Tissue pooling process

Details Tissue pooling process Tissue pooling process

1999-09-07

2003-09-02

Thornton, Krisanne (Department: 1744)

Chemical apparatus and process disinfecting, deodorizing, preser

Process disinfecting, preserving, deodorizing, or sterilizing

Using disinfecting or sterilizing substance

C422S028000, C422S032000, C422S039000, C422S040000, C435S001100, C435S001200

Reexamination Certificate

active

06613278

ABSTRACT:

2.0 BACKGROUND OF THE INVENTION
2.1 FIELD OF THE INVENTION
This invention is a novel method for pooling tissue. In one embodiment, the process includes the steps of perfusion of a porous implant which achieves efficient interpenetration of desired factors into the pores or channels of the implant, cleaning of the implant, efficient passivation of the implant (inactivation of pathogens, microorganisms, cells, viruses and the like and reduction in antigenicity thereof), and the novel implant produced by such treatment. This invention also provides a method for ex vivo treatment of diseased tissue, which may be re-implanted, free of diseased tissue.
2.2 DESCRIPTION OF KNOWN PROCEDURES FOR IMPLANT TREATMENT
As used in this disclosure, the term “implant” refers to any material the implantation of which into a human or an animal is considered to be beneficial. Accordingly, the implant may be tissue-derived material, such as bone, skin, and the like, or it may be a metallic or synthetic material having an internal structure that may require cleaning or sterilization. The implant may comprise autograft tissue, allograft tissue, xenograft tissue or combinations thereof, and in the case of mineralized tissues, such as bone, the implant may comprise mineralized tissue, partially demineralized tissue, completely demineralized tissue, and combinations thereof. Bearing this definition in mind, it will be apparent that procedures have been described in the art for treatment of implants to either clean such implant, inactivate contaminating microorganisms or cells that may be present in or on such implant, or to infuse the implant with desirable factors. This section of the disclosure discusses several known methods for achieving one or more of these results, in order to more clearly and definitively set forth that which has been invented, and which is disclosed and claimed as novel and inventive, as defined by the claims appended hereto.
European Patent Application No. EP 0 424 159 (Osteotech)—“Aseptic Processing of Allograft Bone and Tissue,” (published Apr. 24, 1991, based on a U.S. Priority application filed Oct. 19, 1989), is an extremely general disclosure relating to aseptic processing of allograft bone and tissue.
U.S. Pat. No. 5,333,626 (Cryolife)—“Preparation of Bone for Transplantation”, relates to a method of preparing bone for transplantation by maintaining the internal matrix of the bone to be implanted, preferably at high pressure, in the presence of a decontaminating agent, preferably polyvinyl pyrrolidine-iodine (PVP-1) optionally in the presence of a detergent, in solution. The “high pressure” feature of this patent is described at column 5, lines 10-31: “High pressure washing conditions should provide a force sufficient to drive the cleaning solution into internal matrix of the bone. Such high pressure washing conditions include, for example, vigorous agitation, such as with a paint can shaker, or high pressure lavage such as with a high pressure liquid jet stream. . . The pressure of the liquid jet stream is preferably 100 to 3,000 psi and most preferably 500 to 1,500 psi.” However, the patent does not disclose or suggest exposure of an implant to an oscillating atmospheric pressure, the referenced patent requires pressures significantly higher than those required according to the present invention, and it is only applicable to bone, while the present invention is applicable to bone or soft tissue. In addition, the claimed process requires approximately 1-2 days to complete.
U.S. Pat. No. 5,513,662 (Osteotech)—“Preparation of Bone for Transplantation”, relates to a method of preparing bone for transplantation in which the internal matrix of the bone is maintained at a pressure below one atmosphere. It is disclosed (column 10, lines 13-19) that “optimum times for maintaining pressure below ambient are generally in the range of 30 to 60 minutes but can be determined for each application by monitoring progress of blood and lipid extraction (see Example 10).” It is further disclosed that generally use of gas pressure below ambient for less than two minutes will be ineffective and use for longer than five hours will confer no further benefit. Thus, the '662 patent requires that the bone be maintained for substantial periods of time at pressures below one atmosphere. There is no disclosure or suggestion of rapidly cycling between elevated and decreased pressures, even though it is suggested that the bone might first be treated at an elevated pressure, followed by a treatment step at a pressure below atmospheric pressure (see, for example, claim 3, column 15). The present invention discloses a process wherein transient and cyclical exposure of an implant material to a given pressure achieves the desired result of implant cleaning, perfusion or passivation.
U.S. Pat. No. 5,556,379 (LifeNet Research Foundation)—“Process for Cleaning Large Bone Grafts and Bone Grafts Produced Thereby,” describes the “Allowash□” process. The patent is explicitly directed to the removal of “bone marrow from the luminal and cancellous bone spaces in large, essentially whole, bone grafts.” (See Summary of the Invention). Accordingly, the referenced patent is directed only to treatment of bone, which has to be largely intact. The stated intent in applying the process to essentially whole bone grafts is to reduce the load of potentially virus carrying bone marrow to facilitate preparation of smaller bone grafts therefrom. The process involves applying a vacuum to the bone graft to draw solution capable of solubilizing bone marrow through articulating cartilaginous surfaces and through the intact bone's intramedullary canal or other bone cavity. The patent neither discloses nor suggests a method in which oscillating pressures are used to clean a bone graft.
U.S. Pat. No. 5,380,826 (Aphios Corporation)—“Supercritical Fluid Disruption of and Extraction from Microbial Cells”, relates to a method for harvesting intracellular components by exposing cells to an elevated pressure in the presence of a solvent, and then rapidly and suddenly releasing the pressure to effect disruption of the cells. The patent also discloses an apparatus for carrying out this process continuously. However, this patent neither discloses nor suggests applying the cell disruption method to allograft bone. U.S. Pat. No. 5,288,462 (Stephen D. Carter)—“Sterilization Apparatus and Method”, describes a chamber for receiving a material to be sterilized by repeatedly subjecting the chamber to elevated pressures, followed by sudden release of the pressure, i.e. “explosive decompression.”The patent requires that the chamber be pressurized to at least 1000 psi. The patent neither discloses, suggests, nor claims application of this method or chamber to sterilization of bone materials. There is no disclosure of cleaning solutions used in connection with the described apparatus that would be effective in sterilizing the matrix of a bone. There is no disclosure that would allow one skilled in the art to determine, without undue experimentation, that bone could be sterilized in this apparatus. In addition, there is no disclosure nor suggestion that an implant could be sterilized without use of such highly elevated pressures, but merely by oscillation of lower absolute pressures.
U.S. Pat. No. 5,725,579 (Bioland)—“Process for Treating Bone Tissue and corresponding Implantable Biomaterials”, is directed to a method of cleaning bone by exposing the bone to a supercritical fluid. As best as can be understood from this patent, this involves exposing bone to carbon dioxide at elevated pressures, in order to solubilize lipids.
Tissue sterilization methods known in the art have undesirable attributes. Gamma irradiation, in order to ensure destruction of pathogens, such as the human immunodeficiency virus (HIV), has to be used at doses that result in tissue destruction (e.g. 3.5 Mrad; see, for example, Rasmussen, et al., J. Arthroscopic and Related Surgery, 10(2):188-197, (1994); Goertzen, et al., British Soc. of Bone and Joint Surg., 77:204-

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