Supercritical CO2 Technology Research Articles

Synthesis of surface-modified iron oxide nanocrystals using supercritical carbon dioxide as the reaction field.

In the synthesis of surface-modified nanocrystals (NCs), a simple and green chemistry approach to reduce liquid waste, particularly a solventless process, has been desired. In this study, we applied the supercritical CO2 technology, which is an excellent solventless process, to the synthesis of surface-modified iron oxide NCs. The synthesis was performed at 30.0 ± 0.8 MPa of CO2, 18 h and 100 °C, where iron(iii) acetylacetonate, pure water and decanoic acid were used as starting materials. As a result, the supercritical CO2 medium gave the NCs of α-Fe2O3 and γ-Fe2O3 with unimodal size distribution, where the mean size was 7.8 ± 2.0 nm. In addition, they were self-assembled on the TEM substrate and the mean nearest-neighbor spacing was close to the chain length of decanoic acid. Furthermore, FT-IR and TG analyses indicate that decanoic acid chemically attaches to the surface of iron oxide NCs that are dispersed in cyclohexane. These results suggest that the supercritical CO2 medium could be the new appealing reaction field to fabricate densely modified NCs without liquid waste.

Seed Oil Quality and Cultivation of Sambucus williamsii Hance as a New Oil Crop.

Natural edible oil derived from wild non-cultivated oil crops contributed to human daily nutritional diversity and disease prevention. It was important to investigate the nutritional value of these oils and the feasibility of crop cultivation. The present study focused on the assessment of seed oil quality of Sambucus williamsii Hance (SWH) and its molecular breeding. Wild SWH seed oil was extracted by supercritical CO2 technology and the composition of the oil was determined by using gas chromatography mass spectrometry (GC-MS) analysis. The oil content of SWH seeds reaches around 40%. Its seed oil was found to be rich in unsaturated fatty acids, such as 24.24% of linolenic acid and 50.56% of linoleic acid, and vitamin E (25.92 mg kg−1). The cytotoxicity and heavy metal analysis showed SWH seed oil was safe for consumption. In addition, the SWH strains with excellent characteristics were screened out for cultivation according to genetic diversity and morphological analysis. Amplified fragment length polymorphism (AFLP) markers were used to evaluate the genetic diversity of 28 accessions of wild SWH seeds and 5 accessions were selected to cultivate. Among them, two strains of SWH (sample 3 and 6) with high yielding (275.7 and 266.8 area yield kg−1) were suitable for dense planting and could be used to establish the raw material forest of SWH seed oil. The results of this study indicated the potential of development of selected SWH as novel oil crops and their wide cultivation.

Combined sterilization and fabrication of drug-loaded scaffolds using supercritical CO2 technology

The access of biodegradable scaffolds to the clinical arena is constrained by the absence of a suitable sterilization technique for the processing of advanced polymeric materials. Sterilization with supercritical CO2 (scCO2) may circumvent some technological limitations (e.g., low temperature, no chemical residues on the material), although scCO2 can plasticize the polymer depending on the processing conditions used. In this latter case, the integration of the manufacturing and sterilization processes is of particular interest to obtain sterile and customized scaffolds in a single step. In this work, scCO2 was exploited as a concomitantly foaming and sterilizing agent for the first time, developing a one-step process for the production of vancomycin-loaded poly(ε-caprolactone) (PCL) bone scaffolds. The effect of the CO2 contact time on the sterility levels of the procedure was investigated, and the sterilization efficiency was evaluated against dry spores (Bacillus stearothermophilus, Bacillus pumilus and Bacillus atrophaeus). Vancomycin-loaded PCL scaffolds had relevant sustained release profiles for the prophylaxis of infections at the grafted area, even those caused by methicillin-resistant Staphylococcus aureus (MRSA). The biological performance of the scaffolds was evaluated in vitro regarding human mesenchymal stem cells (hMSCs) attachment and growth. Finally, the biocompatibility and angiogenic response of the manufactured sterile scaffolds was assessed in ovo through chick chorioallantoic membrane (CAM) assays.

Cover Image, Volume 138, Issue 44

The cover image created by Zheng Zhao and his colleagues shows an SEM micrography of sodium alginate (SA)/silk fibroin (SF) composite scaffolds with extracellular matrix (ECM)-like nanofibrous structures developed by supercritical CO2 technology. And the SA microparticles are embedded in the SF scaffolds. Increasing the SA content can improve the mechanical properties of the SF scaffolds and reduce the porosity of the SF scaffolds. Moreover, the SA microparticles can regulate the degradation rate of the SA/SF composite scaffolds. In addition, the SA/SF composite scaffolds exhibit higher L929 fibroblasts attachment and proliferation ability than the SF scaffolds. DOI: 10.1002/app.51421

Fully supercritical CO2 preparation of a nanostructured MOF composite with application in cutaneous drug delivery

Supercritical CO2 (scCO2) technology is used here as an efficient method to assist in the preparation of a cutaneous polymeric formulation based on drug containing metal-organic framework composites. The supercritical fluid is used in three steps: (i) as a drying agent for the nanosized mesoporous matrix, (ii) as the impregnation vector of a topical antibiotic drug, and (iii) as a plasticizing and foaming fluid to obtain dispersions of the hybrid material into a biocompatible polymer, e.g., the macroporous patch. The materials were characterized using solid state techniques. The drug delivery and permeation profiles of the patches were investigated applying in vitro and ex vivo tests by using porcine skin. These analyses suggest that scCO2 impregnation is an easy and fast strategy to prepare composite devices able to progressively release and diffuse the incorporated drug throughout the skin, paving the way to efficiently prepare cutaneous devices for topical or systemic therapies.

Valorization of Fermented Shrimp Waste with Supercritical CO2 Conditions: Extraction of Astaxanthin and Effect of Simulated Gastrointestinal Digestion on Its Antioxidant Capacity.

Lactic acid fermentation increases the bioactive properties of shrimp waste. Astaxanthin is the principal carotenoid present in shrimp waste, which can be found esterified in the liquid fraction (liquor) after its lactic acid fermentation. Supercritical CO2 technology has been proposed as a green alternative to obtain astaxanthin from fermented shrimp waste. This study aimed to optimize astaxanthin extraction by supercritical CO2 technology from fermented liquor of shrimp waste and study bioaccessibility using simulated gastrointestinal digestion (GD) of the optimized extract. A Box–Behnken design with three variables (pressure, temperature, and flow rate) was used to optimize the supercritical CO2 extraction. The optimized CO2 extract was obtained at 300 bar, 60 °C, and 6 mL/min, and the estimated characteristics showed a predictive extraction yield of 11.17%, antioxidant capacity of 1.965 mmol of Trolox equivalent (TE)/g, and astaxanthin concentration of 0.6353 µg/g. The experiment with optimal conditions performed to validate the predicted values showed an extraction yield of 12.62%, an antioxidant capacity of 1.784 mmol TE/g, and an astaxanthin concentration of 0.52 µg/g. The astaxanthin concentration decreased, and the antioxidant capacity of the optimized extract increased during gastrointestinal digestion. In conclusion, our optimized supercritical CO2 process is suitable for obtaining astaxanthin from shrimp by-products after lactic acid fermentation.

Supercritical carbon dioxide assisted fabrication of biomimetic sodium alginate/silk fibroin nanofibrous scaffolds

AbstractIn this study, biomimetic sodium alginate (SA)/silk fibroin (SF) scaffolds were successfully fabricated by supercritical CO2technology. The SA/SF scaffolds exhibited an interconnected porous and extracellular matrix (ECM)‐like nanofibrous structures. Moreover, the SA microparticles were embedded in the SF scaffolds. Increasing the content of SA microparticles could improve tensile strength and compressive strength of the SF scaffolds and reduce the porosity of the SF scaffolds. The addition of the SA microparticles could also regulate the degradation rate of the SA/SF scaffolds. Furthermore, the results of in vitro biocompatibility evaluation, indicated that the SA/SF scaffolds exhibited no obvious cytotoxicity and higher cell adhesion ability and were more favorable for L929 fibroblasts proliferation than pure SF scaffolds. Therefore, the SA/SF scaffolds with ECM‐like nanofibrous and interconnected porous structure have potential application in skin tissue engineering.

Supercritical CO2 extraction, structural analysis and bioactivity of polysaccharide from Grifola frondosa

Polysaccharide was extracted from Grifola frondosa with supercritical CO2 technology. The optimum extraction conditions for the highest yield were determined by Box-Behnken design: the pressure was 34.5Mpa, the extraction temperature was 36.7 ℃, the extraction time was 116.3 min and the ratio of entrainer to raw material was 2.86 mL/g, to give a polysaccharide yield of 4.61 %. The polysaccharide from G. frondosa was purified with ionic liquid. The polysaccharide was characterised as a predominantly heteropolysaccharide composed of different monosaccharides with a β - type structure. The anti-tumour and antibacterial experiments on the polysaccharide in vitro showed that the polysaccharide had marked anticancer and antibacterial effects.

Supercritical CO2 technology for one-pot foaming and sterilization of polymeric scaffolds for bone regeneration

Sterilization is a quite challenging step in the development of novel polymeric scaffolds for regenerative medicine since conventional sterilization techniques may significantly alter their morphological and physicochemical properties. Supercritical (sc) sterilization, i.e. the use of scCO2 as a sterilizing agent, emerges as a promising sterilization method due to the mild operational conditions and excellent penetration capability. In this work, a scCO2 protocol was implemented for the one-pot preparation and sterilization of poly(ε-caprolactone) (PCL)/poly(lactic-co-glycolic acid) (PLGA) scaffolds. The sterilization conditions were established after screening against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) vegetative bacteria and spores of Bacillus stearothermophilus, Bacillus pumilus and Bacillus atrophaeus. The transition from the sterilization conditions (140 bar, 39 °C) to the compressed foaming (60 bar, 26 °C) was performed through controlled depressurization (3.2 bar/min) and CO2 liquid flow. Controlled depressurization/pressurization cycles were subsequently applied. Using this scCO2 technology toolbox, sterile scaffolds of well-controlled pore architecture were obtained. This sterilization procedure successfully achieved not only SAL-6 against well-known resistant bacteria endospores but also improved the scaffold morphologies compared to standard gamma radiation sterilization procedures.

Supercritical CO2 extraction of oil from Arctic charr side streams from filleting processing

Although Arctic charr side streams contain limited amounts of fish flesh, they are a rich fish oil source (46.3 ± 0.6%). The aim of the study was to investigate the potential for valorization of Arctic charr filleting side streams through the extraction of oil by supercritical CO2 technology. The effect of temperature (40 °C and 80 °C) and pressure (20, 35 and 45 MPa) on the final extract after supercritical fluid extraction (SFE) was evaluated. Temperature increase enhanced the yield but decreased the antioxidant activity at 45 MPa, did not affect the yield and the antioxidant activity at 35 MPa, whereas yield was limited at 20 MPa and 80 °C. Extracts were rich in monounsaturated fatty acids (56.7–58.3%, especially oleic acid 37.2–38.0%), and polyunsaturated fatty acids (20.2–26.1%, especially DHA 7.3–11.4%). The presence of astaxanthin significantly preserved the extracts from oxidation. Industrial relevanceSupercritical carbon dioxide extraction is a green technology appropriate for the recovery of non-polar and heat sensitive compounds. The extracted Arctic charr oils were rich in polyunsaturated fatty acids and astaxanthin which inhibited oxidation in combination with the absence of oxygen and light during the process. This technology could be an excellent alternative for more sustainable valorization of fish processing side streams.

Separation and recognition characteristics by MIP manufacture using supercritical CO2 technology

This research is focused on the experiment of molecular imprinting polymers by supercritical solvent technology as friendly-environmental process. Methyl methacrylate (MMA) monomer, methacrylic acid (MAA) monomer, VA (vanillic acid) with template and EGDMA (ethylene glycol dimethacrylate) with cross-linking agent were used for molecular imprinting polymers composition. The template has been eliminated by the Soxhlet extraction method, and the rate of elimination is ca. 95–98 %. The adsorption capacities of the synthesized molecular imprinting polymers were estimated using the kinetics and isotherms of restraint, Scatchard investigation, affinity distributions, the materials adsorption with template-like structure, α (selectivity parameter), and HPLC (high performance liquid chromatography) analysis. The evaluation result shows that the manufactured molecular imprinting polymers have highly selectivity and separation ability. It was also confirmed that there was a difference between the adsorption amounts with EGDMA contents. In this study, prepared molecular imprinting polymers had an advantage in adsorption selectivity where VA and its structural analog materials are present. These results show that the molecular imprinting polymers selectivity was increased using control the cross-linking agent.

Recycling Waste Cotton Cloths for the Isolation of Cellulose Nanocrystals: A Sustainable Approach.

There is an interest in the sustainable utilization of waste cotton cloths because of their enormous volume of generation and high cellulose content. Waste cotton cloths generated are disposed of in a landfill, which causes environmental pollution and leads to the waste of useful resources. In the present study, cellulose nanocrystals (CNCs) were isolated from waste cotton cloths collected from a landfill. The waste cotton cloths collected from the landfill were sterilized and cleaned using supercritical CO2 (scCO2) technology. The cellulose was extracted from scCO2-treated waste cotton cloths using alkaline pulping and bleaching processes. Subsequently, the CNCs were isolated using the H2SO4 hydrolysis of cellulose. The isolated CNCs were analyzed to determine the morphological, chemical, thermal, and physical properties with various analytical methods, including attenuated total reflection-Fourier transform-infrared spectroscopy (ATR-FTIR), field-emission scanning electron microscopy (FE-SEM), energy-filtered transmission electron microscopy (EF-TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results showed that the isolated CNCs had a needle-like structure with a length and diameter of 10–30 and 2–6 nm, respectively, and an aspect ratio of 5–15, respectively. Additionally, the isolated CNCs had a high crystallinity index with a good thermal stability. The findings of the present study revealed the potential of recycling waste cotton cloths to produce a value-added product.

Density and viscosity of mixtures of glycerol acetates saturated with CO2 for the design of a supercritical fractionation column

Supercritical CO2 technology has a great potential for the fractionation of glycerol acetates (mono, di, and triacetyl glycerol) according to the quality standards of the food and cosmeceutical sectors. The design of fractionation columns requires a robust thermodynamic model for phase-equilibrium and PVT predictions, as well as proper correlations for physical properties like viscosity. In this work, we measure volumetric and rheological properties of mixtures of glycerol acetates saturated with CO2 (up to 70 mol%) in the temperature range 298−323 K. The mixture molar volumes are between 75 mL/mol and 135 mL/mol, while the viscosities between 0.9 mPa.s and 20 mPa.s. Results show that assuming ideal solution behaviour to estimate the physical properties has a major impact on the design of the fractionation.

Breath figures makes porous the “so-called” skin layer obtained in polymer foams prepared by supercritical CO2 treatments

In this article, the preparation of porous polymeric scaffolds of the synthetic poly (isopropylideneglycerol methacrylate) (PIPGMA) is described combining two complementary techniques. Supercritical CO2 (SCCO2), has been used as foaming agent to obtain internal porosity by varying parameters such as pressure and depressurization time. However, the disadvantage of SCCO2 technology is the formation of a non-porous skin layer described in the majority of the samples. This skin layer was modified by the breath figures technique (BF), providing superficial porosity to the polymeric sample. The result of using both techniques subsequently showed the formation of a porous network throughout the samples with inner and outer pores interconnected, characterized by scanning electron microscopy (SEM), micro X-ray computerized tomography scanning (micro CT), and processing those images with Image J. Finally, preliminary biological evaluation of the porous samples has been carried out in order to evaluate the biocompatibility and cellular viability of these scaffolds.

Supercritical CO2 Processing of a Functional Beverage Containing Apple Juice and Aqueous Extract of Pfaffia glomerata Roots: Fructooligosaccharides Chemical Stability after Non-Thermal and Thermal Treatments

The effects of supercritical CO2 processing on the chemical stability of fructooligosaccharides (FOS) and other functional and nutritional compounds were evaluated employing non-thermal and thermal approaches. Apple juice was enriched with Pfaffia glomerata roots aqueous extract due to its high content of short-chain FOS and then subjected to different levels of temperature (40 and 60 °C), pressure (8 and 21 MPa), and CO2 volume ratio (20 and 50%). The percentage of CO2 volume was evaluated concerning the total volume of the high-pressure reactor. Also, the functional beverage was thermally treated at 105 °C for 10 min. Physicochemical properties (pH and soluble solid content), beta-ecdysone, sugars (glucose, fructose, and sucrose), and FOS (1-kestose, nystose, and fructofuranosylnystose) content were determined. The pH and soluble solid content did not modify after all treatments. The pressure and CO2 volume ratio did not influence the FOS content and their chemical profile, however, the temperature increase from 40 to 60 °C increased the nystose and fructofuranosylnystose content. High-temperature thermal processing favored the hydrolysis of 1-kestose and reduced the sucrose content. Regarding beta-ecdysone, its content remained constant after all stabilization treatments demonstrating thus its high chemical stability. Our results demonstrated that supercritical CO2 technology is a promising technique for the stabilization of FOS-rich beverages since the molecular structures of these fructans were preserved, thus maintaining their prebiotic functionality.

Comparative Study between Supercritical Carbondioxide Fluid Technology and Conventional Water-based Processing to Dye Minor Elastin Containing Cotton Fabrics

ABSTRACT The need for an environmentally friendly tool in textile production is the major concern of consumers and traders. The current study is aimed to use supercritical CO2 technology to improve dyeing of minor elastin containing cotton using CI. Reactive Blue 222 and CI. Direct Black 112 dyes. For this purpose, several minor elastin containing cotton were pretreated with both conventional water and supercritical CO2 methods. Physical properties such as mass per unit area, tensile strength, tear strength, and elasticity of these fabrics are studied. Obtained results show that the supercritical CO2 pre-treatment affects some of the physical parameters. Furthermore, the obtained results are very promising as they prove that it is possible to dye various base-cotton fabrics in supercritical CO2 medium with a very satisfying quality in terms of uniformity and conformity.

Extraction of pumpkin peel extract using supercritical CO2 and subcritical water technology: Enhancing oxidative stability of canola oil

In this study, subcritical water extraction (SWE) and the supercritical fluid extraction (SFE) methods were used for the extraction of pumpkin peel extract. Total phenolic content and carotenoid compounds of extracts were measured. The extracts were added to canola oil at a concentration of 400 ppm and were stored at 30 °C for 60 days. The peroxide, carbonyl and acid values of the oil samples were measured, then compared with 100 ppm of tert-butylhydroquinone (TBHQ) synthetic antioxidants. The results showed that the total phenol content of obtained extract by SFE (353.5 mg GA/100 g extract) was higher than by SWE (213.6 mg GA/100 g extract), while the carotenoid content was higher for obtained extract by SWE (15.22 mg/100 g extract) compared to SFE (11.48 mg/100 g extract). The result of oil oxidation showed that the oxidative stability of the oil containing the mixed extract (SFE–SWE) is higher than the separate extract, consequently showing higher performance in preventing oil oxidation compared to TBHQ.

Supercritical CO2 and subcritical water technologies for the production of bioactive extracts from sardine (Sardina pilchardus) waste

The valorization of sardine (Sardina pilchardus) waste (SW) from a canning facility has been investigated within a biorefining approach. Sequential fractionation of SW into its constituents has been carried out using green solvents such as supercritical carbon dioxide (SCCO2) and subcritical water (sCW). The lipid fraction has been isolated through supercritical fluid extraction (SFE) with SCCO2 at 250 bar and 40 °C, yielding 20.3 ± 0.2 g oil/100 g SW with up to 17.2 %wt. omega-3 polyunsaturated fatty acids (PUFAs). Aiming at the protein fraction, sCW extraction/hydrolysis has been carried out at different temperatures (90, 140, 190 and 250 °C), using both SW and defatted sardine waste (DSW) from SFE experiments. Previous defatting increased protein recovery and purity. Bioactive properties of the fish protein hydrolysates (FPHs) obtained were affected by the extraction temperature. The highest antioxidant activity and in vitro antiproliferative effect were found in the extracts obtained at 250 °C.

Supercritical fluid assembly of albendazole liposomes targeting gastrin-releasing peptide receptor overexpressing tumors.

Aim: To develop albendazole (ABZ)-loaded bombesin(6-14) (BBN(6-14)) functionalized liposomes for targeting GRPR to enhance delivery to cancer cells. Materials & methods: ABZ-loaded liposomes were formulated using supercritical CO2 technology; functionalized with a GRPR-targeted lipid-anchored BBN(6-14) peptide; and evaluated for effects on cell viability, particle size and targeted cell uptake. Results: BBN(6-14)-coated ABZ liposomes decreased cell viability compared with nonfunctionalized ABZ liposomes. The level of GRPR expression positively correlated with intracellular uptake and decreased cell viability. The reduced cell viability, higher cell uptake and GRPR expression were observed in the order PC-3 > Caco-2 > HepG2 cells. Conclusion: BBN(6-14)-functionalized ABZ liposomes showed enhanced reduction in cell viability compared with nonfunctionalized ABZ liposomes.

Design and processing of drug delivery formulations of therapeutic deep eutectic systems for tuberculosis

Therapeutic deep eutectic systems (THEDES) emerged as alternative therapeutic agents that can enhance the bioavailability of the currently used active pharmaceutical ingredients. The use of THEDES in combination with supercritical CO2 has started to be explored to formulate drug delivery systems through green technology. This work aimed to develop THEDES-delivery systems for tuberculosis therapy, by encapsulating l-arginine-based THEDES in a lipidic matrix, through supercritical CO2 technology. From the phase equilibrium study of THEDES and CO2, PGSS was selected for THEDES encapsulation. Herein, THEDES encapsulation through PGSS was accomplished for the first time, with an average encapsulation efficiency of 75 %. The influence of the THEDES water-content in PGSS processing was also studied, suggesting no interference of the THEDES-water content in the formulation of the THEDES particles. Furthermore, the cell viability of the THEDES and the particles with THEDES encapsulated was measured in L929 fibroblasts and the systems prepared were non-cytotoxic.