Production of ultrafine clobetasol propionate via rapid expansion of supercritical solution (RESS): Full factorial approach

Development of clobetasol-loaded biodegradable nanoparticles as an endodontic intracanal medicament

AIM

The aim of current study is the development and optimization of biodegradable polymeric nanoparticles (NPs) to be used in the field of Endodontics as intracanal medication in cases of avulsed teeth with extended extra-oral time, utilizing PLGA polymers loaded with the anti-inflammatory drug clobetasol propionate (CP).

METHODOLOGY

CP-loaded nanoparticles (CP-NPs) were prepared using the solvent displacement method. CP release profile from CP-NPs was assessed for 48 h against free CP. Using extracted human teeth, the degree of infiltration inside the dentinal tubules was studied for both CP-NPs and CP. The anti-inflammatory capacity of CP-NPs was evaluated in vitro measuring their response and reaction against inflammatory cells, in particular against macrophages. The enzyme-linked immunosorbent assay (ELISA) was used to examine the cytokine release of IL-1β and TNF-α.

RESULTS

Optimized CP-NPs displayed an average size below 200 nm and a monomodal population. Additionally, spherical morphology and non-aggregation of CP-NPs were confirmed by transmission electron microscopy. Interaction studies showed that CP was encapsulated inside the NPs and no covalent bonds were formed. Moreover, CP-NPs exhibited a prolonged and steady release with only 21% of the encapsulated CP released after 48 h. Using confocal laser scanning microscopy, it was observed that CP-NPs were able to display enhanced penetration into the dentinal tubules. Neither the release of TNF-α nor IL-1β increased in CP-NPs compared to the LPS control, displaying results similar and even less than the TCP after 48 h. Moreover, IL-1β release in LPS-stimulated cells, decreased when macrophages were treated with CP-NPs.

CONCLUSIONS

In the present work, CP-NPs were prepared, optimized and characterized displaying significant increase in the degree of infiltration inside the dentinal tubules against CP and were able to significantly reduce TNF-α release. Therefore, CP-NPs constitute a promising therapy for the treatment of avulsed teeth with extended extra-oral time.

Melting Point Depression of Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Triblock Polymers in Supercritical Carbon Dioxide in the Presence of Menthol as a Solid Co-Plasticiser

The melting behaviour of the triblock polymers, Pluronic F38, F68, F77, F108, and F127, was investigated in pressurised CO₂ and in the presence of menthol. The melting points of the polymers combined with 0, 10, 25, and 50 wt% of menthol were studied at atmospheric pressure and compared with those at 10 and 20 MPa in supercritical carbon dioxide (scCO₂). The highest melting point depressions of 16.8 ± 0.5 °C and 29.0 ± 0.3 °C were observed at 10 and 20 MPa, respectively. The melting point of triblock polymers in pressurised CO₂ was found to be dependent on molecular weight, poly(propylene oxide) (PPO) content, and menthol percentage. The melting point of most of the polymers studied in this work can be reduced to room temperature, which can be pivotal to the formulation development of thermolabile substances using these polymers.

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.

Trends on the Rapid Expansion of Supercritical Solutions Process Applied to Food and Non-food Industries

BACKGROUND

The supercritical fluids applied to particle engineering over the last years have received growing interest from the food and non-food industries, in terms of processing, packaging, and preservation of several products. The rapid expansion of supercritical solutions (RESS) process has been recently reported as an efficient technique for the production of free-solvent particles with controlled morphology and size distribution.

OBJECTIVE

In this review, we report technological aspects of the application of the RESS process applied to the food and non-food industry, considering recent data and patent survey registered in literature.

METHODS

The effect of process parameters cosolvent addition, temperature, pressure, nozzle size among others, during RESS on the size, structure and morphology of the resulted particles, and the main differences about recent patented RESS processes are reviewed.

RESULTS

Most of the experimental works intend to optimize their processes through investigation of process parameters.

CONCLUSION

RESS is a feasible alternative for the production of particles with a high yield of bioactive constituents of interest to the food industry. On the other hand, patents developed using this type of process for food products are very scarce, less attention being given to the potential of this technique to develop particles from plant extracts with bioactive substances.

Recrystallization and Micronization of p-Toluenesulfonamide Using the Rapid Expansion of Supercritical Solution (RESS) Process

This study is focused on the micronization of p-toluenesulfonamide (p-TSA) using the rapid expansion of supercritical solution (RESS) process. Taguchi’s experimental design method was applied to determine the optimum operating conditions. L9(34) orthogonal array with four control factors and three levels of each control factor was used to design nine experimental conditions. Four control factors were selected, including extraction temperature, extraction pressure, pre-expansion temperature, and post-expansion temperature. The particle size and morphology of the prepared samples were observed by scanning electron microscopy (SEM). In addition, Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) were employed to compare the differences between the raw and micronized p-TSA particles. The experimental and analytical results indicated that the extraction temperature was the most significant factor for the micronization of p-TSA in the RESS process, and the optimal operating conditions were at an extraction temperature of 50 °C, an extraction pressure of 220 MPa, a pre-expansion temperature of 220 °C, and a post-expansion temperature of 30 °C. The p-TSA particles were micronized from the original average size of 294.8 μm to the smallest average size of 1.1 μm at the optimal RESS process conditions. Furthermore, the physicochemical characteristics of p-TSA did not differ significantly before and after recrystallization.

Evaluation of the Potential Use of Laminar Extrudates on Stabilizing Micronized Coumarin Particles by Supercritical Fluids (RESS)-Study of Different RESS Processing Variables and Mode of Operation

The study evaluates the ability of extrudates to deliver coumarin particles micronized by the rapid expansion of supercritical solutions (RESS). The RESS parameters were drug load (2-50 g), pressure (15-42 MPa) and temperature (40-60°C) in the extraction and pressure in the expansion (0.1-5 MPa) chambers in batch or continuous and CO₂ flow rate in the continuous mode of operation. Particles were characterized for size (laser diffractometry, optical and electronic microscopies-19-61 μm), surface area (BET-0.282-0.423 m²/g), density (pycnometry-1.273-1.358 g/cm³) and yield (2-70%). Extrudates were characterized for the force of extrusion (4 kN), release of coumarin (100%/24 h) and mechanical properties (bending strength and stiffness increased, whereas elasticity decreased in storage) and X-ray diffractometry (micronized particles and extrudates have shown identical patterns) and calorimetry (DSC, enthalpies increased on storage). In the discontinuous mode of operation, increased loads in the extraction or increased pressure in the expansion chambers led to larger particles, whereas increased temperature and pressure in the extraction chamber led to smaller particles. In the continuous mode of operation, a decrease on the expansion pressure, load and CO₂ flow rate led to increased yields. An increase on the flow rate led to a decrease on the particles' diameter, but an increase on coumarin load in the extraction chamber led to an increase in diameter. The study has identified the key parameters in RESS continuous and discontinuous modes of operation affecting the properties of the micronized coumarin particles and has proved the ability of extrudates with a laminar shape on delivering micronized particles.

Nanosizing techniques for improving bioavailability of drugs

The poor solubility of significant number of Active Pharmaceutical Ingredients (APIs) has become a major challenge in the drug development process. Drugs with poor solubility are difficult to formulate by conventional methods and often show poor bioavailability. In the last decade, attention has been focused on developing nanocrystals for poorly water soluble drugs using nanosizing techniques. Nanosizing is a pharmaceutical process that changes the size of a drug to the sub-micron range in an attempt to increase its surface area and consequently its dissolution rate and bioavailability. The effectiveness of nanocrystal drugs is evidenced by the fact that six FDA approved nanocrystal drugs are already on the market. The bioavailabilities of these preparations have been significantly improved compared to their conventional dosage forms. There are two main approaches for preparation of drug nanocrystals; these are the top-down and bottom-up techniques. Top-down techniques have been successfully used in both lab scale and commercial scale manufacture. Bottom-up approaches have not yet been used at a commercial level, however, these techniques have been found to produce narrow sized distribution nanocrystals using simple methods. Bottom-up techniques have been also used in combination with top-down processes to produce drug nanoparticles. The main aim of this review article is to discuss the various methods for nanosizing drugs to improve their bioavailabilities.

Nanoformulation and encapsulation approaches for poorly water-soluble drug nanoparticles

During the last few decades the nanomedicine sector has emerged as a feasible and effective solution to the problems faced by the high percentage of poorly water-soluble drugs. Decreasing the size of such drug compounds to the nanoscale can significantly change their physical properties, which lays the foundation for the use of nanomedicine for pharmaceutical applications. Various techniques have been developed to produce poorly water-soluble drug nanoparticles, mainly to address the poor water-soluble issues but also for the efficient and targeted delivery of such drugs. These techniques can be generally categorized into top-down, bottom-up and encapsulation approaches. Among them, the top-down approaches have been the main choice for industrial preparation of drug nanoparticles while other methods are actively investigated by researchers. In this review, we aim to give a comprehensive overview and latest progress of the top-down, bottom-up, and encapsulation methods for the preparation of poorly water-soluble drug nanoparticles and how solvents and additives can be selected for these methods. In addition to the more industrially applied top-down approaches, the review is focused more on bottom-up and encapsulation methods, particularly covering supercritical fluid-related methods, cryogenic techniques, and encapsulation with dendrimers and responsive block copolymers. Some of the approved and mostly used nanodrug formulations on the market are also covered to demonstrate the applications of poorly water-soluble drug nanoparticles. This review is complete with perspectives on the development and challenges of fabrication techniques for more effective nanomedicine.