29pm1-A-1 Examination of cryoprotectant-free cryopreservation by flash cell freezing : Influence of cooling rate on cell viability

2015 ◽  
Vol 2015.7 (0) ◽  
pp. _29pm1-A-1-_29pm1-A-1
Author(s):  
Masato Shinose ◽  
Yoshitake Akiyama
Keyword(s):  
Cell Viability ◽  
Cooling Rate ◽  
Cell Freezing

scholarly journals Cryopreservation of midbrain dopaminergic neural cells differentiated from human embryonic stem cells

2020 ◽  
Author(s):  
Nicola J. Drummond ◽  
Karamjit Singh Dolt ◽  
Maurice A. Canham ◽  
Peter Kilbride ◽  
G. John Morris ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cell Viability ◽  
Cooling Rate ◽  
Embryonic Stem ◽  
Precursor Cells ◽  
Neural Precursor Cells ◽  
Neural Precursor ◽  
List Type ◽  
Clinical Grade ◽  
Better Than

AbstractRecent advancements in protocols to differentiate human pluripotent stem cells into midbrain dopaminergic (mDA) neurons has improved the ability to model Parkinson’s disease (PD) in a dish, and has provided a scalable source of donor cells for emerging PD cell replacement therapy (CRT). However, to facilitate reproducibility, collaboration, and clinical trials it would be highly beneficial to cryopreserve committed mDA neural precursors cells in a ready-to-use format. In terms of cell manufacturing for PD CRT trials, a cryopreserved transplantation-ready mDA cell product would provide a critical opportunity for quality control, efficacy testing, and safety assessments. To address this challenge, we have compared six (6) different clinical-grade cryopreservation media and different freezing conditions for mDA neural precursor cells differentiated from two human embryonic stem cell (ESC) lines, MasterShef7 and RC17. Significant differences in cell viability were observed at 24h post-thawing, but no differences were observed immediately upon thawing. This highlights the need to check cell viability over the first 24h after thawing, and that viability of freshly thawed cells is insufficient to gauge the success of a cryopreservation protocol. Considerable apoptosis occurs in the first 24h post-thawing, and significant differences between cryopreservation procedures were only revealed during this time period. The presence of ROCK inhibitors improved cell viability at 24h for all conditions tested. A faster cooling rate of 1-2°C/min was significantly better than 0.5°C/min for all conditions tested, while rapid thawing at 37°C was not always superior to slow thawing at 4°C. Indeed, the optimal cryopreservation and thawing conditions in this study, as determined by 24h post-thaw viability, were cells frozen in PSC Cryopreservation medium at a cooling rate of 1°C/min and slow thawing at 4°C. These conditions permitted recovery of 60%-70% live cells at 24h with respect to the starting number of cryopreserved cells. Importantly, cryopreservation of mDA neural precursor cells did not alter their potential to resume differentiation into mDA neurons.HighlightsFirst systematic comparison of multiple clinical-grade cryopreservation media for human ESC-derived mDA neural precursor cellsDifferences in cell viability were observed at 24h after thawing, but not immediately upon thawingCooling rates of 1°C/min or 2°C/min were significantly better than 0.5°C/min for all cryopreservation conditions testedA slow thawing condition at 4°C was significantly better than quick thawing at 37°C for cells frozen in PSC Cryopreservation mediumCryopreservation of mDA cells does not significantly alter their potential to differentiate into mDA neurons

Directional Solidification Stage With Dynamically Variable Speeds: Assessment of Cell Viability After Interrupted Cooling

2011 ◽  
Author(s):  
Josh LaFountain ◽  
Ram V. Devireddy
Keyword(s):  
Cell Viability ◽  
Directional Solidification ◽  
Cooling Rate ◽  
Room Temperature ◽  
Adult Stem Cells ◽  
Membrane Integrity ◽  
Freezing Method ◽  
A Cell ◽  
Directional Freezing ◽  
Solidification Stage

A two-step directional freezing method was utilized to assess the membrane integrity in frozen/thawed adult stem cells (ASCs). Using a custom built directional solidification stage (DSS) we determined that cells cooled at two different rates (i.e., a slower rate between room temperature, 27 °C and −10 °C and a higher rate between −10 °C and −60 °C) experienced significantly higher loss of cell viability when compared with those cooled at a single and uniform slower cooling rate between 27 °C and −60 °C. Specifically, the cells cooled using the two-step freezing method exhibited a post-thaw cell viability of ∼17% while those that were cooled using the traditional method exhibited a cell viability of 49%. We also found that varying the cooling rate between 27 °C and −10 °C did not significantly affect the post-thaw viability of ASCs, suggesting that they are not susceptible to supra-zero cooling injury.

Effects of cooling rate on the mechanical properties of dual phase treated vanadium steels

1983 ◽  
Vol 41 ◽  
pp. 220-221
Author(s):  
L.J. Chen ◽  
H.C. Cheng ◽  
J.R. Gong ◽  
J.G. Yang
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Automobile Industry ◽  
High Strength ◽  
Weight Percent ◽  
Low Alloy Steels ◽  
Dual Phase ◽  
Resource Requirement ◽  
Alloy Steels ◽  
Potential Weight

For fuel savings as well as energy and resource requirement, high strength low alloy steels (HSLA) are of particular interest to automobile industry because of the potential weight reduction which can be achieved by using thinner section of these steels to carry the same load and thus to improve the fuel mileage. Dual phase treatment has been utilized to obtain superior strength and ductility combinations compared to the HSLA of identical composition. Recently, cooling rate following heat treatment was found to be important to the tensile properties of the dual phase steels. In this paper, we report the results of the investigation of cooling rate on the microstructures and mechanical properties of several vanadium HSLA steels.The steels with composition (in weight percent) listed below were supplied by China Steel Corporation: 1. low V steel (0.11C, 0.65Si, 1.63Mn, 0.015P, 0.008S, 0.084Aℓ, 0.004V), 2. 0.059V steel (0.13C, 0.62S1, 1.59Mn, 0.012P, 0.008S, 0.065Aℓ, 0.059V), 3. 0.10V steel (0.11C, 0.58Si, 1.58Mn, 0.017P, 0.008S, 0.068Aℓ, 0.10V).

Suppression of γ’ Precipitation in a Laser-Melted Nickel-Base Alloy

1977 ◽  
Vol 35 ◽  
pp. 270-271
Author(s):  
J. M. Walsh ◽  
J. C. Whittles ◽  
B. H. Kear ◽  
E. M. Breinan
Keyword(s):  
Cooling Rate ◽  
Base Alloy ◽  
Material Surface ◽  
Intimate Contact ◽  
Absorbed Power ◽  
Perfect Contact ◽  
Nickel Base ◽  
Rapidly Solidified ◽  
Limiting Case ◽  
The Heat Transfer Coefficient

Conventionally cast γ’ precipitation hardened nickel-base superalloys possess well-defined dendritic structures and normally exhibit pronounced segregation. Splat quenched, or rapidly solidified alloys, on the other hand, show little or no evidence for phase decomposition and markedly reduced segregation. In what follows, it is shown that comparable results have been obtained in superalloys processed by the LASERGLAZE™ method.In laser glazing, a sharply focused laser beam is traversed across the material surface at a rate that induces surface localized melting, while avoiding significant surface vaporization. Under these conditions, computations of the average cooling rate can be made with confidence, since intimate contact between the melt and the self-substrate ensures that the heat transfer coefficient is reproducibly constant (h=∞ for perfect contact) in contrast to the variable h characteristic of splat quenching. Results of such computations for pure nickel are presented in Fig. 1, which shows that there is a maximum cooling rate for a given absorbed power density, corresponding to the limiting case in which melt depth approaches zero.

Voids in Quenched Nickel

1968 ◽  
Vol 26 ◽  
pp. 266-267
Author(s):  
J. J. Laidler
Keyword(s):  
Electron Beam ◽  
Ambient Temperature ◽  
Cooling Rate ◽  
Three Dimensional ◽  
Cooling Curve ◽  
Polycrystalline Nickel ◽  
Quenching Temperature ◽  
Long Tail ◽  
Diffusion Pump

The presence of three-dimensional voids in quenched metals has long been suspected, and voids have indeed been observed directly in a number of metals. These include aluminum, platinum, and copper, silver and gold. Attempts at the production of observable quenched-in defects in nickel have been generally unsuccessful, so the present work was initiated in order to establish the conditions under which such defects may be formed.Electron beam zone-melted polycrystalline nickel foils, 99.997% pure, were quenched from 1420°C in an evacuated chamber into a bath containing a silicone diffusion pump fluid . The pressure in the chamber at the quenching temperature was less than 10-5 Torr . With an oil quench such as this, the cooling rate is approximately 5,000°C/second above 400°C; below 400°C, the cooling curve has a long tail. Therefore, the quenched specimens are aged in place for several seconds at a temperature which continuously approaches the ambient temperature of the system.

Microstructures of Laser Processed Fe-Cr Surface Alloys

1981 ◽  
Vol 39 ◽  
pp. 328-329
Author(s):  
P. A. Molian ◽  
K. H. Khan ◽  
W. E. Wood
Keyword(s):  
Cooling Rate ◽  
Pure Iron ◽  
Continuous Wave ◽  
Laser Surface ◽  
Material Surface ◽  
Constitution Diagram ◽  
Incident Power ◽  
Surface Alloying ◽  
Laser Surface Alloying ◽  
Spot Diameter

In recent years, the effects of chromium on the transformation characteristics of pure iron and the structures produced thereby have been extensively studied as a function of cooling rate. In this paper, we present TEM observations made on specimens of Fe-10% Cr and Fe-20% Cr alloys produced through laser surface alloying process with an estimated cooling rate of 8.8 x 104°C/sec. These two chromium levels were selected in order to study their phase transformation characteristics which are dissimilar in the two cases as predicted by the constitution diagram. Pure iron (C<0.01%, Si<0.01%, Mn<0.01%, S=0.003%, P=0.008%) was electrodeposited with chromium to the thicknesses of 40 and 70μm and then vacuum degassed at 400°F to remove the hydrogen formed during electroplating. Laser surface alloying of chromium into the iron substrate was then performed employing a continuous wave CO2 laser operated at an incident power of 1200 watts. The laser beam, defocussed to a spot diameter of 0.25mm, scanned the material surface at a rate of 30mm/sec, (70 ipm).

Cytoprotective Effect of Tocotrienol-Rich Fraction and α-Tocopherol Vitamin E Isoforms Against Glutamate-Induced Cell Death in Neuronal Cells

2014 ◽  
Vol 84 (3-4) ◽  
pp. 0140-0151 ◽  
Author(s):  
Thilaga Rati Selvaraju ◽  
Huzwah Khaza’ai ◽  
Sharmili Vidyadaran ◽  
Mohd Sokhini Abd Mutalib ◽  
Vasudevan Ramachandran ◽  
...  
Keyword(s):  
Vitamin E ◽  
Cell Viability ◽  
Neuronal Cells ◽  
Positive Control ◽  
Post Treatment ◽  
Mitochondrial Activity ◽  
Before And After ◽  
Pre Treatment ◽  
Tocotrienol Rich Fraction ◽  
Major Mediator

Glutamate is the major mediator of excitatory signals in the mammalian central nervous system. Extreme amounts of glutamate in the extracellular spaces can lead to numerous neurodegenerative diseases. We aimed to clarify the potential of the following vitamin E isomers, tocotrienol-rich fraction (TRF) and α-tocopherol (α-TCP), as potent neuroprotective agents against glutamate-induced injury in neuronal SK-N-SH cells. Cells were treated before and after glutamate injury (pre- and post-treatment, respectively) with 100 - 300 ng/ml TRF/α-TCP. Exposure to 120 mM glutamate significantly reduced cell viability to 76 % and 79 % in the pre- and post-treatment studies, respectively; however, pre- and post-treatment with TRF/α-TCP attenuated the cytotoxic effect of glutamate. Compared to the positive control (glutamate-injured cells not treated with TRF/α-TCP), pre-treatment with 100, 200, and 300 ng/ml TRF significantly improved cell viability following glutamate injury to 95.2 %, 95.0 %, and 95.6 %, respectively (p < 0.05).The isomers not only conferred neuroprotection by enhancing mitochondrial activity and depleting free radical production, but also increased cell viability and recovery upon glutamate insult. Our results suggest that vitamin E has potent antioxidant potential for protecting against glutamate injury and recovering glutamate-injured neuronal cells. Our findings also indicate that both TRF and α-TCP could play key roles as anti-apoptotic agents with neuroprotective properties.

Sign in / Sign up

Export Citation Format

Share Document