Supercritical foaming and impregnation of polycaprolactone and polycaprolactone-hydroxyapatite composites with carvacrol

Producción CientíficaPolycaprolactone (PCL) and polycaprolactone-hydroxyapatite (PCL-HA) scaffolds were produced by foaming in supercritical carbon dioxide (scCO2) at 20 MPa, as well as in one-step foaming and impregnation process using carvacrol as an antibacterial agent with proven activity against Gram-positive and Gram-negative bacteria. The experimental design was developed to study the influence of temperature (40 °C and 50 °C), HA content (10 and 20 wt.%), and depressurization rate (one and two-step decompression) on the foams’ morphology, porosity, pore size distribution, and carvacrol impregnation yield. The characterization of the foams was carried out using scanning electron microscopy (SEM, SEM-FIB), Gay-Lussac density bottle measurements, and Fourier–transform infrared (FTIR) analyses. The obtained results demonstrate that processing PCL and PCL-HA scaffolds by means of scCO2 foaming enables preparing foams with porosity in the range of 65.55–74.39% and 61.98–67.13%, at 40 °C and 50 °C, respectively. The presence of carvacrol led to a lower porosity. At 40 °C and one-step decompression at a slow rate, the porosity of impregnated scaffolds was higher than at 50 °C and two- step fast decompression. However, a narrower pore size distribution was obtained at the last processing conditions. PCL scaffolds with HA resulted in higher carvacrol impregnation yields than neat PCL foams. The highest carvacrol loading (10.57%) was observed in the scaffold with 10 wt.% HA obtained at 50 °C.Narodowe Centrum Nauki (Polonia) - (grant 2018/31/B/ ST8/01826)Agencia Nacional de Investigación y Desarrollo de Chile (ANID) - (project 120130)Programa de Financiamiento Basal para Centros Científicos y Tecnológicos de Excelencia - (Project AFB180001

Supercritical Fluid Applications in the Design of Novel Antimicrobial Materials

Bacterial resistance to antibiotics is one of the biggest problems in the modern world. The prevention of bacterial spreading from hospitals to the community and vice versa is an issue we have to deal with. This review presents a vast potential of contemporary high-pressure techniques in the design of materials with antimicrobial activity. Scientists from all over the world came up with ideas on how to exploit extraordinary properties of supercritical fluids in the production of advantageous materials in an environmentally friendly way. The review summarizes reported methods and results

Utilization of supercritical CO2 in bioactive principles isolation from Helichrysum italicum and their adsorption on selected fabrics

Helichrysum italicum (Roth) G. Don fil., Asteraceae, possesses numerous secondary plant metabolites with a wide range of biological activities. Yet, data on the potential of supercritical fluid extraction (SFE) in their isolation are scarce. This study provides analyses of the chemical profiles of extracts obtained by SFE with or without ethanol as a cosolvent using GC-FID, GC-MS, HPLC, and UHPLC-MS techniques. Among the compounds with proven biological activity identified, the presence of arzanol was confirmed. In the next step, the integrated process of supercritical fluid extraction and impregnation was applied to deliver active compounds to cotton gauze and polypropylene fabric for possible topical applications. The analytical procedures results showed a considerable affinity of both textile materials for incorporating active components present in the H. italicum. The study indicated the high-pressure techniques applied as very efficient in the isolation of bioactive components from H. italicum and their adsorption on selected carriers

Comparative analyses of diffusion coefficients for different extraction processes from thyme

This work was aimed to analyze kinetics and mass transfer phenomena for different extraction processes from thyme (Thymus vulgaris L.) leaves. Different extraction processes with ethanol were studied: Soxhlet extraction and ultrasound-assisted batch extraction on the laboratory scale as well as pilot plant batch extraction with mixing. The extraction processes with ethanol were compared to the process of supercritical carbon dioxide extraction performed at 10 MPa and 40°C. Experimental data were analyzed by mathematical model derived from the Fick’s second law to determine and compare diffusion coefficients in the periods of constant and decreasing extraction rate. In the fast extraction period, values of diffusion coefficients were one to three orders of magnitude higher compared to those determined for the period of slow extraction. The highest diffusion coefficient was reported for the fast extraction period of supercritical fluid extraction. In the case of extraction processes with ethanol, ultrasound, stirring and extraction temperature increase enhanced mass transfer rate in the washing phase. On the other hand, ultrasound contributed the most to the increase of mass transfer rate in the period of slow extraction

Supercritical Foaming and Impregnation of Polycaprolactone and Polycaprolactone-Hydroxyapatite Composites with Carvacrol

Polycaprolactone (PCL) and polycaprolactone-hydroxyapatite (PCL-HA) scaffolds were produced by foaming in supercritical carbon dioxide (scCO2) at 20 MPa, as well as in one-step foaming and impregnation process using carvacrol as an antibacterial agent with proven activity against Gram-positive and Gram-negative bacteria. The experimental design was developed to study the influence of temperature (40 °C and 50 °C), HA content (10 and 20 wt.%), and depressurization rate (one and two-step decompression) on the foams’ morphology, porosity, pore size distribution, and carvacrol impregnation yield. The characterization of the foams was carried out using scanning electron microscopy (SEM, SEM-FIB), Gay-Lussac density bottle measurements, and Fourier–transform infrared (FTIR) analyses. The obtained results demonstrate that processing PCL and PCL-HA scaffolds by means of scCO2 foaming enables preparing foams with porosity in the range of 65.55–74.39% and 61.98–67.13%, at 40 °C and 50 °C, respectively. The presence of carvacrol led to a lower porosity. At 40 °C and one-step decompression at a slow rate, the porosity of impregnated scaffolds was higher than at 50 °C and two- step fast decompression. However, a narrower pore size distribution was obtained at the last processing conditions. PCL scaffolds with HA resulted in higher carvacrol impregnation yields than neat PCL foams. The highest carvacrol loading (10.57%) was observed in the scaffold with 10 wt.% HA obtained at 50 °C

Cellulose Acetate Membranes Modification by Aminosilane Grafting in Supercritical Carbon Dioxide towards Antibiofilm Properties

The study explores the grafting of cellulose acetate microfiltration membranes with an aminosilane to attain antibiofilm properties. The grafting reaction was performed in the supercritical carbon dioxide used as a transport and reaction medium. The FTIR analyses and dissolution tests confirmed the covalent bonding between the aminosilane and polymer. The membranes’ microstructure was investigated using a dual-beam SEM and ion microscopy, and no adverse effects of the processing were found. The modified membranes showed a more hydrophilic nature and larger water permeate flow rate than the neat cellulose acetate membranes. The tests in a cross-filtration unit showed that modified membranes were considerably less blocked after a week of exposure to Staphylococcus aureus and Escherichia coli than the original ones. Microbiological investigations revealed strong antibiofilm properties of the grafted membranes in experiments with Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella Enteritidis

Extraction of lyophilized olive mill wastewater using supercritical CO2 processes

The olive growing in Tunisia has an economic dominance and agricultural importance. However, the huge extraction of olive oil generates a large quantity of olive mill wastewater (OMW), which is discharged to the surroundings. The highly polluting potential (organic load) of OMW threatens the environment and requires an urgent solution. Supercritical fluid extraction (SFE) is a green extraction method that can be applied to purify OMW and, at the same time, to isolate a high quality oil from this wastewater. In order to explore and to valorize the compositions of Olive mill wastewater (OMW), extraction in different solvents (supercritical CO2, hexane) was carried out and chemical composition of the extracted oils were established by GC-FID. The Tunisia OMW were collected from two different zones namely Sousse and Sfax. In this work, we have investigated the effects pressure (P) and temperature (T) on the yield and the quality of oil. The suitable conditions for the extraction of oil from lyophilized OMW by Super-critical carbon dioxide (SC-CO2) were found to be the pressure of 30 MPa and the temperature of 60 degrees C. In order to simulate the process, the model of broken and intact cells (Sovova's model) was applied. The model well represented the experimental data

Application of cellulose acetate for controlled release of thymol

Cellulose acetate (CA) was investigated as a carrier towards development of material with controlled release of thymol as a natural substance with strong antibacterial properties using high pressure techniques. Effect of thymol content on CA was confirmed by SEM, FTIR and DSC methods. Kinetic of thymol release from CA was tested using simulated gastric and intestinal fluids (hydrochloric acid and phosphate buffer saline). Results were correlated with Korsmeyer-Peppas and Weibull model. Depending on the thymol content and chemical nature of the release medium, the time of thymol release varied from one to three days indicating CA as a promising carrier of thymol with potential uses from medicine to agriculture. The impregnated CA showed antibacterial activity against 23 tested bacterial strains including methicillin-resistant Staphylococcus aureus (MRSA) which is particularly important bearing in mind that this strain causes fatal infections in humans and animals

Antioxidant properties of the anthocyanin-containing ultrasonic extract from blackberry cultivar "Cacanska Bestrna"

For the first time, an ultrasound-assisted extraction was used to investigate isolation of anthocyanin-containing extracts from the blackberry cultivar "Cacanska Bestrna" widely grown in Serbia. Sonication time and temperature influence on the yield, active substances content and antioxidant activity of the extracts isolated from blackberry fruit pur e was discussed. Ultrasound-assisted extraction with acidified ethanol at room and moderately high temperature (40 degrees C) enabled rapid isolation (15-30 min) of anthocyanin-containing blackberry extracts with the high yields (5.3-6.3%). Both increase of the sonication temperature and time within studied ranges had positive effect on the extraction yield. The HPLC analysis revealed the presence of the anthocyanins in the investigated samples. After hydrolysis of all the samples, aglycone-cyanidin was detected in the samples. Determined cyanidin content in the obtained blackberry extracts (0.7-1.0%) was up to 20 times higher than in the blackberry juice. Cyanidin content was positively affected by sonication time and temperature increase. The antioxidant properties of the extracts were analyzed by the ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picryihydrazyl (DPPH) radical scavenging capacity assays. Positive effect of increase of the sonication time and/or temperature on the scavenging activity of the extracts against free DPPH radicals and thus lower IC50 values was demonstrated. Strong linear correlation of DPPH radical scavenging capacities of the extracts with content of cyanidin and tannins was established. FRAP values significantly correlated with total tannin content in the extracts. The analyses of composition and antioxidant properties in this study revealed great potential of blackberry ultrasonic extracts of the cultivar "Cacanska Bestrna" for further use in food and pharmaceutical industries