Soy lecithin micronization by precipitation with a compressed fluid antisolvent — influence of process parameters

What We Need to Know about Liposomes as Drug Nanocarriers: An Updated Review

Liposomes have been attracted considerable attention as phospholipid spherical vesicles, over the past 40 years. These lipid vesicles are valued in biomedical application due to their ability to carry both hydrophobic and hydrophilic agents, high biocompatibility and biodegradability. Various methods have been used for the synthesis of liposomes, so far and numerous modifications have been performed to introduce liposomes with different characteristics like surface charge, size, number of their layers, and length of circulation in biological fluids. This article provides an overview of the significant advances in synthesis of liposomes via active or passive drug loading methods, as well as describes some strategies developed to fabricate their targeted formulations to overcome limitations of the "first-generation" liposomes.

Preparation of Liposomes from Soy Lecithin Using Liquefied Dimethyl Ether

We investigated a method to prepare liposomes; soy lecithin was dissolved in liquefied dimethyl ether (DME) at 0.56 MPa, which was then injected into warm water. Liposomes can be successfully prepared at warm water temperatures above 45 °C. The transmission electron microscopy (TEM) images of the obtained liposomes, size distribution, ζ-potential measurements by dynamic light scattering and the amount of residual medium were compared by gas chromatography using the conventional medium, diethyl ether. The size of the obtained liposomes was approximately 60-300 nm and the ζ-potential was approximately -57 mV, which was almost the same as that of the conventional medium. Additionally, for the conventional media, a large amount remained in the liposome dispersion even after removal by depressurization and dialysis membrane treatment; however, liquefied DME, owing to its considerably low boiling point, was completely removed by depressurization. Liquefied DME is a very attractive medium for the preparation of liposomes because it does not have the toxicity and residue problems of conventional solvents or the hazards of ethanol addition and high pressure of supercritical carbon dioxide; it is also environmentally friendly.

Computational and Experimental Approaches to Investigate Lipid Nanoparticles as Drug and Gene Delivery Systems

Lipid nanoparticles (LNPs) have been widely applied in drug and gene delivery. More than twenty years ago, DoxilTM was the first LNPs-based drug approved by the US Food and Drug Administration (FDA). Since then, with decades of research and development, more and more LNP-based therapeutics have been used to treat diverse diseases, which often offer the benefits of reduced toxicity and/or enhanced efficacy compared to the active ingredients alone. Here, we provide a review of recent advances in the development of efficient and robust LNPs for drug/gene delivery. We emphasize the importance of rationally combining experimental and computational approaches, especially those providing multiscale structural and functional information of LNPs, to the design of novel and powerful LNP-based delivery systems.

Novel Technologies Based on Supercritical Fluids for the Encapsulation of Food Grade Bioactive Compounds

In recent years, the demand for nutritive, functional and healthy foods has increased. This trend has induced the food industry to investigate novel technologies able to produce ingredients with enhanced functional and physicochemical properties. Among these technologies, one of the most promising is the encapsulation based on supercritical fluids. Thanks to the inherent absence of organic solvent, the low temperature of the process to reach a supercritical state and the capacity to dissolve lipid soluble bioactives, the encapsulation with supercritical carbon dioxide represents a green technology to produce several functional ingredients, with enhanced stability, high load and tailored protection from environmental factors. Furthermore, from the fine-tuning of the process parameters like temperature, pressure and flow rate, the resulting functional ingredient can be easily designed to tailor the controlled release of the bioactive, or to reach specific levels of taste, odor and color. Accordingly, the aim of the present review is to summarize the state of the art of the techniques based on supercritical carbon dioxide for the encapsulation of bioactive compounds of food interest. Pros and cons of such techniques will be highlighted, giving emphasis to their innovative aspects that could be of interest to the food industry.

The Why, Where, Who, How, and What of the vesicular delivery systems

Though vesicular delivery systems have been widely explored and reviewed, no comprehensive review exists that covers their development from the inception of the concept to its culmination in the form of regulated marketed formulations. With the advancement of scientific research in the field of nanomedicine, certain category of vesicular delivery systems have successfully reached the global market. Despite extensive research and highly encouraging results in a plethora of pathological conditions in the preclinical studies, translation of these nanomedicines from laboratory to market has been very limited. Aim of this review is to describe comprehensively the various colloidal delivery systems, focusing mainly on their conventional and advanced methods of preparation, different characterization techniques and main success stories of their journey from bench to bedside of the patient. The review also touches the finer nuances of the use of modern formulation approach of DoE (Design of Experiments) in their formulation and the status of regulatory guidelines for the approval of these nanomedicines.

Supercritical Fluid Technology: An Emphasis on Drug Delivery and Related Biomedical Applications

During the past few decades, supercritical fluid (SCF) has emerged as an effective alternative for many traditional pharmaceutical manufacturing processes. Operating active pharmaceutical ingredients (APIs) alone or in combination with various biodegradable polymeric carriers in high-pressure conditions provides enhanced features with respect to their physical properties such as bioavailability enhancement, is of relevance to the application of SCF in the pharmaceutical industry. Herein, recent advances in drug delivery systems manufactured using the SCF technology are reviewed. We provide a brief description of the history, principle, and various preparation methods involved in the SCF technology. Next, we aim to give a brief overview, which provides an emphasis and discussion of recent reports using supercritical carbon dioxide (SC-CO2 ) for fabrication of polymeric carriers, for applications in areas related to drug delivery, tissue engineering, bio-imaging, and other biomedical applications. We finally summarize with perspectives.

Microencapsulation and characterization of liposomal vesicles using a supercritical fluid process coupled with vacuum-driven cargo loading

A new technique of liposomal microencapsulation, consisting of supercritical fluid extraction followed by rapid expansion of the supercritical solution and vacuum-driven cargo loading, was successfully developed. It is a continuous flow-through process without usage of any toxic organic solvent. For use as a coating material, the solubility of soy phospholipids in supercritical carbon dioxide was first determined using a dynamic equilibrium system and the data was correlated with the Chrastil model with good agreement. Liposomes were made with D-(+)-glucose as a cargo and their properties were characterized as functions of expansion pressure, temperature, and cargo loading rates. The highest encapsulation efficiency attained was 31.7% at the middle expansion pressure of 12.41MPa, highest expansion temperature of 90°C, and lowest cargo loading rate of 0.25mL/s. The large unilamellar vesicles and multivesicular vesicles were observed to be a majority of the liposomes produced using this eco-friendly process.

Lipid-based nanovesicles for nanomedicine

Multifunctional lipid-based nanovesicles (L-NVs) prepared by molecular self-assembly of membrane components together with (bio)-active molecules, by means of compressed CO₂-media or other non-conventional methods lead to highly homogeneous, tailor-made nanovesicles that are used for advanced nanomedicine. Confocal microscopy image of siRNA transfection using L-NVs, reprinted with permission from de Jonge,et al.,Gene Therapy, 2006,13, 400–411.

Characteristics of lipid micro- and nanoparticles based on supercritical formation for potential pharmaceutical application

The interest of the pharmaceutical industry in lipid drug delivery systems due to their prolonged release profile, biocompatibility, reduction of side effects, and so on is already known. However, conventional methods of preparation of these structures for their use and production in the pharmaceutical industry are difficult since these methods are usually multi-step and involve high amount of organic solvent. Furthermore, some processes need extreme conditions, which can lead to an increase of heterogeneity of particle size and degradation of the drug. An alternative for drug delivery system production is the utilization of supercritical fluid technique. Lipid particles produced by supercritical fluid have shown different physicochemical properties in comparison to lipid particles produced by classical methods. Such particles have shown more physical stability and narrower size distribution. So, in this paper, a critical overview of supercritical fluid-based processes for the production of lipid micro- and nanoparticles is given and the most important characteristics of each process are highlighted.

Preparation of coenzyme Q10 liposomes using supercritical anti-solvent technique

Coenzyme Q(10) (CoQ(10)) proliposomes were prepared using the supercritical anti-solvent (SAS) technique to encapsulate CoQ(10). The mixture of cholesterol and soya bean phosphatidylcholine (PC) was chosen as wall materials. The effects of operation conditions (temperature, pressure and components) on the recovery of CoQ(10) and the CoQ(10) loading in CoQ(10) proliposomes were studied. At the optimum conditions of pressure of 8.0 MPa, temperature of 35°C, the weight ratio of 1/10 between CoQ(10) and PC, and the weight ratio of 1/3 between cholesterol and PC, the CoQ(10) loading reached 8.92%. CoQ(10) liposomes were obtained by hydrating CoQ(10) proliposomes and the entrapment efficiency of CoQ(10) reached 82.28%. The morphologies of CoQ(10) proliposomes were characterized by scanning electron microscope, and their solid states were characterized by X-ray diffractometer. The structures of CoQ(10) liposomes were characterized by transmission electron microscope. The particle size distribution of CoQ(10) liposomes was determined by dynamic light scattering instrument. The results indicate that CoQ(10) liposomes with particle sizes about 50 nm can be easily obtained from hydrating CoQ(10) proliposomes prepared by SAS technique.

Physical and Chemical Stability of Miconazole Liposomes Prepared by Supercritical Aerosol Solvent Extraction System (ASES) Process

The aerosol solvent extraction system (ASES) process was applied to prepare miconazole (MCZ) liposomes in a dry and reconstitutable form, the optimized temperature and pressure of which were 35 degrees C and 8.0 MPa, respectively. The influence of compositions of phosphatidylcholine (PC), cholesterol (CHOL), and poloxamer 407 (POLOX) as well as the pH of hydration medium on physical and chemical stability of both dry microparticles and liposomes hydrated from them were examined following storage at 4 degrees C and 25 degrees C for 3 months. MCZ microparticles in dry powder were stable on storage at 4 degrees C but degraded considerably after storage at 25 degrees C. MCZ liposomes hydrated from dry ASES-prepared microparticles at pH 4.0 tended to aggregate, whereas those hydrated at pH 7.2 tended to reduce in size on storage, especially with the addition of CHOL. Liposomes with high MCZ content stored at 4 degrees C degraded faster than when stored at 25 degrees C. Addition of POLOX tended to retard the degradation of MCZ liposomes, whereas CHOL appeared to enhance the degradation on storage under both conditions. The chemical degradation of MCZ liposomes appeared to follow the acid-catalyzed hydrolysis. The MCZ liposomes prepared by the ASES process in this study were substantially internalized after being incubated with human lymphocytes.

Drug Solubility in Phospholipid Carrier as a Predictive Parameter for Drug Recovery in Microparticles Produced by the Aerosol Solvent Extraction System (ASES) Process

The solubility of various drugs in a constant ratio of phosphatidylcholine-cholesterol carrier were studied to investigate their influence on drug recovery in drug-lipid microparticles produced by the aerosol solvent extraction system (ASES) process. Solubility of the drugs in such lipid carrier were determined by using differential scanning calorimetry and confirmed by X-ray powder diffraction study. The results showed that drug possessing relatively high solubility in the lipid carrier used could lead to a higher amount of drug recovered in the drug-lipid microparticles produced. However, too high amount of dissolved drug imposed an adverse effect on the solidification of the lipid carrier during ASES processing, which led to partial film formation in the production column and hence a lower yield of microparticles. Such adverse effect was not the case for the drugs with low solubility in the carrier but there was an incomplete recovery of drug in the produced microparticles due to the partial extraction by the supercritical gas instead. The maximum amount of drug recovered in the ASES-prepared microparticles was found to correlate to the solubility of drug in the lipid carrier so that it might be utilized as a predictive parameter for determining the amount of drug to be incorporated into the microparticles.

Conventional and dense gas techniques for the production of liposomes: a review

The aim of this review paper is to compare the potential of various techniques developed for production of homogenous, stable liposomes. Traditional techniques, such as Bangham, detergent depletion, ether/ethanol injection, reverse-phase evaporation and emulsion methods, were compared with the recent advanced techniques developed for liposome formation. The major hurdles for scaling up the traditional methods are the consumption of large quantities of volatile organic solvent, the stability and homogeneity of the liposomal product, as well as the lengthy multiple steps involved. The new methods have been designed to alleviate the current issues for liposome formulation. Dense gas liposome techniques are still in their infancy, however they have remarkable advantages in reducing the use of organic solvents, providing fast, single-stage production and producing stable, uniform liposomes. Techniques such as the membrane contactor and heating methods are also promising as they eliminate the use of organic solvent, however high temperature is still required for processing.

Comparative Physicochemical Characterization of Phospholipids Complex of Puerarin Formulated by Conventional and Supercritical Methods

PURPOSE

The aim of this work was to compare the physicochemical characteristics of the phospholipids complex of puerarin (Pur) prepared by traditional methods (solvent evaporation, freeze-drying and micronization) and a supercritical fluid (SCF) technology. The physicochemical properties of the pure drug and the corresponding products prepared by two different SCF methods were also compared.

METHODS

Solid-state characterization of particles included differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), solubility, dissolution rate and scanning electron microscopy (SEM) examinations. Besides puerarin phospholipids complex (PPC) by four different methods, the solid-state properties of unprocessed, gas antisolvent (GAS) crystallized and solution enhanced dispersion by supercritical fluid (SEDS) precipitated puerarin samples were also compared. Crystallinity was assessed using DSC and XRPD. Drug-phospholipids interactions were characterized using Fourier transform infrared spectroscopy (FTIR). SEM was used to determine any morphological changes. Pharmaceutical performance was assessed in dissolution rate and solubility tests.

RESULT

The results of the physical characterization attested a substantial correspondence of the solid state of the drug before and after treatment with GAS technique, whereas a pronounced change in size and morphology of the drug crystals was noticed. The GAS-processed puerarin exhibited a better crystal shape confirmed by DSC, XRPD and IR. Polymorphic change of puerarin during SEDS coupled with the dramatic reduction of the dimensions determined a remarkable enhancement of its solubility and in vitro dissolution rate. Phospholipids complex prepared using supercritical fluid technology showed similar properties of physical state, thermal stability and molecular interaction with phospholipids (PC) to those of corresponding systems prepared by other three conventional methods namely solvent evaporation, freeze-drying and micronization as proved by XRPD, DSC, and FTIR. The best dissolution rate was obtained by SEDS-prepared complex, while the highest solubility was obtained for solvent evaporation method.

CONCLUSION

Supercritical fluid technology for the preparation of puerarin and its phospholipids complex has been proven to have significant advantages over the solvent evaporation technique and other conventional methods.

Acetylation of soybean lecithin and identification of components for solubility in supercritical carbon dioxide

There is a growing interest to develop environmentally friendly surfactants for utilization with supercritical carbon dioxide (scCO2), which is a "green" solvent with many industrial applications. The goal of the present work was to separate the commonly used soybean lecithin into a phospholipid-rich fraction, acetylate this fraction, and then test its solubility in scCO2 to gauge its suitability as a surfactant for potential scCO2-based applications. Soybean lecithin was first purified by fractionation using acetone and ethanol and then acetylated with acetic anhydride. The acetylated lecithin was further purified by fractionation with acetone to separate the acetylated fraction from the nonacetylated fraction. High-performance liquid chromatography and electrospray ionization mass spectrometry were utilized to characterize these fractions. The various acetylated phospholipid fractions were then tested for solubility in scCO2 under various pressures and temperatures using both a cloud-point and a Fourier transform infrared apparatus. Acetylation was found to increase the solubility of the phospholipids in scCO2, and N-acetylated phosphatidylethanolamine (NAc-PE) was found to be the most soluble component of the acetylated phospholipids.

The preparation of liposomes using compressed carbon dioxide: strategies, important considerations and comparison with conventional techniques

Numerous strategies are currently available for preparing liposomes, although no single method is ideal in every respect. Two methods for producing liposomes using compressed carbon dioxide in either its liquid or supercritical state were therefore investigated as possible alternatives to the conventional techniques currently used. The first technique used modified compressed carbon dioxide as a solvent system. The way in which changes in pressure, temperature, apparatus geometry and solvent flow rate affected the size distributions of the formulations was examined. In general, liposomes in the nano-size range with an average diameter of 200 nm could be produced, although some micron-sized vesicles were also present. Liposomes were characterized according to their hydrophobic drug-loading capacity and encapsulated aqueous volumes. The latter were found to be higher than in conventional techniques such as high-pressure homogenization. The second method used compressed carbon dioxide as an anti-solvent to promote uniform precipitation of phospholipids from concentrated ethanolic solutions. Finely divided solvent-free phospholipid powders of saturated lipids could be prepared that were subsequently hydrated to produce liposomes with mean volume diameters of around 5 microm.

Application of aerosol solvent extraction system (ASES) process for preparation of liposomes in a dry and reconstitutable form

The aerosol solvent extraction system (ASES) process was applied to prepare liposomes in a dry and reconstitutable form. Dry ASES microparticles containing miconazole (MCZ) as a model drug were prepared by an optimized ASES process with various compositions of spraying solution containing phosphatidylcholine, cholesterol, and Poloxamer 407. The influence of such compositions and the pH of hydration medium on the physico-chemical properties of the produced microparticles were investigated before and after hydration. At optimized conditions, partially crystalline, spherical, and nonporous microparticles associated in aggregates varying from a few microns to 40 microm were produced with the residual content of methylene chloride and methanol lower than 30 and 86 ppm, respectively. The percentage of drug recovered in the produced microparticles was increased with an increase of the drug concentration in the spraying solution. The entrapment efficiency of hydrated MCZ microparticles was improved by increasing the pH of the hydration medium.