| 1. |
- Aragao, Rosa, et al.
(författare)
-
Immobilization of Clostridium acetobutylicum DSM 792 as macroporous aggregates through cryogelation for butanol production
- 2014
-
Ingår i: Process Biochemistry. - : Elsevier BV. - 1873-3298 .- 1359-5113. ; 49:1, s. 10-18
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a new cell immobilization technique is presented. Cells of Clostridium acetobutylicum DSM 792 form a macroporous aggregate through cryogelation with concomitant crosslinking together with activated polyethyleneimine (PEI) and poly(vinyl alcohol) (PVA). The cell based cryogel presents a highly porous, elastic structure with walls consisting of densely packed crosslinked cells. The immobilization process maintained the viability of cells as new bacterial cells were observed when gel-plugs were incubated in liquid medium, glucose was consumed and solvent production was observed. Solvent production was improved 2.7-fold in immobilized cells in comparison to free cells. It was possible to reuse the gel-plugs 3-5 times in partial or completely fresh medium, reaching a maximum butanol concentration in the broth of 18.2 g/l and yield of 0.41 (g/g) in one of the cycles. The use of cells based cryogels can be a good alternative for improvement of acetone-butanol-ethanol (ABE) process as cells are immobilized in a macroporous structure with low limitations for mass transfer with potential for high yield production. (C) 2013 Elsevier Ltd. All rights reserved.
|
|
| 2. |
- Berillo, Dmitry, et al.
(författare)
-
Cryogelation of Chitosan Using Noble-Metal Ions: In Situ Formation of Nanoparticles.
- 2014
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1526-4602 .- 1525-7797. ; 15:6, s. 2246-2255
-
Tidskriftsartikel (refereegranskat)abstract
- One of the purposes of the project was to develop the method of preparation of 3D macroporous hydrogel with a structure of interconnected pores by the use of noncovalent interactions. The combination of chitosan and noble-metal complexes was investigated as cross-linking agents for the preparation of ionic cryogels (ICs). Furthermore, the treatment of the ICs containing gold complex by glutaraldehyde results in spontaneous formation of gold nanoparticles (AuNPs) and chemical cross-linking of the cryogel. The characterization of prepared macroporous materials was carried out by the use of FTIR, SEM, TEM techniques, and texture analyzer. A new strategy for control of size distribution of AuNPs was suggested. The size distribution of obtained AuNPs and their population inside of walls of cryogels was estimated. A method for quantifying unreacted chloroauric acid in the presence of acetic acid was proposed. The possibility of use of prepared cryogels with immobilized AuNPs as a catalytic flow through reactor is shown.
|
|
| 3. |
- Berillo, Dmitry, et al.
(författare)
-
Formation of macroporous self-assembled hydrogels through cryogelation of Fmoc-Phe-Phe.
- 2012
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 368:1, s. 226-230
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, it was found that macroporous hydrogels were formed when self-assembly of fluorenyl-9-methoxycarbonyl (Fmoc)-diphenylalanine (Phe-Phe) peptides was induced using glucono-δ-lactone (GdL) in apparently frozen samples. Formed cryogels exhibited a heterogeneous structure with pore walls of densely packed fibres of assembled dipeptides and pores in the range 10-100μm. Hydrogels formed from the same composition above the freezing point exhibited a homogenous structure without any apparent porosity. The formed gels were characterised using microscopy techniques, CD-spectroscopy and stress sweeps. The cryogels exhibited less mechanical strength than the hydrogels that might be due to the heterogeneous structure of the former. It appeared that the self-assembled peptide both in the cryo- and hydrogel maintained the β-sheet structure commonly attributed to these.
|
|
| 4. |
- Berillo, Dmitriy, et al.
(författare)
-
Oxidized Dextran as Crosslinker for Chitosan Cryogel Scaffolds and Formation of Polyelectrolyte Complexes between Chitosan and Gelatin.
- 2012
-
Ingår i: Macromolecular Bioscience. - : Wiley. - 1616-5195 .- 1616-5187. ; 12:8, s. 1090-1099
-
Tidskriftsartikel (refereegranskat)abstract
- Macroporous scaffolds composed of chitosan and using oxidized dextran as a crosslinker are produced through cryogelation. Introducing gelatin as a third component into the structure results in the formation of mesopores in the pore walls, which are not seen if gelatin is excluded. The mesoporous structure is explained by the formation of polyelectrolyte complexes between chitosan and gelatin before crosslinking takes place. The scaffolds exhibit highly elastic properties withstanding compressions up to 60%. The in vitro biocompatibility of the cryogels is evaluated using fibroblasts from a mouse cell line (L929) and it is seen that the cells adhere and proliferate on the scaffolds. The mesoporous structure seems to have a positive effect on proliferation.
|
|
| 5. |
- Elowsson, Linda, et al.
(författare)
-
Evaluation of macroporous blood and plasma scaffolds for skeletal muscle tissue engineering
- 2013
-
Ingår i: Biomaterials Science. - : Royal Society of Chemistry (RSC). - 2047-4830 .- 2047-4849. ; 1:4, s. 402-410
-
Tidskriftsartikel (refereegranskat)abstract
- The field of tissue engineering has a growing need for suitable scaffold materials to become attractive as a clinical therapy. To use a completely autologous construct to repair a damaged or diseased tissue is an appealing thought. As a model system, two types of scaffolds were prepared from biological fluids: blood and plasma. The prepared scaffolds formed a macroporous structure with elastic mechanical properties that were further evaluated with myoblast cell line (C2C12) cultivation and transplantation into mouse skeletal muscle. The cells were found to attach, proliferate, and migrate through all the different scaffolds. Moreover, the cells underwent myogenic differentiation, showing typical cell morphology aligned in a parallel fashion. An increased level of myogenin mRNA was found with the time of culture. Furthermore, myogenic markers MyoD1, desmin, myogenin and myosin, as well as beta-dystroglycan and the laminin alpha 2 chain, were found to be expressed. In vivo data indicated that the scaffolds degraded and were replaced with regenerated muscle fibres. We conclude that the two types of macroporous scaffolds based on blood or plasma have potential in the field of skeletal muscle tissue engineering.
|
|
| 6. |
- Elowsson, Linda, et al.
(författare)
-
Porous protein-based scaffolds prepared through freezing as potential scaffolds for tissue engineering.
- 2012
-
Ingår i: Journal of Materials Science: Materials in Medicine. - : Springer Science and Business Media LLC. - 1573-4838 .- 0957-4530. ; 23:10, s. 2489-2498
-
Tidskriftsartikel (refereegranskat)abstract
- Successful tissue engineering with the aid of a polymer scaffold offers the possibility to produce a larger construct and to mould the shape after the defect. We investigated the use of cryogelation to form protein-based scaffolds through different types of formation mechanisms; enzymatic crosslinking, chemical crosslinking, and non-covalent interactions. Casein was found to best suited for enzymatic crosslinking, gelatin for chemical crosslinking, and ovalbumin for non-covalent interactions. Fibroblasts and myoblasts were used to evaluate the cryogels for tissue engineering purposes. The stability of the cryogels over time in culture differed depending on formation mechanism. Casein cryogels showed best potential to be used in skeletal tissue engineering, whereas gelatin cryogels would be more suitable for compliable soft tissues even though it also seemed to support a myogenic phenotype. Ovalbumin cryogels would be better suited for elastic tissues with faster regeneration properties due to its faster degradation time. Overall, the cryogelation technique offers a fast, cheap and reproducible way of creating porous scaffolds from proteins without the use of toxic compounds.
|
|
| 7. |
- Guzmán, Daniel, et al.
(författare)
-
Preparation of hydrophilic poly(3-hydroxybutyrate) macroporous scaffolds through enzyme-mediated modifications
- 2011
-
Ingår i: Journal of Bioactive and Compatible Polymers. - : SAGE Publications. - 0883-9115 .- 1530-8030. ; 26:5, s. 452-463
-
Tidskriftsartikel (refereegranskat)abstract
- Scaffolds made from poly(3-hydroxybutyrate) were prepared by thermally induced phase separation from solutions in dioxane at temperatures above (23 degrees C) or below the freezing point of the solvent. At 23 degrees C, gelation occured with nano-fibrous network formation. The scaffolds prepared at -12 degrees C and -25 degrees C exhibited a highly porous morphology, with pores in the range of 3-25 mu m, caused by freezing of dioxane. The macroporous scaffolds, prepared at -12 degrees C, were treated with lipase to generate functional groups to which gelatin and glucosamine, respectively, were chemically coupled. The modified scaffolds had lower molecular weight, higher water content, lower melting temperature, and enthalpy. Cultivation of human embryonic fibroblasts on the macroporous scaffolds confirmed that the cells proliferated and adhered to the materials.
|
|
| 8. |
- Hajizadeh, Solmaz, et al.
(författare)
-
Characterization of macroporous carbon-cryostructured particle gel, an adsorbent for small organic molecules
- 2010
-
Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 6:21, s. 5562-5569
-
Tidskriftsartikel (refereegranskat)abstract
- Preparation of a new type of cryostructured carbon particle macroporous gel with one-step sub-zero cross-linking was studied in this work. Aggregation of nano-and micro-particles of poly(N-isopropylacrylamide-co-allylamine) was used to form a polymeric network to integrate activated carbon particles. The cryostructured particle gel was compared with the conventional composite cryogel. The unique macroporous structure of the gel in combination with retained porosity of the carbon particles makes it suitable in separation and environmental applications. The adsorption isotherm of phenol was studied and the advantages of cryostructured particle gel over conventional composite structures were compared in this study. The developed new gels were characterized by scanning electron microscopy, mercury porosimetry and texture analysis.
|
|
| 9. |
- Hajizadeh, Solmaz, et al.
(författare)
-
Composite cryogel with immobilized concanavalin A for affinity chromatography of glycoproteins.
- 2012
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 35:21, s. 2978-2985
-
Tidskriftsartikel (refereegranskat)abstract
- Composite cryogels containing porous adsorbent particles were prepared under cryogelation conditions. The composites with immobilized concanavalin A (Con A) were used for capturing glycoproteins. Adsorbent particles were introduced into the structure in order to improve the capacity and to facilitate the handling of the particles. The monolithic composite cryogels were produced from suspensions of polyvinyl alcohol particles and porous adsorbent particles and cross-linked under acidic conditions at sub-zero temperature. The cryogels were epoxy activated and Con A was immobilized as an affinity ligand. Binding and elution of horseradish peroxidase (HRP) was studied in batch experiment and in a chromatographic setup. Increasing adsorbent concentration in composite cryogels will increase ligand density, which therefore enhances the amount of bound HRP from 0.98 till 2.9 (milligram enzyme per milliliter of gel) in the chromatographic system. The material was evaluated in 10 cycles for binding and elution of HRP.
|
|
| 10. |
- Hajizadeh, Solmaz, et al.
(författare)
-
Cryogelation of molecularly imprinted nanoparticles: A macroporous structure as affinity chromatography column for removal of β-blockers from complex samples.
- 2013
-
Ingår i: Journal of chromatography. A. - : Elsevier BV. - 1873-3778 .- 0021-9673. ; 1274, s. 6-12
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a new macroporous molecularly imprinted cryogel (MIP composite cryogel) was synthesized by glutaraldehyde cross-linking reaction of poly(vinyl alcohol) (PVA) particles and amino-modified molecularly imprinted core-shell nanoparticles. The MIP core-shell nanoparticles were prepared using propranolol as a template by one-pot precipitation polymerization with sequential monomer addition. The characteristics of the MIP composite cryogel were studied by scanning electron microscopy (SEM) and texture analyzer. The macroporous structure of the composite (with the pore size varying from a few micrometers to 100μm) enabled high mass transfer of particulate-containing fluids. In a solid phase extraction (SPE) process, the efficiency and selectivity of the MIP composite cryogel were investigated, where the cryogel was used as an affinity matrix to remove propranolol from aqueous solution as well as from complex plasma sample without prior protein precipitation. The MIP composite cryogel maintained high selectivity and stability and could be used repeatedly after regeneration.
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Hajizadeh, Solmaz, et al.
(författare)
-
Evaluation of selective composite cryogel for bromate removal from drinking water.
- 2010
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 33, s. 1752-1759
-
Tidskriftsartikel (refereegranskat)abstract
- Bromate, which is a potential carcinogen, should be removed from drinking water to levels of less than 10 mug/L. A chitosan-based molecularly imprinted polymer (MIP) and a sol-gel ion-exchange double hydrous oxide (Fe(2)O(3).Al(2)O(3).xH(2)O) adsorbent (inorganic adsorbent) were prepared for this purpose. The sorption behavior of each adsorbent including sorption kinetics, isotherms, effect of pH and selective sorption were investigated in detail. Sorption experimental results showed that the MIP adsorbents had better selectivity for bromate, even in the presence of high concentrations of nitrate, as compared to the inorganic adsorbent. It was found that pH does not affect the adsorption of bromate when using the inorganic adsorbent. Additionally, both adsorbents were immobilized in a polymeric cryogel inside plastic carriers to make them more practical for using in larger scale. Regeneration of the cryogels either containing MIP or inorganic adsorbents were carried out by 0.1 M NaOH and 0.1 M NaCl, respectively. It was found that the regenerated MIP and inorganic adsorbents could be used at least three and five times, respectively, without any loss in their sorption capacity.
|
|
| 15. |
- Hajizadeh, Solmaz, et al.
(författare)
-
Flow-Through-Mediated Surface Immobilization of Sub-Micrometre Particles in Monolithic Cryogels
- 2014
-
Ingår i: Macromolecular Materials and Engineering. - : Wiley. - 1438-7492. ; 299:5, s. 631-638
-
Tidskriftsartikel (refereegranskat)abstract
- Particles with functional groups on their surface were immobilized on premade cryogels through covalent bonding to maximize the accessibility of the target molecules to the surface of the particles. The physical properties of the composite cryogel were characterized by SEM, texture analysis and nitrogen adsorption. Different key factors affecting immobilization were also investigated, e.g., recirculation time and the number of functional groups on the premade cryogels. It was found that the physical characteristics of the composite cryogels prepared in this way were very similar to those of the primary matrices, while their binding capacity increased in comparison with conventionally prepared composite cryogels. The binding capacities of two different types of composite cryogel were evaluated by studying the adsorption of small molecules (copper ions and Orange G) and a large molecule (thermostable His-tagged exoglucanase).
|
|
| 16. |
|
|
| 17. |
- Inci, Ilyas, et al.
(författare)
-
Gelatin cryogels crosslinked with oxidized dextran and containing freshly formed hydroxyapatite as potential bone tissue-engineering scaffolds
- 2013
-
Ingår i: Journal of Tissue Engineering and Regenerative Medicine. - : Hindawi Limited. - 1932-6254. ; 7:7, s. 584-588
-
Tidskriftsartikel (refereegranskat)abstract
- Gelatin-based cryogels were prepared by using a novel crosslinker, oxidized dextran, which was synthesized and used in the study. The cryogels were also loaded with freshly formed hydroxyapatite (HA) particles. These cryogels are opaque, spongy and highly elastic and have a pore structure with large interconnected pores. They swell about 500% in aqueous media and within a few minutes reach their final swollen forms. The elastic moduli of HA-containing cryogels were 18.5 +/- 3.0 kPa, which is suitable for non-load-bearing bone tissue-engineering (TE) applications, especially for the craniofacial area. Copyright (c) 2012 John Wiley & Sons, Ltd.
|
|
| 18. |
- Inci, Ilyas, et al.
(författare)
-
Gelatin-Hydroxyapatite Cryogels with Bone Morphogenetic Protein-2 and Transforming Growth Factor Beta-1 for Calvarial Defects
- 2014
-
Ingår i: Journal of Biomaterials and Tissue Engineering. - : American Scientific Publishers. - 2157-9091 .- 2157-9083. ; 4:8, s. 624-631
-
Tidskriftsartikel (refereegranskat)abstract
- Over recent years, several tissue engineering techniques are used for bone regeneration. In this study gelatin-hydroxyapatite (Gelatin-HA) cryogel scaffolds were used with/without bone morphogenetic protein-2 (BMP-2) and transforming growth factor beta-1 (TGF-beta 1) to heal critical sized bone defects. Release of growth factors from the cryogels were performed up to 28 days in vitro. Moreover, in vivo study were performed by 6 groups and results were evaluated by micro computerized tomography (mu-CT) and histology on 2 months and 4 months after surgery. Gene expression studies were also performed on 2 weeks and 4 weeks after surgery. Collagen type I (Col I), alkaline phosphatase (ALP) and osteocalcin (OSC) gene expression levels were analyzed. According to histology and mu-CT results, there was a significant bone healing in the BMP-2 containing gelatin-HA cryogel group (Group I) as compared to other groups except autograft applied group (Group IV). Moreover, significant increases were observed for Col I, ALP and OSC in Group I and Group IV. However there was no significant increase in the group of BMP-2 and TGF-beta 1 applied together (Group II). The results reveal that combination of gelatin-HA cryogels with BMP-2 is a promising candidate for healing in critical sized craniofacial bone defects.
|
|
| 19. |
- Jespersen, Gry, et al.
(författare)
-
A thiol functionalized cryogel as a solid phase for selective reduction of a cysteine residue in a recombinant human growth hormone variant.
- 2014
-
Ingår i: Journal of Biotechnology. - : Elsevier BV. - 1873-4863 .- 0168-1656. ; 173, s. 76-85
-
Tidskriftsartikel (refereegranskat)abstract
- Site selective chemical modification is a preferred method, employed to prolong the circulation half-life of biopharmaceuticals. Cysteines have been used as attachment point for such modification, however, to be susceptible for chemical modification the involved thiol must be in its reduced form. Proteins often contain disulfides, which aid to maintain their tertiary structure and therefore must remain intact. Thus, methods for selectively reducing cysteine residues, introduced through site-directed mutagenesis, are of interest. In this study a macroporous, polymeric monolith was designed for selectively reducing a single cysteine residue inserted in recombinant human growth hormone (hGH). Advantages of such a material are the circumvention of the need to remove the reducing agent after reaction, as well as milder reduction conditions and a concomitant lower risk of reducing the native disulfides. The designed monolith showed very high capacity towards the selective reduction of an unpaired cysteine residue in a recombinant hGH variant. Factors influencing the selectivity and rate of reaction were investigated and it was found that monolith thiol loading, and buffer pH had an effect on the rate of reduction, whereas hGH variant concentration and buffer conductivity influenced both rate of reduction and selectivity. The developed system constitutes the basis for the development of a scalable platform for selective reduction of a capped cysteine residue in hGH.
|
|
| 20. |
- Jespersen, Gry, et al.
(författare)
-
Dual Application of Cryogel as Solid Support in Peptide Synthesis and Subsequent Protein-Capture
- 2013
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 130:6, s. 4383-4391
-
Tidskriftsartikel (refereegranskat)abstract
- The use of a cryogel in a combined application as a solid support for automated synthesis of a peptide ligand followed by affinity chromatography of a target protein is evaluated. The advantage, of synthesizing the ligand directly on the cryogel, is the circumvention of the standard process of synthesizing a peptide on a solid support, followed by cleavage, purification, analysis, and finally immobilization on the cryogel. To demonstrate the application, a peptide affinity ligand is synthesized directly on a cryogel with a yield of 28.4 mol g(-1) dry polymer and purity of 45% of crude product. The affinity capture of an antipeptide antibody reveals a specific binding capacity of 0.86 mg g(-1) dry polymer. To further elucidate the general availability of a peptide ligand to a macromolecular interaction, a trypsin substrate is synthesized on a cryogel. Trypsin cleavage of immobilized substrate is determined to 1.5 mol g(-1) dry polymer. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4383-4391, 2013
|
|
| 21. |
- Kirsebom, Harald, et al.
(författare)
-
Building Macroporous Materials from Microgels and Microbes via One-Step Cryogelation (dagger).
- 2009
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:15, s. 8462-8465
-
Tidskriftsartikel (refereegranskat)abstract
- Macroporous materials are prepared from microgels or microbes by one-step chemical cross-linking under semifrozen conditions. This avoids the use of freeze drying of the sample because a chemically stable structure is prepared under semifrozen conditions. Cryostructuration results in a material with pore walls composed of closely packed particles.
|
|
| 22. |
- Kirsebom, Harald, et al.
(författare)
-
Cryostructuration as a tool for preparing highly porous polymer materials
- 2011
-
Ingår i: Polymer Chemistry. - : Royal Society of Chemistry (RSC). - 1759-9954 .- 1759-9962. ; 2:5, s. 1059-1062
-
Forskningsöversikt (refereegranskat)abstract
- Cryostructuration is a technique which can be used to produce highly porous polymer materials from either monomeric or polymeric starting material. The technique utilizes freezing of dilute solutions or suspensions for the formation of porous materials. The process has been used in both aqueous and organic media for the preparation of porous materials. This mini-review highlights some recent trends for cryostructuration where it is based on a freeze/thawing approach.
|
|
| 23. |
- Kirsebom, Harald, et al.
(författare)
-
Enzyme-Catalyzed Crosslinking in a Partly Frozen State: A New Way to Produce Supermacroporous Protein Structures.
- 2013
-
Ingår i: Macromolecular Bioscience. - : Wiley. - 1616-5195 .- 1616-5187. ; 13:1, s. 67-76
-
Tidskriftsartikel (refereegranskat)abstract
- In this study a new way to produce supermacroporous protein structures was investigated. Enzyme-mediated crosslinking of gelatin or casein was performed in a partly frozen state, which yielded stable, protein-based cryogels. The reaction kinetics for the formation of cryogels were found to be fairly slow, most likely due to the low temperature (-12 °C) used or due to an increased viscosity owing to the cryo-concentration taking place. The produced cryogels were characterized with regards to their physical properties and in vitro degradation. Furthermore, cryogels produced from gelatin and casein were evaluated as potential scaffolds by fibroblast cultivation to confirm their in vitro biocompatibility. Gelatin- and casein-based scaffolds both supported cell proliferation and migration through the scaffold.
|
|
| 24. |
- Kirsebom, Harald, et al.
(författare)
-
In situ H-1 NMR studies of free radical cryopolymerization
- 2008
-
Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 49:18, s. 3855-3858
-
Tidskriftsartikel (refereegranskat)abstract
- Free radical polymerization of DMAAm (dimethylacrylamide)-co-PEG diacrylate in a semi-frozen aqueous solution was studied using H-1 NMR, which enables to monitor the non-frozen water as well as the reaction of monomers over time. It was possible to confirm the presence of a heterogeneous system with a liquid phase where the monomers were concentrated and the reaction proceeded. The resulting macroporous polymeric structure with dense pore walls was confirmed using scanning electron microscopy (SEM). (C) 2008 Elsevier Ltd. All rights reserved.
|
|
| 25. |
- Kirsebom, Harald, et al.
(författare)
-
Mechanism of Cryopolymerization: Diffusion-Controlled Polymerization in a Nonfrozen Microphase. An NMR Study
- 2009
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 42:14, s. 5208-5214
-
Tidskriftsartikel (refereegranskat)abstract
- Polymerization of dimethylacrylamide (DMAAm) cross-linked with PEG diacrylate was studied using H-1 NMR both in situ in a semi frozen system and in a supercooled aqueous system. The amount of nonfrozen microphase, in which polymerization proceeds, is defined by the concentration of the starting monomers and the freezing temperature, which depends on the depression in freezing temperature caused by dissolved osmolytes. However, despite there being identical initial concentrations in the nonfrozen microphase, at a chosen temperature of -10 degrees C the cryopolymerization proceeded at different rates depending on the size of the nonfrozen microphase. Further studies of the conditions in the nonfrozen microphase were performed by using pulsed gradient spin echo (PGSE) to study the self-diffusion of solutes. Observations regarding the reaction rate were rationalized in terms of different degrees of long-range diffusion which was seen using PGSE. Cryopolymerization resulted in decreasing osmolyte concentration, and hence in gradual freezing of excess water as defined by the depression in freezing point caused by the remaining monomers. The NMR data provide a way of rationale predicting the effect of the monomer concentrations and freezing temperatures on the amount of nonfrozen microphase and its polymer concentration. These parameters define cryogel properties such as mechanical strength and porosity, which are evaluated using SEM and as flow resistance of cryogels.
|
|
| 26. |
- Kirsebom, Harald, et al.
(författare)
-
Modulating the Porosity of Cryogels by Influencing the Nonfrozen Liquid Phase through the Addition of Inert Solutes.
- 2010
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:20, s. 16129-16133
-
Tidskriftsartikel (refereegranskat)abstract
- The freezing of monomeric mixtures is known to concentrate solutes in a nonfrozen phase in the area surrounding the ice crystals. The concentration of such solutes is determined by the freezing temperature. Although salts or solvents do not directly react in the polymerization reaction, they do change the composition and properties of the nonfrozen phase. In this study, we investigated the influence of the addition of various salts and solvents on the structure of macroporous hydrogels formed in a semifrozen state through aqueous free-radical polymerization. The change in composition of the nonfrozen phase was studied using NMR to monitor the freezing of water, and the structural changes of the gels were observed using scanning electron microscopy. It was found that the addition of methanol or acetone caused the formation of reaction-induced phase separation polymerization due to cryoconcentration, which caused a significant increase of methanol or acetone in the nonfrozen phase. This resulted in a material with bimodal pore size distribution with pores of 10-80 μm in diameter caused by cryogelation, and with pores in the polymeric matrix with a diameter of less than 1 μm due to the reaction-induced phase separation. Addition of salts to the monomeric mixture resulted in a structure with only pores of 10-80 μm in diameter due to cryogelation. Increasing the amount of salts added resulted in the formation of thicker pore walls and thus a slight reduction in pore size compared to a sample with no added solute. The possibility of changing the structure and properties of the gels by adding different solutes could open up new applications for these materials, for example, chromatography applications.
|
|
| 27. |
- Kirsebom, Harald
(författare)
-
Preparation and Characterization of Macroporous Cryostructured Materials
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Macroporous hydrogels are regarded as interesting materials both within biotechnology and biomedicine due to their properties. These materials can be prepared from a wide range of synthetic or naturally occurring compounds using a number of different techniques for their production. For this thesis, cryostructuring was used to prepare macroporous hydrogels, often named cryogels. The work utilized the fact that freezing an aqueous solution or suspension results in the formation of ice crystals. As these crystals grow any solutes or particles are expelled and accumulate in a liquid non-frozen phase around the ice crystals. Gel formation takes place in this non-frozen phase resulting in a crosslinked gel-network. The properties of this non-frozen phase are determined by the freezing conditions and the composition of the sample that was frozen. The ice crystals that form act as pore-forming agents and when the sample melts after gelation a macroporous material is formed with the pores being a replica of the ice crystals. Nuclear magnetic resonance (NMR) was utilized in this thesis to study the formation of cryogels produced by free radical polymerization of aqueous solutions of monomers. This technique allowed in situ studies of both the freezing process and the polymerization reaction. It could be seen from these studies that the starting concentration of monomers influenced the size of the non-frozen phase and that the properties of this phase influenced the reaction conditions. Furthermore, studying these reactions at -10 °C made it possible to investigate the differences between polymerization in a semi-frozen state and at supercooled conditions. Polymerization of a supercooled sample generated a non-porous material similar to materials formed above the freezing point, whereas in the semifrozen sample a macroporous structure was produced. It was shown that the structure of cryogels produced from monomeric precursors could be modulated by adding different inert solutes to the monomeric mixture. Adding salts resulted in materials with thicker pore walls and smaller pores sizes since the added solutes created a larger non-frozen phase. The addition of solvents which were poor solvents for the forming polymer resulted in cryogels with a bimodal pore size distribution. Macropores were formed due to the cryogelation process while a secondary porosity within the pore walls formed due to a polymerization-induced phase separation caused by the presence of the solvent. Using the principal that growing ice crystals expel compounds, a method for producing cryostructured materials from suspensions was described. Suspensions of synthetic particles or microorganisms were frozen and the material became closely packed between the ice crystals. In this state inter-particle covalent bonds were formed which prevented the structure from disintegrating into individual particles when the sample was thawed. The covalent bonds could be formed either through the addition of a crosslinker or through the reactions of functional groups on the surfaces of the particles. Structuring particles using this approach made it possible to incorporate activated carbon particles into the structure without blocking the internal porosity of the carbon. When a composite cryogel based on monomers was used to immobilize the carbon, blockage of the internal porosity of the carbon was observed. An evaluation of these new structures for biotechnological and biomedical applications would be interesting.
|
|
| 28. |
- Kirsebom, Harald, et al.
(författare)
-
Stimuli-Responsive Polymers in the 21st Century: Elaborated Architecture to Achieve High Sensitivity, Fast Response, and Robust Behavior
- 2011
-
Ingår i: Journal of Polymer Science. Part B, Polymer Physics. - : Wiley. - 0887-6266. ; 49:3, s. 173-178
-
Tidskriftsartikel (refereegranskat)abstract
- Life is polymeric in its essence. The living cell contains a range of biopolymers such as proteins, carbohydrates, and nucleic acids. The cells are often compartmentalized via membranes that are composed of lipids. These are small molecules, but they spontaneously aggregate into supermolecular structures. The building blocks of these lipids are among others fatty acids, structures built from methylene oligomers. Biopolymers are sensitive to external stimuli. There are examples where the molecules show a highly non-linear response to external stimuli. This is seen as moderate changes in structural properties in response to changes in an external parameter until a critical point is reached where a dramatic change in molecular properties takes place upon an incremental change in the external conditions. After the transition, the system responds poorly to further changes. Such non-linear responses contribute to dramatic cooperative conformational changes leading to strong effects in the biological system. The strong response is an integrated effect of many weak interactions, and it is the cooperativity between all these interactions that are the driving forces for processes occurring in such systems. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 173-178, 2011
|
|
| 29. |
- Kirsebom, Harald, et al.
(författare)
-
Ultrafast Responsive Poly(N-isopropylacrylamide) Gel Produced by Cryostructuring of Self-crosslinkable Polymer Microgels
- 2010
-
Ingår i: Macromolecular Rapid Communications. - : Wiley. - 1022-1336. ; 31:12, s. 1095-1100
-
Tidskriftsartikel (refereegranskat)abstract
- A macroporous material composed of closely aggregated particles was prepared by cryostructuration of N-isopropylacrylamide-co-N-hydroxymethylacrylamide (NIPA-co-HMAm) particle suspensions. The formed structure was maintained by the formation of covalent bonds through self-crosslinking between the particles while the system was in a semi-frozen state thus avoiding the need to freeze-dry the sample. This resulted in macroporous structure composed of closely aggregated thermoresponsive particles which exhibit an ultrafast temperature response. The response rate can be attributed both to the macroporous structure as well as the fast responsive properties of the individual particles.
|
|
| 30. |
- Kumar, Sudesh, et al.
(författare)
-
Reversible in situ precipitation: a flow-through approach for coating macroporous supports with metal hydroxides
- 2014
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488. ; 2:4, s. 1076-1084
-
Tidskriftsartikel (refereegranskat)abstract
- In this study we report on the production of metal-hydroxide-coated macroporous polymers (MHCMPs), which mainly involves a polyacrylamide backbone coated with iron-aluminium double hydroxides. The coating process is fast, occurs using relatively mild reagents at room temperature, and can be repeated multiple times, thus making it a very simple and flexible process. Electron microscopy and energy dispersive X-ray spectroscopy studies showed that metal hydroxide coating occurred throughout the polymer backbone. It was shown that the mass of metal hydroxides incorporated in the MHCMPs could be adjusted by varying the initial salt solution concentration or the number of cycles in the process. Under the studied conditions, on a polymer backbone of mass 25 mg, we observed a maximum metal hydroxide mass incorporation of 18 mg for the MHCMPs produced at 6 cycles by using 0.4 M iron and aluminium salt solution. Nitrogen adsorption isotherms indicated that the surface area of the MHCMPs increased linearly with the increase in the mass of metal hydroxides incorporated. The polymer backbone with no mass incorporated showed a BET surface area of 18 m(2) g(-1) and the MHCMPs with maximum mass incorporation under the studied conditions showed a BET surface area of 63 m(2) g(-1). MHCMPs with varying mass incorporations were applied for arsenic (As(III)) adsorption and showed a high As(III) removal, indicating that they can serve as potential adsorbents. In addition, MHCMPs incorporated with other metal hydroxides were also produced and characterized to show that this method is applicable for coating these as well.
|
|
| 31. |
- Plieva, Fatima, et al.
(författare)
-
Preparation of macroporous cryostructurated gel monoliths, their characterization and main applications.
- 2011
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 34, s. 2164-2172
-
Tidskriftsartikel (refereegranskat)abstract
- Cryostructuration platform renders it possible to form macroporous materials (known as cryogels) with a broad range of porosity, from structures with combination of meso- and macropores to structures with 100-μm sized macropores. When these materials are formed in the shape of monoliths (monolithic cryogels), they present a unique monolithic stationary medium for specific applications. This review summarizes the recent research on the preparation and characterization of cryostructurated monolithic cryogels for (bio)separation and points to some future perspectives.
|
|
| 32. |
- Suresh, Prashanth, et al.
(författare)
-
Arsenite adsorption on cryogels embedded with iron-aluminium double hydrous oxides: Possible polishing step for smelting wastewater?
- 2013
-
Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 1873-3336 .- 0304-3894. ; 250, s. 469-476
-
Tidskriftsartikel (refereegranskat)abstract
- Arsenic is among the most toxic elements and it commonly exists in water as arsenite (As(III)) and arsenate (As(V)) ions. As(III) removal often requires a pre-oxidation or pH adjustment step and it is a challenge to adsorb As(III) at circumneutral pH. In this study, iron-aluminium double hydrous oxides were synthesized and incorporated into cryogels. The resulting composite cryogels were evaluated for As(III) adsorption. Initial experiments indicated that the adsorbent showed similar adsorption kinetics for both As(V) and As(III) ions. The adsorption of As(III) best fit the Langmuir isotherm and the maximum adsorption capacity was 24.6mg/g. Kinetic modeling indicated that the mechanism of adsorption was chemisorption, making the adsorbent-adsorbate interactions independent of charge and hence allowing the adsorbent to function equally efficient across pH 4-11. A Swedish smelting wastewater was used to evaluate the adsorption performance in continuous mode. The studies showed that the adsorbent was successful in reducing the arsenic concentrations below the European Union emission limit (0.15mg/l) in a smelting wastewater collected after two precipitation processes. The arsenic removal was obtained without requiring a pH adjustment or a pre-oxidation step, making it a potential choice as an adsorbent for As(III) removal from industrial wastewaters.
|
|
| 33. |
- Syverud, Kristin, et al.
(författare)
-
Cross-linking cellulose nanofibrils for potential elastic cryo-structured gels
- 2011
-
Ingår i: Nanoscale Research Letters. - 1931-7573 .- 1556-276X. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibrils were produced from P. radiata kraft pulp fibers. The nanofibrillation was facilitated by applying 2,2,6,6-tetramethylpiperidinyl-1-oxyl-mediated oxidation as pretreatment. The oxidized nanofibrils were cross-linked with polyethyleneimine and poly N-isopropylacrylamide-co-allylamine-co-methylenebisacrylamide particles and were frozen to form cryo-structured gels. Samples of the gels were critical-point dried, and the corresponding structures were assessed with scanning electron microscopy. It appears that the aldehyde groups in the oxidized nanofibrils are suitable reaction sites for cross-linking. The cryo-structured materials were spongy, elastic, and thus capable of regaining their shape after a given pressure was released, indicating a successful cross-linking. These novel types of gels are considered potential candidates in biomedical and biotechnological applications.
|
|
| 34. |
- Ye, Jialei, et al.
(författare)
-
Poly(hydroxyethyl methacrylate)-based composite cryogel with embedded macroporous cellulose beads for the separation of human serum immunoglobulin and albumin
- 2013
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 36:24, s. 3813-3820
-
Tidskriftsartikel (refereegranskat)abstract
- A novel super-macroporous monolithic composite cryogel was prepared by embedding macroporous cellulose beads into poly(hydroxyethyl methacrylate) cryogel. The cellulose beads were fabricated by using a microchannel liquid-flow focusing and cryopolymerization method, while the composite cryogel was prepared by cryogenic radical polymerization of the hydroxyethyl methacrylate monomer with poly(ethylene glycol) diacrylate as cross-linker together with the cellulose beads. After graft polymerization with (vinylbenzyl)trimethylammonium chloride, the composite cryogel was applied to separate immunoglobulin-G and albumin from human serum. Immunoglobulin-G with a mean purity of 83.2% and albumin with a purity of 98% were obtained, indicating the composite cryogel as a promising chromatographic medium in bioseparation for the isolation of important bioactive proteins like immunoglobulins and albumins.
|
|
| 35. |
- Yun, Junxian, et al.
(författare)
-
An improved capillary model for describing the microstructure characteristics, fluid hydrodynamics and breakthrough performance of proteins in cryogel beds.
- 2011
-
Ingår i: Journal of chromatography. A. - : Elsevier BV. - 1873-3778 .- 0021-9673. ; 1218:32, s. 5487-5497
-
Tidskriftsartikel (refereegranskat)abstract
- A capillary-based model modified for characterization of monolithic cryogels is presented with key parameters like the pore size distribution, the tortuosity and the skeleton thickness employed for describing the porous structure characteristics of a cryogel matrix. Laminar flow, liquid dispersion and mass transfer in each capillary are considered and the model is solved numerically by the finite difference method. As examples, two poly(hydroxyethyl methacrylate) (pHEMA) based cryogel beds have been prepared by radical cryo-copolymerization of monomers and used to test the model. The axial dispersion behaviors, the pressure drop vs. flow rate performance as well as the non-adsorption breakthrough curves of different proteins, i.e., lysozyme, bovine serum albumin (BSA) and concanavalin A (Con A), at various flow velocities in the cryogel beds are measured experimentally. The lumped parameters in the model are determined by matching the model prediction with the experimental data. The results showed that for a given cryogel column, by using the model based on the physical properties of the cryogel (i.e., diameter, length, porosity, and permeability) together with the protein breakthrough curves one can obtain a reasonable estimate and detailed characterization of the porous structure properties of cryogel matrix, particularly regarding the number of capillaries, the capillary tortuousness, the pore size distribution and the skeleton thickness. The model is also effective with regards to predicting the flow performance and the non-adsorption breakthrough profiles of proteins at different flow velocities. It is thus expected to be applicable for characterizing the properties of cryogels and predicting the chromatographic performance under a given set of operating conditions.
|
|
| 36. |
- Yun, Junxian, et al.
(författare)
-
Chromatographic adsorption of serum albumin and antibody proteins in cryogels with benzyl-quaternary amine ligands.
- 2015
-
Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1381, s. 173-183
-
Tidskriftsartikel (refereegranskat)abstract
- The preparation and characterization of mixed-mode adsorbents for a typical separation purpose are of great importance in bioseparation areas. In this work, we prepared a new monolithic cryogel with a combination of ion-exchange and hydrophobic functions by employing benzyl-quaternary amine groups. The fundamental cryogel properties, protein equilibrium adsorption isotherm and chromatographic adsorption in the cryogel were measured experimentally. The results showed that, by using bovine serum album as the model protein, the dual functional cryogel has protein binding capability even in salt solution and the buffer with pH close or below the protein isoelectric point due to both the electrostatic and hydrophobic interactions. A capillary-based adsorption model was developed, which provided satisfied insights of the microstructure, axial dispersion, mass transfer as well as protein adsorption characteristics within the cryogel bed. The chromatographic isolation of bioactive proteins from rabbit blood serum was carried out by the cryogel. Immunoglobulin G antibody with a purity of 98.2% and albumin with a purity of 96.8% were obtained, indicating that the cryogel could be an interesting and promising adsorbent in bioseparation areas.
|
|
| 37. |
- Yun, Junxian, et al.
(författare)
-
Modeling of protein breakthrough performance in cryogel columns by taking into account the overall axial dispersion.
- 2009
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 32:15-16, s. 2601-2607
-
Tidskriftsartikel (refereegranskat)abstract
- A model considering the overall axial dispersion for describing protein adsorption and breakthrough in monolithic cryogel beds has been developed. The microstructure of cryogels was characterized by tortuous capillaries with a normal diameter distribution but a constant pore wall thickness. The axial dispersion within cryogel columns was described by using the overall axial dispersion coefficient, which can be easily obtained by matching the experimental breakthrough curves without adsorption or measuring residence time distributions (RTDs). Experimental breakthrough curves of lysozyme within a metal-chelated affinity cryogel by Persson et al. (Biotechnol. Bioeng. 2004, 88, 224-236) and a cation-exchange cryogel by Yao et al. (J. Chromatogr. A 2007, 1157, 246-251) were employed as examples to test the model. The results showed that by using the axial dispersion coefficient and assuming uniform radial concentration profile at a given cross-section of the cryogel along the bed height, the model can describe the detailed behaviors of the in-bed overall axial dispersion, the in-pore mass transfer, as well as the protein adsorption and breakthrough. For a known overall axial dispersion coefficient, the lumped parameter of the mass transfer coefficient between the bulk liquid and the capillary wall can be determined by fitting the protein breakthrough curve at a known chromatographic condition. Once this parameter is determined, the model can be used to predict the protein breakthrough profiles under different conditions based on the basic physical parameters of the cryogel bed and the properties of the fluid and protein. The effective capillary diameters employed in the model are close to the actual pore sizes observed from the images by SEM. The model predictions of lysozyme breakthrough profiles at various flow rates are also in good agreement with the experimental data in both the metal-chelated affinity and cation-exchange cryogel columns.
|
|
| 38. |
- Zaushitsyna, Oksana, et al.
(författare)
-
Cryostructured and Crosslinked Viable Cells Forming Monoliths Suitable for Bioreactor Applications
- 2014
-
Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 57:5, s. 339-348
-
Tidskriftsartikel (refereegranskat)abstract
- Applications of immobilized biocatalysts in both research and industry require highly active catalysts, preferably at a low cost. In this study, cryogels with high catalyst density were produced through cryostructuration of whole Escherichia coli (E.coli) cells. Prepared cryogels are macroporous materials composed of metabolically active cells crosslinked to each other via polymeric structures. Different macromolecular reagents: oxidized dextran (OxDex), polyvinyl alcohol (PVA) and polyethyleneimine (PEI), the two latter activated with glutaraldehyde (GTA) have been synthesized. Prepared polymers were tested as effective and mild crosslinkers for cells during the cryostructuration procedure. Combination of the two synthetic polymers: PEI+GTA and PVA+GTA was found most suitable for formation of macroporous and stable structures from cells without any toxic effect on them. About 90 % of beta-glucosidase activity in cells was retained after cross-linking with a combination of synthetic polymers, whereas E. coli crosslinked using GTA showed complete loss of activity. Preserved viability of cells in cryogel offers possibility to induce protein expression in cells after crosslinking. For beta-glucosidase induction post immobilization yielded 50 % activity of that from cells induced in free form before cryo-structurization. The results of the post immobilization studies indicate an interesting potential for handling very sensitive enzymes.
|
|
| 39. |
- Zhang, Songhong, et al.
(författare)
-
Hydrophobic cryogels prepared via cryo-polymerization as oil carriers for biosynthesis of sophorolipids
- 2020
-
Ingår i: Biochemical Engineering Journal. - : Elsevier BV. - 1369-703X. ; 161
-
Tidskriftsartikel (refereegranskat)abstract
- Microbial synthesis of high-value biochemicals like biosurfactants using renewable substrates has attracted an intensive interest in the past decade. In this work, the bioproduction of sophorolipids was achieved by fermentation of different vegetable oils with the strain of Candida bombicola A0803 using novel hydrophobic poly(butyl methacrylate)(pBMA) cryogels as the oil substrate delivery carriers. The hydrophobic cryogels were prepared successfully via the cryo-polymerization of the reactive emulsion containing hydrophobic monomers under freezing conditions, and the characterization of cryogels was investigated experimentally. The results showed that the polymerization yields of 70 %–89 % were achieved and the cryogels had supermacropores with the maximum porosities of 92 %–96 % and good elasticity in organic solvents but rigid in water, which could provide preferable release properties for vegetable oils. Theie Young's elasticity modulus varied from 0.096 to 0.951 kPa in ethanol and acetone and the related aqueous solutions. With the pBMA cryogels as the delivery carriers of oil substrates, the maximum concentrations of sophorolipids produced for rapeseed, perilla seed and linseed oils were improved 14.5 %, 54.5 % and 53.7 %, while the maximum productivities were improved 14.5 %, 72.1 % and 42.7 % compared with those under the same fermentation condition of free carriers after 204 h–252 h of cultivation, indicating that the hydrophobic cryogels could be an interesting material for the potential applications in biosynthesis areas.
|
|
| 40. |
- Önnby, Linda, et al.
(författare)
-
Cryogel-supported titanate nanotubes for waste treatment: Impact on methane production and bio-fertilizer quality.
- 2015
-
Ingår i: Journal of Biotechnology. - : Elsevier BV. - 1873-4863 .- 0168-1656. ; 207, s. 58-66
-
Tidskriftsartikel (refereegranskat)abstract
- By reducing the cadmium (Cd(2+)) content in biomass used for bio-based products such as biogas, a less toxic bio-based fertilizer can be obtained. In this work, we demonstrate how a macroporous polymer can support titanate nanotubes, and we take advantage of its known selective adsorption behavior towards Cd(2+) in an adsorption process from real nutrient-rich process water from hydrolysis of seaweed, a pollutant-rich biomass. We show that pretreatment steps involving alteration in area-to-volume ratio performed in aerated and acidic conditions release the most Cd(2+) from the solid material. By integrating an adsorption step between hydrolysis and the biomethane, we show that it was possible to obtain high Cd(2+) removal (ca. 94%) despite molar excess (between 100 and 500) of co-present ions (e.g., Mg(2+), Ca(2+), Na(+), K(+)) and with maintained total phosphorous content. The bio-methane potential did not significantly decrease as compared to a process without cadmium removal and the yielded bio-fertilizer followed Swedish guideline values. This study provides a sound and promising alternative for a novel remediation step, enabling higher use of otherwise tricky and to some extent overlooked biomass sources.
|
|
| 41. |
- Önnby, Linda, et al.
(författare)
-
Improved arsenic(III) adsorption by Al2O3 nanoparticles and H2O2: Evidence of oxidation to arsenic(V) from X-ray absorption spectroscopy.
- 2014
-
Ingår i: Chemosphere. - : Elsevier BV. - 1879-1298 .- 0045-6535. ; 113, s. 151-157
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the oxidation of inorganic As(III) with H2O2 catalysed by Al2O3, using X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy. The effects of different reaction conditions (pH, time and initial H2O2 concentration) were also studied as were the kinetics of the oxidation reaction. We demonstrated that As(III) was oxidized to As(V) in the presence of H2O2 and Al2O3. Furthermore, all arsenic species found on the Al2O3 surface were in the As(V) state. The presence of both Al2O3 and H2O2 was necessary for oxidation of As(III) to take place within the period of time studied. The oxidation kinetics indicate a mechanism where reversible As(III) binding to the alumina surface is followed by irreversible oxidation by H2O2 leading to strongly bound As(V). Results from this study indicate that there is a surface-catalysed oxidation of As(III) on Al2O3 by H2O2, a reaction that can take place in nature and can be of help in the development of novel treatment systems for As(III) removal.
|
|
| 42. |
- Önnby, Linda, et al.
(författare)
-
Polymer composite adsorbents using particles of molecularly imprinted polymers or aluminium oxide nanoparticles for treatment of arsenic contaminated waters.
- 2012
-
Ingår i: Water Research. - : Elsevier BV. - 1879-2448 .- 0043-1354. ; 46:13, s. 4111-4120
-
Tidskriftsartikel (refereegranskat)abstract
- Removal of As(V) by adsorption from water solutions was studied using three different synthetic adsorbents. The adsorbents, (a) aluminium nanoparticles (Alu-NPs, <50 nm) incorporated in amine rich cryogels (Alu-cryo), (b) molecular imprinted polymers (<38 μm) in polyacrylamide cryogels (MIP-cryo) and (c) thiol functionalised cryogels (SH-cryo) were evaluated regarding material characteristics and arsenic removal in batch test and continuous mode. Results revealed that a composite design with particles incorporated in cryogels was a successful means for applying small particles (nano- and micro- scale) in water solutions with maintained adsorption capacity and kinetics. Low capacity was obtained from SH-cryo and this adsorbent was hence excluded from the study. The adsorption capacities for the composites were 20.3 ± 0.8 mg/g adsorbent (Alu-cryo) and 7.9 ± 0.7 mg/g adsorbent (MIP-cryo) respectively. From SEM images it was seen that particles were homogeneously distributed in Alu-cryo and heterogeneously distributed in MIP-cryo. The particle incorporation increased the mechanical stability and the polymer backbones of pure polyacrylamide (MIP-cryo) were of better stability than the amine containing polymer backbone (Alu-cryo). Both composites worked well in the studied pH range of pH 2-8. Adsorption tested in real wastewater spiked with arsenic showed that co-ions (nitrate, sulphate and phosphate) affected arsenic removal for Alu-cryo more than for MIP-cryo. Both composites still adsorbed well in the presence of counter-ions (copper and zinc) present at low concentrations (μg/l). The unchanged and selective adsorption in realistic water observed for MIP-cryo was concluded to be due to a successful imprinting, here controlled using a non-imprinted polymer (NIP). A development of MIP-cryo is needed, considering its low adsorption capacity.
|
|
| 43. |
- Önnby, Linda, et al.
(författare)
-
γ-Al2O3-based nanocomposite adsorbents for arsenic(V) removal: Assessing performance, toxicity and particle leakage.
- 2014
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 1879-1026 .- 0048-9697. ; 473, s. 207-214
-
Tidskriftsartikel (refereegranskat)abstract
- The generation and development of effective adsorption materials for arsenic removal are urgently needed due to acute arsenic contamination of water sources in many regions around the world. In the search for these new adsorbents, the application of nanomaterials or nanocomposites, and especially the use of nanoparticles (NPs), has proven increasingly attractive. While the adsorptive performance of a range of nanocomposite and nanomaterial-based systems has been extensively reviewed in previously-published literature, the stability of these systems in terms of NP release, i.e. the ability of the nanomaterial or nanocomposite to retain incorporated NPs, is less well understood. Here we examine the performance of nanocomposites comprised of aluminium oxide nanoparticles (AluNPs) incorporated in macroporous polyacrylamide-based cryogels (n-Alu-cryo, where n indicates the percentage of AluNPs in the polymer material (n=0-6%, w/v)) for As(V) adsorption, and evaluate AluNP leakage before and after the use of these materials. A range of techniques is utilised and assessed (SEM, TEM, mass weight change, PIXE and in vitro toxicity studies). The 4-Alu-cryo nanocomposite was shown to be optimal for minimising AluNP losses while maximising As(V) removal. From the same nanocomposite we were further able to show that NP losses were not detectable at the AluNP concentrations used in the study. Toxicity tests revealed that no cytotoxic effects could be observed. The cryogel-AluNPs composites were not only effective in As(V) removal but also in immobilising the AluNPs. More challenging flow-through conditions for the evaluation of NP leakage could be included as a next step in a continued study assessing particle loss and subsequent toxicity.
|
|
