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PubMed1997

Dependence of the molecular mobility and protein stability of freeze-dried gamma-globulin formulations on the molecular weight of dextran.

PURPOSE: The effect of the molecular weight of dextran on the molecular mobility and protein stability of freeze-dried serum gamma-globulin (BGG) formulations was studied. The stabilizing effect of higher molecular weight dextran is discussed in relation to the molecular mobility of the formulations. METHODS: The molecular mobility of freeze-dried BGG formulations containing dextrans of various molecular weights was determined based on the free induction decay of dextran and water protons measured by proton NMR. The protein stability of the formulations was determined at temperatures ranging from 20 to 70 degrees C by size exclusion chromatography. RESULTS: Changes in the molecular mobility of freeze-dried formulations that occurred at temperatures below the glass transition temperature could be detected as the molecular mobility-changing temperature (Tmc), at which dextran protons started to exhibit a Lorentzian relaxation decay due to higher mobility in addition to a Gaussian relaxation decay. Tmc increased as the molecular weight of dextran increased. The proportion of dextran protons which exhibited the higher mobility relaxation process (Phm) at temperatures above Tmc decreased as the molecular weight of dextran increased. Protein stability was closely related to molecular mobility. The temperature dependence of the denaturation rate changed at around Tmc, and denaturation in the microscopically liquidized state decreased as Phm decreased with increasing molecular weight of dextran. CONCLUSIONS: The effect of the molecular weight of dextran on the protein stability of freeze-dried BGG formulations could be explained in terms of the parameters obtained by 1H-NMR such as Tmc and Phm. These parameters appear to be useful in preformulation and stability prediction of freeze-dried formulations.

Calorimetry, Differential Scanning↗
PubMed1998

Preparation and mechanical properties of dense polycrystalline hydroxyapatite through freeze-drying.

High purity hydroxyapatite (HAp) powders were synthesized through the wet-chemical method and subsequent freeze-drying or heat-drying, respectively. Dense polycrystalline HAp ceramics were obtained by sintering the powder compacts in air in the temperature range 1100-1350 degrees C. Results show that the freeze-drying method can produce highly homogeneous, fine-grained HAp powders. The relative density, Vickers hardness and flexural strength of the sintered freeze-dried HAp ceramics increased with the sintering temperature, reaching a maximum at around 1350 degrees C, and the highest values obtained were 99.0%, 820 and 110 MPa, respectively. All these mechanical properties of the freeze-dried HAp ceramics are much higher than those of the conventionally heat-dried HAp ceramics. The drying method can significantly influence the properties of the HAp powders as well as the HAp ceramics.

Journal Article↗
PubMed2006

Freeze-dried whole plasma: evaluating sucrose, trehalose, sorbitol, mannitol and glycine as stabilizers.

Several groups report stability results for freeze-dried whole plasma intended for use as a transfusion product [Hellstern P, Sachse H, Schwinn H, Oberfrank K. Manufacture and in vitro characterization of a solvent/detergent-treated human plasma. Vox Sang 1992;63:178-185; Trobisch H. Results of a quality-control study of lyophilized pooled plasmas which have been virally inactivated using a solvent detergent method (modified Horowitz procedure). Beitr Infusionsther 1991;28:92-109; Hugler P, Trobish H, Neuman H, Moller, Sirtl C, Derdak M, Laubenthal H. Quality control of three different conventional fresh-frozen plasma preparations and one new virus-inactivated lyophilized pooled plasma preparation. Klin Wochenschr 1991;69:157-161; Krutvacho T, Chuansumrit A, Isarangkura P, Pintadit P, Hathirat P, Chiewsilp P. Response of hemophilia with bleeding to fresh dry plasma. Southeast Asian J Trop Med Public Health 1993;24:169-173; Chuansumrit A, Krasaesub S, Angchaisuksiri P, Hathirat P, Isarangkura P. Survival analysis of patients with haemophilia at the International Haemophilia Training Centre, Bangkok, Thailand. Haemophilia 2004;10:542-549]. Plasma coagulation properties are substantially impaired in these freeze-dried plasmas, while pH levels are close to alkaline. In this work, plasma supplemented with 60mM sucrose, trehalose, mannitol, sorbitol or glycine was freeze-dried. The samples were subjected to forced degradation at 40 degrees C for 10 days in order to quickly evaluate the effectiveness of the different stabilizers. Initial PT, APTT and TT values were 14.4+/-0. 5s, 31.4+/-1.5s and 18.3+/-0.6s, respectively. At the end of the degradation period, PT, APTT and TT were substantially prolonged, and were 19.1+/-0. 5s, 43.1+/-0.6s and 26.1+/-1.0s, respectively. In the presence of glycine, at the end of the degradation period, PT, APTT and TT values remained close to the initial values and were 15.5+/-0. 4s, 35.7+/-0.9s and 19.4+/-0.2s, respectively. Percent activities of the coagulation factors V, VII, VIII, IX, X and the coagulation inhibitors protein C, protein S and antithrombin III were recorded. Factors V and VIII were most prone to degradation. Factor V and VIII activities, in control plasma, were approx. 44+/-3.5% and 58+/-2.3%, at the end of storage. In contrast, much higher factor V and VIII activities were maintained in the lyophilized glycine-supplemented plasma: approx. 60+/-3.5% and 74+/-7.0%, correspondingly. The most stable protein was protein C, which showed no signs of degradation under the testing conditions of this study. All tested stabilizers provided protection. Glycine, however, outperformed all tested polyols, providing superior preservation of plasma clotting properties. Thermograms of 60mM glycine in water and 60mM glycine in plasma show that, in the presence of plasma, glycine does not crystallize. The process of freeze-drying caused a complete loss of plasma pCO(2) (gas) and a substantial increase in plasma pH. Citric acid was found to be a suitable pH adjuster for lyophilized/rehydrated plasma.

Blood Preservation↗
PubMed1982

A six-month clinical evaluation of decalcified freeze-dried bone allografts in periodontal osseous defects.

The osteogenic potential of decalcified freeze-dried bone allografts in the treatment of human periodontal osseous defects was evaluated over a 6 month period. Cortical bone, obtained under sterile conditions from a human donor within 24 hours after death, was decalcified, freeze-dried and ground to a particle size of 250 to 500 microns. Twenty-seven osseous defects with one-, two- and wide three-wall morphology were treated. Clinical measurements were made with a stent and a calibrated periodontal probe before surgery, at the time of surgery, and at re-entry. The combined mean osseous regeneration for all defects was 2.4 mm. This represented a 65% mean bone-fill of the original defect. The findings demonstrate that decalcified freeze-dried bone allograft has potential as an osseous grafting material in periodontal therapy.

Alveolar Process↗
PubMed1993

Freeze-drying of cephalothin sodium: granularly agglomerated crystallization during freezing. II.

The mechanism of granularly agglomerated crystallization during freezing of cephalothin sodium (CET-Na) in aqueous solution has been discussed. Our previous report noted that strict control of the following is important in order to obtain crystalline granular agglomerates of CET-Na: (1) thermal history of the solution before receiving freezing, (2) cooling rate in freezing, and (3) aging temperature level in the crystal growth step. In order to clarify the physico/chemical meanings of the individual controls, further investigations have been made: 1) with varying thermal history, aqueous 30-% CET-Na solutions were prepared for storage, first at 0 degrees C with its supersaturation and secondly at 25 degrees C, in an unsaturated state for observing any structural changes by viscosimetry, refractometry, and surface tensiometry; 2) morphological changes in ice crystals during freezing at varying cooling rates, as well as those during the crystal growth step, were observed by polarized-light cryomicroscopy and scanning electron microscopy; 3) melting, as well as crystal growth, at several aging temperature levels were observed by electrical conductometry and also by the above-mentioned techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

Cephalothin↗
PubMed2000

Extraction of antimony and arsenic from fresh and freeze-dried plant samples as determined by HG-AAS.

Six extraction media (acetic acid, EDTA, tetrabutylammonium hydroxide, NaOH, MeOH/H2O, acetonitrile/H2O) were tested for their ability to extract antimony (Sb) and arsenic (As) from freeze-dried poplar leaves, pine shoots and spruce shoots, as well as from a peat matrix. Additionally, the extraction efficiency of Sb and As in fresh and freeze-dried elder leaves and poplar leaves was compared. Total concentrations of Sb and As of aliquots (approximately 220 mg) of the freeze-dried samples were analysed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) after open vessel digestion with adequate mixtures of nitric, sulfuric, hydrochloric, and perchloric acid. Three reference materials GBW 07602 Bush Branches and Leaves, GBW 07604 Poplar Leaves, and SRM 1575 Pine Needles were analysed with every batch of samples to ensure the accuracy and precision of the applied analytical procedures. The use of hydrofluoric acid in the digestion mixture leads to distinctly lower As values (down to 40%) than actual concentrations in the investigated plant materials. Extraction efficiencies were generally low and lower for Sb than for As. Solutions of 0.66 mol L(-1) NaOH liberated highest amounts of Sb with approximately 10% for poplar leaves, and approximately 19% each for pine shoots and spruce shoots. Distinctly higher concentrations of As in NaOH extracts of poplar leaves (22%), pine shoots (32%), and spruce shoots (36%) were quantified. Extraction experiments resulted in yields of 7-9% from fresh elder and poplar leaves, respectively, and 8-13% for freeze-dried samples for Sb. The corresponding values for As were 10-35% for the fresh material and 7-37% for the freeze-dried samples.

Antimony↗
PubMed2000

Effect of protective agents, rehydration media and initial cell concentration on viability of Pantoea agglomerans strain CPA-2 subjected to freeze-drying.

The effect of initial cell density, protective agents and rehydration media on the viability of biocontrol agent Pantoea agglomerans CPA-2 when subjected to freeze-drying was studied. Several additives were tested as protective agents against freeze-drying injury. Maximum viability of the bacterial cells was obtained with disaccharides (survival levels > 60%). Freeze-dried samples were rehydrated with several media; the highest percentage viability was obtained with 10% non-fat skim milk (100%+). The effect of initial bacterial load on the final recovery was dependent on protectant but not on rehydration media. Sucrose was an effective protectant when a high initial concentration (10(10) cfu ml(-1) was used; the opposite occurred with non-fat skim milk. The use of 10(10) cfu ml(-1) as an initial concentration, sucrose as a protectant and non-fat skim milk as a rehydration medium enabled 100% of P. agglomerans viability to be conserved after freeze-drying. Results suggest the possibility of achieving a good formulation system for the studied biocontrol agent with a high number of viable cells to be used toward pathogens, which is desirable for the industrial development of the product.

Animals↗
PubMed1998

Effects of freeze-dry processing conditions on the crystallization of pentamidine isethionate.

The results of this study show that pentamidine isethionate (PI) can exist in at least four crystalline forms-three anhydrates designated as forms A, B, and C, and a trihydrate. Form C is the high-temperature modification, produced by heating forms A, B, and the trihydrate above 130 degrees C and cannot be produced under actual lyophilization conditions. The crystal forms of PI present after freeze-drying depend on the initial solution concentration and the thermal history of freezing. At low concentrations of PI (4% and less), form A is observed regardless of freezing method. At a higher concentration (10%), the crystal forms observed are a function of the freezing method. Three freezing methods were used to effect different cooling rates: (1) cooling on the shelf to 2 degrees C and holding for 3 h prior to decreasing the temperature to -45 degrees C, (2) directly cooling on the shelf from room temperature to -45 degrees C, and (3) dipping the vials in liquid nitrogen. The results show that form A, form B, or a mixture of both forms are present in the freeze-dried solid depending upon whether the trihydrate crystallizes during freezing or not. Since form B can only be produced by dehydration of the trihydrate at low temperature, the presence of this form in the freeze-dried powders depends on the nucleation and growth of the trihydrate during freezing. Photostability studies have demonstrated marked differences between freeze-dried solids frozen under different conditions. The results underscore the importance of recognizing that seemingly subtle differences in processing conditions can have a significant impact on critical quality attributes of freeze-dried products.

Antiprotozoal Agents↗
PubMed1993

The effects of freeze-drying and rehydration on cancellous bone.

Processing technique significantly affects the strength and stiffness of bone for use as a structural alloimplant in reconstructive surgery. The effects of the rehydration of freeze-dried human cancellous bone were studied using 14-mm-diameter cancellous dowels taken from matched cadaveric sites. Three different methods of rehydration were evaluated and compared with unrehydrated freeze-dried and frozen grafts. All samples were biomechanically tested in anatomically matched pair groups to determine compressive strength and stiffness. The strength of each tested graft was expressed as a percentage of its matched pair control. Freeze-dried grafts rehydrated for 24 hours compared with frozen grafts showed no significant difference in mean compressive strength (92.6% +/- 13.3% of control). Analysis of in vacuo versus ex vacuo rehydration at one hour showed a 38% greater mean compressive strength and a 42% greater mean stiffness for the ex vacuo group. Unrehydrated grafts appeared to be both stronger and stiffer than their rehydrated counterparts. These results suggest that the rehydration of freeze-dried grafts may adversely affect graft strength and stiffness. Rehydration under a negative pressure may proceed more rapidly than the process at atmospheric pressures. These findings limit the acceptability of freeze-dried grafts as structural implants.

Adolescent↗
PubMed2002

Crystallization of mannitol below Tg' during freeze-drying in binary and ternary aqueous systems.

PURPOSE: To characterize the phase transitions in a multicomponent system during the various stages of the freeze-drying process and to evaluate the crystallization behavior below Tg' (glass transition temperature of maximally freeze-concentrated amorphous phase) in frozen aqueous solutions and during freeze-drying. METHODS: X-ray powder diffractometry (XRD) and differential scanning calorimetry (DSC) were used to study frozen aqueous solutions of mannitol with or without trehalose. By attaching a vacuum pump to the low-temperature stage of the diffractometer, it was possible to simulate the freeze-drying process in situ in the sample chamber of the XRD. This enabled real-time monitoring of the solid state of the solutes during the process. RESULTS: In rapidly cooled aqueous solutions containing only mannitol (10% w/w), the solute was retained amorphous. Annealing of frozen solutions or primary drying. both below Tg', resulted in crystallization of mannitol hydrate. Similar effects were observed in the presence of trehalose (2% w/w). At higher concentrations (> or =5% w/w) of this noncrystallizing sugar. annealing below Tg' led to nucleation but not crystallization. However, during primary drying, crystallization of mannitol hydrate was observed. CONCLUSIONS: The combination of in situ XRD and DSC has given a unique insight into phase transitions during freeze-drying as a function of processing conditions and formulation variables. In the presence of trehalose, mannitol crystallization was inhibited in frozen solutions but not during primary drying.

Cold Temperature↗
PubMedDate not supplied

Visualization of actin filaments in keratocyte lamellipodia: negative staining compared with freeze-drying.

Depending on the method of preparation, the actin-rich lamellipodia of motile cells can show very different structural organizations. This situation has been a main contributor to differences in current ideas about the possible mechanisms of cell movement. We have here analyzed the structure of the lamellipodium in whole-mount cytoskeletons using one of the most rapid of crawling cells, the fish keratocyte, employing two procedures considered least damaging to actin filament arrays: freeze-drying and negative staining. At the front of the lamellipodium, where filaments density is the highest, freeze-dried images conveyed the impression of a cross-linked network of very short, interconnected filaments--as previously observed by others--whereas the same regions appeared as a diagonal meshwork of long, more or less straight filaments after negative staining. In general, the linearity of actin filaments was not preserved after freeze-drying, except in situations where the filaments had partially dried down onto the substrate before freezing. In the mid and posterior regions of the lamellipodium the actin filaments appeared to be up to several micrometers long by negative staining, whereas their length was impossible to discern by freeze-drying, owing to filament kinking and aggregation and to the nature of the contrasting procedure, which reveals only the upper layers of filaments. We conclude that while freeze-drying preserves the overall three-dimensional structure of the lamellipodium it also introduces fine-structural distortions in actin that obscure actin filament order. Drying in negative stain appears to stabilise the actin network.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin Cytoskeleton↗
PubMed1976

Application of freeze-dried, one-day-old chick erythrocytes to viral hemagglutination and hemagglutination-inhibition tests.

Erythrocytes collected from 1-day-old chicks were stabilized by fixation with formaldehyde and by freeze-drying after treatment with carbon monoxide. Suspensions of freeze-dried erythrocytes in distilled water or physiological saline had a homogeneous bright reddish-purple color. Freeze-dried erythrocytes were compared with fresh erythrocytes for hemagglutination and hemagglutination-inhibition tests for various viruses including rubella, Japanese encephalitis, influenza, mumps, Newcastle disease, and Sendai viruses. After storage at 4 degrees C for 1 year or more, freeze-dried erythrocytes maintained their original appearance and sensitivity to hemagglutination antigens.

Animals↗
PubMed1976

Numerical analysis of heat and mass transfer during freeze-drying.

The transient-state external heat and mass-transfer during freeze-drying was investigated. The spaces between the heaters and porous product-surfaces were simulated as semi porous channels, with mass-injection into the channels from the sublimation of ice. The energy, vorticity, concentration, and stream function/vorticity equations were the governing equations used as the mathematical model. These partial differential-equations were solved by finite-difference, numberical methods. The Fromm, Alternating Direction Implicity, and Upwind Difference methods were used in solving the parabolic equations; and the Successive Over Relaxation method was adopted to solve the elliptic equation. Numerical solutions obtained from the digital computer for the external heat and mass-transfer during freeze-drying were computed for Reynolds numbers equal t0 0.1, 1.0, and 4.0 and Grashof numbers equal to 0, +/- 100, and +/- 1000. The Prandtl number selected for water vapor was 1.0. One set of these solutions were compared to a known, analytical solution, and good agreement was obtained. The external heat and mass-transfer mechanism was then combined with the internal-heat-transfer mechanism developed by Dyer and Sunderland (1968), and the equations describing the relation of heater temperatures and product surface-temperatures developed by Massey and Sunderland (1972). A thorough computer-simulation was carried out for the combined heat and mass-transfer mechanism during freeze-drying of food products.

Computers↗
PubMed1994

Physical stability and protein stability of freeze-dried cakes during storage at elevated temperatures.

The relationship between physical stability of freeze-dried cakes and protein stability during storage was studied using beta-galactosidase as a model protein and inositol as an excipient. Amorphous samples freeze-dried from solutions containing the enzyme and various concentrations of inositol in sodium phosphate buffer (50 mM, pH 7.4) were stored for 7 days over P2O5 at 40 to 70 degrees C. Structural collapse and inositol crystallization were observed in some of the samples, depending on the formulation and storage temperature. The physical stability of freeze-dried samples was also studied by differential scanning calorimeter (DSC). Inositol showed a protein-stabilizing effect when its amorphous form was retained during storage, regardless of structural collapse. However, crystallization of inositol during storage removed its stabilizing effect. Addition of water-soluble polymers such as dextran, Ficoll and carboxymethyl cellulose sodium salt (CMC-Na) preserved activity of the enzyme by preventing inositol crystallization.

Aspergillus oryzae↗
PubMed1989

Morphological and elemental integrity of freeze-fractured, freeze-dried cultured cells during ion microscopic analysis.

The effects of progressive ion beam bombardment on freeze-fractured, freeze-dried cultured cells during ion microscopic (SIMS) analysis were studied with scanning electron microscopy (SEM) and ion microscopy. The freeze-fracture, freeze-dry sample preparation method was generally found to preserve cell morphology to a level far exceeding the spatial resolution of the ion microscope, with splitting at the nuclear envelope being the most commonly observed artefact. SEM monitoring of surface topography of an NRK-49F fibroblast after various ion bombardment doses showed relatively uniform erosion of cellular material, with some apparent selective retention of small cytoplasmic granules. Prolonged bombardment produced no detectable lateral elemental translocation. 41K+/24Mg+ signal ratios from Swiss 3T3 fibroblasts and RBL rat basophilic leukaemia cells were shown to vary generally by less than 10% during the course of extended ion bombardment. GM0415 human skin fibroblasts containing engorged lysosomes characteristic of Hurler's Syndrome were used to evaluate the effects of ion bombardment during a typical analysis session, where ion images of 39K+, 23Na+, 40Ca+ and 24Mg+ are sequentially recorded. This cell line was chosen as a worst-case system, because these cells are often thinly spread and possess extreme surface topography. Thin cell edges were shown sometimes to sputter away during analysis, giving misleadingly low ion signals from these regions in some 24Mg+ micrographs. Various non-uniform sputtering phenomena occurring in the submicrometre spatial domain had little or no measurable impact on local intensities in ion micrographs, indicating that freeze-dried, freeze-fractured cells are sampled in a sufficiently uniform fashion that quantitative ion microscopic evaluations of intracellular elemental levels in the general cytoplasmic or nuclear regions are feasible.

Animals↗
PubMed1976

Freeze-drying of histocompatibility typing sera.

This report describes a unit employed for the freeze-drying of histocompatibility typing sera using a 50-h cycle. The unit will process approximately 3,200 3-ml vials with a final residual moisture content of less than 2%. The system employs dry ice-alcohol cooled circulating baths to maintain the condensers below -60 degrees C, and two shelf-cooling baths to maintain the product at the required temperatures during the freeze-drying process. The results of a recently conducted 5-year study of the effect of residual moisture as a function of time and storage temperature are also included. Studies conducted to date indicate that with residual moistures below 2%, freeze-dried histocompatibility sera can be stored at +4 degrees C without the loss of significant tissue typing factors. Solubility of all serum was lost when samples were stored at +37 degrees C or higher during this same 5-year period. The long-term storage studies are being continued.

Drug Storage↗
PubMed2003

Uptake of erythromycin by first-feeding sockeye salmon, Oncorhynchus nerka (Walbaum), fed live or freeze-dried enriched adult Artemia or medicated pellets.

The potential to use adult Artemia to deliver erythromycin to first-feeding sockeye salmon, Oncorhynchus nerka (Walbaum), was investigated in three trials. In the first trial, first-feeding sockeye were fed live erythromycin enriched adult Artemia or pellets containing equal amounts of erythromycin for 35 days. At the end of the trial, tissue erythromycin concentration of the fish fed the live Artemia was significantly greater (P < 0.05, 25.52 +/- 1.29 microg mL(-1); mean +/- SEM), than the tissue concentration of the fish fed the pellets (0.72 +/- 0.01 microg mL(-1)). In the second trial, first-feeding sockeye were fed either live or freeze-dried bioencapsulated erythromycin (adult Artemia) or pellets containing erythromycin daily for 21 days. Mean daily erythromycin concentration in fish fed the freeze-dried Artemia, live Artemia, or pellets did not differ significantly. In the third trial, apparent erythromycin digestibility was determined. Significantly more (P < 0.05) erythromycin was retained by juvenile sockeye fed freeze-dried bioencapsulated erythromycin (98.3 +/- 1.0%) compared with medicated pellets (89.2 +/- 1.7%). Uptake of bioencapsulated erythromycin from adult Artemia (live or freeze-dried) appears to be greater than uptake from pellets. Freeze-dried and live Artemia were equally effective at delivery suggesting enriched freeze-dried adult Artemia could be produced into a highly palatable, consistent, off-the-shelf product.

Administration, Oral↗
PubMed1989

The gravimetric method for the determination of residual moisture in freeze-dried biological products.

The gravimetric test for the determination of residual moisture in freeze-dried biological products performed in a humidity- and temperature-controlled room with the use of scrupulous gravimetric analytical technique can be used to accurately determine residual moisture in freeze-dried biological products such as antihemophilic factor (human) or honey bee venom allergenic extract. This method determines the first water of hydration of sodium tartrate dihydrate (7.93%) to within 1.3% of the calculated value with a relative standard deviation of 0.3% for 10 replicates. For this gravimetric procedure, freeze-dried samples containing from 1.12 to 4.4% residual moisture had relative standard deviations ranging from 3.6 to 9.1%. Samples containing less than 1.0% residual moisture by the gravimetric method such as intravenous immune globulin and antihemophilic factor (human) had relative standard deviations ranging from 16.7 to 47.0%. Relative standard deviations for residual moisture tests performed on comparable samples by the Karl Fischer and thermogravimetric methods showed similar variability.

Animals↗