Freeze-dried suspensions

Israeli et al. [3.31] found, that trehalose is a very good stabilizer for E, even if the freeze dried suspension of E was stored at 21 °C and 60 % relative humidity, and/or was exposed to visible light. In 3 h, the survival rate decreased without trehalose to 0.01 % under the influence of light and air, with trehalose, 35 % survived. The optimum trehalose concentration was found to be 100 mM. This corresponded with the number of trehalose molecules necessary to replace the water molecules in the outer membrane of the phospholipid molecules. 

To increase the activity and capability of reproduction of Saccharomyces cerevisiae (SC) Kabatov et al. [3.32] proposed the addition of 10 % skimmed milk, which has been saturated with Ar or N2. The freezing down to -25 °C was done under pressure and continued down to -55 °C. The freeze dried suspension did not change its quality during storage at +4 °C. 

Imovax rabies vaccine (human diploid cell) powder for injection freeze-dried suspension of Wistar rabies virus strain PM-1503-3M grown in human diploid cell cultures (inactivated whole virus). 

Lyophilization. LyophiLization is essentially a drying technology. Some dmgs and biologicals are thermolabile and/or unstable in aqueous solution. Utilization of freeze drying permits the production of granules or powders that can be reconstituted by the addition of water, buffered solution, or mixed hydrophilic solvents just prior to use, eg, certain antibiotic suspensions. 

Presentation (e.g., free-flowing, freeze-dried powder or emu-sified suspension)... 

Xanthans from several different sources were used in this study Xanthan samples A, B and C were kindly provided as freeze dried powder of ultrasonic degraded xanthan by Dr. B. Tinland, CERMAV, Grenoble, France. The molecular weights of these samples were determined experimentally in dilute solution by Dr. B. Tinland. Xanthan D was kindly provided as pasteurized, ultrafiltrated fermentation broth by Dr. G. Chauveteau, Institut Francais du Petrole, France. Xanthan E was kindly provided as a freeze dried sample from Dr. I. W. Sutherland, Edinburgh, Scotland. Xanthan F was obtained as a commercial, powdered material (Kelzan, Kelco Inc., a Division of Merck, San Diego CA.). Xanthan G was obtained as a commercial concentrated suspension (Flocon 4800, Pfizer, New York, NY)... 

Mann and Mitchell [58] described a simple colorimetric method for estimation of (-D)-penicillamine in plasma. Blood containing 2-50 pg of penicillamine was mixed with 0.1 M EDTA solution in tromethamine buffer solution. 0.1 mL of this solution was adjusted to pH 7.4 and centrifuged. To a portion of the plasma was added 3 M HCL, the mixture was freeze-dried, and a suspension of the residue in ethanol was centrifuged. The supernatant liquid was mixed with tromethamine buffer solution (pH 8.2) and 10 mM 5,5 -dithiobis-(2-nitrobenzoic acid) in phosphate buffer solution (pH 7.0), the mixture was shaken with ethyl ether, and the absorbance of the separated aqueous layer was measured at 412 nm. The mean recovery was 60% (four determinations), and the calibration graph was linear for the cited range. 

Fig. 1.36.1. Electrical resistance (ER) as function of temperature during cooling and rewarming of a virus suspension. The suspension subcools from -10 °C to approx. -46 °C and freezes at -60 °C to -65 °C. During rewarming the resistance drops clearly at approx. -33 °C. This product should be freeze dried at rice = -40 °C or a little higher (Fig. 7 from [1.27]).

During the freeze drying tests the virus suspensions are either basic salt medium (BSM) or BSM plus calcium lactobionate (CL) plus serum albumin (SA) frozen at -76 °C and dried either at 0 °C or at -40 °C. The activity has been evaluated after 30 days storage at -4 °C or -65 °C. Rehydratation was done with distilled water at 0 °C. The results with the freeze dried viruses indicate ... 

Milnes and Mostaghaci [5.5] compared the consequences of different drying methods on the density, the sinter rate and micro structures of sublimated TiO-, suspensions. Evaporation of water in a micro-oven and by radiation heating leds to strongly bound agglomerates, while freeze drying resulted in softly bound secondary clusters. The freeze dried powder reached in 2 h of sintering 98 % of the theoretical density, while differently dried powders needed twice as much time and had a less fine microstructure. 

Freeze drying or lyophilization is a drying process, in which the solvent and/or the medium of suspension is crystallized at low temperatures and thereafter sublimated from the solid state directly into the vapor phase. 

Freeze drying is mostly done with water as solvent. Fig. 1.1 sows the phase diagram of water and the area in which this transfer from solid to vapor is possible. This step is difficult, even for pure water. If the product contains two or more components in true solutions or suspensions, the situation can become so complicated that simplified model substances have to be used. Such complex systems occur ubiquitously in biological substances. 

Suspensions were prepared in 500 mL polycarbonate bottles by ultrasonically dispersing freeze-dried goethite in dilute nitric... 

Negative atmospheric pressure chemical ionization (APC) low-energy collision activation mss spectrometry has also been employed for the characterization of flavonoids in extracts of fresh herbs. Besides the separation, quantitative determination and identification of flavonoids, the objective of the study was the comparison of the efficacy of the various detection systems in the analysis of flavonoids in herb extracts. Freeze-dried herbs (0.5g of chives, cress, dill, lovage, mint, oregano, parsley, rosemary, tarragon and thyme) were ground and extracted with 20 ml of 62.5 per cent aqueous methanol. After sedimentation the suspension was filtered and used for HPLC analyses. Separations were carried out in an... 

In insulin powder prepared by freeze drying, the reactions observed were deamidation at AsnA21 and dimer formation [137]. In contrast to suspensions, amorphous insulin in the powder form was more stable than crystalline insulin. In fact, the rate of degradation of crystalline insulin increased with increasing water content, whereas the rate of degradation of amorphous insulin was essentially independent of water content up to the maximum studied (ca. 15%). 

Synthetic hydroxyapatite prepared by mixing stoichiometric amounts of aqueous solutions of calcium nitrate and ammonium phosphate was used in this study. The pH of the boiling suspension was maintained at about 10 by flowing a mixture of NH and throughout the precipitation process. The precipitate was repeatedly washed until the conductivity of the supernatant liquid was observed to be constant. The washed sample was freeze-dried and analyzed. An elemental analysis of the batch preparation showed the Ca/P molar to be ratio 1.64, with the predominant impurity being 2... 

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