Operative parameters optimization production of liposomes for the encapsulation of hydrophilic compounds using a new supercritical process

Liposomes are spherical vesicles formed by a inner aqueous core and a double lipidic layer around it. Conventional techniques for the production of liposomes are characterized by several drawbacks, like the production of micrometric vesicles, a difficult control of the Particle Size Distribution (PSD) and low encapsulation efficiencies (EE) of hydrophilic compounds. Many supercritical semi-continuous techniques were proposed in literature. They are successful in the intent of producing liposomes of smaller diameter, but the EE of hydrophilic compounds and the reproducibility are still a challenge. For this reason, it was recently proposed a new supercritical process whose aim is to invert the steps of production of liposomes, by first creating water droplets and then to fast surround them by phospholipids. We discovered that the high diffusion coefficient of phospholipids in supercritical carbon dioxide allows a fast coverage of water droplets preserving the drug content into the liposome core. In this work, hydrophilic compounds were encapsulated in the vesicles produced using SuperLip, such as Fluorescein, Bovine Serum Albumin (BSA) and Ampicillin, obtaining monodispersed spherical vesicles with a mean size from 100 to 300 nm. Operative parameters like water flow rate and lipid to water mass ratio were optimized. The EEs were evaluated with UV-Vis spectroscopy according to methods reported in literature, and obtaining high values up to 99 % for the three investigated compounds

Biopolymer Particles for Proteins and Peptides Sustained Release Produced by Supercritical Emulsion Extraction

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Vapor–Liquid Equilibria of Quaternary Systems of Interest for the Supercritical Antisolvent Process

In the Supercritical Antisolvent process (SAS), the thermodynamic behavior of complex multicomponent systems can influence the particles’ morphology. However, due to the limited thermodynamic data for multicomponent systems, the effect of solutes is often neglected, and the system is considered as pseudo-binary. It has been demonstrated that the presence of a solute can significantly influence the thermodynamic behavior of the system. In particular, when the SAS process is adopted for the production of drug/polymer coprecipitated microparticles, the effect of both the drug and the polymer in the solvent/CO2 mixture should be considered. In this work, the effect of polyvinylpyrrolidone (PVP), used as the carrier, and of the liposoluble vitamins menadione (MEN) and α-tocopherol (TOC), as model drugs, was investigated as a deviation from the fundamental thermodynamic behavior of the DMSO/CO2 binary system. Vapor–liquid equilibria (VLE) were evaluated at 313 K, with a PVP concentration in the organic solution equal to 20 mg/mL. The effect of the presence of PVP, MEN, and TOC on DMSO/CO2 VLE at 313 K was studied; furthermore, the effect of PVP/MEN and PVP/TOC, at a polymer/drug ratio of 5/1 and 3/1, was determined. Moreover, SAS precipitation experiments were performed at the same polymer/drug ratios using a pressure of 90 bar. Thermodynamic studies revealed significant changes in phase behavior for DMSO/CO2/PVP/TOC and DMSO/CO2/PVP/MEN systems compared to the binary DMSO/CO2 system. From the analysis of the effect of the presence of a single compound on the binary system VLE, it was noted that PVP slightly affected the thermodynamic behavior of the system. In contrast, these effects were more evident for the DMSO/CO2/TOC and DMSO/CO2/MEN systems. SAS precipitation experiments produced PVP/MEN and PVP/TOC microparticles, and the obtained morphology was justified considering the quaternary systems VLE

Operating Parameters Optimization for the Production of Liposomes Loaded with Antibodies Using a Supercritical Fluid-Assisted Process

Encapsulation of antibodies represents a significant advance to protect and deliver these therapeutics in a controlled manner, increasing the stability requested to cover the temporal gap between particle production and their administration. Furthermore, using encapsulation, extracellular, cell surface, and intracellular targets can be reached. This work examines the feasibility of encapsulating mouse IgG isotype control antibodies within phosphatidylcholine-based liposomes using a supercritical fluid-based process called SuperLip (Supercritical-assisted Liposome formation). This process allows a continuous production of both nano- and micrometric liposomes with high encapsulation efficiency working under mild operative conditions. The effect of some operative parameters has been studied on liposome mean diameter, particle size distribution, and antibody entrapment efficiency, comparing these data with those collected working with liposomes obtained by the thin-layer hydration technique. In particular, the effect of water flow rate and of the antibody loading were studied. Antibody-loaded liposomes with mean diameters in the range between 205 and 501 nm have been obtained by using a supercritical fluid-assisted process. High entrapment efficiencies up to 94% have been calculated

Preparation of polycaprolactone nanoparticles via supercritical carbon dioxide extraction of emulsions

Polycaprolactone (PCL) nanoparticles were produced via supercritical fluid extraction of emulsions (SFEE) using supercritical carbon dioxide (scCO2). The efficiency of the scCO2 extraction was investigated and compared to that of solvent extraction at atmospheric pressure. The effects of process parameters including polymer concentration (0.6–10% w/w in acetone), surfactant concentration (0.07 and 0.14% w/w) and polymer-to-surfactant weight ratio (1:1–16:1 w/w) on the particle size and surface morphology were also investigated. Spherical PCL nanoparticles with mean particle sizes between 190 and 350 nm were obtained depending on the polymer concentration, which was the most important factor where increase in the particle size was directly related to total polymer content in the formulation. Nanoparticles produced were analysed using dynamic light scattering and scanning electron microscopy. The results indicated that SFEE can be applied for the preparation of PCL nanoparticles without agglomeration and in a comparatively short duration of only 1 h

Instantaneous coprecipitation of polymer/drug microparticles using the supercritical assisted injection in a liquid antisolvent

In this work, the supercritical assisted injection in a liquid antisolvent (SAILA) has been proposed as a new technique to produce composite microparticles for drug controlled release. Coprecipitation has been attempted for different non-steroidal anti-inflammatory drugs (Diclofenac, DF, Piroxicam, PX, and Indomethacin, ID) using poly-lactic-co-glycolic (PLGA) as the polymer matrix; acetone has been used as the liquid solvent and water as the liquid antisolvent. Coprecipitation was successful in all the cases and encapsulation efficiency ranged between 50 and 97%. The effect of operating parameters, such as the polymer/drug ratio, polymer concentration, injection temperature and pressure on particle morphology and drug release rate has been studied considering the system PLGA/Piroxicam. SEM analysis indicated that non-coalescing spherical microparticles formed by PLGA/PX were produced by SAILA at fast mixing conditions (higher injection pressure and higher temperature) and high polymer/drug ratios (20/1 and 10/1). All coprecipitates showed a sharp particle distribution, with diameters ranging between about 0.28 and 2.50 \uce\ubcm. SAILA composite microparticles have been characterized by X-ray, FT-IR, EDX and UV\ue2\u80\u93vis analysis. PLGA/PX coprecipitates showed a prolonged release, about 7 times slower than the physical mixture of the same compounds; moreover, the polymer/drug ratio and the concentration of polymer in the solvent revealed to be a controlling parameter for drug release. The Hoffenberg's equation has been used to describe experimental data, showing a fair good agreement with PX release data

Production of solid lipid nanoparticles with a supercritical fluid assisted process

In this work, a supercritical fluid continuous process, the Supercritical Assisted Injection in a Liquid Antisolvent (SAILA), was proposed for the production of solid lipid nanoparticles (SLNs). SLNs of soy lecithin, cholesterol and stearic acid were produced in this work. Acetone and ethanol were used as solvents. The effect of lipid concentration on particles size distribution and morphology was studied. SLNs with mean dimensions included between 158 \ub1 53 nm and 326 \ub1 169 nm were obtained for soy lecithin particles, between 151 \ub1 74 nm and 207 \ub1 57 nm for cholesterol and from 364 \ub1 77 nm to 462 \ub1 88 nm for stearic acid particles. All the suspensions were stable over 30 days of observation