Biocompatible medical devices with polyurethane surface

Details Biocompatible medical devices with polyurethane surface Biocompatible medical devices with polyurethane surface

2001-09-25

2004-08-10

Szekely, Peter (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C427S335000, C528S493000, C528S494000, C604S096010, C606S195000

Reexamination Certificate

active

06774157

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the manufacture and treatment of articles and devices which may be temporarily, long-term, or permanently inserted as medical devices, accessories, implants or replacements into animal bodies, such as the human body. The present invention particularly relates to the manufacture and treatment of polymeric articles such as implants, prostheses, catheters, stents, shunts, heart valves and ducts for use in animal bodies.
2. Background of the Art
Modern medicine has enabled the use of many newer, non-classical surgical invasive techniques in the treatment of diseases. Implantation of temporary or permanent structural and functioning elements has become commonplace, while merely twenty years ago, such implants were quite rare. Early implants were limited to surgical grade metals and were primarily used for gross mechanical repairs such as bone securement or replacement Even today, oral surgery supports for permanent dentures are still made from surgical grade metal (e.g., titanium) as are Selby and Spinetech™ back surgery medical devices.
Improvements in the chemical types of and construction techniques for polymeric materials has enabled a broader use of these materials in the medical field. Typical areas where polymeric materials are used within the bodies of patients include, but are not limited to catheters, shunts, mesh closures or patches (e.g., vascular grafts), general prostheses construction, artificial muscle attachments (e.g., artificial ligaments), insulation for electrical devices (e.g., for pacemakers and drug delivery systems), and the like. Many early attempts at the use of polymeric materials within patients resulted in rejection, physical irritation, rapid deterioration of the composition, cracking and fissuring, and thrombus formation. The formation of blood clots is particularly dangerous where the inserted object has a lumen which can be closed or restricted by the clot, either blocking the function of he tube or being sloughed off, causing a phlebitic, stroke-like, or other non-conductive event within the patient.
U.S. Pat. No. 4,475,972 describes the formation of prostheses, by the extrusion or spinning of polymer fibers into porous vascular grafts. The fine nature of the fibers used in the grafts has been identified as a possible source of thrombogenic activity when fibers break or crack.
U.S. Pat. No. 4,882,148 describes implantable polymeric devices with reduced cracking and thrombogenic problems by treating the surfaces of the polymeric implantable material with a sulfonating agent, such as sulfur trioxide and fuming sulfuric acid. The sulfur trioxide may also be provided in combination with a primary alcohol. Treatment may be effected by dipping in the sulfonating composition or, in the case of sulfur trioxide, by directly exposing the prostheses to sulfur trioxide vapor. This reference indicates that a chemical reaction occurs between the sulfonating agent and the filaments, because it is specifically indicated that the porous networks generally cannot withstand the heat of reaction from these concentrated sulfonating agents which tend to melt or distort the porous network before the sulfonation reaction is complete. The fact that sulfonation of the polymer can be observed after neutralization treatment indicates a chemical reaction which attaches sulfur containing moieties into the polymer composition of the implant.
U.S. Pat. No. 4,713,402 describes the use of solutions of particular ratios of chlorofluorocarbon compounds and petroleum ether, and after exposure of the devices to the solutions, the treated device is exposed to the application of antithrombogenic/antibacterial agents. The patent also provides a good background description of prior art techniques for heparinizing polymer surfaces to reduce blood-polymer interactions.
U.S. Pat. No. 4,656,083 describes the use of non-chemical means (gas plasma discharge) to improve the biocompatability of biomaterials.
U.S. Pat. No. 4,536,179 describes the application of thin films of plasma polymerized fluorocarbon coatings on the surface of catheters to improve their long term bio-acceptability.
U.S. Pat. No. 5,147,724 describes the use of a gas mixture comprising fluorine and a gaseous oxidizing agent to improve the smoothness of plastic surfaces such as polymers of ethylene, propylene, butadiene, polystyrene and hydrocarbon compounds.
U.S. Pat. No. 4,529,563 describes the treatment of thermoplastic surfaces with a vapor phase of solvents which form an azeoptropic mixture. The solvents comprise both a ‘destructive’ solvent and a ‘non-destructive’ solvent. The treatment is said to improve the physical properties of the thermoplastic substrate.
U.S. Pat. No. 4,302,418 describes a fluid medium used in a process for polishing surfaces of plastic components which is insoluble or inert within the fluid medium until an elevated temperature is reached. It is described as particularly useful for polishing the internal surfaces of tubing components for medical equipment The process includes applying a vaporized solvent at an elevated temperature to liquefy or melt insoluble plastic component surfaces without deforming the component, followed by solidifying or freezing the surfaces by removing the component from the vapors.
U.S. Pat. No. 3,807,054 describes a process for enhancing the appearance of plastic articles such as telephone cases comprising treating the plastic articles within a gas-tight environment with a vapor at an elevated temperature to liquefy the surface of the plastic and then cooling the plastic to return the surface to a solid state. This removes large scratches from the surface of relatively thick articles such as telephone casings.
SUMMARY OF THE INVENTION
The present invention provides a method for improving the bio-compatibility of medical devices which are invasively present within a patient's body. The present invention particularly reduces the thrombogenicity of polyurethane materials in contact with the blood of a living patient. The method comprises providing a bio-compatible medical device having polymeric polyurethane components thereon, exposing the polyurethane components of the medical device to polar solvents for said polymeric components while the polar solvents are in the vapor phase (i.e., without direct physical contact of the polymeric component to a mass of liquid solvent, although some condensation may occur on the surface of the polyurethane), and allowing said vapor phase exposure to continue for a sufficient amount of time as to soften at least some irregular or sharp features on the surface of the polymeric component.
The invention describes a method of improving a medical device having at least one polymeric component, the process comprising the steps of providing a vapor phase comprising a solvent for said polymer component, and exposing said polymeric component to said vapor phase. The process comprises taking a polyurethane component has a surface with a topography (e.g., roughness, sharp edge features, deviations from planarity and the like), and exposing the polyurethane component to said vapor phase increases planarity in said topography. This is done without altering the chemical compositiomn of the polymer component or without necessarily effecting a chemical reaction between the solvent and the polymer component, and because of the control of the amount of solvent which can contact the polymer, the potential for damage to the polymeric component is reduced. In particular, the vapor phase treatment will reduce the dimensions of extrusion markings on the exterior surface of the polyurethane with minimum potential for damage to the structure of the polyurethane, even where the polyurethane is present as thin walls (e.g., less than 0.0762 mm).
Polyurethane articles having wall thicknesses of less than about 3 mils (e.g., less than about 0.076 mm) can be treated with this process to reduce surface roughness without damaging the structural integrity of the article. In this w

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