| 1. |
- Dainiak, Maria B, et al.
(författare)
-
Gelatin-fibrinogen cryogel dermal matrices for wound repair: Preparation, optimisation and in vitro study.
- 2010
-
Ingår i: Biomaterials. - : Elsevier BV. - 1878-5905 .- 0142-9612. ; 31, s. 67-76
-
Tidskriftsartikel (refereegranskat)abstract
- Macroporous sponge-like gelatin-fibrinogen (Gl-Fg) scaffolds cross-linked with different concentrations (0.05-0.5%) of glutaraldehyde (GA) were produced using cryogelation technology, which allows for the preparation of highly porous scaffolds without compromising their mechanical properties, and is a more cost-efficient process than freeze-drying. The produced Gl-Fg-GA(X) scaffolds had a uniform interconnected open porous structure with a porosity of up to 90-92% and a pore size distribution of 10-120mum. All of the obtained cryogels were elastic and mechanically stable, except for the Gl-Fg-GA(0.05) scaffolds. Swelling kinetics and degradation rate, but not the porous structure of the cryogels, were strongly dependent on the degree of cross-linking. A ten-fold increase in the degree of cross-linking resulted in an almost 80-fold decrease in the rate of degradation in a solution of protease. Cryogels were seeded with primary dermal fibroblasts and the densities observed on the surface, plus the expression levels of collagen types I and III observed 5 days post-seeding, were similar to those observed on a control dermal substitute material, Integra((R)). Fibroblast proliferation and migration within the scaffolds were relative to the GA content. Glucose consumption rate was 3-fold higher on Gl-Fg-GA(0.1) than on Gl-Fg-GA(0.5) cryogels 10 days post-seeding. An enhanced cell motility on cryogels with reducing GA crosslinking was obtained after long time culture. Particularly marked cell infiltration was seen in gels using 0.1% GA as a crosslinker. The scaffold started to disintegrate after 42 days of in vitro culturing. The described in vitro studies demonstrated good potential of Gl-Fg-GA(0.1) scaffolds as matrices for wound healing.
|
|
| 2. |
- Grey, Carl, et al.
(författare)
-
Process development of oxygen-demanding reactions utilizing a simple design with parallel glass tube reactors - Evaluated using Gluconobacter oxydans (DSM 24525)
- 2012
-
Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 30:5-6, s. 441-445
-
Tidskriftsartikel (refereegranskat)abstract
- To investigate the possibility of using simple glass tubes as reactors for oxygen-demanding reactions, a setup was assembled to study the initial rate of conversion of glycerol to dihydroxyacetone (DHA) using Gluconobacter oxydans. Several parallel 10 mL glass tubes were incubated in a temperature-controlled shaker. The concentration of DHA was determined using a fast spectrophotometric HPLC-based method that could process 3 samples/min. It was shown that the obtained results were reproducible and the reaction rates remained constant throughout the reaction. Further, the system reached a high volumetric activity of 15.48 g DHA L-1 h(-1) consuming 86 mmol L-1 h(-1) oxygen before the system became mass-transfer limited, indicating a high diffusion of oxygen. It was concluded that the reactor system is well suited for process development where the requirement for oxygen is high and that the assay developed can be used to determine the initial rate of DHA production.
|
|
| 3. |
- Li, YuCai, et al.
(författare)
-
Application of shielding boronate affinity chromatography in the study of the glycation pattern of haemoglobin
- 2002
-
Ingår i: Journal of Chromatography. B. - 1873-376X. ; 776:2, s. 149-160
-
Tidskriftsartikel (refereegranskat)abstract
- Human haemoglobin (Hb) may appear in a number of glycated species. The glycation pattern of Hb using shielding boronate affinity chromatography (SBAC) has been studied in the present work. SBAC is a novel separation technique, which eliminates nonspecific boronate-protein interactions by introducing a so-called shielding reagent [1,2]. Two samples from Bio-Rad (Lyphochek(R))-one from normal persons' blood with relatively low HbA(1c) level (HbL) and the other from diabetic patients' blood with an elevated HbA(1c) level (HbH)-were used for the investigation. Glycated Hb (GHb) was separated from nonglycated Hb species using Tris as the shielding reagent. Two eluted peaks, eluted peak 1 (E1) and eluted peak 2 (E2), were obtained using a linear gradient elution with Tris. Several bands were observed on isoelectric focusing gel, which showed the same migration positions as Hb adducts, such as HbA(o), which is major Hb component containing two alpha chains and two beta chains; HbA(1c) which is post-translational glycation on the N-terminus of the beta chains of HbA(o); Foetal Hb (HbF), consisting of two alpha chains and two gamma chains; and glutathione Hb (also called HbSSG), which is the result from thiol-disulphide interchain exchange during oxidation of the thiol groups of Hb. In both HbL and HbH samples, E2 exhibited slightly higher amounts of HbF than E1. Electrospray-ionisation mass spectrometry showed that: (1) HbL-E1 was glycated with single glucose on both alpha and beta chains while no observable glycated chains were present in HbL-E2; (2) both HbH-E1 and HbH-E2 were glycated with single glucoses on both alpha and beta chains, however, compared with HbH-E1, HbH-E2 showed a higher relative intensity of the glycated beta chain and lower relative intensity of the glycated alpha chain; and (3) the degree of glycation increased with increasing glycation level of the sample. The amount of HbA(1c) presented in the eluted peaks was further determined using enzymatic digestion of glycated Hb by endoproteinase Glu-C and the subsequent separation and analysis of the digested peptides by reversed-phase high-performance liquid chromatography and capillary electrophoresis. The values of HbA(1c)/HbA(o) of the eluted peaks, i.e. HbL-E1, HbL-E2, HbH-E1 and HbH-E2, were 0.27, 0.19, 0.50 and 0.43, respectively. In both HbL and HbH samples, E1 contained higher amounts of HbA(1c) than E2. This study demonstrates the structural heterogeneity of GHb as well as the possibility of using SBAC to detect glycated species of Hb.
|
|
| 4. |
- Lozinsky, Vladimir I, et al.
(författare)
-
Polymeric Cryogels as Promising Materials of Biotechnological Interest.
- 2003
-
Ingår i: Trends in Biotechnology. - : Elsevier BV. - 0167-7799. ; 21:10, s. 445-451
-
Forskningsöversikt (refereegranskat)abstract
- Cryogels are gel matrices that are formed in moderately frozen solutions of monomeric or polymeric precursors. Cryogels typically have interconnected macropores (or supermacropores), allowing unhindered diffusion of solutes of practically any size, as well as mass transport of nano- and even microparticles. The unique structure of cryogels, in combination with their osmotic, chemical and mechanical stability, makes them attractive matrices for chromatography of biological nanoparticles (plasmids, viruses, cell organelles) and even whole cells. Polymeric cryogels are efficient carriers for the immobilization of biomolecules and cells.
|
|
| 5. |
- Savina, Irina N., et al.
(författare)
-
Biomimetic Macroporous Hydrogels: Protein Ligand Distribution and Cell Response to the Ligand Architecture in the Scaffold
- 2009
-
Ingår i: Journal of Biomaterials Science. Polymer Edition. - 0920-5063. ; 20:12, s. 1781-1795
-
Tidskriftsartikel (refereegranskat)abstract
- Macroporous hydrogels (MHs), cryogels, are a new type of biomaterials for tissue engineering that can be produced from any natural or synthetic polymer that forms a gel. Synthetic MHs are rendered bioactive by surface or bulk modifications with extracellular matrix components. In this study, cell response to the architecture of protein ligands, bovine type-I collagen (CG) and human fibrinogen (Fg), immobilised using different methods on poly(2-hydroxyethyl methacrylate) (pHEMA) macroporous hydrogels (MHs) was analysed. Bulk modification was performed by cross-linking cryo-co-polymerisation of HEMA and poly(ethylene glycol) diacrylate (PEGA) in the presence of proteins (CG/ pHEMA and Fg/pHEMA MHs). The polymer surface was modified by covalent immobilisation of the proteins to the active epoxy (ep) groups present on pHEMA after hydrogel fabrication (CG-epHEMA and Fg-epHEMA MHs). The concentration of proteins in protein/pHEMA and protein-epHEMA MHs was 80-85 and 130-140 mu g/ml hydrogel, respectively. It was demonstrated by immunostaining and confocal laser scanning microscopy that bulk modification resulted in spreading of CG in the polymer matrix and spot-like distribution of Fg. On the contrary, surface modification resulted in spot-like distribution of CG and uniform spreading of Fg, which evenly coated the surface. Proliferation rate of fibroblasts was higher on MHs with even distribution of the ligands, i.e., on Fg-epHEMA and CG/ pHEMA. After 30 days of growth, fibroblasts formed several monolayers and deposited extracellular matrix filling the pores of these MHs. The best result in terms of cell proliferation was obtained on Fg-epHEMA. The ligands displayed on surface of these scaffolds were in native conformation, while in bulk-modified CG/ pHEMA MHs most of the proteins were buried inside the polymer matrix and were less accessible for interactions with specific antibodies and cells. The method used for MH modification with bioligands strongly affects spatial distribution, density and conformation of the ligand on the scaffold surface, which, in turn, influence cell-surface interactions. The optimal type of modification varies depending on intrinsic properties of proteins and MHs. (C) Koninklijke Brill NV, Leiden, 2009
|
|
