Chemometrics-assisted solid-state characterization of pharmaceutically relevant materials. Polymorphic substances

The importance of selecting crystal form for triazole fungicide tebuconazole to enhance its botryticidal activity

The growing evidences of resistant fungi stimulate fully understanding tebuconazole regarding its crystal structure on fungicidal activity. In this study, the crystal structures of six technical tebuconazoles (BX, HH, JP, QZ, SJ, and YT) were characterized by using high-resolution X-ray powder diffraction and three-dimensional crystal structure modeling. A structure-activity relationship of the tebuconazoles on the susceptible (HLS and YJS) or resistant (XHR) Botrytis cinerea isolates was analyzed, the differential tricarboxylic acid (TCA) cycle metabolism was determined, and molecular docking with sterol 14α-demethylase (CYP51) was performed. The results showed that tebuconazole existed in three types of crystal forms: an overlapping-pair conformation, a side-by-side-pair conformation, and a parallel-pair conformation. QZ with the parallel-pair conformation and the minimum crystal cell volume exhibited a higher activity and a lower resistant level. XHR possessed a higher content of TCA cycle metabolites and phosphate than YJS, but the exposure to QZ significantly reduced the contents of citrate, isocitrate, α-ketoglutarate and oxaloacetate in XHR, as did the exposure to other technical tebuconazoles. Moreover, the point mutations F487L, G464S, and G443S altered the binding properties of chiral stereoscopic R-QZ with CYP51 protein. Especially the G443S mutation promoted a weak linking of R-QZ with LEU380 and TYR126, and greatly slashed the binding action at lower docking score. In conclusion, our results evidenced an efficient crystal conformation of tebuconazole to improve botryticidal activity and a potential adaptability of B. cinerea to tebuconazole inhibition in TCA cycle metabolism and CYP51 protein mutation.

Research progress on the application of spectral imaging technology in pharmaceutical tablet analysis

Tablet as a traditional dosage form in pharmacy has the advantages of accurate dosage, ideal dissolution and bioavailability, convenient to carry and transport. The most concerned tablet quality attributes include active pharmaceutical ingredient (API) contents and polymorphic forms, components distribution, hardness, density, coating state, dissolution behavior, etc., which greatly affect the bioavailability and consistency of tablet final products. In the pharmaceutical industry, there are usually industry standard methods to analyze the tablet quality attributes. However, these methods are generally time-consuming and laborious, and lack a comprehensive understanding of the properties of tablets, such as spatial information. In recent years, spectral imaging technology makes up for the shortcomings of traditional tablet analysis methods because it provides non-contact and rich information in time and space. As a promising technology to replace the traditional tablet analysis methods, it has attracted more and more attention. The present paper briefly describes a series of spectral imaging techniques and their applications in tablet analysis. Finally, the possible application prospect of this technology and the deficiencies that need to be improved were also prospected.

Investigating kitchen sponge-derived microplastics and nanoplastics with Raman imaging and multivariate analysis

Microplastics can be found almost everywhere, including in our kitchens. The challenge is how to characterise them, particularly for the small ones (<1 μm), referred to as nanoplastics, when they are mixed with larger particles and other components. Herewith we advance Raman imaging to characterise microplastics and nanoplastics released from a dish sponge that we use every day to clean our cookware and eating utensils. The scanning electron microscopy result shows significantly different structures of the soft and hard layers of the sponge, with the hard layer being more likely to shed particles. By scanning the sample surface to generate a spectrum matrix, Raman imaging can significantly improve signal-noise-ratio, compared with individual Raman spectra. Through mapping the characteristic peaks from the matrix that contains hundreds, even thousands of Raman spectra, it is confirmed that the particles released from the soft and hard layers of the sponge are mainly Nylon PA6 and polyethylene terephthalate, respectively. Using principal component analysis (PCA) to decode the spectrum matrix further enhances the signal-noise ratio, which enables mapping the whole set of the spectrum, rather than the selected peaks. By optimising the Raman scanning parameters, the PCA-Raman imaging is able to reliably capture and visualise microplastics and nanoplastics released from both sides of the dish sponge, including a plastic-surrounding-sand composite structure. Overall, PCA-Raman imaging is a holistic and effective approach to characterising miniature plastic particles.

Application of chemometrics using direct spectroscopic methods as a QC tool in pharmaceutical industry and their validation

This present review described the application of chemometrics using direct spectroscopic methods at the quality control (QC) laboratory of Pharmaceutical Industries. Using chemometrics methods, all QC assessments during the fabrication processes of the drug preparations can be well performed. Chemometrics methods have some advantages compared to the conventional methods, i.e., non-destructive, can be performed directly to intake samples without any extractions, unnecessary performing stability studies, and cost-effective. To achieve reliable results of analyses, all methods must be validated first prior to routine applications. According to the current Pharmacopeia, the validation parameters are specificity/selectivity, accuracy, repeatability, intermediate precision, range, detection limit, quantification limit and robustness. These validation data must meet the acceptance criteria, that have been described by the analytical target profile (ATP) of the drug preparations.

Form quantitation in desmotropic mixtures of albendazole bulk drug by chemometrics-assisted analysis of vibrational spectra

Albendazole is a benzimidazole-type active pharmaceutical ingredient, and one of the most effective broad-spectrum anthelminthic agents. The drug has two solid-state forms (ALB I and ALB II) which are desmotropes; both of them seem to be currently marketed. However, using the wrong crystalline solid form for formulation may have an undesired impact on the physicochemical and/or bioavailability properties of the drug product. In order to develop new, simple, and less expensive alternatives toward the determination of the level of albendazole ALB I in its mixtures with ALB II, both desmotropes were prepared, and properly characterized by spectroscopic [solid-state nuclear magnetic resonance and near infrared (NIR)] and diffractometric (powder X-ray diffraction) methods. Then, the NIR and attenuated total reflectance-mid infrared (ATR-MIR) spectra of both forms were conveniently pre-treated and employed for the development and optimization of partial least squares (PLS)-potentiated quantification models (NIR/PLS and ATR-MIR/PLS). The latter were also subjected to validation (accuracy, precision, limits of detection and quantification, etc.) and further used to assess the level of the unwanted ALB II form in the bulk drug. The NIR/PLS method displayed the most satisfactory characteristics, including a limit of quantitation interval of 3.6 ± 1 %w/w; it outperformed both, the ATR-MIR/PLS counterpart (limit of quantitation interval of 14.0 ± 3.4 %w/w) and a previously published and more demanding Raman/PLS alternative.

Construction and application of the qualitative and quantitative analysis system of three boscalid polymorphs based on solid-state analytical methods and chemometric tools

In view of the important influence of solid form on the production and use of agrochemical, it is crucial to develop the accurate and useful qualitative and quantitative analysis system...

Discrimination of ranitidine hydrochloride crystals using X-ray micro-computed tomography for the evaluation of three-dimensional spatial distribution in solid dosage forms

A non-destructive discrimination method for crystals in solid dosage drug forms was first developed using a combination of Raman spectroscopy and X-ray micro-computed tomography (X-ray CT). Identification of the crystal form of an active pharmaceutical ingredient (API) at the appropriate pharmaceutical dosage is crucial, as the crystal form is a determinant of the quality and performance of the final formulation. To develop a non-destructive analytical methodology for the discrimination of solid API crystals in a solid dosage form, we utilized a combination of Raman spectroscopy and X-ray CT to differentiate between ranitidine crystal polymorphs (forms 1 and 2) in tablet formulations containing three excipients. The difference in electron density correlated with the true density between ranitidine polymorphs, thereby enabling the discrimination of crystal forms and visualization of their three-dimensional spatial localization inside the tablets through X-ray CT imaging. Furthermore, X-ray CT imaging revealed that the crystal particles were of varying densities, sizes, and shapes within the same batch. These findings suggest that X-ray CT is not only an imaging tool but also a unique method for quantitative physicochemical characterization to study crystal polymorphs and solid dosage forms.

Chemometrics-Assisted Raman Spectroscopy Characterization of Tunable Polymer-Peptide Hybrids for Dental Tissue Repair

The interfaces that biological tissues form with biomaterials are invariably defective and frequently the location where failure initiates. Characterizing the phenomena that lead to failure is confounded by several factors including heterogeneous material/tissue interfaces. To seamlessly analyze across these diverse structures presents a wealth of analytical challenges. This study aims to develop a molecular-level understanding of a peptide-functionalized adhesive/collagen hybrid biomaterial using Raman spectroscopy combined with chemometrics approach. An engineered hydroxyapatite-binding peptide (HABP) was copolymerized in dentin adhesive and dentin was demineralized to provide collagen matrices that were partially infiltrated with the peptide-functionalized adhesive. Partial infiltration led to pockets of exposed collagen-a condition that simulates defects in adhesive/dentin interfaces. The spectroscopic results indicate that co-polymerizable HABP tethered to the adhesive promoted remineralization of the defects. The spatial distribution of collagen, adhesive, and mineral as well as crystallinity of the mineral across this heterogeneous material/tissue interface was determined using micro-Raman spectroscopy combined with chemometrics approach. The success of this combined approach in the characterization of material/tissue interfaces stems from its ability to extract quality parameters that are related to the essential and relevant portions of the spectral data, after filtering out noise and non-relevant information. This ability is critical when it is not possible to separate components for analysis such as investigations focused on, in situ chemical characterization of interfaces. Extracting essential information from complex bio/material interfaces using data driven approaches will improve our understanding of heterogeneous material/tissue interfaces. This understanding will allow us to identify key parameters within the interfacial micro-environment that should be harnessed to develop durable biomaterials.

Polymorphism characterization of segesterone acetate: A comprehensive study using XRPD, FT-IR and Raman spectroscopy

Segesterone acetate (SA) is a promising and recently approved drug substance used as a contraceptive. SA has two major polymorphic forms, Form I and II. We have shown through indirect analysis that Form I is the more thermodynamically stable polymorphic form at room temperature, however, during the manufacturing process of SA drug products the solid-state stability must be shown to be under control. In the present work, a systematic study has been done using X-ray powder diffraction (XRPD), Fourier Transformed Infrared spectroscopy (FT-IR), and room temperature Raman spectroscopy on both micronized and non-micronized SA powder samples. XRPD showed a crystalline structure in both powder samples with a distinct coexistence of the polymorphic Forms I and II which was confirmed by FT-IR and Raman spectroscopy. The study showed that after thermal annealing a noticeable reduction of the amount of polymorphic Form II was found in both samples. Our results suggest the possibility of reducing the amount of SA Form II by thermal treatment inducing an irreversible solid-state transition to yield the thermodynamically more stable polymorphic Form I. To quantify the ratio of polymorphs I and II we have implemented a method that can be used as a routine analysis step in the manufacturing process of SA.

Fungicidal Effect of Pyraclostrobin against Botrytis cinerea in Relation to Its Crystal Structure

Pyraclostrobin (PYR) is a commonly used strobilurin fungicide, which inhibits mitochondrial respiration at the ubiquinol oxidation center site of the cytochrome bc1 complex. Little information is available regarding the crystal structure of PYR on its fungicidal effect. In this study, the crystal structures of eight PYRs (PYR-A to H) from different sources are determined by using high-resolution X-ray powder diffraction (XRPD) and model construction with the Pawley refinement module. The effects of PYRs on mycelium growth, the kinetics of mycelial growth, conidial germination, and tube elongation of conidia of Botrytis cinerea from tomato are compared. The level of organic acids in the mitochondrial tricarboxylic acid cycle of PYR-treated B. cinerea is analyzed. The results show that PYR-A to PYR-H have their own unique character of XRPD patterns, but the crystal morphology of eight PYRs presents in the triclinic crystal system and space group P1̅. PYR-D with the eclipsed conformation and rational edge angles α (72.599°) and β (98.612°) in the crystal cell shows the highest inhibitory effect against mycelium growth with EC₅₀ as 3.383 μg mL^-1, the best time-dependent effects on the mycelium growth kinetics, and the strongest inhibition on tube elongation of conidia, whereas PYR-E with anticonformation is the worst. Moreover, a significant accumulation of fumarate, malate, and oxalate in the PYR-D-treated mycelium is observed. These findings reinforce the need for a definite crystal structure of PYR to limit usage and mitigate future selection pressure for gray mold management.

Portable and benchtop Raman spectrometers coupled to cluster analysis to identify quinine sulfate polymorphs in solid dosage forms and antimalarial drug quantification in solution by AuNPs-SERS with MCR-ALS

This paper proposes for the first time: (a) a qualitative analytical method based on portable and benchtop backscattering Raman spectrometers coupled to hierarchical cluster analysis (HCA) and multivariate curve resolution - alternating least-squares (MCR-ALS) to identify two polymorphs of antimalarial quinine sulfate in commercial pharmaceutical tablets in their intact forms and (b) a quantitative analytical method based on gold nanoparticles (AuNPs) as active substrates for surface-enhanced Raman scattering (SERS) in combination with MCR-ALS to quantify quinine sulfate in commercial pharmaceutical tablets in solution. The pure concentration and spectral profiles recovered by MCR-ALS proved that both formulations present different polymorphs. These results were also confirmed by two clusters observed in the HCA model, according to their similarities within and among the samples that provided useful information about the homogeneity of different pharmaceutical manufacturing processes. AuNPs-SERS coupled to MCR-ALS was able to quantify quinine sulfate in the calibration range from 150.00 to 200.00 ng mL-1 even with the strong overlapping spectral profile of the background SERS signal, proving that it is a powerful ultrahigh sensitivity analytical method. This reduced linearity was validated throughout a large calibration range from 25.00 to 175.00 μg mL-1 used in a reference analytical method based on high performance liquid chromatography with a diode array detector (HPLC-DAD) coupled to MCR-ALS for analytical validation purposes, even in the presence of a coeluted compound. The analytical methods developed herein are fast, because second-order chromatographic data and first-order SERS spectroscopic data were obtained in less than 6 and 2 min, respectively. Concentrations of quinine sulfate were estimated with low root mean square error of prediction (RMSEP) values and a low relative error of prediction (REP%) in the range 1.8-4.5%.

Fusing data of different orders for environmental monitoring

In the present work a novel application of data fusion to an environmental monitoring study is proposed. This paper involves the joint analysis of zeroth-, first- and second-order data measured on a particular environmental system. The main advantage of this methodology is the possibility of analyzing the relationships of the different order data provided by several analytical techniques. This approach enables to achieve new knowledge, in a way that would be not accessible if considering the information individually. Environmental monitoring databases usually generate large amount of data. Multivariate statistical techniques are necessary to process all this information and obtain a correct interpretation. The Ludueña Stream located in Argentina was chosen as the study system. Samples from different sites of the basin were taken periodically. Conductivity and pH (zeroth-order data) were fused with near-infrared (NIR) spectra of suspended particulate material (first-order data) and with fluorescence emission-excitation matrices of dissolved organic matter (second-order data). Different chemometric algorithms made it possible to extract and merge all the information in a new database, enabling its later analysis as a whole. This methodology allowed to successfully studying the behavior of dissolved organic matter together with suspended particulate material and other specific variables, showing links between them. Their distributions along the basin and their evolutions over time were possible to obtain. Therefore, a simpler interpretation to evaluate the system status was achieved. This model allowed differentiating the variables affected by anthropic activities from those with a natural origin.

Industrial Applications of Terahertz Sensing: State of Play

This paper is a survey of existing and upcoming industrial applications of terahertz technologies, comprising sections on polymers, paint and coatings, pharmaceuticals, electronics, petrochemicals, gas sensing, and paper and wood industries. Finally, an estimate of the market size and growth rates is given, as obtained from a comparison of market reports.

Chemometric study of the excipients' influence on polymorphic-behavior. Mefenamic acid as case of study

The assessment of polymorphism is a problematical issue for regulatory agencies, because variations among crystalline forms of active pharmaceutical ingredient (API) can lead to changes in the efficacy and safety of formulated product. Such conversions are very hard to be detected, thus, the development of techniques for the identification, characterization and quantification of polymorphs results essential in all stages of the manufacturing process. The presence of excipients in formulated products may change the crystal stability of an API, by catalyzing a polymorphic transformation or stabilizing the less stable form. As paradox, all suitable analytical techniques (spectroscopies, thermal analysis, NMR and DRX, and others) for polymorphic analysis are affected by excipients. A deep understanding of the polymorphism-excipient relationship is in full accordance with Quality by Design (QbD) paradigm, the systematic approach focused in quality building into a product based in the full understanding of the products and process. In this work, a novel approach based on thermal stress, MIR monitoring, multivariate curve resolution with alternating least squares (MCR-ALS) and kinetic analysis was developed and applied to monitor polymorphism behavior of model API in formulated products. Commercial tablets, physical mixtures and commercial API, were processed and analyzed under the proposed approach. Commercial tablets of MFA revealed a fast conversion to Form II, contrasting to the behavior of the pure API. Physical mixtures showed similar behavior to commercial tablets, thus reduction in transformation times was related to MFA-excipients physical interaction, even at surface level. Calorimetric studies support the conclusion obtained. The developed approach could be extended to others APIs and other stress sources (humidity, solvents, mechanical forces and its combinations), being a valuable tool for QbD environment.

Transmission Low-Frequency Raman Spectroscopy for Quantification of Crystalline Polymorphs in Pharmaceutical Tablets

The purpose of this study was to quantify polymorphs of active pharmaceutical ingredients in pharmaceutical tablets using a novel transmission low-frequency Raman spectroscopy method. We developed a novel transmission geometry for low-frequency Raman spectroscopy and compared quantitative ability in transmission mode versus backscattering mode using chemometrics. We prepared two series of tablets, (1) containing different weight-based contents of carbamazepine form III and (2) including different ratios of carbamazepine polymorphs (forms I/III). From the relationship between the contents of carbamazepine form III and partial least-squares (PLS) predictions in the tablets, correlation coefficients in transmission mode ( R² = 0.98) were found to be higher than in backscattering mode ( R² = 0.97). The root-mean-square error of cross-validation (RMSECV) of the transmission mode was 3.9 compared to 4.9 for the backscattering mode. The tablets containing a mixture of carbamazepine (I/III) polymorphs were measured by transmission low-frequency Raman spectroscopy, and it was found that the spectral shape changed according to the ratio of polymorphs: the relationship between the actual content and the prediction showed high correlation. These findings indicate that transmission low-frequency Raman spectroscopy possesses the potential to complement existing analytical methods for the quantification of polymorphs.

The applicability of pharmaceutical polymeric blends for the fused deposition modelling (FDM) 3D technique: Material considerations-printability-process modulation, with consecutive effects on in vitro release, stability and degradation

The three dimensional printing (3DP) in the pharmaceutical domain constitutes an alternative, innovative approach compared to the conventional production methods. Fused deposition modelling (FDM), is a simple, cost-effective 3DP technique, however the range of pharmaceutical excipients that can be applied for this methodology is restricted. The study set to define the requirements of the FDM printability, using as technical support custom made, pharmaceutical polymer based filaments and to evaluate if these new dosage forms can live up to the current GMP/GCP quality standards. Formulation rationale was assessed in accordance to the apparatus functionality. Blends were pre-screened based on the processability under the API (carvedilol) thermogravimetric analysis determined critical limit. The technological process implied the use of FDM coupled with hot melt extrusion (HME), while printability was defined by means of thermal, rheological and mechanical measurements. From the pharmaceutical standpoint, the consistency of the in vitro dissolution kinetics was monitored 'at release' and 'in stability', while the print process impact was evaluated based on the previously determined processability potential. Results showed that FDM printability is multifactorial, with brittleness and melt viscosity as primary limitation factors. The increase in shear-thinning and flexural modulus can enable broader processability intervals, which in turn proved to be essential in limiting degradation product formation. The 3DP tablets released the API in an extended rate, however the temperature and humidity along production and storage should be carefully considered as it may affect the final product quality in time. In conclusion, HME + FDM can be considered as an alternative production methodology, with prospects of applicability in the clinical sector, however for some formulations extensive packaging development will be necessary before confirming their suitability.

Characterization of Solid-State Drug Polymorphs and Real-Time Evaluation of Crystallization Process Consistency by Near-Infrared Spectroscopy

Herein, we aimed to develop a strategy for evaluating the consistency of pharmaceutically important crystallization processes in real time, focusing on two typical cases of polymorphism. Theoretical analysis using a combination of ¹³C solid-state nuclear magnetic resonance spectroscopy with other polymorphism analysis techniques identified a number of marker signals, the changes of which revealed the presence of two or more structural orientations (lattices and/or molecular conformations) in both cefazolin sodium pentahydrate (α-CEZ-Na) and cephathiamidine (CETD). The proportions of these forms were shown to be batch-dependent and were defined as critical quality attributes (CQAs) to evaluate process consistency. Subsequently, real-time analysis by chemometrics-assisted near-infrared spectroscopy (NIR) was used to obtain useful information corresponding to CQAs. The pretreated spectra of representative samples were transformed by first derivative and vector normalization methods and used to calculate standard deviations at each wavelength and thus detect significant differences. As a result, vibrational responses of H₂O, CH₃, and CH₂ moieties (at 5,280, 4,431, and 4,339 cm^-1, respectively) were shown to be sensitive to the CQAs of α-CEZ-Na, which allowed us to establish a highly accurate discrimination model. Moreover, signals of H₂O, CONH, and COOH moieties (at 5,211, 5,284, and 5,369 cm^-1, respectively) played the same role in the case of CETD, as confirmed by theoretical results. Thus, we established a technique for the rapid evaluation of crystallization process consistency and deepened our understanding of crystallization behavior by using NIR in combination with polymorphism analysis techniques.