Systems to Preserve Living Tissue

The present invention relates to methods and systems to maximize the probability of successfully preserving living tissue severed from its host living system.

The literature abounds with writings describing the re-implantation of severed appendages and the, albeit presently ephemeral, transplantation of cadaveric or homologous allografts, including allografts of skin, corneas, some internal organs (e.g., kidney, pancreas, lung and heart) plus nesidiogenesis of vital tissues. In all of these situations there exists the need to maximize the likelihood of a successful (i.e., functional) graft. The success is decisively related to many factors, including the time and incipient conditions, during which the appendage or tissue is severed from its host, before re-implantation. Frequently preservation may be particularly difficult following amputation as a consequence of traumatic catastrophic accident. In particular, failure to optimize the quality of the post-traumatic milieu creates an unnecessary rate-limiting obstruction to successful re-implantation. The present method and system provide both a superior milieu in the postpartum period, plus improved thermal and mechanical stability.

Accordingly, it is a principal object of the present invention to provide a novel method and system to preserve living tissue or tissues severed from its host.

Another object is to provide a method and system that is particularly useful to preserve human legs and arms that are catastrophically severed from the host.

Still another object is to enable improved preservation of germinal tissues, cloned cells and organs from selected animals, bacteria or cell lines.

These and still further objects are addressed hereinafter.

The foregoing objects are achieved, generally, in a method (and system) for preserving tissue that has been severed from its host, that comprises depositing the tissue in a bag containing a sterile liquid; introducing to the liquid within the bag a biscuit containing a pH buffer and electrolyte to maintain and preserve a quasistatic biochemical environment most favorable to thriving tissue or cells; and maintaining the liquid at a temperature favorable to survival of the tissue.

The invention is hereafter described with reference to the accompanying drawing in which:

FIG. 1 is an isometric view of a bag and other elements of a system to preserve living tissue, cells and the like that have been severed from their host;

FIG. 2 shows the bag of FIG. 1 (slightly reduced in size) with a portion of a finger contained therein; and

FIG. 3 shows isometrically and partially cutaway, an outer container with the bag (reduced in size), the finger and other system components within.

Turning now to the figures, the system labeled 101 in FIG. 3 serves to preserve living tissue (e.g., the severed finger shown at 7 in FIG. 2) that has been severed from its host. The system 101 includes a gas-permeable bag 9 to receive the tissue and a liquid solution 5 (e.g., water); the bag 9 provides a sterile environment for both the tissue and the solution during storage thereof. A T-shaped biscuit 6 is disposed within the bag, surrounded by the liquid 5. The biscuit 6 contains an electrolyte (e.g. potassium bicarbonate, potassium chloride, potassium dihydrogen phosphate, calcium salts) to maintain the cellular internal environment of the tissue and it contains, as well, a pH buffer (e.g., sodium and potassium bicarbonate). The T-shape form of biscuit results in a more uniform dissolution thereof within the solution, than would a spheroidal or pellet shape biscuit.

The bag 9 is placed into an insulated box 8 containing ice 11 to maintain the temperature of the solution 5 at between about 2.degree. C. and 20.degree. C. It will be appreciated that the appropriate temperature range can be maintained by refrigeration or other known mechanisms and, in addition, presently available microprocessor controls can be employed.

The bag 9 ideally is made of a material that is both mechanically and chemically stable and, for the system shown, is permeable both to O.sub.2 and CO.sub.2. A polyethylene and silicone composite can be employed to provide that mechanical stability and permeability, the polyethylene giving mechanical stability and the silicone giving permeability.

The molecular oxygen is needed to maximize the probability of the tissue to survive and, in addition, it permits some ingredients (e.g., coenzymes and antibiotics) in the biscuit 6 to function properly. The carbon dioxide is a by-product of tissue metabolism. Of course, the molecular oxygen can be provided by other mechanisms (e.g., O.sub.2 cartridges, gas-evolving chemical reactions or electrical anodic liberation of oxygen). The carbon dioxide can be absorbed by other mechanisms (e.g., gascolators, chemisorbents).

To construct the bag 9, a back sheet 1 is attached to a front sheet 2 by a seal 3 disposed at the periphery of the sheets 1 and 2. A latch mechanism 4 is used to seal the bag 9 once the entire contents are present (i.e., the solution, the biscuit and the severed appendage). The seal is broken only when surgical re-implantation is imminent.

In addition to an electrolyte and a pH buffer, usually the biscuit will contain one or more of the following: an energy source (e.g., glucose and fructose); a high-energy phosphate compound (e.g., ATP and creatine phosphate); a metabolite (e.g., coenzymes and aminoacids); a material to remove toxic debris (activated charcoal and heavy metal chelators); a material to slow down tissue destruction (e.g., protease and peptidase inhibitors); a material to inactivate bacteria and viruses (e.g., antibiotics and methylene blue); a material to enhance survival in a cold environment (e.g., glycerol); a material to enhance survival during oxidative stress (e.g., glutathione and selenium, superoxide dismutase, carotene); and a material to enhance wound healing (e.g., zinc oxide).

Modification of the invention herein disclosed will occur to persons skilled in the art and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.