CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/564,651, filed April 23, 2004, the contents of which are incorporated herein in their entirety.

BACKGROUND OF THE INVENTION

All publications and patent applications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

The present invention relates to an apparatus and method for maintaining low temperatures in biological materials exposed to an irradiation field. More precisely, it relates to a container and a method of irradiation using a container for reducing the variation in delivered gamma dose to biological materials contained in vessels surrounded by dry ice. The container prevents attenuation of the main gamma field during irradiation by keeping dry ice out of the path of the main gamma field.

Irradiation technology has long been used in medical sterilization. As discussed in U.S. Patent 6,384,419, biological products have validated specifications for inactivation treatment by gamma radiation. The biological products are irradiated on dry ice in containers, for example polyfoam containers, to protect product integrity. The polyfoam containers insulate the product and the commonly used pellet or riced dry ice maintain temperatures at or below an acceptable range. Considerable amounts of energy and thus heat are generated during the irradiation process, temperatures typically exceed 1O0C to 15°C above ambient. This temperature range can be deleterious to the biological product. The most common radioactive source for sterilization by radiation is gamma rays. For example, gamma rays are used to inactivate viruses, bacteria, yeasts, molds, mycoplasmas, and parasites as described in U.S. Patent 5,362,442. The sterilizing gamma rays are often produced by sources containing Cobalt 60, but may be provided by other sources.

In an irradiation system or facility, multiple containers can be loaded into an irradiation carrier for conveying the containers to a radiation source for simultaneous exposure and sterilization. Such an exemplary system is described in U.S. Patent 6,384,419. The carrier can be configured to hold, for example, fifteen containers, depending on the size of the individual containers. The carrier is then attached to a conveyor system which brings the carrier into a room containing a gamma radiation source. The carrier can be any device which will hold a number of containers, for example, a metal structure dimensioned and configured for carrying several containers. The conveyor of the irradiation system is used to transport carriers to the radiation source and can be any means by which the carriers are brought to and from the radiation source.

Many biological materials must be preserved at very low temperatures, often by using dry ice as the cooling agent. Some of these biological materials are also deactivated by gamma rays. The gamma field causes significant heat to be generated, adding to the cooling requirements.

One problem with using irradiation in sterilization of biological products is that the heat generated by the irradiation can result in degradation of the products. To maintain biological materials exposed to a gamma field, current irradiation methods surround the vessels of biological materials with pelleted or riced dry ice. In addition, the pelleted or riced dry ice tends to pull away from vessel walls as it sublimates, greatly reducing the heat transfer from the vessels during irradiation. Further, shifting of the dry ice in relation to the vessels varies the intensity of radiation received by the vessels as the vessels and/or the dry ice shifts, changing angles of the vessels in relation to the gamma field and varying the mass of dry ice in the radiation path and thus attenuating the gamma field.

Another problem with current containers used to hold vessels of biological materials and dry ice is that the vessels and dry ice tend to be loaded or conveyed with the vessels in an initial orientation, for example, upright. During or prior to irradiation the vessels may be rotated 90°_relative to their initial position, resulting in unpredictable shifting of the vessels and dry ice within the containers. For example, the conveyor system in the previously described irradiation system can be configured so as to bring the carrier holding the containers to the radiation source in an orientation where a first side of the containers receives radioactivity. The conveyor can be further configured so as to bring the carrier to the radiation source in another orientation where a second side, for example a side 90° relative to the first side, receives radioactivity. The conveyor can move the carrier to any one of several positions necessary for irradiating the containers. The conveyor can also include means for varying the time at which the carriers are held at each of the positions so as to hold any one of the several positions for a specified time. The means for varying time at which a carrier is held in position is used to control the length of exposure to the radiation source and to reduce variability in exposure. This shifting within the containers makes it impossible to accurately control or determine the dose of radiation being received by the biological materials due to varied attenuation of the irradiation field depending on the final arrangement of the vessels and dry ice. There is a need in the art for a container and method for maintaining proper orientation of vessels of biological materials and dry ice within an insulated container to more accurately determine and control the exposure of the biological materials to an irradiation field.

BRIEF SUMMARY OF THE INVENTION

The present invention is a process for using, and design of, an insulated container for maintaining low temperatures during irradiation of vessels of biological materials. A container is designed to hold vessels of biological materials and dry ice or other cooling element used to achieve and maintain low temperatures in those vessels of biological materials. The container may have channel or other shaped constraints for restricting motion of the vessels and the blocks of dry ice or other cooling element. In one embodiment, the biological material is a liquid stored in a container, such as serum (including fetal bovine serum), plasma, plasma fractions, etc. In another embodiment, the liquid contains one or more pathogens such as a virus or a bacteria. Exemplary viruses include, but are not limited to, human immunodeficiency virus, herpes virus, filovirus, circovirus, paramyxovirus, cytomegalovirus, hepatitis virus (A, B, C, and D), pox virus, toga virus, Ebstein-Barr virus and parvovirus and any combination thereof.

The shaped constraints within the container may hold the vessels between blocks of dry ice or other cooling elements such that as the dry ice sublimates, gravity maintains the dry ice in contact with the outer walls of the vessels. The shaped constraints in combination with gravity also maintain a fixed angular relationship between the source of the gamma field and the vessels and prevent attenuation of the radiation source by dry ice obstructing the path of the gamma rays.

One embodiment of the invention is a container to maintain a low temperature in a material within a vessel when exposed to an irradiation field. The container contains a thermally deformable cooling element having a substantially planar surface, and an interior surface defining a chamber having a vertical axis and a horizontal axis to house the vessel and cooling element. The surface of the cooling element engages the vessel such that thermally deforming the cooling element causes a displacement of the vessel within the chamber. The interior surface has at least one recess to engage at least a portion of the vessel. The recess limits the displacement of the vessel to a direction substantially along the vertical axis.

Another embodiment of the invention is a container for maintaining a low temperature in an assembly of at least two vertically stacked vessels of biological material when exposed to an irradiation field. The container comprises an interior surface defining a chamber to house the assembly and at least two blocks of dry ice located on either side of the assembly of vessels. The interior of the container has at least one recess that engages the assembly of vessels to keep the assembly substantially in the irradiation field and the at least two blocks of dry located such that they do not attenuate the irradiation field as it irradiates the assembly of vessels. The irradiation field is propagated substantially horizontally. The at least one recess is configured so as to permit the assembly to be displaced substantially only in a vertical direction within the chamber upon sublimation of the dry ice.

Yet another embodiment of the invention is an irradiation system comprising a biological material having a pathogen; at least one vessel to hold the biological material, the at least one vessel having a neck portion. The irradiation source includes at least one irradiation field to irradiate the biological material; a first thermally deformable cooling element having a substantially planar surface; and at least one container having an interior surface defining a chamber to house the vessel and cooling element. The surface of the cooling element is engaged with the vessel such that thermally deforming the cooling element causes a displacement of the vessel in the chamber. The interior surface of the container has a recess to engage the neck portion of the vessel so as to locate the at least one vessel substantially inside the at least one irradiation field and prevent the first cooling element from attenuating the irradiation field being received by the vessel. The recess is configured to permit the assembly to be displaced substantially only in the vertical direction within the chamber upon thermally deforming the first cooling element.

Another embodiment of the invention is a method of irradiating a biological material in a gamma irradiation field providing a vessel of biological material at a temperature ranging from about -80° C to about -500C. The method includes forming a stacked assembly comprising a first substantially planar block of dry ice, a second substantially planar block of dry ice, with the vessel disposed between with the first and second blocks of dry ice to remove heat from the biological material during the irradiation. The stacked assembly is located in an insulated container. The insulated container has an interior surface defining a chamber house the stacked assembly such that the first and second blocks of dry ice are located above and below the vessel. The interior surface of the container has at least one recess that engages at least a portion of the vessel. The container is located in the irradiating field so that the field propagates along the horizontal axis so as to substantially intersect the vessel and irradiate the biological material and the first and second blocks of ice are located such that they do not attenuate the irradiation at the vessel. The irradiating field irradiates the container so as to sublimate the first and second blocks of dry ice in a direction substantially along the vertical axis and causing translation of the vessel within the chamber, the recess limiting the translation to the direction of sublimation and maintaining the first and second blocks of ice substantially outside the irradiating field. Still another embodiment of the invention is a container for maintaining a vessel of biological material at a low temperature during irradiation comprising providing a stacked assembly comprising a first substantially planar block of dry ice, a second substantially planar block of dry ice, and at least one vessel containing the biological material at a temperature ranging from about -8O0C to about

-5O0C. The vessel is located between the first and second blocks of dry ice, with the vessel and dry ice being located within a container having an interior surface defining a chamber to house the stacked assembly. The interior surface defines a recess. The stacked assembly is located within the chamber and the recess on the interior surface engages a portion of the vessel with the to define a first position of the vessel within the chamber. The container is irradiated so as to sublimate the first and second blocks of dry ice. The sublimation of the dry ice translates the vessel to a second position within the chamber with the recess limiting the vessel to moving along the vertical axis, maintaining the vessel engaged with the first and second blocks of dry ice to maintain the biological material at a low temperature. In one embodiment, the biological material is a liquid containing one or more pathogens.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate an embodiment of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention.

FIG. IA is a side section view of a container including vessels and dry ice according to the present invention.

FIG. IB is a side section view of the container of FIG, IA after sublimation of a portion of the dry ice.

FIG. 1C is a plot of experimental test results for the temporal changes in temperature for various vessels disposed within a container according to the present invention exposed to a gamma radiation source.

FIG. 2 is a front section view of the container of FIG. IA.

FIG. 3 is a side view of a vessel for containing biological materials within the container of FIG. IA according to the present invention.

FIG. 4 is a top section view of the container of FIG. IA. FIG. 5 is a side section view of stacked containers including vessels and dry ice according to the present invention.

DETAILED DESCRIPTION

FIG. IA is a side section view and FIG. 2 is a front section view of an illustrative embodiment of a container 10 comprising a walled portion 11 and a cover 12. Container 10 can be dimensioned and configured to hold at least two vessels 20 in a vertically stacked arrangement. Alternatively, the two vessels may be horizontally next to one another. Preferably, the container 10 can be configured to hold twelve vessels 20 for containing materials stacked in three groups of four vessels each, each group of four vessels arranged in a configuration two bottles wide and two bottles high. Container 10 can be configured to hold cooling elements for cooling the biological material in vessels 20. Preferably, container 10 is configured such that an upper block of dry ice 32 rests on top of the upper row vessels of each group of four vessels 20, while each group of four vessels 20 rests on top of a lower block of dry ice 34. The lower blocks of dry ice 34 in turn rest on bottom wall 111 of walled portion 11 of container 10. As shown in FIG. 2, side blocks of dry ice 36 may be located between left and right walls 112, 113 of walled portion 11 of container 10. The blocks of dry ice 32, 34, 36 may have approximately planar surfaces in their initial state as installed within the container 10. The vessels 20 may also have approximately planar surfaces, providing for good contact between the blocks of dry ice 32, 34, 36 and the container 10 and facilitating stacking of the vessels 20.

Although the shown system has been described using blocks of dry ice as a cooling source, it will be understood by those skilled in the art that any thermally deformable cooling element could be used in place of the dry ice. In addition, while the embodiment described will house twelve vessels within the container, a container using the principles of this invention could be constructed to contain any number of vessels.

The shown system is preferably configured to reduce initial fluid temperatures to and maintains those fluid temperatures in a range of about -800C to -4O0C, and more preferably in a range of about -800C to about -5O0C, and even more preferably in a range of about -8O0C to about -700C. Moreover, the system employed with block dry ice may effectively remove heat from the vessels of biological materials exposed to doses of radiation as high as about 100 Kgy during the irradiation process. Shown in FIG. 1C is a plot of experimental test results for the temporal changes in temperature for the various vessels 20 disposed within a container 10 exposed to a gamma radiation source. As indicated, in a forty-eight hour period of radiation exposure, a container 10, as described above, maintained vessel temperatures at less than about -7O0C. Shown in FIG. 3 is an illustrative embodiment of vessel 20. Vessel 20 comprises a main body 21 and a neck 22, and can be roughly "milk bottle" shaped. Lid 221 may be located on neck 22 to retain the materials within vessel 20. Note that although the shown system is conceived as a process and design for maintaining low temperatures in biological materials during gamma irradiation, the system may be used for maintaining low temperatures in other materials using other sources of radiation. The vessels 20 can have substantially planar wall surfaces, providing for good contact between the blocks of dry ice 32, 34 and the wall surfaces of the vessels 20. While the invention may be appropriate for use with standard 250 ml, 500 ml and one liter bottles, the system is not limited to such bottles being used as vessels 20.

The vessel 20 can contain any biological fluid which may contain one or more pathogens. Examples of biological fluids include, but are not limited to, those fluids containing recombinant proteins, blood components, blood proteins, physiological buffers (e.g., saline). As used herein, "blood components" is intended to mean one or more of the components that may be separated from whole blood and include, but are not limited to, the following: serum, cellular blood components, such as red blood cells, white blood cells, and platelets; blood proteins, such as blood clotting factors, enzymes, albumin, plasminogen, fibrinogen, and immunoglobulins; and liquid blood components, such as plasma, plasma protein fraction (PPF), cryoprecipitate, plasma fractions, and plasma- containing compositions. As used herein, the term "blood protein" is intended to mean one or more of the proteins that are normally found in whole blood. Illustrative examples of blood proteins found in mammals, including humans, include, but are not limited to, the following: coagulation proteins, both vitamin K-dependent, such as Factor VH and Factor IX, and non-vitamin K-dependent, such as Factor VIII and von Willebrands factor; albumin; lipoproteins, including high density lipoproteins (HDL), low density lipoproteins (LDL), and very low density lipoproteins (VLDL); complement proteins; globulins, such as immunoglobulins IgA, IgM, IgG and IgE; digestive enizymes such as trypsin and the like. Another group of blood proteins includes Factor I (fibrinogen), Factor II (prothrombin), Factor III (tissue factor), Factor V (proaccelerin), Factor VI (accelerin), Factor VII (proconvertin, serum prothrombin conversion), Factor VIII (antihemophiliac factor A), Factor IX (antihemophiliac factor B), Factor X (Stuart-Prower factor), Factor XI (plasma thromboplastin antecedent), Factor XII (Hageman factor), Factor XIII (protransglutamidase), von Willebrands factor (vWF), Factor Ia, Factor Ha, Factor Ilia, Factor Va, Factor Via, Factor Vila, Factor Villa, Factor DCa, Factor Xa, Factor XIa, Factor XIIa, and Factor XIIIa. Yet another group of blood proteins includes proteins found inside red blood cells, such as hemoglobin and various growth factors, and derivatives of these proteins.

As shown in FIGS. IA and 2, the walled portion 11 of container 10 can form a rectangular shaped box with a back wall 115 surrounded by bottom, left, right, and top walls 111, 112, 113, and 114, respectively. Alternatively, container 10 may be circular cylindrical in shape or any other geometry that may, for example, facilitate stacking within carrier 50. Back wall 115 can define a vertical direction along axis IA — IA and bottom wall 11 can define a horizontal axis IB — IB. Container 10 may be composed of an expanded polyurethane or polystyrene, providing an excellent insulation layer. Alternatively, container 12 may be composed of other relatively rigid insulating material, or a less rigid insulating material (including air) or vacuum enclosed in rigid walls of any material well-known in the art for its ability to withstand large amounts of radiation and low temperatures. The insulating material and/or the rigid walls may be any material appropriate for such purposes that is well-known in the art.

The bottom and top walls 111, 115 define a chamber having a preferably rectangular cross- section although other geometric configurations are possible. The inner sides of bottom and top walls 111, 115 may have ribbing 116. Again referring to FIG. 2, ribbing 116 may provide a surface on which lower blocks of dry ice 34 rest. More specifically, ribbing 116 may be spaced relative to one another so as to minimize physical contact between the dry ice 34 and wall 111 thereby minimizing heat transfer between dry ice 34 and container 10. The ribbing 116 may have a further raised portion 117 spaced relative to one another so as to impede lateral movement of the upper and lower blocks of dry ice 32, 34 substantially along the horizontal axis IB — IB.

As shown in FIG. IA, cover 12 conforms to the size and shape of the opening in the walled portion 11 of container 10. The cover 12 may have a stepped portion 121 to match and fit within stepped portion 118 at the opening of walled portion 11 of container 10. The cover 12 may be attached to the walled portion 11 by any means well-known in the art including, but not limited to, bolting, screwing, an interference fit, taping, velcro, and strapping.

As shown in FIG. 4, the inner surface of the back wall 115 of the walled portion 11 of container 10 may be configured so as to define vertical channels or recesses 119 for impeding lateral movement of vessels 20 and possibly also further impeding lateral movement of upper and lower blocks of dry ice 32, 34. Similarly, the cover 12 may have vertical channels or recesses 122 with which necks 22 of vessels 20 engage. The vertical channels 122 impede lateral movement of vessels 20 along the axis IB — IB shown in FIG. 2. As shown in FIG. 2, channels 122 are preferably configured so as to define a substantially elongate oval cross-sectional area although other geometries are possible, for example rectangular. In addition, the depth of the vertical channels 119 and 122 may be used together or individually to impede lateral movement of vessels 20 within container 10. Protrusions may be built into the cover 12 or the walled portion 11 of container 10 to serve the same purpose as the vertical channels or recesses 122 and 119, respectively. The vertical channels 119 can also allow a user to locate the vessels 20 in their proper locations as they are loaded into walled portion 11 of container 10 prior to irradiation. As shown in FIG. 2, vessels 20 are preferably loaded into container 10, the upper, lower, and side blocks of dry ice 32, 34, 36 are placed around the vessels 20. Container 10 can be preferably top loaded with vessels 20 and blocks of dry ice 32, 34, 36 such that back wall 115 may be located in the horizontal plane, and the opening of walled portion 11 facing upward to receive the vessels 20 and blocks of dry ice 32, 34, 36. The vertical channels may be included in detachable walls that may be attached to the interior of the walled portion 11 and/or the cover 12. Alternatively, detachable ribbing may be selectively located within the chamber so as to form channels of variable dimensions. The detachable walls offer the advantage of allowing variations in the sizes of vessels 20 and may be attached to the interior of the walled portion 11 and/or the cover 12 by any mechanical means well known in the art including, but not limited to, screwing, bolting, quick connect, and velcro.

After loading the vessels 20 and blocks of dry ice 32, 34 36 into the walled portion 11, the cover 12 may be installed onto the opening of the walled portion 11. As shown in FIG. 5, container 10 may then be rotated 90° and placed within stacks of other containers 10 in a carrier 50. In this position, the vessels 20 on the lower rows rest on the lower blocks of dry ice 34, while the upper blocks of dry ice 32 rest on the upper rows of vessels 20. This arrangement provides large areas of contact between the blocks of dry ice 32, 34 and the vessels 20, providing improved heat transfer compared to pelleted or riced dry ice packed around the vessels 20.

Referring to FIG. 5, the stacked containers 10 may be exposed to a radiation field or fields 40, with rays entering from the direction of the cover 12 and/or the back wall of walled portion 11. The radiation field 40 generates heat within the containers 10. Moreover, heat generated in vessels 20 is transferred to ice 32, 34 and 36. This heat, along with the ambient heat absorbed by the containers, causes the blocks of dry ice 32, 34, 36 to sublimate. As the blocks of dry ice 32, 34 sublimate, they become smaller, as shown in FIG. IB. As lower blocks of ice 34 become smaller, the upper surface of the ice becomes lower, resulting in the vessels 20 resting upon blocks 34 following to lower elevations as the blocks 34 sublimate. Vertical channels 119 and/or 122 guide the vessels 20 as their elevation changes, maintaining physical contact between vessels 20 and blocks of dry ice 32, 34. In addition, vessels 20 maintain the same angular relationship to the radiation sources due to the vertical channels 119 and/or 122 impeding movement of the vessels 20 in any direction other than vertical. The blocks of dry ice 32, 34 are also maintained above and below the vessels, respectively, such that they do not interfere with the radiation source. This allows for a relatively constant irradiation of the vessels 20. Ribbing 116, 117 may further facilitate heat transfer between vessels 20 and ice 32, 34 and 36 by providing an interstice to which hot sublimated gases may escape away from the vessels 20 and ice 32, 34, and 36.

It will be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing an enabling disclosure of the invention. The foregoing disclosure is not intended to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.