Preparation, characterization, in vitro and in vivo evaluation of metronidazole–gallic acid cocrystal: A combined experimental and theoretical investigation

New Cocrystals of Ligustrazine: Enhancing Hygroscopicity and Stability

Ligustrazine (TMP) is the main active ingredient extracted from Rhizoma Chuanxiong, which is used in the treatment of cardiovascular and cerebrovascular diseases, with the drawback of being unstable and readily sublimated. Cocrystal technology is an effective method to improve the stability of TMP. Three benzoic acid compounds including P-aminobenzoic acid (PABA), 3-Aminobenzoic acid (MABA), and 3,5-Dinitrobenzoic acid (DNBA) were chosen for co-crystallization with TMP. Three novel cocrystals were obtained, including TMP-PABA (1:2), TMP-MABA (1.5:1), and TMP-DNBA (0.5:1). Hygroscopicity was characterized by the dynamic vapor sorption (DVS) method. Three cocrystals significantly improved the hygroscopicity stability, and the mass change in TMP decreased from 25% to 1.64% (TMP-PABA), 0.12% (TMP-MABA), and 0.03% (TMP-DNBA) at 90% relative humidity. The melting points of the three cocrystals were all higher than TMP, among which the TMP-DNBA cocrystal had the highest melting point and showed the best stability in reducing hygroscopicity. Crystal structure analysis shows that the mesh-like structure formed by the O-H⋯N hydrogen bond in the TMP-DNBA cocrystal was the reason for improving the stability of TMP.

Metronidazole Cocrystal Polymorphs with Gallic and Gentisic Acid Accessed through Slurry, Atomization Techniques, and Thermal Methods

In this study, key features of metronidazole (MNZ) cocrystal polymorphs with gallic acid (GAL) and gentisic acid (GNT) were elucidated. Solvent-mediated phase transformation experiments in 30 solvents with varying properties were employed to control the polymorphic behavior of the MNZ cocrystal with GAL. Solvents with relative polarity (RP) values above 0.35 led to cocrystal I°, the thermodynamically stable form. Conversely, solvents with RP values below 0.35 produced cocrystal II, which was found to be only 0.3 kJ mol-1 less stable in enthalpy. The feasibility of electrospraying, including solvent properties and process conditions required, and spray drying techniques to control cocrystal polymorphism was also investigated, and these techniques were found to facilitate exclusive formation of the metastable MNZ-GAL cocrystal II. Additionally, the screening approach resulted in a new, high-temperature polymorph I of the MNZ-GNT cocrystal system, which is enantiotropically related to the already known form II°. The intermolecular energy calculations, as well as the 2D similarity between the MNZ-GAL polymorphs and the 3D similarity between MNZ-GNT polymorphs, rationalized the observed transition behaviors. Furthermore, the evaluation of virtual cocrystal screening techniques identified molecular electrostatic potential calculations as a supportive tool for coformer selection.

Tannic acid-derived selective capture of bacteria from apple juice

Given the enormous burden pathogens pose on human health, rapid capture and removal of bacteria for sterilization or further bacterial detection is essential. Herein, tannic acid-functionalized virus-like Fe₃O₄ (vFe₃O₄-TA) was established for bacterial enrichment. We investigated the ability of vFe₃O₄-TA to capture Gram-negative bacteria (E. coli, S. flex and S. typhi) and Gram-positive bacteria (S. aureus, MRSA and LM), respectively. Compared to the capture efficiency of <15 % for Gram-negative bacteria, vFe₃O₄-TA showed excellent selectivity and efficiency in isolating Gram-positive bacteria with >87 % removal efficiency. GFN-xTB semiempirical quantum chemical calculations revealed that the selective recognition originates from the high affinity between TA and peptidoglycan. Without impacting ingredients, the TA-mediated trapper also shows excellent ability to distinguish Gram-positive bacteria in juice samples. These results are expected to reveal the interaction of TA with bacteria, and inaugurate a potential natural safe tool for food safety control, medical treatment and environmental remediation.

Pharmaceutical Co-crystal of Antiviral Agent Efavirenz with Nicotinamide for the Enhancement of Solubility, Physicochemical Stability, and Oral Bioavailability

The present research work attempted to improve the oral bioavailability of the antiviral drug Efavirenz (EFV) using a pharmaceutical cocrystallization technique. EFV comes under BCS-II and has extremely low water solubility, and results in low oral bioavailability. EFV and nicotinamide (NICO) were selected in a (1:1) stoichiometric ratio and efavirenz nicotinamide cocrystal (ENCOC) was prepared through the liquid-assisted grinding method (LAG). The confirmation of the formation of a new solid phase was done through spectroscopic techniques like Fourier transmission infrared (FTIR), Raman, and ¹³C solid-state nuclear magnetic resonance (¹³C ssNMR). Thermal techniques like differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and hot stage microscopy (HSM) illustrated the thermal behavior and melting patterns of ENCOC, EFV, and NICO. The X-ray powder diffraction (XRPD) confirms the formation of a new crystalline phase in ENCOC. The Morphology was determined through scanning electron microscopy (FESEM). The results of saturated solubility studies and in vitro drug release studies exhibited 8.9-fold enhancement in solubility and 2.56-fold enhancement in percentage cumulative drug release. The percentage drug content of ENCOC was found higher than 97% and cocrystal exhibits excellent accelerated stability. The oral bioavailability of EFV (C_max, 799.08 ng/mL) exhibits significant enhancement after cocrystallization (C_max, 5597.09 ng/mL) than EFV and Efcure®-200 tablet (2896.21 ng/mL). The current work investigates the scalable and cost-effective method for enhancement of physicochemical stability, solubility, and oral bioavailability of an antiviral agent EFV.

Improving the Physicochemical and Biopharmaceutical Properties of Active Pharmaceutical Ingredients Derived from Traditional Chinese Medicine through Cocrystal Engineering

Active pharmaceutical ingredients (APIs) extracted and isolated from traditional Chinese medicines (TCMs) are of interest for drug development due to their wide range of biological activities. However, the overwhelming majority of APIs in TCMs (T-APIs), including flavonoids, terpenoids, alkaloids and phenolic acids, are limited by their poor physicochemical and biopharmaceutical properties, such as solubility, dissolution performance, stability and tabletability for drug development. Cocrystallization of these T-APIs with coformers offers unique advantages to modulate physicochemical properties of these drugs without compromising the therapeutic benefits by non-covalent interactions. This review provides a comprehensive overview of current challenges, applications, and future directions of T-API cocrystals, including cocrystal designs, preparation methods, modifications and corresponding mechanisms of physicochemical and biopharmaceutical properties. Moreover, a variety of studies are presented to elucidate the relationship between the crystal structures of cocrystals and their resulting properties, along with the underlying mechanism for such changes. It is believed that a comprehensive understanding of cocrystal engineering could contribute to the development of more bioactive natural compounds into new drugs.

Reusable Ag@TiO2-Based Photocatalytic Nanocomposite Membranes for Solar Degradation of Contaminants of Emerging Concern

Two significant limitations of using TiO2 nanoparticles for water treatment applications are reduced photocatalytic activity under visible radiation and difficulty recovering the particles after use. In this study, round-shaped Ag@TiO2 nanocomposites with a ≈21 nm diameter and a bandgap energy of 2.8 eV were synthesised by a deposition-precipitation method. These nanocomposites were immobilised into a porous poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) matrix and well-distributed within the pores. The photocatalytic activity of Ag@TiO2/PVDF-HFP against metronidazole (MNZ) under solar radiation was evaluated. Further, an adaptive neuro-fuzzy inference system (ANFIS) was applied to predict the effect of four independent variables, including initial pollutant concentration, pH, light irradiation intensity, and reaction time, on the photocatalytic performance of the composite membrane on MNZ degradation. The 10% Ag@TiO2/PVDF-HFP composite membrane showed a maximum removal efficiency of 100% after 5 h under solar radiation. After three use cycles, this efficiency remained practically constant, demonstrating the membranes' reusability and suitability for water remediation applications.

Revisiting stacking interactions in tetrathiafulvalene and selected derivatives using tight-binding quantum chemical calculations and local coupled-cluster method

The engineering of supramolecular architectures needs accurate descriptions of the intermolecular interactions in crystal structures. Tetrathiafulvalene (TTF) is an effective building block used in the construction of promising functional materials. The parallel packing of the neutral TTF-TTF system was studied previously using the high-level quantum chemical method, advancing it as a valuable model system. The recently developed tight-binding quantum chemical method GFN2-xTB and local coupled-cluster method DLPNO-CCSD(T) were used to investigate the stacking interactions of TTF and selected derivatives deposited in the Cambridge Structural Database. Using the interaction energy of the TTF-TTF dimer calculated at the CCSD(T)/CBS level as the reference, the accuracies of the two methods are investigated. The energy decomposition analysis within the DLPNO-CCSD(T) framework reveals the importance of dispersion interaction in the TTF-related stacking systems. The dispersion interaction density plot vividly shows the magnitude and distribution of the dispersion interaction, providing a revealing insight into the stacking interactions in crystal structures. The results show that the GFN2-xTB and DLPNO-CCSD(T) methods could achieve accuracy at an affordable computational cost, which would be valuable in understanding the nature of parallel stacking in supramolecular systems.

Amino Acids as the Potential Co-Former for Co-Crystal Development: A Review

Co-crystals are one of the most popular ways to modify the physicochemical properties of active pharmaceutical ingredients (API) without changing pharmacological activity through non-covalent interactions with one or more co-formers. A "green method" has recently prompted many researchers to develop solvent-free techniques or minimize solvents for arranging the eco-friendlier process of co-crystallization. Researchers have also been looking for less-risk co-formers that produce the desired API's physicochemical properties. This review purposed to collect the report studies of amino acids as the safe co-former and explored their advantages. Structurally, amino acids are promising co-former candidates as they have functional groups that can form hydrogen bonds and increase stability through zwitterionic moieties, which support strong interactions. The co-crystals and deep eutectic solvent yielded from this natural compound have been proven to improve pharmaceutical performance. For example, l-glutamine could reduce the side effects of mesalamine through an acid-base stabilizing effect in the gastrointestinal fluid. In addition, some amino acids, especially l-proline, enhances API's solubility and absorption in its natural deep eutectic solvent and co-crystals systems. Moreover, some ionic co-crystals of amino acids have also been designed to increase chiral resolution. Therefore, amino acids are safe potential co-formers, which are suitable for improving the physicochemical properties of API and prospective to be developed further in the dosage formula and solid-state syntheses.

Improving the Solubility, Dissolution, and Bioavailability of Metronidazole via Cocrystallization with Ethyl Gallate

Metronidazole (MTZ) is an antibacterial drug widely used for the treatment of protozoan and anaerobic infections in humans and animals. However, its low bioavailability necessitates the frequent administration of a high dose to attain an effective plasma concentration profile for therapy. To reduce the dose of MTZ, we have prepared a new cocrystal between MTZ and ethyl gallate (EG). The solid-state properties of MTZ-EG were characterized using complimentary techniques, including thermal, spectroscopic, microscopic, and X-ray crystallographic methods. The MTZ-EG cocrystal exhibits a higher solubility and faster dissolution than MTZ. The bioavailability of MTZ in rats was increased by 36% when MTZ-EG was used.

Development of Polycaprolactone-Based metronidazole matrices for intravaginal extended drug delivery using a mechanochemically prepared therapeutic deep eutectic system

The engineering of crystalline multi-component drug systems, including cocrystals and salts, is now an established method of modifying the physicochemical properties and dissolution behaviour of an active ingredient. Remarkably, liquid drug systems, including therapeutic ionic liquids and therapeutic deep eutectic solvents (THEDES), remain largely unexplored as an untapped reservoir for drug modification. In this work, the formation of a THEDES containing metronidazole (MET), the preferred first-line treatment for bacterial vaginosis (BV), was explored. The formed THEDES was evaluated for its dissolution behaviour from a simple polycaprolactone (PCL) matrix, in order to achieve an extended release, balanced with an appropriate onset of action, hence offering improved MET intravaginal application. To minimise handling of the liquid THEDES, an end-to-end continuous process that enables feeding of the raw materials in their respective solid forms, and collection of a solidified final formulation is presented. The concurrent THEDES formation and formulation were carried out using a bench scale (approx. 10 g) twin-screw hot melt extruder. The chosen parent reagents have shown sufficiently strong reactivity and resulted in successful and complete conversion to THEDES while in the presence of PCL, during the extrusion process. The formulated THEDES-PCL matrix exhibited significantly improved onset of drug release followed by a controlled delivery of MET over a total 7-day period in SVF, proving itself as a viable alternative to oral therapy.

Color tuning of an active pharmaceutical ingredient through cocrystallization: a case study of a metronidazole–pyrogallol cocrystal

The visual color of antimicrobial drug metronidazole is tuned through cocrystallization with pyrogallol, offering a new modification approach.