Cocrystallization improves the tabletability of ligustrazine despite a reduction in plasticity

Cocrystallization is an effective method for altering the tableting performance of crystals by modifying their mechanical properties. In this study, cocrystals of ligustrazine (LIG) with malonic acid (MA) and salicylic acid (SA) were investigated to better understand how modifying crystal structure can affect tableting properties. LIG suffered from overcompression at high pressures despite its high plasticity. Both LIG-MA and LIG-SA displayed lower plasticity than LIG, which was confirmed by both an in-die Heckel and energy framework analyses. The LIG-MA cocrystal displayed slightly worse tabletability than LIG, as expected from its lower plasticity. However, LIG-SA surprisingly showed improved tabletability despite its lower plasticity. This was explained by the higher bonding strength of LIG-SA compared with LIG. This work not only provided new examples of tabletability modulation through crystal engineering but also highlighted the risk of failed tabletability predictions based on plasticity alone. Instead, more reliable tabletability predictions of different crystal forms must consider the bonding area - bonding strength interplay.

Intermediates in Mechanochemical Reactions

Mechanochemical reactions offer methodological and environmental advantages for chemical synthesis, constantly attracting attention within the scientific community. Besides unmistakable sustainability advantages, the conditions under which mechanochemical reactions occur, namely solventless conditions, sometimes facilitate the isolation of otherwise labile or inaccessible products. Despite these advantages, limited knowledge exists regarding the mechanisms of these reactions and the types of intermediates involved. Nevertheless, in an expanding number of cases, ex situ and in situ monitoring techniques have allowed for the observation, characterization, and isolation of reaction intermediates in mechanochemical transformations. In this Minireview, we present a series of examples in which reactive intermediates have been detected in mechanochemical reactions spanning organic, organometallic, inorganic, and materials chemistry. Many of these intermediates were stabilized by non-covalent interactions, which played a pivotal role in guiding the chemical transformations. We believe that by uncovering and understanding such instances, the growing mechanochemistry community could find novel opportunities in catalysis and discover new mechanochemical reactions while achieving simplification in chemical reaction design.

Reply to comments by Dr. Ali Shayanfar

Several clarifications are made pertaining to the study on the cocrystallization of 5-fluorouracil (5-FU) and gallic acid (GA). Dr. Shayanfar's perspective in the solubility and biological activity of cocrystals is recognized, and his insightful guidance on solubility determination methodologies is greatly appreciated. A misconception concerning the cytotoxicity assay methodology in the Shayanfar's comments is addressed. Furthermore, the stability of the 5-FU-GA cocrystal during solubility measurement is highlighted, as evidenced by XRD analysis of residual solids. Lastly, the independence of the elevated cytotoxicity of the cocrystal from 5-FU solubility is deliberated, aligning with preceding research outcomes.

Comments on "Cocrystallization of 5-fluorouracil with gallic acid: A novel 5-fluorouracil cocrystal displaying synergistic anti-tumor activity both in oral and intraperitoneal injection administration"

This commentary highlights the significance of the solution stability and preparation of a solution of cocrystal in evaluating anti-tumor activity. It introduces a challenging issue regarding improving the biological activity of an API in cocrystal form.

Efficient cocrystal coformer screening based on a Machine learning Strategy: A case study for the preparation of imatinib cocrystal with enhanced physicochemical properties

Cocrystal engineering, which involves the self-assembly of two or more components into a solid-state supramolecular structure through non-covalent interactions, has emerged as a promising approach to tailor the physicochemical properties of active pharmaceutical ingredient (API). Efficient coformer screening for cocrystal remains a challenge. Herein, a prediction strategy based on machine learning algorithms was employed to predict cocrystal formation and seven reliable models with accuracy over 0.890 were successfully constructed. Imatinib was selected as the model drug and the models established were applied to screen 31 potential coformers. Experimental verification results indicated RF-8 is the optimal model among seven models with an accuracy of 0.839. When the seven models were combined for coformer screening of Imatinib, the combinational model achieved an accuracy of 0.903, and eight new solid forms were observed and characterized. Benefiting from intermolecular interactions, the obtained multicomponent crystals displayed enhanced physicochemical properties. Dissolution and solubility experiments showed the prepared multicomponent crystals had higher cumulative dissolution rate and remarkably improved the solubility of imatinib, and IM-MC exhibited comparable solubility to Imatinib mesylate α form. Stability test and cytotoxicity results showed that multicomponent crystals exhibited excellent stability and the drug-drug cocrystal IM-5F exhibited higher cytotoxicity than pure API.

Discovery of a potent and highly selective inhibitor of SIRT6 against pancreatic cancer metastasis in vivo

Pancreatic cancer, one of the most aggressive malignancies, has no effective treatment due to the lack of targets and drugs related to tumour metastasis. SIRT6 can promote the migration of pancreatic cancer and could be a potential target for antimetastasis of pancreatic cancer. However, highly selective and potency SIRT6 inhibitor that can be used in vivo is yet to be discovered. Here, we developed a novel SIRT6 allosteric inhibitor, compound 11e, with maximal inhibitory potency and an IC50 value of 0.98 ± 0.13 μmol/L. Moreover, compound 11e exhibited significant selectivity against other histone deacetylases (HADC1‒11 and SIRT1‒3) at concentrations up to 100 μmol/L. The allosteric site and the molecular mechanism of inhibition were extensively elucidated by cocrystal complex structure and dynamic structural analyses. Importantly, we confirmed the antimetastatic function of such inhibitors in four pancreatic cancer cell lines as well as in two mouse models of pancreatic cancer liver metastasis. To our knowledge, this is the first study to reveal the in vivo effects of SIRT6 inhibitors on liver metastatic pancreatic cancer. It not only provides a promising lead compound for subsequent inhibitor development targeting SIRT6 but also provides a potential approach to address the challenge of metastasis in pancreatic cancer.

Hydrophilic Cocrystals with Water Switched Luminescence

Utilizing water molecules to regulate the luminescence properties of solid materials is highly challenging. Herein, we develop a strategy to produce water-triggered luminescence-switching cocrystals by coassembling hydrophilic donors with electron-deficient acceptors, where 1,2,4,5-Tetracyanobenzene (TCNB) was used as the electron acceptor and pyridyl benzimidazole derivatives were used as the electron donors enabling multiple hydrogen-bonds. Two cocrystals, namely 2PYTC and 4PYTC were obtained and showed heat-activated emission, and such emission could be quenched or weakened by adding water molecules. The cocrystal structure exhibited the donor molecule that can form multiple hydro bonds with water and acceptor molecules due to the many nitrogen atoms of them. The analyses of the photophysical data, powder X-ray diffraction, and other data confirmed the reversible fluorescence "on-off" effects were caused by eliminating and adding water molecules in the crystal lattice. The density functional theory calculations indicate that the vibration of the O-H bond of water molecules in the cocrystal can absorb the excitation energy and suppress fluorescence. Furthermore, the obtained cocrystals also showed temperature, humidity, and H+ /NH4 + responsive emission behavior, which allows their applications as thermal and humidity sensors, and multiple information encryptions. This research paves the way for preparing intelligent hydrophilic organic cocrystal luminescent materials.

The bioavailability enhancement and insight into the action mechanism of poorly soluble natural compounds from co-crystals preparation: Oridonin as an example

BACKGROUND

Natural bioactive molecules are important sources for the development of new drugs. However, most of them were limited in clinical applications due to their low aqueous solubility and bioavailability. Oridonin (ORI) is a powerful anticancer compound with above characteristics.

OBJECTIVE

This study aimed to find an effective method to improve the bioavailability of poorly soluble natural compounds, and explore the action mechanisms of them to promote their application.

RESULTS

In this study, ORI-nicotinamide (NCT) cocrystal was successfully prepared for the first time to overcome the defects of ORI. The solubility and oral bioavailability of cocrystal (COC) increased 1.34 and 1.18 times compared with ORI. Moreover, MTT assay was applied to compare the cytotoxicity of positive control drug sorafenib with ORI and COC. The IC50 values of sorafenib, ORI and COC on HepG2 cells were 7.61, 8.79 and 7.36 nmol·mL-1, which indicated that the cytotoxicity of ORI could be enhanced by cocrystal preparation. The cellular metabolomics was innovatively introduced to gain insight into the difference of cytotoxicity mechanism between ORI and COC. The results showed that there were 78 metabolites with significant differences in content between the two groups, while these differential metabolites were related to 11 metabolic pathways. Among these, glycerophospholipid metabolism and cysteine and methionine metabolism were the significant differential pathways, and the downregulation of PC(14:0/16:1(9z)) and upregulation of homocysteine were the likely main reasons for higher cytotoxicity of COC.

CONCLUSIONS

This study has presented novel approaches for enhancing the bioavailability and drug efficacy of natural compounds, while also offering fresh insights into the underlying action mechanisms of pharmaceutical cocrystals.

Biodegradable nanocomposite poly(lactic acid) foams containing carvacrol-based cocrystal prepared by supercritical CO2 processing for controlled release in active food packaging

Compounds derived from essential oils have been used in active packaging, but their volatility and degradability negatively affect stability and leads to high release rates. The present study aimed to develop PLA bionanocomposite foams loaded with carvacrol cocrystal by supercritical CO2 and its release into a food simulant for control release in food packaging. For this purpose, 4,4'-bipyridine was used as coformer and carvacrol as active agent. Cocrystallized closed cell foams were obtained using supercritical CO2 and were characterized in terms of their physicochemical and mechanical properties, and release kinetics to a D1 simulant were evaluated as well as the antioxidant ability. A better overall mechanical behavior due to the nanoclay promoting a higher interfacial adhesion with the polymeric matrix was revealed. A higher incorporation of carvacrol was observed in samples with higher C30B content. The incorporated cocrystals showed a decrease of one order of magnitude in the estimated effective diffusion coefficient of carvacrol and showed antioxidant activity. These results suggest that the nanocomposite foam containing carvacrol-based cocrystals could be used in active packaging systems with controlled release characteristics, especially with highly volatile compounds, and can be proposed for other fields such as biomedical applications.

Improving the physicochemical and pharmacokinetic properties of olaparib through cocrystallization strategy

Olaparib (OLA) is the first PARP inhibitor worldwide used for the treatment of ovarian cancer. However, the oral absorption of OLA is extremely limited by its poor solubility. Herein, pharmaceutical cocrystallization strategy was employed to optimize the physicochemical and pharmacokinetic properties. Four cocrystals of OLA with oxalic acid (OLA-OA), malonic acid (OLA-MA), fumaric acid (OLA-FA) and maleic acid (OLA-MLA) were successfully discovered and characterized. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the formation of cocrystals rather than salts, and the possible hydrogen bonding patterns were analyzed through molecular surface electrostatic potential calculations. The in vitro and in vivo evaluations indicate that all of the cocrystals demonstrate significantly improved dissolution performance, oral absorption and tabletability compared to pure OLA. Among them, OLA-FA exhibit sufficient stability and the most increased Cmax and AUC0-24h values that were 11.6 and 6.1 times of free OLA, respectively, which has great potential to be developed into the improved solid preparations of OLA.

Enhancing physical and chemical stability of hygroscopic hydroxytyrosol by cocrystal formation

Hydroxytyrosol (HT) is a natural phenolic compound with potent antioxidant activity extracted from olive trees. It is generally a slightly hydrated viscous liquid at ambient conditions, and it is highly susceptible to oxygen due to the presence of catechol moiety. Although encapsulation technique provides HT in powder form, it does not improve its chemical stability. Herein, we propose an efficient solution to the high hygroscopicity and poor stability of HT. Four cocrystals were first reported, and their intermolecular interactions were analyzed in detail. After cocrystallization, the melting point is increased and the hygroscopicity is significantly decreased. HT cocrystals are thus solid at room temperature. Moreover, hydroxytyrosol cocrystals with betaine (HT-BET) and nicotinamide (HT-NIC) demonstrate superior chemical stability than pure HT, olive extract, and HT encapsulation material. Therefore, cocrystallization can be considered as a promising approach to overcome the application obstacles of HT.

Optimized solubility and bioavailability of genistein based on cocrystal engineering

With various potential health-promoting bioactivities, genistein has great prospects in treatment of a series of complex diseases and metabolic syndromes such as cancer, diabetes, cardiovascular diseases, menopausal symptoms and so on. However, poor solubility and unsatisfactory bioavailability seriously limits its clinical application and market development. To optimize the solubility and bioavailability of genistein, the cocrystal of genistein and piperazine was prepared by grinding assisted with solvent based on the concept of cocrystal engineering. Using a series of analytical techniques including single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis, the cocrystal was characterized and confirmed. Then, structure analysis on the basis of theoretical calculation and a series of evaluation on the stability, dissolution and bioavailability were carried out. The results indicated that the cocrystal of genistein and piperazine improved the solubility and bioavailability of genistein. Compared with the previous studies on the cocrystal of genistein, this is a systematic and comprehensive investigation from the aspects of preparation, characterization, structural analysis, stability, solubility and bioavailability evaluation. As a simple, efficient and green approach, cocrystal engineering can pave a new path to optimize the pharmaceutical properties of natural products for successful drug formulation and delivery.

In Situ Cocrystallization via Spray Drying with Polymer as a Strategy to Prevent Cocrystal Dissociation

The aim of the present study was to investigate how different polymers affect the dissociation of cocrystals prepared by co-spray-drying active pharmaceutical ingredient (API), coformer, and polymer. Diclofenac acid-l-proline cocrystal (DPCC) was selected in this study as a model cocrystal due to its previously reported poor physical stability in a high-humidity environment. Polymers investigated include polyvinylpyrrolidone (PVP), poly(1-vinylpyrrolidone-co-vinyl acetate) (PVPVA), hydroxypropyl methyl cellulose, hydroxypropylmethylcellulose acetate succinate, ethyl cellulose, and Eudragit L-100. Terahertz Raman spectroscopy (THz Raman) and powder X-ray diffraction (PXRD) were used to monitor the cocrystal dissociation rate in a high-humidity environment. A Raman probe was used in situ to monitor the extent of the dissociation of DPCC and DPCC in crystalline solid dispersions (CSDs) with polymer when exposed to pH 6.8 phosphate buffer and water. The solubility of DPCC and solid dispersions of DPCC in pH 6.8 phosphate buffer and water was also measured. The dissociation of DPCC was water-mediated, and more than 60% of DPCC dissociated in 18 h at 40 °C and 95% RH. Interestingly, the physical stability of the cocrystal was effectively improved by producing CSDs with polymers. The inclusion of just 1 wt % polymer in a CSD with DPCC protected the cocrystal from dissociation over 18 h under the same conditions. Furthermore, the CSD with PVPVA was still partially stable, and the CSD with PVP was stable (undissociated) after 7 days. The superior stability of DPCC in CSDs with PVP and PVPVA was also demonstrated when systems were exposed to water or pH 6.8 phosphate buffer and resulted in higher dynamic solubility of the CSDs compared to DPCC alone. The improvement in physical stability of the cocrystal in CSDs was thought to be due to an efficient mixing between polymer and cocrystal at the molecular level provided by spray drying and in situ gelling of polymer. It is hypothesized that polymer chains could undergo gelling in situ and form a physical barrier, preventing cocrystal interaction with water, which contributes to slowing down the water-mediated dissociation.

Mechanochemical Mediated Coexistence of B←N Coordination and Hydrogen Bonding

Mechanochemistry afforded a photoactive cocrystal via coexisting (B)O-H⋅⋅⋅N hydrogen bonds and B←N coordination. Specifically, solvent-free mechanochemical ball mill grinding and liquid-assisted grinding of a boronic acid and an alkene resulted in mixtures of hydrogen-bonded and coordinated complexes akin to mixtures of noncovalent complexes that can be obtained in solution in equilibria processes. The alkenes of the hydrogen-bonded assembly undergo an intermolecular [2+2] photodimerization in quantitative conversion, effectively reporting the outcome of the self-assembly processes. Our results suggest that interplay involving noncovalent bonds subjected to mechanochemical conditions can lead to functional solids where, in the current case, the structure composed of the weaker hydrogen bonding interactions predominates.

Norfloxacin Cocrystals: Mechanochemical Synthesis and Scale-up Viability Through Solubility Studies

Cocrystals are recognized as one of the most efficient approaches to improve aqueous solubility of Biopharmaceutical Classification System, BCS, classes II and IV drugs. Cocrystal discovery and the establishment of experimental conditions suitable for scale-up purposes are some of the main challenges in cocrystal investigation. In this work, the investigation of mechanochemical synthesis of norfloxacin cocrystals with picolinic and isonicotinic acids is performed, leading to the discovery of two new cocrystals of this important BCS class IV antibiotic, which were characterized through thermal, spectral and diffractometric analysis. Norfloxacin apparent aqueous solubility using the cocrystals is also presented, with higher values being obtained for all the investigated systems when compared to the pure drug. Norfloxacin has 3 polymorphs and several solvents/hydrates, which represents a challenge for obtaining pure cocrystal forms from solvent crystallization. This challenge was successfully overcome in this work, as experimental conditions to obtain the pure cocrystals (the new ones and also norfloxacin-nicotinic acid and norfloxacin-saccharin) were established using Crystal16 equipment. This is a crucial step to envisage future scale-up procedures and therefore a valuable information for the pharmaceutical industry.

Overcoming the Hydrophobic Nature of Zinc Phenylacetate Through Co-Crystallization with Isonicotinamide

Zinc phenylacetate (Zn-PA), a substitute for sodium phenylacetate as an ammonia-scavenging drug is hydrophobic, which poses problems for drug dissolution and solubility. We were able to co-crystallize the zinc phenylacetate with isonicotinamide (INAM) and produce a novel crystalline compound (Zn-PA-INAM). The single crystal of this new crystal was obtained, and its structure is reported here for the first time. Zn-PA-INAM was characterized computationally by ab initio, Hirshfeld calculations, CLP-PIXEL lattice energy calculation, and BFDH morphology analysis, and experimentally by PXRD, Sc-XRD, FTIR, DSC, and TGA analyses. Structural and vibrational analyses showed a major modification in intermolecular interaction of Zn-PA-INAM compared to Zn-PA. The dispersion-based pi-stacking in Zn-PA is replaced by coulomb-polarization effect of hydrogen bonds. As a result, Zn-PA-INAM is hydrophilic, improving the wettability and powder dissolution of the target compound in an aqueous solution. Morphology analysis revealed, unlike Zn-PA, Zn-PA-INAM has polar groups exposed on its prominent crystalline faces, reducing the hydrophobicity of the crystal. The shift in average water droplet contact angle from 128.1° (Zn-PA) to 27.1° (Zn-PA-INAM) is strong evidence of a marked decrease in hydrophobicity of the target compound. Finally, HPLC was used to obtain the dissolution profile and solubility of Zn-PA-INAM compared to Zn-PA.

A critical review of Roxadustat formulations, solid state studies, and analytical methodology

This review aims to collate information about the analytical methodologies, bioanalytical methodologies, pharmaceutical formulations, solid-state studies, and the current and future market scenario for a relatively new class of drugs, Roxadustat. Roxadustat is a hypoxia-inducible factor propyl hydroxylase inhibitor that significantly increases blood hemoglobin via the action of transcriptional activator HIF. As the molecule has a promising role in stimulating erythropoiesis, it is considered an ideal therapeutic agent for patients with anemia. In the current review, an attempt has been made to compile the pharmacological, pharmacokinetic, and pharmacodynamic characteristics of Roxadustat and systematically present product development data. This drug has several polymorphs of cocrystal, co-former, and salt, which have been explained in detail in the current work. The comprehensive review summarizes all the chromatographic methods and is presented in table form. This review has extensively covered Liquid chromatography-tandem mass spectrometry methods used to analyze Roxadustat in the biological matrix. The literature needs more data on forced degradation study, impurity profiling, gas chromatography, analytical methods for assay, dissolution, and different formulation aspects of Roxadustat.

First cocrystal of esculetin: simultaneously optimized in vitro/vivo properties and antioxidant effect

Esculetin (ELT) is one of the best-known and simplest coumarins with powerful natural antioxidant effects but insoluble and difficult to absorb. In order to overcome the problems, cocrystal engineering was first applied to ELT in this paper. Nicotinamide (NAM) was selected as the coformer for its excellent water solubility and potential synergistic antioxidant effect with ELT. The structure of the ELT-NAM cocrystal was successfully prepared and characterized by IR, SCXRD, PXRD, and DSC-TG. Furthermore, the in vitro/vivo properties and antioxidant effects of the cocrystal were adequately studied. The results highlight that the ELT obtained tremendous improvements in water solubility and bioavailability after cocrystal formation. Meanwhile, the synergistic enhancement of ELT with NAM in antioxidant effect was demonstrated by the DPPH assay. Ultimately, the simultaneously optimized in vitro/vivo properties and antioxidant activity of the cocrystal created an improved practical effect of hepatoprotective in rat experiments. The investigation is significant for developing coumarin drugs represented by ELT.

Synthesis of the first remdesivir cocrystal: design, characterization, and therapeutic potential for pulmonary delivery

While cocrystal engineering is an emerging formulation strategy to overcome drug delivery challenges, its therapeutic potential in non-oral applications remains not thoroughly explored. We herein report for the first time the successful synthesis of a cocrystal for remdesivir (RDV), an antiviral drug with broad-spectrum activities against RNA viruses. The RDV cocrystal was prepared with salicylic acid (SA) via combined liquid-assisted grinding (LAG) and thermal annealing. Formation of RDV-SA was found to be a thermally activated process, where annealing at high temperature after grinding was a prerequisite to facilitate the cocrystal growth from an amorphous intermediate, rendering it elusive under ambient preparing conditions. Through powder X-ray analysis with Rietveld refinement, the three-dimensional molecular structure of RDV-SA was resolved. The thermally annealed RDV-SA produced by LAG crystalized in a non-centrosymmetric monoclinic space group P2₁ with a unit cell volume of 1826.53(17) ų, accommodating one pair of RDV and SA molecules in the asymmetric unit. The cocrystal formation was also characterized by differential scanning calorimetry, solid-state nuclear magnetic resonance, and Fourier-transform infrared spectroscopy. RDV-SA was further developed as inhaled dry powders by spray drying for potential COVID-19 therapy. The optimized RDV-SA dry powders exhibited a mass median aerodynamic diameter of 4.33 ± 0.2 μm and fine particle fraction of 41.39 ± 4.25 %, indicating the suitability for pulmonary delivery. Compared with the raw RDV, RDV-SA displayed a 15.43-fold higher fraction of release in simulated lung fluid at 120 min (p =0.0003). RDV-SA was safe in A549 cells without any in vitro cytotoxicity observed in the RDV concentration from 0.05 to 10 µM.

Mechanistic Study on Transformation of Coamorphous Baicalein-Nicotinamide to Its Cocrystal Form

Recently, coamorphization and cocrystal technologies are of particular interest in the pharmaceutical industry due to their ability to improve the solubility/dissolution and bioavailability of poorly water-soluble drugs, while the coamorphous system often tends to convert into the stable crystalline form usually crystalline physical mixture of each component during formulation preparation or storage. In this paper, BCS II drug baicalein (BAI) along with nicotinamide (NIC) were prepared into a single homogeneous coamorphous system with a single transition temperature at 42.5 °C. Interestingly, instead of the physical mixture of crystalline BAI and NIC, coamorphous BAI-NIC would transform to its cocrystal form under stress of temperature and humidity. The transformation rate under isothermal condition was temperature-dependent, since the crystallinity of the cocrystal enhanced as the temperature increased. Further mechanic studies showed the activation energy for the transformation under non-isothermal condition was calculated to be 184.52 kJ/mol. Additionally, water vapor sorption tests with further solid characterizations indicated the transformation was faster under higher humidity condition due to the faster nucleation process of cocrystal BAI-NIC. This research not only discovered the mechanism of transformation from coamorphous BAI-NIC to cocrystal form, but also provided an unusual method for cocrystal preparation from its coamorphous form.

Dissolution Profiles of Carbamazepine Cocrystals with Cis-Trans Isomeric Coformers

PURPOSE

The purpose of the present study was to investigate the dissolution profiles of cocrystals with cis-trans isomeric coformers. Previously, the carbamazepine (CBZ) cocrystals with even-carbon dicarboxylic acids showed higher supersaturation than those with odd-carbon ones, attributed to particle surface solution-mediated phase transformation (PS-SMPT) to CBZ dihydrate (CBZ DH). However, it has been unknown whether this odd-even pattern holds for cis-trans isomeric coformers.

METHOD

CBZ cocrystals with maleic acid (MLE) and fumaric acid (FUM) (CBZ-FUM anhydrate (CBZ-FUM AH) and monohydrate (CBZ-FUM H₂O)) were employed as model cocrystals. Hydroxypropyl　methylcellulose (HPMC), polyvinylpyrrolidone, and polyethylene glycol 6000 (PEG) were used as precipitation inhibitors. Dissolution tests were performed under a non-sink condition. Residual particles were analyzed by powder X-ray diffraction, differential scanning calorimetry, polarized light microscope, and scanning electron microscope.

RESULTS

All cocrystals showed little supersaturation in the absence of a polymer. In 0.1% HPMC, CBZ-FUM AH showed significant supersaturation, whereas CBZ-MLE and CBZ-FUM H₂O did not for the first two hours. HPMC reduced the initial dissolution rate of CBZ-MLE and CBZ-FUM H₂O while inducing the highest supersaturation among the polymers after 96 h. The particle surface changed from a smooth plane to a striped pattern, but little or no CBZ DH was detected.

CONCLUSION

The cocrystals with cis-trans isomeric coformers showed different dissolution profiles. HPMC increased the dissolution rate of CBZ-FUM AH by inhibiting PS-SMPT but reduced the dissolution rate of CBZ-MLE and CBZ-FUM H₂O without inducing PS-SMPT. The striped pattern was suggested to be due to surface etching rather than PS-SMPT.

Rucaparib cocrystal: Improved solubility and bioavailability over camsylate

Rucaparib (Ruc) is a drug used to treat advanced ovarian cancer associated with deleterious BRCA mutations. Its commercial form, the camsylate salt (Ruc-Cam), suffers from poor aqueous solubility and thus causes low and erratic oral bioavailability. In this work, we aimed to improve the oral exposure of Ruc through cocrystallization. Liquid-assisted grinding, slurry, and solvent evaporation methods were employed to prepare new solid forms of Ruc. Cocrystals of rucaparib-theophylline monohydrate (Ruc-Thp MH), rucaparib-maltol (Ruc-Mal), and rucaparib-ethyl maltol (Ruc-Emal) were obtained. Powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and dynamic vapor sorption were utilized to characterize these multi-component systems. All cocrystals dissolve faster than Ruc-Cam at pH 2.0 and 4.5, and Ruc-Thp MH displays the highest apparent solubility in pH 4.5 and 6.8 buffers. Pharmacokinetic studies in rats show that Ruc-Thp MH exhibits 2.4 times the C_max and 1.4 times the AUC_0-24h at a single dose compared with Ruc-Cam. The enhanced solubility and bioavailability of Ruc-Thp MH showcase the power of cocrystallization in addressing absorption issues in drug development.

Single Crystalline, Non-stoichiometric Cocrystals of Hydrogen-Bonded Organic Frameworks

Porous frameworks composed of non-stoichiometrically mixed multicomponent molecules attract much attention from a functional viewpoint. However, their designed preparation and precise structural characterization remain challenging. Herein, we demonstrate that cocrystallization of tetrakis(4-carboxyphenyl)hexahydropyrene and pyrene derivatives (CP-Hp and CP-Py, respectively) yields non-stoichiometric mixed frameworks through networking via hydrogen bonding. The composition ratio of CP-Hp and CP-Py in the framework was determined by single crystalline X-ray crystallographic analysis, indicating that the mixed frameworks were formed over a wide range of composition ratios. Furthermore, microscopic Raman spectroscopy on the single crystal indicates that the components are not uniformly distributed such as ideal solid solution, but are done gradationally or inhomogeneously.

Inhibiting Sublimation of Thymol by Cocrystallization

A thymol:4,4'-dipyridyl (2:1) cocrystal (Form I) is reported to suppress thymol sublimation. The cocrystal was prepared via solution-mediated phase transformation and its structure is sustained by O-H (phenol) ··· N (pyridyl) hydrogen bonds between two individual components. A cocrystal polymorph (Form II) was formed via solid state transformation or via vapor phase upon heating. Using gravimetry analysis, it was demonstrated that cocrystal Form I decreased the sublimation rate of thymol by 38-fold. This study demonstrates that cocrystallization is an effective approach to reduce vapor pressure and sublimation of solids, thus achieving odor-masking.

Precisely Tailoring Heterometallic Polyoxotitanium Clusters for the Efficient and Selective Photocatalytic Oxidation of Hydrocarbons

Photocatalysis is a promising yet challenging approach for the selective oxidation of hydrocarbons to valuable oxygenated chemicals with O₂ under mild conditions. In this work, we report an atomically precise material model to address this challenge. The key to our solution is the rational incorporation of Fe species into polyoxotitanium cluster to form a heterometallic Ti₄ Fe₁ cocrystal. This newly designed cocrystal cluster, which well governs the energy and charge transfer as evidenced by spectroscopic characterizations and theoretical calculations, enables the synergistic process involving C(sp³ )-H bond activation by photogenerated holes and further reactions by singlet oxygen (¹ O₂ ). Remarkably, the cocrystal Ti₄ Fe₁ cluster achieves efficient and selective oxidation of hydrocarbons (C₅ to C₁₆ ) into aldehydes and ketones with a conversion rate up to 12 860 μmol g^-1  h^-1 , 5 times higher than that of Fe-doped Ti₃ Fe₁ cluster. This work provides insights into photocatalyst design at atomic level enabling synergistic catalysis.

Gefitinib-resveratrol Cocrystal with Optimized Performance in Dissolution and Stability

Gefitinib (GEF) is an anti-tumor oral solid formulation with a superior advantage for lung tumors. However, it has poor aqueous solubility which limits its utility in vivo. Herein, a novel cocrystal (GEF-RES) assembled by GEF and RES (Resveratrol) has been successfully prepared and comprehensively characterized by differential scanning calorimetry, thermogravimetric analysis, Raman spectroscopy and powder X-ray diffraction. A single-crystal structure of the GEF-RES cocrystal was solved and illustrated in detail. In aqueous hydrochloric acid, the GEF-RES cocrystal showed that the maximum concentration of GEF was slightly higher than that of raw GEF. Furthermore, the thermal and physical stability of the GEF-RES cocrystal were also evaluated in this paper. The enhanced solubility and excellent solid-state stability results may provide new potential to the application of key GEF in clinical.

Glibenclamide - Malonic Acid Cocrystal with an Enhanced Solubility and Bioavailability

OBJECTIVE

The objective of the work is to enhance the solubility, dissolution and pharmacokinetic properties of Glibenclamide (GLB) via cocrystallization technique. Significance: Glibenclamide (GLB) is an oral hypoglycemic agent used for treating non-insulin-dependent (type II) diabetes mellitus. It exhibits poor aqueous solubility and oral bioavailability, thereby compromising its therapeutic effect. Therefore, utilizing cocrystal approach for enhancing the solubility will modulate the physicochemical properties of GLB without altering its molecular structure.

METHODS

Cocrystal was prepared by solution crystallization method using coformer malonic acid. The cocrystal was characterized by Differential Scanning Calorimetry (DSC), Powder X-ray Diffraction (PXRD) and Fourier Transform Infrared (FT-IR) studies. The prepared cocrystal was subjected to solubility, in vitro dissolution, and pharmacokinetic studies.

RESULTS

The DSC endotherms, PXRD patterns and the FT-IR spectra of the cocrystal established the formation of a cocrystal. The formation of eutectic mixture was refuted upon comparing the DSC endotherm and PXRD pattern of the cocrystal with that of the physical mixture. GLB showed a two-fold enhancement in solubility and a significant improvement in the rate of dissolution (p < 0.05, Independent t-test) after cocrystallization. The pharmacokinetic parameters on male Sprague Drawly rats showed 1.45 enhancement in AUC _0-24 and 1.36 -fold enhancement in the C_max of GLB as compared to the pure drug.

CONCLUSION

These findings demonstrate that cocrystallization technique was able to tailor the solubility and dissolution profile of GLB leading to an enhanced pharmacokinetic property.

A novel cocrystal of metformin hydrochloride with citric acid: Systematic synthesis and computational simulation

Pharmaceutical cocrystals have matured into an effective technique for tuning the physicochemical and mechanical properties of drugs in solid form simultaneously. Herein, in order to provide a novel cocrystal form of oral medicine metformin hydrochloride (MH), citric acid (CA) was selected as an efficient ligand after screening a variety of inorganic and organic acids. Thus, based on the principle of crystal engineering, we report a novel cocrystal: metformin hydrochloride - citric acid (MHCA) after the systematic screening, which was experimentally proved to be constituted with 1:1 stoichiometry. Compared with pure MH, MHCA has been proved higher solubility in water, methanol, and ethanol from 283.15 to 313.15 K. Through single-crystal X-ray diffraction (SC-XRD), the particular molecular structure of MHCA has been determined as the orthorhombic system and Pbca space group. Besides, the binding model of MH-CA was built for investigating the binding energy and stability between two components at 278, 298, and 318 K, which were found to be essential for the prediction and analysis of cocrystals. The contribution of different intermolecular interactions and the strength of molecular packing in the cocrystal also have been investigated by Hirshfeld surface analysis. It was found that the cocrystal structure was mainly stabilized by intermolecular hydrogen bonds existing as N-H···O between components, which indicated that the diffusion-combination trend of molecules enhanced the regular array of cocrystal. The results revealed that the molecules of MH and CA formed supramolecular cocrystals mainly induced by hydrogen bonds after passive contacts, such as co-crystallization or grind.

Cocrystals of tuberculosis antibiotics: Challenges and missed opportunities

Cocrystals have been extensively used to improve the physicochemical properties and bioavailability of active pharmaceutical ingredients. Cocrystals of anti-tuberculosis medications are among those commonly reported. This review provides a summary of the tuberculosis antibiotic cocrystals reported in the literature, providing the main results on current tuberculosis medications utilized in cocrystals. Moreover, anti-tuberculosis cocrystals limitations and advantages are described, including evidence for enhanced solubility, stability and effect. Opportunities to enhance anti-tuberculosis medications and fixed dose combinations using cocrystals are given. Several cocrystal pairs are suggested to enhance the effectiveness of anti-tuberculosis drugs.

Azilsartan-nicotinamide cocrystal: Preparation, characterization and in vitro / vivo evaluation

Azilsartan (AZL) is an angiotensin II receptor antagonist, which is mainly used for the treatment of hypertension. AZL has the advantages of high selectivity, hypotensive effect, protection of cardiovascular and cerebrovascular diseases. In order to improve the water solubility of AZL and its bioavailability, AZL -nicotinamide (NA) cocrystal was prepared by mechanical ball milling, and the effect of ball milling conditions on cocrystal preparation were studied. AZL-NA cocrystal was identified and characterized by powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy and Fourier transform infrared spectrometry. The results showed that AZL-NA cocrystal with the molar ratio of 1:2 was successfully prepared. And the optimum ball milling condition was milling speed of 300 rpm, milling time of 50 min, the solvent was ethanol/acetonitrile (1:1, v/v), and the solvent dosage (η) was 0.8 μL/mg. The results of solubility tests showed that the solubility of AZL in the cocrystal was 3.39 times higher than the pure drug at 24 h. And the results of vitro dissolution tests showed that the cumulative dissolution of AZL in 2 h was about 10%. While distilled water, pH 1.2 and pH 4.5 acid or buffered solutions and pH 6.8 buffer phosphate salt solution was used as the dissolution medium, the cumulative dissolution of AZL in cocrystal reached 50%, 35%, 55% and 90%, respectively, showing obvious improvement of dissolution. In addition, the accelerated stability tests showed that the AZL-NA cocrystal had good chemical stability. And the pharmacokinetic results showed that AZL-NA cocrystal could significantly improve the bioavailability of AZL.

To what extent do bond length and angle govern the 13C and 1H NMR response to weak CH⋯O hydrogen bonds? A case study of caffeine and theophylline cocrystals

Weak hydrogen bonds are important structure-directing elements in supramolecular chemistry and biochemistry. We consider here weak CH⋯O hydrogen bonds in a series of cocrystals of theophylline and caffeine and assess to what extent the CH⋯O distance and angle govern the observed ¹³C and ¹H isotropic chemical shifts. Gauge-including projector-augmented wave density functional theory (GIPAW DFT) calculations consistently predict a decrease in the ¹³C and ¹H magnetic shielding constants upon hydrogen bond formation on the order of 2-5 ppm (¹³C) and 1-2 ppm (¹H). These trends are reproduced using the machine-learning approach implemented in ShiftML. Experimental ¹³C and ¹H chemical shifts obtained for powdered samples using one-dimensional NMR spectroscopy as well as heteronuclear correlation (HETCOR) spectroscopy correlate well with the GIPAW DFT results. However, the experimental ¹³C NMR response only correlates moderately well with the hydrogen bond length and angle, while the experimental ¹H chemical shifts only show very weak correlations to these local structural elements. DFT computations on isolated imidazole-formaldehyde models show that the ¹³C and ¹H chemical shifts generally decrease with the C⋯O distance but show no clear dependence on the CH⋯O angle. These results demonstrate that the ¹³C and ¹H response to weak CH⋯O hydrogen bonding is influenced significantly by additional weak contacts within cocrystal heterodimeric units.

Explaining dissolution properties of rivaroxaban cocrystals

The aim of this study was to improve rivaroxaban water-solubility by cocrystal preparation and to understand this process. The screening with water-soluble coformers was performed via both mechanochemical and solution-mediated techniques. Two cocrystals of rivaroxaban with malonic acid and oxalic acid were prepared, and the structure of the cocrystal with oxalic acid was solved. Both cocrystals exhibit improved dissolution properties. The mechanism of the supersaturation maintenance was studied by in-situ Raman spectroscopy. The transformation into rivaroxaban dihydrate was identified as the critical step in the improved dissolution properties of both cocrystals. Moreover, the transformation kinetics and solubilization effects of the coformers were identified as responsible for the differences in the dissolution behavior of the cocrystals. In-vivo experiments proved that the use of cocrystal instead of form I of free API helped to increase the bioavailability ofrivaroxaban.

Preparation of a new component group of Ginkgo biloba leaves and investigation of the antihypertensive effects in spontaneously hypertensive rats

Ginkgo (Ginkgo biloba L.) is a traditional economic tree species in China. Ginkgo biloba extract (GBE) is widely used in combination to treat hypertension and complications in clinical practice. However, the antihypertensive effect of GBE alone is weak and it is also difficult to study the mechanism because of its complex composition. This study was to prepare a new component group of Ginkgo biloba leaves (GBLCG) with clear chemical structures, and to investigate its effect on reducing blood pressure and improving myocardial hypertrophy in spontaneously hypertensive rats with GBE and amlodipine as positive controls. The results showed that total flavonoid aglycones (TFAs) of GBLCG was mainly composed of quercetin (QCT), kaempferol (KMF) and isorhamnetin (ISR); Total terpenoid lactones (TTLs) of GBLCG might be a novel cocrystal composed of Ginkgolide A (GA), Ginkgolide B (GB) Ginkgolide C (GC), Ginkgolide J (GJ) and bilobalide (BB). The hypotensive activity of GBLCG (4.4 mg/kg) group was better than that of GBE group (p < 0.05), and the effect of improving myocardial hypertrophy was better than that of amlodipine besylate group (p < 0.01). GBLCG might reduce blood pressure and improve myocardial hypertrophy by promoting the synthesis and release of NO in endothelial cells, reducing oxidative stress, inhibiting platelet aggregation and promoting lesion circulation. Eventually, we hope to introduce GBLCG as a new drug for hypertension.

A Calix[3]acridan-Based Host-Guest Cocrystal Exhibiting Efficient Thermally Activated Delayed Fluorescence

A supramolecular strategy to construct thermally activated delayed fluorescence (TADF) materials through host-guest charge transfer interactions was proposed. Consequently, a new class of macrocycle namely calix[3]acridan was conveniently synthesized in 90 % yield. The host-guest cocrystal formed by calix[3]acridan and 1,2-dicyanobenzene exhibited efficient TADF properties due to intense intermolecular charge transfer interactions. Moreover, the spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital resulted in a very small singlet-triplet energy gap of 0.014 eV and hence guaranteed an efficient reverse intersystem crossing for TADF. Especially, a high photoluminescence quantum yield of 70 % was achieved, and it represents the highest value among the reported intermolecular donor-acceptor TADF materials.

Novel dapagliflozin di-L-proline cocrystal-loaded tablet: Preparation, physicochemical characterization, and pharmacokinetics in beagle dogs and mini-pigs

Dapagliflozin base and a commercial dapagliflozin propanediol hydrate cocrystal (DPF-PDHC) were highly hygroscopic and thermally unstable. In this study, to address this limitation, we prepared a novel dapagliflozin di-L-proline cocrystal (DPF-LPC) and evaluated its physicochemical characterization compared with DPF-PDHC. After the preparation of the DPF-LPC-loaded tablet, its dissolution, stability and bioequivalence in beagle dogs and mini-pigs were assessed. DPF-LPC was well prepared with a dapagliflozin base and L-proline in a molar ratio of 1:2. Similar to DPF-PDHC, DPF-LPC was highly lipophilic and crystalline in nature. However, these two cocrystals exhibited different melting points and crystalline structures, indicating their different cocrystal forms. Moreover, DPF-LPC exhibited less hygroscopicity and lower water content than DPF-PDHC. The DPF-LPC-loaded tablet composed of DPF-LPC, Comprecel M102, lactose monohydrate, crospovidone, magnesium stearate, and Opadry (coating) at a weight ratio of 15.6:104.4:100.0:8.0:2.0:7.0, was dissolution-equivalent to the commercial tablet. Moreover, it provided lower impurities than the commercial tablet, indicating its better stability. In the two animals, there were no significant differences in the plasma concentrations, AUC, C_max, and T_max values, suggesting that they were bioequivalent. Therefore, the novel DPF-LPC-loaded tablet with excellent stability and bioequivalence may be used as a potential alternative to the commercial DPF-PDHC-loaded tablet.

Simultaneous improvement of physical stability, dissolution, bioavailability, and antithrombus efficacy of Aspirin and Ligustrazine through cocrystallization

A novel 1:1 cocrystal between two cardiovascular drugs, aspirin (ASA) and ligustrazine (tetramethylpyrazine, TMP) has been synthesized and characterized. The structure of this drug-drug cocrystal, ASA-TMP, was determined using single crystal X-ray crystallography. The ASA-TMP cocrystal exhibits a significantly reduced sublimation tendency than TMP. Importantly, cocrystallization simultaneously improves bioavailability of both parent drugs. This suggests the possibility of developing a more effective antithrombosis drug therapy given the synergistic pharmacological effects of the two parent drugs.

Curcumin and n-acetylcysteine cocrystal produced with supercritical solvent: characterization, solubility, and preclinical evaluation of antinociceptive and anti-inflammatory activities

Curcumin presents a promising anti-inflammatory potential, but its low water-solubility and bioavailability hinder its application. In this sense, cocrystallization represents a tool for improving physicochemical properties, solubility, permeability, and bioavailability of new drug candidates. Thus, the aim of this work was to produce curcumin cocrystals (with n-acetylcysteine as coformer, which possesses anti-inflammatory and antioxidant activities), by the anti-solvent gas technique using supercritical carbon dioxide, and to test its antinociceptive and anti-inflammatory potential. The cocrystal was characterized by differential scanning calorimetry, powder X-ray diffraction and scanning electron microscopy. The cocrystal solubility and antichemotaxic activity were also assessed in vitro. Antinociceptive and anti-inflammatory activities were carried out in vivo using the acetic acid-induced abdominal writhing and carrageenan-induced paw oedema assays in mice. The results demonstrated the formation of a new crystalline structure, thereby confirming the successful formation of the cocrystal. The higher solubility of the cocrystal compared to pure curcumin was verified in acidic and neutral pH, and the cocrystal inhibited the chemotaxis of neutrophils in vitro. In vivo assays showed that cocrystal presents increased antinociceptive and anti-inflammatory potency when compared to pure curcumin, which could be related to an improvement in its bioavailability.

Improving the dissolution behaviors and bioavailability of abiraterone acetate via multicomponent crystal forms

Abiraterone acetate (ABA), the first-line drug for the treatment of metastatic castration resistant prostate cancer (mCRPC), is administered at a high daily dosage of 1000 mg due to its poor solubility, and its fasted absolute oral bioavailability is estimated to be less than 10%. In this work we have focused on developing multicomponent forms with improved dissolution behaviors and bioavailability. Two salts of ABA with malonic acid (ABA-MA) and saccharin (ABA-SAC), and five cocrystals with trans-aconitic acid (ABA-TAA), 1-hydroxy-2-naphthoic acid (ABA-1HNA), pyrocatechol (ABA-PCA), resorcinol (ABA-RES) and hydroquinone (ABA-HDE) were successfully obtained. Their crystal structures were elucidated by single crystal X-ray diffraction, and these multicomponent forms were fully characterized by powder X-ray diffraction, thermal analysis and Fourier Transform Infrared spectra. Among them, ABA-TAA cocrystal shows substantial enhancements both in the solubility and intrinsic dissolution rates in different buffer solutions. In the meantime, we unexpectedly found the gelation of ABA-MA salt and ABA-SAC salt in pH 2.0 buffer solution. The gel-like materials generated on the surface of drug will suppress the release of ABA. Moreover, in vivo pharmacokinetic study on beagle dogs was conducted for ABA-TAA cocrystal preparation and ABA commercial product, and ABA-TAA cocrystal preparation shows enhanced absorption. These advantages in dissolution behaviors and bioavailability demonstrate the potential of ABA-TAA cocrystal to be a better candidate for the treatment of mCRPC compared with ABA.

The solid state of anti-inflammatory morniflumate diniflumate: A cocrystalline salt

Morniflumate diniflumate, a molecular compound involving niflumic acid and its β-morpholino ethyl ester (morniflumate) in the mole ratio 2:1, is found to crystallize in a triclinic P - 1 space group with a unit-cell volume of 2203.4(5) ų. It is a cocrystal between a morniflumate⁺ niflumate^- salt and a neutral niflumic acid molecule. The co-crystalline salt forms endothermically with a positive excess volume and it melts incongruently at 382.3(8) K. Differential scanning calorimetry executed at heating rates above 20 K⋅min^-1, leads to congruent melting at 387.8(9)K with an enthalpy change of Δ_fusH = 80(2) J g^-1. The rare occurrence that incongruent and congruent melting can be observed for the same cocrystal may be due to the conformational versatility of the niflumic acid molecule and its slow conversion between the different conformations due to weak intramolecular hydrogen bonding.

Solid State Characterization and Dissolution Enhancement of Nevirapine Cocrystals

Purpose: Novel cocrystals of nevirapine (NP) were designed and prepared with salicylamide and 3-hydroxy benzoic acid (3-HBA).

Methods: The cocrystals were prepared by solvent drop grinding method by adding few drops of acetone to enhance the solubility and dissolution. The drug and cocrystals were characterized by differential scanning calorimetry (DSC) and powder x-ray diffraction (PXRD). The solubility of NP, its wet ground form, and cocrystals were investigated at different pH. Moreover, the effect of surfactant on solubility of cocrystals was also studied. Finally, intrinsic dissolution rate (IDR) and stability of cocrystals was examined.

Results: The characterization of cocrystals by DSC and PXRD revealed formation of new solid forms due to changes in thermogram and PXRD pattern. The cocrystal of NP with 3-HBA showed 4.5 folds greater solubility in pH 1.2 buffer and 5.5 folds in 1% Tween 80 as compared to original drug. IDR of cocrystals was higher than the pure drug in 0.1 N hydrochloric acid (HCl). Moreover, cocrystals were found physically stable after 3 months as evident from unchanged IDR.

Conclusion: Hence, the present research indicates the new stable solid forms of NP with improved dissolution rate than pure drug.

Reduced deliquescency of isosorbide by cocrystallization and mechanisms for hygroscopicity

Isosorbide (ISO) is an effective hyperosmotic agent that can be administrated orally and is used as a therapeutic agent for brain pressure drop, glaucoma, and Meniere's disease. However, the critical relative humidity (CRH) of ISO is about 48% RH at 25 °C, and it deliquesces in humid environments. In this study, we attempted to reduce the deliquescence of ISO using cocrystallization and analyze the water adsorption mechanism from the crystal structure. Four new ISO cocrystals with piperazine (PZ), hydrochlorothiazide (HCT), 3,5-dihydroxybenzoic acid (35DHBA), or gallic acid (GA) were identified. The dynamic vapor sorption analyses demonstrated that all the cocrystals showed higher CRHs than the ISO crystal. Although water adsorption below the CRH was observed for all cocrystals, the water molecules adsorbed in the ISO-PZ and ISO-GA cocrystals were lower than those in the ISO crystal. Investigation of the crystal structures suggested that the amount of water adsorbed might be related to the degree of exposure of the ISO hydroxyl groups on the crystal surface. Given the CRH, water adsorption below the CRH, thermal stability, apparent dissolution rate, and toxicity level of the coformer, the ISO-GA cocrystal is the most suitable for preparing a solid formulation of ISO.

Dry and Wet Mechanochemical Synthesis of Piroxicam and Saccharin Co-Crystals and Evaluation by Powder X-Ray Diffraction, Thermal Analysis and Mid- and Near- Infrared Spectroscopy

The purpose of this study is to investigate the effects of dry and wet mechanochemical synthesis on piroxicam (PX) and saccharin (SA) mixtures. For this purpose, PX and SA mixtures prepared by wet mechanochemical processes using three solvents and by dry mechanochemical synthesis were evaluated by mid-and near-infrared spectroscopy, powder X-ray diffraction (PXRD), and differential scanning calorimetry (DSC). The mixtures of wet-type products were transformed into PX/SA 1:1 co-crystals. The effect of the solvent was key to the co-crystallization of PX and SA. The products from the dry process were transformed into the amorphous phase. For the sample of the amorphous mixture, two exothermic peaks due to crystallization were observed in the thermal analysis. Bulk PX was ground for the same number of times for transformation, but was not successfully transformed to the amorphous bulk; the same was observed for SA. It is suggested that the mutual existence of PX and SA promotes mutual amorphization.

A Drug-Drug Cocrystal of Dihydromyricetin and Pentoxifylline

Drug-drug cocrystals, which can regulate physicochemical properties of individual drugs and might produce synergistic therapeutic effects, have drawn growing interest in the pharmaceutical industry. In this study, a novel drug-drug (1:1) cocrystal hydrate of slightly water-soluble dihydromyricetin (DMY) and highly water-soluble pentoxifylline (PTX), DMY-PTX•H₂O (1), was prepared by a slurry method. The single-crystal X-ray diffraction results reveal that the cocrystal is formed through hydrogen-bonding interactions between hydroxyl groups of DMY and four acceptors of PTX. The dynamic vapour sorption results indicate that the cocrystal displays reduced hydrophilicity compared with DMY. It is found that cocrystal formation narrows the solubility difference between two parent drugs. The equilibrium solubility of PTX decreases greatly, while that of DMY increases slightly. As a result, DMY and PTX are synchronously and sustainedly released from the cocrystal. Further, a synergistic anti-cancer effect of the cocrystal DMY-PTX•H₂O (1) on HepG2 cells in vitro at a drug concentration of 100 μM was discovered. This study brings evidence of cocrystallization as a successful approach for synchronous sustained-release of two drugs with substantially different aqueous solubility.

Multicomponent ionic crystals of diltiazem with dicarboxylic acids toward understanding the structural aspects driving the drug-release

Diltiazem (DIL) is a calcium channel blocker antihypertensive drug commonly used in the treatment of cardiovascular disorders. Due to the high solubility and prompt dissolution of the commercial form hydrochloride (DIL-HCl) that is closely related to short elimination drug half-life, this API is known for exhibiting an unfitted pharmacokinetic profile. In an attempt to understand how engineered multicomponent ionic crystals of DIL with dicarboxylic acids can minimize these undesirable biopharmaceutical attributes, herein, we have focused on the development of less soluble and slower dissolving salt/cocrystal forms. By the traditional solvent evaporation method, two hydrated salts of DIL with succinic and oxalic acids (DIL-SUC-H₂O and DIL-OXA-H₂O), and one salt-cocrystal with fumaric acid (DIL-FUM-H₂FUM) were successfully prepared. An in-depth crystallographic description of these new solid forms was conducted through single and powder X-ray diffraction (SCXRD, PXRD), Hirshfeld surface (HS) analysis, energy framework (EF) calculations, Fourier Transform Infrared (FT-IR) spectroscopy, and thermal analysis (TG, DSC, and HSM). Structurally, the inclusion of dicarboxylic acids in the crystal structures provided the formation of 2D-sheet assemblies, where ionic pairs (DIL⁺/anion^-) are associated with each other via H-bonding. Consequently, a substantial lowering in both solubility (16.5-fold) and intrinsic dissolution rate (13.7-fold) of the API has been achieved compared to that of the hydrochloride salt. These findings demonstrate the enormous potential of these solid forms in preparing of novel modified-release pharmaceutical formulations of DIL.

Ketoconazole-p aminobenzoic cocrystal, an improved antimycotic drug formulation, does not induce skin sensitization on the skin of BALBc mice

Fungal infections are a growing global health problem. Therefore, our group has synthetized and characterized an improved antimycotic by co-crystallization of ketoconazole and para-amino benzoic acid, named KET-PABA. The aim was to increase bioavailability, biocompatibility, and efficiency of the parent drug-ketoconazole. Based on our previous results showing the cocrystal improved physical properties, such as stability in suspension, solubility, as well as antimycotic efficiency compared to ketoconazole, the current study investigated the local possible side effects induced on the skin of BALBc mice by the application of KET-PABA cocrystal, in view of a further use as a topically applied antimycotic drug. A specific test (mouse ear-swelling test) was used, combined with the histopathological examination and the measurement of pro and anti-inflammatory cytokines and inflammation mediators. KET-PABA application was safe, without signs of skin sensitization shown by the mouse ear sensitization test, or histopathology. KET-PABA strongly inhibited proinflammatory cytokines such as IL1 α, IL1 β, IL6 and TNF α, and other proinflammatory inducers such as NRF2, compared to vehicle. KET-PABA had no effect on the levels of the anti-inflammatory cytokine IL10, or proinflammatory enzyme COX2 and had minimal effects on the activation of the NF-κB pathway. Overall, KET-PABA application induced no sensitization, moreover, it decreased the skin levels of proinflammatory molecules. The lack of skin sensitization effects on BALBc mice skin along with the inhibition of the proinflammatory markers show a good safety profile for topical applications of KET-PABA and show promise for a further clinical use in the treatment of cutaneous mycosis.

Phase solubility diagrams and energy surface calculations support the solubility enhancement with low hygroscopicity of Bergenin: 4-Aminobenzamide (1: 1) cocrystal

Herein, we reported a new bergenin: 4-aminobenzamide (BGN-4AM) cocrystal with significantly enhanced solubility and low hygroscopicity probed from two aspects such as phase solubility diagrams and theoretical calculations. Compared with anhydrous BGN, BGN-4AM solubilities in water and different buffer solutions (pH = 1.2, 4.5, 6.8) increase significantly. It is noted that BGN-4AM solubility in pH = 6.8 buffer solution presents 32.7 times higher than anhydrous BGN. Interestingly, BGN-4AM (0.31 ± 0.07%) showcases lower hygroscopicity than anhydrous BGN (9.31 ± 0.16%). The predicted and experimental solubilities agree with each other when considering solubility product (K_sp) and solution binding constant (K₁₁) in phase solubility diagrams, indicating the solution complexes formation occurs. Further crystal surface-water interactions and Bravais, Friedel, Donnay-Harker (BFDH) analyses based on Density Functional Theory with dispersion correction (DFT-d) methods support the enhanced solubility. The water probe demonstrates an average interaction energy of -6.48 kcal/mol on the 002 plane of BGN-4AM, and only -5.47 kcal/mol on the 011 plane of BGN monohydrate. The lower lattice energy of BGN-4AM guarantees its lower hygroscopicity than BGN monohydrate. BGN-4AM with enhanced solubility and low hygroscopicity can be a potential candidate for further formulation development.

Molecular cocrystal odyssey to unconventional electronics and photonics

Cocrystal has been discovered and studied for more than 170 years since 1844, while the applications to optoelectronics only begin in the last decade. Several general questions that chemists and materials scientists currently seek to answer are: can we design and control the molecular self-assembly and cocrystal growth, what's the packing-property correlations, as well as how can we improve device parameters for real applications in industry. In this contribution, we review our and other groups' recent advances in the cocrystal research field sequentially including: (1) nucleation and growth mechanisms for selective preparation of cocrystals with different donor/acceptor ratio and morphology; (2) charge transport and electronic devices, particularly field-effect transistor (FET) and photo-response device. We discuss the in-situ single crystal device fabrication method, ambipolar charge transport, and molecular packing-charge separation correlation; (3) photonic and optical property, focusing on optical waveguide, photonic logic computation, and nonlinear optics (NLO). We present unusual optical properties revealed by advanced instruments and general structure-function relations for future study. Importantly, the extensive investigations described herein yield in-depth and detailed understandings of molecular cocrystals, and show that such bi-component material systems together with the developed instrument measurement methodologies have the potential to initiate unconventional electronic and photonic science and technology.

Terahertz spectroscopic characterizations and DFT calculations of indomethacin cocrystals with nicotinamide and saccharin

Co-crystallization is an effective strategy to improve the drug properties such as solubility and stability. However, its thermodynamic backgrounds, especially lattice vibration, haven't been fully understood. In this work, indomethacin (IND) cocrystals formed with nicotinamide (NIC) and saccharin (SAC) are successfully characterized by using terahertz spectroscopy. DFT calculations at PBE-D3 level with and without constrained unit cell are performed to predict the absorption peaks at spectral range. The results suggest that the DFT calculations with constrained unit cell achieve a better agreement with experimental observations. Based on the optimized geometries and calculated phonons, the thermodynamic contributions from lattice vibrations to cocrystal formations are further evaluated. The findings reveal that the vibrational energy plays a comparable role with electronic energy, but has an opposite impact on these two cocrystal formations.

Novel cocrystals of itraconazole: Insights from phase diagrams, formation thermodynamics and solubility

In this work, the cocrystallization approach was applied to itraconazole (ITR), a very slightly soluble triazole antifungal drug, which led to the formation of two new solid forms of ITR with 4-aminobenzoic acid (4AmBA) and 4-hydroxybenzamide (4OHBZA). A thermodynamic analysis of the solid-liquid binary phase diagrams for the (ITR + 4AmBA) and (ITR + 4OHBZA) systems provided conclusive evidence of the cocrystal stoichiometry: 1:1 for the cocrystal with 4-aminobenzoic acid, and 1:2 for the cocrystal with 4-hydroxybenzamide. Powder X-Ray diffraction analysis confirmed the formation of two different polymorphic forms of the [ITR + 4OHBZA] (1:2) cocrystal obtained either through solution or melt crystallization. Cocrystal formation and polymorphic transition processes were investigated in detail by the DSC and HSM methods. The thermodynamic functions of cocrystal formation were estimated from the solubility of the cocrystals and the corresponding solubility of the pure compounds at different temperatures. The combination of ITR and 4OHBZA was found to be more favorable than the reaction between ITR and 4AmBA in terms of both Gibbs energy and enthalpy. The pH-solubility behavior of the cocrystals was investigated at different pH values using eutectic concentrations of the components and the cocrystal solubility advantage was estimated. It was found that the cocrystallization of itraconazole with 4OHBZA and 4AmBA can potentially increase the drug solubility at pH1.2 and 37 °C by 225 and 64 times, respectively. The cocrystal dissolution behavior in biorelevant media was analyzed in terms of C_max, σ_max parameters (the maximum ITR concentration and supersaturation), and AUC (the concentration area under the curve during the dissolution - supersaturation - precipitation process). The cocrystals had similar σ_max values during the dissolution and sustained supersaturation for up to 6 h, which gave them an advantage in the AUC values (13-37 times higher) over the drug. The differences in the dissolution profiles of the cocrystals were rationalized in terms of their dissolution rate values.

Modulation of the powder properties of lamotrigine by crystal forms

The mechanical properties of powders determine the ease of manufacture and ultimately the quality of the oral solid dosage forms. Although poor mechanical properties of an active pharmaceutical ingredient (API) can be mitigated by using suitable excipients in a formulation, the effectiveness of that approach is limited for high dose drugs or multidrug tablets. In this context, improving the mechanical properties of the APIs through solid form optimisation is a good strategy to address such a challenge. This work explores the powder and tableting properties of various lamotrigine (LAM) solid forms with the aim to facilitate direct compression by overcoming the poor tabletability of LAM. The two drug-drug crystals of LAM with nicotinamide and valproic acid demonstrate superior flowability and tabletability over LAM. The improved powder properties are rationalised by structure analysis using energy framework, scanning electron microscopy, and Heckel analysis.