigate the surface attachment of the selected metal complexes, which are analogues of the cobalt-based complex previously reported to be a molecular catalyst for hydrogen evolution, first, three different PEDOT films were formed by electropolymerization of pure PEDOT or pure N3-PEDOT, and last, 1:2N3-PEDOT:PEDOT were formed by co-polymerizing a 1:4 mixture of N3-EDOT:EDOT monomers. The successful surface immobilization of the complexes on the latter two azide-functionalized films, by CuAAC, was confirmed by X-ray photoelectron spectroscopy (XPS) and electrochemistry as well as by UV-vis-NIR and resonance Raman spectroelectrochemistry. The ratio between the N3 groups, and hence, the number of surface-attached metal complexes after CuAAC functionalization, in pristine N3-PEDOT versus 1:2N3-PEDOT:PEDOT is expected to be 3:1 and seen to be 2.86:1 with a calculated surface coverage of 3.28 ± 1.04 and 1.15 ± 0.09 nmol/cm2, respectively. The conversion, to the metal complex attached films, was lower for the N3-PEDOT films (Ni 74%, Cu 76%) than for the copolymer 1:2N3-PEDOT:PEDOT films (Ni 83%, Cu 91%) due to the former being more sterically congested. The Raman and UV-vis-NIR results were simulated using density functional theory (DFT) and time-dependent DFT (TD-DFT), respectively, and showed good agreement with the experimental data. Importantly, the spectroelectrochemical behavior of both anchored metal complexes is analogous to that of the free metal complexes in solution. This proves that PEDOT films are promising conducting scaffolds for the covalent immobilization of metal complexes, as the existing electrochromic features of the complexes are preserved on immobilization, which is important for applications in electrocatalytic proton and carbon dioxide reduction, optoelectronics, and sensing.

The photophysical properties of a series of heteroleptic Ru(II) complexes of the form [Ru(phen)2(phen-5,6-R2)]2+, where phen = 1,10-phenanthroline and R = phenyl (Ph), p-tert-butylbenzene (p-Ph-tBu), p-methoxybenzene (p-Ph-OMe), and 2-naphthalene (2-naph), have been measured. Variation of the R group does not greatly perturb the electronic properties of the ground state, which were explored with electronic absorption and resonance Raman spectroscopy and are akin to those of the archetypal parent complex [Ru(phen)3]2+. All complexes were shown to possess emissive 3MLCT states, characterized through transient absorption and emission spectroscopy. However, an additional, long-lived excited state was observed in the Ru(II) naphthalene complex. The naphthalene substituents facilitate population of a 40 μs dark state which decays independently to that of the emissive 3MLCT state. This state was characterized as 3LC in nature, delocalized over the naphthalene substituted ligand.

Five pharmaceutically relevant compounds with increasing molecular complexity, benzoic acid, diphenylacetic acid, l-tyrosine, celecoxib (form III), and carvedilol (form II), were investigated using...

Many customary Māori textiles are produced from harakeke fibres (muka) which are extracted from New Zealand flax (Phormium tenax) and some are dyed with paru (black) iron-tannate dyes. These tannate-dyed textiles degrade via iron catalysed oxidation and acid catalysed hydrolysis. To mitigate this degradation, conservators can potentially use various types of natural and synthetic consolidants; however, there is a lack of systematic study of the interaction between muka and consolidants. As part of a larger research project investigating the efficacy of six consolidants for treatment of deteriorated black-dyed muka in Māori textiles, the penetration of different consolidants applied to muka was investigated. By using Raman microscopy combined with chemometrics, this study was able to aid in selection, and concentration of, consolidants for use in the larger project. Six different consolidants; sodium alginate, zinc alginate, Paraloid B-72™ (ethyl-methyl methacrylate), TRI-Funori™ (seaweed extract, polysaccharide), Klucel G™ (hydroxypropyl cellulose), and Methocel A4C™ (methylcellulose) were applied at three concentrations (0.5, 1.0, and 2.0% w/v) to muka. The consolidated samples were sectioned and analysed using Raman microscopy mapping with a 532 nm incident laser. Relative intensity levels of the signals from the fibres and the consolidants were used to generate maps of the chemical composition across the fibre. Univariate analysis (with unique band integrals) and multivariate analysis (true component analysis) of the chemical images was able to distinguish the penetration pattern of consolidants, Paraloid B-72™, TRI-Funori™, and Klucel G™ into the fibres. The analysis of Methocel A4C™ was not possible because the spectral characteristics were too similar between the two. Sodium and zinc alginate consolidated samples tended to burn and no useful data could be collected. The consolidants accumulated in the intercellular spaces/middle lamella of the fibre's morphological structure and did not appear to penetrate into the fibre cell walls. The results from the study demonstrated the usefulness of Raman microscopy for understanding the properties and behaviour of consolidants applied to important cultural materials.

Lake snow, caused by the freshwater centric diatom Lindavia intermedia, has become problematic in several large, oligotrophic New Zealand lakes over the past decade. Macroaggregates produced by L. intermedia foul fishing lines, intake screens, and water filters, and have a negative impact on recreational values. It was confirmed that the fibers constituting lake snow are composed of chitin, two chitin synthase genes (chs1 and 2) from L. intermedia were characterized, new qPCR-based tools to quantify the abundance of the species and measure expression of chs2 relative to the reference gene act1 (the product of which has cytoskeletal functions) were developed. The strong heterogeneity and mucilaginous nature of lake snow samples create particular difficulties for calibrations of gene or transcript copy numbers with cell densities and obtaining high yields of mRNA. However, data collected from four lakes during November 2018 and February and May 2019 show that abundance of L. intermedia is always high when lake snow is also abundant, but that a full range of L. intermedia abundance can occur when lake snow is absent, suggesting that chitin production is not obligate in L. intermedia. This result is consistent with the available data for chs2 expression, which suggest higher transcription when lake snow is abundant. Lake snow production by L. intermedia therefore requires an as yet undetermined stimulus independent of cell abundance.

A series of β-ferrocene-modified zinc porphyrins, with various electron-withdrawing units appended to the ferrocene, were synthesized, and their electronic properties were investigated. The ferrocene was able to be modified with the substituents, with its oxidation potential increased by up to 0.3 V, without significantly perturbing the porphyrin core. A small red-shift of the strongest absorption band (B band) occurred upon the addition of the electron-withdrawing substituents (270 cm-1), occurring alongside a broadening of the band. The singlet state is unaffected by the ferrocene substitution; however, the triplet state lifetimes are decreased by 10.4-10.6 μs from that of the unsubstituted ferrocene porphyrin (18.1 μs). Computational studies showed that the changes in the optical properties are due to a loss of degeneracy of the porphyrin lowest unoccupied molecular orbitals; this is supported by resonance Raman spectroscopy studies, which show different enhancement patterns when probing the high- and low-energy edges of the B band.

The effect of electronic coupling on electron transfer (ET) rates has been considered minor and often ignored compared to the effect of driving force (ΔG°) between similarly structured donor and ac...

Techniques enabling in situ monitoring of drug solubilization and changes in the solid-state of the drug during the digestion of milk and milk-based formulations are valuable for predicting the effectiveness of such formulations in improving the oral bioavailability of poorly water-soluble drugs. We have recently reported the use of low-frequency Raman scattering spectroscopy (region of analysis

Pseudomonas aeruginosa infection is common in cystic fibrosis as well as non-cystic fibrosis bronchiectasis. The pathogen presents challenges for treatment due to its adaptive antibiotic-resistance, mainly pertaining to its biofilm-forming ability, as well as limitations associated with conventional drug delivery in achieving desired therapeutic concentration in the infection site. Hence, therapeutic approach has shifted towards the inhalation of antibiotics. Ceftazidime is a potent antibiotic against the pathogen; however, it is currently only available as a parenteral formulation. Here, spray dryer was employed to generate inhalable high dose ceftazidime microparticles. In addition, the use of amino acids (valine, leucine, methionine, phenylalanine, and tryptophan) to improve aerosolization as well as chemical stability of amorphous ceftazidime was explored. The particles were characterized using X-ray diffraction, infrared (IR) spectroscopy, calorimetry, electron microscopy, particle size analyzer, and next generation impactor. The chemical stability at 25 °C/15% was assessed using chromatography. All co-spray dried formulations were confirmed as monophasic amorphous systems using calorimetry. In addition, principal component analysis of the IR spectra suggested potential interaction between tryptophan and ceftazidime in the co-amorphous matrix. Inclusion of amino acids improved aerosolization and chemical stability in all cases. Increase in surface asperity was clear with the use of amino acids which likely contributed to the improved aerosol performance, and potential interaction between amino acids and ceftazidime was plausibly the reason for improved chemical stability. Leucine offered the best aerosolization enhancement with a fine particle fraction of 78% and tryptophan showed stabilizing superiority by reducing chemical degradation by 51% over 10 weeks in 1:1 M ratio. The protection against ceftazidime degradation varied with the nature of amino acids. Additionally, there was a linear relationship between degradation protection and molar mass of amino acids or percentage weight of amino acids in the formulations. None of the amino acids were successful in completely inhibiting degradation of ceftazidime in amorphous spray-dried powder to prepare a commercially viable product with desired shelf-life. All the amino acids and ceftazidime were non-toxic to A549 alveolar cell line.

Refereed/Peer-reviewed The influence of amino acids, other than leucine, in improving aerosolization of inhalable powders has not been widely explored. This detailed study focused on the use of methionine, another promising endogenous amino acid, in high dose spray-dried co-amorphous powders by investigating the influence of methionine proportion (0 – 20% w/w), and feed concentration (0.2 – 0.8% w/v) on aerosolization of kanamycin, a model drug, using a design of experiment approach. Low frequency Raman spectroscopy was used to assess the stability of the powders stored at 25 °C/53% relative humidity over 28 days. An increase in concentration of methionine was associated with an increase in fine particle fraction (FPF), with the highest FPF of 84% being achieved at 20% w/w and 0.2% w/v feed concentration. With an increase in feed concentration, both yield and particle size increased for all formulations; the FPF did not change except for kanamycin only formulation in which it decreased. During storage at high humidity, similar aerosolization stabilities were offered by different proportions of methionine although methionine crystallized out in all formulations. Furthermore, the crystallization was accompanied by surface enrichment of methionine on the particles. This study suggests that there is a direct relationship between methionine content and aerosolization for kanamycin-methionine amorphous matrices but feed concentration has little effect. In addition, methionine proportion has no effect on physical stability of such matrices at high humidity.

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are commercially important omega-3 fatty acids found in fish oils. Here we demonstrate that a handheld Raman spectrometer can be used to quantitate these compounds in intact fish oil capsules, avoiding oxidizing risk. Partial least squares regression models were prepared by relating Raman spectral variance to EPA and DHA concentrations determined using gas chromatography–mass spectrometry (GC-MS) analysis of fatty acid methyl esters in 15 commercial samples containing 145–473 mg g−1 EPA and 101–260 mg·g−1 DHA. Handheld Fourier transform (FT)-Raman models had root mean square errors of cross-validation of 38 mg g−1, 24 mg g−1, and 32 mg·g−1 for EPA, DHA, and EPA+DHA, respectively. Models generated from a benchtop FT-Raman spectrometer had corresponding errors of 32 mg·g−1, 22 mg·g−1, and 26 mg·g−1. By comparison, average standard deviations from triplicate GC-MS analyses were 11 mg·g−1 for EPA and 9 mg·g−1 for DHA.