Biocompatible coatings

Details Biocompatible coatings Biocompatible coatings

1999-12-15

2002-06-18

Dawson, Robert (Department: 1712)

Stock material or miscellaneous articles

Composite

Of silicon containing

C524S858000, C524S860000, C524S492000, C528S014000, C528S034000, C424S422000

Reexamination Certificate

active

06406792

ABSTRACT:

The present invention relates to methods of coating surfaces to render them substantially biocompatible and to the biocompatible surfaces produced thereby. These coatings are especially valuable on medical devices.
Biocompatible surfaces are important for medical devices. The term ‘biocompatible surface’ is used herein to mean a surface which causes either no or a minimal reaction when it comes into contact with a human or animal body or its blood, fluids or other biological membranes. The term ‘medical device’ is used herein to encompass all medical apparatuses which are used in the treatment of, and come in contact with, a human or animal body or its blood, fluids or other biological membranes. Such medical devices include, for example, implants, prostheses and components used in the delivery or routing of blood or fluids.
When medical devices have non-biocompatible surfaces, they can initiate a reaction by the human or animal body or its blood, fluids or other biologic membranes which may result in serious patient complications such as rejection or post perfusion syndromes. Medical devices have, therefore, conventionally been made of relatively inert plastic or elastomeric materials. These materials, however, have varying degrees of biocompatibility.
Since the biocompatibility of medical devices is generally a result of their surface properties, changing the surface composition, for example by applying or grafting on more biocompatible material, may enhance their bioperformance and improve the patient outcome.
Attempts have been made to improve the surface properties of medical devices. For instance, it is well known to coat the surface of medical devices such as needles with polydimethylsiloxanes for lubrication. In the absence of further treatment (e.g., heat), these polydimethylsiloxanes could migrate from the surface to which they are applied.
U.S. Pat. No. 3,574,673 teaches the use of organosiloxane polymers which can be cured on various surfaces such as needles to provide a lubricating film. The organosiloxane polymers used in this reference comprise aminosiloxane units and organosiloxane units which cure in the presence of moisture to form the film. These organosiloxane polymers, however, require moisture for curing and take a substantial time to cure.
Similarly, U.S. Pat. No. 4,720,521 teaches coating devices such as needles or catheters with a curable silicone composition to form a crosslinked, adherent coating which serves as a matrix for a non-reactive lubricating silicone polymer. The curable silicone composition used in this reference comprises a siloxane polymer which has two or more vinyl groups, a siloxane which has two or more pendant hydrogen atoms, a siloxane chain extending polymer having two or more terminal hydrogen atoms and a platinum catalyst. The coatings of the reference, however, are disadvantageous because of their complex nature and because of the curing techniques.
U.S. Pat. No. 5,061,738 also teaches a blood compatible, lubricious composition for use on medical articles. The composition comprises a quaternary ammonium complex of heparin and a silicone. The silicones disclosed in the composition, however, are not cured and, thus, could migrate from the surface to which they are applied.
We have now discovered a coating that can render a medical device biocompatible without the problems of the prior art.
The present invention relates to a medical device having a biocompatible coating, said biocompatible coating comprising the reaction product of a composition comprising a reactive polysiloxane, an acetoxysilane crosslinking agent, a reinforcing silica and a metal catalyst.
The medical devices which can be coated by the present invention can be any of the known medical apparatuses which are likely to come into contact with a human or animal body or its blood, fluids or other biological membranes. These include, for example, implants and prosthetics such as cardiac valves, shunts, implanted tubes, and the like. It also includes, for example, components of extracorporeal circulation or fluid delivery such as tubing, valves, pumps, cannulas, catheters, needles and the like.
The above medical devices can be made of nearly any material which is suitable for the application. This includes, for example, plastics, elastomers, metals and the like. Specific materials include polyvinylchlorides (PVC), polycarbonates (PC), polyurethanes (PU), polypropylenes (PP), polyethylenes (PE), silicones, polyesters, polymethylmethacrylate (PMMA), hydroxyethylmethacrylate, N-vinyl pyrrolidones, fluorinated polymers such as polytetrafluoroethylene, polyamides, polystyrenes, copolymers or mixtures of the above polymers and medical grade metals such as steel or titanium. Preferred materials include silicones, PVCs, PCs, PUs, PPs, PEs and PMMA.
The medical device made of the above materials is coated with the biocompatible coating of the invention. The entire device may be coated with this coating or, alternatively, just that portion of the device that comes into contact with the human or animal body or its blood, fluids or other biological membranes can be coated.
The biocompatible coating of the invention is the reaction product of a composition comprising a reactive polysiloxane, an acetoxysilane crosslinking agent, a reinforcing silica and a metal catalyst.
The reactive polysiloxane can be nearly any which reacts with the acetoxysilane crosslinking agent to cure and form the biocompatible coating. Such polysiloxanes generally have reactive groups such as hydrogen, hydroxyl, alkoxy or alkoxyalkoxy bound to silicon in the polymer. As such, the reactive polysiloxanes generally have siloxane units of the general structure:
R
m
R
1
SiO
(3-m)
  I
in which each R represents a monovalent hydrocarbon group having up to 20 carbon atoms such as an alkyl (e.g., methyl, ethyl, propyl or butyl) or phenyl groups, m is 1 or 2 and R
1
represents a hydrogen, a hydroxyl (OH) group or an alkoxy group (OR) such as methoxy, ethoxy, propenyloxy and the like. Preferably, R is methyl and R
1
is hydroxyl.
The reactive polysiloxanes can, and preferably does, also have other units such as, for example, units of the general structure:
R
n
SiO(4-n)  II
in which R is as above, and n is 0, 1, 2 or 3. In addition, or alternatively, the polysiloxane can also contain, for example, organic groups such as acrylates, carbonates, polybutylenes or the like.
The reactive polysiloxane can also comprise mixtures or copolymers of the above polysiloxanes. Obviously, however, the polysiloxane must have at least one, preferably at least two, units of formula I for crosslinking.
In a preferred embodiment of the invention, the reactive polysiloxane comprises a polysiloxane having the structure.
OH(Si(CH
3
)
2
O)
x
H  III
wherein x is an integer of 3 to 10,000 or more.
The reactive polysiloxanes can have a wide variety of viscosities such as from about 10 mm
2
/s to gums (e.g., viscosities up to 50 million mm
2
/s) at 25° C. Such polysiloxanes generally have number average molecular weights (Mn) of up to 500,000 or more.
Preferably, the reactive polysiloxane is of Formula III wherein x is an integer which results in a siloxane gum. More preferably, the reactive polysiloxane has a viscosity of 500,000 to 50 million mm
2
/s at 25° C. Most preferably, the reactive polysiloxane has an Mn of about 250,000 to 350,000.
The acetoxysilane crosslinking agent of the present invention comprises a material or a mixture of materials of the structure
R
2
4-b
SiR
3
b
in which R
2
is a monovalent hydrocarbon group having up to 20 carbon atoms such as an alkyl (e.g., methyl, ethyl, propyl or butyl) or a phenyl group, R
3
is an acetoxy group, and b is 2, 3, or 4. In addition, the hydrolysis and condensation products of these silanes such as, for example, polysiloxanes containing the above acetoxy groups are also functional herein.
Examples of specific acetoxysilanes include methyltriacetoxysilane, ethyltriacetoxysilane and mixtures thereof.
The crosslinking agents are used in amounts of about 10 ppm to

Affiliated with

Also associated with

Rating

Biocompatible coatings does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Biocompatible coatings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Biocompatible coatings will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2940797