Supercritical Impregnation Research Articles

Physicochemical characterization, antioxidant and antimicrobial activities of chitosan film containing Sauropus androgynus extract prepared by solution casting and supercritical impregnation

Sauropus androgynus extract (SAE) was incorporated with chitosan to produce solution casting film (SAE-SCF) and supercritical impregnation film (SAE-SIF). The physicochemical characterization and biological activities of SAE-SCF and SAE-SIF films were evaluated and compared. In terms of total phenolic content (TPC) and total flavonoids content (TFC), SAE-SCF (TPC: 49.14–71.88 mg GAE/g; TFC: 32.73–57.05 mg QE/g) obtained higher results than SAE-SIF (TPC: 8.40–18.90 mg GAE/g; TFC: 1.97–12.34 mg QE/g). FTIR results confirmed the interaction between SAE-active compounds and chitosan via hydrogen bonding and electrostatic interaction. Due to the formation of hydrogen bonding or cross-linking effects in SAE-chitosan film, the light opacity (1.748–3.375 AU), water vapor permeability (2.87–3.92 × 10−11 g m−1.s−1.Pa−1), and mechanical properties (tensile strength; 8.65-15.72 MPa; elongation at break: 7.95–13.25%) were enhanced compared to neat chitosan film, with SAE-SCF showing higher performances than SAE-SIF. The antioxidant activities of both films were evaluated using ABTS (IC50: 55.98–97.85 μg/mL) and DPPH assays (IC50: 53.68–143.04 μg/mL), with SAE-SCF showing higher inhibition of free radicals than SAE-SIF. The ferric-reduction power was recorded (28.17–94.95 Trolox μmol/mL), and SAE-SCF achieved a higher reduction power than SAE-SIF. In antimicrobial analysis, SAE-SCF demonstrated the best reduction of viable growth of all tested foodborne microorganisms. Overall, the functional performance of SAE-SCF is better than SAE-SIF in all tested aspects. The results revealed the potential of SAE-SCF to be utilized as a food packaging material.

Using interfacial behavior and adsorption kinetics measurements as a predictor of bulk hydrophobic development of paper supercritically impregnated with food-grade waxes

Supercritical Impregnation methods are becoming popular in the development of food packaging materials. Bulk functional improvements of cellulose substrates using this method may be influenced by interfacial interactions between the impregnated solutes and cellulose. Hence, an interfacial adsorption kinetics study of solute molecules onto the substrate can provide insight on bulk property development, leading to an optimized packaging material with improved functionality. Paper substrates were impregnated with two food-grade waxes: Alkyl Ketene Dimer (AKD) and Carnauba Wax (CW). Hydrophobic development was monitored over a 3-week period. A quartz crystal microbalance (QCM-D) was used to determine interfacial characteristics and behavior of each wax with cellulose, and adsorption kinetics were quantified to compare the mass transfer processes of each wax at the interface. AKD significantly contributed to the substrate’s hydrophobic development over time. CW generated mildly hydrophobic substrates only when heated. AKD strongly adhered to the cellulose fibers at the interface, and demonstrated a 3-stage kinetic adsorption process, tentatively assigned (i) diffusion through the solvent; (ii) diffusion through the substrate; and (iii) attachment onto the fibers. CW readily washed off the cellulose surface, demonstrating only the first adsorption process. The different chemical structures also impacted these behaviors, as did concentration and temperature.Graphical

Production of mono and bilayer devices for wound dressing by coupling of electrospinning and supercritical impregnation techniques

In this paper, electrospinning and supercritical impregnation were coupled to produce polyurethane fibrous membranes loaded with mesoglycan and lactoferrin. The proposed methodology allowed the production of three skin wound healing bilayer systems: a first system containing mesoglycan loaded through electrospinning and lactoferrin loaded by supercritical impregnation, a second system where the use of the two techniques was reversed, and a third sample where the drugs were both encapsulated through a one-step process. SEM analysis demonstrated the formation of microfibers with a homogeneous drug distribution. The highest loadings were 0.062 g/g for mesoglycan and 0.013 g/g for lactoferrin. Then, hydrophilicity and liquid retention analyses were carried out to evaluate the possibility of using the manufacturers as active patches. The kinetic profiles, obtained through in vitro tests conducted using a Franz diffusion cell, proved that the diffusion of the active drugs followed a double-step release before attaining the equilibrium after about 30 h. When the electrospun membranes were placed in contact with HUVEC, HaCaT, and BJ cell lines, as human endothelial cells, keratinocytes, and fibroblasts, respectively, no cytotoxic events were assessed. Finally, the capacity of the most promising system to promote the healing process was performed by carrying out scratch tests on HaCat cells.

Supercritical Impregnation of PETG with Olea europaea Leaf Extract: Influence of Operational Parameters on Expansion Degree, Antioxidant and Mechanical Properties.

PETG (poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)) is an amorphous copolymer, biocompatible, recyclable, and versatile. Nowadays, it is being actively researched for biomedical applications. However, proposals of PETG as a platform for the loading of bioactive compounds from natural extract are scarce, as well as the effect of the supercritical impregnation on this polymer. In this work, the supercritical impregnation of PETG filaments with Olea europaea leaf extract was investigated, evaluating the effect of pressure (100-400 bar), temperature (35-55 °C), and depressurization rate (5-50 bar min-1) on the expansion degree, antioxidant activity, and mechanical properties of the resulting filaments. PETG expansion degree ranged from ~3 to 120%, with antioxidant loading ranging from 2.28 to 17.96 g per 100 g of polymer, corresponding to oxidation inhibition values of 7.65 and 66.55%, respectively. The temperature and the binary interaction between pressure and depressurization rate most affected these properties. The mechanical properties of PETG filaments depended greatly on process variables. Tensile strength values were similar or lower than the untreated filaments. Young's modulus and elongation at break values decreased below ~1000 MPa and ~10%, respectively, after the scCO2 treatment and impregnation. The extent of this decrease depended on the supercritical operational parameters. Therefore, filaments with higher antioxidant activity and different expansion degrees and mechanical properties were obtained by adjusting the supercritical processing conditions.

Morphological 3D Analysis of PLGA/Chitosan Blend Polymer Scaffolds and Their Impregnation with Olive Pruning Residues via Supercritical CO2.

Natural extracts, such as those from the residues of the Olea europaea industry, offer an opportunity for use due to their richness in antioxidant compounds. These compounds can be incorporated into porous polymeric devices with huge potential for tissue engineering such as bone, cardiovascular, osteogenesis, or neural applications using supercritical CO2. For this purpose, polymeric scaffolds of biodegradable poly(lactic-co-glycolic acid) (PLGA) and chitosan, generated in situ by foaming, were employed for the supercritical impregnation of ethanolic olive leaf extract (OLE). The influence of the presence of chitosan on porosity and interconnectivity in the scaffolds, both with and without impregnated extract, was studied. The scaffolds have been characterized by X-ray computed microtomography, scanning electron microscope, measurements of impregnated load, and antioxidant capacity. The expansion factor decreased as the chitosan content rose, which also occurred when OLE was used. Pore diameters varied, reducing from 0.19 mm in pure PLGA to 0.11 mm in the two experiments with the highest chitosan levels. The connectivity was analyzed, showing that in most instances, adding chitosan doubled the average number of connections, increasing it by a factor of 2.5. An experiment was also conducted to investigate the influence of key factors in the impregnation of the extract, such as pressure (10-30 MPa), temperature (308-328 K), and polymer ratio (1:1-9:1 PLGA/chitosan). Increased pressure facilitated increased OLE loading. The scaffolds were evaluated for antioxidant activity and demonstrated substantial oxidation inhibition (up to 82.5% under optimal conditions) and remarkable potential to combat oxidative stress-induced pathologies.

Supercritical Impregnation of Mangifera indica Leaves Extracts into Porous Conductive PLGA-PEDOT Scaffolds.

Plant leaves, such as those from Mangifera indica, represent a potential utilization of waste due to their richness in bioactive compounds. Supercritical CO2 allows these compounds to be incorporated into various matrices by impregnation. Combined with its ability to generate polymeric scaffolds, it represents an attractive strategy for the production of biomedical devices. For this purpose, conjugated polymeric scaffolds of biodegradable PLGA (poly(lactic-co-glycolic acid)) and PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)), generated in situ by foaming, were employed for the supercritical impregnation of ethanolic mango leaves extract (MLE) in tissue engineering as a potential application. The extraction of MLE was performed by Enhanced Solvent Extraction. The effects of pressure (120-300 bar), temperature (35-55 °C), and depressurization rate (1-50 bar/min) on the physical/conductive properties and the impregnation of MLE were studied. The scaffolds have been characterized by liquid displacement, scanning electron microscope, resistance to conductivity techniques, measurements of impregnated load, antioxidant capacity and antimicrobial activity. Porosity values ranging 9-46% and conductivity values between 10-4-10-5 S/cm were obtained. High pressures, low temperatures and rapid depressurization favored the impregnation of bioactive compounds. Scaffolds with remarkable antioxidant activity were obtained (75.2-87.3% oxidation inhibition), demonstrating the ability to inhibit S. aureus bacterial growth (60.1 to 71.4%).

PBAT/PLA Films and Supercritical Impregnation of Caffeine for Potential Application in Anticellulite Tools

AbstractTopical administration is the preferred route for the controlled release of active compounds since it reduces side effects typical of other administration methods. The use of polymer blends is a way to modulate drug release from a topical device. The blends ensure modulation of a wide range of properties, such as mechanical properties, water sorption, and degradation. This paper proposes blends of poly(lactide acid) (PLA), and Poly(butylene adipate‐co‐terephthalate) (PBAT), for the topical release of caffeine, a molecule with anti‐inflammatory, antioxidant, and anticellulite activities. PBAT/PLA blends are optimized for compatibility between the two polymers, mechanical properties, and drug release rate. Blends with a higher amount of PBAT show the best performance regarding polymer compatibility. The blends undergo supercritical CO2‐assisted caffeine impregnation. This process assures homogeneous dispersion of caffeine into the polymer matrix. The ratios 45/55 and 55/45 PBAT/PLA show the best performance in terms of caffeine release (complete caffeine release within 25 h). Caffeine is released into three steps: a burst effect due to the caffeine dispersed over the film surface, a slower release due to the caffeine dispersed in the polymer matrix, and a fast release due to the increase of polymer degradation rate induced by caffeine presence.

Green Sustainable Textile Supercritical Dyeing Process Using CO2 Madder (Rubia tinctorum L.) Extract

ABSTRACT Waterless or reduced water consumption dyeing methods based on supercritical technologies are of interest to fabric manufacturers. The study was aimed at developing a dyeing method for natural fibers, in particular linen and silk, by pressure supercritical impregnation using madder alizarin (R. tinctorum) coloring compound produced by supercritical extraction method as an ecological alternative to conventional dyeing methods. A comparative test of fabric dyeing using supercritical and conventional methods was also carried out. In these dyeing technologies, the pre-treatment process plays an important role in the color intensity. The tests were performed using fabrics without and with mordants, and the results were compared using the color analysis method. The colors of the dyed samples obtained in the supercritical technology are more in shades of carmine, and in the traditional method in duller reds. The proposed modern and ecological dyeing technology guarantees a good resistance to washing and light. Antibacterial activity tests were also performed using supercritical and ethanol extracts. Dyed fabrics play health-promoting and protective roles for their users. Linen fabrics showed antimicrobial activity and positive effects on the skin, which was more moisturized. Waterless technologies should be developed in conjunction with user and environmental impact studies.

Extraction of Bioactive Compounds from Prestonia mollis Leaves and Their Impregnation into Polylactic Acid Using High-Pressure Technologies: Potential for Biomedical Application.

Enhanced solvent extraction (ESE) and pressurized liquid extraction (PLE) have been used for the first time to obtain antioxidant compounds from Prestonia mollis leaves. The effects of pressure (100-250 bar), temperature (55-75 °C) and the composition of the extraction solvent (ethanol, water and hydroalcoholic mixtures) were evaluated according to multilevel factorial designs. PLE provided the largest extraction yields compared to ESE, as well as a greater impact of the operating conditions studied. The highest total phenolic content was obtained when using a hydroalcoholic mixture (CO2/ethanol/water 50/25/25) through ESE at 100 bar and 75 °C. The antioxidant capacity of this extract is related to higher concentration levels of the identified flavonoids: Quercetin 3-O-xylosyl-rutinoside, Kaempferol 3-(2G-apiosylrobinobioside) and Kaempferol 4'-glucoside 7-rhamnoside. This extract was tested for the supercritical impregnation of polylactic acid (PLA), which is a polymer widely used in the biomedical industry. The influence of pressure (100-400 bar), temperature (35-55 °C), amount of extract (3-6 mL) and impregnation time (1-2 h) have been evaluated. The best results were obtained by impregnating 3 mL of extract at 100 bar and 55 °C for 2 h, achieving 10% inhibition with DPPH methods. The extract presented a potentially suitable impregnation of PLA for biomedical applications.

Supercritical impregnation of starch aerogels with quercetin: Fungistatic effect and release modelling with a compartmental model

This work proposes the use of supercritical CO2 to impregnate starch (potato and corn) aerogels with quercetin for a potential fungistatic application. Starch aerogels were successfully produced with supercritical drying, but different results were found depending on the amylose/amylopectin ratio. A higher amount of amylose increases aerogels' specific surface area (with a structure with nanofibrils and nodes) due to the linear and amorphous character of this polymer, whereas a higher amount of amylopectin decreases this property until values of only 25 m2·g−1, obtaining an aerogel with a rough surface. These results were explained with XRD, thermogravimetric, and rheological results (triple step with two temperature sweeps and a time sweep and steady state analysis) concerning hydrogel formation. In fact, retrogradation step plays a more important role in hydrogel formation for a starch source with a higher amount of amylopectin due to an increase in the different polymers' interactions. Supercritical impregnation of quercetin on the aerogels was successfully performed (a loading around 0.30 % with respect to the amount of polymer), and in vitro results indicated that the aerogels produced a fungistatic effect on different types of fungi, but only in the first 12 h because the microorganisms adapted to the surrounding environment. Finally, a compartmental model was used to fit the drug release, which is controlled by quercetin aqueous solubility, indicating the main mass transfer resistances (mass transfer through aerogels was always around 500 min−1 and dissolution process mass transfer from 5·10−3 to 1.65·10−3 s−1) and how an increase in the specific surface area of the aerogels (in the case of corn aerogel) provided a stronger initial burst (70–80 % in 20 min). In fact, this initial burst release was mathematically related to a parameter, that varies from 0.178 to 0.036 depending on the aerogel composition. This study shows that starch aerogels can be impregnated with a hydrophobic compound with fungistatic effect by using supercritical CO2, modifying in addition the drug release by changing the native starch.

PREPARATION OF DRUG-LOADED CHITOSAN/HYDROXYAPATITE COMPOSITE MATERIAL AND ITS NUMERICAL SIMULATION IN NASAL DEFECT REPAIR

With the continuous innovation and development of materials science and tissue engineering technology, biomaterials are gradually being used to replace autologous bone and allogeneic bone grafts in clinical practice for the treatment and repair of bone defects. In this paper, L-arginine-modified chitosan/hydroxyapatite composites were prepared by solution blending of L-arginine-modified chitosan and hydroxyapatite. A hormone drug prednisone acetate was loaded into the composites by supercritical impregnation technique. The results of in vitro release showed that under the loading condition of 12 MPa and 318 K, the cumulative release amount of the drug was 74.6% in 72 h, which had an excellent sustained release effect. In addition, a numerical model of the nasal bone was developed and numerical calculations were performed to analyze and compare the stresses of the healthy nasal bone and the nasal bone repaired with CA/HA composite when subjected to a force of 100 N, in different directions. The total deformation difference at the material was 0.002-0.004 mm/mm, and the stress difference was 0.004–1.373 MPa for the nasal bone in both states, with the sagittal plane under 0–90 degrees of force. The above results indicate that the CA/HA composite has good biological and mechanical properties and can be used to repair nasal bone defects. This material and numerical calculation method can also be applied to other related bone tissue engineering and biomedical materials, which have broad application prospects.

Supercritical Impregnation of Mesoglycan and Lactoferrin on Polyurethane Electrospun Fibers for Wound Healing Applications.

Fibrous membranes of thermoplastic polyurethane (TPU) were fabricated through a uni-axial electrospinning process. Fibers were then separately charged with two pharmacological agents, mesoglycan (MSG) and lactoferrin (LF), by supercritical CO2 impregnation. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis proved the formation of a micrometric structure with a homogeneous distribution of mesoglycan and lactoferrin. Besides, the degree of retention is calculated in four liquid media with different pHs. At the same time, angle contact analysis proved the formation of a hydrophobic membrane loaded with MSG and a hydrophilic LF-loaded one. The impregnation kinetics demonstrated a maximum loaded amount equal to 0.18 ± 0.20% and 0.07 ± 0.05% for MSG and LT, respectively. In vitro tests were performed using a Franz diffusion cell to simulate the contact with the human skin. The release of MSG reaches a plateau after about 28 h while LF release leveled off after 15 h. The in vitro compatibility of electrospun membranes has been evaluated on HaCaT and BJ cell lines, as human keratinocytes and fibroblasts, respectively. The reported data proved the potential application of fabricated membranes for wound healing.

Supercritical impregnation of polyphenols from passion fruit residue in corn starch aerogels: Effect of operational parameters

Supercritical impregnation of polyphenols from passion fruit residue in corn starch aerogels: Effect of operational parameters

Maximising olive oil by‐products

Maximising olive oil by‐products

Dehydration of glycerol over H6P2W18O62/γ-Al2O3 prepared by the supercritical method

H6P2W18O62/γ-Al2O3 prepared by supercritical impregnation exhibited excellent catalytic performance.

Antibacterial Finishing of Cotton Bed Sheets using Olive Leaves Extract

The main goal of this project consisted of the conceptualization and development of a product related to the olive tree chemical features to monetize the wastes of the olive fruit exploitation. The most abundant by-product of the olive fruit harvest is the olive leaves, used as the raw material in this project. By following the steps of Chemical Product Design, it was decided to pursue the idea of creating antibacterial cotton bed sheets impregnated with olive leaves extract, mainly composed of oleuropein. The production process includes a pre-treatment of the olive leaves, oleuropein extraction, and supercritical impregnation. The estimated amount of leaves required is 39 g/m2 of cotton, considering a cotton fabric with 115 GSM.

Exploring the relationship between food-grade wax solubility in supercritical carbon dioxide and resulting hydrophobic development of impregnated paper substrates

Alkyl ketene dimer (AKD) and vegetable wax (VW) are suitable contenders for supercritical impregnation (SCI) processes, where the waxes may be deposited onto paper fiber surfaces to improve their hydrophobicity for food packaging applications. The solubility of both waxes in supercritical carbon dioxide (scCO2) with n-heptane cosolvent was measured (40 – 60 oC and 10 – 18 MPa). VW was two orders of magnitude more soluble in scCO2 compared with AKD, and both sets of data were validated using the Chrastil empirical equation. SCI of AKD wax into paper matrixes was performed at pre-determined solubility conditions, and the resulting hydrophobicity was measured. Results demonstrated that annealing the samples (4 h, 140, 160, 180 oC) immediately following impregnation generally enabled a more rapid development of the CA over a 2-week period. Crucially, using impregnation temperatures and pressures that maximized AKD solubility in scCO2 resulted in CA up to 130o. Gravimetric analysis of the impregnated samples confirmed the expected deposited wax quantities to within 25% of the solubility quantities. Scanning electron microscopy (SEM) imaging revealed better distribution of AKD in annealed samples and partially confirmed that more intricate structures were responsible for higher measured CA. These results explicitly connect the intuitive relationship that higher solute solubility in scCO2 should lead to bulk property improvements (i.e. higher CA or hydrophobicity) after SCI. Continued research in this area will enable the development of metrics, linking solubility conditions to desired bulk material properties, and is expected to lead to innovative packaging of green materials and processes.

Production of Mesoglycan/PCL Based Composites through Supercritical Impregnation.

The development of targeted therapies for wound repair is knowing a growing interest due to the increasing aging of the population and the incidence of chronic pathologies, mainly pressure ulcers. Among molecules recruiting cell populations and promoting the formation of new vital tissue, sodium mesoglycan (MSG) has been proven to be effective in wound healing. In this work, MSG impregnation of polymer matrices has been attempted by a supercritical carbon dioxide-based process. Polymeric matrices are composed of polycaprolactone blends, where water-soluble polymers, polyethylene glycol, polyvinyl pyrrolidone, gelatin, and thermoplastic starch, have been employed to modulate the MSG release, making the devices potentially suitable for topical administrations. Two different techniques have been used to obtain the films: the first one is compression molding, producing compact and continuous structures, and the second one is electrospinning, producing membrane-like designs. A higher amount of MSG can be loaded into the polymeric matrix in the membrane-like structures since, in these films, the impregnation process is faster than in the case of compression molded films, where the carbon dioxide has firstly diffused and then released the active molecule. The type of water-soluble polymer influences the drug release rate: the blend polycaprolactone-gelatin gives a prolonged release potentially suitable for topical administration.

Development a novel robust method to enhance the solubility of Oxaprozin as nonsteroidal anti-inflammatory drug based on machine-learning

Accurate specification of the drugs’ solubility is known as an important activity to appropriately manage the supercritical impregnation process. Over the last decades, the application of supercritical fluids (SCFs), mainly CO2, has found great interest as a promising solution to dominate the limitations of traditional methods including high toxicity, difficulty of control, high expense and low stability. Oxaprozin is an efficient off-patent nonsteroidal anti-inflammatory drug (NSAID), which is being extensively used for the pain management of patients suffering from chronic musculoskeletal disorders such as rheumatoid arthritis. In this paper, the prominent purpose of the authors is to predict and consequently optimize the solubility of Oxaprozin inside the CO2SCF. To do this, the authors employed two basic models and improved them with the Adaboost ensemble method. The base models include Gaussian process regression (GPR) and decision tree (DT). We optimized and evaluated the hyper-parameters of them using standard metrics. Boosted DT has an MAE error rate, an R2-score, and an MAPE of 6.806E-05, 0.980, and 4.511E-01, respectively. Also, boosted GPR has an R2-score of 0.998 and its MAPE error is 3.929E-02, and with MAE it has an error rate of 5.024E-06. So, boosted GPR was chosen as the best model, and the best values were: (T = 3.38E + 02, P = 4.0E + 02, Solubility = 0.001241).

Supercritical Impregnation of Mango Leaf Extract into PLA 3D-Printed Devices and Evaluation of Their Biocompatibility with Endothelial Cell Cultures.

The addition of natural substances with pharmacoactive properties to polymeric biomedical devices would provide beneficial regarding the assimilation of these endoprostheses when implanted into a patient’s body. The added drug would facilitate endothelization by regulating the inflammatory processes that such interventions entail, preventing contamination hazards and favoring the angiogenesis or formation of blood vessels in the tissue. The present work used mango leaf extract (MLE) obtained through pressurized ethanol for this purpose. Polylactic acid (PLA) in the form of filaments or 3D-printed disks was impregnated by means of supercritical technology with MLE for the culture essays. The release kinetics has been studied and the polymer matrices have been examined by scanning electron microscopy (SEM). The impregnated devices were subjected to in vitro culture of colony-forming endothelial cells. The influence of the different impregnation conditions used for the production of the MLE impregnated polymeric devices on the development of the cell culture was determined by fluorescence microscopy. The best results were obtained from the calcein cultures on 35 °C MLE impregnated into 3D-printed polymer disks.