Modification of indomethacin crystals using supercritical and aqueous antisolvent crystallizations

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.

Supercritical fluid (SCF)-assisted fabrication of carrier-free drugs: An eco-friendly welcome to active pharmaceutical ingredients (APIs)

Despite the success in developing various pharmaceutical formulations, most of the active pharmaceutical ingredients (APIs)/drugs, according to the Biopharmaceutics Classification System (BCS), often suffer from various intrinsic limitations of solubility and permeability, substantially hindering their bioavailability in vivo. Regardless of the fact that the availability of different particle fabrication approaches (top-down and bottom-up) towards pharmaceutical manufacturing, the supercritical fluid (SCF) technology has emerged as one of the highly effective substitutes due to the environmentally benign nature and processing convenience, as well as the economically promising character of SCFs. The exceptional features of SCFs have endowed the fabrication of various APIs either solely or in combination with the compatible supramolecular species towards achieving improved drug delivery. Operating such APIs in high-pressure conditions often results in arbitrary-sized particulate forms, ranging from micron-sized to sub-micron/nano-sized particles. Comparatively, these SCF-processed particles offer enhanced tailorable physicochemical and morphological properties (size, shape, and surface), as well as improved performance efficacy (bioavailability and therapy) over the unprocessed APIs. Although the "carrier-based" delivery is practical among diverse delivery systems, the direct fabrication of APIs into suitable particulate forms, referred to as "carrier-free" delivery, has increased attention towards improving the bioavailability and conveying a high payload of the APIs. This review gives a comprehensive emphasis on the SCF-assisted fabrication of diverse APIs towards exploring their great potential in drug delivery. Initially, we discuss various challenges of drug delivery and particle fabrication approaches. Further, different supercritical carbon dioxide (SC-CO₂)-based fabrication approaches depending on the character of SCFs are explicitly described, highlighting their advantages and suitability in processing diverse APIs. Then, we provide detailed insights on various processing factors affecting the properties and morphology of SCF-processed APIs and their pharmaceutical applications, emphasizing their performance efficacy when administered through multiple routes of administration. Finally, we summarize this compilation with exciting perspectives based on the lessons learned so far and moving forward in terms of challenges and opportunities in the scale-up and clinical translation of these drugs using this innovative technology.

A high-throughput system combining microfluidic hydrogel droplets with deep learning for screening the antisolvent-crystallization conditions of active pharmaceutical ingredients

Crystallization of active pharmaceutical ingredients (APIs) is a crucial process in the pharmaceutical industry due to its great impact in drug efficacy. However, conventional approaches for screening the optimal crystallization conditions of APIs are usually time-consuming, labor-intensive and expensive. Recently, droplet microfluidic technology has offered an alternative strategy for high-throughput screening of crystallization conditions. Despite its many advantages such as low sample consumption, reduced operation time, increased throughput, etc., some challenges remain to be solved, such as instability of droplets in the long-term and tedious efforts required for extracting useful information from massive data. To solve these problems, a high-throughput system that combined microfluidic hydrogel droplets with deep learning was proposed for the first time to screen the antisolvent-crystallization conditions of APIs. In this system, stable hydrogel droplets containing different concentrations of indomethacin, its solvent and antisolvent were generated on a chip. Crystals of indomethacin with different morphologies were formed in hydrogel droplets, and their optical images were captured by a camera. Then, deep learning was applied to identify the hundreds of indomethacin crystal images and successfully classify the crystal morphologies in a short time; a ternary phase diagram was drawn by combining the experimental results with the recognition results of crystal morphologies, and was used to guide the scale-up preparations of indomethacin crystals as desired. This system, which integrated high throughput preparation, characterization and data analysis, is also useful for screening the crystallization conditions and processes of semiconductors, catalysts, agrochemicals, proteins and other specialty chemicals.

Recrystallization and Production of Spherical Submicron Particles of Sulfasalazine Using a Supercritical Antisolvent Process

In this study, the recrystallization and production of spherical submicron particles of sulfasalazine, an active pharmaceutical ingredient (API), were performed using the supercritical antisolvent (SAS) process, a nonconventional crystallization technique. Sulfasalazine was dissolved in tetrahydrofuran (THF), and supercritical carbon dioxide (CO2) served as the antisolvent. The effects of operating parameters on the SAS process, including the operating pressure, solution concentration, solution flowrate, CO2 flowrate, and spraying nozzle diameter, at two operating temperatures were examined. The solid-state characteristics of sulfasalazine before and after the SAS process, including particle size, crystal habit, and crystal form, were analyzed using a scanning electron microscope (SEM), powder X-ray diffractometer (PXRD), and differential scanning calorimeter (DSC). A higher operating temperature, intermediate operating pressure, higher CO2 flowrate, and lower solution flowrate are recommended to obtain spherical particles of sulfasalazine. The effects of the solution concentration and spraying nozzle diameter on the SAS process were negligible. Under optimal conditions, spherical sulfasalazine crystals with a mean size of 0.91 μm were generated, and this study demonstrated the feasibility for tuning the solid-state characteristics of API through the SAS process.