Supercritical Fluid Impregnation Research Articles

Advances in interdisciplinary medical and engineering research of intraocular lens surface modifications to prevent posterior capsule opacification.

Posterior capsule opacification (PCO), a common complication after cataract surgery, impacts a patient's long-term visual quality to various degrees. Although a neodymium:yttrium aluminum garnet (Nd:YAG) laser posterior capsulotomy is a very effective treatment, it may lead to a serial of complications. Accordingly, the search for simple, safe, and effective methods to prevent PCO has received widespread attention. Various researchers are committed to the interdisciplinary collaboration between medicine and engineering fields, such as functionalizing the surface of the intraocular lens (IOL) via supercritical fluid impregnation, coating the surface of the IOL, high-concentration drug immersion, and application of a drug delivery system, to effectively reduce the incidence and severity of PCO.

Supercritical fluid impregnation of microcrystalline cellulose derived from the agricultural waste with ibuprofen

The present study was aimed to investigate the feasibility of loading microcrystalline cellulose derived from the agricultural waste with poorly water-soluble drug by using supercritical carbon dioxide as impregnation medium. Operating parameters of supercritical impregnation process (pressure, temperature and time) were varied to in order to maximize loading of ibuprofen used as a model drug into microcrystalline cellulose. The efficiency of ibuprofen loading using supercritical impregnation and release kinetics studies of microcrystalline cellulose in two pharmaceutical forms, powder and tablets, were investigated.The highest amount of ibuprofen was impregnated in microcrystalline cellulose powder by using supercritical impregnation at 25 MPa and 40 °C for 24 h (9.43%). Increasing pressure in the range of 10 MPa–25 MPa and time from 2 h to 24 h favours loading of ibuprofen into microcrystalline cellulose. A higher loading efficiency at the same impregnation conditions was observed for powdered microcrystalline cellulose. Temperature change in range of 40–60 °C had negligible influence on loading efficiency. FT-IR spectroscopy analysis showed no evidence of chemical modification of microcrystalline cellulose after processing. In vitro drug release study showed that impregnated powder formulations released the total amount of ibuprofen immediately, while the impregnation of microcrystalline cellulose powder in the form of tablets led to the achievement of the sustained release profile.

Highly hydroxide-conductive anion exchange membrane with PIL@MOF-assisted ion nanochannels

A highly hydroxide-conducting anion exchange membrane with well-organized multi ion channels were fabricated via incorporating poly ionic liquids modified MIL101 (PIL@MIL101) into imidazolated poly (2,6-dimethyl-1,4-phenylene oxide) (ImPPO). 1-Vinyl-3-ethylimidzolium bromine was first immobilized in MIL101 cages via supercritical fluid impregnation method. Afterwards, the rigid-assisted ion nanochannels were constructed by in-situ polymerization of ionic liquids within the long-range ordered pores of MIL101. Meanwhile, PPO was functionalized by 1-ethyl-2-methyimidzolium to prepare comb-shaped ImPPO with enhanced microphase separation structure. Then the PIL@MIL101 was combined with ImPPO to fabricate hybrid anion exchange membrane with well-organized multiple ion channels. The OH− conductivity of the hybrid membrane significantly reached 138mS/cm at 80°C (176% higher than that of pristine membrane). Furthermore, the stability and mechanical properties of the hybrid membranes were remarkably enhanced. The excellent performances render the hybrid membrane a good candidate for the application in anion exchange membrane fuel cells.

Supercritical Fluid Impregnation of Broken Stone with Deasphaltizate Obtained from Oil Residue

Results are presented concerning the studies on obtaining a heavy oil residue, its deasphalting and the impregnation of crushed carbonate stone with deasphaltizate. The heavy oil residue is obtained via the separation of extra-heavy crude oil using a steam thermal method. The deasphalting of the oil residue and the impregnation of crushed carbonate stone are carried out using a propane-butane solvent in the liquid and supercritical fluid state, respectively.

Impregnation of carbonate rock by deasphalted oil with the use of a supercritical fluid impregnation process

ABSTRACTThe authors present the results of investigation and experimental implementation of several processes: production of heavy oil residue and its deasphaltizing and impregnation of carbonate rock with deasphalted oil. Heavy oil residue has been produced during fractionation of highly-vicious oil by steam-thermal method. Deasphaltizing of oil-residue and impregnation of carbonate rock are implemented with the use of extraction and supercritical fluid impregnation processes with propane-butane solvent.

Stable “coloured” states of spirooxazine photochrom molecules immobilized in polymer matrixes by supercritical carbon dioxide

Formation of long-lived coloured forms of indoline spirocompounds (spirooxazines and spiropyrans) molecules under matrix immobilization in polar polymer of different chemical structure using supercritical fluid impregnation is studied. Some of such systems acquire additional optical characteristics besides colour – they become fluorophores. Mechanisms of observed changes in optical properties and long-term stability of the resulting coloured forms of indoline spirooxazine in polymers are discussed. Electronic absorption spectra of such coloured forms were recorded in supercritical carbon dioxide medium as well as on air. The results can be applied for creation of optical, biomedical and electronic devices and stable fluorescence composite coverings.

Improvement of functionality of carbonate macadam via supercritical fluid impregnation with bituminous compounds

A comprehensive process for the deasphaltizing of heavy oil residue and subsequent treatment (impregnation using a solvent in the supercritical fluid state) of a carbonate macadam by bituminous compounds (deasphaltizate) is developed. The purpose is to improve the functionality of the material and, above all, to reduce its water absorption capacity. The process parameters are specified based on the newly obtained data on the thermal capacity of heavy oil residue and deasphaltizate. The results of the process of experimental implementation and the characteristics of impregnated macadam, including the water absorption capacity which decreased from 3.6 to 0.54%, are presented.

Photo–induced processes in Ag and Eu β-diketonates incorporated into aerogel matrix of silicon dioxide by supercritical fluid impregnation

Samples of silicon dioxide aerogel with embedded Ag and Eu β-diketonate molecules are obtained by impregnation in supercritical carbon dioxide (SC-CO2). The sample impregnated by Eu(tta)3 molecules possesses photoluminescence properties. Moreover, adsorption of Eu(tta)3 on the walls of the pores results in a strong broadening of the Stark components of its photoluminescence spectra. It is found that aerogel impregnation by AgFOD molecules followed by laser irradiation causes the formation of Ag nanoparticles in the sample volume as a result of AgFOD photolysis and subsequent diffusion self-assembly. The Ag nanoparticles assemble into filament structures due to self-organization as they focus laser radiation.

Solubility of Poly(vinylpyrrolidone) with Different Molecular Weights in Supercritical Carbon Dioxide

For studying the phase behavior of poly(vinylpyrrolidone) (PVP) with different molecular weights in supercritical carbon dioxide (SCCO2), the equilibrium solubilities of PVP with different molecular weights of 10000, 24000, and 58000, which were widely used as polymeric carriers in supercritical fluid impregnation technology, were measured in SCCO2 at temperatures of (313, 323, 333, and 343) K and in the pressure range of (9.0 to 18.0) MPa by the dynamic method. The effects of pressure, temperature, and molecular weight of solute on PVP solubility were investigated by comparing the solubility data in SCCO2, and it was found that the solubility of PVP in SCCO2 increased with pressure and temperature increasing for the same solute molecular weight and with the solute molecular weight decreasing at the same operational conditions. The solubility data of PVP in SCCO2 were correlated by five density-based semiempirical models (Chrastil, M-S-T, K-J, S-S, A-L), and satisfactory correlation results were achieved ...

Fabrication of Ni mold for nanoimprint lithography by combining two supercritical fluid-based deposition technologies

A nano-scale three-dimensional (3D) Ni mold fabrication technique was developed for nanoimprint lithography by filling Ni into a patterned polymer resist film, 100 nm in width and with an aspect ratio of 1. This was achieved by a combination of two supercritical fluid-based technologies: supercritical fluid impregnation (SCFI) of Pd and supercritical fluid deposition (SCFD) of Ni. Pd nanoparticles were formed primarily on the surface of the 3D patterned resist film by SCFI to provide a catalytic effect on the resist surface, which initiated the subsequent Ni-SCFD. Ni was then filled into the patterned resist by SCFD, exploiting its superior gap-filling capabilities. Our proposed scheme has the potential to be applied to structures scaled down to below 100 nm.

Novel supercritical carbon dioxide impregnation technique for the production of amorphous solid drug dispersions: a comparison to hot melt extrusion.

The formulation of BCS Class II drugs as amorphous solid dispersions has been shown to provide advantages with respect to improving the aqueous solubility of these compounds. While hot melt extrusion (HME) and spray drying (SD) are among the most common methods for the production of amorphous solid dispersions (ASDs), the high temperatures often required for HME can restrict the processing of thermally labile drugs, while the use of toxic organic solvents during SD can impact on end-product toxicity. In this study, we investigated the potential of supercritical fluid impregnation (SFI) using carbon dioxide as an alternative process for ASD production of a model poorly water-soluble drug, indomethacin (INM). In doing so, we produced ASDs without the use of organic solvents and at temperatures considerably lower than those required for HME. Previous studies have concentrated on the characterization of ASDs produced using HME or SFI but have not considered both processes together. Dispersions were manufactured using two different polymers, Soluplus and polyvinylpyrrolidone K15 using both SFI and HME and characterized for drug morphology, homogeneity, presence of drug-polymer interactions, glass transition temperature, amorphous stability of the drug within the formulation, and nonsink drug release to measure the ability of each formulation to create a supersaturated drug solution. Fully amorphous dispersions were successfully produced at 50% w/w drug loading using HME and 30% w/w drug loading using SFI. For both polymers, formulations containing 50% w/w INM, manufactured via SFI, contained the drug in the γ-crystalline form. Interestingly, there were lower levels of crystallinity in PVP dispersions relative to SOL. FTIR was used to probe for the presence of drug-polymer interactions within both polymer systems. For PVP systems, the nature of these interactions depended upon processing method; however, for Soluplus formulations this was not the case. The area under the dissolution curve (AUC) was used as a measure of the time during which a supersaturated concentration could be maintained, and for all systems, SFI formulations performed better than similar HME formulations.

The influence of electron-donating compounds on the electronic state of spiroantrooxazine incorporated into thermoplastic polymers via supercritical fluid impregnation

Aromatic electron-donating compounds (EDCs), such as toluene and dibutyl phthalate, were found to affect the content of photochromic spiroantrooxazine (SAO) incorporated into thermoplastic polymer matrices (for example, polyvinylchloride and F-42 fluoropolymer) via the method of supercritical fluid impregnation (SCFI) and influence the ratio of colored B and B x forms of SAO. The presence of EDCs in impregnated polymers induces reciprocal transformations between B and B x colored forms of SAO and increases the rate of their “dark” bleaching.

Supercritical Fluid Impregnation of Essential Bark Oil in Copolymers of L-Lactide with 7-Membered Cyclic Compounds

In order to develop a novel controlled-release material, we previously attempted to impregnate poly(L-lactide) (poly(L-LA)), poly(L-LA-ran-CL) (CL: e-caprolactone) or poly(L-LA-ran-TEMC) (TEMC: tetramethylene carbonate) with low boiling point, organic useful compounds using supercritical carbon dioxide (scCO2) as the solvent. In this work, the factors influencing impregnation of poly (L-LA) random copolymers with useful compounds were investigated under scCO2 using the copolymers previously used. The influence of temperature, pressure, and time on the impregnation contents of the useful compounds on the copolymers was evaluated. The polymer used, which is a base of this material, was poly(L-LA-ran-CL), poly(L-LA-ran-TEMC), or poly(L-LA-ran-DXO) (DXO: 1,5-dioxepan-2-one). Statistical random copolymers of L-LA with CL, TEMC, or DXO were synthesized using Sn(oct)2 as a catalyst at 150°C for 24 h without solvent. Preparation of the controlled-release materials was carried out using essential bark oil from Thujopsis dolabrata var. hondae and synthetic L-LA random copolymers as a base material under scCO2. The impregnation experiment, which investigated the influence of pressure, was conducted in the range of 10 to 20 MPa. The influence of temperature on impregnation was carried out at 40°C to 100°C. Impregnation time was varied from 1 to 5 h. The pressure of essential oil impregnated into poly(L-LA) random copolymers was the highest at 14 MPa. In the influence of temperature on impregnation, the amount of essential oil increased with increasing temperature.

Polymer-filled microcontainers for oral delivery loaded using supercritical impregnation

In the last years a large variety of drug delivery systems have been developed to improve bioavailability of therapeutics in oral administration. An increasing interest has arisen in reservoir-based microdevices designed for active ingredients like water insoluble compounds and fragile biomolecules. Such microdevices are designed to protect the active ingredient against degradation and deactivation, and to allow cytoadhesion and unidirectional drug release. There are few works which optimize the drug loading step and often therapeutics are dosed in the microdevices through laborious and time consuming procedures. This work proposes an effective loading technique for a poorly soluble model drug in microcontainers, by combining inkjet printing and supercritical fluid impregnation. Well defined quantities of poly(vinyl pyrrolidone) (PVP) solutions are dispensed into microcontainers by inkjet printing with a quasi-no-waste performance. Then ketoprofen is impregnated in the polymer matrix by using supercritical carbon dioxide (scCO2) as loading medium. The amount of polymer is controlled by the volume and the number of droplets of dispensed polymer and drug loading is tuned by varying the impregnation parameters. Compared to solid dispersions of the same drug and polymer, scCO2-impregnated microcontainers exhibit a more reproducible drug loading and a faster dissolution rate of the active compound which allows drug release to be modulated. The combination of these loading techniques potentially allows the high throughput fabrication of microdevices for oral drug delivery with a safe and solvent-free solution.

Optical properties of europium(III) β-diketonate/polymer-doped systems using supercritical carbon dioxide

The optical properties of fluoropolymers and polypropylene doped with europium(III) β-diketonates Eu(L)3·2H2O and Eu(L)3phen (L: fod=6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato, bta=4,4,4-trifluoro-1-phenyl-1,3-butanedione, tta=4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, and phen=1,10-phenanthroline) using supercritical carbon dioxide were investigated by absorption and emission spectra. A comparative analysis of the PL decay times of Eu3+ ions in the initial europium (III) β-diketonates and impregnated fluoropolymers was carried out. The supercritical fluid (SCF) impregnation of polymer samples with europium(III) β-diketonates containing 1,10-phenanthroline was found to be obstructed differently depending on the type of ligand in the entire investigated impregnation temperature range (TSCF=50–90°С). It is shown that from the variety of Eu(L)3phen only Eu(fod)3phen can be introduced into the polymer matrix by this method.

Metallized nanotube polymer composites via supercritical fluid impregnation

Although many metal decorated nanotubes and nanowires appear in the literature, well-dispersed metal decorated nanotube polymer composites have rarely been reported because of the excessive density mismatch between the decorated nanotubes and polymer matrix. Here, we report a novel method to prepare well-dispersed, highly functional, metallized nanotube polymer composites (MNPCs) that possess remarkably improved electrical conductivity and mechanical toughness. The MNPCs are prepared by supercritical fluid impregnation of an organometal compound into a premade well-dispersed single wall carbon nanotube-polymer composite film. The infused precursor preferentially migrates towards the nanotubes to undergo spontaneous reduction and form nanometer-scale metal particles leading to an increase in the conductivity of the MNPC films. The environmentally friendly supercritical fluid impregnation process significantly improved the toughness of the composite films, regardless of the presence of metal. Additional functionality can be imparted into the resulting MNPC by infusing other precursors such as magnetic and catalytic metal compounds. © 2011 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys, 2012

Formation of long-lived fluorescent merocyanine forms of spiro compounds via their immobilization into polymer matrices from supercritical carbon dioxide medium

It is shown that the supercritical fluid (SCF) impregnation of polymers containing phenylphenol and halide polar groups (polycarbonate, fluoroplastic, poly(vinyl chloride)) with spiro compounds leads to conformational rearrangements resulting in stabilization of merocyanine forms of the photochromes. The effect of the formation of long-lived colored form B of the photochromes immobilized in the polymer matrix in SCF medium, revealed earlier for spinroanthroxazine, is of more general nature: it is observed and investigated by us for a number of spiro compounds SCF-impregnated into polar polymer matrices of different chemical structures. It was found that the colored forms of spiro compounds introduced in halogenated matrices feature intense photoluminescence.

Dual stimuli responsive poly(N-isopropylacrylamide) coated chitosan scaffolds for controlled release prepared from a non residue technology

The first decade of the 21st century saw an increasing interest in the development of devices and biomaterials for delivery of bioactive substances that can be controlled by external stimuli. Herein we report the production of smart partially biodegradable scaffolds that exhibit pH- and temperature-responsive behavior and their effects on the release of a model protein and a drug of low molecular weight. Chitosan (CHT) scaffolds (pH sensitive) were coated/impregnated with a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), by in situ synthesis of PNIPAAm within CHT micropores. Microarchitectural analysis by scanning electron microscopy and mercury intrusion porosimetry demonstrate that the coating of the pores inner structure could be efficiently achieved without a considerable loss of porosity of native CHT-scaffolds. Two different strategies were used to impregnate the polymeric devices: supercritical fluid impregnation for scaffold uptake with a model low molecular weight drug (ibuprofen) and bulk loading to impregnate a model protein (bovine serum albumin, BSA). The release profiles showed a specific pattern according to pH and temperature. PNIPAAm temperature responsiveness is able to control BSA release but ibuprofen (Ibu) release is only mediated by pH environmental conditions.

Cyproconazole impregnation into wood using sub- and supercritical carbon dioxide

Supercritical fluid (SCF) impregnation is a promising preservative treatment method for wood. In order to commercialize the sub- and supercritical CO2 biocide treatment, better understanding of the fluid phase and its effect on treatment results have to be demonstrated and developed. Preservative treatability under super- and subcritical fluid conditions was evaluated using radiata pine sapwood, and treating characteristics in relation to different fluid phases and treatability were discussed. Various treatment conditions resulted in varying biocide retentions and distributions. Higher pressure conditions enhanced biocide retentions resulting from increasing biocide input in the applied saturation method. Subcritical CO2 condition produced higher biocide retentions and little retention gradients from face to core. Subcritical CO2 treatment has a couple of benefits such as investment costs and energy consumption compared with supercritical CO2.

Modification of the optical properties of fluoropolymers by supercritical fluid impregnation with europium β-diketonates

Optical properties of a number of fluoroacrylate-based fluoropolymers doped with europium β-diketonates by means of supercritical fluid impregnation were studied. The influence of the type of polymer matrix on the process of impregnation of europium β-diketonate molecules into it and the evolution of the optical properties of the doped polymers during a long-term storage were revealed. A comparative analysis of the quantum yield (λexc = 300 and 380 nm) and thermosensitivity of the photoluminescence of Eu3+ ions for different europium β-diketonates and polymer structures was performed. It was demonstrated that the supercritical fluid extraction of unreacted photoinitiator residues from polymer samples makes it possible to substantially enhance their transparency at wavelengths shorter than 300 nm.