Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2002-06-05
2004-08-03
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S038000, C528S065000, C528S066000, C528S070000, C528S335000, C528S359000, C528S401000, C528S391000, C528S392000, C528S044000, C530S300000, C530S345000
Reexamination Certificate
active
06770725
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to macromolecules containing biologically active drugs/biomolecules, or precursors thereof, and fluoroligomers; compositions comprising said macromolecules containing biologically active drugs/biomolecules and fluoroligomers in admixture with polymers, particularly biomedical polymers; articles made from said admixtures, particularly medical devices; and methods of preparation of said macromolecules containing biologically active drugs/biomolecules and fluoroligomers.
BACKGROUND TO THE INVENTION
Biomedical polymers (includings polyamides, polyurethanes, polysilicones, polyfluorocarbons, polysulfones, polyolefins, polyesters, polyvinyl derivatives, polypeptide derivatives, polysaccharide derivatives etc. ) are applied extensively in the manufacture of conventional biomedical devices used in contact with living tissues, body fluids and its constituents, such as vascular and skin grafts, endotracheal tubes and catheters, drug delivery vehicles and affinity chromatography systems [1]. Many synthetic polymers have characteristics that make them useful as biomedical materials. One reason for this is the wide range of properties available from man-made polymers. The chemistry of the repeat unit, the shape of the molecular backbone, and the existence and concentration of intermolecular bonds among the macromolecules that make up the polymeric material all influence its ultimate properties. Additional variations in polymer character is possible in polymers with more than one kind of repeating unit. Copolymers, terpolymers, and even multipolymers are possible in which the properties of more than one polymer type are combined to produce a unique material. The arrangement of the different repeat units in copolymers allows further property variations. The overall concentration of each monomer is also an important parameter in determining the properties of the copolymers, but unless one monomer is used in great excess over the other, the resulting properties can be quite different from either homopolymer.
Biocompatibility
Biocompatibility is defined as the ability of a material to perform with an appropriate host response in a specific application. The host relates to the environment in which the biomaterial is placed and will vary from being blood, bone, cartilage, heart, brain, etc. Despite the unique biomedical related benefits that any particular group of polymers may possess, the materials themselves, once incorporated into the biomedical device, may be inherently limited in their performance because of their inability to satisfy all the critical biocompatibility issues associated with the specific application intended. For instance while one material may have certain anti-coagulant features related to platelets it may not address key features of the coagulation cascade, nor be able to resist the colonization of bacteria. Another material may exhibit anti-microbial function but may not be biostable for longterm applications. The incorporation of multi-functional character in a biomedical device is often a biomedical device is often a complicated and costly process which almost always compromises one polymer property or biological function over another, yet all blood and tissue contacting devices can benefit from improved biocompatibility character. Clotting, toxicity, inflammation, infection, immune response in even the simplest devices can result in death or irreversible damage to the patient. Since most blood and tissue material interactions occur at the interface between the biological environment and the medical device, only the make-up of the outer molecular layer (at most the sub-micron layer) of the polymeric material is relevant to the biological interactions at the interface. This means that as long as the polymer does not contain any leachable impurities, the chemistry of the bulk polymer, which is distant from the biological interface, should have a minimal influence on tissue and body fluid interactions if the material surface is relatively biostable.
Surface Modification
Given the knowledge that it is the surface that is the most pertinent issue in the matters of biocompatibility, a practical approach taken towards the development of biomedical devices has involved the utilization of polymeric materials that satisfy the bulk material criteria for the device while applying some form of surface modification which may specifically tailor the biological surface properties and produce minimal change to the bulk character. Such an approach is seen advantages over grafting biologically active agents to the bulk polymer chains since the latter approach brings about significant changes to the physical structure of the polymers [2]. Methods that have been used for the surface modification of polymer surfaces rather than bulk grafting of the polymers have included the following: Non-covalent coatings (with and without solvent), chemical surface grafting, ion implantation, Langmuir-Blodgett Overlayer and self assembled films, surface modifying additives, surface chemical reactions and etching and roughning.
Surface Modifying Macromolecules
The use of oligomeric surface modifying additives present a significant advance over many commercial surface coating technologies reported above (i.e. radiation grafting polymerization; chemical coating, solvent coating; electron radiation; plasma polymerization or deposition; etc.), since it is a one step operation which can be simultaneously carried out with normal extrusion, film casting, fibre spinning and injection molding processes. The technology is readily transferable from one field to the next because it is adaptable to different polymer systems, analogous to additives such as colorants. General applications have included desoiling agents [3] and membrane applications for the separation of organics and water [4]. In areas of specific interest to the biomedical field, polymeric additives have been developed for applications in polyurethanes and other materials [5,6]. Ward et al. [7], issued describes polymer admixtures formed from a base polymer and thermoplastic copolymer additives having polar hard segments and polar and no-polar soft blocks in graft or block copolymer form, for use in biomedical devices. Ward et al. [7], describes novel linear polysiloxane-polylactone block copolymers, particular polysiloxane-polycaprolactone linear blocked copolymers, miscible with nylon for use as surface-modified nylon articles. Ward et al., [8] describes end-group containing polymers that comprise a linear base polymer having covalently bonded surface active end groups of a nature and present in an amount such that the polymer has a surface interaction tension that differs by at least 1 dyne/cm from the surface or interfacial tension of an otherwise identical polymer that does not contain the covalently bonded surface active endgroups. Santerre [6] describes fluoroligomers and compositions comprising fluoroligomers as surface-modifiers in admixture with polymers, for providing articles with passive surface properties, particularly, medical devices that shield enzyme interactions along with having acceptable passive blood compatibility.
It should be noted that in cases pertaining to the end group's described above [6,8], and the influence of the latter on cells, proteins and other biomolecular functions, the type of the interaction is relatively non-specific and it is preferred to be passive in nature, meaning that the surface generated by the end groups does not contain in itself a defined biochemical action that allows it to be both surface active and express a specific biological action on individual cellular mechanisms, specific protein or enzyme activity, or messenger action in the case of peptide signaling molecules. For the latter, the biomedical community still relies on traditional methods of therapy, i.e. the delivery of drugs or bio-active molecules via traditional diffusion mechanisms. Clas
Moore Margaret G.
Morgan & Lewis & Bockius, LLP
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