Antimicrobial gas impregnating devices and methods

Abstract

A nitric oxide gas-releasing conduit configured for surgical implantation through a patient's tympanic membrane. The nitric oxide gas-releasing conduit comprises a gas-permeable cured resin material configured for releasably sequestering therein gas. The gas-permeable cured resin material is charged with nitric oxide gas. The nitric oxide gas-releasing conduit may be optionally coated with an antimicrobial gas-releasing composition. The gas-releasing coating composition may be configured to release nitric oxide.

Claims

1. An antimicrobial gas-releasing conduit comprising an elongate hollow tube that is sufficiently flexible to be implantable within a patient, which tube comprises a gas-permeable cured resin material having a porous microstructure, wherein the porous microstructure of said gas-permeable cured resin material is saturated throughout with antimicrobial gaseous nitric oxide and is devoid of an antimicrobial gas-releasing composition, the conduit being configured such that the gaseous nitric oxide is releasably sequestered in said porous microstructure and thus is released, after implantation of the conduit within a patient, so as to diffuse about the tube and provide antimicrobial gas to the surrounding tissue.

2. The antimicrobial gas-releasing conduit of claim 1, wherein said gas-permeable cured resin material is selected from the group consisting of curable silicones, polyvinyl acetates, acrylonitrile-butadiene-styrene copolymer rubber and polyurethanes.

3. The antimicrobial gas-releasing conduit of claim 1, wherein said elongate hollow tube, that is sufficiently flexible to be implantable within a patient, is an ear-draining tube.

4. The antimicrobial gas-releasing conduit of claim 1, wherein said elongate hollow tube, that is sufficiently flexible to be implantable within a patient, is a tympanostomy tube.

5. The antimicrobial gas-releasing conduit of claim 1, wherein said elongate hollow tube, that is sufficiently flexible to be implantable within a patient, is a myringotomy tube.

6. A method for treating otitis media in a patient comprising implanting the antimicrobial gas-releasing conduit of claim 1 in a patient's tympanic membrane.

7. The method of claim 6, wherein said antimicrobial gas-releasing conduit is a tympanostomy tube.

8. The method of claim 6, wherein said antimicrobial gas-releasing conduit is a myringotomy tube.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be described in conjunction with reference to the following drawings, in which:

(2) FIG. 1(a) is a chart showing the effects of gNO released from gNO-charged vent tubes on the proliferation of Streptococcus pyogenes. FIG. 1(b) is a chart showing the effects of released gNO on survival of S. pyogenes;

(3) FIG. 2(a) is a chart showing the effects of gNO released from gNO-charged vent tubes on the proliferation of Streptococcus pneumonia. FIG. 2(b) is a chart showing the effects of released gNO on survival of S. pneumonia;

(4) FIG. 3(a) is a chart showing the effects of gNO released from gNO-charged vent tubes on the proliferation of Moraxella catarrhalis. FIG. 3(b) is a chart showing the effects of released gNO on survival of M. catarrhalis;

(5) FIG. 4(a) is a chart showing the effects of gNO released from gNO-charged vent tubes on the proliferation of Haemophilus influenzae. FIG. 4(b) is a chart showing the effects of released gNO on survival of H. influenzae;

(6) FIG. 5(a) is a chart showing the effects of gNO released from gNO-charged vent tubes on the proliferation of methicillin-resistant Staphylococcus aureus. FIG. 5(b) is a chart showing the effects of released gNO on survival of S. aureus; and

(7) FIG. 6 is a chart showing the effects of gNO released from gNO-charged silicon vent tubes and gNO-charged polytetrafluoroethylene vent tubes on the proliferation of Staphylococcus aureus.

(8) FIG. 7 provides a schematic illustration of an embodiment of the presently described conduit, wherein a hollow tube 1 can be coated on the outer surface 2 with a coating comprising antimicrobial gas-releasing coating.

DETAILED DESCRIPTION

(9) Certain exemplary embodiments of the present invention are directed to antimicrobial conduit structures configured for long-term installation through the tympanic membranes into the inner ear cavities for the purpose of draining fluids therefrom. Such conduit structures are exemplified by tympanostomy tubes, myringotomy ventilation tubes and the like, and will be generally referred to from hereon in as “tympanostomy tubes”. The antimicrobial tympanostomy tubes generally comprise materials that are controllably permeatable with gases selected for their antimicrobial properties.

(10) The antimicrobial tympanostomy tubes are characterized by their biological compatibility with otologic tissue associated with the tympanic membrane and middle ear tissues, and generally comprise polymeric materials exemplified by resins which after forming and curing, are microporous and have the requisite high gas permeability properties needed to prepare the antimicrobial tympanostomy tubes. These resins are suitably characterized by an ability for infiltratably sequestering selected permeating antimicrobial gases, and then controllably releasing the antimicrobial gases over extended periods of time. Suitable resins are exemplified by curable silicones, polyvinyl acetates, thermoplastic elastomers, acrylonitrile-butadiene-styrene copolymer rubber, polyurethanes and the like. In certain embodiments, curable silicone resins are preferred for the manufacture of the antimicrobial tympostomy tubes due to their molecular structure which provides good flexibility both microscopically and macroscopically, and high gas permeability rates. Table 1 illustrates the gas permeability of silicone resins in comparison with other types of materials suitable for such tubular manufacture.

(11) The geometries of the antimicrobial tympanostomy tubes are generally cylindrical and may simply comprise elongate hollow conduits having the same diameter extending from end to end, or alternatively may comprise elaborate configurations that may additionally include abrupt diameter changes and odd shaped flanges.

(12) TABLE-US-00001 TABLE 1 Gas permeation through selected materials (cc/0.001 in/100.0 in.sup.2/24 h at 22.8° C., 0% relative humidity, ASTM D-1434)*. Permeating gas Tubular material O.sub.2 CO.sub.2 Silicone 50,000 300,000 Urethanes 200 3,000 Epoxies 5-10 8 Fluorocarbons 7-15 15-30 Nylon 2.6 4.7 Polybutylene 385 825 Polycarbonate 258 775 Cellulose acetate 23 105 *adapted from; (1) Packaging Encyclopedia 1988 Vol. 33 No. 5, pp. 54-55, and Machine Design, May 25, 1967, p. 192.

(13) Gaseous nitric oxide (gNO) is an intermediary compound produced during the normal functioning of numerous biochemical pathways in many biological systems including humans. gNO is known to those skilled in these arts as a key biological messenger signaling compound that plays key roles in many biological processes. Recent evidence (e.g., Ghaffari et al., 2005 Nitric Oxide 14: 21-29) suggests that gNO plays an important role in mammalian host defense against infection and regulates wound healing and angiogenesis. In particular, topical applications of exogenous gNO at 200 ppm for extended periods of time inhibited and prevented the growth of a wide range of microbial pathogens Staphylococcus aureus, Escherichia coli, Group B Streptococcus, Pseudomonas aeruginosa, and Candida albicans, without any cytotoxic effects on cultured human dermal fibroblasts. Furthermore, McMullin et al. (2005, Respir. Care 5:1451-1456) demonstrated that exogenous gNO at a concentration of 200 ppm could clear nosocomial pneumonia caused by microbial pathogens such as S. aureus and P. aeruginosa, in about 6 hours. Accordingly, gNO is a particularly suitable antimicrobial gas for saturatingly permeating tympanostomy tubes comprising gas-permeable polymeric materials.

(14) The antimicrobial typanostomy tubes described herein may be produced by first casting a desired tubular configuration with a selected suitable resin using conventional methods known to those skilled in these arts. It is suitable to process the tubes into their final configuration and finish after which, the tubes are placed into a sealable chamber. The chamber is then saturated with a selected antimicrobial gas, exemplified by gNO, for a selected period of time suitable for infiltratingly saturating the tympanostomy tubes whereby the gas is sequestered into and within the resin structure comprising the tubes thereby by providing antimicrobial properties to the tympanostomy tubes. Excess gNO is then evacuated from the chamber after which, the gNO-loaded tympanostomy tubes are removed and individually packaged into gas-impermable containers. In certain embodiments, the chamber may be infiltrated with a semi-porous sealing gaseous material configured to at least partially cross-link with the outer surfaces antimicrobial tympanostomy tubes thereby enabling a further extension of time duration for release of the sequestered gas about the antimicrobial tympanostomy tubes. The chamber may be controllably infiltrated with the semi-porous sealing gaseous material concurrently with evacuation of the antimicrobial gas from the chamber or alternatively, the antimicrobial gas may be completely evacuated from the chamber after which, the semi-porous sealing gaseous material may be infiltrated into the chamber. Excess semi-porous sealing gaseous material is then evacuated from the chamber after which, the gNO-loaded tympanostomy tubes are removed and individually packaged into gas-impermable containers.

(15) In certain embodiments, gNO-sequestering chelating agents may be incorporated into a suitable selected resin material prior to forming tympanostomy tubes. Suitable gNO-sequestering chelating agents are exemplified by sodium nitrite, nitrosothiols, dipyridoxyl chelating agents, L-arginine, organic nitrates, organic nitrites, thionitrates, thionitrites, N-oxo-N-nitrosamines, N-nitrosamines, sydnonimines, 2-hydroxyimino-5-nitroalkenamides, diazenium diolates, oxatriazolium compounds, oximes, syndomines, molsidomine and derivatives thereof, pirsidomine, furoxanes, nitrosonium salts, and the like, and combinations thereof. A suitable amount of a selected gNO-sequestering chelating agent is placed into a sealable chamber which is then saturated with gNO. A suitable amount of the gNO-loaded chelating agent is then thoroughly intermixed and commingled with a selected resin material after which, the resin material is processed into tympanostomy tubes using methods known to those skilled in these arts. The tympanostomy tubes comprising interspersed therethrough gNO-loaded chelating agent, are then sealably packaged into gas-impermeable containers.

(16) In certain embodiments, an antimicrobial gas-releasing coating may be provided onto the outer surfaces, and optionally on to the inner surfaces, of NO gas-permeated tympanostomy tubes. For example, NO gas-releasing coatings can be provided by applying to the NO gas-permeated tympanostomy tubes, a composition comprising a N.sub.2O.sub.2.sup.− functional group that will bind to the cured resin material comprising the tympanostomy tubes. Suitable exemplary compounds comprising N.sub.2O.sub.2.sup.− functional groups are disclosed in U.S. Pat. No. 5,525,357. Other suitable exemplary coating compositions for providing NO gas-releasing coatings onto NO gas-permeated tympanostomy tubes include among others, NO-releasing intramolecular salts known as zwitterions having the general formula 2RN[N(O)NO.sup.−(CH.sub.2),NH.sub.2.sup.+R′, and S-nitrosothiols.

(17) The antimicrobial gas-permeated tympanostomy tubes described herein can be surgically implanted using well-known procedures, through a patient's tympanic membrane such that one end of the tympanostomy tube extends into the patient's middle ear cavity while the other end of the tube extends through the tympanic membrane into the outer ear cavity. The antimicrobial gas sequestered within the resin material comprising the implanted tympanostomy tube will slowly diffuse from and about the tube thereby alleviating and/or preventing post-operative microbial infections normally associated with these types of tubes and without adverse toxicology reactions exemplified by irritation and inflammation, of otologic tissues. Contact with moisture will expedite the release of gNO sequestered within and coated onto the antimicrobial tympanostomy tubes. Furthermore, provision of NO gas-releasing coatings on the outer surfaces of the tubes, and optionally on their inner surfaces, will inhibit and prevent the formation of biofilms thereon.

EXAMPLES

Example 1

(18) A plurality of vent tubes comprising a polytetrafluoroethylene (PTFE) substrate (1.25 mm Sheehy collar buttons, catalog number 23-40300; Inovotec International Inc., Jacksonville, Fla., USA) were placed into gas-ventable Petri dishes. A suitable cather was used to connect the Petri dishes to a manifold connected to a cylinder containing gNO manufactured by Airgas (Chicago Ill., USA). The manifold was provided with a gas flow controller adjusted to deliver 22,000 ppm of gNO to each Petri dish at a flow rate of 30 cc min.sup.−1 for a period of 22 h. After the gNO-charging process was completed, the gNO-charged PTFE vent tubes were stored in gas-impermeable containers. All handling of the vent tubes after the gNO-charging process was completed, was done using aseptic techniques.

(19) Stock cultures of Streptococcus pyogenes (ATCC#51878), Streptococcus pneumonia (ATCC#10015), Moraxella catarrhalis (ATCC#25240), and Haemophilus influenzae (ATCC#35540) were maintained on nutrient agar. Broth cultures of each microorganism were prepared by inoculating a test tube containing 10 mL of Brain Heart infusion broth with a colony picked from a stock culture plate. The inoculated test tubes were cultured for 12 h to 18 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2. The cultures were then diluted with fresh Brain Heart Infusion broth to an OD.sub.600 reading of 0.5. Each broth culture thus prepared contained 10.sup.7 to 10.sup.8 colony-forming units (CFU) mL.sup.−1. All handling of the microbial cultures was done using aseptic techniques.

(20) All wells in a 24-well plate received 1 mL of broth culture of a selected microorganism prepared as described above. Each of 12 wells received 1 gNO-charged PTFE vent tube prepared as described above. Each of the remaining 12 wells received 1 sterile PTFE vent tube as supplied by the manufacturer. The tubes were incubated in the broth cultures contained in the 24-well plates for about 1 min after which, each tube was removed from its broth culture and transferred to a quadrant in a quadrant Petri dish. The quadrant Petri dishes were maintained for 7 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2. Individual tubes were removed from the quadrant Petri dishes after 3 h and 7 h of incubation, and were each placed into a microtubes containing 30 μL of sterile phosphate-buffered saline (PBS) and vortexed. The PBS was then pipetted onto a nutrient agar plate and spread across the agar surface. The inoculated plates were then incubated for 24 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2 after which, the plates were removed and the numbers of CFU units appearing thereon were quantified. The results are shown in FIGS. 1-4. The data show that exposure of S. pyogenes (FIGS. 1(a) and 1(b)), S. pneumonia (FIGS. 2(a) and 2(b)), M. catarrhalis (FIGS. 3(a) and 3(b)), and H. influenzae (FIGS. 4(a) and 4(b)) to gNO-charged vent tubes reduced the proliferation of each of the microbial species tested.

Example 2

(21) A plurality of vent tubes comprising a PTFE substrate (Armstrong Beveled vent tube Grommet-type 1.14 mm I.D Fluorplastic, from Gyrus ACMI, catalog number 140242; Inovotec International Inc., Jacksonville, Fla., USA) were placed into gas-ventable Petri dishes. A suitable cather was used to connect the Petri dishes to a manifold connected to a cylinder containing gNO manufactured by Airgas (Chicago Ill., USA). The manifold was provided with a gas flow controller adjusted to deliver 22,000 ppm of gNO to each Petri dish at a flow rate of 30 cc min.sup.−1 for a period of 22 h. After the gNO-charging process was completed, the gNO-charged PTFE vent tubes were stored in gas-impermeable containers. All handling of the vent tubes after the gNO-charging process was completed, was done using aseptic techniques.

(22) A stock culture of methicillin-resistant Staphylococcus aureus (MRSA; ATCC#700698), was maintained on nutrient agar. MSRA is a S. aureus strain that is known to be resistant to a number of broad-spectrum antibiotics commonly used to treat it. MRSA broth cultures were prepared by inoculating a plurality of test tubes containing 10 mL of Brain Heart Infusion broth with a colony picked from a stock culture plate. The inoculated test tubes were cultured for 12 h to 18 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2. The cultures were then diluted with fresh Brain Heart Infusion broth to an OD.sub.600 reading of 0.5. Each broth culture thus prepared contained about 10.sup.5 CFU mL.sup.−1. All handling of the microbial cultures was done using aseptic techniques.

(23) All wells in a 24-well plate received 1 mL of a MSRA broth culture prepared as described above. Each of 12 wells received 1 gNO-charged PTFE vent tube prepared as described above. Each of the remaining 12 wells received 1 sterile PTFE vent tube as supplied by the manufacturer. The tubes were incubated in the broth cultures contained in the 24-well plates for about 1 min after which, each tube was removed from its broth culture and transferred to a quadrant in a quadrant Petri dish. The quadrant Petri dishes were maintained for 7 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2. Individual tubes were removed from the quadrant Petri dishes after 3 h and 7 h of incubation, and were each placed into a microtubes containing 30 μL of sterile phosphate-buffered saline (PBS) and vortexed. The PBS was then pipetted onto a nutrient agar plate and spread across the agar surface. The inoculated plates were then incubated for 24 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2 after which, the plates were removed and the numbers of CFU units appearing thereon were quantified. The results are shown in FIG. The data show that exposure of methicillin-resistant Staphylococcus aureus (FIGS. 5(a) and 5(b)) to gNO-charged vent tubes reduced the proliferation of this microbial species.

Example 3

(24) A first plurality of vent tubes comprising a silicon substrate (T-Tube, Silicon Myringotomy Tube, 23-50600; Invotec International Inc., Jacksonville, Fla., US) and a second plurality of vent tubes a PTFE substrate (Sheehy Collar Button, Fluoroplastic Myringotomy Tube, 23-40300; Inovotec International Inc., Jacksonville, Fla., USA) were placed into gas-ventable Petri dishes. A suitable cather was used to connect the Petri dishes to a manifold connected to a cylinder containing gNO manufactured by Airgas (Chicago Ill., USA). The manifold was provided with a gas flow controller adjusted to deliver 22,000 ppm of gNO to each Petri dish at a flow rate of 30 cc min.sup.−1 for a period of 22 h. After the gNO-charging process was completed, the gNO-charged silicon vent tubes and PTFE vent tubes were stored in gas-impermeable containers. All handling of the vent tubes after the gNO-charging process was completed, was done using aseptic techniques.

(25) A stock culture of a Staphylococcus aureus (ATCC#25923), was maintained on nutrient agar. S. aureus broth cultures were prepared by inoculating a plurality of test tubes containing 10 mL of Brain Heart Infusion broth with a colony picked from a stock culture plate. The inoculated test tubes were cultured for 12 h to 18 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2. The cultures were then diluted with fresh Brain Heart Infusion broth to an OD.sub.600 reading of 0.5. Each broth culture thus prepared contained about 10.sup.5 CFU mL.sup.−1. All handling of the microbial cultures was done using aseptic techniques.

(26) All wells in a 24-well plate received 1 mL of a S. aureus broth culture prepared as described above. Each of 12 wells received 1 gNO-charged PTFE vent tube prepared as described above. Each of the remaining 12 wells received 1 sterile PTFE vent tube as supplied by the manufacturer. The tubes were incubated in the broth cultures contained in the 24-well plates for about 1 min after which, each tube was removed from its broth culture and transferred to a quadrant in a quadrant Petri dish. The quadrant Petri dishes were maintained for 7 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2. Individual tubes were removed from the quadrant Petri dishes after 3 h and 7 h of incubation, and were each placed into a microtubes containing 30 μL of sterile phosphate-buffered saline (PBS) and vortexed. The PBS was then pipetted onto a nutrient agar plate and spread across the agar surface. The inoculated plates were then incubated for 24 h at 37° C. in an incubater provided with an atmosphere containing about 5% CO.sub.2 after which, the plates were removed and the numbers of CFU units appearing thereon were quantified. The results are shown in FIG. The data show that exposure of S. aureus ATCC#25923 to gNO-charged vent tubes reduced the proliferation of this microbial species on silicon-based vent tubes and on PTFE vent tubes (FIG. 6).

(27) While this invention has been described with respect to the exemplary embodiments, it is to be understood that various alterations and modifications can be made to the configurations and shapes of the antimicrobial tympanostomy tubes, and to methods for saturatingly infiltrating the tubes with a selected antimicrobial gas within the scope of this invention.

(28) Further, the foregoing is merely intended to illustrate various embodiments of the present invention. The specific modifications or characteristics discussed above are not to be construed as limitations on the scope of the invention. It will be apparent to one skilled in the art that various equivalents, changes, and modifications may be made without departing from the scope of the invention, and it is understood that such equivalent embodiments are to be included herein. All references cited herein are incorporated by reference as if fully set forth herein.