Solvent Impregnation Research Articles

Polymeric Microfiltration Membranes Modification by Supercritical Solvent Impregnation-Potential Application in Open Surgical Wound Ventilation.

This study investigated supercritical solvent impregnation of polyamide microfiltration membranes with carvacrol and the potential application of the modified membranes in ventilation of open surgical wounds. The impregnation process was conducted in batch mode at a temperature of 40 °C under pressures of 10, 15, and 20 MPa for contact times from 1 to 6 h. FTIR was applied to confirm the presence of carvacrol on the membrane surface. In the next step, the impact of the modification on the membrane structure was studied using scanning electron and ion beam microscopy and cross-filtration tests. Further, the release of carvacrol in carbon dioxide was determined, and finally, an open thoracic cavity model was applied to evaluate the efficiency of carvacrol-loaded membranes in contamination prevention. Carvacrol loadings of up to 43 wt.% were obtained under the selected operating conditions. The swelling effect was detectable. However, its impact on membrane functionality was minor. An average of 18.3 µg of carvacrol was released from membranes per liter of carbon dioxide for the flow of interest. Membranes with 30–34 wt.% carvacrol were efficient in the open thoracic cavity model applied, reducing the contamination levels by 27% compared to insufflation with standard membranes.

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.

Immobilization of Silver Nanoparticles on Chitosan-Coated Silica-Gel-Beads and the Antibacterial Activity

Silver nanoparticles (Ag0) have attracted the most attention due to their broad antimicrobial application and outstanding activity. The silver nanoparticles are usually in colloidal form, then immobilization the colloid onto solid support is still interesting to explore. In this work, a new method for silver colloidal nanoparticle immobilization on silica gel beads (SiG), which was then symbolized as Ag0-[chi-SiG] was conducted and characterized successfully. The finding proved that SiG must be coated with three chitosan film layers to give stable support for silver nanoparticles. This coating method caused the chitosan completely covered SiG, and the chitosan film provides coordination bonding for silver ions. The most appropriate solvent for silver ion impregnation on the surface of chi-SiG is methanol compared to other solvents. Tungsten lamp as the photo-irradiation, which is low cost and environmentally friendly has been proven effective for silver ion reduction, as shown by silver metal colloid UV-Vis surface plasmon resonance at 400-700 nm. Ag0-[chi-SiG] showed the antibacterial properties of inhibiting the growth Staphylococcus aureus and Escherichia coli; then it provides the potential application for antibacterial filter material. According to the weight comparison between antibacterial standard and Ag content, then Ag0-[chi-SiG] has two and five times higher of exhibiting zone for each bacteria.

Supercritical Impregnation of Ketoprofen into Polylactic Acid for Biomedical Application: Analysis and Modeling of the Release Kinetic.

Ketoprofen (KET) is an anti-inflammatory drug often used in medicine due to its analgesic and antipyretic effects. If it is administered in a controlled form by means of different dosing devices, it acts throughout the patient’s recovery period improving its efficacy. This study intends to support the use of supercritical solvent impregnation (SSI) as an efficient technique to develop polylactic acid (PLA) functionalized with ketoprofen, for use as controlled drug release devices. For this purpose, firstly, the influence of different SSI variables on the desirable swelling of the polymer structure, while avoiding their foaming, were evaluated. Then, the resulting ketoprofen loading was evaluated under different pressure/temperature conditions. It was generally found that as pressure and temperature are higher, the drug impregnation loads also increase. The maximum impregnation loads (at about 9% KET/PLA) were obtained at 200 bar and 75 °C. In vitro drug release tests of the impregnated compound were also carried out, and it was found that drug release profiles were also dependent on the specific pressure and temperature conditions used for the impregnation of each polymer filament.

Antibacterial activity of thymol/carvacrol and clinoptilolite composites prepared by supercritical solvent impregnation

Antibacterial activity of thymol/carvacrol and clinoptilolite composites prepared by supercritical solvent impregnation

In Vitro Study of the Release of Drugs Impregnated by Supercritical Technology in Polylactic Acid for Biomedical Applications

The manufacture of functionalized bioabsorbable polymeric implants is gaining attention in recent years. These devices administer gradually and locally drugs or biomolecules to treat several diseases and they disappear once they perform their function. In this work, ketoprofen, an anti-inflammatory drug with analgesic and antipyretic effects, was loaded by supercritical solvent impregnation (SSI) in polylactic acid (PLA) filaments, and the initial stage of its in vitro release was explored. Impregnation experiments were carried out in a range of pressure and temperature of 25-40 MPa and 328-348 K. Different drug loading values were obtained (up to 9 % respecting the polymer mass) depending on the operating conditions.The ketoprofen release profile and the mathematical modelling (Korsmeyer-Peppas and Peppas-Sahlin models) showed an initial release governed by diffusion and with different kinetics depending on the impregnation conditions. Thus, this study reveals that SSI could be used to manufacture personalized drug-delivery implants based on the final dose and required dosing rate.

Supercritical Carbon Dioxide as a Green Alternative to Achieve Drug Complexation with Cyclodextrins.

Cyclodextrins are widely used in pharmaceutics to enhance the bioavailability of many drugs. Conventional drug/cyclodextrin complexation techniques suffer from many drawbacks, such as a high residual content of toxic solvents in the formulations, the degradation of heat labile drugs and the difficulty in controlling the size and morphology of the product particles. These can be overcome by supercritical fluid technology thanks to the outstanding properties of supercritical CO2 (scCO2) such as its mild critical point, its tunable solvent power, and the absence of solvent residue after depressurization. In this work the use of scCO2 as an unconventional medium to achieve the complexation with native and substituted cyclodextrins of over 50 drugs, which belong to different classes, are reviewed. This can be achieved with different approaches such as the “supercritical solvent impregnation” and “particle-formation” techniques. The different techniques are discussed to point out how they affect the complexation mechanism and efficiency, the physical state of the drug as well as the particle size distribution and morphology, which finally condition the release kinetics and drug bioavailability. When applicable, the results obtained for the same drug with various cyclodextrins, or different complexation techniques are compared with those obtained with conventional approaches.

Development of functionalized alginate dressing with mango polyphenols by supercritical technique to be employed as an antidiabetic transdermal system

Supercritical solvent impregnation (SSI) has been used to develop a transdermal delivery system consisting of an alginate dressing loaded with mango bioactive compounds. A mango leaf extract (MLE) was produced using CO2 + 50% ethanol at high pressure (200 bar) and temperature (80 °C). The extract presented antidiabetic activity as α-glucosidase inhibition (IC50 = 57.28 μg/mL), antioxidant (EC50 = 10.88 μg/mL), and antibacterial activity against S. aureus (IC50 = 68.77 μg/mL). The influence of impregnation conditions was studied by varying temperature (35–55 °C) and pressure (200–400 bar). Functionalized dressings obtained at 200 bar and 55 °C presented a high antioxidant capacity (~90% DPPH inhibition), as well as antidiabetic (37.5%/10 mg dressing) and antibacterial capacity (64.75%/100 mg dressing). HPLC analysis demonstrated the presence of bioactive compounds such as gallic acid, iriflophenone 3-C-β-D-glucoside, and mangiferin. SEM images showed the presence of MLE particles deposited on the alginate fibers.

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 °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.

Beyond confinement effects in Fischer-Tropsch Co/CNT catalysts

Fischer-Tropsch catalyst preparation parameters, such as cobalt precursor and impregnation solvent, determine structure and in fine catalytic performances of Co-based catalysts. Co particles of 3–7 nm mean size were prepared by incipient wetness impregnation on surface-oxidized CNT. In this work, the crucial impact of the chemistry operating between the Co precursor and the support during catalyst preparation on the catalyst properties is demonstrated, and the influence of CNT surface chemistry on catalyst characteristics is assessed. Very good correlations were found between: (i) the reduction degree of the catalysts and the concentration of the Co(OOC–) surface species; (ii) the Cohcp/Cofcc ratio and the amount of CO-releasing groups on the support surface; (iii) the extent of hydrogen spillover and the concentration of quinone surface groups. The initial catalytic activity could only be correlated to a combination of catalyst features: percentage of Cohcp, Co confinement, hydrogen spillover, and surprisingly the inverse of the Co initial particle size. No significant differences in SC5+ selectivity were observed, in accordance with a comparable final Co particle size. Finally, the stability of the catalyst can be correlated with the initial Co particle size and the percentage of Cohcp in the catalyst. These results confirm the significant impact of the precursor/support couple on the structure and performance of Co/CNT catalysts, and reveal for the first time an inverse correlation between Co particle size and activity, which is attributed to the confined Cohcp phase.

Biobased films of nanocellulose and mango leaf extract for active food packaging: Supercritical impregnation versus solvent casting

Antioxidant and antimicrobial free-standing films composed of nanofibrillated cellulose (NFC) and a polyphenolic-rich extract, viz. mango leaf extract (MLE), were produced via supercritical solvent impregnation (SSI) and conventional solvent casting film-processing methodologies. The CO2-assisted impregnation of NFC with MLE created robust films with thermal stability up to 250 °C, good mechanical performance (Young's modulus > 4.7 GPa), UV-light barrier properties, antioxidant capacity with maximum inhibition percentage of ca. 84%, and antimicrobial activity against Staphylococcus aureus (growth inhibition ≈ 37%) and Escherichia coli (growth inhibition ≈ 91%). The comparison of the NFC/MLE films prepared by SSI with those fabricated via solvent casting shows a clear advantage of the SSI methodology. Particularly, the antioxidant and antimicrobial activities are visibly higher in the films fabricated by the CO2-assisted impregnation of MLE into NFC. In fact, for the SSI films, the MLE components are mostly adsorbed at the surface and not in the bulk of the biopolymeric matrix, which translates into faster migrations and, hence, higher active properties. All these findings evinced the potential performance of the NFC/MLE films prepared by the eco-friendly SSI as UV-blocking, antioxidant, and antimicrobial bio-based materials for application as sustainable active food packaging.

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.

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.

Bimetallic AgPd/UiO-66 Hybrid Catalysts for Propylene Glycol Oxidation into Lactic Acid.

Different methods (the wetness impregnation of Ag and Pd precursors dissolved in water or acetonitrile solution, and the double solvent impregnation technique) were employed to immobilize Ag–Pd nanoparticles (NPs) into the pores of the microporous zirconium-based metal-organic framework known as UiO-66. The obtained materials were characterized by using nitrogen adsorption-desorption at −196 °C, powder X-ray diffraction, UV-Vis diffusion reflectance spectroscopy, and transition electron microscopy measurements. Special attention was paid to the acid and redox properties of the obtained materials, which were studied by using temperature-programmed desorption of ammonia (TPD-NH3) and temperature-programmed reduction (TPR-H2) methods. The use of a drying procedure prior to reduction was found to result in metallic NPs which, most likely, formed on the external surface and were larger than corresponding voids of the metal-organic framework. The formation of Ag–Pd alloy or monometallic Ag and Pd depended on the nature of both metal precursors and the impregnation solvent used. Catalytic activity of the AgPd/UiO-66 materials in propylene glycol oxidation was found to be a result of synergistic interaction between the components in AgPd alloyed NPs immobilized in the pore space and on the external surface of UiO-66. The key factor for consistent transformation of propylene glycol into lactic acid was the proximity between redox and acid-base species.

Study on the influence of technological factors on drug loading of poorly water-soluble drug on MCM-41 mesoporous carrier

The present study explored solvent impregnation drug loading process of the poorly soluble non-steroid anti-inflammatory drug indomethacin on MCM-41 type mesoporous silica carrier. Different technological factors that can influence drug-loading process as time of reaction, temperature, use of non-solvent as well as different ratios between drug and MCM-41 were studied. TEM and DLS were used to characterize physicochemical properties of obtained particles. The influence of drug-loading rate on dissolution process were studied using in-vitro release tests. Our results established that changes in explored technological factors could lead to different indomethacin loading. Moreover, the in-vitro release tests proved that drug loading rate had a direct influence on indomethacin release from MCM-41 particles. Our finding suggested that by tuning the main technological factors it would be possible different drug delivery systems with different drug loading rate to be obtained.

Co/CeO2 and Ni/CeO2 catalysts for ethanol steam reforming: Effect of the cobalt/nickel dispersion on catalysts properties

The Co/CeO2 and Ni/CeO2 catalysts were obtained by impregnation method with using different active phase precursors, different impregnation solvents and in presence of organic additive in order to improve cobalt/nickel dispersion and metal-support interaction. An addition of citric acid to precursor metal salt solution allowed to obtain their better dispersion and smaller metal particle size of Co/CeO2 and Ni/CeO2 samples. Whereas catalysts obtained from ammonia solution exhibited the largest size of metal particles. The key step for steam reforming of ethanol at 420 °C over both Co/CeO2 and Ni/CeO2 catalysts is ethanol dehydrogenation which occurs preferentially on cobalt/nickel terrace sites. But efficiency to cleavage C─C bond is favored by the edge/steps sites. Because nucleation of carbon requires relative large domains of flat terraces or larger ensemble sizes, the terrace atoms are involved in the catalyst deactivation under SRE conditions. Whereas the increase in fraction of edge and corner, i.e. better dispersion and strong metal-oxide interactions between metal and ceria could enhance the transfer of oxygen and thus improve the oxidation of carbon formed on the catalysts surface under SRE conditions. Catalytic performance of Ni/CeO2 catalysts in SRE reaction depends on the nickel crystallite size. Whereas catalytic performance of Co/CeO2 catalysts in SRE reaction is related to combination of cobalt crystallite size dependence and the oxidation state of the cobalt nanoparticles.

Boosting Ni Dispersion on Zeolite-Supported Catalysts for CO2 Methanation: The Influence of the Impregnation Solvent

In this work, an enhancement of Ni0 particle dispersion over zeolite-supported catalysts was intended by tuning the impregnation solvent. For this purpose, a series of 15 wt % Ni catalysts supporte...

Application of Supercritical Solvent Impregnation for Production of Zeolite Modified Starch-Chitosan Polymers with Antibacterial Properties

In the present study, supercritical solvent impregnation (SSI) has been applied to incorporate thymol into bio-composite polymers as a potential active packaging material. Thymol, a natural component with a proven antimicrobial activity, was successfully impregnated into starch-chitosan (SC) and starch-chitosan-zeolite (SCZ) films using supercritical carbon dioxide (scCO2) as a solvent. Experiments were performed at 35 °C, pressures of 15.5 and 30 MPa, and an impregnation time in the range of 4–24 h. The highest impregnation yields of SC films with starch to chitosan mass ratios of 1:1 and 1:2 were 10.80% and 6.48%, respectively. The addition of natural zeolite (15–60%) significantly increased the loading capacity of films enabling thymol incorporation in a quantity of 16.7–27.3%. FTIR and SEM analyses were applied for the characterization of the films. Mechanical properties and water vapor permeability of films before and after the impregnation were tested as well. Thymol release kinetics in deionized water was followed and modeled by the Korsmeyer-Peppas and Weibull model. SCZ films with thymol loading of approximately 24% exhibited strong antibacterial activity against E. coli and methicillin-resistant Staphylococcus (S.) aureus (MRSA).

Various metal organic frameworks combined with imidazolium, quinolinum and benzothiazolium ionic liquids for removal of three antibiotics from water

In this research, imidazolium, quinolinum and benzothiazolium based ionic liquids (ILs) were immobilized on a metal organic framework (MOF) by solvent impregnation or capillary action. The synthesized IL@MOF composite materials were characterized by FTIR, XRD, SEM and TGA methods and then applied in removal of tetracyclines (TCs) from aqueous samples. The presence of ionic liquids significantly improved the adsorption efficiency of the metal organic framework, with 82% or higher removal percentage was obtained for the three target TCs while the pristine MOFs adsorption efficiency was below 50%. This could be attributed to the ability of ILs to make complex interaction with target drugs via multiple intermolecular forces. Experimental results revealed the effects of three significant factors including pH, temperature and solid-liquid ratio, and optimum adsorption efficiency could be achieved at pH 8 and 30 °C when solid-liquid ratio = 1:2 was adopted. The adsorption kinetics was properly fitted with pseudo-second order model and Redlich-Peterson model could be used to describe the adsorption isotherm for three antibiotics; moreover, the adsorption was an endothermic and spontaneous process in nature. Finally, the adsorbed TCs could be desorbed efficiently and the performance of the IL@MOF sorbent was further verified by actual water samples.

Nitrogen and Oxygen Co-Doping Assisted Synthesis of Highly Dispersed Pd Nanoparticles on Hollow Carbon Spheres as Efficient Electrocatalysts for Oxygen Reduction Reaction.

Electrochemical reduction of O2 (oxygen reduction reaction; ORR) provides an opportunity to achieve the commercial application of clean energy, but it remains challenging, so the rational design of inexpensive and efficient electrocatalysts is required. Palladium-based electrocatalysts have emerged as a class of the most promising candidates for the ORR, which could accelerate O2 adsorption, dissociation, and electron transfer. However, the metal Pd atoms tend to aggregate into nanoparticles, driven by the tendency of the metal surface free energy to decrease, which significantly reduces the atom utilization efficiency and the catalytic performance. Herein, a facile double solvent impregnation method is developed for the synthesis of highly dispersed Pd nanoparticles supported on hollow carbon spheres (Pd-HCS), which could act as efficient electrocatalysts for the ORR in basic solution. Systematic investigation reveals that the nitrogen-containing and oxygen-containing functional groups (especially -COOH groups) are essential for achieving the homogenous dispersion of Pd nanoparticles. Significantly, the optimized Pd-HCS electrocatalyst with homogeneously dispersed Pd nanoparticles and Pd-N sites delivers high electrocatalytic activity for the ORR and excellent stability, without significant decay in onset potential and half-potential and good resistance to methanol crossover. This work offers a new route for the rational design of efficient ORR electrocatalysts toward advanced materials and emerging applications.