Curve Resolution Analysis Research Articles

Photostability and ex-vivo permeation studies on diclofenac in topical niosomal formulations

Photostability studies were performed on topical formulations containing diclofenac (DC). Niosomal gels were designed as photostabilization systems and ascorbic acid was also added to the new topical formulations because of its antioxidant property. Photodegradation tests were applied on commercial formulations containing DC and novel prepared gels, according to the ICH rules. The experiments were monitored by spectrophotometry and the data processed by multivariate curve resolution analysis to estimate the spectra and concentration profiles of evolved components. Characterization of niosomes was evaluated by size and distribution measurement, morphological analysis and encapsulation efficiency. Permeation experiments were performed across rabbit ear skin up to 24h. Photodegradation rate of DC was found very fast in commercial formulation, with a residual content of 90% after only 4.38min under a radiant exposure of 450W/m2. Photostability resulted increased significantly when the drug was entrapped in niosomal systems. The best results were obtained by reaching a 10% degradation after 50.00min of light exposure after incorporation of DC in niosomes in presence of 5% ascorbic acid. Moreover, niosomal gel also influenced the permeation capability of DC by enhancing the transdermal delivery of the drug. The cumulative dose permeated of DC from niosomal gel was about three times that obtained with the commercial gel.

Statistically rigorous analysis of imaging SIMS data in the presence of detector saturation

We present a new strategy for analyzing imaging time‐of‐flight SIMS data sets affected by detector saturation. Rather than attempt to correct the measured data to remove saturation, we incorporate the detector behavior into the statistical basis of the analysis. This is performed within the framework of maximum a posteriori reconstruction. The proposed approach has several advantages over previous techniques. No approximations are involved other than the assumed model of the detector. The method performs well even when applied to highly saturated and/or single‐scan data sets. It is statistically rigorous, correctly treating the underlying statistical distribution of the data. It is also compatible with Bayesian methods for incorporating prior knowledge about sample properties. An efficient iterative scheme for solving the proposed equations is presented for the case of the bilinear model commonly used in analyses of SIMS data. The correctness of the approach and its efficacy are demonstrated on synthetic data sets. The method is found to perform better than a widely‐used data‐correction method used in combination with alternating‐least‐squares Multivariate Curve Resolution analysis. Copyright © 2015 John Wiley & Sons, Ltd.

Anisotropy resolved multidimensional emission spectroscopy (ARMES): A new tool for protein analysis

Structural analysis of proteins using the emission of intrinsic fluorophores is complicated by spectral overlap. Anisotropy resolved multidimensional emission spectroscopy (ARMES) overcame the overlap problem by the use of anisotropy, with chemometric analysis, to better resolve emission from different fluorophores. Total synchronous fluorescence scan (TSFS) provided information about all the fluorophores that contributed to emission while anisotropy provided information about the environment of each fluorophore. Here the utility of ARMES was demonstrated via study of the chemical and thermal denaturation of human serum albumin (HSA).Multivariate curve resolution (MCR) analysis of the constituent polarized emission ARMES data resolved contributions from four emitters: fluorescence from tryptophan (Trp), solvent exposed tyrosine (Tyr), Tyr in a hydrophobic environment, and room temperature phosphorescence (RTP) from Trp. The MCR scores, anisotropy, and literature validated these assignments and showed all the expected transitions during HSA unfolding. This new methodology for comprehensive intrinsic fluorescence analysis of proteins is applicable to any protein containing multiple fluorophores.

Triplet state formation in photovoltaic blends of DPP-type copolymers and PC71 BM.

The exciton dynamics in pristine films of two structurally related low-bandgap diketopyrrolopyrrole (DPP)-based donor-acceptor copolymers and the photophysical processes in bulk heterojunction solar cells using DPP copolymer:PC71 BM blends are investigated by broadband transient absorption (TA) pump-probe experiments covering the vis-near-infrared spectral and fs-μs dynamic range. The experiments reveal surprisingly short exciton lifetimes in the pristine poly-mer films in conjunction with fast triplet state formation. An in-depth analysis of the TA data by multivariate curve resolution analysis shows that in blends with fullerene as acceptor ultrafast exciton dissociation creates charge carriers, which then rapidly recombine on the sub-ns timescale. Furthermore, at the carrier densities created by pulsed laser excitation the charge carrier recombination leads to a substantial population of the polymer triplet state. In fact, virtually quantitative formation of triplet states is observed on the sub-ns timescale. However, the quantitative triplet formation on the sub-ns timescale is not in line with the power conversion efficiencies of devices indicating that triplet state formation is an intensity-dependent process in these blends and is reduced under solar illumination conditions, as free charge carriers can be extracted from the photoactive layer in devices.

Label-free in vivo imaging of peripheral nerve by multispectral photoacoustic tomography.

Unintentional surgical damage to nerves is mainly due to poor visualization of nerve tissue relative to adjacent structures. Multispectral photoacoustic tomography can provide chemical information with specificity and ultrasonic spatial resolution with centimeter imaging depth, making it a potential tool for noninvasive neural imaging. To implement this label-free imaging approach, a multispectral photoacoustic tomography platform was built. Imaging depth and spatial resolution were characterized. In vivo imaging of the femoral nerve that is 2 mm deep in a nude mouse was performed. Through multivariate curve resolution analysis, the femoral nerve was discriminated from the femoral artery and chemical maps of their spatial distributions were generated.

Microsecond Scale Vibrational Spectroscopic Imaging by Multiplex Stimulated Raman Scattering Microscopy.

Real-time vibrational spectroscopic imaging is desired for monitoring cellular states and cellular processes in a label-free manner. Raman spectroscopic imaging of highly dynamic systems is inhibited by relatively slow spectral acquisition on millisecond to second scale. Here, we report microsecond scale vibrational spectroscopic imaging by lock-in free parallel detection of spectrally dispersed stimulated Raman scattering signal. Using a homebuilt tuned amplifier array, our method enables Raman spectral acquisition, within the window defined by the broadband pulse, at the speed of 32 microseconds and with close to shot-noise limited detection sensitivity. Incorporated with multivariate curve resolution analysis, our platform allows compositional mapping of lipid droplets in single live cells, observation of intracellular retinoid metabolism, discrimination of fat droplets from protein-rich organelles in Caenorhabditis elegans, spectral detection of fast flowing tumor cells, and monitoring drug diffusion through skin tissue in vivo. The reported technique opens new opportunities for compositional analysis of cellular compartment in a microscope setting and high-throughput spectral profiling of single cells in a flow cytometer setting.

Sub-ns triplet state formation by non-geminate recombination in PSBTBT:PC70BM and PCPDTBT:PC60BM organic solar cells

Transient absorption spectroscopy and multivariate curve resolution analysis is used to demonstrate triplet state formation in low-bandgap polymer:fullerene photovoltaic blends.

The influence of polysorbate 80 on the radiochemical synthesis of a PET tracer in the FASTlab.

The aim of current study was to investigate the influence of a common non-ionic surfactant, polysorbate 80 (PS80), on radioactive labelling process of a novel PET tracer, [(18)F]Flutemetamol. Ferrous oxidation-xylenol orange (FOX) assay, in addition to UV/VIS and (1)H NMR spectroscopies were applied to characterise the composition of the PS80 solution after storage. Multivariate Curve Resolution (MCR) and PLS analysis was used to establish correlation between quality of the PS80 solution and the RCP obtained after labelling. The levels of unsaturated fatty acid moieties of PS80 were negatively correlated to RCP of [(18)F]Flutemetamol after synthesis. This explains the slight increase in RCP when stored PS80 solutions were applied in the synthesis. The mechanism behind this observation is suggested to be related to radiation induced radical formation in the unsaturated fatty acids, which subsequently causes instability of the PET tracer. UV/VIS spectroscopy was demonstrated to have the ability as a possible control tool for quality assurance of the studied radioactive labelling process. The presence of unsaturated fatty acid moieties in PS80 was found to be one of the most important factors responsible for the reduction in RCP of [(18)F]Flutemetamol after synthesis.

Solvatochromism of symmetrical 2,6-distyrylpyridines. An experimental and theoretical study

Seven symmetrical 2,6-distyrylpyridines, phenyl-substituted with hydrogen-bond donors, hydrogen-bond acceptors, halogens and hydrophobic moieties were synthesized and their spectroscopic characterization was done. Solvent effects on the absorption and fluorescence spectra were analyzed and quantified using the Kamlet–Taft and Catalán approach. The obtained results were rationalized by comparison of electrostatic potentials of the molecules in the ground and in excited state and by comparison of the frontier molecular orbitals (HOMO and LUMO), derived from quantum-mechanical calculations (HF, DFT, MP2). Analysis of the results revealed an important influence of non-specific (dispersive) interactions on the solvatochromic behavior of the compounds. 1D and 2D NMR data, in silico obtained conformational assembly of the compound, and the NMR analysis of molecular flexibility in solution (NAMFIS), were used to estimate population of conformers and to deconvolute the UV-Vis spectrum of representative derivative; inferring that the conformational assembly is more complex than was assumed in so far published literature data for this class of compounds. Along with this, the emission spectra of the representative compounds were decomposed by the Multivariate Curve Resolution analysis.

Multivariate Analysis Combined with Surface Mass Spectrometry (ToF-SIMS): Enabling Problem Solving and Expanding Application Space in an Industrial Environment

Surface characterization techniques, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) in particular, provide data that are multivariate in nature. Multivariate data reduction approaches can extract information and/or represent the data to facilitate interpretation of the data and correlation with measured properties. Examples discussed include multivariate curve resolution analysis of secondary ion mapping data (additive segregation in polymer resin pellets), combined positive and negative secondary ion mapping data after image registration, and secondary ion depth profiling data with depth scale correction.

Chemometric processing of second-order liquid chromatographic data with UV–vis and fluorescence detection. A comparison of multivariate curve resolution and parallel factor analysis 2

Second-order liquid chromatographic data with multivariate spectral (UV–vis or fluorescence) detection usually show changes in elution time profiles from sample to sample, causing a loss of trilinearity in the data. In order to analyze them with an appropriate model, the latter should permit a given component to have different time profiles in different samples. Two popular models in this regard are multivariate curve resolution-alternating least-squares (MCR-ALS) and parallel factor analysis 2 (PARAFAC2). The conditions to be fulfilled for successful application of the latter model are discussed on the basis of simple chromatographic concepts. An exhaustive analysis of the multivariate calibration models is carried out, employing both simulated and experimental chromatographic data sets. The latter involve the quantitation of benzimidazolic and carbamate pesticides in fruit and juice samples using liquid chromatography with diode array detection, and of polycyclic aromatic hydrocarbons in water samples, in both cases in the presence of potential interferents using liquid chromatography with fluorescence spectral detection, thereby achieving the second-order advantage. The overall results seem to favor MCR-ALS over PARAFAC2, especially in the presence of potential interferents.

Exploring metabolic pathways in vivo by a combined approach of mixed stable isotope-labeled Raman microspectroscopy and multivariate curve resolution analysis.

Understanding cellular metabolism is a major challenge in current systems biology and has triggered extensive metabolomics research, which in most cases involves destructive analysis. However, the information obtainable only in a nondestructive manner will be required for accurately mapping the global structure of the organism's metabolic network at a given instant. Here we report that metabolic pathways can be explored in vivo by mixed stable isotope-labeled Raman microspectroscopy in conjunction with multivariate curve resolution analysis. As a model system, we studied ergosterol biosynthesis in single living fission yeast cells grown in mixtures of normal and (13)C-labeled glucose as the sole carbon source. The multivariate spectral data analysis of space-resolved Raman spectra revealed the intrinsic spectra and relative abundances of all isotopomers of ergosterol whose carbon atoms in the 5,7-diene moiety of the sterol skeleton are either partly or fully substituted with (13)C. Our approach is applicable to other metabolites and will earn a place in the toolbox of metabolomic analysis.

Real time Raman imaging to understand dissolution performance of amorphous solid dispersions

We have employed for the first time Raman spectroscopic imaging along with multi-variate curve resolution (MCR) analysis to investigate in real time and in-situ the dissolution mechanisms that underpin amorphous solid dispersions, with data being collected directly from the dosage form itself. We have also employed a novel rotating disk dissolution rate (RDDR) methodology to track, through the use of high-performance liquid chromatography (HPLC), the dissolution trends of both drug and polymer simultaneously in multi-component systems. Two formulations of poorly water-soluble felodipine in a polymeric matrix of copovidone VA64 which have different drug loadings of 5% and 50% w/w were used as models with the aim of studying the effects of increasing the amount of active ingredient on the dissolution performance. It was found that felodipine and copovidone in the 5% dispersion dissolve with the same dissolution rate and that no Raman spectral changes accompanied the dissolution, indicating that the two components dissolve as single entity, whose behaviour is dominated by water-soluble copovidone. For the 50% drug-loaded dispersion, partial RDDR values of both felodipine and copovidone were found to be extremely low. MCR Raman maps along with classical Raman/X-ray powder diffraction (XRPD) characterisation revealed that after an initial loss of copovidone from the extrudate the drug re-crystallises, pointing to a release dynamics dependent on the low water solubility and high hydrophobicity of felodipine. Raman imaging revealed different rates of transition from amorphous to crystalline felodipine at different locations within the dosage form.

Molecular monitoring of epithelial-to-mesenchymal transition in breast cancer cells by means of Raman spectroscopy

In breast cancer the presence of cells undergoing the epithelial-to-mesenchymal transition is indicative of metastasis progression. Since metabolic features of breast tumour cells are critical in cancer progression and drug resistance, we hypothesized that the lipid content of malignant cells might be a useful indirect measure of cancer progression. In this study Multivariate Curve Resolution was applied to cellular Raman spectra to assess the metabolic composition of breast cancer cells undergoing the epithelial to mesenchymal transition. Multivariate Curve Resolution analysis led to the conclusion that this transition affects the lipid profile of cells, increasing tryptophan but maintaining a low fatty acid content in comparison with highly metastatic cells. Supporting those results, a Partial Least Square-Discriminant analysis was performed to test the ability of Raman spectroscopy to discriminate the initial steps of epithelial to mesenchymal transition in breast cancer cells. We achieved a high level of sensitivity and specificity, 94% and 100%, respectively. In conclusion, Raman microspectroscopy coupled with Multivariate Curve Resolution enables deconvolution and tracking of the molecular content of cancer cells during a biochemical process, being a powerful, rapid, reagent-free and non-invasive tool for identifying metabolic features of breast cancer cell aggressiveness at first stages of malignancy.

Heme degradation upon production of endogenous hydrogen peroxide via interaction of hemoglobin with sodium dodecyl sulfate

In this study the hemoglobin heme degradation upon interaction with sodium dodecyl sulfate (SDS) was investigated using UV–vis and fluorescence spectroscopy, multivariate curve resolution analysis, and chemiluminescence method. Our results showed that heme degradation occurred during interaction of hemoglobin with SDS producing three fluorescent components. We showed that the hydrogen peroxide, produced during this interaction, caused heme degradation. In addition, the endogenous hydrogen peroxide was more effective in hemoglobin heme degradation compared to exogenously added hydrogen peroxide. The endogenous form of hydrogen peroxide altered oxyHb to aquamethemoglobin and hemichrome at low concentration. In contrast, the exogenous hydrogen peroxide lacked this ability under same conditions.

Reactivity of Bis[3-(triethoxysilyl)propyl] Tetrasulfide (TESPT) Silane Coupling Agent over Hydrated Silica: Operando IR Spectroscopy and Chemometrics Study

The presence of physisorbed water during the silanization of silica is well-known for strongly influencing the silane reactivity at the interface. In this work, the reactivity of bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT), widely used in the rubber industry, on hydrated precipitation silica was investigated by time-resolved operando FTIR spectroscopy and chemometrics. The predominating reaction scheme is elucidated in conditions representative of industrial mixing process at the molecular scale. Based on multivariate curve resolution analysis and a quantitative kinetic model, it is shown that TESPT chemisorption is governed by two competitive reaction routes both producing only ethanol in the gas phase: (i) direct grafting reaction between an ethoxy moiety and a silica surface silanol and (ii) silane hydrolysis followed by co-condensation with a vicinal silane species. Reactions involving silanol–silanol condensation with production of water were not found to be significant. Although several types...

Decomposition of in vivo spatially offset Raman spectroscopy data using multivariate analysis techniques

The decomposition of spatially offset Raman spectra for complex multilayer systems, such as biological tissues, requires advanced techniques such as multivariate analyses. Often, in such situations, the decomposition methods can reach their limits of accuracy well before the limits imposed by signal‐to‐noise ratios. Consequently, more effective reconstruction methods could yield more accurate results with the same data set. In this study we process spatially offset Raman spectroscopy (SORS) data with three different multivariate techniques (band‐target entropy minimization (BTEM), multivariate curve resolution and parallel factor analysis (PARAFAC)) and compare their performance when analysing a spectrally challenging plastic model system and an even more challenging problem, the analysis of human bone transcutaneously in vivo. For the in vivo measurements, PARAFAC's requirement of multidimensional orthogonal data is addressed by recording SORS spectra both at different spatial offsets and at different anatomical points, the latter providing added dimensionality through the variation of skin/soft tissue thickness.The BTEM and PARAFAC methods performed the best on the plastic system with the BTEM more faithfully reconstructing the major Raman bands and PARAFAC the smaller more heavily overlapped features. All three methods succeeded in reconstructing the bone spectrum from the transcutaneous data and gave good figures for the phosphate‐to‐carbonate ratio (within 2% of excised human tibia bone); the PARAFAC gave the most accurate figure for the mineral‐to‐collagen ratio (20% less than excised human tibia bone).Previous studies of excised bones have shown that certain bone diseases (such as osteoarthritis, osteoporosis and osteogenesis imperfecta) are accompanied by compositional abnormalities that can be detected with Raman spectroscopy, the utility of a technique which could reconstruct bone spectra accurately is manifest. The results have relevance on the use of SORS in general. © 2014 Crown copyright. Journal of Raman Spectroscopy published by John Wiley & Sons, Ltd.

Multivariate curve resolution analysis applied to time-resolved synchrotron X-ray Absorption Spectroscopy monitoring of the activation of copper alumina catalyst

The pure X-ray Absorption (XAS) spectral constituents and related concentration profiles characterizing the reduction of a copper-based catalyst supported on hierarchically porous alumina were disentangled from a set of time-resolved Quick-XAS using a Multivariate Curve Resolution-methodology. First, the number of components involved in the data set and the range of existence of intermediate species were determined by Principal Component Analysis (PCA). Then, a Multivariate Curve Resolution with Alternating Least Squares fitting of the set of time-resolved Quick-XANES was performed using the constraints of non-negativity of both absorption and concentration and of closure of concentration. Consideration about the strategy of use of the chemometric methods and robustness regarding the reliability of results for time-resolved XAS data is discussed. The intermediate copper species determined by MCR-ALS is at the monovalent oxidation state and characterized by a local order of 2 oxygen atoms at 1.915Å. Upon isothermal treatment under 60% H2/He at 250°C for 30min, the intermediate species appears quite resistant to complete copper reduction. Copper speciation obtained using MCR-ALS method leads to very different results than those obtained using bulk CuO, Cu2O and metallic Cu as constituents, MCR-ALS concentration profile so-determined being fully consistent with the reducibility of the catalyst measured by TPR.

Monitoring the polymorphic transformation on the surface of carbamazepine tablets generated by heating using near-infrared chemical imaging and chemometric methodologies

This work presents the monitoring of the polymorphic transformation of carbamazepine (form III to form I) in pharmaceutical formulations as tablets, generated by heating at a temperature of 140°C for 7h, with data acquisition in each hour. Near infrared chemical imaging in conjunction with chemometric procedures was used to evaluate the change on the distribution of each polymorph in the tablet surface. The concentration distribution maps of polymorphic forms I and III of carbamazepine in the tablet were estimated by matrix-augmented multivariate curve resolution (MCR) and parallel factor analysis (PARAFAC). The concentration profile as a function of time under heating allowed a dynamic study of the system. The results show that MCR was able to provide information about the polymorphic transformation of carbamazepine tablets in the dynamic process, generating distribution maps for each acquisition time. PARAFAC provided global information about the system, but it was not able to completely resolve the spectral components.

Molecular component distribution imaging of living cells by multivariate curve resolution analysis of space-resolved Raman spectra

Label-free Raman microspectroscopy combined with a multivariate curve resolution (MCR) analysis can be a powerful tool for studying a wide range of biomedical molecular systems. The MCR with the alternating least squares (MCR-ALS) technique, which retrieves the pure component spectra from complicatedly overlapped spectra, has been successfully applied to in vivo and molecular-level analysis of living cells. The principles of the MCR-ALS analysis are reviewed with a model system of titanium oxide crystal polymorphs, followed by two examples of in vivo Raman imaging studies of living yeast cells, fission yeast, and budding yeast. Due to the non-negative matrix factorization algorithm used in the MCR-ALS analysis, the spectral information derived from this technique is just ready for physical and/or chemical interpretations. The corresponding concentration profiles provide the molecular component distribution images (MCDIs) that are vitally important for elucidating life at the molecular level, as stated by Schroedinger in his famous book, "What is life?" Without any a priori knowledge about spectral profiles, time- and space-resolved Raman measurements of a dividing fission yeast cell with the MCR-ALS elucidate the dynamic changes of major cellular components (lipids, proteins, and polysaccharides) during the cell cycle. The MCR-ALS technique also resolves broadly overlapped OH stretch Raman bands of water, clearly indicating the existence of organelle-specific water structures in a living budding yeast cell.