Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Ketone doai
Reexamination Certificate
2002-07-29
2003-04-29
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Ketone doai
C514S687000, C514S559000, C514S558000, C514S616000, C514S621000, C554S036000, C554S037000, C554S063000, C424S078080, C604S226000, C623S001110, C623S011110
Reexamination Certificate
active
06555587
ABSTRACT:
TECHNICAL FIELD
The present invention relates to reagents and methods for rendering a surface biocompatible, and in particular to reagents and methods for “passivating” the surface of an implantable medical device in order to render it hemocompatible. In another aspect, the invention relates to biomedical devices, per se, and in particular those having biocompatible, including hemocompatible, tissue-contacting surfaces.
BACKGROUND OF THE INVENTION
Manufacturers of implantable medical devices have long attempted to understand, and in turn improve, the performance of materials used in blood-contacting applications (Leonard, E. F., et al.
Ann. N.Y. Acad. Sci.
516, New York, Acad. Sci., New York, 1987). The biological response of the body, as well as problems with infection, have hindered the application of implantable, disposable, and extracorporeal devices. Anticoagulant drugs, such as heparin and coumadin, can improve the use of such devices, although anticoagulants have their own corresponding risks and drawbacks. For these reasons, development of materials having greater compatibility with blood has been pursued aggressively (Sevastianov, V. I.,
CRC Crit. Rev. Biocomp.
4:109, 1988).
Two general strategies that have been used to develop improved blood-contacting materials include modifying the chemistry of the bulk material itself, and/or modifying the interfacial properties of the material. With regard to the latter approach, several classes of materials have been covalently bonded onto blood-contacting surfaces with the goal of improving blood compatibility. These include anticoagulants, such as heparin and hirudin; hydrogels; polyethylene oxide (PEO); albumin binding agents; cell membrane components; prostaglandins; and sulfonated polymers. These approaches have met with varying degrees of success in terms of reducing protein adsorption, platelet adhesion and activation, and thrombus formation. Unfortunately, no approach has yet been shown to be universally applicable for improving blood-biomaterial interactions.
As mentioned above, albumin binding agents have been considered for use on biomaterials. Biomaterials having a high surface concentration of albumin have been shown to be less likely to initiate the fibrin cascade and platelet attachment than those having a high concentration of other serum proteins, such as fibrinogen, fibronectin, or immunoglobulins. On many polymeric materials, however, fibrinogen is often the predominant protein adsorbed from protein mixtures or plasma. For these reasons, investigators have attempted to immobilize albumin onto materials or to design biomaterial surfaces that will enhance binding of endogenous albumin from blood, thus mitigating the adsorption of fibrinogen and consequent thrombogenic phenomena.
In this respect, a number of different approaches have been employed to date. These approaches include passive adsorption or covalent immobilization of albumin to the surface, and the development of surfaces designed to selectively bind endogenous albumin from circulating blood, the latter using alkyl chain-modified materials and other means.
Munro, et al., U.S. Pat. No. 4,530,974, discloses a method of adsorbing albumin to a water-insoluble polymer such as polyurethane by covalently binding to the surface a nonionic hydrophobic aliphatic chain to which serum albumin will selectively bind.
Frautschi et al., U.S. Pat. Nos. 5,017,670 and 5,098,977, teach methods for covalent attachment of aliphatic extensions of 12 to 22 carbon atoms to water-insoluble polymers containing aromatic rings and ring structures with adjacent secondary hydroxyls for increased albumin binding.
Eaton, U.S. Pat. No. 5,073,171, describes a biocompatible prosthetic device incorporating an amount of an albumin binding dye effective to form a coating of endogeneous albumin on the device when the device is in contact with a physiological fluid containing albumin.
While some or all of these various strategies can be used to enhance the binding of endogenous albumin to blood-contacting material surfaces, and in turn to reduce fibrinogen binding, these approaches are each limited in one or more respects. Alkyl chain-modified surfaces have been shown to increase albumin binding and decrease fibrinogen binding, but these effects were fairly limited, for instance, to a short term time frame (generally less than one hour). In addition, various other surface modification methods discussed above are useful for only a narrow range of substrate materials.
On another subject, the assignee of this application has developed the ability to attach bioactive groups to a surface by covalently bonding those groups, directly or indirectly, to the surface. For instance, U.S. Pat. Nos. 4,722,906, 4,979,959, 4,973,493 and 5,263,992 relate to devices having biocompatible agents covalently bound via photoreactive groups and a chemical linking moiety to the biomaterial surface. U.S. Pat. Nos. 5,258,041 and 5,217,492 relate to the attachment of biomolecules to a surface through the use of long chain chemical spacers. U.S. Pat. Nos. 5,002,582 and 5,512,329 relate to the preparation and use of polymeric surfaces, wherein polymeric agents providing desirable properties are covalently bound via a photoreactive moiety to the surface. In particular, the polymers themselves exhibit the desired characteristics, and in the preferred embodiment, are substantially free of other (e.g., bioactive) groups.
It would be highly desirable to be able to attach albumin to a biomaterial surface in a manner that is suitably stable for extended use, particularly in a manner that permits the albumin to be replenished over time and in the course of use.
SUMMARY OF THE INVENTION
The present invention provides a novel reagent for use in passivating a biomaterial surface, the reagent comprising a latent reactive group and a bifunctional aliphatic acid, in combination with a spacer group linking the latent reactive group to the aliphatic acid in a manner that preserves the desired function of each group. The reagent can be used to passivate a surface by activating the latent reactive group in the presence of the surface in order to covalently bond the reagent to the surface. Once bound to the surface, the reagent presents the aliphatic acid to the physiological environment, in vivo, in a manner (e.g., concentration and orientation) sufficient to hold and orient albumin. Preferably, over time, the reagent surface is able to replenish itself by replacing albumin molecules that have become unbound or deteriorated with new albumin molecules. Albumin (e.g., human serum albumin (HSA)), is defined as any naturally occurring proteinaceous moiety containing a fatty acid binding site.
In a preferred embodiment, the reagent is of the general formula (X)
m
—Y—(Z)
n
where X is a latent reactive (e.g., photoreactive) group, Y is a spacer radical, and Z is a bifunctional aliphatic acid, as each are described herein. The values of m and n are ≧1 and while m can equal n, it is not necessary. The aliphatic acid is ‘bifunctional’ in that it provides both an aliphatic region and an anionic (e.g., carboxylic acid) region. Once attached to a surface, these portions cooperate in the process of attracting and binding of albumin in order to passivate the surface.
In the preferred embodiment where both m and n=1, the reagent is termed a heterobifunctional reagent. The aliphatic acid is preferably attached to the latent reactive group by means of a divalent spacer group in a manner that does not detrimentally affect the function of either the aliphatic or anionic portions. Higher-valent spacer groups can also be selected which permit the attachment of multiple aliphatic acid and latent reactive groups, again in a manner which does not detrimentally affect the functions of the respective groups. In this case m does not necessarily equal n and both are ≧1.
In a further embodiment, the spacer group can be a multivalent polymer having multiple sites along the backbone which permit covalent attachment of the aliphatic acid and latent rea
Amos Richard A.
Anderson Aron B.
Everson Terrence P.
Guire Patrick E.
Ghali Isis
Page Thurman K.
Surmodics, Inc.
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