Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Ligament or tendon
Reexamination Certificate
1998-10-05
2001-04-03
Milano, Michael J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Ligament or tendon
C623S013130
Reexamination Certificate
active
06210441
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a linear block polymer which comprises urea and urethane groups and which has a high molecular weight and which is suited as an implant in living beings such as humans and animals. The invention also comprises a method for the production of the block polymer in question and use thereof as an implant, for example, an implant in the form of ligaments.
PRIOR ART
When injuries arise on the body of a human or an animal or as a result of some disease, a damaged organ must often be replaced temporarily or permanently by some kind of implant. A condition for such an implant to be able to be used is that, firstly, it has such properties, for example strength, that it can replace the functions of the damaged organ and, secondly, that it is biocompatible, i.e. that the body is not poisoned or in some other way damaged by the implant. Different materials, such as pure titanium and some kinds of plastic materials have been shown to have these properties and are already used to a great extent. Other materials are also known in this connection.
The metallic implants, such as titanium and some types of steel are characterized by their great strength and they are therefore used, for example, as tooth implants or for repairing bone fractures, etc. Surgically inserted reservoir containers for medicines which are to be dosed in small amounts during an extended period of time are preferably made of titanium. Different forms of pipes which can replace blood veins or drain out some body liquid are used and these are usually made of thermoplastic materials. They may be used both temporarily and permanently.
Technical Problem
Some implants, such as implants for replacing or supporting a ligament, must have a certain tension strength and have an adapted stretchability. In addition, it is necessary for such an implant that it is also biocompatible and it is also desirable that the implant can promote the growth of the damaged natural ligament at the same time as the implant in many cases should be biologically degradable so that it slowly disappears and the rebuilt ligament resumes its function again.
Solution
According to the present invention, the above problems have been solved and an implant has been created using a new linear block polymer having a molecular weight of at least 10
4
Dalton, preferably at least 10
5
Dalton, comprising urea and urethane groups and ester groups at such a distance from each other that after hydrolysis of these ester groups fragments are created which are so small that they can be excreted from a human body and further comprising primary NH
2
and/or OH end groups, which can be substituted by for example monoamines, such as butylamine or ethylamine.
According to the invention, the linear block polymer should have at least as many or more urea groups as urethane groups.
The linear block polymer according to the present invention can, in the chain, also contain such groups as polytetramethylene oxide, polyethylene oxide, polycaprolactone, polyethylene glycol adipate, tolylene, diphenyl methane, hexamethylene, tetramethylene, naphthylene, glycerine monoallyl ether, trimethylol propane monoallyl ether, glycerine monoglycidyl ether, dimethylol propionic acid methyl ester, dimethylol propionic acid bromobutyl ester, esters of monocarboxymethyl ethers of glycerine and trimethylol propane and other additional groups which modify the properties of the block polymer.
The invention also includes a method for the production of linear block polymers and it is characterized in that a prepolymer having two isocyanate end groups per molecule is chain extended with an aliphatic or aromatic diamine having a mol ratio of NH
2
/NCO of 0.95-1.05, preferably 0.98-1.02.
According to the invention, the prepolymer is suitably produced by providing a diol with two isocyanate end groups per molecule. The prepolymer may be a mixture of prepolymers having different composition.
According to the invention, it is suitable that the diol consists of a polyester diol, for example, polydiethylene glycol adipate diol, polycapro-lactone diol or polyethylene glycol adipate diol, or a polyether diol such as polytetramethylene oxide diol, polyethylene oxide diol or a monodiol such as glycerine monoallyl ether, trimethylol propane monoallyl ether, glycerine monoglycidyl ether, dimethylol propionic acid methyl ester, dimethylol propionic acid bromobutyl ester, esters of monocarboxymethyl ethers of glycerine, trimethylol propane, and others and the isocyanate-supplying compound is suitably 4, 4′-diphenyl methane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, naphthylene diisocyanate and others. The diol may also consist of mixtures of diols.
According to the invention, it is suitable that the diamine consists of primary diamines, preferably ethylene diamine or 1.3-diaminopropane or hydrolysable diamines, for example, 1.3-propane diol-bis-p-aminobenzoate or ethylene glycol-bis-diamino acetate.
The molecular weight and its distribution may, according to the invention, be controlled by the stoichiometric relationship but primarily by addition of small amounts of monoamine, for example butyl amine or ethanol amine.
The method according to the invention also includes that built-in groups in the chain are modified by a reaction with physiologically active substances. Those groups which, according to the invention, are modified are suitably glycerine monoallyl ether, trimethylol propane monoallyl ether, glycerine monoglycidyl ether, dimethylol propionic acid methyl ester, and dimethylol propionic acid bromobutyl ester.
The linear block polymer according to the invention is suitable as material in implants in humans and animals.
When the block polymer is used as an implant this is suitably an implant for ligaments, tendons, skin or cartilage.
According to the invention, it is suitable that when the polymer is used as an implant it has the form of fibres or threads which have been knitted or woven.
According to the invention, it is suitable that the block polymer, by means of its NH
2
or OH end groups, is used for covalent binding of growth-promoting groups. The OH groups can be obtained by, for example, using ethanol amine as a chain stopper.
DETAILED DESCRIPTION
Block polymers or block copolymers are defined as copolymers in which participating monomers are present as sequences or blocks of different lengths which are linearly united to each other to molecules having a high molecule weight (>10
4
Dalton). The latter is important for the mechanical properties and necessary for making fibres and films.
An advantage of block polymers is that properties which are characteristic for several homopolymers can be built in in one and the same molecule. In this way, incompatible polymers can be brought to cooperate in a material and apparently non-compatible properties can be combined. Thus, reactive side groups can be introduced. Further, hydrolysable blocks may, for example, be introduced which, after hydrolysis, give fragments of polymers which are sufficiently small to be secreted from the body.
A common way to describe block polymers is as follows. The monomer A forms the block A-A-A-A-A . . . , called polyA or pA and the monomer B forms the block B-B-B-B . . . , polyB or pB. They are united to -A-A-A-A-B-B-B- or pA-pB in the production process. Typical block polymer types are diblock, triblock and multiblock polymers. In the present invention, the multiblock type is the one mostly used. It is written pA-pB-pA-pB-pA-pB . . . in which the block types alternate. By partially exchanging the block types, variants can be produced which give further properties to the polymer. The invention relates to production of such variants in which the third component (and possibly a fourth) randomly replaces one of the blocks, for example pB.
The invention uses isocyanate chemistry to synthesise the block polymers, which will be of the type polyurethane urea groups. Both form hydrogen bonds between the molecules, which gives t
Artimplant Development Artdev AB
Milano Michael J.
Munday John S.
Phan Hieu
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