The Effect of Solvents on the Crystal Morphology of Isosorbide Mononitrate and Its Molecular Mechanisms

In this work, the modified attachment energy model was used to predict the crystal morphology of isosorbide mononitrate (ISMN) in the dichloromethane (CH2Cl2) solvent system and dichloromethane-n-hexane (CH2Cl2-C6H14) mixed solvent system. The solvent effect can significantly affect the crystal morphology, which can profoundly impact both the drug's physicochemical properties and the subsequent technological treatment process. In addition, the interactions between solvent molecules and crystal faces were investigated using molecular dynamics simulation, and radial distribution function (RDF) analysis was performed to determine the types of interactions. The structural parameter S was introduced to characterize the roughness of each crystal surface; the change in the CH2Cl2 diffusion coefficient before and after the addition of C6H14 was analyzed using mean square displacement (MSD). The calculation results of the modified attachment energy from the two solvent systems revealed that C6H14 could accelerate crystal growth, while the crystal morphology was not greatly affected, which is of some significance as a guide for the industrial crystallization process.

Particle preparation of pharmaceutical compounds using supercritical antisolvent process: current status and future perspectives

The low aqueous solubility and subsequently slow dissolution rate, as well as the poor bioavailability of several active pharmaceutical ingredients (APIs), are major challenges in the pharmaceutical industry. In this review, the particle engineering approaches using supercritical carbon dioxide (SC CO₂) as an antisolvent are critically reviewed. The different SC CO₂-based antisolvent processes, such as the gas antisolvent process (GAS), supercritical antisolvent process (SAS), and a solution-enhanced dispersion system (SEDS), are described. The effect of process parameters such as temperature, pressure, solute concentration, nozzle diameter, SC CO₂ flow rate, solvent type, and solution flow rate on the average particle size, particle size distribution, and particle morphology is discussed from the fundamental perspective of the SAS process. The applications of the SAS process in different formulation approaches such as solid dispersion, polymorphs, cocrystallization, inclusion complexation, and encapsulation to enhance the dissolution rate, solubility, and bioavailability are critically reviewed. This review highlights some areas where the SAS process has not been adequately explored yet. This review will be helpful to researchers working in this area or planning to explore SAS process to particle engineering approaches to tackle the challenge of low solubility and subsequently slow dissolution rate and poor bioavailability.

API co-crystals - Trends in CMC-related aspects of pharmaceutical development beyond solubility

Whereas pharmaceutical co-crystals are widely described as tool to improve solubility and dissolution behavior of poorly soluble drugs, so far less focus has been on their potential role to facilitate pharmaceutical manufacturability. This review summarizes recent developments in co-crystal research regarding new trends in co-crystal preparation routes and control of solid-state material attributes. Also, recent literature was reviewed to assess risks for co-crystals in formulation processes. A growing number of publications suggest that co-crystals show potential to specifically improve mechanical properties such as tabletability and compressibility, which can often be linked to intrinsic features of crystal structure properties. However, such trends must be treated with care, as molecular structures in reported co-crystal studies are not representative in some structural parameters governing also solid-state behavior (smaller molecular weight, more balanced hydrogen bond donor versus acceptor counts) compared to recent market approved small molecule drugs.

Mechanical Activation by Ball Milling as a Strategy to Prepare Highly Soluble Pharmaceutical Formulations in the Form of Co-Amorphous, Co-Crystals, or Polymorphs

Almost half of orally administered active pharmaceutical ingredients (APIs) have low solubility, which affects their bioavailability. In the last two decades, several alternatives have been proposed to modify the crystalline structure of APIs to improve their solubility; these strategies consist of inducing supramolecular structural changes in the active pharmaceutical ingredients, such as the amorphization and preparation of co-crystals or polymorphs. Since many APIs are thermosensitive, non-thermal emerging alternative techniques, such as mechanical activation by milling, have become increasingly common as a preparation method for drug formulations. This review summarizes the recent research in preparing pharmaceutical formulations (co-amorphous, co-crystals, and polymorphs) through ball milling to enhance the physicochemical properties of active pharmaceutical ingredients. This report includes detailed experimental milling conditions (instrumentation, temperature, time, solvent, etc.), as well as solubility, bioavailability, structural, and thermal stability data. The results and description of characterization techniques to determine the structural modifications resulting from transforming a pure crystalline API into a co-crystal, polymorph, or co-amorphous system are presented. Additionally, the characterization methodologies and results of intermolecular interactions induced by mechanical activation are discussed to explain the properties of the pharmaceutical formulations obtained after the ball milling process.

Solid-State and Particle Size Control of Pharmaceutical Cocrystals using Atomization-Based Techniques

Poor bioavailability and aqueous solubility represent a major constraint during the development of new API molecules and can influence the impact of new medicines or halt their approval to the market. Cocrystals offer a novel and competitive advantage over other conventional methods with respect towards the substantial improvement in solubility profiles relative to the single-API crystals. Furthermore, the production of such cocrystals through atomization-based methods allow for greater control, with respect to particle size reduction, to further increase the solubility of the API. Such atomization-based methods include supercritical fluid methods, conventional spray drying and electrohydrodynamic atomization/electrospraying. The influence of process parameters such as solution flow rates, pressure and solution concentration, in controlling the solid-state and final particle size are discussed in this review with respect to atomization-based methods. For the last decade, literature has been attempting to catch-up with new regulatory rulings regarding the classification of cocrystals, due in part to data sparsity. In recent years, there has been an increase in cocrystal publications, specifically employing atomization-based methods. This review considers the benefits to employing atomization-based methods for the generation of pharmaceutical cocrystals, examines the most recent regulatory changes regarding cocrystals and provides an outlook towards the future of this field.

A critical review on the particle generation and other applications of rapid expansion of supercritical solution

The novel particle generation processes of Active Pharmaceutical Ingredient (API)/drug have been extensively explored in recent decades due to their wide-range applications in the pharmaceutical industry. The Rapid Expansion of Supercritical Solutions (RESS) is one of the promising techniques to obtain the fine particles (micro to nano-size) of APIs with narrow particle size distribution (PSD). In RESS, supercritical carbon dioxide (SC CO₂) and API are used as solvent and solute respectively. In this literature survey, the application of RESS in the formation of fine particles is critically reviewed. Solubility of API in SC CO₂ and supersaturation are the key factors in tuning the particle size. The different approaches to model and predict the solubility of API in SC CO₂ are discussed. Then, the effect of process parameters on mean particle size and the particle size distribution are interpreted in the context of solubility and supersaturation. Furthermore, the less-explored applications of RESS in preparation of solid-lipid nanoparticles, liposome, polymorphic conversion, cocrystallization and inclusion complexation are compared with traditional processes. The solubility enhancement of API in SC CO₂ using co-solvent and its applications in particle generation are explored in published literature. The development and modifications in the conventional RESS process to overcome the limitations of RESS are presented. Finally, the perspective on RESS with special attention to its commercial operation is highlighted.

Applications of Supercritical Anti-Solvent Process in Preparation of Solid Multicomponent Systems

Solid multicomponent systems (SMS) are gaining an increasingly important role in the pharmaceutical industry, to improve the physicochemical properties of active pharmaceutical ingredients (APIs). In recent years, various processes have been employed for SMS manufacturing. Control of the particle solid-state properties, such as size, morphology, and crystal form is required to optimize the SMS formulation. By utilizing the unique and tunable properties of supercritical fluids, supercritical anti-solvent (SAS) process holds great promise for the manipulation of the solid-state properties of APIs. The SAS techniques have been developed from batch to continuous mode. Their applications in SMS preparation are summarized in this review. Many pharmaceutical co-crystals and solid dispersions have been successfully produced via the SAS process, where the solid-state properties of APIs can be well designed by controlling the operating parameters. The underlying mechanisms on the manipulation of solid-state properties are discussed, with the help of on-line monitoring and computational techniques. With continuous researching, SAS process will give a large contribution to the scalable and continuous manufacturing of desired SMS in the near future.

Choline-chloride and betaine-based deep eutectic solvents for green extraction of nutraceutical compounds from spent coffee ground

Coffee beans contain several compounds which have shown nutraceutial properties; among them chlorogenic acids (CGAs) are the most studied, have shown nutraceutical properties. These molecules are also present in the waste by-product known as spent coffee grounds (SCG). SCG are generated during the production of coffee drink, whereby roasted, ground coffee beans are heat or steam treated. A HPLC-PDA/ESI-MS method has been developed for the analysis of the most representative CGAs in SCG samples using a green extraction approach based on deep eutectic solvents (DESs). We examined fifteen different DESs based on choline chloride and betaine as hydrogen bond acceptor in combination with different hydrogen bond donors being seven alcohols, two organic acids, one sugar and urea. Fifteen CGAs were detected, identified and quantified for the evaluation of extraction efficiency. A betaine-based DES with triethylene glycol (molar ratio 1:2) was the most effective one at extracting CGAs from SCG also compared to a conventional organic solvent. Thirty percent of water added to DES and sample to solvent ratio 1:15 (g/mL) were selected as the best extraction conditions. The chromatographic method was validated studying LOD, LOQ, retention time and peak area precision, and linearity range. Retention time and peak area repeatability were determined obtaining RSDs values below 0.63 % and 8.51 %, respectively. Inter-day precision was determined obtaining RSDs value below 0.58 % and 8.80 % for retention time and peak area, respectively.

Supercritical carbon dioxide-based technologies for the production of drug nanoparticles/nanocrystals - A comprehensive review

Low drug bioavailability, which is mostly a result of poor aqueous drug solubilities and of inadequate drug dissolution rates, is one of the most significant challenges that pharmaceutical companies are currently facing, since this may limit the therapeutic efficacy of marketed drugs, or even result in the discard of potential highly effective drug candidates during developmental stages. Two of the main approaches that have been implemented in recent years to overcome poor drug solubility/dissolution issues have frequently involved drug particle size reduction (i.e., micronization/nanonization) and/or the modification of some of the physicochemical and structural properties of poorly water soluble drugs. A large number of particle engineering methodologies have been developed, tested, and applied in the synthesis and control of particle size/particle-size distributions, crystallinities, and polymorphic purities of drug micro- and nano-particles/crystals. In recent years pharmaceutical processing using supercritical fluids (SCF), in general, and supercritical carbon dioxide (scCO₂), in particular, have attracted a great attention from the pharmaceutical industry. This is mostly due to the several well-known advantageous technical features of these processes, as well as to other increasingly important subjects for the pharmaceutical industry, namely their "green", sustainable, safe and "environmentally-friendly" intrinsic characteristics. In this work, it is presented a comprehensive state-of-the-art review on scCO₂-based processes focused on the formation and on the control of the physicochemical, structural and morphological properties of amorphous/crystalline pure drug nanoparticles. It is presented and discussed the most relevant scCO₂, scCO₂-based fluids and drug physicochemical properties that are pertinent for the development of successful pharmaceutical products, namely those that are critical in the selection of an adequate scCO₂-based method to produce pure drug nanoparticles/nanocrystals. scCO₂-based nanoparticle formation methodologies are classified in three main families, and in terms of the most important role played by scCO₂ in particle formation processes: as a solvent; as an antisolvent or a co-antisolvent; and as a "high mobility" additive (a solute, a co-solute, or a co-solvent). Specific particle formation methods belonging to each one of these families are presented, discussed and compared. Some selected amorphous/crystalline drug nanoparticles that were prepared by these methods are compiled and presented, namely those studied in the last 10-15 years. A special emphasis is given to the formation of drug cocrystals. It is also discussed the fundamental knowledge and the main mechanisms in which the scCO₂-based particle formation methods rely on, as well as the current status and urgent needs in terms of reliable experimental data and of robust modeling approaches. Other addressed and discussed topics include the currently available and the most adequate physicochemical, morphological and biological characterization methods required for pure drug nanoparticles/nanocrystals, some of the current nanometrology and regulatory issues associated to the use of these methods, as well as some scale-up, post-processing and pharmaceutical regulatory subjects related to the industrial implementation of these scCO₂-based processes. Finally, it is also discussed the current status of these techniques, as well as their future major perspectives and opportunities for industrial implementation in the upcoming years.