Freezing Of Biological Materials Research Articles

A Mathematical Analysis of Directional Solidification of Aqueous Solutions

Abstract Horizontal directional solidification techniques have been broadly utilized for the freezing of biological matter under conditions in which the freezing rate during solidification must be controlled and known. Directional solidification is used for diverse applications such as fundamental research on freezing of biological materials, cryopreservation of biological matter, and tissue engineering. This study is motivated by our intent to use directional solidification as a simplified model for the study of three-dimensional (3D) cryoprinting. In evaluating directional solidification in the context of 3D cryoprinting, we realized that current mathematical models of directional solidification are not adequately representative for this purpose, because they are simplified and one-dimensional (1D). Here, we introduce an experimentally verified and more representative two-dimensional (2D) mathematical model of directional solidification that can aid in the fundamental study of freezing of biological matter, in particular during 3D cryoprinting. The mathematical model was used to develop correlations between the freezing rates that a layer of an aqueous solution experiences during directional solidification and the various design parameters such as thickness of the sample and temperature gradients in the substrate. Results show that the freezing rates can be higher than those suggested by the previously used simplified 1D mathematical models. The results can be used for developing simplified models of 3D cryoprinting. In addition, the results suggest that many experimental studies on directional solidification of aqueous solutions and biological matter may require readjustment of analysis, in view of these findings.

4. 生体食品の凍結における諸機序とミクロ伝熱(セミナー : 生物資源の保存)

4. 生体食品の凍結における諸機序とミクロ伝熱(セミナー : 生物資源の保存)

The prospects of the application of gases and gas hydrates in cryopreservation

In the present review, we attempt to evaluate the known properties of gas hydrates and gases that form them from the point of view of the mechanisms of cryoinjury and cryoprotection, to consider the publications on the freezing of biological materials in the presence of inert gases, and to assess the prospects of development in this field. For this purpose, we searched for information on the physical properties of gases and gas hydrates, compared the processes that occur during the formation of gas hydrates and water ice, and analyzed the effects of the formation and growth of gas hydrates on the structures of biological objects. We prepared a short review on the biological effects of xenon, krypton, argon, carbon dioxide, hydrogen sulfide, and carbon monoxide with emphasis on hypothermal conditions and the probable application of these properties in cryopreservation technology. The descriptions of the existing experiments on cryopreservation of biological objects using gases are analyzed. Based on the information we found, the most promising directions of work in the field of cryopreservation of biological objects using gases are outlined; potential problems in this field are anticipated.

Dynamic and sub-ambient thermal transition relationships in water–sucrose solutions

This work was undertaken to investigate thermal and dynamic transitions observed in the temperature range close to the bulk ice melting temperature in sucrose solutions. Measurements of thermal (differential calorimetry) and dynamic (neutron scattering) properties were compared in order to give a physical interpretation of the thermal transitions observed during the thawing of amorphous sucrose solutions. In fact, the freezing of biological material leads to the distinction between different pools of water: bulk water which becomes ice after freezing, unfrozen water trapped in the glassy matrix or close to the interface of solutes can be considered, and finally freezable confined water with a lower melting point than bulk water and with properties depending on both the ice presence and the microstructure of the material. The transition temperatures such as glass transition or melting are dependent on the freezing protocol used and examples of annealing effects are presented, in order to underline the necessity of a good temperature control during freezing for the study of biological material with freezable water.

S0601-1-5 食品凍結に及ぼす超音波照射の影響(食と熱工学(1))

A method to actively controlling crystallization is one of promising technique for cryopreservation. The object of this paper is to study the effects of ultrasonic irradiation on ice formation during freezing of biological materials with supercooling. In the experiments, agar gel was frozen under irradiation of ultrasound at frequency of 28kHz. The results suggest that higher degree of ultrasonic irradiation can release supercooling state, but also lower degree of ultrasonic irradiation would enhance supercooling dgree during freezing process. It was also found that the size of ice crystal decreased with increasing ultrasonic power under constant supercoling degree. The method to setting sample as possible as near the ultrasonic horn was useful for reducing ice crystal size.

Ice-front propagation monitoring in tissue by the use of visible-light spectroscopy

For demonstrating that visible-light spectroscopy can be used for ice-front detection within freezing tissue, proton magnetic resonance images were correlated to time-evolving transmittance spectra as an ice front progressed across a tissue sample. The experimental apparatus was designed to be compatible with magnetic resonance imaging, to produce one-dimensional freezing, and to allow both reflectance and transillumination emitter-detector configurations about a normally progressing planar ice front in chicken muscle. This demonstration has potentially important medical applications in cryopreservation (freezing of biological materials for preservation) and cryosurgery (destruction of tissue by freezing).

Modifications to the paper ‘On defining the thermal history of cells during the freezing of biological materials’

SUMMARYSome of the figures published in the original paper Bald & Crowley (1979) have been modified to include a corrected value for the thermal conductivity of ice.

On defining the thermal history of cells during the freezing of biological materials

An explicit numerical finite difference scheme for defining the thermal history of a cell or group of cells contained within a biological sample of prescribed shape is described. Solutions are presented for three different cases of freezing of biological materials prior to microscopic examination. It is concluded that a surface boundary condition must be specified in any experiment before cell ultrastructure or viability can be related to thermal history or cooling rate.

A new method for controlled freezing of biological material

A new method for controlled freezing of biological material

Apparatus for deep freezing of biological material with programmed control.

Apparatus for deep freezing of biological material with programmed control.