Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis
Patent
1998-02-09
2000-08-29
Yu, Mickey
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
623 146, 623 236, 427 224, 427453, 4271263, 606 76, 4283044, 4283155, A61F 200, A61L 2704, A61L 2728, A61L 3300
Patent
active
061102040
DESCRIPTION:
BRIEF SUMMARY
This invention relates to implants.
Various artificial materials are introduced into the human body as a short-term or relatively long-term implant for diagnosis and treatment (catheters, probes, sensors, stents, artificial heart valves, endotracheal tubes etc.). The selection of the material for these implants depends on the stability and geometry required to insure a certain function of the implant. In order to meet these functional demands, it is often not possible to pay sufficient regard to the fact of whether these materials are biocompatible. Therefore, it is useful to improve the materials from which these implants are made by coatings which are compatible with blood and tissue. Coatings are required which activate the coagulation system only to a minor degree, and which cause few endogenous defense reactions thus reducing the deposit of thrombi and biofilm on the implant surface. A coating is useful for all materials which are directly introduced into the bloodstream, e.g. for vascular prostheses, stents, artificial heart valves, as well as for implants which are in contact with tissue, e.g. cardiac pacemakers or defibrillators and for implants which are in contact with body fluids, e.g. bile duct drains, catheters for draining urea and cerebrospinal fluid, and endotracheal resuscitation tubes. The blood compatibility of implants is influenced decisively by their surface properties. In order to avoid the formation of thrombi ("antithrombogeneity"), relative smoothness is necessary to prevent the deposit and destruction, of corpuscular components of the blood and activation of the coagulation system. In addition, direct charge exchange processes must be prevented between coagulation-specific proteins and the implant surface.
It is known to use coatings made of pyrolytic carbon as a common material for heart valves to meet these demands. In addition, it is known to use semi-conducting materials, e.g. a-SiC:H as an implant coating, to prevent the charge exchange processes between the coagulation-specific proteins and the implant surface (A. Bolz, M. Schaldach, "Haemocompatibility optimisation of implants by hybrid structuring", Med. & Biol. & Comput., 1993, 31, pp. 123-130). Furthermore, it is known to employ Ti.sub.6 Al.sub.4 V as a coating (I. Dion, C. Baquey, J.- R. Monties, P. Havlik, "Haemocompatibility of Ti.sub.6 Al.sub.4 V alloy", Biomaterials, Vol. 4, 1993, pp. 122-126). A plurality of plastics have also been investigated in the field of polymer chemistry to produce non-adhering surfaces. In this field as well, the problem has not yet been solved satisfactorily (R. F. Brady Jr., "Coming to an unsticky end", Nature, Vol. 368, 1994, pp. 16-17).
Although implants having a carbon coating and a porous structure meet the demands made on the surface properties, they have the drawback that an electron transfer caused by tunneling of occupied, valence band-like states of the protein to free states of the solid leads to cleavage of fibrinogen in the blood. The resulting fibrin monomers polymerize and produce an irreversible thrombus. Although implants made of rutile ceramics prevent these charge exchange processes, they were not ready for series production because of the high production costs. Although implants having a coating made of amorphous carbon (a-SiC:H) can be produced in a cost-effective fashion, the drawback of this material consists in that it is not hard enough for certain applications. This material is presently produced by means of CVD methods which require great heating of the substrate as an additional problem, so that application is made more difficult for a large number of heat-sensitive basic materials. In addition, this material has a fixed band gap and low conductivity. Both properties lead to the formation of thrombi rather than preventing them.
Therefore, it is the object of the present invention to provide an implant of the above-mentioned kind with a surface by which the activation of blood coagulation accompanied by the formation of thrombi as well as the formation of a biof
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Lazarov Miladin
Mayer Isabella
Halluin Albert P.
Huber & Schussler
Koh Choon P.
Smith J. David
Yu Mickey
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