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At least 19 recordsLinked to original sources
PubMed2002

Effect of freeze-drying, freezing and frozen storage of blood plasma on fibrin network characteristics.

INTRODUCTION: We investigated the effect of freezing, freeze-drying and the duration of frozen storage of blood plasma on fibrin network characteristics of clots subsequently produced. MATERIALS AND METHODS: Fibrin network characteristics of clots made from freeze-dried and frozen plasma were compared to those made from fresh plasma. Freeze-dried pooled plasma was reconstituted and frozen each month for 4 months to describe the differences in fibrin networks that occur as a result of storage of the plasma over this period. RESULTS: Compared to freezing, freeze-drying of plasma had fewer undesirable effects on the fibrin network characteristics measured. Only the permeability of the clots from freeze-dried plasma was significantly less compared to the values of clots from the fresh plasma (p=0.005). Fibrinogen activity and mass-length ratio, compaction and fibrin content of the clots made from frozen plasma were, however, all significantly affected by freezing. Mass-length ratio and compaction showed a linear decrease and fibrin content a linear increase over a 4-month frozen storage period, thereby indicating that these variables were probably not stable. Large variation found in the data from each month indicates that there may be other factors, apart from storage time, that have a larger influence on these fibrin network characteristics, than frozen storage of plasma for 4 months. Storage of plasma in the freeze-dried form for 4 months resulted in a significant increase in fibrinogen (p=0.0004) but significant decrease in fibrin content (p=0.0002). CONCLUSIONS: Although the process of freeze-drying had fewer undesirable effects on the measured fibrin network characteristics compared to freezing, storage in both forms resulted in altered activity upon rehydration and thawing.

Blood Coagulation↗
PubMed1999

The effects of freeze drying and freeze drying additives on the prothrombin time and the international sensitivity index.

AIM: To determine whether freezing, freeze drying protective additives, or freeze drying of plasma samples from patients on coumarin treatment and from normal individuals affects prothrombin times or the international sensitivity index (ISI) calibration. METHODS: The effect of the addition of the protective additives singly and combined on the prothrombin time of coumarin samples and normal samples before and after freeze drying was observed using high and low ISI reference thromboplastins. ISI values were also determined. RESULTS: Freezing caused a prolongation of prothrombin time in the normal plasma samples with both reagents, which was significant with the low ISI human. Prolongation (non-significant) of the prothrombin time in coumarin plasma samples occurred with the human reagent only. Significant prolongation of normal prothrombin time by some of the protective additives before and after freeze drying was observed with both thromboplastins but to a greater extent with the human. Significant prolongation of prothrombin time in coumarin plasma samples was observed, but again was more marked with human thromboplastin. An approximate ISI was determined on the 20 coumarin samples. The only marked ISI change was with the WHO human thromboplastin after freeze drying of plasma, where a decrease from 0.95 to 0.90 was observed, corresponding to a marked prothrombin ratio increase. CONCLUSIONS: Freeze drying additives and the freeze drying procedure prolong normal and coumarin prothrombin times, with low ISI thromboplastin. Less marked prolongations occurred with a high ISI rabbit reagent, coumarin samples showing more significant prolongations. Marked ISI change in freeze dried plasma was only recorded with the low ISI ECAA human reagent. Frozen normal plasma samples cannot be used with confidence for ISI calibrations.

Animals↗
PubMed1985

Critical-point drying versus freeze drying for scanning electron microscopy: a quantitative and qualitative study on isolated hepatocytes.

Critical-point drying and freeze drying were compared both quantitatively and qualitatively as preparative procedures for scanning electron microscopy. Isolated hepatocytes were used as model cells. Nomarski differential interference contrast microscopy was used for light microscopic measurements of the hepatocytes in the unfixed, the glutaraldehyde fixed, the glutaraldehyde + OsO4 fixed, the critical-point dried and the freeze dried states. Critical-point dried hepatocytes were found to shrink to 38% of glutaraldehyde + OsO4 fixed volume, whereas optimal freeze dried hepatocytes (frozen in water saturated with chloroform and freeze dried at 183 K for 84 h) were found to shrink to 51% of glutaraldehyde + OsO4 fixed volume. Transmission and scanning electron micrographs of the critical-point dried cells showed well-preserved ultrastructure and surface structure. Micrographs of the freeze dried cells showed ultrastructure destroyed by internal ice crystals and surface structure destroyed by external ice crystals. Double-fixed isolated hepatocytes were shown to swell during storage in buffer and to shrink during storage after critical-point drying. For low magnification scanning electron microscopy (up to about 3000 times) both critical-point drying and freeze drying can be used. However, for high magnification scanning electron microscopy, critical-point drying is superior to freeze drying.

Animals↗
PubMed2003

Long-term preservation of mouse spermatozoa after freeze-drying and freezing without cryoprotection.

The widespread production of mice with transgenes, disrupted genes and mutant genes, has strained the resources available for maintaining these mouse lines as live populations, and dependable methods for gamete and embryo preservation in these lines are needed. Here we report the results of intracytoplasmic sperm injection (ICSI) with spermatozoa freeze-dried or frozen without a cryoprotectant after storage for periods up to 1.5 years. Freeze-dried samples were stored at 4 degrees C. Samples frozen without cryoprotection were maintained at -196 degrees C. After storage, spermatozoa were injected into the oocytes by ICSI. Zygotic chromosomes and fetal development at Day 15 of gestation were examined after 0, 1, 3, 6, 9, and 12 mo of sperm storage. When fresh spermatozoa were used for ICSI, 96% of resultant zygotes contained normal chromosomes, and 58% of two-cell embryos transferred developed to normal viable fetuses. Similar results were obtained when spermatozoa were frozen without cryoprotection and then used for ICSI (87% and 45%, respectively; P > 0.05) and after 12 mo of sperm storage (mean of six endpoints examined: 87% and 52%, respectively; P > 0.05). Freeze-drying decreased the proportion of zygotes with normal karyoplates (75% vs. 96%; P < 0.001) and the proportion of embryos that developed into fetuses (35% vs. 58%; P < 0.001), but similar to freezing, there was no further deterioration during 12 mo of storage (mean of six endpoints examined: 68% and 34%, respectively; P > 0.05). Live offspring were obtained from both freeze-dried and frozen spermatozoa after storage for 1.5 yr. The results indicate that 1) the freeze-drying procedure itself causes some abnormalities in spermatozoa but freezing without cryoprotection does not and 2) long-term storage of both frozen and freeze-dried spermatozoa is not deleterious to their genetic integrity. Freezing without cryoprotection is highly successful, simple, and efficient but, like all routine sperm storage methods, requires liquid nitrogen. Liquid nitrogen is also required for freeze-drying, but sperm can then be stored at 4 degrees C and shipped at ambient temperatures. Both preservation methods are successful, but rapid freezing without cryoprotection is the preferred method for preservation of spermatozoa from mouse strains carrying unique genes and mutations.

Animals↗
PubMed1984

Freeze drying and freeze substitution combined with low temperature-embedding. Preparation techniques for microprobe analysis of biological soft tissues.

An X-ray microanalytical and morphological investigation was carried out on rapidly frozen freeze-dried or freeze-substituted tissues. A comparison was made between different embedding and polymerisation procedures following freeze substitution and freeze drying. The investigation also included an analysis of specimens which had been infiltrated, embedded and polymerised by ultraviolet irradiation at low temperatures with Lowicryl-HM20. The method of freeze drying, followed by embedding and polymerisation at low temperatures in vacuo was found to give satisfactory results, comparable with more tedious and hazardous freeze substitution technique.

Animals↗
PubMed2005

Thermoanalytical techniques for the investigation of the freeze drying process and freeze-dried products.

A key challenge facing the pharmaceutical industry is the production of biotechnological drug products such as proteins in a stable form. Freeze-drying is preferred for manufacturing such products because of the low temperatures used. However, the protein may still degrade during the process necessitating the inclusion of a protectant. This review describes the range of thermal analysis techniques that have been used to investigate the properties of formulations to be freeze dried and the resultant products. This approach has allowed insight into the key parameters required for design of formulations and processes that will generate the best possible products.

Biological Products↗
PubMed1979

Binding of concanavalin-A to critical-point-dried and freeze-dried human lymphocytes.

When human lymphocytes are treated with concanavalin-A (con A) and hemocyanin, the hemocyanin marker, which demonstrates con A binding sites, can be visualized by scanning (SEM) and transmission electron microscopy (TEM) on both critical-point-dried and freeze-dried cells. The ability to visualize the hemocyanin marker by SEM, its quantity and distribution, were all similar in lymphocytes prepared by both drying procedures. By TEM, hemocyanin was seen adjacent to the plasma membrane on critical-point-dried lymphocytes. In contrast, freeze-dried cells showed hemocyanin labeling at some distance from the plasma membrane (40-70 nm) as well as adjacent to it. The distribution of hemocyanin corresponded to the thickness of the amorphous coat seen on fixed, freeze-dried cells. Therefore, the extracellular coat on freeze-dried lymphocytes is a carbohydrate-containing glycocalyx.

Concanavalin A↗
PubMed2005

Crystallization and X-ray diffraction of spray-dried and freeze-dried amorphous lactose.

Crystallization of spray-dried and freeze-dried amorphous lactose over different relative vapor pressures (RVP) and storage times was studied. Crystallization was observed from increasing peak intensities in X-ray diffraction patterns. Lactose was crystallized in the samples stored at RVP of 44.1% and above in both types of dehydrated powders. The rate of crystallization increased with increasing RVP and storage time. Similar crystallization behavior of both spray-dried and freeze-dried lactose was observed. Lactose crystallized as alpha-lactose monohydrate, anhydrous beta-lactose, and the anhydrous form of alpha- and beta-lactose in a molar ratio of 5:3 and 4:1 in both spray-dried and freeze-dried forms. Peak intensities of X-ray diffraction patterns for anhydrous beta-lactose were decreased, and for alpha-lactose monohydrate increased with increasing storage RVP and time. The crystallization data were successfully modeled using Avrami equation at RVP of 54.5% and above. The crystallization data obtained is helpful in understanding and predicting storage stability of lactose-containing food and pharmaceutical products.

Crystallization↗
PubMed2005

Distinct effects of sucrose and trehalose on protein stability during supercritical fluid drying and freeze-drying.

Supercritical fluid (SCF) drying has been proposed as an alternative for freeze-drying to stabilize proteins. Here we studied the influence of sucrose and trehalose during SCF drying on the protein stability and the physical powder characteristics of lysozyme and myoglobin formulations. The results obtained with SCF drying were compared with the results after freeze-drying of the same solutions. Aqueous protein solutions, with or without sugar, were sprayed into a SCF mixture of carbon dioxide and ethanol. The dried products were analyzed by residual water measurements, scanning electron microscopy, X-ray powder diffraction and differential scanning calorimetry. After reconstitution the protein structure was studied by UV/VIS, circular dichroism and fluorescence spectroscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and bioactivity assay (lysozyme). The SCF dried and freeze-dried formulations showed comparable water contents, but their physical properties were substantially different. All freeze-dried cakes were amorphous with fully preserved protein structure. SCF dried sucrose-containing formulations showed agglomerated crystalline particles, whereas SCF dried trehalose-containing formulations appeared to consist of amorphous spherical particles. Particle morphology of excipients-free proteins was protein specific. Nearly all SCF dried lysozyme could be readily reconstituted, but for myoglobin significant fractions of SCF protein did not dissolve, especially in the absence of sugars. Covalent aggregation was not observed for the two proteins. For the recovered soluble fractions, the secondary protein structure was preserved. The tertiary structure was preserved for lysozyme, but not entirely for myoglobin. Surprisingly, during SCF drying trehalose was less protective than sucrose for myoglobin.

Animals↗
PubMed1999

Protein inhalation powders: spray drying vs spray freeze drying.

PURPOSE: To develop a new technique, spray freeze drying, for preparing protein aerosol powders. Also, to compare the spray freeze-dried powders with spray-dried powders in terms of physical properties and aerosol performance. METHODS: Protein powders were characterized using particle size analysis, thermogravimetric analysis, scanning electron microscopy, X-ray powder diffractometry, and specific surface area measurement. Aerosol performance of the powders was evaluated after blending with lactose carriers using a multi-stage liquid impinger or an Anderson cascade impactor. Two recombinant therapeutic proteins currently used for treating respiratory tract-related diseases, deoxyribonuclase (rhDNase) and anti-IgE monoclonal antibody (anti-IgE MAb), were employed and formulated with different carbohydrate excipients. RESULTS: Through the same atomization but the different drying process, spray drying (SD) produced small (approximately 3 microns), dense particles, but SFD resulted in large (approximately 8-10 microns), porous particles. The fine particle fraction (FPF) of the spray freeze-dried powder was significantly better than that of the spray-dried powder, attributed to better aerodynamic properties. Powders collected from different stages of the cascade impactor were characterized, which confirmed the concept of aerodynamic particle size. Protein formulation played a major role in affecting the powder's aerosol performance, especially for the carbohydrate excipient of a high crystallization tendency. CONCLUSIONS: Spray freeze drying, as opposed to spray drying, produced protein particles with light and porous characteristics, which offered powders with superior aerosol performance due to favorable aerodynamic properties.

Administration, Inhalation↗
PubMed1992

Enzyme histochemistry and immunohistochemistry with freeze-dried or freeze-substituted resin-embedded tissue.

Freeze-drying or freeze-substitution, combined with low-temperature resin-embedding, represents a new approach to the optimum preservation of tissue for enzyme histochemistry and immunohistochemistry. This method, which avoids tissue fixation, combines excellent tissue morphology with the preservation of enzyme activity and immunoreactivity and allows high-resolution enzyme histochemical and immunohistochemical studies to be performed. The activity of a wide range of enzymes can be demonstrated in sections of freeze-dried or freeze-substituted resin-embedded tissue. Enzymes are retained in situ with high activity, accurate localization and no diffusion. Immunohistochemical studies can also be performed on resin sections, and antigens--especially labile antigens--are immobilized in situ without denaturation and can be demonstrated with high sensitivity and accurately localized. This method allows the localization and distribution of enzymes and antigens to be studied in relation to excellent histological and cytological detail.

Animals↗
PubMed2002

A retrospective case series comparing the use of demineralized freeze-dried bone allograft and freeze-dried bone allograft combined with enamel matrix derivative for the treatment of advanced osseous lesions.

BACKGROUND: Combined regenerative approaches have been used for treating advanced osseous lesions around teeth. The aim of combining treatments is to enhance both clinical predictability and regenerative outcome compared to a monotherapeutic approach. This case series from a private practice reports on the clinical efficacy of an enamel matrix derivative (EMD) combined with either demineralized freeze-dried bone allograft (DFDBA) or freeze-dried bone allograft (FDBA) in the treatment of advanced infrabony lesions. The advanced lesions were veneered by a rapidly formed absorbable polymer barrier of poly(DL-lactide) to enhance graft containment. METHODS: A total of 22 consecutive patients, each contributing one infrabony lesion, are reported. After patients completed presurgical preparation, the infrabony lesions were surgically treated with a combined approach that included root surface treatment with citric acid. The two groups differed in their composite graft; one received DFDBA-EMD (n = 10) and the other received FDBA-EMD (n = 12). Patients followed a stringent postoperative protocol and were evaluated 6 months postsurgery. Clinical outcomes were assessed by changes in clinical attachment level (CAL) and probing depth (PD) from pretreatment. Surgical re-entry of several sites was possible in each group. RESULTS: CAL at pretreatment measured 9.2 +/- 1.3 mm and 9.1 +/- 1.9 mm for DFDBA-EMD and FDBA-EMD groups, respectively, with corresponding PD of 8.4 +/- 1.6 mm and 8.9 +/- 2.0 mm for each group. At 6 months post-treatment, CALs were reduced to 4.7 +/- 1.3 mm and 3.8 +/- 1.0 mm for DFDBA-EMD and FDBA-EMD groups, respectively; with corresponding PD decreased to 3.0 +/- 0.8 mm and 3.2 +/- 1.0 mm. Relative improvements in CAL for the DFDBA-EMD and DFDBA-EMD groups were 49.1% +/- 11.0% and 57.3% +/- 9.4%, respectively (P <0.07). CONCLUSIONS: This case series demonstrates the clinical benefits of using a combined therapeutic approach in which a biologic mediator (EMD) was combined with either DFDBA or FDBA. In this limited case series, a trend was observed towards greater improvement in clinical attachment level gain in advanced infrabony defects when EMD was combined with FDBA as compared to DFDBA. Larger prospective controlled clinical trials are needed to determine if differences exist in the relative efficacy of DFDBA versus FDBA in combination with EMD.

Absorbable Implants↗
PubMed1981

Investigation of membrane complexes of myelin and gregarine pellicle by freeze-drying and freeze-etching methods.

By the changes introduced in the standard procedures of the freeze-drying method (fixation, transportation of specimens from a vacuum apparatus into glass capillary tubes, and embedding) we have managed to simplify the method and to increase the reliability of the results. Fixation of the tissue was carried out after freeze-drying in molecular beams of OsO4 or in an OsO4 solution in carbon tetrachloride. The samples were embedded in araldite through mixtures of carbon tetrachloride and araldite. Membranes of myelin and gregarine pellicle were investigated. The repeat period of myelin at fixation of nerves after freeze-drying in OsO4 molecular beams is 11.2 +/- 0.5 nm and in an OsO4 solution in carbon tetrachloride, 12 +/- 0.4 nm. A tetragonal reticulum was revealed on the plasma-membrane extracellular surface of gregarine which had been prepared by freeze-drying. This type of structure is never observed after the routine fixation in water, while an analogous structure is revealed after freeze-etching.

Animals↗