Abstract:
Antimicrobial compositions and methods are disclosed. The antimicrobial compositions are particularly useful in providing antimicrobial capability to a wide-range of medical devices. In one aspect, the invention relates to a mild solvent coating using acrylate-type mild solution coating. These compositions include rheological modifiers as necessary. The compositions also include antimicrobial agents, which may be selected from a wide array of agents. Representative antimicrobial agents include cetyl pyridium chloride, cetrimide, alexidine, chlorexidine diacetate, benzalkonium chloride, and o-phthalaldehyde. Additionally, the compositions comprise one or more suitable mild solvents, such as a low molecular weight alcohol, alkane, ketone, and combinations thereof.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. provisional patent application No. 61/118,988, filed Dec. 1, 2008, entitled “Antimicrobial Compositions and Methods for Medical Product Use,” which application is incorporated herein by this reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to antimicrobial compositions and methods for use of those compositions in various medical applications. One of the major challenges of modern medical treatment is control of infection and the spread of microbial organisms. 
         [0003]    One area where this challenge is constantly presented is in infusion therapy of various types. Infusion therapy is one of the most common health care procedures. Hospitalized, home care, and other patients receive fluids, pharmaceuticals, and blood products via a vascular access device inserted into the vascular system. Infusion therapy may be used to treat an infection, provide anesthesia or analgesia, provide nutritional support, treat cancerous growths, maintain blood pressure and heart rhythm, or many other clinically significant uses. 
         [0004]    Infusion therapy is facilitated by a vascular access device. The vascular access device may access a patient&#39;s peripheral or central vasculature. The vascular access device may be indwelling for short term (days), moderate term (weeks), or long term (months to years). The vascular access device may be used for continuous infusion therapy or for intermittent therapy. 
         [0005]    A common vascular access device is a plastic catheter that is inserted into a patient&#39;s vein. The catheter length may vary from a few centimeters for peripheral access to many centimeters for central access. The catheter may be inserted transcutaneously or may be surgically implanted beneath the patient&#39;s skin. The catheter, or any other vascular access device attached thereto, may have a single lumen or multiple lumens for infusion of many fluids simultaneously. 
         [0006]    The vascular access device commonly includes a Luer adapter to which other medical devices may be attached. For example, an administration set may be attached to a vascular access device at one end and an intravenous (IV) bag at the other. The administration set is a fluid conduit for the continuous infusion of fluids and pharmaceuticals. Commonly, an IV access device is a vascular access device that may be attached to another vascular access device, closes the vascular access device, and allows for intermittent infusion or injection of fluids and pharmaceuticals. An IV access device may include a housing and a septum for closing the system. The septum may be opened with a blunt cannula or a male Luer of a medical device. 
         [0007]    When the septum of a vascular access device fails to operate properly or has inadequate design features, certain complications may occur. Complications associated with infusion therapy may cause significant morbidity and even mortality. One significant complication is catheter related blood stream infection (CRBSI). An estimate of 250,000-400,000 cases of central venous catheter (CVC) associated BSIs occur annually in US hospitals. 
         [0008]    Current vascular access devices prevent complications, such as infection resulting in CRBSIs, by providing a septum that functions properly during attachment and/or access of the vascular access device by other medical devices. Septa that function properly will act, in part, as infection barriers between the internal and external environments of the vascular access device during attachment and/or access by other medical devices. By functioning properly as infection barriers, septa minimize CRBSI&#39;s and other complications. 
         [0009]    An IV access device may include a housing and a septum for closing the system. The septum may be opened with a blunt cannula or a male Luer of a medical device. A vascular access device may serve as a nidus of infection, resulting in a disseminated BSI (blood stream infection). This may be caused by failure to regularly flush the device, a non-sterile insertion technique, or by pathogens that enter the fluid flow path through either end of the path subsequent to catheter insertion. When a vascular access device is contaminated, pathogens adhere to the vascular access device, colonize, and form a biofilm. The biofilm is resistant to most biocidal agents and provides a replenishing source for pathogens to enter a patient&#39;s bloodstream and cause a BSI. 
         [0010]    Over the last 35 years, it has been common practice to use a thermoplastic polyurethane solution as the carrier for antimicrobial coating. The solvent is usually tetrahydrofuran (THF), dimethylformamide (DMF), or a blend of both. Because THF can be oxidized very quickly and tends to be very explosive, an expensive explosion-proof coating facility is necessary. The harsh solvents will also attack most of the polymeric materials, including polyurethane, silicone, polyisoprene, butyl rubber, polycarbonate, polyvinyl chloride, PET, and acrylics. Therefore medical devices made with these materials can become distorted and/or form microcracks on their surfaces. Another issue with this coating is that it takes almost 24 hours for the solvent to be completely heat evaporated. Accordingly, conventional technology has persistent problems with processing and performance. 
         [0011]    Another limitation is the availability of suitable antimicrobial agents for use in such coatings. One of the most commonly used antimicrobial agents used in coating medical devices is silver. Silver salts and silver element are well known antimicrobial agents in both the medical surgical industry and general industries. They are usually incorporated into the polymeric bulk material or coated onto the surface of the medical devices by plasma, heat evaporation, electroplating, or by conventional solvent coating technologies. These technologies are tedious, expensive and not environmentally friendly. 
         [0012]    In addition, the performance of silver coating medical devices is mediocre at best. For example, it can take up to 8 hours before the silver ion, ionized from the silver salts or silver element, to reach certain efficacy as an antimicrobial agent. As a result, substantial microbial activity can occur prior to the silver coating even becoming effective. Furthermore, the silver compound or silver element has an unpleasant color, from dark amber to black. 
         [0013]    Accordingly, there is a need in the art for improved compositions for providing antimicrobial capability to medical devices of various types, and particularly devices related to infusion therapy. There is also a need for improved methods of applying such antimicrobial coatings to medical devices. 
       BRIEF SUMMARY OF THE INVENTION 
       [0014]    The present invention has been developed in response to problems and needs in the art that have not yet been fully resolved by currently available antimicrobial compositions and methods. Thus, these compositions and methods are developed to reduce complications, such as the risk and occurrence of CRBSIs, by providing improved antimicrobial compositions and methods. 
         [0015]    In one aspect, the present invention includes a mild solvent acrylate-type coating that has antimicrobial properties. This coating is also suitable for use on medical devices, particularly intravascular access devices like needleless valves of the type described and discussed above. The medical devices to be coated are themselves comprised of polymeric substrates, such as polycarbonate (PC), polyurethane (PU), polyvinyl chloride (PVC), and acrylic. Their surfaces are then coated with the mild solvent acrylate-type coating, which contains an antimicrobial agent uniformly distributed throughout its matrix. The antimicrobial agent is able to diffuse through the matrix and kill microscopic organisms that come in contact with the coating&#39;s surface. 
         [0016]    The formulations of this invention are an acrylate-type mild solvent coatings, which have good adhesion to numerous plastic surfaces (including PC, PU, PVC and acrylic). In some embodiments, the mild solvent is selected from one or more low molecular weight alcohols (e.g., ethanol and isopropanol), alkanes (e.g., pentane and heptanes), ketones (e.g., acetone), and combinations thereof. The solvent generally comprises 40% less of the overall solution. 
         [0017]    In some embodiments, the coating can also be dried at about 60° C. for less than about 10 minutes. In one example, the formulation is comprised of alkyl acrylate or alkyl methacrylate-type polymer as the coating resin in one or more mild solvents (e.g., isopropanol), rheological modifiers, and antimicrobial agents. The nano- or micro-sized particles of the antimicrobial agents are uniformly and permanently distributed throughout the whole coating matrix. 
         [0018]    The coating solution can be sprayed, wiped, dipped, or distributed by using other conventional coating methods to coat a substrate&#39;s surface. In certain embodiments it can then be dried at room temperature or at about 60° C. for about 10 minutes or less. The coatings are generally more efficacious than those of silver element or silver compounds that are commonly used in the IV access devices on the market. The coatings also have a pleasant light color or an even clear color. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    This detailed description of the invention provides additional description of each of the aspects of the invention summarized above. 
         [0020]    As discussed above, the present invention comprises a mild solvent antimicrobial coating. The antibacterial solvent coating comprises an acrylate polymer or copolymer; a rheological modifier; and an antimicrobial agent. Generally the acrylate polymer or copolymer is selected from the group consisting of alkyl acrylates, alkyl methacrylates, alkyl hydroxyl(meth)acrylates, and alkyl methoxycinnamate acrylate. The alkyl group can have a carbon number from 0 to 22 (0 means hydrogen, 1 means methyl, 2 means ethyl, 3 means propyl etc.), but preferably a number from 0 to 6, and more preferably between 0 to 3. 
         [0021]    In the compositions, the rheological modifier is generally selected from the group consisting of organic clay, castor wax, polyamide wax, polyurethane, and fumed silica. The rheological modifier may be present in the amount of from about 0.2% to about 30% of the dry weight of the coating. That is, the weight of the coating once the solvent has evaporated. In certain other embodiments, the rheological modifier is present in the amount of from about 0.2% to about 20% of the dry weight of the coating. In certain other embodiments, the rheological modifier is present in the amount of from about 0.2% to about 10% of the dry weight of the coating. 
         [0022]    The antimicrobial agent is generally selected from the group consisting of aldehydes, anilides, biguanides, silver, silver compounds, bis-pheonols, and quaternary ammonium compounds. In certain instances, the antimicrobial agent is preferred to be selected from the group consisting of cetyl pyridium chloride, cetrimide, benzalkonium chlorides, alexidine, chlorexidine diacetate, and o-phthalaldehyde. 
         [0023]    The antimicrobial agent may be present in the composition in the amount of from about 0.5% to about 50% of the dry weight of the coating. In other embodiments, the antimicrobial agent is present in the composition in the amount of from about 0.5% to about 30% of the dry weight of the coating. In certain other embodiments, the antimicrobial agent is present in the amount of from about 0.5% to about 20% of the dry weight of the coating. Finally, in certain preferred embodiments, the antimicrobial agent is present in the amount of from about 0.5% to about 7.0% of the dry weight of the coating. 
         [0024]    As discussed above, in some embodiments, the formulations of this invention are mixed in a mild solvent before being applied to a medical device. While the mild solvent may comprise any solvent that is capable of dissolving the described acrylate polymer or copolymer, some suitable examples of the mild solvent include one or more low molecular weight alcohols, alkanes, ketones, and combinations thereof. Some examples of suitable low molecular weight alcohols comprise methanol, ethanol, propanol, isopropanol, and butanol. Because methanol evaporates relatively quickly, however, methanol may not be preferred in all embodiments. Instead, in some currently preferred embodiments, the alcohol comprises ethanol or isopropanol. Some suitable examples of suitable low molecular weight alkanes comprise pentane, hexane, heptane, and isomers thereof. Indeed, in some preferred embodiments the mild solvent comprises hexane or heptanes. Additionally, an example of a suitable low molecular weight ketone is acetone. However, in embodiments in which the solvent comprises acetone, the solvent preferably also comprises another mild solvent, such as an alcohol or an alkane. 
         [0025]    The aforementioned solvents may be preferred for several reasons. In one example, the aforementioned solvents are gentler on medical devices that comprise PC, PU, PVC, or another similar material than are some conventional solvents (e.g., tetrahydrofuran (THF) and dimethyl formaldehyde (DMF)). In other words, the aforementioned solvents are less likely than some conventional solvents (e.g., THF and DMF) to distort or crack the medical devices to which they are applied. 
         [0026]    In another, example, the aforementioned mild solvents may evaporate more quickly than other conventional solvents. Accordingly, the coating process is faster where aforementioned mild solvents are used. In still another example, the described mild solvent are less toxic and less explosive than certain other conventional solvents (e.g., THF and DMF). 
         [0027]    As with the other disclosed compositions, the antimicrobial agents, which are uniformly distributed in the polymer matrix, gradually diffuse out of the matrix when the matrix is softened by the IV fluids or other types of fluids, and kill the microbes that come into contact with the coating surface. 
         [0028]    The data from Table 1 shows the effectiveness of various compositions employing various antimicrobial agents. Each composition includes an acrylate polymer or copolymer, a rheological modifier, isopropanol, and the listed antimicrobial agent. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 The Contact Kill (%) of  S. epidermidis  by using different antimicrobial 
               
               
                 agents in the formulations. 
               
             
          
           
               
                   
                 Contact kill 
                 Contact Kill 
                   
               
               
                   
                 (%) 
                 (%) 
                 Contact Kill 
               
               
                   
                 
                   S. 
                 
                 
                   S. 
                 
                 (%) 
               
               
                   
                 
                   Epidermidis 
                 
                 
                   Epidermidis 
                 
                 
                   S. Epidermidis 
                 
               
               
                 Antimicrobial Agents 
                 1 min. 
                 1 hr. 
                 8 hrs. 
               
               
                   
               
             
          
           
               
                 Chlorhexidine Diacetate 
                 4 
                 30.1 
                 100 
               
               
                 Chlorhexidine Gluconate 
                 0 
                 22.1 
                 13.3 
               
               
                 Chlorhexidine Dichloride 
                 22.3 
                 17.6 
                 18.1 
               
               
                 Chlorhexidine Acetate 
                 ND 
                 ND 
                 ND 
               
               
                 Alexidine 
                 100 
                 N/G* 
                 N/G 
               
               
                 Trichlocarbonilide 
                 17.7 
                 25.7 
                 89.2 
               
               
                 Triclosan 
                 30.0 
                 0 
                 18.1 
               
               
                 Chitosan 
                 28.6 
                 30.9 
                 0 
               
               
                 Carboxymethyl Chitosan 
                 5.7 
                 29.4 
                 10.8 
               
               
                 Silver Sulfadiazine 
                 10.9 
                 36.8 
                 69.9 
               
               
                 Silver Acetate 
                 18.3 
                 24.3 
                 100 
               
               
                 Silver Citrate Hydrate 
                 13.7 
                 19.1 
                 84.3 
               
               
                 Silver Protein 
                 26.9 
                 14.7 
                 74.7 
               
               
                 Cetrimide 
                 20.6 
                 100 
                 N/G 
               
               
                 Cetyl pyridium Chloride 
                 9.7 
                 100 
                 N/G 
               
               
                 Benzalkonium Chloride 
                 23.4 
                 29.4 
                 100 
               
               
                 Hexamethylene Tetramine 
                 ND* 
                 ND 
                 ND 
               
               
                 Chloroxylenol 
                 36.6 
                 18.4 
                 22.9 
               
               
                 o-phthalaldehyde 
                 19.4 
                 100 
                 N/G 
               
               
                 Bisphenol 
                 19.4 
                 24.3 
                 37.3 
               
               
                 HM-4100 
                 20.6 
                 18.4 
                 28.9 
               
               
                 Hm-4072 
                 21.7 
                 18.4 
                 69.9 
               
               
                 AGS-20 
                 13.1 
                 41.2 
                 89.2 
               
               
                   
               
               
                 *1. NG = no growth (all microbes have been killed already) 
               
               
                 *2. ND = no data 
               
             
          
         
       
     
         [0029]    The following is a representative formulation within the scope of the present invention:
       1. Acrylate copolymer solution, such as Lubrizol&#39;s Avalure AC-315, 20% by weight in isopropanol (Lubrizol Advanced Materials, Inc. Cleveland, Ohio);   2. Rheological modifier, such as Cabot&#39;s TS-720, 10% by weight of solid acrylate copolymer;   3. Antimicrobial agent, such as Alexidine or cetrimide or cetyl pyridium chloride, 7% by weight of solid acrylate copolymer.       
 
         [0033]    The acrylate-type polymer, copolymer, or polymer resins should be soluble in one or more of the aforementioned mild solvents (e.g., common low molecular weight alcohols, such as methanol, ethanol, isopropanol, etc.; low molecule weight alkanes, such as pentane, heptane, hexane, etc.; and/or simple ketones, such as acetone. Preferably, the polymers should not dissolve in water. The polymer or copolymer can be alkyl acrylate, alkyl methacrylate, alkyl hydroxyl(meth)acrylate or alkyl methoxycinnamate acrylate and the like. Examples are Lubrizol&#39;s Avalure AC-315 and National Starch and Chemical Company&#39;s Dermacryl 79 (Bridgewater, N.J.). 
         [0034]    The rheological modifiers can be organic clay, castor wax, polyamide wax, polyurethane, fumed silica, and the like. The quantity of the modifier can be less than 30% by dry weight of the mild solvent coating, preferably less than 20%, and most preferably between about 0.2% and about 10% dry weight of the mild solvent coating. 
         [0035]    The antimicrobial agents can be aldehydes, anilides, biguanides, silver element or its compounds, bis-phenols, and quaternary ammonium compounds for the formulations. The preferred agents may be cetyl pyridium chloride, cetrimide, benzalkonium chloride, alexidine, chlorhexidine diacetate or o-phthalaldehyde. The quantity of the agent in the formulation should be less than 50% of the dry weight of the mild solvent coating, preferably less than 30%, and most preferably between about 0.5% and about 20%. 
         [0036]    The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.