Adsorptive Precipitation Research Articles

Supercritical adsorptive precipitation of coenzyme Q10 on sodium alginate aerogel

Supercritical adsorptive precipitation (SAP) can be employed to load hydrophobic bioactives onto aerogels formed using the Pressurized Gas eXpanded liquid (PGX) Technology to prepare novel delivery systems. The objective of this study was to investigate the effects of SAP parameters on the coenzyme-Q10 (CoQ10) loading onto PGX-processed sodium alginate (PGX-SA) and its physicochemical properties. Within the ranges tested, higher recirculation time (50 min) and flow rate (262 mL/min), lower pressure (200 bar), and higher surface area biopolymer resulted in higher CoQ10 loading (46.9 ± 3.0% w/w). Helium ion microscopy revealed a rather uniform coating of PGX-SA fibrils, covering the porous structure. Thermal and crystallinity analyses demonstrated a decrease in CoQ10 crystallinity. CoQ10-loaded PGX-SA suspension in water remained stable for 50 days at 4 °C. These findings demonstrate the potential of PGX Technology combined with SAP for developing delivery systems for hydrophobic bioactives to increase water dispersibility and suspension stability, which can boost their bioavailability.

Drug-impregnated, pressurized gas expanded liquid-processed alginate hydrogel scaffolds for accelerated burn wound healing

While the benefits of both hydrogels and drug delivery to enhance wound healing have been demonstrated, the highly hydrophilic nature of hydrogels creates challenges with respect to the effective loading and delivery of hydrophobic drugs beneficial to wound healing. Herein, we utilize pressurized gas expanded liquid (PGX) technology to produce very high surface area (~200 m2/g) alginate scaffolds and describe a method for loading the scaffolds with ibuprofen (via adsorptive precipitation) and crosslinking them (via calcium chelation) to create a hydrogel suitable for wound treatment and hydrophobic drug delivery. The high surface area of the PGX-processed alginate scaffold facilitates >8 wt% loading of ibuprofen into the scaffold and controlled in vitro ibuprofen release over 12–24 h. In vivo burn wound healing assays demonstrate significantly accelerated healing with ibuprofen-loaded PGX-alginate/calcium scaffolds relative to both hydrogel-only and untreated controls, demonstrating the combined benefits of ibuprofen delivery to suppress inflammation as well as the capacity of the PGX-alginate/calcium hydrogel to maintain wound hydration and facilitate continuous calcium release to the wound. The use of PGX technology to produce highly porous scaffolds with increased surface areas, followed by adsorptive precipitation of a hydrophobic drug onto the scaffolds, offers a highly scalable method of creating medicated wound dressings with high drug loadings. Statement of SignificanceWhile medicated hydrogel-based wound dressings offer clear advantages in accelerating wound healing, the inherent incompatibility between conventional hydrogels and many poorly water-soluble drugs of relevance in wound healing remains a challenge. Herein, we leveraged supercritical fluids-based strategies to both process and subsequently impregnate alginate, followed by post-crosslinking to form a hydrogel, to create a very high surface area alginate hydrogel scaffold loaded with high hydrophobic drug contents (here, >8 wt% ibuprofen) without the need for any pore-forming additives. The impregnated scaffolds significantly accelerated burn wound healing while also promoting regeneration of the native skin morphology. We anticipate this approach can be leveraged to load clinically-relevant and highly bioavailable dosages of hydrophobic drugs in hydrogels for a broad range of potential applications.

Preparation of PGX-dried gum arabic and its loading with coQ10 by adsorptive precipitation

The Pressurized Gas eXpanded (PGX) liquid technology was developed for simultaneously drying and purifying high molecular weight biopolymers, resulting in nano/micro-sized powders with large surface areas that can be loaded with various bioactives. The preparation of PGX-dried gum arabic (GA) and its loading by adsorptive precipitation with coenzyme Q10 (coQ10) was investigated in a two-step process. In step one, the effects of feed solution concentration, flow rates and flow rate ratios on the PGX-processed GA were studied. Low flow rates and high ratios resulted in larger (up to 65 m2/g) surface areas. In the second step, the impact of different recirculation flow rates and pressurization rates on the coQ10 loading was tested. Only an increased pressurization rate (4.5 vs. 1.5 MPa/min) showed an effect, increasing the coQ10 loading from 0.6 to 2.0% w/w. PGX drying followed by adsorptive precipitation shows great potential for the development of bioactive delivery systems.

Characterization of oat beta-glucan and coenzyme Q10-loaded beta-glucan powders generated by the pressurized gas-expanded liquid (PGX) technology

The physicochemical properties of the oat beta-glucan powder (BG) and coenzyme Q10 (CoQ10)-loaded BG powder (L-BG) produced by the pressurized gas-expanded liquid (PGX) technology were studied. Helium ion microscope, differential scanning calorimeter, X-ray diffractometer, AutoSorb iQ and rheometer were used to determine the particle morphology, thermal properties, crystallinity, surface area and viscosity, respectively. Both BG (7.7μm) and L-BG (6.1μm) were produced as micrometer-scale particles, while CoQ10 nanoparticles (92nm) were adsorbed on the porous structure of L-BG. CoQ10 was successfully loaded onto BG using the PGX process via adsorptive precipitation mainly in its amorphous form. Viscosity of BG and L-BG solutions (0.15%, 0.2%, 0.3% w/v) displayed Newtonian behavior with increasing shear rate but decreased with temperature. Detailed characterization of the physicochemical properties of combination ingredients like L-BG will lead to the development of novel functional food and natural health product applications.

Adsorptive precipitation of co-enzyme Q10 on PGX-processed β-glucan powder

The recently developed Pressurized Gas eXpanded (PGX) liquid technology allows drying of high molecular weight water-soluble biopolymers, resulting in nano/micro-sized powders. The objective of this study was to investigate the adsorptive precipitation of co-enzyme Q10 (coQ10), a natural antioxidant, on PGX-processed β-glucan, an oat-derived biopolymer. CoQ10 is first solubilized in supercritical CO2, which then carries it to the PGX-processed β-glucan, resulting in the adsorptive precipitation. Different parameters, including the mode of operation (separate vs. simultaneous saturation and precipitation cycles), CO2 flow rate (70–465 mL/min), time of operation (15–90 min) and depressurization rate (0.5–13.0 MPa/min) were tested. Maximum coQ10 loading (18% w/w) was obtained after 45 min of operation at 40 °C, 30.0 MPa and 190 mL/min of CO2 flow rate, followed by a depressurization rate of 13.0 MPa/min. The two-step PGX process shows great potential for the preparation of bioactive-biopolymer delivery systems.

Enhanced removal of Pb(II) by supported nanoscale Ni/Fe on hydrochar derived from biogas residues

A functionalized carbonaceous material was prepared via hydrothermal carbonization (HTC) of biogas residues and denoted as hydrochar (HC). The obtained HC was used to synthesize a hybrid (Ni/Fe-HC) to conduct Pb(II) removal from aqueous solution. SEM images show that Ni0/Fe0 was anchored tightly to HC particles due to a cellular structure of HC formed during HTC. Complete Pb(II) removal (>99.5%) was achieved within 1.5h using Ni/Fe-HC whereas more than 85% of Pb(II) remained in bulk solution after 10h with bare HC. SEP results indicate that Pb(II) was mainly associated with the fraction bound to carbonates and Fe–Mn oxides in the spent Ni/Fe-HC particles. Consequently, the adsorptive precipitation and specific adsorption dominated Pb(II) removal by Ni/Fe-HC despite minor reduction of Pb(II) to Pb0. However, the reduction of Pb(II) to Pb0 was conducted by the catalytically generated atomic hydrogen rather than Ni/Fe nanoparticles as electron donor. Ni/Fe-HC not only acted as an effective adsorbent for Pb(II) but also played a role of catalyst to generate atomic hydrogen. HC prepared with biogas residues can be used as an excellent supporting material to prepare a hybrid of Ni/Fe-HC for Pb(II) removal.

Preparation, Characterization and Application of Silver Chloride-Eosin Y Inclusion Material

Abstract From the adsorptive precipitation of Cl–, eosin Y (EY) and Ag+, we developed in-situ inclusion of EY into growing silver chloride particles to form ternary electronegative micro-conductors. The composition of the particles was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES), ion chromatography (IC) and spectrophotometry and the size and pattern of the particles characterized by the particle size analysis, X-ray diffractometer (XRD), scanning electron microscopy (SEM), and thermogravimetry. The results showed that the in-situ inclusion of EY into AgCl crystal particles in layer-by-layer and the supermolecular complex {[(AgCl)50EY]n}2n– was formed in cubic and globe-like shape. The ternary inclusion particles adsorbed cationic dyes selectively, rapidly and with high efficiency. A representative cationic dye, victoria blue B (VBB), was used to investigate the performance of the ternary particles as adsorbents and the mechanism involved. The equilibrium adsorption capacity of the ternary particles is 353 mg/g VBB, over 10 times higher than absorption to the silver chloride–only particles and over 3 times to activated carbon. Moreover, the adsorption approached the equilibrium in 10 min, which is much less than that with activated carbon in about 2 h. This work advanced a sample method for preparation of the supramolecular inclusion materials as dye adsorbent and it provided a simple, efficient and practical approach for the recovery or removal of organic substances from aqueous.

Preparation and characterization of silver thiocyanate – tetrabromo-tetrachlorofluorescein inclusion material and its adsorption to synthetic dye

From the adsorptive precipitation of SCN −, tetrachloro-tetrabromofluorescein (TBTCF) and Ag +, we found in-situ embedment of TBTCF into growing silver thiocyanate particles to form ternary electronegative inclusion material. The composition, size and phase of the material were determined by spectrophotometry and ICP and characterized by XRD, SEM, etc. The results showed that in-situ inclusion particles {[Ag(SCN)] m (TBTCF)} n 2 n− ( m = 33 ± 11) were formed. The inclusion particles adsorbed cationic dyes selectively and rapidly. A representative cationic dye, ethyl violet (EV), was used to investigate the performance of the ternary inclusion particles and the mechanism involved. The equilibrium adsorption capacity of the Ag(SCN)/TBTCF inclusion particles is 202 mg/g EV, over 14 times higher than absorption to the silver thiocyanate–only particles and slightly more than activated carbon. Moreover, the adsorption approached the equilibrium in 10 min, which is much less than that with activated carbon in about 2 h. In this work, a simple preparation method of the inclusion material as dye adsorbent was established and it will play an important role in the removal or recovery of cationic organic substances from aqueous.

Rapid determination of Cl − by light-absorption ratio variation approach using Cl −–eosin Y–Ag + adsorptive precipitation

The adsorptive precipitation between eosin Y (EY) and AgCl colloids at pH 3.73 caused the sensitive color change of the solution. The reaction mechanism between EY and AgCl was analyzed and this reaction was used for determination of Cl − in trace level by the light-absorption radio variation approach.

Molekülabsorptionsspektrometrie mit elektrothermischer verdampfung in einer graphitrohrküvette: 12. Tei. bestimmung von cl-species in selen und A IIIB V-halbleitermaterialien

( Molecular absorption spectrometry with electrothermal vaporization in a graphite cuvette. Part 12. Determination of chloride species in selenium and A IIIB V-semiconductor materials after separation of the traces by adsorptive precipitation and distillation. ) The determination of traces of chloride in chloride-dosed selenium and in gallium arsenide by molecular absorption spectrometry of AlCl is described. The traces of chloride are separated by adsorption precipitation (AgCl/Al 2O 3). The AgCl is dissolved in ammonia. After addition of Al 3+ and Ba(OH) 2 the molecular absorption of AlCl is measured at 261.4 nm. It is possible to determine 0.2 μg g −1 Cl in 500 mg of Se or GaAs.

Cup and Ring Markings

IN reply to Mr. Abbott's letter in NATURE of July 21, p. 652, I regret that he did not see the photographs to which I referred; had he done so he would have appreciated the difference between these and his own. As there is no tangible evidence that such reconstructed surfaces are due either to gelic selection or adsorptive precipitation, I submit that, pending the proving of the gel theory, it is safer to describe the process as “concretionary,” for this term covers much ignorance, and is, at least, non-committal.

Cup and Ring Markings

MAY I query Mr. Carus-Wilson's opinions in his letter in NATURE of June 23 (p. 523)? I have, alas! seen only one case (at Ilkley) of these markings, but have long been interested in the peculiar weathering of mortar which is common on the north side of old buildings near the sea. My view is that it is quite distinct from the cup and rings. The change in mortar is, I suspect, one of adsorptive precipitation, so well explained by Mr. S. C. Bradford in NATURE of March 23, 1916, and elsewhere.