| 1. |
- Andac, M, et al.
(författare)
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Poly(hydroxyethyl methacrylate)-based macroporous hydrogels with disulfide cross-linker
- 2008
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1521-3935 .- 1022-1352. ; 209:6, s. 577-584
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Tidskriftsartikel (refereegranskat)abstract
- Biodegradable supermacroporous PHEMA cryogels were produced by combining two cross-linkers, poly(ethylene glycol) diacrylate and a newly developed disulfide water soluble crosslinker, N,N'-bis(methacryloyl)-L-cystine. The biodegradable PHEMA cryogels were prepared with gel fraction yields up to 70% and were characterized by highly interconnected pores of micrometer size and good mechanical stability. When subjected to reductive agents like DTT, the biodegradable PHEMA cryogels disintegrated into small pieces. The rate of disintegration was controlled by the crosslinking density in the cryogels and the DTT concentration.
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| 2. |
- Arvidsson, Pär, et al.
(författare)
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Chromatography of microbial cells using continuous supermacroporous affinity and ion-exchange columns
- 2002
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 977:1, s. 27-38
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Tidskriftsartikel (refereegranskat)abstract
- Continuous supermacroporous chromatographic columns with anion-exchange ligands [2-(dimethylanlino)ethyl group] and immobilized metal affinity (IMA) ligands (Cu2+-loaded iminodiacetic acid) have been developed allowing binding of Escherichia coli cells and the elution of bound cells with high recoveries. These poly(acrylamide)-based continuous supermacroporous columns have been produced by radical co-polymerization of monomers in aqueous solution frozen inside a column (cryo-polymerization). After thawing, the column contains a continuous matrix (so-called cryogel) with interconnected pores of 10-100 mum in size. The large pore size of the matrix makes it possible for E. coli cells to pass unhindered through a plain column containing no ligands. E. coli cells bound to an ion-exchange column at low ionic strength were eluted with 70-80% recovery at NaCl concentrations of 0.35-0.40 M, while cells bound to an IMA-column were eluted with around 80% recovery using either 10 mM imidazole or 20 mM EDTA solutions, respectively. The cells maintain their viability after the binding/elution procedure. These preliminary results indicate that microbial cells can be handled in a chromatographic mode using supermacroporous continuous columns. These columns are easy to manufacture from cheap and readily available starting materials, which make the columns suitable for single-time use. (C) 2002 Published by Elsevier Science B.V.
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| 3. |
- Boelgen, Nimet, et al.
(författare)
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Cryogelation for preparation of novel biodegradable tissue-engineering scaffolds
- 2007
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Ingår i: Journal of Biomaterials Science. Polymer Edition. - : Informa UK Limited. - 0920-5063 .- 1568-5624. ; 18:9, s. 1165-1179
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Tidskriftsartikel (refereegranskat)abstract
- 2-Hydroxyethyl methacrylate-L-lactate (HEMA-LLA) and HEMA-L-lactate-dextran (HEMA-LLA-D) were synthesized. H-1-NMR confirmed the formation of these oligomers and macromers. Cryogels with different pore structures were prepared using different amounts of HEMA, HEMA-LLA and HEMA-LLA-D by a cryogelation technique. SEM micrographs exhibited pore morphologies. Cryogels were highly porous with interconnected pore structures, opaque, spongy and highly elastic. It was possible to compress them to remove the water in the pores and to return to their original form just by immersing them in water in few minutes, which was quite reproducible. Their swelling abilities, compressive strengths and degradation in buffer solutions were found to be related with their structural properties which was controlled by changing the cryogelation recipe.
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| 4. |
- Bolgen, Nimet, et al.
(författare)
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Tissue responses to novel tissue engineering biodegradable cryogel scaffolds: An animal model
- 2009
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Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 91A:1, s. 60-68
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Tidskriftsartikel (refereegranskat)abstract
- Biodegradable macroporous cryogels with highly open and interconnected pore structures were produced from dextran modified with oligo L-lactide bearing hydroxyethylmethacrylate (HEMA) end groups in moderately frozen solutions. Tissue responses to these novel scaffolds were evaluated in rats after dorsal subcutaneous implantation, iliac submuscular implantation, auricular implantation, or in calvarial defect model. In no case, either necrosis or foreign body reaction was observed during histological studies. The cryogel scaffolds integrated with the surrounding tissue and the formation of a new tissue were accompanied with significant ingrowth of connective tissue cells and new blood vessels into the cryogel. The tissue responses were significantly lower in auricular and calvarial implantations when compared with the subcutanous and the submuscular implantations. The degradation of the scaffold was slower in bone comparing to soft tissues. The biodegradable cryogels are highly biocompatible and combine extraordinary properties including having soft and elastic nature, open porous structure, and very rapid and controllable swelling. Therefore, the cryogels could be promising candidates for further clinical applications in tissue regeneration. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 91 A: 60-68, 2009
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| 5. |
- Bradoo, Sapna, et al.
(författare)
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Synthesis of alkylgalactosides using whole cells of Bacillus pseudofirmus species as catalysts
- 2004
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 1873-4863 .- 0168-1656. ; 110:3, s. 273-285
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Tidskriftsartikel (refereegranskat)abstract
- Whole cells of alkaliphilic Bacillus pseudofirmus AR-199, induced for beta-galactosidase activity, were used for the synthesis of 1-hexyl-beta-D-galactoside and 1-octyl-beta-D-galactoside, respectively, by transglycosylation reaction between lactose and the corresponding alcohol acceptor. The product yield was strongly influenced by the initial water content in the reaction mixture. Water content of 10% (v/v) was optimal providing 3.6-36 mM hexyl galactoside from 10 to 150 mM lactose, and no secondary product hydrolysis. Product yield could be enhanced by supplementing the reaction mixture with more cells or partly replacing the product with fresh substrate, but was decreased with time to the initial equilibrium level. Cell permeabilisation or disruption resulted in increased reaction rate and higher product yield but was followed by product hydrolysis. Octyl galactoside synthesis using whole cells was optimal at water content of 2% (v/v) with a yield of 26%. The cells were immobilised in cryogels of polyvinyl alcohol for use in continuous process, where hexyl galactoside was produced with a constant yield of 50% from 50 mM lactose for at least a week. (C) 2004 Elsevier B.V. All rights reserved.
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| 6. |
- Dainiak, Maria, et al.
(författare)
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Cell chromatography: Separation of different microbial cells using IMAC supermacroporous monolithic columns
- 2005
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Ingår i: Biotechnology Progress. - : Wiley. - 1520-6033 .- 8756-7938. ; 21:2, s. 644-649
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Tidskriftsartikel (refereegranskat)abstract
- Supermacroporous monolithic columns with CU2+-IDA ligands have been successfully used for chromatographic separation of different types of microbial cells. The bed of monolithic matrix is formed by a cryogel of poly(acrylamide) cross-linked with methylenebis(acrylamide) and has a network of large (10- 100 mu m) interconnected pores allowing unhindered passage of whole cells through the plain cryogel column containing no ligands. Two model systems have been studied: the mixtures of wild-type Escherichia coli (w.t. E. coli) and recombinant E. coli cells displaying poly-His peptides (His-tagged E. coli) and of w.t. E. coli and Bacillus halodurans cells. Wild-type E. coli and His-tagged E. coli were quantitatively captured from the feedstock containing equal amounts of both cell types and recovered by selective elution with imidazole and EDTA, with yields of 80% and 77%, respectively. The peak obtained after EDTA elution was 8-fold enriched with His-tagged E. coli cells as compared with the peak from imidazole elution, which contained mainly weakly bound w.t. E. coli cells. Haloalkalophilic B. halodurans cells had low affinity to the CU2+-IDA cryogel column and could be efficiently separated from a mixture with w.t. E. coli cells, which were retained and recovered in high yields from the column with imidazole gradient. All the cells maintained their viability after the chromatographic procedure. The results show that chromatography on affinity supermacroporous monolithic columns is a promising approach to efficient separations of individual cell types.
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| 7. |
- Dainiak, Maria, et al.
(författare)
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Chromatography of living cells using supermacroporous hydrogels, cryogels
- 2007
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Ingår i: Advances in Biochemical Engineering, Biotechnology. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0724-6145. ; 106, s. 101-127
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Tidskriftsartikel (refereegranskat)abstract
- The preparative cell separation is an intrinsic requirement of various diagnostic, biotechnological and biomedical applications. Affinity chromatography is a promising technique for cell separation and is based on the interaction between a cell surface receptor and an immobilised ligand. Most of the currently available matrices have pore size smaller than the size of the cells and are not suitable for cell chromatography due to column clogging. Another problem encountered in chromatographic separation of cells is a difficulty to elute bound cells from affinity surfaces. Application of novel adsorbents, supermacroporous monolithic cryogels, allows overcoming these problems. Cryogels are characterised by highly interconnected large (10-100 mu m) pores, sponge-like morphology and high elasticity. They are easily derivatised with any ligand of choice. Convective migration can be used to transport the cells through the matrix. Target cells bind to affinity ligands, while other cells pass through the cryogel column non-retained and are removed during a washing step. Because of the spongy and elastic nature of the cryogel matrices, the cells are efficiently desorbed by mechanical compression of cryogels, which provides high cell viability and yields. The release of affinity bound cells by mechanical compression of a cryogel monolithic adsorbent is a unique and efficient way of cell detachment. This detachment strategy and the continuous macroporous structure make cryogels very attractive for application in cell separation chromatography.
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| 8. |
- Dainiak, Maria, et al.
(författare)
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Integrated isolation of antibody fragments from microbial cell culture fluids using supermacroporous cryogels
- 2004
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1045:1-2, s. 93-98
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Tidskriftsartikel (refereegranskat)abstract
- The present paper describes a chromatographic capture/purification step for the recovery of proteins directly from undiluted and unclarified cell culture broths using supermacroporous dimethylacrylamide (DMAA) cryogel. The interconnected character and the size (10-100 mum) of the pores of the adsorbent make it possible to process whole cell fermentation broths without blocking the column. Cu2+-iminodiacetic acid (IDA) DMAA cryogel has been used for the isolation and purification of excreted (His)(6)-tagged single chain (sc) Fv antibody fragments, (His)(6)-scFv, from E. coli cell culture. Bound protein was recovered with 0.2 M imidazole or with 20 mM EDTA and was practically cell-free. Chromatographic capture using Cu2+-IDA cryogel column was performed at flow rates of 300 and 600 cm/h, respectively and resulted in 84-96% recovery of (His)(6)-scFv fragments with a purification factor of 13-15. The DMAA cryogel adsorbent is mechanically stable, can withstand harsh cleaning-in-place procedure and is relatively inexpensive. Chromatographic isolation of proteins using cryogels allows efficient removal of cells and can be operated at a flow rate as high as 600 cm/h. This novel technique has proven to be a scalable process, does not require special equipment and can be a good alternative to expanded bed adsorption and other integrated isolation techniques. (C) 2004 Published by Elsevier B.V.
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| 9. |
- Deraz, Sahar, et al.
(författare)
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Capture of bacteriocins directly from non-clarified fermentation broth using macroporous monolithic cryogels with phenyl ligands
- 2007
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 40:4, s. 786-793
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Tidskriftsartikel (refereegranskat)abstract
- The bacteriocin, sakacin P was produced by the bacteriocin-producing strain Lactobacillus sakei CCUG 42687 at 20 degrees C without pH control. The bacteriocin was captured directly from the fermentation broth using macroporous octyl- and phenyl-monolith columns. The large size of the interconnected macropores (up to 100 mu m) in the macroporous monolith allowed for direct fermentation broth processing with no clarification needed. Screening for optimal bacteriocin binding demonstrated that at pH 6.2 about 80% of the bacteriocin activity could be recovered with a purification factor of 150-160 in the cell-free eluate. Capture of bacteriocins from the fermentation broth using macroporous monoliths in the 96-well plate format presents a promising approach for rapid analytical isolation of bacteriocins from numerous samples.
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| 10. |
- Efremenko, Elena N., et al.
(författare)
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Dried-Reswollen Immobilized Biocatalysts for Detoxification of Organophosphorous Compounds in the Flow Systems
- 2009
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Ingår i: Applied Biochemistry and Biotechnology. - : Springer Science and Business Media LLC. - 1559-0291 .- 0273-2289. ; 159:1, s. 251-260
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Tidskriftsartikel (refereegranskat)abstract
- New immobilized biocatalysts based on polypeptides containing N- or C-terminal polyhistidine sequences and possessing organophosphorus hydrolase activity were investigated for detoxification of organophosphorous neurotoxic compounds in the flow systems. The biocatalysts were revealed to have a high catalytic activity within wide pH and temperature ranges 7.5-12.5 A degrees C and 15-65 A degrees C, respectively. The immobilized biocatalysts can be dried and reswollen before use with 92-93% catalytic activity remaining after drying and rehydration procedures. The half-lives of the biocatalysts under wet and dry storage conditions were 420 and 540 days, respectively.
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