Optimal Freezing Research Articles

Building the Method and the Mathematical Model to Determine the Rate of Freezing Water inside Royal Jelly in the Freezing Process

The aim of this study is building the new method and the mathematical model to determine the rate of freezing water inside Royal jelly of the freezing process for using in preservation as well as for using in the freeze drying. The results obtained were used to determine the optimal freezing temperature of Royal jelly for preservation of -5.73°C (corresponding to the rate of freezing water inside Royal jelly of 86.02% over 86%) and for the freeze drying of -18.33°C (corresponding to the rate of freezing water inside Royal jelly of 100%). This is basic parameters and very essential to set up the technological mode of the freezing process Royal jelly for preservation as well as for freeze drying.

Freezing period strongly impacts the emergence of a global consensus in the voter model

It is well known that human beings do not always change opinions or attitudes, since the duration of interaction with others usually has a significant impact on one's decision-making. Based on this observation, we introduce a freezing period into the voter model, in which the frozen individuals have a weakened opinion switching ability. We unfold the presence of an optimal freezing period, which leads to the fastest consensus, using computation simulations as well as theoretical analysis. We demonstrate that the essence of an accelerated consensus is attributed to the biased random walk of the interface between adjacent opinion clusters. The emergence of an optimal freezing period is robust against the size of the system and the number of distinct opinions. This study is instructive for understanding human collective behavior in other relevant fields.

Leakage of Phosphatases and Fertility of Buck Semen Cryopreserved under Different Freezing Modes

Present study was conducted on 160 ejaculates collected at weekly interval by artificial vagina method from 13 adult Sirohi bucks. Pooled ejaculates were diluted with Tris-egg yolk-citric acid-fructose-glycerol extender (1:4), filled and sealed in straws. Few straws of diluted semen were thawed (40° C/15 seconds) and assessed for acid and alkaline phosphatases (ACP and AKP) in seminal plasma of diluted semen (Control Group). Remaining semen straws were randomly grouped to constitute freezing mode groups (M1, M2, M2, and M4) and processed further for cryo-preservation of semen. Accordingly diluted semen straws were cooled @-4° C/minute from 25° C up to 5° C thereafter equilibrated for 2 hours and frozen up to -160° C @ 15, 20, 25 and 300 C/minute for M1, M2, M3 and M4 groups respectively. These frozen straws were hold at this temperature for 2 minutes then stored separately in LN2. After 7 days of storage, straws from each freezing mode group were thawed and assessed for ACP and AKP in seminal plasma. In vivo fertility trials were also conducted with straws of control (fresh diluted semen) as well as freezing mode groups (frozen at different freezing rates). Least square analysis of variance for the data obtained revealed highly significant (P ≤ 0.01) rise in the seminal plasma ACP and AKP enzyme levels in frozen thawed semen as compared to that in fresh diluted semen. The Values of ACP and AKP also differed significantly (P ≤ 0.05) among all the freezing mode groups wherein lowest values of ACP were observed in M3 group followed by M4, M2 and M1 groups in increasing order whereas, lowest values of AKP were observed in M3 followed by M2, M4 and M1 groups in increasing order. Highest fertility rates were observed with semen from M3 followed by M2, M4 and M1 groups. On the basis of enzyme leakage and in-vivo fertility trials, the optimum freezing rate for cryopreservation protocol was arrived at 25° C/minute.DOI: http://dx.doi.org/10.3126/ijasbt.v1i4.8913 Int J Appl Sci Biotechnol, Vol. 1(4): 202-207

EFFECT OF FREEZING ON THE BIOCHEMICAL AND ENZYMATIC ACTIVITY OF LACTOBACILLUS BULGARICUS

The problem of preserving the viability, stability and activity of thermophilic lactic acid bacteria Lactobacillus bulgaricus upon freezing is considered. The effect of different freezing conditions and low-temperature storage on the biochemical and morphological properties and stability of the DNA of L. delbrueckii ssp. bulgaricus has been investigated. Sensory evaluation has been carried out for non-frozen bacterial starter cultures containing L. bulgaricus, and their basic physical and chemical parameters (titratable and active acidity and relative viscosity) have been determined. The influence of low temperature on these parameters has been investigated. The effect of freezing and low-temperature storage on the antagonistic activity of L. delbrueckii ssp. bulgaricus strains has been elucidated. The optimum freezing and storage temperatures for the starters containing L. bulgaricus have been determined.

Fabrication of Three-Dimensional Porous Keratin/PEO Biological Scaffolds

In order to prepare the keratin biological scaffold, keratin was firstly extracted from human hair by immersing in 200mL of aqueous solution containing 7mol/L urea, 2wt% Sodium dodecyl sulfate (SDS), and 5wt% sodium disulfite (Na2S2O6). The mixture was then heated to 95°C, shaking for 4h, and filtered through a stainless-steel mesh, dialyzed against 3L of distilled water, with cellulose tubing having a molecular weight cutoff of 10000~14000Da for 36h and filtered again. To examine the property of keratin scaffold, the vacuum freeze-drying process of pure keratin was investigated to find the optimum process. In order to further improve the property of keratin scaffold, different contents of Poly Ethylene Oxide (PEO) were added into the keratin solution. The result showed that the optimum freezing process was that Freezing at room temperature for 4h, and then put the sample into the refrigerator from ambient temperature to-20°C for 4h. Then the sample was put into the cold trap for 24h at-56°C. During the last 4 hours, the vacuum pump was opened and the frozen temperature was raised gradually. The keratin scaffold with good mechanical properties and uniform porosity was fabricated when the concentration of keratin solution was 10wt%. Additionally, PEO plays an important role in improving the flexibility of keratin/PEO scaffold.

Development of a novel methodology for cryopreservation of melanoma cells applied to CSF470 therapeutic vaccine

CSF470 vaccine is a mixture of four lethally irradiated melanoma cell lines, administered with BCG and GM-CSF, which is currently being tested in a Phase II/III Clinical trial in stage II/III melanoma patients. To prepare vaccine doses, irradiated melanoma cell lines are frozen using dimethyl sulfoxide (Me2SO) and stored in liquid nitrogen (liqN2). Prior to inoculation, doses must be thawed, washed to remove Me2SO and suspended for clinical administration. Avoiding the use of Me2SO and storage in liqN2 would allow future freeze-drying of CSF470 vaccine to facilitate pharmaceutical production and distribution. We worked on the development of an alternative cryopreservation methodology while keeping the vaccine’s biological and immunogenic properties. We tested different freezing media containing trehalose suitable to remain as excipients in a freeze-dried product, to cryopreserve melanoma cells either before or after gamma irradiation. Melanoma cells incorporated trehalose after 5h incubation at 37°C by fluid-phase endocytosis, reaching an intracellular concentration that varied between 70–140mM depending on the cell line. Optimal freezing conditions were 0.2M trehalose and 30mg/ml human serum albumin, at −84°C. Vaccine doses could be frozen in trehalose at −84°C for at least four months keeping their cellular integrity, antigen expression and apoptosis/necrosis profile after gamma-irradiation as compared to Me2SO control. Non-irradiated melanoma cell lines also showed comparable proliferative capacity after both cryopreservation procedures. Trehalose-freezing medium allowed us to cryopreserve melanoma cells, either alive or after gamma irradiation, at −84°C avoiding the use of Me2SO and liqN2 storage. These cryopreservation conditions could be suitable for future freeze-drying of CSF470 vaccine.

Optimizing conditions for treating goat semen with cholesterol-loaded cyclodextrins prior to freezing to improve cryosurvival

The fertility of goat sperm is highly variable and new methods for improving sperm cryosurvival are needed. Cholesterol plays important roles in membrane fluidity, cold shock sensitivity and cryodamage, and treating sperm from cold-shock sensitive species with cholesterol-loaded cyclodextrins (CLC) prior to cryopreservation enhances sperm cryosurvival. The aim of this study was to develop a CLC-treatment to optimize goat sperm cryopreservation. A total of 45 ejaculates coming from eleven adult Murciano-Granadina bucks were used and three experiments were conducted to determine: (1) the optimal CLC concentration to treat goat sperm; (2) the optimal time to treat the sperm (before or after seminal plasma removal); and (3) optimal freezing diluent (either of two Tris-citrate diluents containing 2% or 20% egg yolk and 4% glycerol or a skim milk diluent with 7% glycerol) to cryopreserve goat sperm. Goat sperm cryosurvival rates were greatest when they were treated with 1mg CLC/120×106sperm prior to freezing. The benefit was also greatest if the sperm were treated with CLC after seminal plasma removal. Finally, CLC treatment improved sperm cryosurvival rates for sperm frozen in all three diluents, however, CLC treatment was most effective for sperm frozen in egg-yolk diluents. In conclusion, treating goat sperm, with CLC prior to cryopreservation, improved sperm cryosurvival rates. In addition, CLC treatment was effective for all freezing diluents tested, making this technology practical for the industry using current cryopreservation techniques. Nevertheless, additional studies should be conducted to determine how CLC might affect sperm functionality and fertilizing ability.

The effect of freezing rate on the quality of striped bass sperm

Several studies have been conducted in an attempt to determine the optimal freezing rate for cryopreservation of striped bass (Morone saxatilis) sperm. In this study, the effects of freezing rate (−10 °C, −15 °C, −20 °C, and −40 °C/min) on gamete quality was examined, using Sybr-14 and propidium iodide to determine viability (sperm cell membrane integrity), ATP concentration using a luciferin-luciferase bioluminescence assay, and a CEROS computer-assisted sperm analysis system to characterize striped bass sperm motion. Adult male striped bass (N = 12) were sampled once a week for 5 weeks. Collected samples were extended, cryoprotected using a 7.5% (vol/vol) dimethyl sulfoxide final concentration solution, and frozen using a Planer Kryosave controlled-rate freezer. Samples were stored in liquid nitrogen for 49 days, and sperm quality was re-evaluated after thaw (same methods). Sperm cryopreserved at −40 °C/min resulted in means for total motility (10.06%), progressive motility (7.14%), ATP concentration (0.86 pmol/106 cells), and sperm viability (56.5%) that were greater (P < 0.05) than those for slower cooling rates. Therefore, −40 °C/min was the optimal freezing rate (among those tested) for cryopreservation of striped bass sperm.

Basic Study on Visualization of a Cell During Freezing Using Electrical Impedance Tomography

Visualization of a cell during freezing was tried as a first trial using electrical impedance tomography (EIT). During freezing of a grain of Citrus Sudachi, we found good agreement between video and EIT images. These results indicated that EIT has possibility to visualize a cell in freezing process. I. INTRODUCTION The cryopreservation technology enables long term storage of cells and biological tissues, since theoretically their metabolism is stopped due to freezing. However, there is difficulty in using this technique for complex structure of biological tissues because it may cause an injury, such as denaturation, to the cell membrane by concentrating of the intracellular solution with the extracellular freezing. The destruction of the cell membrane and the intracellular microstructure can happen due to nucleation of ice crystals (intracellular freezing), which depends on the cooling rate of the freezing process (1). If we can visualize a cell or a tissue structure during freezing in real time, an optimal freezing method can be developed. In this study, report the results of a preliminary trial to visualize a cell during freezing process using electrical impedance tomography (EIT) (2).

EFFECT OF EQUILIBRATION DURATION, VAPOUR TEMPERATURE AND EXPOSURE VAPOUR DURATION ON CRYOPRESERVED SPERM OF AFRICAN CATFISH

The objective of this study was to obtain the optimal freezing rate with special focus on equilibration duration, vapour temperature and exposure vapour duration on sperm motility characteristics (SMCs) of African catfish (Clarias gariepinus) using Fish-Ringer Extender (FRE) with fixed 10% Dimethyl-sulfoxide (DMSO) as cryoprotectant. Briefly, the straws containing the sperm were placed in a refrigerator at 4oC with three equilibration durations (120, 140 or 160 min) after which exposed to liquid nitrogen vapour at three vapour temperatures (-80, -90 or -100oC) with three exposure vapour durations (5, 10 or 15 min). Finally, the straws were directly plunged into liquid nitrogen vapour at -196oC. The frozen sperm were thawed at 30oC for 30 sec to evaluate the sperm movement characteristics using the Automated Semen Analyzer-IVOS (Hamilton Thorne, USA). Results showed that the highest values of total motility and progressive motility obtained were combination factors of 120 min equilibration duration, -100oC vapour temperature and 15 min vapour exposure duration (87.44 ± 2.07% and 28.22 ± 2.16%, respectively). Combination of 120 min, -100oC and 15 min gave the highest value of rapid velocity (38.56 ± 3.10%), while combination of 120 min, -80oC and 10 min gave the lowest value (16.33 ± 3.21%). The highest values of Velocity Average Path (VAP), Straight-line Velocity (VSL) and Curvilinear Velocity (VCL) were attained by combination of 120 min, -80oC and 15 min which produced 68.76 ± 6.42%, 60.49 ± 6.01% and 94.71 ± 6.27%, respectively. For combination of 120 min, -100oC and 15 min was probably the optimum condition in which positive correlations were shown between total motility and progressive motility; total motility and rapid; total motility and VAP; total motility and VSL; total motility and VCL; progressive motility and rapid; progressive motility and VAP; progressive motility and VSL; progressive motility and VCL; rapid and VAP; rapid and VSL; rapid and VCL; static and Straightness (STR); VAP and VSL; VAP and VCL; VSL and VCL and STR and Linearity (LIN) (p &gt; 0.05). In conclusion, under the present conditions, the optimal frozen-thawed sperm motility characteristics in African catfish using FRE extender was obtained with combination of 120 min equilibration duration, -100oC vapour temperature and 5 to 15 min exposure vapour duration. It is recommended that FRE extender using DMSO as cryoprotectant apparently is suitable to cryopreserve the sperm of African catfish (Clarias gariepinus).

66. Development of a novel methodology for cryopreservation of melanoma cells applied to the CSF470 therapeutic vaccine

CSF470 therapeutic vaccine is a mixture of four lethally irradiated melanoma cell lines, administered with BCG and GM-CSF, which is being tested in a Phase II/III clinical trial in stage II/III melanoma patients. Currently, irradiated cells that comprise CSF470 vaccine are frozen using dimethyl sulfoxide (Me2SO) as a cryoprotectant and stored in liquid nitrogen (LN2) until its use. Prior to inoculation, each dose must be thawed under sterile conditions, washed to remove Me2SO and finally resuspended until clinical i.d. administration. In order to facilitate CSF470 pharmaceutical production and distribution we need to develop a methodology that allows the preservation of CSF470 in a freeze-dried formulation, avoiding storage in LN2 while keeping its biological and immunogenic properties. To achieve freeze-drying of eukaryotic nucleated cells they should be frozen in the absence of the currently used cryoprotectant Me2SO, this being the critical step. We tested diverse freezing conditions, employing cryoprotectants suitable to be used as excipients in the final product. Since the freeze and thaw process represent a stress for the cells, we also studied hsp 27, 70 and 90 pattern of expression in the four cell lines that comprise the vaccine. We investigated trehalose (TRE) as cell cryoprotectant, both before and after gamma irradiation. We also analyzed TRE uptake by melanoma cells and investigated the Fluid-Phase endocytosis kinetics, employing the fluorescent dye Lucifer Yellow (LYCH). We assayed different compositions of freezing media with TRE and human serum albumin (HSA). We compared samples frozen with TRE and control Me2SO, evaluating cellular integrity (trypan blue exclusion), persistence of vaccine antigens (MART-1, gp100, GD2, GD3 and HLA-A0201, FACS), proliferative capacity (MTT assay) and in case of irradiated cells, the proportion of apoptotic/necrotic cells, by Annexin-V/IP staining. TRE uptake was measured using the anthrone-sulfuric assay. Cells incubated with 0.2 M TRE after 5 h of fluid-phase endocytosis at 37 °C reached an intracellular TRE concentration that varied between 100 and 170 mM for each cell line. Optimal freezing conditions were 0.2 M TRE and 30 mg/ml HSA at − 80 °C. After freezing and subsequent thawing, the number of recovered cells, cellular integrity as well as the presence of specific antigens obtained for CSF470 frozen in TRE were not statistically different to the Me2SO control condition. Furthermore, the apoptosis/necrosis profile after gamma irradiation was similar in both cases. The non-irradiated melanoma cell lines also showed comparable proliferative capacity after both cryoprotection procedures. However, some differences were observed in the separated cell lines in terms of growth kinetics after cryopreservation. Differences in the hsps expression pattern, as detected by Western blot, were found between cell lines, suggesting a possible role for these proteins in their freezing performance. Using the TRE-freezing medium we are able to cryopreserve CSF470 vaccine in the absence of Me2SO at − 80 °C, and under these conditions we could start the vaccine freeze-drying assays.

Optimized preparation of biodegradable polymer particles encapsulating low-molecular-weight hydrophilic drugs

In the present paper, the conditions required to improve the drug loading efficiency in biodegradable polymer particles prepared using the particular technique of freezing the inner water phase of the primary emulsion before preparation of the secondary emulsion were successfully optimized. The optimal freezing temperature for the inner water phase in the primary (w1/(o1+o2)) emulsion, amount of oil soluble surfactant added to the outer o3 phase, and stirring rate and preparation time for the secondary (w1/(o1+o2)/o3) emulsion, were determined to be −15°C, 1.00g, 400rpm, and 10s, respectively. PLGA particles with a smooth spherical morphology were achieved using a sub-zero temperature of −15°C to freeze the inner water phase in the primary w1/(o1+o2) emulsion. By utilizing this procedure, PLGA particles with a drug loading efficiency of approximately 60% were prepared in the liquid–liquid system, even though a low-molecular-weight hydrophilic drug (Mw=137), isoniazid, was used.

Preserving and Using Germplasm and Dissociated Embryonic Cells for Conserving Caribbean and Pacific Coral

Coral reefs are experiencing unprecedented degradation due to human activities, and protecting specific reef habitats may not stop this decline, because the most serious threats are global (i.e., climate change), not local. However, ex situ preservation practices can provide safeguards for coral reef conservation. Specifically, modern advances in cryobiology and genome banking could secure existing species and genetic diversity until genotypes can be introduced into rehabilitated habitats. We assessed the feasibility of recovering viable sperm and embryonic cells post-thaw from two coral species, Acropora palmata and Fungia scutaria that have diffferent evolutionary histories, ecological niches and reproductive strategies. In vitro fertilization (IVF) of conspecific eggs using fresh (control) spermatozoa revealed high levels of fertilization (>90% in A. palmata; >84% in F. scutaria; P>0.05) that were unaffected by tested sperm concentrations. A solution of 10% dimethyl sulfoxide (DMSO) at cooling rates of 20 to 30°C/min most successfully cryopreserved both A. palmata and F. scutaria spermatozoa and allowed producing developing larvae in vitro. IVF success under these conditions was 65% in A. palmata and 53% in F. scutaria on particular nights; however, on subsequent nights, the same process resulted in little or no IVF success. Thus, the window for optimal freezing of high quality spermatozoa was short (∼5 h for one night each spawning cycle). Additionally, cryopreserved F. scutaria embryonic cells had∼50% post-thaw viability as measured by intact membranes. Thus, despite some differences between species, coral spermatozoa and embryonic cells are viable after low temperature (−196°C) storage, preservation and thawing. Based on these results, we have begun systematically banking coral spermatozoa and embryonic cells on a large-scale as a support approach for preserving existing bio- and genetic diversity found in reef systems.

Effect of Freezing Temperature on the Color of Frozen Salmon

New freezing methods developed with the purpose of improved product quality after thawing can sometimes be difficult to get accepted in the market. The reason for this is the formation of ice crystals that can give the product a temporary color loss and make it less appealing. We have here used microscopy to study ice crystal size as a function of freezing temperature by investigating the voids in the cell tissue left by the ice crystals. We have also investigated how freezing temperature affects the color and the visible absorption spectra of frozen salmon. Freezing temperatures previously determined to be the best for quality after thawing (-40 to -60 °C) were found to cause a substantial loss in perceived color intensity during frozen state. This illustrated the conflict between optimal freezing temperatures with respect to quality after thawing against visual appearance during frozen state. Low freezing temperatures gave many small ice crystals, increased light scattering and an increased absorption level for all wavelengths in the visible region. Increased astaxanthin concentration on the other hand would give higher absorption at 490 nm. The results showed a clear potential of using visible interactance spectroscopy to differentiate between poor product coloration due to lack of pigmentation and temporary color loss due to light scattering by ice crystal. This type of measurements could be a useful tool in the development of new freezing methods and to monitor ice crystal growth during frozen storage. It could also potentially be used by the industry to prove good product quality. In this article we have shown that freezing food products at intermediate to low temperatures (-40 to -80 °C) can result in paler color during frozen state, which could affect consumer acceptance. We have also presented a spectroscopic method that can separate between poor product color and temporary color loss due to freezing.

Three-Dimensional Numerical Study on Freezing Phase Change Heat Transfer in Biological Tissue Embedded With Two Cryoprobes

Biological tissues undergo complex phase change heat transfer processes during cryosurgery, and a theoretical model is preferable to forecast this heat experience. A mathematical model for phase change heat transfer in cryosurgery was established. In this model, a fractal treelike branched network was used to describe the complicated geometrical frame of blood vessels. The temperature distribution and ice crystal growth process in biological tissue including normal tissue and tumor embedded with two cryoprobes were numerically simulated. The effects of cooling rate, initial temperature, and distance of two cryoprobes on freezing process of tissue were also studied. The results show that the ice crystal grows more rapidly in the initial freezing stage (&lt;600 s) and then slows down in the following process, and the precooling of cryoprobes has no obvious effect on freezing rate of tissue. It also can be seen that the distance of 10 mm between two cryoprobes produces an optimal freezing effect for the tumor size (20 mm × 10 mm) in the present study compared with the distances of 6 mm and 14 mm. The numerical results are significant in providing technical reference for application of cryosurgery in clinical medicine.

Alterations in Glycopeptides Associated with Herceptin Treatment of Human Breast Carcinoma MCF-7 and T-Lymphoblastoid Cells

The therapeutic humanized monoclonal antibody IgG1 known as Herceptin® has shown remarkable antitumor effects. Although this type of therapy has increased the cancer-free survival of patients, not all tumors respond to this treatment and cancers often develop resistance to the antibody. Despite the fact that Herceptin function has been extensively studied, the precise mechanism underlying its antitumor activity still remains incompletely defined. We previously demonstrated on human breast MCF-7 carcinoma and T-lymphoblastoid CEM cells that monoclonal antibody in combination with Lipoplex consisting of Lipofectamine mixed with plasmid DNA showed a more profound effect on cancer cell viability than antibody alone. The analyses of N-glycans isolated from cancer cells showed dramatic differences in profiles when cells were exposed to Herceptin. Moreover, the investigation of glycosylated peptides from the same cancer cell models after treatment revealed further alterations in the post-translational modifications. Tandem mass spectra obtained from the samples treated confirmed the presence of a series of glycopeptides bearing characteristic oligosaccharides as described in IgG1. However some of them differed by mass differences that corresponded to peptide backbones not described previously and more of them were detected from Herceptin treated samples than from cells transfected with Heceptin/Lipoplex. The results indicate that the presence of Lipoplex prevents antibody transformation and elongates its proper function. The better understanding of the multipart changes described in the glycoconjugates could provide new insights into the mechanism by which antibody induces regression in cancers.

BUIDING MATHEMATICAL MODEL OF FREEZING HEAT TRANSFER TO DETERMINE ICE RATIO AND OPTIMAL FREEZING TEMPERATURE OF HUMID MATERIALS IN THE FIRST STAGE IN CONDITION OF FREEZE DRYING

When foods are frozen to preserve as well as perform the first stage during condition of freeze drying. The problem need to consider how to determine optimal freezing temperature, this problem is complicated. In this article presents research results of a mathematical model in describing freezing heat transfer to determine ice ratio of humid material following freezing temperature, the results received was basic to determine optimal freezing temperature, to regime technological the first stage of freeze drying and applied to calculate and design the system of freeze drying.

How do I collect and process stem cells?

How do I collect and process stem cells?

Criopreservación de espermatozoides de anchoveta peruana (Engraulis ringens)

El presente trabajo muestra una metodologia practica y de bajo costo para criopreservar espermatozoides de Engraulis ringens, con la finalidad de optimizar las tecnicas de su reproduccion en cautiverio. La investigacion fue dividida en tres etapas; la primera consistio en evaluar la toxicidad de cuatro crioprotectores; dimetilsulfoxido (ME2SO), etanol (ET), propilenglicol (PG) y glicerol (GL) a tres concentraciones molares diferentes (0,5 M; 1,0 M y 1,5 M) sobre la motilidad espermatica. Los porcentajes de motilidad de espermatozoides incubados en ME2SO fueron significativamente mayores al de los observados con los otros tres crioprotectores. En la segunda etapa se determino la tasa de congelamiento optima, utilizando el crioprotector con el que se obtuvieron los mejores resultados de motilidad (ME2SO). En este caso, los mayores porcentajes de motilidad post-descongelamiento obtenidos fueron con ME2SO a 1,5 M a tasas de congelamiento de -20 hasta -40oC min-1 (61,3 ± 7,6% y 53,8 ± 4,9% respectivamente). Por ultimo, se evaluo el efecto de la adicion de un crioaditivo no permeable en la solucion crioprotectora (vitelo de huevo de gallina, VHG), para optimizar la motilidad espermatica post-descongelamiento; sin embargo, los resultados no variaron significativamente con los controles sin VHG.

Optimizing oocyte cryopreservation for fertility preservation patients: do we mature then freeze or freeze then mature?

OBJECTIVE: For elective oocyte cryopreservation patients, there is an incentive to optimize the reproductive potential of all retrieved oocytes. The timely implementation of In Vitro Maturation (IVM) of any immature oocytes with an optimal freezing protocol is essential. We evaluated the maturation and post-thaw survival rates of immature oocytes to determine whether or not IVM should be attempted prior to or after cryopreservation.