Ureapoietic organ replacement

Details Ureapoietic organ replacement Ureapoietic organ replacement

2001-04-09

2002-10-22

Willse, David H. (Department: 3738)

Prosthesis (i.e., artificial body members), parts thereof, or ai

Implantable prosthesis

Hollow or tubular part or organ

C435S180000

Reexamination Certificate

active

06468312

ABSTRACT:

The invention relates to a bionic organ replacement, i.e. an “artificial liver” for intracorporeal as well as extracoporeal application.
It is general knowledge that different metabolic processes occur in the human liver. The digestive products are stored and processed in the hepatocytes. In addition, essential importance is attributable to the liver as a detoxification organ.
The different structures of the hepatocytes, the cytoplasm, the fine and rough endoplasmic reticulum, lycosomes, peroxisomes and the Golgi complex with mitochondria, each carrying out their respective different functions. As an example mention is made of the generation of urea, the diamide of carbon dioxide in the mitochondrial matrix of the hepatocytes. The formation of bile, i.e. bile salts and bile pigments is also part of the functions of the liver. The bile fluid which is separated by the hepatocytes as secretion is received by the interlobular gall capillaries and transmitted to the interhepatic gall ducts.
It is the object of the present invention to provide an organ replacement which is capable, in case of existing organ insufficiency or organ failure, to assume said functions, at least in part, and which is suitable for intracorporeal as well as extracorporeal application.
Said object is solved according to the invention by a ureapotetic organ replacement in accordance with claim
1
.
The bionic organ replacement has a structure consisting of three groups of hollow textile micro fibers, whereby the hollow micro fibers of each group issue into at least one respectively central liquid conductors, with the hollow micro fibers of the first group being made of proton-conducting material and having perforations for drainage of bile fluid into the interior of the fibers and one of the surfaces of essentially every hollow microfiber of the first group being hydrophilic and lipophilic, whereas the other of the surfaces is hydrophobic and lipophobic, and whereby cell cultures can be grown on the outer surface of all of the hollow micro fibers.
The invention-specific organ replacement is designed in such manner that if hepatocytes are cultured on the surfaces of the hollow micro fibers, said organ replacement is capable of essentially fulfilling all functions of the liver, both intracorporeal as well as extracorporeal. The hollow micro fibers of the structure have textile properties, i.e. they are extremely fine and flexible. They form the capillary vessels of the artificial liver.
The human liver is constructed of approximately 1 to 1.5 million of liver lobules (lobuli hepati), which have a height of approximately 2 mm and a diameter of approximately 1 to 3 mm and consist of liver cells (hepatocytes) which are arranged approximately polyhedrally. The bile which is formed in the liver lobules is drained as secretion via the interlobular gall capillaries and the small gall ducts into the gall bladder (vesica fellea) or via the gall duct (ductus chlodeochus) directly into the small intestine. The interlobular gall capillaries generally have a diameter from 0.1 to 1.5 &mgr;m but can, however, in case of obstruction of the bile flow expand to approximately 15 to 20 &mgr;m.
The functions of the interlobular gall capillaries in the organ replacement according to the invention are carried out by the hollow micro fibers of the first group. They must be made of a material, the same as the natural gall capillaries, which is proton-conductive. Apatit, for example, as well as some polymers, specifically polytetrafluorethylene, have proven themselves suitable for said purpose. In order to provide the larges possible surface for culturing the cells, preference is given to spongiform hollow micro fibers. In addition, the fibers must be structured in such manner that they will selectively pass the involved metabolites, in other words, they are semi-permeable.
Another requirement consists in that one of the surfaces of each hollow micro fiber of the first group, preferably the inner surface, is lipophobic and hydrophobic and the other surface, preferably the outer surface, lipophilic and hydrophilic. In this fashion decomposition of the cells can be prevented by the bile formed in the hepatocytes. The surfaces of the hollow micro fibers can, for example, be rendered lipophobic or hydrophobic, in other words they can be “sealed” by a coating with appropriate polymers and ceramic materials. The relevant technology is known to the expert in this field and is therefore not explained in greater detail.
For purposes of draining the bile into the hollow micro fibers of the first group, these are provided with perforations of the entire wall thickness. The perforations in the hollow micro fibers are made during manufacture by means of stretching and laser application. The bile secretion enters into the hollow micro fibers of the first group via the perforations, said hollow micro fibers constituting the synthetic bile capillaries, and is passed from there to one of several fluid conductors which constitute the synthetic small gall ducts.
In addition to the capillaries and ducts for the bile, the human liver has vessel branches originating from the hepatic artery (arteria hepatica) and the portal vein (vena portae) which supply the liver lobes with blood. The surfaces of the hepatocytes are partially enclosed with cell membranes or plasma membranes which function as separation walls vis-a-vis the neighboring hepatocytes, whereby the distance amounts to approximately 100 to 200 Å. Between the star-shaped hepatocytes approaching the central vein (vena centralis) are formed so-called liver sinusoids, having a diameter equal to approximately 9 to 12 &mgr;m, in which flows the blood coming from the vessel branches to the central vein. Between the sinusoidal wall, permeable with respect to blood plasma and macromolecule, and the hepatocytes, there are so-called Disse's spaces.
According to the invention, the branches or capillaries of the human liver coming from the portal vein and the hepatic artery, are formed by the hollow micro fibers of the second and third group. These have, in accordance with the measurements of the real branches, an inner diameter of approximately 1 to 150 &mgr;m. According to the properties of the branches of the portal vein and the hepatic artery, the hollow micro fibers of the second and third group have a lower proton conductivity and act as ion- or electrolyte separation membranes.
Ceramic substances and polymers have proven themselves as materials particularly appropriate for said purpose. The hollow micro fibers of the second and third group respectively issue in a central fluid conductor, the synthetic portal vein or the synthetic hepatic artery. They can be made of bio-compatible material customarily employed for artificial vessels.
On the organ replacement according to the invention, a culture of human liver cells is grown, preferably in vitro, until the outer surface of the hollow micro fibers is fully overgrown with human liver cells. The liver cells or hepatocytes have in their center the nucleus. In addition, the liver cells have the so-called mitochondria, which are equipped with multi-semipermeable membranes with a cut-off accuracy in the micro-, ultra- or nano-range, with size and load exclusion, or a combination of both, and in which, among others, enzymatic reactions occur for the supply of energy.
Finally, the Golgi apparatuses are located in the liver cells in sequences, in whose so-called cisterns, lipids can occur.
As soon as sufficient cell growth exists, the organ replacement according to the invention can be surgically inserted into the body under application of immuno-therapeutics. It is hereby possible to introduce the medicaments into the interior of the hollow micro fibers. Needless to say, the artificial liver according to the invention can also be used as an extracorporeal organ replacement.
Insertion of the organ replacement into the human body is a fundamentally possible alternative to the in vitro cell culture growth, so that still healthy liver cells grow incorporea

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