Biomedical moldings

Details Biomedical moldings Biomedical moldings

2001-08-14

2003-04-29

Dees, Jose G. (Department: 1616)

Drug, bio-affecting and body treating compositions

Topical body preparation containing solid synthetic organic...

Ophthalmic preparation

Reexamination Certificate

active

06555103

ABSTRACT:

The present invention pertains to moldings, especially biomedical moldings such as ophthalmic moldings, comprising certain radiation sensitive groups on their surface and to a process for attaching said moldings to living tissue, in particular to the eye as a corneal prosthesis.
It is known e.g. from WO 95/13764 to provide corneal prostheses being composed of porous polymeric material for correcting the optical properties of an eye or altering the appearance thereof. Corneal inlays are in general implanted into or onto the cornea of a mammal using surgical methods, for example by making an incision in the stromal tissue of the cornea to form a pocket into which the onlay is placed, and then closing the incision by suturing.
A more recent method involves removing the corneal epithelial cell layers of the cornea by scraping, placing a synthetic lenticule directly onto and in intimate contact with the corneal tissue and holding it in place for a period of time which is sufficient for the epithelial cells to recover, grow over the implant and thus fix it in a persistent manner. The initial temporary fixation of the onlay on the cornea is accomplished by the use of a biocompatible glue such as a commercially available collagen- or fibrin-based two components glue. However said glues have not yet proven satisfactory mainly because of severe handling problems. For example, the surgeon always has to mix the glue components prior to use. Once the premixing has taken place, only a limited time period is available for using the glue depending on the glue's specific curing time; this puts time-pressure on the surgeon. Following the attachment of the onlay onto the cornea, excessive glue has to be removed carefully because otherwise cured glue residues may inhibit the overgrowth of epithelial cells over the onlay. Further disadvantages of the known glues concern, for example, an insufficient mechanical stability and duration. In view of these and other drawbacks, there is a need for improved methods and materials for a temporary fixation of a polymeric onlay on a cornea.
Surprisingly, it now has been found that biomedical moldings, in particular ophthalmic moldings such as corneal onlays, may be attached conveniently to living tissue if they comprise certain radiation sensitive groups covalently bound to their surface.
The present invention therefore in one aspect pertains to a biomedical molding comprising a non-biodegradable biocompatible organic polymer comprising attached to its surface radicals of formula
wherein R
1
is, for example, hydroxy, C
1
-C
4
-alkyl, C
1
-C
4
-alkoxy, sulfo, nitro, trifluoromethyl or halogen such as, for example, fluorine or chlorine, m is an integer from 0 to 2, and
Z is a group which functions as a triggerable precursor for carbene, nitrene or benzhydrol formation.
Examples of suitable biocompatible organic polymers to which the radicals of formula (1) are attached are polyaddition and polycondensation polymers, for example polyurethanes, epoxy resins, polyethers, polyesters, polyamides or polyimides; polyolefins, for example polyacrylates, polymethacrylates, polystyrene, polyethylene or halogenated derivatives thereof, polyvinyl acetate or polyacrylonitrile; or elastomers, for example silicones, polybutadiene or polyisoprene.
A preferred group of organic polymers are those being conventionally used for the manufacture of biomedical devices, e.g. ophthalmic devices such as contact lenses, artificial cornea ot intraocular lenses, which are not hydrophilic per se. Such materials are known to the skilled artisan and may comprise for example polysiloxanes, perfluoroalkyl polyethers, fluorinated poly(meth)acrylates or equivalent fluorinated polymers derived e.g. from other polymerizable carboxylic acids, polyalkyl (meth)acrylates or equivalent alkylester polymers derived from other polymerizable carboxylic acids, polyolefines, or fluorinated polyolefines, such as polyvinylidene fluoride, fluorinated ethylene propylene, or tetrafluoroethylene, preferably in combination with specific dioxols, such as perfluoro-2,2-dimethyl-1,3-dioxol. Examples of suitable bulk materials are e.g. Lotrafilcon A, Neofocon, Pasifocon, Telefocon, Silafocon, Fluorsilfocon, Paflufocon, Silafocon, Elastofilcon, Fluorofocon or Teflon AF materials, such as Teflon AF 1600 or Teflon AF 2400 which are copolymers of about 63 to 73 mol % of perfluoro-2,2-dimethyl-1,3-dioxol and about 37 to 27 mol % of tetrafluoroethylene, or of about 80 to 90 mol % of perfluoro-2,2-dimethyl-1,3-dioxol and about 20 to 10 mol % of tetrafluoroethylene. A group of particularly preferred hydrophobic polymers are non-porous or particularly porous perfluoroalkyl polyether (PFPE) homo- or copolymers or perfluoroalkyl acrylates or methacrylates, for example those as disclosed in PCT applications WO 96/31546, WO 96/31548, WO 97/35906 or WO 00/15686.
Another preferred group of biocompatible organic polymers are those being conventionally used for the manufacture of biomedical devices, e.g. contact lenses, which are hydrophilic per se, since hydrophilic groups, e.g. carboxy, carbamoyl, sulfate, sulfonate, phosphate, amine, ammonium or hydroxy groups, are inherently present in the material. Such materials are known to the skilled artisan and comprise for example polyhydroxyethyl acrylate, polyhydroxyethyl methacrylate (HEMA), polyvinyl pyrrolidone (PVP), polyacrylic acid, polymethacrylic acid, polyacrylamide, poly-N,N-dimethyl acrylamide (DMA), polyvinyl alcohol, copolymers for example from two or more monomers from the group hydroxyethyl acrylate, hydroxyethyl methacrylate, N-vinyl pyrrolidone, acrylic acid, methacrylic acid, acrylamide, N,N-dimethyl acrylamide, vinyl alcohol, vinyl acetate and the like, polyalkylene glycols such as polyethylene glycols, polypropylene glycols or polyethylene/polypropylene glycol block copolymers. Typical examples are e.g. Polymacon, Tefilcon, Methafilcon, Deltafilcon, Bufilcon, Phemfilcon, Ocufilcon, Focofilcon, Etafilcon, Hefilcon, Vifilcon, Tetrafilcon, Perfilcon, Droxifilcon, Dimefilcon, Isofilcon, Mafilcon, Nelfilcon or Atlafilcon.
Another group of preferred organic polymers are amphiphilic segmented copolymers comprising at least one hydrophobic segment and at least one hydrophilic segment which are linked through a direct bond or a bridge member. Examples are silicone hydrogels, for example those disclosed in PCT applications WO 96/31792 and WO 97/49740.
The form of the organic polymer may vary within wide limits. Examples are moldings of all kinds, for example tubes, films, membranes and in particular ophthalmic moldings, such as contact lenses, intraocular lenses or artificial cornea. Further examples of moldings are materials useful for example as wound healing dressings, eye bandages, materials for the sustained release of an active compound such as a drug delivery patch, moldings that can be used in surgery, such as heart valves, vascular grafts, catheters, artificial organs, encapsulated biologic implants, e.g. pancreatic islets, materials for prostheses such as bone substitutes, or moldings for diagnostics, membranes or biomedical instruments or apparatus.
Z in formula (1) is, for example, a group of formula
wherein R
3
is an electron-withdrawing substituent, for example, fluorinated C
1
-C
6
-alkyl, such as a radical —C
2
F
5
or preferably a radical —CF
3
, R
1
′ independently has the meaning of R
1
, and
m1 independently has the meaning of m.
R
1
and R
1
′ are each independently of the other preferably C
1
-C
4
-alkoxy, C
1
-C
4
-alkyl or sulfo.
The variable m is 1 or preferably 0. The variable m1 is preferably 0.
One group of suitable radicals of formula (1) are those wherein Z is a group
and m is 0.
A further group of suitable radicals of formula (1) are those wherein Z is a group —N
3
, and m is 1 or preferably 0.
The radicals of formula (1) may be attached to the molding surface by any known linking group that is biomedically acceptable and especially ophthalmically acceptable. For example, the radicals of formula (1) may be attached directly to t

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