Patent Application
20060260956
The present invention relates to polymeric articles having reduced interaction with packaging materials, methods for producing such articles, and methods for preventing or reducing interaction between such articles and their packaging materials. In particular, the present invention relates to ophthalmic devices that are modified to have reduced interaction with packaging materials, methods for producing such ophthalmic devices, and methods for preventing or reducing interaction between such ophthalmic devices and their packaging materials.
Packaging containers are often made of polymeric materials. These containers also are often used to contain products made of polymers, which tend to stick to the containers. For example, ophthalmic devices, such as contact lenses and intraocular lenses (“IOLs”), are commonly contained in packages filled with packaging solution for shipment to points of use. The individual package typically comprises a cavity, which is typically made of a polymeric material and sealed with a lid typically made of a laminated foil. Because the ophthalmic device tends to stick to the package, packaging solutions have been formulated to reduce or prevent device sticking. For this reason, certain surfactants, such as polyvinyl alcohol or poly(alkyleneoxy) surfactants, have been used in the formulation of packaging solutions. However, adding new compounds, including surfactants, in device packaging solution would require regulatory approval. Other challenges encountered in adding a surfactant to a packaging solution, including the possibility of lowering shelf-life and/or adverse reactions during heat sterilization, have further limited the use of surfactants in a packaging solution for the purpose of preventing device sticking.
Therefore, there is a continued need to provide products that do not tend to interact with packaging materials and methods for making such products. In particular, it is very desirable to provide ophthalmic devices that at least have a property of reduced interaction with packaging materials and methods for making such ophthalmic devices.
In general, the present invention provides polymeric articles that have reduced potential for interaction with the packages in which they are contained, and methods for preventing or reducing interaction between the polymeric articles and the packages.
In one aspect, the present invention provides packages and methods for containing or storing ophthalmic devices, which packages and methods provide at least reduced potential for the sticking of such devices to the packages.
In another aspect, the present invention provides a method for preventing or reducing interaction between an ophthalmic device and a package containing the device.
In still another aspect, the method for preventing or reducing interaction between the ophthalmic device and the package comprises oxidizing the ophthalmic device.
In yet another aspect, the method comprises treating the ophthalmic device with an oxygen-containing plasma before disposing the treated device in the package.
In still another aspect, the method further comprises disposing a solution in the package and disposing the device in the solution.
In yet another aspect, the ophthalmic device is a contact lens or an intraocular lens.
Other features and advantages of the present invention will become apparent from the following detailed description and claims.
In general, the present invention provides polymeric articles that have reduced potential for interaction with the packages in which they are contained, and methods for preventing or reducing interaction between the polymeric articles and the packages.
In one aspect, the present invention provides packages and methods for containing or storing ophthalmic devices, which packages and methods provide at least reduced potential for the sticking of such devices to the packages. In another aspect, the packages and the ophthalmic devices comprise polymeric materials.
In another aspect, a method for preventing or reducing interaction between an ophthalmic device and a package comprises oxidizing the ophthalmic device. In still another aspect, the method comprises causing an increase in the oxygen content of the ophthalmic device. In still another aspect, the method comprises treating the ophthalmic device with oxygen-containing plasma.
Base portion 12 can be made of a thermoplastic or thermoset polymeric materials. Non-limiting examples of thermoplastic materials are polyolefins (such as low- and high-density polyethylene and polypropylene), polysulfones, polyethylene terephthalate, polycarbonates, nitrile rubbers, acrylonitrile butadiene styrene (“ABS”) polymers, and polyimides. Non-limiting examples of thermoset polymeric materials are epoxy and phenolic-based polymers. Base portion 12 also can be made of a composite of any of these polymeric materials and compatible reinforcing agents or materials, such as silica or glass fibers. Preferably, base portion 12 is made of polypropylene for its good thermoforming properties and its ability to withstand thermal sterilization. Alternatively, other polymeric materials can be chosen if non-thermal sterilization is used. Base portion 12 can be formed by conventional extrusion or molding processes and has thickness sufficient for withstanding handling of the package.
Cover member 14 is typically made of a metal foil, such as aluminum foil. Alternatively, it can be a laminated multilayered stack of metallic and polymeric materials. Such a multilayered stack can be made by coextrusion of sheets of metallic and polymeric materials, with or without an adhesive between the layers.
In one embodiment, polymeric article 40 is a contact lens and solution 30 is a contact lens storing solution, such as a saline solution, which keeps contact lens 40 in a hydrated state.
Generally, contact lenses in wide use fall into two categories: (1) the hard or rigid gas permeable corneal type lenses formed from materials prepared by polymerization of acrylic esters, such as poly(methyl methacrylate) (PMMA), silicone acrylates, and fluorosilicone methacrylates; and (2) gel, hydrogel, or soft-type lenses that are formulated from polymers having a proportion of hydrophilic repeat units derived from monomers, such as 2-hydroxyethyl methacrylate (“HEMA”), N,N-dimethylacrylamide, or N-vinylpyrrolidone, such that the water content of the lens during use is at least 20% by weight. The term “soft contact lens” generally refers to those contact lenses that readily flex under small amounts of force and return to their original shape when that force is released. In one embodiment, silicone hydrogel soft contact lenses can benefit from a method of the present invention.
Contact lens 40 is treated with an oxygen-containing plasma before being disposed in solution 30 in cavity 16. A treated contact lens of the present invention does not stick to or has reduced potential for sticking to the internal surface of cavity 16 or to the surface of cover member 14 that is adjacent to the contact lens 40. The optical properties, such as light transmission or optical power, of well-treated lenses are not detectably affected by the treatment with oxygen-containing plasma.
In general, polymeric article 40 is treated with oxidizing plasma. In one embodiment, the oxidizing plasma is oxygen-containing plasma, which can be generated in an oxygen-containing atmosphere by a conventional method such as low-pressure electrical discharge, radio-frequency (“RF”) capacitive discharge, RF inductively coupled plasma discharge, microwave-generated plasma discharge, or combinations thereof. A suitable method for the present invention is RF inductively coupled plasma discharge in a low-pressure oxygen-containing atmosphere (such as pressure in the range from about 0.1 Pa to about 1000 Pa), at RF in the range from about 1 MHz to about 100 MHz (such as the commonly used frequency of 13.56 MHz), and at power in the range from about 10 to about 1000 W. The duration of the treatment can be in a range from about 1 second to about 2 hours. Preferably, the treatment duration is sufficient to prevent the sticking of the polymeric article 40 to the internal surface of cavity 16. For example, the treatment duration can be in the range from about 10 seconds to about 1 hour.
The oxygen-containing species of the plasma are derived from an oxygen-containing gas introduced into the plasma chamber, such as oxygen, air, NOx (N2O, NO, N2O3, N2O4, NO2,N2O5, N3O4, NO3), SOx, (SO2, SO3), or a mixture of any of these gases and an inert gas selected from the group consisting of nitrogen, helium, argon, neon, krypton, xenon, and combinations thereof.
Monomer formulation RD-1632 comprising polymerizable dialkyl siloxanes and a polymerizable fluoroalkyl siloxane (Bausch & Lomb Incorporated, Rochester, N.Y. ) was cast into contact lenses in polypropylene molds and cured under ultraviolet (“UV”) light. The lenses were released from the molds using liquid nitrogen.
These lenses were treated with oxygen plasma at a range of treatment times (from 30 seconds to 30 minutes) in a Metroline/IPC 7104 plasma chamber at pressure of about 40 Pa (or 0.3 mm Hg), power of 400 W, and RF of 13.56 MHz. Some lenses were also treated for 30 seconds at the same pressure and RF, but at power of 100 W. The loading for each plasma treatment was 50 lenses on a tray designed to handle lenses, centered on a shelf in the middle of the chamber. After plasma treatment, these lenses were extracted in a bath of isopropanol (“IPA”) for 4 hours, re-hydrated in water, and packaged into polypropylene blister packs in three different fill volumes of aqueous borate buffered saline solution (3.6, 4.2 and 4.7 ml). The packaged lenses were sterilized in steam in an autoclave, for example at a temperature up to, and including, 100° C. The sterilization temperature can be higher if super heated steam is used. However, the sterilization temperature should not be high enough to negatively affect the polymeric article and the package. Alternatively, sterilization can be effect by radiation, such as gamma or e-beam radiation.
Samples of these packages were then randomly opened and inspected for sticking to the blister and/or lidstock. Further chemical and physical characterization on the lenses was conducted using X-Ray photoelectron spectroscopy (“XPS”) and atomic force microscopy (“AFM”). Three lenses from each lot were tested for surface analysis. Following desalination, lenses were cut into quarters and mounted for XPS and AFM analyses with one-quarter posterior side up and one-quarter anterior side up for each technique. Survey and high resolution spectra were obtained for one spot on each lens quarter for XPS.
At all fill levels, the untreated lenses tenaciously stuck to the package (Table 1). There was minimal or no sticking at the fill volumes of 3.6 and 4.2 ml, from 0.5 minute of plasma treatment to 30 minutes of treatment, indicating that a minimal plasma treatment was necessary to prevent this negative phenomena with these fluorosilicone hydrogel lenses. At the highest fill volume (4.7 ml), sticking to the packages decreased with increasing plasma surface treatment time. It is believed that the lens was pushed against the lidstock rather than actually stuck.
Cloud-clarity qualitative ratings of the treated lenses, compared to the untreated control, were maintained up to 15 minutes. At treatment time of 20 minutes, this rating dropped, and at 30 minutes decreased greatly.
The unstuck lenses and their surfaces were characterized using XPS and AFM. The oxygen concentrations found by XPS were higher (and carbon concentrations lower) for all the treated samples compared with the controls (Table 2).
Atomic concentration data obtained from XPS analysis suggests that with increasing plasma treatment time, the carbon concentrations decreased and oxygen concentrations increased up to the twenty-minute treatment time (Table 2). The lenses with the thirty-minute treatment time showed slight increases in carbon and decreases in oxygen from the twenty-minute treatment. This data suggests that the surface was being oxidized with increasing plasma time. It is believed that oxygen is incorporated into the lens surfaces and exists as various oxygen-containing moieties, such as one or more of the groups of hydroxyl, carbonyl, carboxyl, ether, and epoxide.
Roughness data obtained from AFM analyses are shown in Table 3. The untreated, control samples showed low roughness values. AFM images indicated that treatment times from 0.5 minute up to 20 minutes resulted in varying degrees of formation of islands having sizes from a micrometer in diameter to about 20 micrometers in diameter. The lenses treated for thirty minutes showed large islands with space between and wrinkled areas around the islands. These observations were also supported by the large RMS (root means square) roughness values and standard deviations. In general, the surface morphology appeared to trend in these plasma treatment times from a mildly cracked under-treated surface, to a well-treated homogeneous surface similar in morphology to the untreated control to a grossly cracked over-treated surface. Such an over-treated surface rendered the lens cloudy because of the large micrometer-sized cracks. Surface roughness data also suggests such a trend, wherein the RMS roughness initially increases with treatment, then decreases and levels off at 5-15 minutes, then increases again at the treatment times of 20 and 30 minutes.
Notes:
(1)Average
(2)Standard deviation
While specific embodiments of the present invention have been described in the foregoing, it will be appreciated by those skilled in the art that many equivalents, modifications, substitutions, and variations may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.
