Drug – bio-affecting and body treating compositions – Inorganic active ingredient containing – Heavy metal or compound thereof
Reexamination Certificate
2002-04-23
2004-04-20
Pak, John (Department: 1616)
Drug, bio-affecting and body treating compositions
Inorganic active ingredient containing
Heavy metal or compound thereof
C424S405000, C424S489000, C424S600000, C424S604000, C424S617000, C424S620000, C424S630000, C424S639000, C424S641000, C424S646000, C424S649000, C424S650000, C424S651000, C424S652000, C424S653000, C424S654000, C424S655000, C424S682000, C427S250000, C106S001050, C106S001130, C106S001140, C106S001150, C106S001180, C106S001190, C106S001210, C148S513000, C148S537000, C148S559000, C148S678000, C148S679000, C514S951000
Reexamination Certificate
active
06723350
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to water swellable or lubricious, antimicrobial and anti-inflammatory coatings for substrates such as medical devices, and methods of preparing same.
BACKGROUND OF THE INVENTION
To improve the lubricity of medical devices such as catheters, probes or feeding tubes which are inserted into a human or animal body cavity, coatings have been developed. Jelly-like coatings have been smeared onto the surface of medical devices before insertion into body cavities. However, such coatings are easily dislodged from the medical device, causing discomfort on removal. Furthermore, the jelly-like coatings can raise an additional risk of infection.
Another approach to reducing the coefficient of friction of medical devices has been to use oil, silicone or polymeric materials which are coated with such materials as Teflon®. These approaches provided limited lubricity, or introduced possible sources of infection.
Typical microorganisms involved in infection arising from the use of medical devices include
Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli
and
Proteus mirabilis,
fungi and yeast such as
Aspergillus fumigatus
and
Candida albicans.
Numerous lubricious polymeric coatings are known for use on medical devices and other substrates. These coatings typically use a hydrophilic polymers which bind to the surface of the substrate and exhibit slipperiness (lubricity) on wetting. However, as a source for infection, these coatings can still be problematic.
There is still a need for an effective lubricious coating for substrates, which also provides antimicrobial protection.
SUMMARY OF THE INVENTION
The present invention provides water swellable, and most preferably lubricious, coatings useful for a wide variety of substrates. The coatings contain a water swellable, preferably lubricious, polymer, which provides lubricity on wetting, and a nanocrystalline antimicrobial powder formed with atomic disorder, which acts as both an antimicrobial agent and an anti-inflammatory agent, without interfering with the enhanced lubricity. It is particularly surprising and advantageous to discover that the inclusion of the atomically disordered antimicrobial metal component of the coatings of the present invention adheres well to the substrates and does not interfere with the lubricity properties of the final, dried coating. The antimicrobial metal component provides not only antimicrobial activity, but also anti-inflammatory activity, when wetted. It is also surprising that the coatings of the invention, which are formed from solutions of the polymer and the metal powder and then dried, continue to provide both antimicrobial and anti-inflammatory activity when rehydrated for actual use. The initial hydration of the polymer and metal powder to form the coating does not deactivate the metal powder. Importantly, the antimicrobial and anti-inflammatory activities are also found to be sustainable, that is not merely instantaneous, but continuing over an extended time period such as hours, days or weeks. Also important is the discovery that the coatings of the present invention provide a significant reduction to biofilm formation on the coated substrates.
Nanocrystalline powders of the antimicrobial metal, most preferably a noble metal, formed with atomic disorder can be prepared either as nanocrystalline coatings on powdered substrates such as chitin, or may be prepared as nanocrystalline coatings on a substrate such as a silicon wafer, and then scraped off as a nanocrystalline powder. In either case, the coatings are formed with atomic disorder using such techniques as physical vapour deposition or modified inert gas condensation as taught in prior patent applications WO 93/23092, published Nov. 25, 1993, and WO 95/13704, published May 26, 1995, both of which name Burrell et al., as inventors. Alternatively, to impart atomic disorder, a fine grained or nanocrystalline powder of the antimicrobial or noble metal may be cold worked to impart atomic disorder, as disclosed in prior patent application WO 93/23092. Still alternatively, the metal powders may be formed in accordance with the novel powder manufacturing process disclosed herein.
Broadly stated, the invention provides a method of coating a substrate comprising forming a liquid medium containing a water swellable polymer (preferably a lubricious polymer), a solvent and a powder of one or more antimicrobial metals formed with atomic disorder; and coating the substrate from the liquid medium to provide a gel coating that adheres to the substrate, and becomes antimicrobial and anti-inflammatory when wet.
In another broad aspect, the invention provides a substrate coated with a water swellable gel coating, comprising a substrate, and a water swellable gel coating adhering to the substrate, wherein the coating includes a water swellable polymer and one or more antimicrobial metals formed with atomic disorder, and wherein the gel coating becomes antimicrobial and anti-inflammatory when wet.
In yet another broad aspect, the invention provides a kit for coating a substrate comprising a water swellable polymer; a powder of one or more antimicrobial metals formed with atomic disorder; and optionally a solvent for the water swellable polymer.
The lubricious polymer is preferably a hydrophilic polymer in powder form, most preferably one or more of carboxymethyl cellulose, polyvinyl alcohol and alginate. The antimicrobial metal is preferably one or more of Ag, Au, Pd or Pt (most preferably Ag), in a nanocrystalline powder form (grain size less than 100 nm, more preferably less than 50 nm, more preferably less than 40 nm, and most preferably less than 25 nm), and with particulate size preferably less than 100 &mgr;m, more preferably less than 40 &mgr;m, and most preferably less than 10 &mgr;m).
The invention also broadly provides a method of forming a metal powder comprising sputtering a metal coating in a sputtering apparatus equipped to sputter onto a moving or rotating surface, and then scraping the coating off the moving or rotating surface with one or more scrapers to form a metal powder.
As used herein and in the claims, the terms and phrases set out below have the meanings which follow.
“Metal” or “metals” includes one or more metals whether in the form of substantially pure metals, alloys or compounds such as oxides, nitrides, borides, sulphides, halides or hydrides.
“Antimicrobial metals” are silver, gold, platinum, palladium, iridium, zinc, copper, tin, antimony, bismuth, or mixtures of these metals with same or other metals, silver, gold, platinum and palladium being preferred, and silver being most preferred.
“Noble metals” are silver, gold, platinum and palladium, or mixtures of such metals with same or other metals, with silver metal being the most preferred.
“Antimicrobial effect” means that atoms, ions, molecules or clusters of the antimicrobial or noble metal are released into the electrolyte which the coating contacts in concentration sufficient to inhibit microbial growth on and in the vicinity of the coating. The most common methods of measuring an antimicrobial effect are a zone of inhibition test (which indicates an inhibitory effect, whether microbiostatic or microbiocidal) or a logarithmic reduction test (which indicates a microbiocidal effect). In a zone of inhibition test (ZOI) the material to be tested is placed on a bacterial lawn (or a lawn of other microbial species) and incubated. A relatively small or no ZOI (ex. less than 1 mm) indicates a non-useful antimicrobial effect, while a larger ZOI (ex. greater than 5 mm) indicates a highly useful antimicrobial effect. The ZOI is generally reported as a corrected zone of inhibition (CZOI), wherein the size of the test sample is subtracted from the zone. A logarithmic reduction test in viable bacteria is a quantitative measure of the efficacy of an antibacterial treatment; for example, a 5 log reduction means a reduction in the number of microorganisms by 100,000-fold (e.g., if a product contained 100,000
Bowlby Leonard Salvin
Burrell Robert Edward
Cholowski Walter Carlton Theodore
Field David James
Moxham Peter Howard
Fish & Richardson P.C.
Nucryst Pharmaceuticals Corp.
Pak John
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