| 1. |
- Schoug, Åsa, et al.
(författare)
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Freeze-drying of Lactobacillus coryniformis Si3--effects of sucrose concentration, cell density, and freezing rate on cell survival and thermophysical properties
- 2006
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Ingår i: Cryobiology. - Maryland Heights, USA : Elsevier BV. - 0011-2240 .- 1090-2392. ; 53:1, s. 119-127
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Tidskriftsartikel (refereegranskat)abstract
- Freeze-drying is commonly used to stabilize lactic acid bacteria. Many factors have been reported to influence freeze-drying survival, including bacterial species, cell density, lyoprotectant, freezing rate, and other process parameters. Lactobacillus coryniformis Si3 has broad antifungal activity and a potential use as a food and feed biopreservative. This strain is considered more stress sensitive, with a low freeze-drying survival, compared to other commercialized antifungal lactic acid bacterial strains. We used a response surface methodology to evaluate the effects of varying sucrose concentration, cell density and freezing rate on Lb. coryniformis Si3 freeze-drying survival. The water activity of the dry product, as well as selected thermophysical properties of importance for freeze-drying; degree of water crystallization and the glass transition temperature of the maximally freeze concentrated amorphous phase (Tg') were determined. The survival of Lb. coryniformis Si3 varied from less than 6% to over 70% between the different conditions. All the factors studied influenced freeze-drying survival and the most important factor for survival is the freezing rate, with an optimum at 2.8 degrees C/min. We found a co-dependency between freezing rate and formulation ingredients, indicating a complex system and the need to use statistical tools to detect important interactions. The degree of water crystallization decreased and the final water activity increased as a function of sucrose concentration. The degree of water crystallization and Tg' was not affected by the addition of 10(8)-10(10) CFU/mI. At 10(11) CFU/ml, these thermophysical values decreased possibly due to increased amounts of cell-associated unfrozen water.
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| 2. |
- Can, Quan, et al.
(författare)
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Carotenoids particle formation by supercritical fluid technologies
- 2009
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Ingår i: Chinese Journal of Chemical Engineering. - 1004-9541 .- 2210-321X. ; 17:2, s. 344-349
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Tidskriftsartikel (refereegranskat)abstract
- Based on the solubility in supercritical CO2, two strategies in which CO2 plays different roles are used to make quercetine and astaxanthin particles by supercritical fluid technologies. The experimental results showed that micronized quercetine particles with mean particle size of 1.0-1.5 μm can be made via solution enhanced dispersion by supercritical fluids (SEDS) process, in which CO2 worked as turbulent anti-solvent; while for astaxanthin, micronized particles with mean particle size of 0.3-0.8 μm were also made successfully by rapid expansion supercritical solution (RESS) process.
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| 3. |
- Toropainen, Tarja, et al.
(författare)
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Crystal structure changes of gamma-cyclodextrin after the SEDS process in supercritical carbon dioxide affect the dissolution rate of complexed budesonide
- 2007
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Ingår i: Pharmaceutical research. - : Springer Science and Business Media LLC. - 0724-8741 .- 1573-904X. ; 24:6, s. 1058-1066
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. The present study describes the crystal structure changes of γ-cyclodextrin (γ-CD) during the solution enhanced dispersion by supercritical fluids (SEDS) process and its effect on dissolution behaviour of complexed budesonide. Materials and Methods. γ-CD solution (10 mg/ml in 50% ethanol) was pumped together with supercritical carbon dioxide through a coaxial nozzle with or without a model drug, budesonide (3.3 mg/ml). The processing conditions were 100 b and 40, 60 or 80°C. γ-CD powders were characterised before and after vacuum-drying (2-3 days at RT) with XRPD, SEM and NMR. Budesonide/γ-CD complexation was confirmed with DSC and XRPD. The dissolution behaviour of complexed budesonide was determined in aqueous solution (1% γ-CD, 37°C, 100 rpm). Results. During the SEDS process (100 b, 40 and 60°C), γ-CD and budesonide/γ-CD complexes crystallized in a tetragonal channel-type form. The vacuum-drying transformed crystalline γ-CD into amorphous form while the complexes underwent a tetragonal-to-hexagonal phase transition. The increase in the processing temperature decreased the crystallinity of γ-CD. At 80°C, amorphous γ-CD was obtained while the complexes crystallized in a hexagonal channel-type form. The dissolution behaviour of budesonide/γ-CD complexes was dependent on their crystal structure: the tetragonal form dissolved faster than the hexagonal form. Conclusions. The crystal structure of γ-CD and subsequently, the dissolution rate of complexed budesonide, can be modified with the processing conditions.
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| 4. |
- Toropainen, Tarja, et al.
(författare)
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Preparation of budesonide/gamma-cyclodextrin complexes in supercritical fluids with a novel SEDS method
- 2006
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Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0022-3549 .- 1520-6017. ; 95:10, s. 2235-2245
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to investigate if solid drug/cyclodextrin complexes could be produced in a single-step process with a solution enhanced dispersion by supercritical fluids (SEDS) method. Budesonide and gamma-cyclodextrin (CD) solutions (50% or 99.5% ethanol) were pumped from the same (conventional method) or separate (modified method) containers together with supercritical carbon dioxide through a coaxial nozzle into a particle formation chamber. The pressure was maintained at 100, 150 or 200 bar with a temperature of 40, 60 or 80 degrees C. SEDS-processed powders were characterised with HPLC, DSC and XRPD for budesonide content, complexation and crystallinity. The budesonide dissolution rate was determined in 1% gamma-CD aqueous solution. Solid, white budesonide/gamma-CD complex particles were formed using the conventional and modified SEDS processes. The complexation efficiency was dependent on the processing conditions. For example, with the conventional method (100 bar, 60 C) the yield of the powder was 65 +/- 12% with 0.14 +/- 0.02 mg budesonide/mg powder, corresponding to 1:2 drug:CD molar ratio. The dissolution rate of this complexed budesonide (93 +/- 2% after 15 min) was markedly higher compared to unprocessed micronised budesonide (41 +/- 10%) and SEDS-processed budesonide without CD (61 +/- 3%). As a conclusion, SEDS is a novel method to produce solid drug/CD complexes in a single-step process.
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| 5. |
- Velaga, Sitaram, et al.
(författare)
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Supercritical fluids processing of recombinant human Growth Hormone
- 2005
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Ingår i: Drug Development and Industrial Pharmacy. - 0363-9045 .- 1520-5762. ; 31:2, s. 135-149
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to investigate the feasibility of precipitating recombinant human growth hormone (hGH) from aqueous solutions using conventional and modified techniques of solution-enhanced dispersion (SEDS) by supercritical fluids. The study investigated the effect on hGH stability of adding isopropanol either as a cosolvent with the original aqueous protein solution (conventional process) or to the supercritical carbon dioxide before mixing with the aqueous protein solution (modified process). The influence of the addition of sucrose (with or without isopropanol) on the precipitation behavior and stability of the protein was also studied. Experiments were performed under various processing conditions (pressure 100-200 bars and temperature 40-50 degrees C), and with various flow rates and solution compositions (CO2/isopropanol and protein solution). Bioanalytical characterization of the resulting powders involved spectrophotometry, sodium dodecyl sulfate-polycrylamide gel electrophoresis, reverse-phase high performance liquid chromatography (RP-HPLC), and size exclusion chromatography. Solid-state characterization was performed using differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and Karl Fischer techniques. Results showed that with both conventional and modified methods, under optimum processing conditions, the presence of sucrose in the solution decreased the destabilizing effects of the solvent and/or process on the structure of hGH. More hGH was dissolved from the precipitated powders containing sucrose than from those containing only isopropanol. Reverse-phase HPLC indicated that about 94% of the hGH was recovered in its native form. The proportion of dimers and oligomers was reduced in the presence of sucrose; about 92% of the soluble protein was present in monomer form under optimal conditions. The remaining undissolved protein was in monomeric form. The precipitated powders were amorphous, containing particulate aggregates in the size range 1-6 microm with 5-10% residual moisture content. In conclusion, hGH was successfully precipitated from aqueous solution using SEDS technology. The presence of sucrose in the protein solution promoted the precipitation of hGH and reduced aggregation and improved dissolution.
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