Encapsulation of Olive (Olea europaea L.) Pruning Waste Particles by Supercritical CO2 Technology.

Olive leaves (Olea europaea L.) contain a multitude of bioactive compounds such as sterols, carotenes, triterpenic alcohols and phenolic compounds. These compounds have been shown to exhibit antiviral, antioxidant, candida-growth-inhibitory, anticancer, antifungal, anti-inflammatory and antibacterial activities. In this sense, submicron particles from olive leaves with antioxidant activity were precipitated by supercritical antisolvent extraction in a previous work. Moreover, encapsulation enables the delayed release of compounds and avoids the first-step effect in medical therapies. Therefore, this work focused on encapsulation of particles with a certain antioxidant capacity from olive pruning waste using supercritical technology. A variety of experiments were carried out to test how the different operating variables (pressure, temperature and extract-polymer ratio) affect. Morphology was analyzed by SEM microscopy, obtaining encapsulates between 1 and 5 microns in size. The antioxidant capacity was determined by the DPPH assay, with most of the encapsulates having AAI values between 0.5 and 1 (moderate antioxidant capacity). An increase in polyphenol content was observed in the 1:3 ratio tests. The release of the compounds in gastric simulated medium was retarded by the polymeric encapsulation, while in intestinal fluid, the solubility was improved compared to the unencapsulated particles. Overall, the supercritical encapsulation process for the natural extract of olive pruning residues has proven to be effective in obtaining antioxidant particles with different release profiles.

Formation of PLGA-PEDOT: PSS Conductive Scaffolds by Supercritical Foaming.

The usage of conjugated materials for the fabrication of foams intended to be used as therapeutic scaffolds is gaining relevance these days, as they hold certain properties that are not exhibited by other polymer types that have been regularly used until the present. Hence, this work aims to design a specific supercritical CO2 foaming process that would allow the production of porous polymeric devices with improved conductive properties, which would better simulate matrix extracellular conditions when used as therapeutic scaffolds (PLGA-PEDOT:PSS) systems. The effects of pressure, temperature, and contact time on the expansion factor, porosity, mechanical properties, and conductivity of the foam have been evaluated. The foams have been characterized by scanning electron and atomic force microscopies, liquid displacement, PBS degradation test, compression, and resistance to conductivity techniques. Values close to 40% porosity were obtained, with a uniform distribution of polymers on the surface and in the interior, expansion factors of up to 10 orders, and a wide range of conductivity values (2.2 × 10-7 to 1.0 × 10-5 S/cm) and mechanical properties (0.8 to 13.6 MPa Young's modulus in compression test). The conductive and porous scaffolds that have been produced by supercritical CO2 in this study show an interesting potential for tissue engineering and for neural or cardiac tissue regeneration purposes due to the fact that electrical conductivity is a crucial factor for proper cell function and tissue development.

Generation of Highly Antioxidant Submicron Particles from Myrtus communis Leaf Extract by Supercritical Antisolvent Extraction Process.

Submicron particles have been produced from an ethanolic extract of Myrtus communnis leaves using supercritical carbon dioxide technology, hereinafter referred to as Supercritical Antisolvent Extraction (SAE). The influence of pressure (9-20 MPa), temperature (308 and 328 K) and injection rate (3 and 8 mL/min) on the particles' precipitation has been investigated, and it has been confirmed that increases in pressure and temperature led to smaller particle sizes. The obtained particles had a quasi-spherical shape with sizes ranging from 0.42 to 1.32 µm. Moreover, the bioactivity of the generated particles was assessed and large contents of phenolic compounds with a high antioxidant activity were measured. The particles were also subjected to in vitro studies against oxidative stress. The myrtle particles demonstrated cytoprotective properties when applied at low concentrations (1 µM) to macrophage cell lines.

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%).

Inclusion of Natural Antioxidants of Mango Leaves in Porous Ceramic Matrices by Supercritical CO2 Impregnation.

Mango is one of the most important, medicinal tropical plants in the world from an economic point of view due to the presence of effective bioactive substances as co-products in its leaves. The aim of this work was to enhance the impregnation of natural antioxidants from mango leaves into a porous ceramic matrix. The effects of pressure, temperature, impregnation time, concentration of the extract and different porous silica on impregnation of phenolic compounds and antioxidant activity were analyzed. The volume of the pressurized fluid extract and amount of porous ceramic matrix remained constant. The best impregnation conditions were obtained at 6 h, 300 bar, 60 mg/mL, 35 °C and with MSU-H porous silica. The results indicated that increasing the pressure, concentration of the extract and temperature during impregnation with phenolic compounds such as gallic acid and iriflophenone 3-C (2-O-p-hydroxybenzolyl)-ß-D-glucoside increased the antioxidant activity and the amount of total phenols.

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.

Structural Modification of Polymers Functionalized with Mango Leaf Extract by Supercritical Impregnation: Approaching of Further Food and Biomedical Applications.

Identifying new polymers from natural resources that can be effectively functionalized can have a substantial impact on biomedical devices and food preservation fields. Some of these polymers would be made of biodegradable, renewable and compostable materials, and present the kind of porosity required to effectively carry active compounds that confer on them the desired properties for their intended applications. Some natural extracts, such as mango leaf extract, have been proven to have high levels of antioxidant, antimicrobial or anti-inflammatory properties, making them good candidates for controlled-release applications. This work intends to investigate the supercritical impregnation of different types of polymers (ABS, PETG, TPU, PC and PCL) with mango leaf extract. The influence of temperature and pressure on the polymers' structure (swelling and foaming processes) and their different behaviors have been analyzed. Thus, TPU and PC experience minimal structural modifications, while PETG, PCL and ABS, on the other hand, suffer quite significant structural changes. TPU and PETG were selected as the representative polymers for each one of these behaviors to delve into mango leaf extract impregnation processes. The bioactive capacity of the extract is present in either impregnated polymer, with 25.7% antioxidant activity by TPU processed at 35 °C and 100 bar and 32.9% antioxidant activity by PETG impregnated at 75 °C and 400 bar.

Development of Porous Polyvinyl Acetate/Polypyrrole/Gallic Acid Scaffolds Using Supercritical CO2 as Tissue Regenerative Agents.

Scaffolds are advanced devices employed in tissue engineering, as they are intended to mimic the characteristics of extracellular matrices. In this respect, conjugated materials are gaining relevance in the manufacturing of the foams used for therapeutic scaffolds, since they can provide certain properties that are missing in the other polymers used to form the scaffolds. This work has, therefore, focused on the development of functional scaffolds formed by conjugated-non-conjugated polymers such as polyvinyl acetate and polypyrrole, impregnated with gallic acid as the model drug and produced by means of a supercritical CO2 foaming/impregnation process. The effects from a series of parameters such as pressure, temperature, depressurization rate, and contact time of the scaffold production process have been determined. The impregnated foams have been characterized according to their morphology, including their porosity and expansion factor, their drug loading and delivering capabilities, and their mechanical and electrical properties. The characterization of the experiments was carried out using scanning electron microscopy, liquid displacement, in vitro release, electrochemical impedance spectroscopy, and compression techniques. The results from our tests have revealed a considerable influence of all the input variables studied, as well as relevant interactions between them. Values close to 35% porosity were obtained, with a drug release of up to 10 h with a fast initial release. The best operating conditions were 353 K, 30 MPa, 0.5 MPa/min depressurization rate, and 1 h contact time. By means of the supercritical foaming/impregnation technique, scaffolds with potential in tissue engineering due to their studied properties were obtained.

An Attempt to Optimize Supercritical CO2 Polyaniline-Polycaprolactone Foaming Processes to Produce Tissue Engineering Scaffolds.

Conjugated polymers are biomaterials with high conductivity characteristics because of their molecular composition. However, they are too rigid and brittle for medical applications and therefore need to be combined with non-conductive polymers to overcome or lessen these drawbacks. This work has, consequently, focused on the development of three-dimensional scaffolds where conductive and non-conductive polymers have been produced by combining polycaprolactone (PCL) and polyaniline (PANI) by means of supercritical CO2 foaming techniques. To evaluate their therapeutic potential as implants, a series of experiments have been designed to determine the most influential variables in the production of the three-dimensional scaffolds, including temperature, pressure, polymer ratio and depressurization rate. Internal morphology, porosity, expansion factor, PANI loads, biodegradability, mechanical and electrical properties have been taken as the response variables. The results revealed a strong influence from all the input variables studied, as well as from their interactions. The best operating conditions tested were 70 °C, 100 bar, a ratio of 5:1 (PCL:PANI), a depressurization rate of 20 bar/min and a contact time of 1 h.

Potential Use of Annona Genus Plants Leaf Extracts to Produce Bioactive Transdermal Patches by Supercritical Solvent Impregnation.

The objective of the present work was to develop a bioactive transdermal patch functionalized with Annona leaf extracts (ALE) by means of supercritical impregnation technique. The potential of six different Annona leaf extracts (ALE) obtained with the enhanced solvent system formed by carbon dioxide + ethanol/acetone was evaluated taking into account the antioxidant activity, total phenol composition and global extraction yields. For the impregnation of ALE, two drug supporting systems were tested: hydrocolloid sodium carboxymethyl cellulose (NaCMC) and polyester dressings (PD). The effect of the impregnation conditions, including pressure (P), temperature (T), percent of co-solvent (ethanol) and ALE/polymer mass ratio, was determined with regard to the loading and the functional activity of the impregnated samples. The optimal impregnation conditions of ALE were established at 55 °C and 300 bar which led to obtained transdermal patches with antioxidant and antimicrobial capacity. In order to understand the behavior of the process, the homogeneity of the samples in the vessels was also evaluated. The best results were obtained at higher proportions of co-solvent in the system.

Determining the Optimal Conditions for the Production by Supercritical CO2 of Biodegradable PLGA Foams for the Controlled Release of Rutin as a Medical Treatment.

Poly(D,L,-lactide-co-glycolide) (PLGA) foam samples impregnated with rutin were successfully produced by supercritical foaming processes. A number of parameters such as pressure (80-200 bar), temperature (35-55 °C), depressurization rate (5-100 bar/min), ratio lactide:glycolide of the poly(D,L,-lactide-co-glycolide) (50:50 and 75:25) were studied to determine their effect on the expansion factor and on the glass transition temperature of the polymer foams and their consequences on the release profile of the rutin entrapped in them. The impregnated foams were characterized by scanning electron microscopy, differential scanning calorimetry, and mercury intrusion porosimetry. A greater impregnation of rutin into the polymer foam pores was observed as pressure was increased. The release of rutin in a phosphate buffer solution was investigated. The controlled release tests confirmed that the modification of certain variables would result in considerable differences in the drug release profiles. Thus, five-day drug release periods were achieved under high pressure and temperature while the depressurization rate remained low.

Application of a Natural Antioxidant from Grape Pomace Extract in the Development of Bioactive Jute Fibers for Food Packaging.

There is an increasing demand for the use of new food packaging materials. In this study, natural jute fibers impregnated with a Petit Verdot Red Grape Pomace Extract (RGPE) was proposed as a new active food packaging material. Pressurized Liquid Extraction (PLE) and Enhanced Solvent Extraction (ESE) techniques were employed to obtain the bioactive RGPE. Afterward the supercritical solvent impregnation conditions to obtain RGPE-natural jute fibers were studied, by varying pressure, modifier percentage and dried RGPE mass. PLE technique offered the highest bioactive extract at 20 MPa, 55 °C, 1 h residence time using C2H5OH:H2O (1:1 v/v), providing an EC50 of 3.35 ± 0.25 and antibacterial capacity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa (MIC of 12.0, 1.5 and 4.0 mg/mL RGPE respectively). The natural jute fibers impregnated with 3 mL of that RGPE (90 mg/mL) at 50 MPa and 55 °C generated the most efficient packing material with regards to its food preservation potential.

Usage of supercritical fluid techniques to obtain bioactive alkaloid-rich extracts from cherimoya peel and leaves: extract profiles and their correlation with antioxidant properties and acetylcholinesterase and α-glucosidase inhibitory activities.

The agroindustrial sector is highly concerned with regards to reducing the environmental impact of waste from pruning activities (leaves, branches and bark) and from food industry processes (peels and seeds). In this sense, the wastes generated by cherimoya cultivation and processing industries should be contemplated as a valuable source of biologically active compounds. In this work, we have studied the bioactivity of alkaloid-rich Annona cherimola Mill. extracts obtain by means of supercritical fluid extraction techniques. The extracts were obtained from the peel and leaves using the following optimal conditions: 100 bar of pressure, 75 °C and 15% methanol as co-solvent. High antioxidant capacity (5304.23 ± 73.60 to 21 705.20 ± 1069.31 µmol Trolox equivalent per 100 g), and acetylcholinesterase (IC50 = 87.69 ± 3.42 to 515.02 ± 29.25 µg mL-1) and α-glucosidase (IC50 = 1097.76 ± 121.12 to 3206.88 ± 97.06 µg mL-1) inhibitory activities were exhibited by both peel and leaf extracts. Larger alkaloid contents were determined by UHPLC-ESI-MS analysis, with peel extracts presenting a high concentration of N-trans-feruloyl phenethylamine, while leaf extracts were rich in anonine. This work reports novel data on bioactivity of cherimoya peel and leaves and their potential as a source of bioactive compounds.

Foaming of Polycaprolactone and Its Impregnation with Quercetin Using Supercritical CO2.

Foamed polycaprolactone impregnated with quercetin was carried out with a batch foaming technique using supercritical CO2. The experimental design was developed to study the influence of pressure (15-30 MPa), temperature (308-333 K), and depressurization rate (0.1-20) on the foam structure, melting temperature, and release tests of composites. The characterization of the experiments was carried out using scanning electron microscopy, X-ray diffractometer, and differential scanning calorimetry techniques. It was observed that the porosity created in the polymer had a heterogeneous structure, as well as the impregnation of the quercetin during the process. On the other hand, controlled release tests showed a significant delay in the release of quercetin compared to commercial quercetin.