•A two-stage GMPPT method is proposed.•A segmentation search method is used as the first stage.•A novel variable step-size P&O method is used as the second stage.•Extensive simulation are performed ...to obtain the segmentation rule.•The proposed GMPPT method can easily be integrated with PGS firmware.
Photovoltaic generation systems (PGSs) frequently experience partially shaded conditions (PSCs). Because PSC creates several peak values on the power-to-voltage characteristic curve, developing an algorithm that facilitates tracking global maximum power point (GMPP) is crucial. Therefore, this study introduced a two-stage GMPP tracking algorithm. In the first stage, this study developed the segmentation rules after performing extensive simulations on existing products. During the second stage, this study proposed a novel variable step-size perturb and observe method to increase the speed of searching for GMPP. The presented method feature advantages, such as simple structures, high tracking speeds, enhanced tracking accuracy, improved success rate, and easy integration with original PGS firmware. To verify the correctness of the proposed method, this study developed a 2kW PGS prototype, which was used in subsequent simulations and experiments to assess method performance.
Display omitted
•Citrus oil has been encapsulated in PEG by PGSS process.•The influence of process conditions on the characteristics of particles has been investigated.•Particles of different sizes ...and shapes were obtained.•The EE was dependent on process conditions and oxidative stability was improved by encapsulation.•The in vitro release of encapsulated oil was dependent on the pH of the incubation media.
Citrus oil was encapsulated in polyethylene glycol (PEG) using the particles from gas saturated solutions (PGSS) technique. The impact of process conditions, i.e., pressure, temperature, and citrus oil/PEG mixing ratio on the characteristics of formed microparticles has been investigated. The particles with sizes of 190.56–373.32μm and different shapes were obtained. The efficiency of encapsulation ranged between 43.95% and 83.87%. The oxidative stability and in vitro release was significantly changed depending on storage temperature and pH of the incubation medium, respectively, and the oxidative stability was significantly improved by encapsulation using PGSS process.
The delivery of bioactive agents using active wound dressings for the management of pain and infections offers improved performances in the treatment of wound complications. In this work, solid lipid ...microparticles (SLMPs) loaded with lidocaine hydrochloride (LID) were processed and the formulation was evaluated regarding its ability to deliver the drug at the wound site and through the skin barrier. The SLMPs of glyceryl monostearate (GMS) were prepared with different LID contents (0, 1, 2, 4, and 10 wt.%) using the solvent-free and one-step PGSS (Particles from Gas-Saturated Solutions) technique. PGSS exploits the use of supercritical CO2 (scCO2) as a plasticizer for lipids and as pressurizing agent for the atomization of particles. The SLMPs were characterized in terms of shape, size, and morphology (SEM), physicochemical properties (ATR-IR, XRD), and drug content and release behavior. An in vitro test for the evaluation of the influence of the wound environment on the LID release rate from SLMPs was studied using different bioengineered human skin substitutes obtained by 3D-bioprinting. Finally, the antimicrobial activity of the SLMPs was evaluated against three relevant bacteria in wound infections (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa). SLMPs processed with 10 wt.% of LID showed a remarkable performance to provide effective doses for pain relief and preventive infection effects.
Display omitted
•Copper nanoparticles were successfully loaded into lipid microparticles by PGSS.•Mixtures with a water content up to 40% were effectively processed.•Microparticles with uniformly ...distributed metal nanoparticles were produced.•Copper encapsulation efficiency up to 60% was achieved.
Production of lipid particles loaded with metal nanoparticles by supercritical fluids based processes has been barely studied. In this work, copper nanoparticles were loaded into glyceryl palmitostearate microparticles by PGSS® (Particles from Gas Saturated Solutions). The effect of different variables, temperature (60–80°C), copper load (0.2–5%w/w) and water addition (0–40%w/w), in particle size and encapsulation efficiency has been studied. The dispersion of metal nanoparticles in the lipid has been determined by SEM-FIB coupled with EDS mapping. In all cases, mean particle size values lower than 70μm have been obtained, and encapsulation efficiencies around 60% have been achieved. The addition of water has no negative effect in encapsulation efficiency nor in nanoparticles dispersion within the lipid microparticle, being important since nanoparticles are commonly synthetized in aqueous medium.
This paper will discuss about the utilization of supercritical fluid (SCF) process to produce fine particles. Supercritical fluids (SCFs) process can be considered as an emerging “clean” technology ...for the production of small-size or fine particles (e.g. micron-size). Microsphere is a material in micron scale which has been widely used as adsorbent, catalyst support, and drug delivery system. For advanced application, those materials are formulated in the form of porous microspheres. There are several methods that can be used using SCFs. Those method are, Rapid Expansion of Supercritical Solution (RESS), Gas Anti-Solvent/Supercritical Anti-Solvent (GAS/ SAS), Aerosol Solvent Extraction System (ASES), dan Solution Enhanced Dispersion by Supercritical Fluids (SEDS) and Particle from Gas-Saturated Solutions/Suspensions (PGSS). Considering the morphology of material which will be used to prepare microsphere, each of methods above has specific advantages and disadvantages toward the material. Based on the literatures, the ASES method is more likely to produce porous microparticles (microspheres). In the ASES method, porous microsphere formation is the result of interactions between: degrees of supersaturation, nucleation velocity and crystal growth.
Solid lipid microparticles (SLMPs) are attractive carriers as delivery systems as they are stable, easy to manufacture and can provide controlled release of bioactive agents and increase their ...efficacy and/or safety. Particles from Gas-Saturated Solutions (PGSS
) technique is a solvent-free technology to produce SLMPs, which involves the use of supercritical CO
(scCO
) at mild pressures and temperatures for the melting of lipids and atomization into particles. The determination of the key processing variables is crucial in PGSS
technique to obtain reliable and reproducible microparticles, therefore the modelling of SLMPs production process and variables control are of great interest to obtain quality therapeutic systems. In this work, the melting point depression of a commercial lipid (glyceryl monostearate, GMS) under compressed CO
was studied using view cell experiments. Based on an unconstrained D-optimal design for three variables (nozzle diameter, temperature and pressure), SLMPs were produced using the PGSS
technique. The yield of production was registered and the particles characterized in terms of particle size distribution. Variable modeling was carried out using artificial neural networks and fuzzy logic integrated into neurofuzzy software. Modeling results highlight the main effect of temperature to tune the mean diameter SLMPs, whereas the pressure-nozzle diameter interaction is the main responsible in the SLMPs size distribution and in the PGSS
production yield.
Literature data on basic research for and practical application of the synthesis of micro- and nanoparticles with the use of supercritical fluids (SCFs) are systematized and analyzed. The review of ...SCF-based micronization is divided into sections according to the role played by an SCF in the process, which is in most cases a solvent (the rapid expansion of supercritical solutions (RESS)), an antisolvent (supercritical antisolvent precipitation (SAS)), or a solute (particles formed from gas-saturated solutions (PGSS)). Special attention is given to means less covered in the literature, where the SCF is a co-solute (SAA, CAN-BD, and DELOS). The main advantages, limitations, and applicability of each approach for a specific range of substances are analyzed in detail. It is shown that the range of the considered substances is not limited to the best-described pharmaceutical objects; rather, it is greatly expanded to cover possible applications of SCF micronization. The focus is mainly on works published over the last decade.
Poor aqueous solubility of drug candidates is a major challenge for the pharmaceutical scientists involved in drug development. Particle size reduction appears as an effective and versatile option ...for solubility improvement. Nanonization is an attractive solution to improve the bioavailability of the poorly soluble drugs, improved therapies, in vivo imaging, in vitro diagnostics and for the production of biomaterials and active implants. In drug delivery, application of nanotechnology is commonly referred to as Nano Drug Delivery Systems (NDDS). In this article, commercially available nanosized drugs, their dosage forms and proprietors, as well as the methods used for preparation like milling, high pressure homogenization, vacuum deposition, and high temperature evaporation were listed. Unlike the traditional methods used for the particle size reduction, supercritical fluid-processing techniques offer advantages ranging from superior particle size control to clean processing. The primary focus of this review article is the use of supercritical CO2 based technologies for small particle generation. Particles that have the smooth surfaces, small particle size and distribution and free flowing can be obtained with particular SCF techniques. In almost all techniques, the dominating process variables may be thermodynamic and aerodynamic in nature, and the design of the particle collection environment. Rapid Expansion of Supercritical Solutions (RESS), Supercritical Anti Solvent (SAS) and Particles from Gas Saturated Solutions (PGSS) are three groups of processes which lead to the production of fine and monodisperse powders. Few of them may also control crystal polymorphism. Among the aforementioned processes, RESS involves dissolving a drug in a supercritical fluid (SCF) and passing it through an appropriate nozzle. Rapid depressurization of this solution causes an extremely rapid nucleation of the product. This process has been known for a long time but its application is limited. Carbon dioxide, which is the only supercritical fluid that is preferentially used in pharmaceutical processes, is not a good solvent for many Active Pharmaceutical Ingredients (API). Various researchers have modified the RESS process to overcome its solubilizing limitations, by introducing RESOLV, RESAS, and RESS-SC. Overall, all RESS based processes are difficult to scale up. The SAS processes are based on decreasing the solvent power of a polar organic solvent in which the substrate (API & polymer of interest) is dissolved, by saturating it with carbon dioxide (CO2) at supercritical conditions. CO2 causes precipitation and recrystalization of the drug. SAS is scalable and can be applied to a wide variety of APIs and polymers. Minor modifications of basic SAS process include GAS, ASES, SAS-DEM and SAS-EM. Processes where SCF is used as an anti solvent and dispersing agent include SEDS, SAA, and A-SAIS. The mechanisms and applications of these processes were briefly discussed. In PGSS, CO2 is dissolved in organic solutions or melted compounds and it is successfully used for manufacturing drug products as well as for drying purposes. The two widely used methods, PGSSdrying and CAN-BD SCF, were also included in discussions. Among the limitations of the techniques involved, the poor solvent power of CO2, the cost and necessity of voluminous usage of the CO2 can be mentioned. There is still confusion in contribution of each variable on the particle morphology and properties regardless of the number of mechanistic studies available. The advantages of especially SAS and PGSS based techniques are the production of the nano or micro sized spherical particles with smooth surfaces and narrow particle size distribution. Regardless of its advantages, the reasons why 25 years of active research, and more than 10 years of process development could not promote the use of (SCF) technology, and produced only few commercial drug products, necessitate further evaluation of this technique.
Display omitted
•Detailed analyses of the unit operations of the PGSS process.•Supercritical carbon dioxide is promoting the mixing.•The flow behavior during the expansion step is strongly ...influencing the particle formation.•Pulsations lead to bi-modal particle size distributions, due to different spray patterns.
Supercritical fluid assisted sprays for particle generation are widely researched in groups all over the world. Most of the research results follow an empirical approach, trying to bring process conditions into a correlation with product properties. In many cases, a deeper understanding of what is happening in the single unit steps of such processes is missing. Nearly all spray processes using supercritical fluids can be subdivided into the individual steps liquefaction, dosing, mixing and particle formation. This article discusses how far these single steps are developed and understood, and highlights which parameters and conditions along the unit operations of the PGSS process influence particle formation.
Display omitted
► β-Carotene has been encapsulated in soybean lecithin by PGSS-drying. ► Particles of 10–500μm, constituted by fused spheres, have been obtained. ► Encapsulation efficiencies up to ...60% have been achieved. ► Rehydration produce 1–5μm multilamellar liposomes loaded with β-carotene.
The application of β-carotene as a natural colourant in food and nutraceutical products requires an appropriate formulation in order to protect the active compound from degradation and overcome the low bioavailability due to a low solubility in aqueous media. Liposomes as carriers for β-carotene can enhance their release to the organism and improve their preservation. In this work, β-carotene has been encapsulated in soybean lecithin using the novel PGSS (Particles from Gas Saturated Solutions)-drying technique. An experimental study of the influence of the main process parameters (pressure, temperature, gas to product ratio and concentration of carrier material) has been carried out. Dry particles of 10–500μm, constituted by fused spherical particles of less than 10μm, have been obtained, with β-carotene encapsulation efficiencies up to 60%. By hydration of these particles, β-carotene-loaded multilamellar liposomes of 1–5μm have been obtained.
PDF
