A. Montes

Supercritical Antisolvent Precipitation of Ethyl Cellulose

Supercritical antisolvent (SAS) technique is an appropriate process to obtain micro- and nanoparticles. The application of this process has, until now, been explored in a variety of different fields including: explosives, polymers, pharmaceutical compounds, colouring matter, superconductors, catalysts, and inorganic compounds. Biocompatible and biodegradable polymers are playing more and more important roles in pharmaceutical areas such as tissue engineering and drug delivery. Formulation of these polymers into suitable solid-state forms plays an important role in safety, stability, and efficiency of the products. Ethyl cellulose is commonly used as drug carrier in controlled delivery systems. In this work, particles of ethyl cellulose have been precipitated by SAS using CO2 as antisolvent and dichloromethane (DCM) as solvent. We studied the effects of concentration on the particle size distribution (PSD) of the precipitates. Ethyl cellulose size-controlled particles have been produced in the micrometer range 3.8–5.0 μm, and an increase of the mean particle diameter (MPD) was observed with the increase of the concentration of the solution.

Particles Formation Using Supercritical Fluids

The particle precipitation into micro and nanoparticles has been an active research field for decades (Chattopadhyay & Gupta, 2001; Kalogiannis et al., 2005; Rehman et al., 2001; Reverchon, 1999; Velaga et al., 2002; YeoL or using it as antisolvent, the SAS technique (Supercritical AntiSolvent); the choice between one or another depends on the active substance high or low solubility in the supercritical fluid. The RESS process consists of solubilising the active ingredient of interest in the supercritical fluid and then rapidly depressurising this solution through a nozzle, thus causing the precipitation, extremely fast, of this compound. In other words, the process is based on the transition of active compound from soluble to insoluble state when the carbon dioxide passes from the supercritical to the gaseous phase. This technique has been applied on the particle precipitation and co-precipitation of many active ingredients/polymers (Kongsombut et al., 2009; Sane & Limtrakul, 2009; Turk et al., 2006; Vemavarapu et al., 2009; Wen et al., 2010). The SAS technique, in all its variants, generally consists of spraying a solution of the solute to be precipitated into the supercritical fluid. The mass transfer behavior of the droplets is thought to be a key factor affecting particle morphology (Werling & Debenedetti, 1999). The volumetric expansion of the solvent reduces the solvation capacity of the solvent, causing the supersaturation of the liquid phase and the consequent generation of the particles. The SAS process has been carried out for many particles precipitation and polymeric encapsulation of particles of active ingredients (Ai-Zheng et al., 2009; Chong et al., 2009a;

Generation of quercetin/cellulose acetate phthalate systems for delivery by supercritical antisolvent process.

&NA; Supercritical antisolvent process (SAS) has been used to precipitate microparticles of quercetin, a plant pigment found in many foods and used for medical treatments, pharmaceutical and cosmetic industries, together with nanoparticles of cellulose acetate phthalate (CAP), a polymer quite frequently used in drug delivery. Previously, precipitation of nanoparticles of CAP by the same process was studied at different conditions of pressure, temperature, CO2 and solution flow rates, nozzle diameter and initial concentration of the solution. Morphologies of the precipitates were analyzed by scanning electron microscopy (SEM). A range between 84 and 145 nm of diameter in spherical particle were achievement in CAP precipitation. A same range of semi‐spherical particles of CAP around 145 nm and needle‐like particle of quercetin was obtained in the coprecipitation experiments. X‐ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) were carried out to find out the possible loss of crystallinity of the coprecipitates and the possible interactions between the polymer and quercetin, respectively. Release profiles of quercetin were carried out in simulated gastric and intestinal fluids. Higher quercetin:polymer ratios in the coprecipitates are recommended to achieve faster release and higher solubilities of quercetin in the assayed time. This fact would allow its use in pharmaceutical, cosmetic or nutraceutical applications. Graphical abstract Figure. SEM images of a) commercial cellulose acetate phthalate, b) commercial quercetin and c) coprecipitation of CAP/quercetin after SAS process. Figure. No caption available.

Producing new stone consolidants for the conservation of monumental stones

A customary procedure in the protection of monumental buildings is to consolidate decaying stone by applying commercial products containing tetraethoxysilane (TEOS). These products polymerize within the porous structure of the stone, significantly increasing the cohesion of the material. However, TEOS-based consolidants have practical drawbacks, such as cracking during the drying phase, and blockage of the rock pores. In order to address this problem, the authors increased the porosity of the product by including colloidal particles in the initial sol state. Colloidal silica particles were added to TEOS-based sols resulting in a stone consolidant with improved properties. The addition of ethanol increased the products viscosity in order to better permeate into the stone structure. The newly formulated TEOS-based consolidant is compared with the commercial consolidants, Tegovakon V 100, using graphs and tables. -- ICCROM

Preparation of polyphenol fine particles potent antioxidants by a supercritical antisolvent process using different extracts of Olea europaea leaves

Various extracts from olive leaves have been precipitated by a supercritical antisolvent (SAS) process to evaluate the possibility of producing polyphenol fine particles with controlled size and size distribution. Olive leaves were initially extracted with subcritical fluids using mixtures of CO2+ethanol at 10% and 50%, by pressurized liquid extraction (PLE) with water, ethanol and a hydroalcoholic mixture (50: 50) (v/v), and also by conventional ethanol extraction (CE). PLE gave the extract with the highest yield and the best antioxidant activity. SAS precipitation was unsuccessful for the extracts obtained with pressurized water and with the hydroalcoholic mixture (50: 50) (v/v). The SAS precipitates with the smallest particle sizes were produced from extracts obtained with subcritical fluids. The SAS precipitates obtained after the conventional ethanol extraction of olive leaves showed the best antioxidant activity.

Polymer encapsulation of amoxicillin microparticles by SAS process

Abstract Encapsulation of amoxicillin (AMC) with ethyl cellulose (EC) by a supercritical antisolvent process (SAS) was investigated. AMC microparticles obtained previously by an SAS process were used as host particles and EC, a biodegradable polymer used for the controlled release of drugs, was chosen as the coating material. In this work, a suspension of AMC microparticles in a solution of ethyl cellulose in dichloromethane (DCM) was sprayed through a nozzle into supercritical CO2. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and HPLC analyses were carried out. The effects of AMC:EC ratio, the initial polymer concentration of the solution, temperature and pressure on the encapsulation process were investigated. Although all the experiments led to powder precipitation, the AMC encapsulation was achieved in only half of the cases, particularly when the lower drug:polymer ratios were assayed. In general, it was observed that the percentages of AMC present in the precipitates were higher on increasing the AMC:EC ratio. In these cases composites rather than encapsulates were obtained. The in vitro release profiles of the resulting materials were evaluated in order to ascertain whether composites can be used as encapsulated systems for drug delivery systems.

Studies on the biosynthesis of secobotryane skeleton

Abstract The labelling and coupling patterns of secobotrytrienediol, biosynthesised from [1-13C] and [1,2-13C2]-acetate by the fungus Botrytis cinerea, have been used to define the mode of formation and the biogenetic origin of secobotrytrienediol. [10-2H]-Botrydiol was not incorporated into the secobotryane skeleton. In addition, this feeding experiment led to the isolation of three new unlabelled derivatives possessing a secobotryane skeleton, secobotrydiene-3,10,15-triol, secobotrydiene-3,4,10,15-tetraol, and secobotrytriene-10,12,15-triol.

Hydrodynamics Influence on Particles Formation Using SAS Process

Particle size and particle size distribution play an important role in many fields such cosmetic, food, textile, explosives, sensor, catalysis and pharmaceutics among others. Many properties of industrial powdered products can be adjusted by changing the particle size and particle size distribution of the powder. The conventional methods to produce microparticles have several drawbacks: wide size distribution, high thermal and mechanical stress, environmental pollution, large quantities of residual organic solvent and multistage processes are some of them. The application of supercritical fluids (SCF) as an alternative to the conventional precipitation processes has been an active field of research and innovation during the past two decades (Jung & Perrut, 2001; Martin& Cocero, 2008; Shariati P this also meets the pharmaceutical requirements for the absence of residual solvent, correct technological and biopharmaceutical properties and high quality (Benedetti et al., 1997; Elvassore et al., 2001; Falk& Randolph, 1998; Moneghini et al., 2001; Reverchon& Della Porta, 1999; Reverchon, 2002; Subramaniam et al., 1997; Yeo et al., 1993; Winters et al.,1996), as well as giving enhanced therapeutic action compared with traditional formulations (Giunchedi et al., 1998; Okada& Toguchi, 1995). The revised literature demonstrates that there are two principal ways of micronizing and encapsulating drugs with polymers: using supercritical fluid as solvent, the RESS technique (Rapid Expansion of Supercritical Solutions); or using it as antisolvent, the SAS technique (Supercritical AntiSolvent); the choice of one or other depends on the high or low solubility, respectively, of the polymer and drug in the supercritical fluid. Although the experimental parameters influences on the powder characteristic as particle size and morphologies is now qualitatively well known, the prediction of the powder characteristics is not feasible yet. This fact it is due to different physical phenomena involved in the SAS process. In most cases, the knowledge of the fluid phase equilibrium is