Supercritical Fluid Technology Research Articles

Supercritical CH3OH-Triggered Isotype Heterojunction and Groups in g-C3N4 for Enhanced Photocatalytic H2 Evolution.

The structure tuning of bulk graphitic carbon nitride (g-C3N4) is a critical way to promote the charge carriers dynamics for enhancing photocatalytic H2-evolution activity. Exploring feasible post-treatment strategies can lead to effective structure tuning, but it still remains a great challenge. Herein, a supercritical CH3OH (ScMeOH) post-treatment strategy (250-300 °C, 8.1-11.8 MPa) is developed for the structure tuning of bulk g-C3N4. This strategy presented advantages of time-saving (less than 10 min), high yield (over 80%), and scalability due to the enhanced mass transfer and high reactivity of ScMeOH. During the ScMeOH post-treatment process, CH3OH molecules diffused into the interlayers of g-C3N4 and subsequently participated in N-methylation and hydroxylation reactions with the intralayers, resulting in a partial phase transformation from g-C3N4 into carbon nitride with a poly(heptazine imide)-like structure (Q-PHI) as well as abundant methyl and hydroxyl groups. The modified g-C3N4 showed enhanced photocatalytic activity with an H2-evolution rate 7.2 times that of pristine g-C3N4, which was attributed to the synergistic effects of the g-C3N4/Q-PHI isotype heterojunction construction, group modulation, and surface area increase. This work presents a post-treatment strategy for structure tuning of bulk g-C3N4 and serves as a case for the application of supercritical fluid technology in photocatalyst synthesis.

Analysis of Adaptability and Application Potential of Supercritical Multi-Source Multi-Component Thermal Fluid Technology for Offshore Heavy Oil in China

Supercritical multi-source, multi-component thermal fluid is a heavy oil thermal recovery method independently developed by China National Offshore Oil Co., Ltd (Beijing, China). It uses waste liquid at the production end of the production well as the water source, the injection medium temperature exceeds 374 °C, 22.1 MPa, and all the produced flue gas is re-injected. Compared with steam huff and puff technology, supercritical technology has the advantages of high enthalpy value, high heat utilization rate, good oil displacement effect, and being green and pollution-free. In addition, its oil–water treatment cost is low, it can realize the reuse of organic matter, it has a good cost advantage of water treatment under the background of low carbon, and it is a thermal recovery method with great application potential for offshore heavy oil. Therefore, it is necessary to carry out research on the adaptability and application potential of supercritical multi-source, multi-heat flow thermal recovery technology in the sea. Based on the laboratory one-dimensional displacement experiment, this paper reveals the mechanism of heavy oil supercritical multi-source multi-component thermal fluid displacement and the contribution of supercritical components to the displacement effect, and establishes the supercritical multi-source, multi-component thermal fluid numerical simulation characterization method. Combined with the characteristics of offshore heavy oil reserves, the main control factors affecting supercritical multi-source, multi-component thermal fluid development were established by numerical simulation and orthogonal test methods, and the adaptive screening method of offshore supercritical technology was established. The application potential of 670 million tons of offshore heavy oil reserves was evaluated and sorted, and KL 10-2 oilfield was selected as the pilot test oilfield. The results show that supercritical technology has great advantages in oil displacement and water treatment cost reduction, and the results play an important guiding significance for the development of offshore heavy oil technology system and the iteration of new technology.

Supercritical fluid technology for lupin hulls valorization: extraction and fractionation of lupeol

Supercritical fluid technology for lupin hulls valorization: extraction and fractionation of lupeol

New solubility model to correlate solubility of anticancer drugs in supercritical carbon dioxide and evaluation with Kruskal–Wallis test

Anti-cancer drugs are the result of human endeavor in search of a treatment for a deadly disease like cancer. The advent of the ideology of sustainability and eco-friendliness has propelled the manipulation of supercritical fluid technology in numerous fields. Beyond green technology, they account for the production of nanoparticles, due to which they are highly exploited for the production of anti-cancer drugs, making the existing technologies obsolete. Production of anticancer drugs through supercritical fluid technology requires the knowledge of anticancer drug as well as an efficient model to correlate its solubility in the supercritical fluid. Thus, in this work, a new model for correlating the solubility of anticancer drugs in supercritical carbon dioxide based on thermodynamic frame work has been proposed. Over eighteen important anticancer drugs are considered for evaluation. Further, five successful six-parameter models are considered to compare the performance of the new thermodynamic model. Various statistical parameters and Kruskal-Wallis test have been used to compare and evaluate the significance of the difference between the models in order to test the efficacy of the proposed model.

Increasing the bioavailability of curcumin using a green supercritical fluid technology-assisted approach based on simultaneous starch aerogel formation-curcumin impregnation

A green approach based on simultaneous starch aerogel formation-curcumin impregnation via supercritical fluid technology was used to increase the bioavailability of curcumin. The loading amounts of curcumin were 16.4, 21.4, and 24.9 mg/g of aerogel for the 25% Amyl-loaded, 55% Amyl-loaded, and 72% Amyl-loaded samples, respectively. Curcumin-loaded aerogels showed the eventual distribution of curcumin in the hydrophobic area of the internal structure of the aerogels. In vitro gastrointestinal release profiles demonstrated the enhanced curcumin release from the curcumin-loaded aerogel formulations produced by the SC-CO2 technology over free curcumin. After intestinal digestion, the percentage of released curcumin from 25% Amyl-loaded, 55% Amyl-loaded, and 72% Amyl-loaded was 7.2, 12.1, and 12.1%, respectively, while the release of native curcumin was only 0.5%. Caco-2 cell permeation studies revealed superior bioavailability of curcumin from the curcumin-loaded aerogels. Curcumin-loaded aerogels exhibited improved storage stability than free curcumin.

Thermodynamic Modeling of Solubility of Some Antibiotics in Supercritical Carbon Dioxide Using Simplified Equation of State Approach

Antibiotics are playing crucial role in the treatment of humans since the last few centuries. Their usage has several benefits along with side effects. The efficacy of antibiotics for the treatment of ailments may be retained by controlling the drug dosage. This may be achieved with supercritical fluid technology (SFT). The antibiotic drug solubility in supercritical carbon dioxide (scCO2) is available only at specific temperature and pressure conditions, for effective utilization of SFT, solubility at various conditions are required. Equation of state (EoS) method is used for solubility data modeling and it requires critical properties of the solute, molar volume of the solute and sublimation pressure of the solute along with fugacity coefficient, pressure and temperature. These properties are estimated using group contribution methods. For antibiotics solute critical properties, molar volume and sublimation pressure are unavailable and existing group contribution methods are also not applicable due to the lack of functional group contributions in their techniques. Thus, there is a need to address EoS methodology without using solute properties. Hence, a new EoS methodology for solubility modeling is, proposed without using critical properties of the solute, molar volume of the solute and vapour pressure of the solute. Thus, this study focuses on the development of new solubility model that correlates antibiotics using equation of state (EoS). Importantly, the proposed solubility model does not use the critical properties of the antibiotics. Correlating ability of the proposed model is indicated in terms of regression coefficient and arithmetic average relative deviation percentage (AARD %).

Formation of hollow solid lipid microparticles from natural waxes using supercritical carbon dioxide

AbstractIn this study, the potential of natural waxes, namely, candelilla wax (CLW) and carnauba wax (CW), was explored to form extra‐hard shell hollow solid lipid particles using a particle formation process based on supercritical fluid technology. Melting behavior and volumetric expansion of CLW and CW in pressurized CO2 were investigated as a function of pressure. The melting point of waxes decreased linearly with increasing pressures up to a certain level; then stayed constant regardless of further elevated pressures. The highest melting point depressions of 13.0% and 8.3% were observed for CLW and CW at 140 and 130 bar CO2 pressure, respectively. A positive correlation between the melting point depression and volumetric expansion was observed for both waxes. The volumetric expansion of waxes increased with increasing pressures within the linear range of the melting curves. The highest volumetric expansion was achieved at 140 bar/68°C and 130 bar/85°C for CLW (7.1%) and CW (8.5%), respectively. Hollow solid lipid particles with smooth surfaces were obtained from both CLW and CW. There was no difference between the melting behavior of the original waxes and their particles. Increasing SC‐CO2 pressure decreased the particle size and inner volume of the hollow particles. D[4,3] of CLW ranged between 9.3 and 25.4 μm, whereas it ranged between 8.7 and 34.2 μm for CW. CLW and CW were found to be suitable high‐melting lipids to form hollow solid lipid particles via SC‐CO2‐assisted particle formation process to develop hollow solid lipid particles with an extra‐hard protective shell.

RIBES FRAGRANS PALLAS: SUPERCRITICAL CO2 EXTRACTION AND TANDEM MASS SPECTROMETRY

Supercritical fluid technology was used to obtain bioactive substances from leaves of Ribes fragrans Pallas. The supercritical fluid technology proved to be the most effective type of extraction, giving the highest yield of metabolome composition of R. fragrans. Several experimental conditions were investigated in the pressure range 50–300 bar, with the used volume of co-solvent ethanol in the amount of 2.5% in the liquid phase at a temperature in the range of 31–70 °C. The most effective extraction conditions are: pressure 200 Bar and temperature 55 °C for leaves of R. fragrans. The CO2-extract of leaves of R. fragrans contain various polyphenolic compounds and compounds of other chemical groups with valuable biological activity. For the first time, the metabolome of supercritical extracts of R. fragrans leaves was studied in this research. Tandem mass-spectrometry (HPLC-ESI – ion trap) was applied to detect target analytes. The four-stage ion separation mode was implemented 79 different bioactive components have been identified in R. fragrans extracts. Twenty chemical compounds from polyphenol group and twelve chemical compounds from other chemical groups were identified for the first time in genus Ribes.

Alginate aerogels by spray gelation for enhanced pulmonary delivery and solubilization of beclomethasone dipropionate

Aerogel technology is an emerging platform that offers alternative and cost-effective dry carriers with advanced performances for the pharmaceutical industry. The innovative combination of compressed air-assisted spray gelation and “green” supercritical fluid (SCF) technology was used in this study to produce alginate aerogel microparticles with adequate properties for pulmonary drug delivery. Beclomethasone dipropionate (BDP), a poorly water-soluble anti-inflammatory drug for asthma treatment, was loaded into alginate aerogel particles by SCF-assisted impregnation ensuring high loading, as well as the amorphization of the drug. The production of aerogels was optimized through the fine-tuning of parameters in compressed air-assisted spray gelation, specifically adjusting the air flow rate and the pump speed. Alginate aerogels were aimed to be produced with an appropriate aerodynamic diameter from 1 to 5 µm, measured by in vitro deposition tests with Next Generation impactor and potential for deep lung penetration. Nuclear magnetic resonance (NMR) relaxometry was used to assess aerogel hydration and unveiled structure–property relationships leading to the sudden release of the drug. Finally, in vitro cytotoxicity tests in fibroblasts and ex vivo permeability tests were conducted. These biological tests confirmed the excellent biocompatibility of the aerogel formulations and demonstrated the efficient deposition of BDP in porcine bronchial tissues assisted by the porous alginate aerogel carrier.

Encapsulation Methods and Releasing Mechanisms of Encapsulated Active Drug

Substances of plant origin are chemically unstable and easily oxidized by external conditions. However, they have to remain in their bioactive form when they are used in food, pharmaceutical, nutraceutical and cosmetic industries. Encapsulation method is an effective technique that should protect them preventing the degradation of these active substances and thus prevent them from losing their activities.
 In this review, the strategies for encapsulating plant substances and their preparation methods including emulsification, atomization, coaxial electrospray system, lyophilization, coacervation, in situ polymerization, melt extrusion, supercritical fluid technology, fluidized bed coating etc. were discussed. The release mechanisms of plant active substances were also presented.
 The choice of an appropriate encapsulation technique and wall material depends on the final use of the product and the processing conditions involved. The use of liposomes, ethosomes, phytosomes, emulsions, microspheres, microcapsules, solid lipid nanoparticles including formulations based on plant substances has enhanced their therapeutic effects. With the use of all these encapsulation systems, the formulation is delivered in a targeted manner, giving it an on-site effect, and the bioavailability of the formulation is also improved. With these new drug delivery systems, actives and extracts used in herbal formulations exhibit improved stability, sustained release from the formulation, protection against toxicity, and improved therapeutic efficacy.
 Keywords : nanoparticles, bioactive substance, formulation

Solvent-Free Method for Masking the Bitter Taste of Azithromycin Dihydrate Using Supercritical Fluid Technology

ABSTRACT Introduction and purpose The unpleasant extremely bitter taste of the orally administered broad-spectrum antibiotic azithromycin decreases patient compliance, especially in pediatrics. This issue can be overcome by decreasing drug interaction with the tasting buds using insoluble polymers at salivary pH (6.8 -7.4), like the cationic polymer Eudragit EPO. Supercritical fluid technology is a green synthesis method for preparing pharmaceutical preparations that replace organic solvents with safe supercritical CO2. This study aimed to mask the bitter taste of azithromycin using the supercritical fluid method and a pH-sensitive Eudragit EPO polymer. Methods: A foaming process was investigated for preparing a formulation (TEST), which comprises treating the polymer with supercritical carbon dioxide (CO2) fluid to prepare a taste-masked dosage form without employing organic solvents or flavors. Results: The use of the supercritical technique at 40 °C and 10 MPa for two hours allowed the manufacturing of solvent-free polymeric foam with azithromycin dispersions; the average calculated percentage of apparent volume change was 62.5 ± 5.9% with an average pore diameter of 34.879 Å. The formulated sample showed low drug release in simulated salivary fluid while keeping its crystalline nature. Moreover, clinical studies on healthy subjects showed that the formula successfully masked azithromycin's bitter taste. Conclusions: Overall, it has been shown herein that the supercritical fluid technology foaming method is promising in masking the bitter taste of bitter ingredients.

Supercritical CO2 technology for the treatment of end-of-life lithium-ion batteries

Supercritical fluid technology is a promising approach for sustainable and efficient resource recovery (especially fluorinated binders and electrolytes) from end-of-life lithium ion batteries with significant economic and environmental perspectives.

Supercritical fluid and cocrystallization technologies for designing antimicrobial food packaging PLA nanocomposite foams loaded with eugenol cocrystals with prolonged release

Searching for effective strategies to modify the release rate of essential oil derivatives is one of the main challenges in designing prolonged-release antimicrobial food packaging materials. Herein, supercritical fluid technology and cocrystallization engineering were used to develop novel eugenol (EU) prolonged-release poly (lactic acid) (PLA) nanocomposite foams. Eugenol-phenazine (EU-PHE) cocrystals, produced by a solvent-free mechanochemical method, were incorporated by supercritical solvent impregnation (SSI) inside PLA nanocomposite foams with different contents of Cloisite30B® (C30B). The effect of the cocrystallization process and C30B content on the EU release kinetics and its relation with their antimicrobial activity by direct contact (anti-attachment) and release in broth culture were studied. The deposition of isolated spherical-shaped micrometric EU-PHE cocrystal particles with 0.8 µm average diameter inside the pores of PLA foams was evidenced by XRD, SEM, DSC, and TGA analyses. The release mechanism of EU and its cocrystal was defined as a quasi-Fickian diffusion process successfully described by the Korsmeyer-Peppas model with release rate constants up to 3.6-fold lower than the release rate constant of pure EU. The impregnated foam samples completely inhibited the attachment of Listeria monocytogenes and Salmonella Enteritidis and provided prolonged antimicrobial activity in broth culture against both food-borne pathogens. This study suggests a new, environmentally friendly method for designing prolonged-release antimicrobial food packaging materials.

Supercritical fluid technology as a strategy for nifedipine solid dispersions formulation: In vitro and in vivo evaluation

Supercritical fluid technology (SFT) is an insufficiently investigated approach for the production of solid dispersions, it is environmentally acceptable and has a high potential for application in the pharmaceutical industry. The aim of this work was to formulate and characterize nifedipine solid dispersions (SDs) produced by the SFT and compare the results with ones obtained by the classical solvent based kneading method. The following in vitro tests were conducted: assay and yield, solvent residues, solid state characterization (FTIR, DSC, XRD), flowability, hygroscopicity, solubility, dissolution and stability. Additionally, bioavailability was examined on an animal model (Wistar rats). The formulation selection for in vivo study was performed using the multilevel categoric experimental design and the health risk assessment. Solid state characterization revealed that formulation obtained by the SFT method and higher ratio of polymer (1:5) have had nifedipine in completely amorphous form. Polymer ratio and method of SDs preparation do influence the investigation characteristics. Dissolution rate was fastest in SDs prepared by the SFT and higher polymer ration (1:5). In vivo data of selected SDs prepared by the kneading (ratio 1:1) and the SFT (ratio 1:5) showed alteration in pharmacokinetic profile after i.v. and p.o. application.

Value-Added Green Processing of Tomato Waste to Obtain a Stable Free-Flowing Powder Lycopene Formulation Using Supercritical Fluid Technology

Value-Added Green Processing of Tomato Waste to Obtain a Stable Free-Flowing Powder Lycopene Formulation Using Supercritical Fluid Technology

Recent Patents on Solid Dispersions Emphasize Promising Benefits in Solubility Enhancement of Poorly Water-soluble Drugs.

In the development of drug delivery systems, drugs' solubility remains the most challenging constraint. Many newly synthesized chemical compounds are available, but they involve low solubility and poor permeability restrictions. Among various drug delivery systems, the utilization of solid dispersion technologies has become more focused due to their promising benefits. This technology has attracted extensive attention for dissolution rate improvement along with substantial bioavailability enhancement of poorly water-soluble drug candidates. Many approaches have been employed for preparing solid dispersions, such as the melting method, hot melt extrusion, solvent evaporation process, fusion and kneading method, spray drying technique, co-grinding and freeze drying, supercritical fluid technology, etc. Result: A wide variety of hydrophilic and hydrophobic materials are available as carriers, which are employed in the formulation of solid dispersions. Depending on the carrier characteristics, immediate- release solid dispersions and/or controlled-release solid dispersions can be formulated. Multiple hydrophilic materials have been explored for heightening dissolution features with enhanced bioavailability of poorly water-soluble drug molecules. The availability of commercially available products further validates the utility of solid dispersion technology in drug delivery systems. In the current manuscript, an attempt has been made to highlight the comprehensive development techniques, characterization techniques, recent solid dispersion technologies, clinical trial studies, and patented technology, along with studies heightening the dissolution behavior of numerous poorly aqueous soluble drugs. The major stability issues affecting the suitability of solid dispersions are also discussed.

HPMCAS-Based Amorphous Solid Dispersions in Clinic: A Review on Manufacturing Techniques (Hot Melt Extrusion and Spray Drying), Marketed Products and Patents.

Today, therapeutic candidates with low solubility have become increasingly common in pharmaceutical research pipelines. Several techniques such as hot melt extrusion, spray drying, supercritical fluid technology, electrospinning, KinetiSol, etc., have been devised to improve either or both the solubility and dissolution to enhance the bioavailability of these active substances belonging to BCS Class II and IV. The principle involved in all these preparation techniques is similar, where the crystal lattice of the drug is disrupted by either the application of heat or dissolving it in a solvent and the movement of the fine drug particles is arrested with the help of a polymer by either cooling or drying to remove the solvent. The dispersed drug particles in the polymer matrix have higher entropy and enthalpy and, thereby, higher free energy in comparison to the crystalline drug. Povidone, polymethaacrylate derivatives, hydroxypropyl methyl cellulose (HPMC) and hydroxypropyl methylcellulose acetate succinate derivatives are commonly used as polymers in the preparation of ASDs. Specifically, hydroxypropylmethylcellulose acetate succinate (HPMCAS)-based ASDs have become well established in commercially available products and are widely explored to improve the solubility of poorly soluble drugs. This article provides an analysis of two widely used manufacturing techniques for HPMCAS ASDs, namely, hot melt extrusion and spray drying. Additionally, details of HPMCAS-based ASD marketed products and patents have been discussed to emphasize the commercial aspect.

Creation of porous synthetic matrices of polylactic acid (PLA) with ibuprofen impregnation using supercritical fluid

The synthesis of highly porous biosoluble polymer matrices using supercritical and subcritical fluid technologies is a promising direction in the development of functional materials for modern tissue engineering and regenerative medicine. The subject of the article is the pore formation, the creation of composite polymer matrices and the impregnation of medicinal substances into the resulting structures using supercritical fluids, as well as the identification of patterns of influence of thermodynamic parameters on the physical properties of the resulting structures. Experimental studies were carried out on the creation of PLA polymer implants, composites of PLA-hydroxyapatite HAP with impregnation into the resulting ibuprofen matrix. The obtained samples were studied using spectral methods of analysis and differential scanning calorimetry.

The In Vitro, In Vivo, and PBPK Evaluation of a Novel Lung-Targeted Cardiac-Safe Hydroxychloroquine Inhalation Aerogel.

Hydroxychloroquine (HCQ) was repurposed for COVID-19 treatment. Subtherapeutic HCQ lung levels and cardiac toxicity of oral HCQ were overcome by intratracheal (IT) administration of lower HCQ doses. The crosslinker-free supercritical fluid technology (SFT) produces aerogels and impregnates them with drugs in their amorphous form with efficient controlled release. Mechanistic physiologically based pharmacokinetic (PBPK) modeling can predict the lung's epithelial lining fluid (ELF) drug levels. This study aimed to develop a novel HCQ SFT formulation for IT administration to achieve maximal ELF levels and minimal cardiac toxicity. HCQ SFT formulation was prepared and evaluated for physicochemical, in vitro release, pharmacokinetics, and cardiac toxicity. Finally, the rat HCQ ELF concentrations were predicted using PBPK modeling. HCQ was amorphous after loading into the chitosan-alginate nanoporous microparticles (22.7±7.6 μm). The formulation showed a zero-order release, with only 40% released over 30 min compared to 94% for raw HCQ. The formulation had a tapped density of 0.28 g/cm3 and a loading efficiency of 35.3±1.3%. The IT administration of SFT HCQ at 1 mg/kg resulted in 23.7-fold higher bioavailability, fourfold longer MRT, and eightfold faster absorption but lower CK-MB and LDH levels than oral raw HCQ at 4 mg/kg. The PBPK model predicted 6 h of therapeutic ELF levels for IT SFT HCQ and a 100-fold higher ELF-to-heart concentration ratio than oral HCQ. Our findings support the feasibility of lung-targeted and more effective SFT HCQ IT administration for COVID-19 compared to oral HCQ with less cardiac toxicity. Graphical abstract.

An approach to enhance carbon/polymer interface compatibility for lithium-ion supercapacitors

Developing high-efficiency and easy machining components, as well as high-performance energy storage components, is a pressing issue on the road to economic and social progress. Optimizing the interface compatibility between composites and promoting the efficient utilization of the electrochemical active sites are crucial factors in improving the electrochemical performance of composite electrode materials. To address this challenge, a carbon-based flexible lithium-ion supercapacitor positive material (Polyaniline @ Carbon Foam-Supercritical carbon dioxide (P@C-SC)) is synthesized using commercial melamine foam and aniline monomer. The synthesis process utilizes supercritical fluid technology, effectively solving the interface compatibility problem between the composite materials. Consequently, the electrochemical performance of the composite electrode materials is significantly improved. The supercapacitive properties of this material are investigated in 1 mol/L sulfuric acid (H2SO4) and lithium sulfate (Li2SO4) electrolytes using a three-electrode system. In H2SO4 electrolyte, the material exhibits a working voltage of up to 2.2 V and a specific capacitance of 898F/g (at 1 A/g), resulting in a maximum energy density of 50.8 Wh kg−1. Furthermore, this electrode demonstrates superior lithium storage performance, with a specific capacity of approximately 900 mAh/g (at 1 A/g) and a retention of about 400 mAh/g after 200 cycles, along with a coulomb efficiency of 100%. This work offers insights into the integrated design of composite materials with improved electrochemical properties and interface compatibility, thus providing potential applicability of supercritical fluids in the field of lithium-ion supercapacitors.