The invention relates to a plastically deformable implant for inserting into bodily orifices of the human or animal body. Implants of this type are used, for example, in ophthalmology, in particular, as vitreous body or lens replacements and in dentistry, for example, for filling extraction cavities in jaw-bones. Known implants, however, are not suitable for long-term use. The invention aims to provide a deformable plastic implant which also has a long-term application. This is achieved by the fact that the implant consists of a gel which is not sealed, containing fluorocarbon and which is directly introduced into the natural, or artificially created bodily orifice.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Because of their versatile and variable properties, the fluorine-containing gels described above are suitable for use as a starting material in the construction of a generic implant. For such an implant to be of long-term use, however, it must be ensured that the implant does not irreversibly liquefy when exposed to aqueous media. In addition, the implant must have a long-term stability to mechanical and thermal stresses. The stability of the implant material on exposure to heat must be ensured, in particular, because the material must be sterilized (121° C.) prior to inserting it into the bodily orifices. One finding on which the present invention is based relates to the fact that the gel structure of certain fluorine-containing gels is reversible and can be completely recovered even after it has been considerably damaged. Compared to the prior printed publications on fluorine-containing gels, this finding comes as a surprise.

According to the present invention, the term fluorine-containing gel is defined as a gel-like preparation which comprises a minimum of one fluorocarbon. In especially useful embodiments of the present invention, the fluorine-containing gel comprises essentially three components, i.e., a fluorocarbon, a fluorine-containing surface-active agent, and water. It is possible for different additives to be added to the fluorocarbon-containing and aqueous components. Certain compositions of surface-active agents, fluorocarbons, and water form gels which are able to completely recover their gel structure after they have been liquefied, for example, by exposure to mechanical pressure or heat. This property of the gels according to the present invention makes it possible for them to be used as a generic implant over a long period of time. If the implant material of such an implant that has been inserted into a bodily orifice were to liquefy, for example, as a result of short-term pressure, the gel structure, due to the reversibility described, would be able to recover when in a state of rest. Thus, the implant according to the present invention has a self-regulating restorative mechanism. This self-regulating restorative mechanism of a polyaphron gel is attributable to the stability of the aphrons that form the gel. After liquefaction, a gel can restore its structure only if its "building blocks," the aphrons, were not completely destroyed. If a sufficient number of intact aphrons remain after liquefaction, a recovery is possible, and what comes as a surprise is the fact that the aphron structure is transferred to the homogenized regions of the surrounding liquid and that the gel structure is restored in the entire liquid. The stability of the aphrons depends on the intensity of the interaction between water, surface-active agent, and perfluorocarbon, which in turn is determined by the surface properties and the ability of the individual phases to spread on each other's surface. In addition, an important aspect is the intensity of the interactions of the molecules within the films that envelop the aphrons (water/surface-active agent; perfluorocarbon/surface-active agent). Thus, the self-regulating restorative mechanism is activated only if the surface properties of the surface-active agent/water and/or surface-active agent/perfluorocarbon film, on the one hand, and of the internal aphron phase, on the other hand, are properly coordinated, i.e., if the strength of the surface-active agent stabilizes the aphron structure. This can be implemented through the use of fluorine-containing surface-active agents of the general formula

R_F—R_pol,

where R_F stands for the linear or branched perfluoroalkyl groups with more than 5 carbon atoms and R_pol stands for a polar hydrocarbon residue which comprises a minimum of one functional group which is selected from CO—NH(R), CO—N(R)₂, COO—, COOR, SO₃; SO₂N(R)₂, CH₂—O—R, PO₂H, PO₃H. The molecular weight is preferably >400 g/mol, the surface tension in aqueous solution is <30 mN/m and preferably <20 mN/m. The interfacial tension in aqueous solution with respect to the nonpolar component is <25 mN/m, preferably <10 mN/m, and the concentration is <3%, preferably <0.1%. With nonfluorinated surface-active agents, this can be achieved by means of a strong cohesive effect with an HLB value greater than 25 (HLB=hydrophilic lipophilic balance according to Griffin in J. Soc. Cosmet. Chem. 1 (1949), p. 311).

Thus, the implant according to the present invention is able to resist both thermal stress, for example, during sterilization, and mechanical stress, for example, pressure exerted on the bodily orifice. Furthermore, the ability of the implant according to the present invention to reverse the damage to its structure prevents the destruction of the implant material that is caused by diffusion processes in the bodily orifices. In the implants according to the present invention, the light transmittance of the fluorine-containing gels which in other gels is generally considerably impaired as a result of these diffusion processes remains in a dynamic equilibrium.

The biocompatibility of the implants according to the present invention is ensured since ultrapurified starting materials and very small quantities of surface-active agents (preferably <0.1%) are used. Moreover, the surface-active agents used are histocompatible, intimately bonded to the gel, and homogeneously distributed throughout the entire volume.

The implant according to the present invention is used, for example, in ophthalmology as a vitreous body replacement. For this purpose, in particular fluorine-containing gels with a high specific weight and, at the same time, a high affinity to water-soluble substances are suitable. Thus, for the first time, a tamponading material or implant with a specific weight higher than that of water and, at the same time, the capacity to absorb water-soluble ions are made available. After vitrectomy and conventional procedures of retinal surgery, the plastically deformable implant is injected into the space of the vitreous body. As a result of the absorption of water, the plastically deformable implant expands. The increase in volume caused by the absorption of water enhances the tamponade effect mediated by the highly dense fluorocarbons. At the same time, pressure builds inside the implant, and this pressure counteracts a further expansion in volume and absorption of water. The dynamic equilibrium that is established as a result is ensured by the structural reversibility of the implant material and thus makes it possible for the implant to be used for long-term applications.

An additional advantage of the implant according to the present invention when used as a vitreous body replacement is the reduction of mechanical injuries in the region of the retina. Such injuries are known to arise when pure fluorocarbons are used as vitreous body replacement materials and have been attributed to the high density of the fluorocarbons. Only recently it was discovered that the injury is not caused by the static pressure. Instead, the injuries are attributable to the fact that the impalement of heavy fluids on the retina—as it occurs, for example, when the head is moved rapidly—causes an increase in the mechanical pressure. When using fluorine-containing gels as vitreous body replacement materials, this effect can be prevented through the use of certain gels. These gels are gels with a high viscosity/density ratio of >100 mPa cm³/g, preferably >1000 mPa cm³g. Gels according to the present invention of this type make possible a tamponade in the lower eye segment without the development of motion-induced pressure peaks during sudden jerky head movements. This is made possible by the viscosity which—in comparison to that of pure fluorocarbons—is increased, and this increased viscosity counteracts the acceleration forces and prevents the damaging impact of heavy fluids on the retina. In this context, it is a particular advantage that compared to the material properties of pure fluorocarbons, those of the fluorine-containing gels are variable within wide limits.

In contrast to all other ophthalmological preparations on the basis of fluorinated compounds, the implants according to the present invention as ophthalmological preparations for application in the vitreoretinal region can be used not only in procedures that aim at the reattachment of the retina and as a short-term tamponading material. Instead, in addition to the tamponade effect, these implants can also perform other functions of the natural vitreous body. Thus, these implants open up new possibilities, such as treating pathological changes in the vitreoretinal region or suppressing morbid processes which may lead to a permanent injury to the retina, e.g., injury to the Müller cells. For this purpose, the preparations can be designed to ensure that they combine different and even opposite properties in such a way that these can be activated in one single treatment step. The application potential of the gels is enhanced and expanded by the fluorocarbons that are contained in the gels which, as is well known, have special properties, such as anti-inflammatory and anti-gas properties.

The other known properties of fluorine-containing compounds that are of advantage when such compounds are applied as ophthalmological preparations are maintained or even enhanced in the implants according to the present invention, thus, for example, the possibility of a laser treatment, the tamponade properties, and the solubility of active ingredients. The implants according to the present invention can be removed from the bodily orifices using conventional methods, for example, vitrectomy.

The fluorine-containing implants according to the present invention can also be used as intraocular lenses. For this particular purpose, it is recommended that highly transparent gels be used which have an especially high viscosity/density ratio; this can be achieved in particular through the use of oligomer R_FF_H compounds as the discontinuous phase, such as has been described in the European Patent No. EP-A 545 174. In addition, the refractive index of the gels used should be adjusted to a range from 1.334 to 1.338, which can be implemented, for example, by using the following compounds:

The implants according to the present invention can be used instead of the artificial intraocular lenses made of silicone, PMMA, or acrylic that are normally used for cataract operations. After opening the capsular sac and removing the cloudy natural lens using conventionally known methods, the implant material is injected, ensuring that the entire capsular sac is completely filled with it. The implant takes over the complete function of the natural lens, i.e., in spite of the cataract operation, the accommodative capacity of the lens is maintained. Due to the forces that are continuously acting on the implant, the mechanical long-term stability is of very special importance in this particular application.

The implants according to the present invention can also be used to temporarily seal off bodily orifices and to temporarily separate tissue parts, for example, in applications in which the implants are used as expanders, or to stimulate the growth of bone. In dentistry, the implant according to the present invention can be used in particular to temporarily fill extraction cavities in the jaw bone and to expand tissue. In addition, it can be used in orthopedic medicine as a biocompatible lubricating film for joints and joint prostheses. After inserting the implant material into the extraction cavities, these cavities are encapsulated by sewing together the surrounding tissue. This prevents leakage of the gel-like implant.

 

Claim 1 of 16 Claims

1. A plastically deformable implant for insertion into bodily orifices of a human or animal body, the implant formed by a gel which is not sealed and is directly introduced into a natural or artificially created bodily opening, with the gel having a polyaphron structure and comprising a fluorocarbon selected from the group consisting of perfluorophenanthrene, C₆F₁₃C₈H₁₇ and (C₆F₁₃C₂H₄)₃, further comprising water, and a minimum of one fluorinated surface-active agent of the general formula R_F-F_pol, wherein:

R_F stands for linear or branched perfluoroalkyl groups with more than 5 carbon atoms;

R_pol stands for a polar hydrocarbon residue with a minimum of one functional group which is selected from the group consisting of CO—NH(R), CO—N(R)₂, COO—, COOR, SO₃—, SO₂N(R)₂, CH₂—O—R, PO₂H, and PO₃H (R=alkyl); and

the surface-active agent has a molecular weight of >400 g/mol, a surface tension in aqueous solution of <30 mN/m, an interfacial tension in aqueous solution with respect to the fluorocarbon of <25 mN/m, and a concentration of <0.3%.
 

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