Supercritical fluid techniques for materials precipitation have been proposed as an alternative to conventional precipitation processes as they allow to improve the performance of these processes in ...terms of reduction of particle size and control of morphology and particle size distribution, without degradation or contamination of the product. These techniques have received much attention during the last years, and their feasibility and performance have been experimentally demonstrated for many substances. One of the main pending tasks is the development of a systematic procedure for the design and scale-up of these processes. This requires not only empirical knowledge, but also information about the fundamentals of the process. This work aims to review the published literature dealing with a fundamental investigation or modeling of supercritical fluid precipitation processes.
Supercritical fluid (SCF) technology has become an important tool of materials processing in the last two decades. Supercritical CO
2 and H
2O are extensively being used in the preparation of a great ...variety of nanomaterials. The greatest requirement in the application of nanomaterials is its size and morphology control, which determine the application potential of the nanoparticles, as their properties vary significantly with size. Although significance of SCF technology has been described earlier by various authors, the importance of this technology for the fabrication of inorganic and hybrid nanomaterials in biomedical applications has not been discussed thoroughly. This review presents the nanomaterial preparation systematically using SCF technology with reference to the processing of biomedical materials. The basic principles of each one of the processes have been described in detail giving their merits and perspectives. The actual experimental data and results have been discussed in detail with respect to the selected nanomaterials for biomedical applications. The SCF synthesis of nanoparticles like phosphors, magnetic materials, carbon nanotubes, etc. have been discussed as they have potential applications in bio-imaging, hyperthermia, cancer therapy, neutron capture therapy, targeted drug delivery systems and so on. The more recent approach towards the
in situ surface modification, dispersibility, single nanocrystal formation, and morphology control of the nanoparticles has been discussed in detail.
The ethanolic extract of artichoke leaves is phytotherapic. Impregnation is used to protect the bioactive material and is also a means of controlling the release of the encapsulated substance while ...masking unwanted taste and/or color. This research describes a study of artichoke leaf extraction by five techniques and tested the formations of solid-lipid microparticles of beeswax and avocado oil loaded with these extracts by PGSS and their particle stability. Pressurized liquid extraction (PLE) using an intermittent process was optimized and presented the highest content of active compounds in the extracts, although the inulin contents (IC) were higher in the extracts obtained by conventional methods. Two different ratios between solid and liquid lipids and the extract (1:2:3 and 1:2:6; w:w:w) were studied. The particles with a major beeswax ratio showed a smaller distribution and average size (74.2 ± 6.2 µm), but no differences were observed in relation to stability. All extraction techniques were able to yield inulin (max. 173.46 ± 1.27 mginulin/gextract), and with PLE only the temperature had a significant effect on the extraction yield under the studied conditions.
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●Investigation of different processes to obtain artichoke extracts.●Use of ethanol as a green and health-safe solvent in all processes.●Study of the pressurized liquid extraction in an intermittent process to have extracts.●Formation of beeswax particles impregnated with artichoke in supercritical medium.●Characterization and study of particles stability of under unfavorable conditions.
Structured lipid carriers based on mixture of solid lipids with liquid lipids are the second generation of solid lipid particles, offering the advantage of improved drug loading capacity and higher ...storage stability. In this study, structured lipid carriers were successfully prepared for the first time by precipitation from gas saturated solutions. Glyceryl monooleate (GMO), a liquid glycerolipid, was selected in this work to be incorporated into three solid glycerolipids with hydrophilic-lipophilic balance (HLB) ranging from 1 to 13, namely Gelucire 43/01™, Geleol™ and Gelucire 50/13™. In general, microparticles with a irregular porous morphology and a wide particle size distribution were obtained. The HLB of the individual glycerolipids might be a relevant parameter to take into account during the processing of solid:liquid lipid blends. As expected, the addition of a liquid lipid into a solid lipid matrix led to increased stability of the lipid carriers, with no significant modifications in their melting enthalpy after 6 months of storage. Additionally, Gelucire 43/01™:GMO particles were produced with different mass ratios and loaded with ketoprofen. The drug loading capacity of the structured lipid carriers increased as the GMO content in the particles increased, achieving a maximum encapsulation efficiency of 97% for the 3:1 mass ratio. Moreover, structured lipid carriers presented an immediate release of ketoprofen from its matrix with higher permeation through a mucous-membrane model, while solid lipid particles present a controlled release of the drug with less permeation capacity.
The manufacture of particulate hybrid carriers containing a glyceryl monostearate (Lumulse
® GMS-K), a waxy triglyceride (Cutina
® HR), silanized TiO
2 and different active agents (caffeine, ...glutathione or ketoprofen) was investigated with the aim of producing controlled drug delivery systems based on solid lipid particles. Particles were obtained using the supercritical PGSS
® (particles from gas saturated solutions) technique. Experiments were performed at 13
MPa and 345
K, according to previous measurements of lipid melting points. Solid lipid particles were loaded with silanized TiO
2 and caffeine, glutathione or ketoprofen in percentages of 6–7
wt% for the mineral filler and 4.2, 5.6 and 16.1
wt% for the respective drugs. The particles obtained were analyzed in the solid state by thermogravimetric and X-ray diffraction analysis and scanning electron microscopy. Drug contents in the precipitated lipid samples and their elution profiles were studied by HPLC. Hydrophobic drugs, such as ketoprofen, were more efficiently encapsulated in the lipophilic lipidic matrix than hydrophilic drugs, such as caffeine and glutathione.
This study aimed the encapsulation of coffee oil flavor and optimizing the process conditions which affect the encapsulation efficiency (EE). Oil was extracted from roasted Coffea arabica, ...(Yrigachefe, Ethiopia) using supercritical carbon dioxide (Sc–CO2). Then, the extracted oil was encapsulated by polyethyleneglycol (PEG) using particles from gas-saturated solutions (PGSS) process. Process parameters which affect the EE such as, temperature (T, 40–50 °C), pressure (P, 200–300 bar) and polymer-oil ratios (R, 5:1–10:1 g/g) were optimized via Box Behnken design (BBD). The optimal conditions were (T, 40.0 °C, P, 260.14 bar and R, 6.57:1 g/g) with a maximum EE of 79.78%. The encapsulated oil showed peroxide value of 4.56 meq peroxide/kg oil after 12 weeks of storage. Less than 2% loss of fatty acid composition was observed after encapsulation. Moreover, flavor profiles of particles obtained using optimal condition showed very good preservation of flavors. Therefore, microencapsulation using PGSS process could be employed for production of freely flowing powdered particles that can be used in food processing industries.
•Roasted coffee oil was extracted using Sc–CO2.•The oil was successfully encapsulated using PEG by PGSS process.•The PGSS process parameters were optimized using Box Behnkendesign.•The optimum conditions were 40 °C, 260.14bar and 6.57:1polymer-oil ratio.
•Resveratrol and tebuconazole were encapsulated on lecithin and β-glucans.•Dry particles were obtained by spray-drying and PGSS-drying.•High loading of active compound (greater than 50%) was achieved ...for both processes.•Amorphous resveratrol and tebuconazole were found within the encapsulated material.•Encapsulation improved the antifungal action of resveratrol against Botrytis cinerea.
β-Glucans and soy lecithin were used as encapsulating materials for resveratrol and tebuconazole, in order to test their antifungal activity against Botrytis cinerea. First an oil-in-water emulsion was formed and afterwards the emulsion was dried by spray-drying or by particles from gas saturated solutions-drying (PGSS-drying). β-Glucans were precipitated also by supercritical anti-solvent (SAS), but it was not a suitable drying process for this material. Particles were characterized regarding particle size, morphology, crystallinity, encapsulation efficiency and in vitro activity against B. cinerea. Although the emulsions with β-glucans had bigger droplet size than the ones with lecithin, there was no difference on particle size for each encapsulating material, it was just dependent on the drying process. For all the materials and drying processes, completely amorphous particles were obtained, in spite of the crystalline form of the pure active compounds. Concerning the antifungal activity, the encapsulation of tebuconazole did not improve its action, because it was already very effective. Pristine resveratrol did not reduce fungal growth, but it was inhibited between 50% and 70% with encapsulated resveratrol, which implies the production of an effective fungicide against B. cinerea totally from natural origin substances.
Proposed mechanism of formation of solid lipid nanoparticles.
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•A modified PGSS process with expansion into a water stream was developed.•The encapsulation of Vitamin B2 in solid lipid ...nanoparticles was tested.•Pressure, Vitamin B2 and surfactant concentrations and stabilizer MW were varied.•Best conditions were 15.0MPa, 2% Vitamin B2, 5% SLS and PEG MW of 35kDa.•Best particles had bioactive load of 0.54mg/g and mean particle size of 104nm.
Solid lipid nanoparticles (SLN) are spherical particles prepared from solid fats, which can be used as delivery systems by encapsulating bioactives. In this study, particles from gas-saturated solutions (PGSS) were produced by a modified process, using fully hydrogenated canola oil (FHCO) to encapsulate Vitamin B2, a hydrophilic bioactive. Four operating parameters were studied in terms of their influence on encapsulation efficiency, bioactive load and particle size: pressure (10.0–25.0MPa), Vitamin B2 concentration (0.25–2%, w/w), surfactant (sodium lauryl sulfate, SLS) concentration (1–7.5%, w/w) and stabilizer (polyethylene glycol, PEG) molecular weight (2,000–35,000Da). The optimal conditions were determined as 15.0MPa, 2% Vitamin B2, 5% SLS and 35,000Da PEG, resulting in an encapsulation efficiency of 12±0.03%, bioactive load of 0.54±0.05mg/g and bimodal particle size distribution with a main peak at 104±5.7nm, showing that it is possible to generate nano-scale solid lipid particles with a high content of a hydrophilic bioactive; however, further fine tuning is needed.
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•Formulation of insoluble drugs nimodipine, fenofibrate, and o-vanillin using PGSS™.•Melting points, gas solubility and interfacial tension of Brij S100.•Yield, mean particle size ...distribution, loading efficiency and dissolution rates.
PGSS™ process was applied to the carrier materials Brij S100 and polyethylene glycol PEG 4000 for the incorporation of the insoluble drugs nimodipine, fenofibrate, and o-vanillin with the purpose of improving their bioavailability and dissolution rate. Brij S100/CO2 system has been investigated in the first part. The system has an S-L-G (solid-liquid-gas) curve with a negative dP/dT slope, which indicates high CO2 solubility in the molten heavy component. Sorption of CO2 in Brij S100 is about 25% higher than in PEG 4000 under similar conditions, varying from 0.12 g CO2/g carrier at 5.87 MPa to 0.57 CO2/g carrier at 35 MPa. The values of the interfacial tension for the Brij S100/CO2 system are approximately 50% of those of the PEG 4000/CO2 system.
Influence of processing parameters on PGSS™ process yield, particle size distribution, loading efficiency and dissolution rates is presented in addition.
•Curcuminoids were extracted using different extraction methods.•Highest amount of extract was obtained using ethanol as solvent.•Antioxidant, antifungal and antibacterial activities of extracts have ...been measured.•The highest antioxidant activity was obtained from ethanol extract.•Curcuminoids have been encapsulated in PEG by PGSS™ process.
In this study, the isolation of curcuminoids from turmeric (Curcuma longa L.) was performed using different solvent extraction methods and solvents. Obtained extracts were analyzed for the contents of curcumin, demethoxycurcumin and bisdemethoxycurcumin by HPLC and the radical scavenging and antibacterial activities of extracts were determined. Extract with highest content of curcuminoids was mixed with polyethylene glycol (PEG) and formulated into powder using PGGS™ method. Obtained powder was pressed into tablets and a release study of the curcuminoids from the product was observed in simulated gastric and intestinal fluids.
Results show that the highest yield of extract is obtained using conventional extraction with mixing in ethanol giving the highest concentration of curcuminoids as well. All extracts show strong antifungal properties but weak antibacterial activity. Curcuminoids extract was successfully encapsulated in PEG carrier and a fine powder was obtained, which increased the solubility in aqueous media.
