Method and apparatus for preserving biological materials

Claim 2

A process for preserving biological materials by freezing comprising the steps of: cooling the biological material to a temperature equal to or minimally warmer than the freezing temperature of the material; chilling the environment surrounding the biological material rapidly to a preselected temperature substantially colder than the freezing temperature of the material to initiate phase change of the material; warming the environment surrounding the biological material from said preselected temperature to a temperature equal to or minimally cooler than the freezing temperature of the material during removal of the heat of fusion of the material; and cooling the environment surrounding the biological material at a substantially linear preselected rate of temperature change to a preselected end temperature.

Claim 3

The process according to claim 1, the step of cooling the biological material comprising the substeps of: introducing a refrigerant to the environment surrounding the biological material in intermittent bursts; sensing the temperature of the biological material; and terminating introduction of the refrigerant when the temperature of the biological material is approximately but not less than the freezing temperature of the material.

Claim 4

The process according to claim 1, the step of chilling the environment comprising the substeps of: triggering a continuous flow of refrigerant to the environment surrounding the biological material; sensing the temperature of the environment; and terminating the flow of refrigerant when the environment reaches the preselected temperature.

Claim 5

The process according to claim 1, the step of warming the environment comprising the substeps of: introducing a flow of warm air to the environment surrounding the biological material; sensing the temperature of the environment; and terminating the flow of warm air when the environment reaches a temperature approximately but not higher than the freezing temperature of the biological material.

Claim 6

The process according to claim 1, the step of cooling the environment comprising the substeps of: introducing a refrigerant to the environment in intermittent bursts; and sensing the temperature of the environment.

Claim 7

The process according to claim 1 further comprising the step of intermittantly recording the temperature of the biological material and the temperature of the surrounding environment during the process.

Claim 8

A process for preserving biological materials by freezing comprising the steps of: cooling the biological material at a substantially linear preselected rate of temperature change to approximately but not less than the freezing temperature of the material; chilling the environment surrounding the biological material rapidly to a preselected temperature in the range of -20° C to -100° C; warming the environment to a temperature approximately but not more than the freezing temperature of the biological material; and cooling the environment at a preselected substantially linear rate of temperature change to a preselected temperature in the range of -20° C to -100° C.

Claim 9

A process for preserving biological materials by freezing comprising the steps of: cooling the biological material at a substantially linear preselected rate of temperature change to approximately but not less than the freezing temperature of the material; chilling the environment surrounding the biological material rapidly to a preselected temperature in the range of -20° C to -100° C; warming the environment to a temperature approximately but not more than the freezing temperature of the biological material; and cooling the environment at a preselected substantially linear rate of temperature change to a preselected temperature in the range of -20° C to -100° C.

Claim 10

The process according to claim 7 wherein the rate of cooling the biological material and the rate of cooling the environment are independently selectively in the range of 0.5° C per minute to 30° C per minute.

Claim 11

A process for preserving biological materials by freezing comprising the steps of: placing the biological material in a cooling chamber; introducing a refrigerant to the cooling chamber in intermittant bursts to lower the temperature of the biological material; sensing the temperature of the biological material; triggering a continuous burst of refrigerant into the cooling chamber when the biological material is at or minimally warmer than freezing temperature; sensing the temperature of the chamber; terminating the flow of refrigerant into the chamber when the chamber temperature reaches a preselected temperature substantially lower than the freezing temperature of the biological material and prior to completion of removal of the heat of fusion of the biological material; introducing a flow of warm air to the chamber when flow of refrigerant is terminated; terminating the flow of warm air when the chamber temperature is at or minimally lower than the freezing temperature of the biological material; and reintroducing intermittant bursts of refrigerant to the cooling chamber to substantially linearly lower the temperature of the biological material to a preselected end temperature.

Claim 12

A process for preserving biological materials by freezing comprising the steps of: placing the biological material in a cooling chamber; introducing a refrigerant to the cooling chamber in intermittant bursts to lower the temperature of the biological material; sensing the temperature of the biological material; triggering a continuous burst of refrigerant into the cooling chamber when the biological material is at or minimally warmer than freezing temperature; sensing the temperature of the chamber; terminating the flow of refrigerant into the chamber when the chamber temperature reaches a preselected temperature substantially lower than the freezing temperature of the biological material and prior to completion of removal of the heat of fusion of the biological material; introducing a flow of warm air to the chamber when flow of refrigerant is terminated; terminating the flow of warm air when the chamber temperature is at or minimally lower than the freezing temperature of the biological material; and reintroducing intermittant bursts of refrigerant to the cooling chamber to substantially linearly lower the temperature of the biological material to a preselected end temperature.

Claim 13

Apparatus for preserving biological materials by freezing comprising in combination: a cooling chamber and a refrigerant source interconnected by a transfer line having a valve disposed therein; means for continuously circulating the air in said chamber; a first thermocouple for sensing the temperature of a sample of the biological material; a second thermocouple for sensing the temperature of the cooling chamber; means for warming the air in said chamber; and circuit means for receiving electrical signals from said first and second thermocouples and for transmitting signals to said valve and to said warming means, said circuit means being operable to sequentially: i. intermittantly open and close said valve to cool the biological material in the liquid phase to a temperature approximately but not warmer than the freezing temperature of the material; ii. open said valve to rapidly chill said chamber to a preselected temperature substantially colder than the freezing temperature of the material; iii. close said valve and energize said warming means; iv. deenergize said warming means when said chamber returns to approximately but not higher than the freezing temperature of the material; and v. intermittantly open and close said valve to cool the biological material in the solid phase at a substantially linear rate of temperature change to an end temperature.

Claim 14

Apparatus for preserving biological materials by freezing comprising in combination: a cooling chamber and a refrigerant source interconnected by a transfer line having a valve disposed therein; means for continuously circulating the air in said chamber; a first thermocouple for sensing the temperature of a sample of the biological material; a second thermocouple for sensing the temperature of the cooling chamber; means for warming the air in said chamber; and circuit means for receiving electrical signals from said first and second thermocouples and for transmitting signals to said valve and to said warming means, said circuit means being operable to sequentially: i. intermittantly open and close said valve to cool the biological material in the liquid phase to a temperature approximately but not warmer than the freezing temperature of the material; ii. open said valve to rapidly chill said chamber to a preselected temperature substantially colder than the freezing temperature of the material; iii. close said valve and energize said warming means; iv. deenergize said warming means when said chamber returns to approximately but not higher than the freezing temperature of the material; and v. intermittantly open and close said valve to cool the biological material in the solid phase at a substantially linear rate of temperature change to an end temperature.

Claim 15

The apparatus defined in claim 10 further comprising means for securing said first thermocouple at approximately the geometric center of the sample of biological material.

Claim 16

The apparatus defined in claim 10 wherein said circulating means comprises an air inlet passage to and an air outlet passage from said chamber, said passages being interconnected by a duct to form a continuous path of air flow, said duct having a blower means disposed therein for causing a flow of air along said path.

Claim 17

The apparatus defined in claim 12, said transfer line being connected to said chamber via a refrigerant inlet passage in said chamber, said refrigerant inlet passage being aligned to introduce refrigerant into said chamber along a path transverse to the path of air flow through said air inlet passage.

Claim 18

The apparatus defined in claim 13 further comprising means disposed in said chamber for interrupting a direct flow of refrigerant or air from said passages to the biological material or the sample thereof.

Claim 19

The apparatus defined in claim 10, said circuit means including a plurality of independently variable means operable to select respectively the cooling rate in the liquid phase, the liquid phase final temperature, the preselected chill temperature, the deenergization of warming means temperature, the end temperature and the cooling rate in the solid phase.

Claim 20

The apparatus defined in claim 15 wherein said variable means have respective ranges of 0.5° C per minute to 30° C per minute, 0° C to -25° C, -20° C to -100° C, 0° C to -40° C and 0.5° C per minute to 30° C per minute.