Functional Modification of Cellulose Acetate Microfiltration Membranes by Supercritical Solvent Impregnation

This study investigates the modification of commercial cellulose acetate microfiltration membranes by supercritical solvent impregnation with thymol to provide them with antibacterial properties. The impregnation process was conducted in a batch mode, and the effect of pressure and processing time on thymol loading was followed. The impact of the modification on the membrane's microstructure was analyzed using scanning electron and ion-beam microscopy, and membranes' functionality was tested in a cross-flow filtration system. The antibiofilm properties of the obtained materials were studied against Staphyloccocus aureus and Pseudomonas aeruginosa, while membranes' blocking in contact with bacteria was examined for S. aureus and Escherichia coli. The results revealed a fast impregnation process with high thymol loadings achievable after just 0.5 h at 15 MPa and 20 MPa. The presence of 20% of thymol provided strong antibiofilm properties against the tested strains without affecting the membrane's functionality. The study showed that these strong antibacterial properties could be implemented to the commercial membranes' defined polymeric structure in a short and environmentally friendly process

Functionalization of polyamide microfiltration membranes by supercritical solvent impregnation

The study reports the application of supercritical solvent impregnation to deliver antibacterial substance thymol to the defined polymeric structure of commercial polyamide microfiltration membranes. The process performed at a temperature of 40 degrees C and pressures of 10, 15, and 20 MPa was characterized by the fast impregnation in the first 30 min with thymol loadings up to 29 wt%. The maximal achieved thymol loading in the process was around 42 wt%, regardless the pressure. The scanning electron and ion microscopy analyses revealed that the membranes' microstructure was preserved with a thymol content of 20 wt%, while a more prominent swelling effect was observed in samples with 35 wt% of thymol. The cross-flow filtration tests showed that the impregnation process did not harm the membranes' functionality in samples with 20 wt% of thymol. These membranes exhibited strong anti-biofilm activity, and were less prone to the blockage with bacteria in comparison to neat membranes

Impregnation of cotton fabric with pyrethrum extract in supercritical carbon dioxide

This study discusses a possibility of cotton fabric impregnation with pyrethrum extract as a tick repellent in supercritical carbon dioxide. A solubility of pyrethrum extract in supercritical carbon dioxide has been determined at 35 and 40 degrees C and pressures ranging from 8 to 20 MPa. The highest solubility of 48.69 kg/m(3) was obtained at temperature of 35 degrees C and pressure of 20 MPa. Density -based equations of Chrastil, Adachi-Lu and del Valle-Aguilera were employed to correlate the experimental data. Based on the solubility data, conditions for the impregnation of cotton fabric were selected. Conditions at 40 degrees C and 8 MPa provided targeted quantities of the impregnated extract of 0.5% and 1% after 1 h and 2 h of the impregnation, respectively. The presence of pyrethrins on the cotton fabric's surface was confirmed by FTIR analysis. Repellent activity of both impregnated cotton fabrics (pyrethrum extract contents of 0.5% and 1%) was proven against ticks

SFE as a superior technique for isolation of extracts with strong antibacterial activities from lichen Usnea barbata L.

The number of cases of fatal infections in humans and animals caused by multiresistant and panresistant bacterial strains has been dramatically increased over the past 10 years on almost every continent. Therefore, implementation of newer technologies in order to develop processes for isolation of substances with strong antibacterial activities from natural sources is of increasing interest. In this study, advantage of high pressure processing and supercritical fluid extraction with carbon dioxide in isolation of active principles from lichen Usnea barbata L was presented. Supercritical extraction showed extremely higher selectivity toward usnic acid compared to the conventional techniques tested. In order to simulate the process and estimate mass transfer coefficients, the new mathematical model of Sovova (2011) was applied. Supercritical extract obtained at 40 C and 30 MPa showed stronger antibacterial activity against the most of tested strains compared to pure usnic acid and extracts obtained using ethanol as a solvent. Further, supercritical extract with lower usnic acid content expressed stronger antibacterial activity against the majority of tested strains including MRSA strains compared to the pure usnic acid and the supercritical extract with the higher usnic acid content. The same extract was far more effective than ampicillin against Streptococcus uberis, all tested Enterococcus faecalis, MRSA and MRSA ATCC 33591. Against few tested strains, the supercritical extract was superior to erythromycin and penicillin as well. These findings justified possible benefits of inclusion of supercritical extracts into pharmaceutical and cosmetic formulations. Applied mathematical model described the SFE process with high accuracy

A novel chitosan gels: Supercritical CO2 drying and impregnation with thymol

Supercritical carbon dioxide (scCO(2)) technology was used for preparation of functional pH sensitive chitosan-based aerogels characterized with micron size pores and their impregnation with thymol as a natural bioactive substance. Hydrogels based on chitosan, itaconic and methacrylic acids were transformed to alcogels and dried in the air or with scCO(2) to obtain xero- and aerogels, respectively. Applying 10 min of static and 120 min of dynamic scCO(2) drying at 11 MPa and 45 degrees C followed with the decompression at a rate of 1 MPa/min yielded an advantageous aerogel with favorable swelling kinetics and elasticity, compared to the xerogel and aerogels obtained at other decompression rates and drying times. This aerogel was successfully loaded with thymol (up to 4.6 wt.%) using supercritical scCO(2) at 10 MPa and 35 degrees C. In vitro studies of swelling in PBS at 37 degrees C indicated a great potential of the obtained stimuli-responsive chitosan gels for topical administration of thymol known for antimicrobial, antioxidant and anti-inflammatory activities. POLYM. ENG. SCI., 58:2192-2199, 2018. (c) 2018 Society of Plastics Engineer