Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing
Reexamination Certificate
2001-05-15
2004-03-09
Thornton, Krisanne (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
C422S028000, C422S040000, C526S245000, C526S279000
Reexamination Certificate
active
06702983
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to the surface treatment of medical devices including ophthalmic lenses, stents, implants and catheters. In particular, the present invention is directed to a simple, low cost method of modifying the surface of a medical device to decrease its affinity for bacterial adhesion.
BACKGROUND
Medical devices such as ophthalmic lenses have been investigated for a number of years. Such materials can generally be subdivided into two major classes, namely hydrogels and non-hydrogels. Non-hydrogels do not absorb appreciable amounts of water, whereas hydrogels can absorb and retain water in an equilibrium state.
Those skilled in the art have long recognized that surface characteristics play a major role in biocompatibility. It is known that increasing the hydrophilicity of the contact lens surface improves the wettability of the contact lenses. This in turn is associated with improved wear comfort of contact lenses. Additionally, the surface of the lens can affect the lens's susceptibility to deposition, particularly the deposition of proteins and lipids from the tear fluid during lens wear. Accumulated deposition can cause eye discomfort or even inflammation. In the case of extended wear lenses (i.e. lenses used without daily removal of the lens before sleep), the surface is especially important, since extended wear lenses must be designed for high standards of comfort and biocompatibility over an extended period of time.
Extended-wear lenses also present two added challenges. First, the lenses are typically in continuous contact with the epithelium for between 7 and 30 days. This stands in marked contrast to conventional contact lenses, which are removed from the eye before sleep. Second, because the extended-wear lenses are worn continuously, they are generally not removed for disinfection until the conclusion of the recommended extended-wear period. Thus an improved method for inhibiting bacterial attachment would be a major advance for both conventional and extended-wear contact lenses.
In the area of contact lens wetting/conditioning solutions, it has been found that polyelectrolytes can bind to a lens surface of opposite charge and form polyelectrolyte complexes. Such polyelectrolyte complexes have commercially been demonstrated to give more comfortable lens materials because of the greater adsorption of surface bound water. Examples of materials useful for forming such polyelectrolyte complexes are taught in U.S. Pat. No. 4,321,261 to Ellis et al.; U.S. Pat. No. 4,436,730 to Ellis et al.; U.S. Pat. No. 5,401,327 to Ellis et al.; U.S. Pat. No. 5,405,878 to Ellis et al.; U.S. Pat. No. 5,500,144 to Potini et al.; U.S. Pat. No. 5,604,189 to Zhang et al.; U.S. Pat. No. 5,711,823 to Ellis et al.; U.S. Pat. No. 5,773,396 to Zhang et al.; and U.S. Pat. No. 5,872,086 to Ellis et al.
Bacterial attachment to biomaterial surfaces is believed to be a contributing factor in device-related infection. But the extent to which a given microorganism will attach itself to a given biomaterial has proven difficult to predict. Examples of methods for inhibiting such attachment are taught in U.S. Pat. No. 5,945,153 to Dearnaley; U.S. Pat. No. 5,961,958 to Homola et al.; U.S. Pat. No. 5,980,868 to Homola et al.; U.S. Pat. No. 5,984,905 to Dearnaley; U.S. Pat. No. 6,001,823 to Hultgren et al.; U.S. Pat. No. 6,013,106 to Tweden et al.; and U.S. Pat. No. 6,054,054 to Robertson et al.
For contact lens materials, bacterial attachment to a lens surface can lead to bacterial keratitis, or other potential contact lens related complications such as sterile infiltrates and CLARE (Contact Lens Induced Acute Red Eye). Thus it would be desirable to provide a method for inhibiting attachment of microorganisms to contact lenses.
SUMMARY OF THE INVENTION
This invention provides a method for inhibiting the attachment of microorganisms to the surface of a biomaterial. In accordance with the invention, it has been found that controlling the ionic strength of the solution unexpectedly affects the performance of the cationic cellulosic polymer for inhibiting bacterial attachment. Specifically, it has been found that solutions having an ionic strength of less than about 0.13, preferably less than about 0.10 are notably effective for decreasing bacterial attachment to biomedical materials. The range of useful ionic strengths in accordance with this invention is from about 0.01 to about 0.13, preferably from about 0.05 to about 0.10. In a preferred embodiment, the biomedical material is a contact lens and the cationic polysaccharide is a cationic cellulosic polymer. In a more preferred embodiment, the solution has an ionic strength as defined here of less than about 0.095 and most preferably less than about 0.090. The method of the invention is well suited for use with contact lenses, especially silicone hydrogel contact lenses suitable for continuous wear for about 7 to about 30 days.
In another embodiment, the invention provides a composition for inhibiting the attachment of microorganisms to the surface of a biomaterial. The composition of the invention comprises a cationic polysaccharide in an aqueous solution having an ionic strength as defined herein of less than about 0.13, preferably less than about 0.10, more preferably less than about 0.095 and most preferably less than about 0.090. In a preferred embodiment of the composition, the cationic polysaccharide is a cationic cellulosic polymer.
The surface of the biomaterial is preferably at least slightly anionic prior to the application of the cationic polysaccharide. The mechanism for binding the cationic polysaccharide to the surface of the biomedical device is not critical, provided that the binding strength is sufficient to maintain the surface for the intended use of the biomaterial. As used herein, the terms “bond” and “bind” refer to forming a relatively stable complex or other relatively stable attraction between the surface of a biomedical device and a polysaccharide with or without the addition of a linking agent, and is not limited to a particular mechanism. Thus “binding” may involve covalent bonds, hydrogen bonds, hydrophobic interactions or other molecular interactions that enable the cationic polysaccharide of the invention to form a relatively tenacious surface coating on a biomedical device.
The cationic charge on the cationic polysaccharide may be derived from ammonium groups, quaternary ammonium groups, guanidium groups, sulfonium groups, phosphonium groups, bound transition metals, and other positively charged functional groups.
Examples of methods for providing an anionic surface charge on the biomedical device include: (a) bulk distribution of anionic sites in the biomaterial for example, by polymerization; (b) oxidative surface treatment such as plasma discharge or corona discharge; (c) application of an anionic linking agent; (d) complexation; or (e) a combination of one or more of (a)-(d).
Incorporating monomers containing groups such as carboxylate groups, sulfate groups, sulfonate groups, sulfite groups, phosphate groups, phosphonate groups, and phosphonic groups can provide anionic sites distributed through the bulk of the polymeric substrate material. Methacrylic acid and 2-acrylamido-2-methylpropane sulfonic acid are examples of monomers that are useful for incorporating negatively charged sites into the bulk of the substrate biomaterial.
If the surface of the biomaterial carries a net neutral charge or a net cationic charge, the biomaterial may be treated with an oxidative surface treatment or other surface treatment to present a net anionic charge prior to the treatment with the cationic polysaccharide. Examples of suitable oxidative surface treatments include plasma discharge or corona discharge as taught in U.S. Pat. No. 4,217,038 to Letter; U.S. Pat. No. 4,096,315 to Kubacki; U.S. Pat. No. 4,312,575 to Peyman; U.S. Pat. No. 4,631,435 to Yanighara; and U.S. Pat. Nos. 5,153,072; 5,091,204 and 4,565,083, all to Ratner. Additional examples of plasma surface treatments include subj
Borazjani Roya
Hu Zhenze
Salamone Joseph C.
Bausch & Lomb Incorporated
Furr, Jr. Robert B.
Thornton Krisanne
Vacca Rita D.
LandOfFree
Low ionic strength method and composition for reducing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low ionic strength method and composition for reducing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low ionic strength method and composition for reducing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3207039