| 1. |
- Ivanov, Alexander, et al.
(författare)
-
Affinity adhesion of carbohydrate particles and yeast cells to boronate-containing polymer brushes grafted onto siliceous supports
- 2006
-
Ingår i: Chemistry: A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 12:27, s. 7204-7214
-
Tidskriftsartikel (refereegranskat)abstract
- Cross-linked agarose particles (Sepharose CL-6B) and baker's yeast cells were found to adhere to siliceous supports end-grafted with boronate-containing copolymers (BCCs) of N,N-dimethylacrylamide at pH >= 7.5, due to boronate interactions with surface carbohydrates of the particles and the cells. These interactions were registered both on macroscopic and on molecular levels: the BCCs spontaneously adsorbed on the agarose gel at pH >= 7.5, with adsorption increasing with pH. Agarose particles and yeast cells stained with Procion Red HE-3B formed stable, monolayer-like structures at pH 8.0, whereas at pH 7.0-7.8 the structures on the copolymer-grafted supports were less stable and more random. At pH 9.0, 50% saturation of the surface with adhering cells was attained in 2 min. Stained cells formed denser and more stable layers on the copolymer-grafted supports than they did on supports modified with self-assembled organosilane layers derivatized with low-molecular-weight boronate, presumably due to a higher reactivity of the grafted BCCs. Quantitative detachment of adhered particles and cells could be achieved by addition of 20 mm fructose - a strong competitor for binding to boronates - at pH 7.0-9.0. Regeneration of the grafted supports allowed several sequential adhesion and detachment cycles with stained yeast cells. Affinity adhesion of micron-sized carbohydrate particles to boronate-containing polymer brushes fixed on solid supports is discussed as a possible model system suggesting a new approach to isolation and separation of living cells.
|
|
| 2. |
- Ivanov, Alexander, et al.
(författare)
-
Boronate-containing polymer brushes: Characterization, interaction with saccharides and mammalian cancer cells.
- 2009
-
Ingår i: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 88:1, s. 213-225
-
Tidskriftsartikel (refereegranskat)abstract
- Boronate-containing polymer brushes were synthesized by free radical copolymerization of N,N-dimethylacrylamide (DMAA) and N-acryloyl-m-phenylboronic acid (NAAPBA) (9:1) on the surface of 3-mercaptopropyl-silylated glass plates and capillaries. The brushes were characterized with time-of-flight secondary ion mass-spectrometry (ToF SIMS), atomic force microscopy and contact angle measurements. Fructose caused a well-expressed drop spreading on the surface of copolymer-grafted glass, due to the strong interaction with the boronate groups. Sedimentation of murine hybridoma cells M2139 or human myeloid leukemia cells KG1 onto the DMAA-NAAPBA copolymer-grafted glass plates from 10 mM phosphate buffer solution (pH 8.0) resulted in the cell adhesion. The adhered M2139 and KG1 cells could be quantitatively detached from the grafted plates with 0.1M fructose, which competed with cell surface carbohydrates for binding to the boronates. Evaluation of the binding strength between M2139 cells and the copolymer brush was performed by exposure of the adhered cells to a shear stress. Detachment of a fraction of 18% of the adhered M2139 cells was obtained at a shear force of 1400-2800 pN/cell generated by the running phosphate buffer (pH 8.0), whereas the remaining adhered cells (70%) could be detached with 0.1M fructose dissolved in the same buffer. Possible applications of the boronate-containing polymer brushes to affinity cell separation can be based upon the facile recovery of the attached cells. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2008.
|
|
| 3. |
- Ivanov, Alexander, et al.
(författare)
-
Boronate-containing polymers form affinity complexes with mucin and enable tight and reversible occlusion of mucosal lumen by poly (vinyl alcohol) gel
- 2008
-
Ingår i: International Journal of Pharmaceutics. - : Elsevier BV. - 1873-3476 .- 0378-5173. ; 358:1-2, s. 36-43
-
Tidskriftsartikel (refereegranskat)abstract
- Copolymers of N-acryloyl-m-aminophenylboronic acid (NAAPBA) with N,N-dimethylarcrylamide (DMAA) formed insoluble interpolymer complexes with mucin from porcine stomach at pH 9.0. The complex formation based on boronate-sugar interactions took place between the similarly charged macromolecules and resulted in coacervate particles formation, which depended both on pH and ionic strength of the solution. the coacervation rate displayed a maximum at the intermediate DMAA_NAAPBA copolymer: mucin weight ratio, that is a pattern typical of interpolymer complex formation.
|
|
| 4. |
- Ivanov, Alexander, et al.
(författare)
-
Synthesis of boronate-contaming copolymers of N,N-dimethylacrylamide, their interaction with poly(vinyl alcohol) and rheological behaviour of the gels
- 2004
-
Ingår i: Polymer. - : Elsevier BV. - 0032-3861. ; 45:8, s. 2495-2505
-
Tidskriftsartikel (refereegranskat)abstract
- Cross-linking of polyvinylalcohol (PVA) by boronate-containing copolymer of N,N-dimethylacrylamide (DMAA, 1) was studied and compared to cross-linking of PVA by borate buffers in weakly alkaline solutions. The copolymer of M-w = 19,000 g mor(-1) containing 9 mol% N-acryloyl-m-aminophenylboronic acid (NAAPBA, 2) was prepared by free radical polymerization of the monomers, exhibiting copolymerization constants r(1) = 0.84 and r(2) = 2.2. Due to multipoint interaction of the copolymer with PVA via monodiols, the intermolecular cross-linking required for seven-fold and 10-fold lower boron concentrations as compared to borate buffers of pH 8.6 and 7.5, respectively. In theological measurements, PVA-copolymer gels exhibited storage moduli (G'(max) comparable to those of PVA-borate gels prepared at 7.5-fold higher boron concentration and the same pH 8.6, what testified to the similar concentration of cross-links in the gels. Therefore, DMAA-NAAPBA copolymer is a more effective cross-linker of PVA than borate. The PVA-copolymer gel exhibited much higher relaxation time (97 s) compared to PVA-borate gels (less than or equal to20 s) indicating a longer lifetime of junction zones. The 'shape stability, of the gel is suggested to originate in the structure of junctions, containing several boronate-diol complexes, between the macromolecules of PVA and the copolymer. (C) 2004 Elsevier Ltd. All rights reserved.
|
|
| 5. |
- Ivanov, Alexander, et al.
(författare)
-
Variations of wettability and protein adsorption on solid siliceous carriers grafted with poly(N-isopropylacrylamide)
- 2006
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 296:2, s. 538-544
-
Tidskriftsartikel (refereegranskat)abstract
- Poly(N-isopropylacrylamide), a thermally responsive polymer, was end-grafted to mercaptopropyl derivatives of silica gel, plane glass sheets and glass capillary tubing by free radical polymerization of the monomer in 1,4-dioxane at 100 degrees C. The polymer monolayer attached to the glass carriers provided them with thermally controlled wettability registered by two independent methods: direct measurements of the water contact angle and capillary rise. The water Contact angle changed from 54 +/- 3 degrees to 68 +/- 3 degrees in the temperature range from 20 to 50 degrees C. The polymer grafting to silica gel (pore diameter 100 A, particle size 5 pm) resulted in 15-30-fold reduction in protein adsorption on the carrier at 35 degrees C. Adsorption isotherms of myoglobin indicate completely different characters of the protein adsorption to silica gel and its polyNIPAM-grafted derivative. Cooling of the grafted carrier containing adsorbed myoglobin to 9 degrees C led to a partial release of the protein to the contacting solution, whereas heating of the system to 35 degrees C resulted in reversible binding of the protein. Adsorption of myoglobin on polyNIPAM-coated silica was ca. 2-fold higher at 35 than at 9 degrees C, most probably (c) 2005 Elsevier Inc. All rights reserved.
|
|
| 6. |
- Plieva, Fatima, et al.
(författare)
-
Macroporous elastic polyacrylamide gels prepared at subzero temperatures: control of porous structure
- 2006
-
Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501. ; 16:41, s. 4065-4073
-
Tidskriftsartikel (refereegranskat)abstract
- Macroporous polyacrylamide gels (MPAAGs) with unique elastic morphology and open porous structure are prepared at subzero temperatures. The porous structure of MPAAGs consisting of large, 1 - 100 mu m-sized interconnected pores, is controlled by the freezing temperature, the content of the initiator system ( ammonium persulfate and N,N,N',N'-tetramethyl-ethylenediamine) in the initial reaction mixture and the solvent used. The initiator content, through its effects on the kinetics of polymerization, is an efficient tool of control allowing for the preparation of well defined macroporous elastic structures with either open interconnected pores or closed pores. In the semi-frozen reaction mixture, the dissolved monomers and initiators are concentrated in the unfrozen liquid microphase where the polymerization reaction proceeds. The final freezing temperature, T-f ( defined as temperature fixed in a low temperature thermostat), as well as the solvent used affect the porous structure through their effect on the formation of the unfrozen liquid microphase.
|
|
| 7. |
- Plieva, Fatima, et al.
(författare)
-
Pore structure in supermacroporous polyacrylamide based cryogels
- 2005
-
Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 1:4, s. 303-309
-
Tidskriftsartikel (refereegranskat)abstract
- Pore size and thickness of pore walls in macroporous polyacrylamide gels, so-called cryogels (pAAm-cryogels), were controlled by varying the content of monomers in the initial reaction mixture and the cross-linker used. The thickness of pore walls in pAAm-cryogels increased with increasing concentration of monomers in the initial reaction mixture. Pore volume in the supermacroporous pAAm-cryogels was in the range of 70-93% and decreased with increasing concentration of monomers in the reaction feed. The porous structure of the pAAm-cryogels was visualized using environmental scanning electron microscopy (ESEM) that allowed monitoring of the dehydration process in pAAm-cryogels. The accessibility of ligands covalently coupled to the polymer backbone for low molecular weight target, Cu(II) ions, and high molecular weight target, the protein lysozyme, was assessed for pAAm-cryogels produced from feeds with different monomer concentration. The amount of bound Cu(II) ions increased linearly with increasing monomer concentration in the reaction feed, suggesting that all ligands are equally accessible for small targets. On the contrary, lysozyme binding demonstrated a clear maximum at monomer concentration about 18% suggesting that only ligrands present at the surface of pore walls are accessible for high molecular weight targets.
|
|
| 8. |
- Plieva, Fatima, et al.
(författare)
-
Pore structure of macroporous monolithic cryogels prepared from poly(vinyl alcohol)
- 2006
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 100:2, s. 1057-1066
-
Tidskriftsartikel (refereegranskat)abstract
- Macroporous monolithic cryogels made from poly(vinyl alcohol) (PVA) with degree of saponification 87.7% have been prepared using a crosslinking reaction with glutaralclehyde under acidic conditions at subzero ternperatures. The porous structure of the monolithic cryogels from PVA (cryoPVA), analyzed using optical microscopy, scarinina electron microscopy, and environmental scanning electron microscopy, revealed interconnected macropores up to 150 mu m in size with a noticeable microporosity of the gel walls. Differential scanning calorimetry measurement showed that more than 90% of the water in the cryoPVA monoliths was freezable water, while the amount of polymer bound water increased with increase in the polymer concentration in the cryoPVA sample. The swelling degree of cryoPVA depended on concentration of polymer in the initial reaction mixture and degree of crosslinking. The cryoPVA monoliths were elastic and spongy-like materials that can be dried, stored in dried state, and re-swelled when required. Derivatization of hydroxyl-groups of the cryoPVA monolith allowed incorporation of required functionality. (c) 2006 Wiley Periodicals, Inc.
|
|
| 9. |
- Kumar, Ashok, et al.
(författare)
-
Integrated bioprocess for the production and isolation of urokinase from animal cell culture using supermacroporous cryogel matrices
- 2006
-
Ingår i: Biotechnology and Bioengineering. - Hoboken, NJ : Wiley. - 1097-0290 .- 0006-3592. ; 93:4, s. 636-646
-
Tidskriftsartikel (refereegranskat)abstract
- An integrated cell cultivation and protein product separation process was developed using a new type of supermacroporous polyacrylamide gel, called cryogel (pAAm-cryogel) support matrix. Human fibrosarcoma HT1080 and human colon cancer HCT116 cell lines were used to secrete urokinase (an enzyme of immense therapeutic utility) into the culture medium. The secreted protein was isolated from the circulating medium using a chromatographic capture column. A pAAm cryogel support with covalently coupled gelatin (gelatin-pAAm cryogel) was used for the cultivation of anchorage dependent cells in the continuous cell culture mode in 5% carbon dioxide atmosphere. The cells were attached to the matrix within 4-6 h of inoculation and grew as a tissue sheet inside the cryogel matrix. Continuous urokinase secretion into the circulating medium was monitored as a parameter of growth and viability of cells inside the bioreactor. No morphological changes were observed in the cells eluted from the gelatin-cryogel support and re-cultured in T-flask. The gelatin-pAAm cryogel bioreactor was further connected to a pAAm cryogel column carrying Cu(II)-iminodiacetic acid (Cu(II)-IDA)-ligands (Cu(II)-IDA-pAAm cryogel), which had been optimized for the capture of urokinase from the conditioned medium of the cell lines. Thus an automated system was built, which integrated the features of a hollow fiber reactor with a chromatographic protein separation system. The urokinase was continuously captured by the Cu(II)-IDA-pAAm cryogel column and periodically recovered through elution cycles. The urokinase activity increased from 250 PU/mg in the culture fluid to 2,310 PU/mg after recovery from the capture column which gave about ninefold purification of the enzyme. Increased productivity was achieved by operating integrated bioreactor system continuously for 32 days under product inhibition free conditions during which no back-pressure or culture contamination was observed. A total 152,600 Plough units of urokinase activity was recovered from 500 mL culture medium using 38 capture columns over a period of 32 days. (c) 2006 Wiley Periodicals, Inc.
|
|
| 10. |
- Arvidsson, Pär, et al.
(författare)
-
Chromatography of microbial cells using continuous supermacroporous affinity and ion-exchange columns
- 2002
-
Ingår i: Journal of Chromatography A. - 0021-9673. ; 977:1, s. 27-38
-
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.
|
|
