Preparation, characterization, and evaluation of celecoxib eutectic mixtures with adipic acid/saccharin for improvement of wettability and dissolution rate.

Celecoxib (CEL) is a selective cyclooxygenase-2 (COX-2) inhibitor therapeutically indicated for the treatment of rheumatoid arthritis, osteoarthritis, acute pain, and inflammation. However, its poor solubility and dissolution rate significantly hinders its broader application. In this study, eutectic mixtures, as binary pharmaceutical compositions of CEL with adipic acid (ADI) and saccharin (SAC), were identified through a phase diagram and Tammann's triangle intended to improve the wettability and dissolution rate of poorly water-soluble CEL. The contact angles at 0s in the liquid-solid interface were approximately θs (theta) 79.7 ±â€¯0.50° and 86.65 ±â€¯0.45° for CEL-ADI and CEL-SAC, respectively, which were much lower than the value obtained for CEL (92.05 ±â€¯0.75° θ). Moreover, a comparison of the disk intrinsic dissolution rate and powder dissolution properties demonstrated that eutectic mixtures significantly increased the dissolution rate compared with CEL and physical mixtures. A general relationship was elucidated and indicated that the dissolution rate was increased as the contact angle decreased (correlation coefficient, r = 0.9966 ±â€¯0.0031). Therefore, CEL-ADI and CEL-SAC eutectics may offer a novel formulation strategy to enhance the solubility and oral bioavailability of CEL.

Printing T3 and T4 oral drug combinations as a novel strategy for hypothyroidism.

Hypothyroidism is a chronic and debilitating disease that is estimated to affect 3% of the general population. Clinical experience has highlighted the synergistic value of combining triiodothyronine (T3) and thyroxine (T4) for persistent or recurrent symptoms. However, thus far a platform that enables the simultaneous and independent dosing of more than one drug for oral administration has not been developed. Thermal inkjet (TIJ) 2D printing is a potential solution to enable the dual deposition of T3 and T4 onto orodispersible films (ODFs) for therapy personalisation. In this study, a two-cartridge TIJ printer was modified such that it could print separate solutions of T3 and T4. Dose adjustments were achieved by printing solutions adjacent to each other, enabling therapeutic T3 (15-50 µg) and T4 dosages (60-180 µg) to be successfully printed. Excellent linearity was observed between the theoretical and measured dose for both T3 and T4 (R2 = 0.982 and 0.985, respectively) by changing the length of the print objective (Y-value). Rapid disintegration of the ODFs was achieved (<45 s). As such, this study for the first time demonstrates the ability to produce personalised dose combinations by TIJ printing T3 and T4 onto the same substrate for oral administration.

The Effect of Inkjet Printing over Polymeric Films as Potential Buccal Biologics Delivery Systems.

The buccal mucosa appears as a promissory route for biologic drug administration, and pharmaceutical films are flexible dosage forms that can be used in the buccal mucosa as drug delivery systems for either a local or systemic effect. Recently, thin films have been used as printing substrates to manufacture these dosage forms by inkjet printing. As such, it is necessary to investigate the effects of printing biologics on films as substrates in terms of their physical and mucoadhesive properties. Here, we explored solvent casting as a conventional method with two biocompatible polymers, hydroxypropyl methylcellulose, and chitosan, and we used electrospinning process as an electrospun film fabrication of polycaprolactone fibers due to its potential to elicit mucoadhesion. Lysozyme was used as biologic drug model and was formulated as a solution for printing by thermal inkjet printing. Films were characterized before and after printing by mechanical and mucoadhesive properties, surface, and ultrastructure morphology through scanning electron microscopy and solid state properties by thermal analysis. Although minor differences were detected in micrographs and thermograms in all polymeric films tested, neither mechanical nor mucoadhesive properties were affected by these differences. Thus, biologic drug printing on films was successful without affecting their mechanical or mucoadhesive properties. These results open way to explore biologics loading on buccal films by inkjet printing, and future efforts will include further in vitro and in vivo evaluations.

Preparation of a novel lipid-core micelle using a low-energy emulsification method.

High-energy methods for the manufacturing of nanomedicines are widely used; however, interest in low-energy methods is increasing due to their simplicity, better control over the process, and energy-saving characteristics during upscaling. Here, we developed a novel lipid-core micelle (LCM) as a nanocarrier to encapsulate a poorly water-soluble drug, nifedipine (NFD), by hot-melt emulsification, a low-energy method. LCMs are self-assembling colloidal particles composed of a hydrophobic core and a hydrophilic shell. Hybrid materials, such as Gelucire 44/14, are thus excellent candidates for their preparation. We characterized the obtained nanocarriers for their colloidal properties, drug loading and encapsulation efficiency, liquid state, stability, and drug release. The low-energy method hot-melt emulsification was successfully adapted for the manufacturing of small and narrowly dispersed LCMs. The obtained LCMs had a small average size of ~ 11 nm and a narrow polydispersity index (PDI) of 0.228. These nanocarriers were able to increase the amount of NFD dispersible in water more than 700-fold. Due to their sustained drug release profile and the PEGylation of Gelucire 44/14, these nanocarriers represent an excellent starting point for the development of drug delivery systems designed for long circulation times and passive targeting.

Powder Compression Properties of Paracetamol, Paracetamol Hydrochloride, and Paracetamol Cocrystals and Coformers.

The objective was to study the relationship between crystal structure, particle deformation properties, and tablet-forming ability for the monoclinic form of paracetamol (PRA), 2 cocrystals and a salt crystal of PRA in addition to 2 coformers (oxalic acid and 4,4'-bipyridine). Thus, the structure-property-performance relationship was investigated. Analytical powder compression was used for determination of effective plasticity, as inferred from the Heckel yield pressure and the Frenning parameter, and the elastic deformation was determined from in-die tablet elastic recovery. The plasticity could not be linked to the crystal lattice structure as crystals containing zig-zag layers displayed similar plasticity as crystals containing slip planes. In addition, crystals containing slip planes displayed both high and low plasticity. The mechanical properties could not be linked to the tablet-forming ability as the tablet tensile strength, unexpectedly, displayed a tendency to reduce with increased plasticity. Furthermore, the elastic deformation could not explain the tablet-forming ability. It was concluded that no relationship between structure-property-performance for PRA and its cocrystals and salt could be established. Thus, it was indicated that to establish such a relationship, an improved knowledge of crystallographic structure and interparticle bonding during compaction is needed.

Discrete multi-physics simulations of diffusive and convective mass transfer in boundary layers containing motile cilia in lungs.

In this paper, the mass transfer coefficient (permeability) of boundary layers containing motile cilia is investigated by means of discrete multi-physics. The idea is to understand the main mechanisms of mass transport occurring in a ciliated-layer; one specific application being inhaled drugs in the respiratory epithelium. The effect of drug diffusivity, cilia beat frequency and cilia flexibility is studied. Our results show the existence of three mass transfer regimes. A low frequency regime, which we called shielding regime, where the presence of the cilia hinders mass transport; an intermediate frequency regime, which we have called diffusive regime, where diffusion is the controlling mechanism; and a high frequency regime, which we have called convective regime, where the degree of bending of the cilia seems to be the most important factor controlling mass transfer in the ciliated-layer. Since the flexibility of the cilia and the frequency of the beat changes with age and health conditions, the knowledge of these three regimes allows prediction of how mass transfer varies with these factors.

Personalisation of warfarin therapy using thermal ink-jet printing.

Warfarin is a widely used anticoagulant that is critical in reducing patient morbidity and mortality associated with thromboembolic disorders. However, its narrow therapeutic index and large inter-individual variability can lead to complex dosage regimes. Formulating warfarin as an orodispersible film (ODF) using thermal ink-jet (TIJ) printing could enable personalisation of therapy to simplify administration. Commercial TIJ printers are currently unsuitable for printing the milligram dosages, typically required for warfarin therapy. As such, this study aimed to modify a commercial TIJ printing system to formulate personalised warfarin ODFs containing therapeutic dosages. A TIJ printer was modified successfully with the printer functionality intact; the substrate (paper) rolling mechanism of the printer was replaced by printing onto a stationary stage. Free film substrates were composed of hydroxypropyl methylcellulose (20%w/w) and glycerol (3%w/w). The resulting ODFs were characterised for morphology, disintegration, solid-state properties and drug content. Printed film stability was assessed at 40 °C/75% relative humidity for 30 days. Therapeutic warfarin doses (1.25 and 2.5 mg) were successfully printed onto the film substrates. Excellent linearity was observed between the theoretical and measured dose by changing the warfarin feed concentration (R2 = 0.9999) and length of the print objective, i.e. the Y-value, (R2 = 0.9998). Rapid disintegration of the ODFs was achieved. As such, this study successfully formulated personalised warfarin ODFs using a modified TIJ printer, widening the range of applications for TIJ printing to formulate narrow therapeutic index drugs.

Investigation of supersaturation and in vitro permeation of the poorly water soluble drug ezetimibe.

The interplay between supersaturation, precipitation and permeation characteristics of the poorly water-soluble drug ezetimibe (EZ) was investigated. Supersaturation and precipitation characteristics of EZ in the presence of Caco-2 cells were compared to those in a cell-free environment. The effect of the water-soluble polymer polyvinyl pyrrolidone (PVP-K30) on the supersaturation, precipitation and transport of EZ was also investigated and the amount of drug taken up by Caco-2 cells was quantified. A one-compartment setup without Caco-2 cells (i.e. in the wells of cell-culture plates) was used to mimic a non-sink in vitro dissolution chamber. The two-compartment Caco-2 cell monolayer setup (with apical and basolateral compartments) was used to investigate how the absorption of EZ affects supersaturation. EZ in varying degrees of supersaturation (DS; 10, 20, 30 and 40) was introduced into the one-compartment setup or the apical chamber of the two-compartment setup. Samples were collected at specific times to determine supersaturation, precipitation and permeation. At the end of the study, Caco-2 cells were lysed and the intracellular amount of EZ was quantified. In the one-compartment setup, a high DS was associated with rapid precipitation. Supersaturation was maintained for longer time periods and precipitation was lower in the presence of Caco-2 cells. There were no significant differences in the absorption rate of the drug, even at high concentrations on the apical side. Permeability coefficients for all supersaturated solutions (i.e. DS 10-40) were significantly (p < 0.05) different from those when EZ was present in crystalline form. Both concentrations of PVP-K30 (i.e. 0.05% and 0.1% w/v) improved solubility and supersaturation of EZ when added to the apical side, however, the increase in absorption at the higher concentration was not proportional. The amount of intracellular EZ increased with increasing DS in the apical side, until the saturation limit was reached in the cells (i.e. at DS 30 and higher). This study demonstrated that precipitation of EZ could be overestimated when supersaturation was investigated without the implementation of an absorption compartment in vitro, both in the absence and in the presence of polymer.

Reducing the stigma of long acting injectable antipsychotics - current concepts and future developments.

BACKGROUND: Long acting injectable antipsychotics (LAI-APs) are considered a major advance in psychiatric treatment concerning treatment adherence and outcomes. Yet, both, doctors and patients remain sceptical. AIM: To explain the rationale for using LAI-APs, review their effectiveness and explore barriers to use. METHOD: Clinical overview of LAI-APs from the patient and doctor's perspective. RESULTS: LAI-APs were developed to increase adherence to treatment, thereby improving treatment outcomes. LAI-APs may reduce the risk of relapse and hospitalisation. Yet, the evidence from the few meta-analyses available remains weak. Both patients and doctors may associate LAI-APs with stigma and coercion. Current means of improving adherence include more focus on the therapeutic relationship, better information, adverse effects minimisation and half-life extension of LAI-APs. Future means of improving adherence include novel administration techniques that abolish the need for injection. CONCLUSIONS: For both, clinicians and drug developers, drug adherence remains a major target for improving treatment outcomes.

Experimental Studies and Modeling of the Drying Kinetics of Multicomponent Polymer Films.

The process of drying thin polymer films is an important operation that influences the film structure and solid state, and the stability of the product. The purpose of this work was to study and model the drying kinetics of multicomponent films based on two polymers: hydroxypropyl methylcellulose (HPMC, amorphous) and polyvinyl alcohol (PVA, semicrystalline). The isothermal drying kinetics of the films at different temperatures (40, 60, and 80°C) were studied using thermo-gravimetric analysis (TGA) and convection oven methods. Solid-state characterization tools used in the study included polarization and hot-stage microscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The drying kinetics of HPMC and PVA films in the TGA apparatus and convection oven were comparable. The three-parameter (W max, τ, n) Hill equation successfully modeled the experimental drying kinetics. The time factor τ in the Hill equation nicely explained two drying phases in the films. Solid-state phase changes occurring in the films during dehydration had a bearing on the drying kinetics and mechanisms. TGA can be used as a simple tool to determine the end points in drying processes using ovens or tunnels. The three-parameter Hill equation explained the drying kinetics and diffusion mechanisms of the solvent through the polymer films for the first time. This study advances our understanding of film drying, in particular for pharmaceutically relevant thin films.

Dry powder inhalers: An overview of the in vitro dissolution methodologies and their correlation with the biopharmaceutical aspects of the drug products.

In vitro dissolution testing is routinely used in the development of pharmaceutical products. Whilst the dissolution testing methods are well established and standardized for oral dosage forms, i.e. tablets and capsules, there are no pharmacopoeia methods or regulatory requirements for testing the dissolution of orally inhaled powders. Despite this, a wide variety of dissolution testing methods for orally inhaled powders has been developed and their bio-relevance has been evaluated. This review provides an overview of the in vitro dissolution methodologies for dry inhalation products, with particular emphasis on dry powder inhalers, where the dissolution behavior of the respirable particles can have a role on duration and absorption of the drug. Dissolution mechanisms of respirable particles as well as kinetic models have been presented. A more recent biorelevant dissolution set-ups and media for studying inhalation biopharmaceutics were also reviewed. In addition, factors affecting interplay between dissolution and absorption of deposited particles in the context of biopharmaceutical considerations of inhalation products were examined.

Effect of surfactants and drug load on physico-mechanical and dissolution properties of nanocrystalline tadalafil-loaded oral films.

The aim of the present work was to prepare tadalafil (TDF) nanocrystals-loaded oral polymeric films (OFs) and investigate the effect of hydrophilic surfactants and drug loads on the physico-mechanical and dissolution properties. The nanosuspensions of TDF were prepared by high shear homogenization. HPMC based placebo casting film gel was prepared and mixed with TDF nanosuspensions. Films were casted using an automated film applicator and dried at 60°C for 45min. Particle size (PS), polydispersity index (PDI), and zeta potential (ZP) of TDF nanosuspensions were measured in a Zetasizer. The films were characterized using SEM, AFM, DSC, TGA and PXRD. The mechanical properties and in vitro drug release were determined using standard methods. TDF existed in crystalline form and the particles remained in the nano-range in redispersed films. TDF nanocrystals were embedded in the polymeric matrix and the drug loaded films were rough on the surface. Mechanical properties of the films varied with changes in drug load and surfactant. Significant changes in the disintegration times were noticed in films containing surfactants compared to surfactant-free films. About 80% of the drug release was observed between 3 and 30min. TPGS showed better TDF release from the films at different drug loads. CHEMICAL COMPOUNDS: Hydroxy propyl methyl cellulose (PubChem CID: 57503849); Glycerol (PubChem CID: 753); Pluronic F-68 (PubChem CID: 24751); Vitamin E TPGS (PubChem CID: 71406).

Experimental cocrystal screening and solution based scale-up cocrystallization methods.

Cocrystals are crystalline single phase materials composed of two or more different molecular and/or ionic compounds generally in a stoichiometric ratio which are neither solvates nor simple salts. If one of the components is an active pharmaceutical ingredient (API), the term pharmaceutical cocrystal is often used. There is a growing interest among drug development scientists in exploring cocrystals, as means to address physicochemical, biopharmaceutical and mechanical properties and expand solid form diversity of the API. Conventionally, coformers are selected based on crystal engineering principles, and the equimolar mixtures of API and coformers are subjected to solution-based crystallization that are commonly employed in polymorph and salt screening. However, the availability of new knowledge on cocrystal phase behaviour in solid state and solutions has spurred the development and implementation of more rational experimental cocrystal screening as well as scale-up methods. This review aims to provide overview of commonly employed solid form screening techniques in drug development with an emphasis on cocrystal screening methodologies. The latest developments in understanding and the use of cocrystal phase diagrams in both screening and solution based scale-up methods are also presented. Final section is devoted to reviewing the state of the art research covering solution based scale-up cocrystallization process for different cocrystals besides more recent continuous crystallization methods.

Buccal Dosage Forms: General Considerations for Pediatric Patients.

The development of an appropriate dosage form for pediatric patients needs to take into account several aspects, since adult drug biodistribution differs from that of pediatrics. In recent years, buccal administration has become an attractive route, having different dosage forms under development including tablets, lozenges, films, and solutions among others. Furthermore, the buccal epithelium can allow quick access to systemic circulation, which could be used for a rapid onset of action. For pediatric patients, dosage forms to be placed in the oral cavity have higher requirements for palatability to increase acceptance and therapy compliance. Therefore, an understanding of the excipients required and their functions and properties needs to be particularly addressed. This review is focused on the differences and requirements relevant to buccal administration for pediatric patients (compared to adults) and how novel dosage forms can be less invasive and more acceptable alternatives.

Effect of plasticizers on the physico-mechanical properties of pullulan based pharmaceutical oral films.

The effect of different plasticizers (glycerol, vitamin E TPGS and triacetin) and their concentrations on the physico-mechanical properties of pullulan based oral films was studied. A full factorial (32) design of experiments was used. Elastic modulus, tensile strength, elongation at break and disintegration time were selected as response variables. Modulated differential scanning calorimeter (MDSC) was used for determining glass transition temperature (Tg) of pullulan films. The surface morphology of films was evaluated by SEM, while ATR-FTIR was used to obtain a molecular level understanding of polymer-plasticizer interactions. The DoE analysis allowed for the modelling of tensile strength and elongation at break. The highest elongations were observed in glycerol at 20% w/w. Majority of the films disintegrated within one minute without significant differences. ATR-FTIR spectra of pullulan alone and different plasticizer blend films show characteristic molecular interactions. The present study concluded that glycerol is suitable plasticizer compared to others for manufacturing pullulan based oral films.

Relationship between mechanical properties and crystal structure in cocrystals and salt of paracetamol.

Objectives were to study mechanical properties of various solid forms of paracetamol and relate to their crystal structures. Paracetamol form I (PRA), its cocrystals with oxalic acid (PRA-OXA) and 4,4-bipyridine (PRA-BPY) and hydrochloride salt (PRA-HCL) were selected. Cocrystals and salt were scaled-up using rational crystallization methods. The resulting materials were subjected to different solid-state characterizations. The powders were sieved and 90-360 µm sieve fraction was considered. These powders were examined by scanning electron microscopy (SEM) and densities were determined. Tablets were made at applied pressures of 35-180 MPa under controlled conditions and the tablet height, diameter and hardness were measured. Tensile strength and porosity of the tablets were estimated using well known models. Crystal structures of these systems were visualized and slip planes were identified. Cocrystal and salt of PRA were physically pure. Sieved powders had comparable morphologies and particle size. The apparent and theoretical densities of powders were similar, but no clear trends were observed. The tensile strengths of these compacts were increased with increasing pressure whereas tabletability decreased in the order oxalic acid > PRA-HCL ≈ PRA-OXA > BPY > PRA-BPY. Tablet tensile strength decreases exponentially with increasing porosity with the exception of PRY-BPY and BPY. Slip plane prediction based on attachment energies may not be independently considered. However, it was possible to explain the improved mechanical properties of powders based on the crystal structure. Cocrystallization and salt formation have introduced structural features that are responsible for improved tableting properties of PRA.

Dissolution and precipitation behavior of ternary solid dispersions of ezetimibe in biorelevant media.

The effects of different formulations and processes on inducing and maintaining the supersaturation of ternary solid dispersions of ezetimibe (EZ) in two biorelevant media fasted-state simulated intestinal fluid (FaSSIF) and fasted-state simulated gastric fluid (FaSSGF) at different temperatures (25 °C and 37 °C) were investigated in this work. Ternary solid dispersions of EZ were prepared by adding polymer PVP-K30 and surfactant poloxamer 188 using melt-quenching and spray-drying methods. The resulting solid dispersions were characterized using scanning electron microscopy, differential scanning calorimetry (DSC), modulated DSC, powder X-ray diffraction and Fourier transformation infrared spectroscopy. The dissolution of all the ternary solid dispersions was tested in vitro under non-sink conditions. All the prepared solid dispersions were amorphous in nature. In FaSSIF at 25 °C, the melt-quenched (MQ) solid dispersions of EZ were more soluble than the spray-dried (SD) solid dispersions and supersaturation was maintained. However, at 37 °C, rapid and variable precipitation behavior was observed for all the MQ and SD formulations. In FaSSGF, the melting method resulted in better solubility than the spray-drying method at both temperatures. Ternary solid dispersions show potential for improving solubility and supersaturation. However, powder dissolution experiments of these solid dispersions of EZ at 25 °C may not predict the supersaturation behavior at physiologically relevant temperatures.

Design of salmon calcitonin particles for nasal delivery using spray-drying and novel supercritical fluid-assisted spray-drying processes.

The overall aim of this study was to prepare a nasal powder formulation of salmon calcitonin (sCT) using an absorption enhancer to improve its bioavailability. In this work, powder formulations for nasal delivery of sCT were studied using various absorption enhancers and stabilizers. Powders were prepared by two different methods: conventional spray-drying (SD) and novel supercritical fluid-assisted spray-drying (SASD) to investigate the role of CO2 in the particle formation process. The prepared sCT powder formulations were characterized by several analyses; powder X-ray diffractometry (PXRD), scanning electron microscopy (SEM), and the Fourier transform infrared (FT-IR) spectroscopy method. The particle size distribution was also evaluated. In vivo absorption tests were carried out in Sprague-Dawley rat using the prepared powder formulations, and the results were compared to those of raw sCT. Quantitative analysis by high-performance liquid chromatography (HPLC) indicated that sCT was chemically stable after both the SD and SASD processes. Results of PXRD, SEM, and FT-IR did not indicate a strong interaction or defragmentation of sCT. The in vivo absorption test showed that SD- and SASD-processed sCT powders increased the bioavailability of the drug when compared to the nasal administration of raw sCT. In addition, SASD-processed sCT exhibited higher nasal absorption when compared with SD-processed sCT in all formulations due to a reduction of particle size. The results from this study illustrate that the preparation of nasal powders using the SASD process could be a promising approach to improve nasal absorption of sCT.

Theophylline cocrystals prepared by spray drying: physicochemical properties and aerosolization performance.

The purpose of this work was to characterize theophylline (THF) cocrystals prepared by spray drying in terms of the physicochemical properties and inhalation performance when aerosolized from a dry powder inhaler. Cocrystals of theophylline with urea (THF-URE), saccharin (THF-SAC) and nicotinamide (THF-NIC) were prepared by spray drying. Milled THF and THF-SAC cocrystals were also used for comparison. The physical purity, particle size, particle morphology and surface energy of the materials were determined. The in vitro aerosol performance of the spray-dried cocrystals, drug-alone and a drug-carrier aerosol, was assessed. The spray-dried particles had different size distributions, morphologies and surface energies. The milled samples had higher surface energy than those prepared by spray drying. Good agreement was observed between multi-stage liquid impinger and next-generation impactor in terms of assessing spray-dried THF particles. The fine particle fractions of both formulations were similar for THF, but drug-alone formulations outperformed drug-carrier formulations for the THF cocrystals. The aerosolization performance of different THF cocrystals was within the following rank order as obtained from both drug-alone and drug-carrier formulations: THF-NIC>THF-URE>THF-SAC. It was proposed that micromeritic properties dominate over particle surface energy in terms of determining the aerosol performance of THF cocrystals. Spray drying could be a potential technique for preparing cocrystals with modified physical properties.

Exploiting the Synergy of Powder X-ray Diffraction and Solid-State NMR Spectroscopy in Structure Determination of Organic Molecular Solids.

We report a strategy for structure determination of organic materials in which complete solid-state nuclear magnetic resonance (NMR) spectral data is utilized within the context of structure determination from powder X-ray diffraction (XRD) data. Following determination of the crystal structure from powder XRD data, first-principles density functional theory-based techniques within the GIPAW approach are exploited to calculate the solid-state NMR data for the structure, followed by careful scrutiny of the agreement with experimental solid-state NMR data. The successful application of this approach is demonstrated by structure determination of the 1:1 cocrystal of indomethacin and nicotinamide. The 1H and 13C chemical shifts calculated for the crystal structure determined from the powder XRD data are in excellent agreement with those measured experimentally, notably including the two-dimensional correlation of 1H and 13C chemical shifts for directly bonded 13C-1H moieties. The key feature of this combined approach is that the quality of the structure determined is assessed both against experimental powder XRD data and against experimental solid-state NMR data, thus providing a very robust validation of the veracity of the structure.