Chemistry: molecular biology and microbiology – Carrier-bound or immobilized enzyme or microbial cell;... – Enzyme or microbial cell is immobilized on or in an organic...
Reexamination Certificate
2000-06-09
2003-02-04
Naff, David M. (Department: 1651)
Chemistry: molecular biology and microbiology
Carrier-bound or immobilized enzyme or microbial cell;...
Enzyme or microbial cell is immobilized on or in an organic...
C424S130100, C424S184100, C435S181000, C435S395000, C435S402000, C436S531000, C436S532000, C514S002600, C530S402000, C530S815000, C530S816000
Reexamination Certificate
active
06514734
ABSTRACT:
FIELD OF THE INVENTION
In one aspect, this invention relates to reagents that can be used to modify biomaterial surfaces or to fabricate new biomaterials. In another aspect, the invention relates to biomaterials having surfaces that have been prepared or modified to provide desired bioactive function.
BACKGROUND OF THE INVENTION
Biomaterials have long been used to fabricate biomedical devices for use in both in vitro and in vivo applications. A variety of biomaterials can be used for the fabrication of such devices, including ceramics, metals, polymers, and combinations thereof. Historically, such biomaterials were considered suitable for use in fabricating biomedical devices if they provided a suitable combination of such basic properties as inertness, low toxicity, and the ability to be fabricated into desired devices. (Hanker, J. S. and B. L. Giammara,
Science
242:885-892, 1988).
As the result of more recent advances, devices can now be provided with surfaces having various desirable characteristics, e.g., in order to better interface with surrounding tissue or solutions. For instance, approaches have been developed to promote the attachment of specific cells or molecules to device surfaces. A device surface, for instance, can be provided with a bioactive group that is capable of attracting and/or attaching to various molecules or cells. Examples of such bioactive groups include antigens for binding to antibodies, ligands for binding to cell surface receptors, and enzyme substrates for binding to enzymes.
Such bioactive groups have been provided on the surfaces of biomaterials in a variety of ways. In one approach, biomaterials can be fabricated from molecules that themselves present the desired bioactive groups on the surfaces of devices after fabrication. However, desirable bioactive groups are typically hydrophilic and cannot be incorporated into most metals or hydrophobic polymeric biomaterials at effective concentrations without disrupting the structural integrity of such biomaterials.
An alternative approach involves adding bioactive groups to the surfaces of biomaterials, e.g., after they have been fabricated into medical devices. Such bioactive groups can occasionally be added by adsorption. However, groups that have been added by adsorption cannot typically be retained on surfaces at high levels or for long periods of time.
The retention of such bioactive groups on a surface can be improved by covalent bonding of those groups 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 a photoreactive group 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 5,263,992 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.
Others have used photochemistry to modify the surfaces of biomedical devices, e.g., to coat vascular grafts. (See, e.g., Kito, H. et. al.,
ASAIO Journal
39:M506-M511, 1993. See also Clapper, D. L., et. al.,
Trans. Soc. Biomat
. 16:42, 1993).
Cholakis and Sefton synthesized a polymer having a polyvinyl alcohol (PVA) backbone and heparin bioactive groups. The polymer was coupled to polyethylene tubing via nonlatent reactive chemistry, and the resultant surface was evaluated for thromboresistance in a series of in vitro and in vivo assays. For whatever reason, the heparin in the polymer prepared by Cholakis and Sefton did not provide effective activity. (Cholakis, C. H. and M. V. Sefton,
J. Biomed. Mater. Res
. 23:399-415, 1989. See also Cholakis, C. H., et. al.,
J. Biomed. Mater. Res
. 23:417-441, 1989).
Finally, Kinoshita et. al. disclose the use of reactive chemistry to generate polyacrylic acid backbones on porous polyethylene, with collagen molecules being subsequently coupled to carboxyl moieties on the polyacrylic acid backbones. (See Kinoshita, Y., et. al.,
Biomaterials
14:209-215, 1993).
Generally, the resultant coating in the above-captioned situations is provided in the form of bioactive groups covalently coupled to biomaterial surfaces by means of short linear spacers. This approach works well with large molecular weight bioactive groups, such as collagen and fibronectin, where the use of short spacers is desired and the size of the bioactive group is quite large compared to that of the spacer itself.
The approaches described above, however, with the possible exception of Kinoshita et al., are not optimal for coating small molecular weight bioactive groups. Kinoshita does appear to coat small molecular weight molecules, although it describes a laborious multistep process that can detrimentally affect both yield and reproducibility.
Small molecular weight bioactive groups are typically provided in the form of either small regions derived from much larger molecules (e.g., cell attachment peptides derived from fibronectin) or as small molecules that normally diffuse freely to produce their effects (e.g., antibiotics or growth factors). It appears that short spacers can unduly limit the freedom of movement of such small bioactive groups, and in turn, impair their activity when immobilized. What are clearly needed are methods and compositions for providing improved concentrations of bioactive groups, and particularly small molecular weight groups, to a biomaterial surface in a manner that permits improved freedom of movement of the bioactive groups.
SUMMARY OF THE INVENTION
The present invention addresses the needs described above by providing a “polybifunctional” reagent comprising a polymeric backbone bearing one or more pendent photoreactive moieties and one or more, and preferably two or more, pendent bioactive groups. The reagent preferably includes a high molecular weight polymer backbone, preferably linear, having attached thereto an optimal density of both bioactive groups and photoreactive moieties. The reagent permits useful densities of bioactive groups to be coupled to a biomaterial surface, via one or more photoreactive groups. The backbone, in turn, provides a spacer function of sufficient length to provide the bioactive groups with greater freedom of movement than that which could otherwise be achieved, e.g., by the use of individual spacers (as described above).
As an added advantage, the present reagent permits the formation of inter- and intra-molecular covalent bonds within and/or between polymer backbones and the biomaterial surface, thereby providing an optimal and controllable combination of such properties as coating density, freedom of movement, tenacity and stability.
In addition to its use in modifying a biomaterial surface, a reagent of the invention provides other benefits as well. The photoreactive moieties allow individual polymer molecules to couple efficiently (e.g.,.crosslink) with adjacent polymer molecules. This crosslinking characteristic allows the polymers to generate thick coatings upon biomaterial surfaces and/or to generate independent films and bulk materials, either in vitro or in vivo.
The present invention also discloses a method for synthesizing a polybifunctional reagent and for providing a coated surface, such as the surface of a biomaterial, or biomedical device fabricated from such a biomaterial. The coated surface, having molecules of the polybifunctional reagent attached thereto in order to provide the device with desirable properties or attributes.
The photoreactive moieties can be activated in order to attach the polybifunctional reagent to a surface providing abstractable hydrogen atoms in such a manner that the pendent bioactive group(s) retain their desired bioactive function. Preferably, the reagent is attached to the surface
Amos Richard A.
Clapper David L.
Everson Terrence P.
Hu Sheau-Ping
Swanson Melvin J.
Fredrikson & Byron , P.A.
Naff David M.
Surmodics, Inc.
LandOfFree
Polybifunctional reagent having a polymeric backbone and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polybifunctional reagent having a polymeric backbone and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polybifunctional reagent having a polymeric backbone and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3126062