Patent Publication Number: US-2009220378-A1

Title: Indicator device having an active agent encapsulated in an electrospun nanofiber

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 10/965,350, filed Oct. 14, 2004. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to an indicator device for determining the efficacy of an antimicrobial treatment process, and more particularly to an indicator device including an active agent encapsulated in an electrospun nanofiber. 
     BACKGROUND OF THE INVENTION 
     In the healthcare industry it is often necessary to determine the efficacy of an antimicrobial treatment process. As used herein, “antimicrobial treatment process” includes, but is not limited to, hand and machine washing, sterilization, disinfection, decontamination, inactivation, and sanitization processes. The effectiveness of such processes is typically verified by use of a biological indicator, a chemical indicator, or both. An indicator is typically comprised of (1) an active agent, such as a biological specimen (e.g., an enzyme from a biological source, a biological organism, or both) or a color changing chemical sensitive to a specific chemistry, and (2) a carrier substrate (i.e., support system) for supporting the active agent. Effectiveness of an antimicrobial treatment process may be indicated by a change in the color of the active agent. Alternatively, process effectiveness may be evaluated by exposing the active agent or its byproducts to a reagent (e.g., a growth media) that reacts therewith. 
     During an antimicrobial treatment process, the active agent may separate (e.g., wash off) from the carrier substrate due to exposure to the liquid or gaseous treatment chemicals used during the antimicrobial treatment process. Consequently, the indicator may operate improperly. In this regard, the indicator may have a lowered sensitivity, or have a total operation failure. Moreover, the separated active agent may also re-contaminate the item being treated. 
     The present invention provides an indicator device including an active agent embedded in an electrospun nanofiber to prevent the separation of the active agent from the carrier substrate. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided an indicator device for use in determining the efficacy of an antimicrobial treatment process, comprising: (a) at least one active agent; (b) at least one encapsulation component for encapsulating the at least one active agent wherein said encapsulation component includes at least one of the following: a polymer; a polymer blend; and a mixture of a polymer and a plasticizer; and (c) a carrier substrate. 
     An advantage of the present invention is the provision of an indicator device that encapsulates an active agent in an electrospun nanofiber. 
     Another advantage of the present invention is the provision of an indicator device that prevents the separation of the active agent from a carrier substrate. 
     Still another advantage of the present invention is the provision of an indicator device that allows contact between the treatment chemistry of the antimicrobial treatment process and an active agent, without compromising the integrity of the active agent, the carrier substrate, or the articles being treated by the treatment chemistry. 
     Yet another advantage of the present invention is the provision of an indicator device suitable for process validation, indication, detection and the like, in connection with an antimicrobial treatment process. 
     Yet another advantage of the present invention is the provision of an indicator device suitable for neutralizing antimicrobial chemistry after a treatment process. 
     These and other advantages will become apparent from the following description of a preferred embodiment taken together with the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form a part hereof, and wherein: 
         FIG. 1  is a schematic diagram of an apparatus for producing electrospun nanofibers; and 
         FIG. 2  illustrates an apparatus for producing electrospun nanofibers. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     Referring now to the drawings wherein the showings are for the purposes of illustrating a preferred embodiment of the invention only and not for purposes of limiting same,  FIG. 1  shows a schematic diagram of an apparatus  10  for producing electrospun nanofibers. The electrospun nanofibers form a fabric or mat from an extrusion of plastic. The extrudate can incorporate at least one active agent. The fabric or mat formed by the extrudate thus provides a host for the active agent. Apparatus  10  is generally comprised of a high voltage power supply  20 , an electrode  22 , a capillary tube  30 , and a collector electrode  70 . 
     High voltage power supply  20  preferably produces a voltage in the range of 5 kV to 20 kV, and has a low current. Electrode  22  is connected to high voltage power supply  20  and extends into capillary tube  30 . Capillary tube  30  is filled with a polymer solution  40 . In a preferred embodiment, polymer solution  40  includes a polymer and a solvent used to solvate the polymer, as will be described in detail below. Alternatively, a polymer melt can be substituted for the polymer solution. Collector electrode  70  preferably takes the form of a metal plate, screen or grid. Collector electrode  70  is connected to ground. 
     Alternate arrangements of the electrodes can be made to allow for the generation of plasma in air or inert gases, or both, prior to, concurrent, or subsequent to the polymer discharge from capillary tube  30 . Such electrode arrangements are known based upon the type and proximity of the electrodes, and the use of dielectric materials to minimize or eliminate arcing or filamentary discharge currents. Electrode configurations include dielectric barrier discharge such as resistive barrier discharge, hollow/microhollow cathode discharge, capillary plasma electrode and cathode boundary layer, and electromagnetic ion implantation such as microwave generated plasma, atmospheric plasma jet, and nitrogen gas ion implantation. In cases where plasma generation is incorporated into the electrospinning process, the applied voltages can be one to three orders of magnitude higher. 
     A carrier substrate  60  is preferably located proximate to collector electrode  70 . In the illustrated embodiment carrier substrate  60  is located on top of collector electrode  70 . Carrier substrate  60  supports the electrospun nanofibers formed thereon, as will be described in detail below. Carrier substrate  60  is preferably a rigid porous or nonporous material, as will be described in further detail below. In a preferred embodiment, carrier substrate  60  is selected for resistance to heat exposure, liquid chemicals, and gaseous chemicals used in an antimicrobial treatment process. 
     It should be appreciated that carrier substrate  60  may also take the form of electrospun nanofibers in the form of a mat, depending upon the thickness and durability of the electrospun nanofibers. 
     A physical representation of an exemplary electrospinning apparatus  100  is shown in  FIG. 2 . A non-conducting support structure  110  is provided to suspend capillary tube  30  above carrier substrate  60  and collector electrode  70 . Capillary tube  30  is connected with support structure  110  by support members  120 . Collector electrode  70  and/or carrier substrate  60  may be moveable relative to capillary tube  30 . Accordingly, polymer fiber may be placed at desired locations on carrier substrate  60 . It should be appreciated that multiple capillary tubes  30  may be suspended from support structure  110 . 
     The electrospinning process can be summarized as follows. Capillary tube  30  is filled with a polymer solution  40 , and electrode  22  is inserted into polymer solution  40  to charge polymer solution  40  to a high electrical potential. It should be understood that electrode  22  can also charge polymer solution  40  when it is in, connected to, or in contact with the outer wall of a metal capillary tube. Air pressure above polymer solution  40  inside capillary tube  30  may be controlled by an air pump, such that a stable drop of polymer solution  40  is suspended at the tip of capillary tube  30 . It should be appreciated that polymer solution  40  may be of sufficient viscosity to sustain surface tension in capillary tube  30  without the need for an air pump. The drop of polymer solution  40  at the tip of capillary tube  30  is deformed into a conical portion  45 , referred to as a Taylor cone. Electrospinning occurs when the electrical forces at the surface of polymer solution  40  overcome surface tension and cause an electrically charged liquid jet of polymer solution  40  to eject from capillary tube  30 . As the jet of polymer fiber stretches and dries, radial electrical forces cause it to repeatedly splay, thereby forming a splayed portion  52 . The charged polymer fiber can be directed or accelerated by the electrical forces. The polymer fibers are deposited on carrier substrate  60 , as sheets or other geometric forms. The solvent added to the polymer will preferably evaporate as the jet of polymer travels from capillary tube  30  to carrier substrate  60 . The polymer fibers have nanometer scale diameters (i.e., nanofibers), typically in the range of 40 to 2000 nm. Lower voltages result in thinner polymer fibers, since less force is used to pull polymer solution  40  out from capillary tube  30 . 
     It should be appreciated that depending on the size of the active agent and solubility of the solvent, the active agent can be embedded on the outside of the nanofiber or contained within. 
     More details concerning the electrospinning process are found in the article by Darrell H. Reneker and Iksoo Chun entitled “Nanometre Diameter Fibres of Polymer, Produced by Electrospinning,” Nanotechnology 7 (1996), pages 216-233, and the article by Jayesh Doshi and Darrell H. Reneker entitled “Electrospinning Process and Applications of Electrospun Fibers,” Journal of Electrostatics 35 (1995), pages 155-160, both of which are incorporated herein by reference. 
     The indicator device of the present invention finds utility in a wide variety of applications, including, but not limited to, processes involving antimicrobial and antiseptic efficacy, adequate skin barrier detection, post-washing efficacy for handwashing, pre- and post-processing of food product safety, and industrial cleaning efficacy. The aforementioned processes may employ heat, liquid treatment chemicals, and/or gaseous treatment chemicals. Antimicrobial treatment processes may be carried out with use of an automated or a manual apparatus, including, but not limited to, washer/disinfectors, reprocessors and autoclaves. 
     By way of example and not limitation, the indicator of the present invention may be used as a biological indicator, a chemical indicator, a cleaning indicator, and a detection indicator for infection control practices. Biological indicators may be used to qualify food contact surfaces, medical device decontamination, high level disinfection, and sterilization. Chemical indicators may be used to detect use-dilution in medical reprocessing environments or residual chemistries (e.g., glutaraldehyde, peroxide). Cleaning indicators may be used after a cleaning process to detect residual chemicals on a surface, and determine adequate impingement in automated washers and clean room environments. Detection indicators for infection control practices may be used in connection with surgical site preparation, and pre- and post-operative infection control. 
     In accordance with a preferred embodiment of the present invention, the abovementioned electrospinning method and apparatus are used to extrude liquid polymer fibers with at least one active agent encapsulated therein to produce a non-woven nanofiber “fabric” or mat. Preferably, each individual nanofiber has a near-uniform distribution of the active agent. 
     An indicator device, according to a preferred embodiment of the present invention, is generally comprised of an active agent, an encapsulation component, and a carrier substrate. 
     Active agents include, but are not limited to: biological agents, chemical agents, physical agents, and combinations thereof. Biological agents include, but are not limited to, spore forming bacteria (e.g., a  Bacillus  species spore), fungal spores (e.g.  Aspergillus niger ), mycobacteria, and prions (e.g. yeast PrP). Chemical agents include, but are not limited to, inorganic dyes (e.g., iron and manganese oxides, and copper sulfate) and organic dyes with photo-, thermo- and/or electrochemical-chromic properties (e.g., tetrazolium, sulfur, and lead salts), colorimetric (food colors carotenoids, oxonols, azo- and aza-compounds, nitro and nitroso-compounds, carbonyl, and quinone/anthraquinone compounds), fluorescence (e.g. rhodopsin), phosphorescence, and chemiluminescence (e.g. luciferin), biological dyes (crystal violet), redox dyes, and crown ethers to detect metal ions. A complete list and description of dyes and pigments can be found in the book by Henrich Zollinger entitled, “Color Chemistry: Syntheses, Properties and Applications of Organic Dyes and Pigments,” VCH Verlagsgesellschaft mbH: Weinheim, Germany, 1987. 
     It should be appreciated that in an alternative embodiment of the present invention, the chemical agents may function to neutralize (e.g., catalase) an antimicrobial chemistry after a treatment process. In this case, the indicator device is located remote from the treatment environment and accessed by the antimicrobial chemistry for the purpose of neutralizing it after the treatment process. 
     Antimicrobial chemistries include, but are not limited to, chlorine and chlorine compounds (e.g., hypochlorite, triclosan, PCMX, chlorinated biguanides such as chlorhexidine), peroxygens (e.g., hydrogen peroxide, mono- or di-percarboxylic acids, monopersulfate), alcohols (e.g. isopropyl-, ethyl-), phenolic compounds, iodine compounds (e.g., PVP-I), cationic surfactants (Quaternary Ammonium Compounds), anionic and nonionic surfactants, and food and industrial grade preservatives (e.g., benzoic acid derivatives, sorbic acids, and natural and essential oils with pesticidal efficacy), and any combination thereof. Antimicrobial chemistries may also include antimicrobials with increased activity when in the form of a nanoemulsion (e.g., Nanostat from NanoBio Corp, and Ecotrue from Envirosystems). Such nanoemulsions are made by imparting oil/water emulsions of oils, surfactants, and chloro-xylenols (PCMX). A complete list of antimicrobial compounds can be found in the book by Seymour Block entitled, “Disinfection, Sterilization, and Preservation,” 3 rd  through 5 th  edition, herein fully incorporated by reference. 
     Physical agents include, but are not limited to, polymers, non-polymers, supports systems, and markers that provide detection of treatment process parameters, microelectrode materials or electrochemical sensor materials, or both, nanocarbon tube, and RFID tags. 
     Physical agents provide a means to insure adequate indication of various degrees of effectiveness of an antimicrobial treatment process and/or various degrees of effectiveness of a phase of an antimicrobial treatment process having multiple phases. 
     In accordance with an alternative embodiment of the present invention, physical agents within the nanofibers can be used to neutralize an antimicrobial treatment chemistry after the process, especially physical agents that generate a plasma gas field or electric field, or agents that stabilize free radicals (e.g. hydroxyl groups, hydrogen peroxide, ozone). In this case, the indicator device is located remote from the treatment environment and accessed by the antimicrobial chemistry for the purpose of neutralizing it after the treatment process. 
     It should be appreciated that polymer deposition can be arranged to accommodate, protect, or encapsulating miniature metals and other solid state materials that function as a trip, signal relay or signal transponder system to measure, indicate, or record critical parameters when interrogated or in real time. Also, polymer fibers containing MEMS (Micro-Electro-Mechanical Systems) components can be made as microarrays used to screen a sample for microorganisms. 
     As indicated above, different types of active agents may be used in combination. For example, an indicator device may include both a physical agent and a chemical agent. The physical agent breaks down during an antimicrobial treatment process to expose a chemical agent to the process environment. In this regard, the physical agent has pressure, heat, or time-sustaining properties that prevent the chemical agent from being exposed to treatment chemicals until a predetermined period of time has elapsed, or until a predetermined stage of the antimicrobial treatment process has commenced. 
     The encapsulation component encapsulates at least one active agent to reduce “wash-off,” and may control the reaction between the active agent and treatment chemicals. Preferably, the encapsulation component is comprised of a material that is biologically and chemically inert, has a controlled adhesion strength to the carrier substrate, and is permeable to the treatment chemicals of the antimicrobial treatment process. In accordance with a preferred embodiment of the present invention, the encapsulation component is selected from the group including, but not limited to, a polymer; a polymer blend; and a mixture of a polymer and a plasticizer. The polymer may include any solid or liquid high-molecular weight polymer obtained by conducting a polymerization reaction, or produced by “drying components” capable of creating a polymer, pseudopolymer, and the like. Drying components may include solvents that remove water (e.g. acetone), agents that absorb/adsorb a solvent (e.g., polyacrylates, chitosan), polymerizers/placticizers (e.g., oxidizers), or heat or electrical energy produced through the apparatus electrodes (e.g., plasma gas) or by activation of the physical agents (e.g., electroactive polymers, superconducting metals, and MEMS) in the electrospun polymer. 
     By way of example, and not limitation, the polymer or polymer blend may include one or more of the following: polycaprolactone (a biodegradable polymer); pluronic acid; Tecophilic® family of highly water absorbing, aliphatic, polyether-based thermoplastic polyurethanes, from Thermedics Polymer Products, that have been specially formulated to absorb equilibrium water contents of up to 150% of the weight of dry resin; Tecoflex® family of highly water phobic, aliphatic, polyether-based thermoplastic polyurethanes from Thermedics Polymer Products; polymeric gels that are insoluble in water, including, but not limited to, co-polymers of polyvinylpyrolidone, polyacrylamide, polyvinyl alcohol, cross-linked polyacrylates, polyethyleneimine, and the like; polymer resins, including, but not limited to, Carbopol® from B.F. Goodrich; cellulose-based polymers, including, but not limited to, ethylcellulose; biologically derived polymers, including, but not limited to collagen, polyhydroxy-aldehydes and ketones (e.g. glucose, galactose); peptides (serum albumin); and shellac, Polymers with active binding sites for halogens (e.g. chlorine) such as polystyrene hydantoin (Halopure®) from Vanson-Halosource, quaternary amines (Microban Shield®) from Aegis, and acrylates and olefins are also suitable. 
     The encapsulation component may also include a solvent for liquefying the polymer or polymer blend. By way of example, and not limitation, the solvent may be selected from the following: water (H 2 O), tetrahydrafuran (THF), ethanol (EtOH), acetone, isopropanol, and combinations thereof. Ionic liquids such as N-methylimidazole from BASF Corporation may be used as alternatives to the aforementioned organic solvents. The ionic liquids themselves may be capable of polymerizing and forming a polymer mat, and as such eliminate the need for the aforementioned solvents. 
     It should be understood that the selected solvent should not inactivate the active agent encapsulated within the polymer. For instance, suitable combinations of polymers and solvents for encapsulation of spores, include, but are not limited to: (1) polycaprolactone and acetone; (2) pluronic acid and ethanol; and (3) Tecoflex® and tetrahydrafuran (THF), (4) albumin and water, and (5) N-halamine polymers and dimethylsulfoxide, as described in detail in U.S. Pat. No. 6,294,185, issued to Worley et al., Sep. 25, 2001, entitled “Monomeric and Polymeric Cyclic Amine and N-Halamine Compounds.” 
     The active agent may be directly incorporated into an encapsulation component, or the active agent may be deposited onto a carrier substrate and be sealed thereon by an encapsulation component. For instance, high level disinfection and decontamination of surfaces may be validated/indicated by means of an active agent, such as a heat sensitive marker or a dry-resistant organism (non-pathogenic). 
     As indicated above, the carrier substrate is preferably a rigid porous or nonporous material. By way of example, and not limitation, the carrier substrate may be formed of a plastic sheet or film, a teflon coating, woven or non-woven fibers (e.g., cotton, cloth, and plant derived cellulose), paper, aluminum foil, and stainless steel. Furthermore, the carrier substrate may be formed from the polymer solution as an end result of electrospinning the liquefied polymer. Also, the deposition of the charged polymer onto the carrier substrate at the ground plate or mesh during the electrospinning process can be coupled with thermal or nonthermal plasma grafting processes to enhance the uniformity and binding strength of the polymer onto the carrier substrate. 
     A biological indicator according to the present invention may include spores that are encapsulated into an electrospun nanofiber, as described above. For example, a genetically modified  Bacillus  species (e.g.,  stearothermophilis  in heat-based systems) with a chromosomally-integrated indicator, foreign gene (e.g., the gene for firefly luciferase) may be encapsulated into the nanofiber. The foreign gene is integrated into chromosomal operons that are not expressed during the sporulation cascade, but are expressed early in a germination cascade. The foreign gene product is not present in the spore, but on germination would be expressed, and thus detected by a variety of available rapid-detection systems. 
     As noted above, cleaning indicators can be used to detect residuals on a surface following a cleaning process. An active agent is encapsulated within an encapsulation component, and sustained indefinitely until such time that the active agent is affected by the cleaning process. In accordance with a preferred embodiment, the active agent is a chemical resistant to biological, chemical, and physical degradation; soluble in the encapsulation component (e.g., a polymer compound); and provides a colorimetric change when exposed to the treatment chemicals of the cleaning process. By way of example, and not limitation, the active agent for a cleaning indicator may be selected from the group including, but not limited to, a water-soluble dye (e.g., a pH indicator dye such as phenol red, methylene blue and Azo compounds), and a fluorescent marker. 
     The present invention also finds advantageous application as an antimicrobial fabric for simulating a surgical barrier site, as will be described by example below, and as an antimicrobial delivery agent. 
     With regard to an antimicrobial delivery agent, an antimicrobial agent may be encapsulated as an active agent into the encapsulation component for application to surfaces, to permit slow release over time. For example, biocides (including, but not limited to, chlorhexidine and triclosan in formulation) may be encapsulated and directly applied to a skin surface. This allows for a “slow-release” of the antimicrobial agent for bioburden reduction/control, such as bioburden reduction for preoperative preparation or bioburden control at wound sites or points of surgical entry (e.g., catheter entry sites). 
     In accordance with an alternative embodiment of the present invention, the indicator device may have multiple layers of encapsulation components. For instance, a first layer encapsulation component covers a second layer encapsulation component, where the second layer encapsulation component encapsulates an active agent. The multiple layers of encapsulation components may be selected to provide an indicator device that indicates the efficacy/adequacy of an enzymatic, pH or other cleaning chemistry process. For example, a first layer encapsulation component may be comprised of a first polymer, while the second layer encapsulation component may be comprised of an insoluble polymer that encapsulates a dye mix. The first layer encapsulation component is removed during a cleaning process, thereby exposing the second layer encapsulation component. The active agent encapsulated in the second layer encapsulation component changes color to provide an indication of the efficacy of the cleaning process. 
     It should be appreciated that the encapsulation component (e.g., polymer) itself may be used to determine the effectiveness of an antimicrobial treatment process. In this regard, when multiple layers of encapsulation components are applied to a carrier substrate, each layer may have different adhesion strengths to the carrier substrate or subsequent layers of encapsulation components, or the concentrations of the polymer or polymer blend are adjusted in series to provide a scale for process effectiveness. For example, a polymer solution including hydrophilic and hydrophobic polymers can be adjusted such that the hydrophobic polymer concentration is greater than the hydrophilic polymer concentration to minimize wash-off in high flow liquid processes. The balance of the solution contains a hydrophilic polymer in a concentration suitable to permit penetration of the treatment active. A preferred concentration is 70% hydrophobic polymer (e.g., tecoflex) and 30% hydrophilic polymer (e.g., pluronic acid). 
     The present invention will now be further described by way of the following examples: 
     Example 1 
     Biological Indicator 
       
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 Encapsulation 
                 Polyurethane 67% Tecoflex and a water soluble 
               
               
                 Component 
                 polymer (33% Pluronic acid) 
               
               
                   
                 Solvent: Tetrahydrofuran (THF) 
               
               
                 Active Agent 
                 Spore  Bacillus stearothermophilus  ATCC 12980 
               
               
                 Carrier Substrate 
                 Polymer Mat 
               
               
                   
               
            
           
         
       
     
     In Example 1, a nanofiber biological indicator (BI) was produced using the electrospinning process described above to compare the level of wash-off against commercially available paper impregnated BI&#39;s. These BI&#39;s typically lose approximately 50% of the indicator organism solely due to mechanical action of water in automated liquid systems. In this regard, spores were incorporated into a polymer blend of polyurethane and a water soluble polymer. The nanofiber BI was sectioned and cut into two 3 cm 2  samples containing approximately 2.35×10 7  (7.37 log 10 ) colony forming units (CFU)  Bacillus stearothermophilus  ATCC 12980 per sample. To simulate the process conditions that can cause wash-off in liquid-based automated reprocessing systems, the impact of agitation to remove the indicator organism was evaluated in vitro by vigorously vortexing the samples in 10 milliliters (mL) deionized water (DI) 5 times; each time vortexing for 3 seconds. Several observations were made as to the effectiveness of the polymer to retain the test organisms and to show reproducibility in results. Overall, the total wash-off after all 5 washings were 2.5 and 2.9×10 3  CFU (0.01%) for each sample. The wash-off between each washing was very low, ranging from 1.6 to 9.3×10 2  CFU. Furthermore, the wash-off from each subsequent wash compared to the initial wash was exhaustive as less wash-off occurred after each subsequent washing. The initial wash-off values for the samples between 7.5 and 9.3×10 2  CFU, and were reduced to 1.2 to 1.6×10 2  CFU after the fifth wash. As a result, the polymer BI outperformed commercial BI&#39;s by retaining 99.99% of the test organism as compared to approximately 50%. In a separate test, the ability of an active agent to penetrate the nanofiber BI and inactivate the test organism was investigated. Samples as prepared above were treated in vitro with a 0.2% peracetic acid/builders solution (i.e., STERIS 20 Sterilant Concentrate) at 50° C. over 10, 40, 80, and 120 seconds, removed, and neutralized in 0.048% sodium thiosulfate. The samples were then dissolved in a low concentration of non inhibitory THF solvent to dissolve the polymer and quantify the remaining test organism. Serial dilutions were performed in Tryptic soy broth and aliquots of the appropriate dilutions dispensed onto pour plates of Tryptic Soy Agar. Based on the results, the active agent was permitted to penetrate the polymer to contact and kill the test organism as shown by an initial reduction at 10 seconds of 0.78 log 10  and a significant reduction at 120 seconds of 5.8 log 10 . Based on the kill rate shown above, it can be assumed that at longer exposure times beyond 120 seconds, all of the test organism in the BI would have been inactivated. 
     A nanofiber BI has several advantageous characteristics over conventional biological indicators. In this respect, the nanofiber BI is durable; the nanofiber BI can be penetrated by a liquid antimicrobial treatment chemical; the nanofiber BI does not affect the qualitative medium used to detect the presence of a test organism; the nanofiber BI has a wall strength that allows a spore to outgrow; wash-off of spores is minimized by formation of nanofiber around the spores; accuracy of wash-off qualification is improved by uniform distribution of spores throughout the nanofiber BI; the electrospinning process provides a sterile environment without the need for a clean room; a nanofiber BI is ready for use after being manufactured without a drying period; a nanofiber BI may not require special packaging and does not add restrictions to the shelf life of the BI because the spores are encapsulated within the nanofiber. 
     Example 2 
     Chemical Indicator 
       
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 Encapsulation 
                 Polyurethane Tecoflex 
               
               
                 Component 
                 Solvent: Tetrahydrofuran (THF) 
               
               
                 Active Agent 
                 Color changing chemical: 0.16% crystal violet 
               
               
                 Carrier Substrate 
                 Polymer Mat 
               
               
                   
               
            
           
         
       
     
     The chemical indicator (CI) includes a color changing chemical (i.e., crystal violet) that is sensitive to oxidizing chemistry, such that upon oxidation with an antimicrobial treatment chemical (i.e., STEMS 20 sterilant), comprised of 0.2% peracetic acid (PAA) in a builder package containing buffers, anticorrosives, and chelating agents will cause a color change. The baseline color of the CI is deep purple, and changes to a white color in the presence of &gt;1500 mg/L of the sterilant STERIS 20. 
     It should be appreciated that other dyes/pigments can be encapsulated in the encapsulation component to verify other parameters of the antimicrobial treatment process, including, but not limited to, time and temperature. 
     Example 3 
     Cleaning Indicator 
       
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 Encapsulation 
                 Polyurethane 67% Tecoflex and a water soluble 
               
               
                 Component 
                 polymer (33% pluronic acid) 
               
               
                   
                 Solvent: Tetrahydrofuran (THF) 
               
               
                 Active Agent 
                 Color changing chemical: 7% blue ink 
               
               
                 Carrier Substrate 
                 Stainless steel coupon 
               
               
                   
               
            
           
         
       
     
     The cleaning indicator (CnI) of Example 3 is used to test the efficacy of a cleaning agent of an automated cleaning system that penetrates and removes soil, debris and contaminants using a high pressure spray. In Example 3, the CnI converted from a baseline yellow color to a deep blue color upon contact with water for 30 seconds. 
     Example 4 
     Antimicrobial Surgical Site Barrier 
       
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 Encapsulation 
                 Polyurethane (67% Tecoflex) and a water soluble 
               
               
                 Component 
                 polymer (33% Pluronic acid) 
               
               
                 Active Agent 
                 Chlorhexidine Gluconate (CHG) in ethanol 
               
               
                   
                 Concentration Range: 0.5% to 1% 
               
               
                 Carrier Substrate 
                 [Please identify carrier substrate.] 
               
               
                   
               
            
           
         
       
     
     The effectiveness of the CHG polymer mat was investigated using a disk diffusion method on  Staphylococcus aureus  ATCC 6538 and  Escherichia coli  ATCC 25922 lawn plates. The plates were prepared for each organism by dispensing and spreading 0.1 mL of the bacterium over the entire surface of prepared tryptic soy agar plates to create a “lawn.” Concentrations of chlorhexidine gluconate (CHG) at 0.25%, 0.5%, and 1.0% were electrospun with Tecoflex to produce an antimicrobial polymer mat. The polymer mats were cut into two 0.5-1.0 inch diameter disks for each CHG concentration. One disk per plate was placed into the center of the bacterial plate The plates were then incubated at 37° C. for 7 days to determine the zone of inhibition or antimicrobial coverage around the disk (measured in millimeters diameter), which simulates the persistence of an antimicrobial dressing to inactivate resident microorganisms on the skin. For  S. aureus,  0.25%, 0.50%, and 1.0% CHG was effective showing mean zones of 20 mm, 25 mm, and 25 mm zones, respectively at 7 days, while at the same concentrations  E. coli  mean zones were 11 mm, 23 mm, and 28 mm. By these results it is apparent that the CHG polymer is capable of inactivating resident microorganisms and shows minimal leaching and sustained release of the CHG by maintaining the zones over 7 days. 
     The nanofiber of Example 4 provides a barrier that maintains an air exchange to the environment without allowing external organisms to invade. Furthermore, the delivery of the active agent is localized and sustained over an extended period of time. Accordingly, a greater amount of the active agent is in contact with the microorganisms, and prevents their proliferation. The nanofiber can remain in contact with the skin during an operation, or at a device (e.g., catheter) insert site to provide controlled release of the active agent around an incision or orifice. In a preferred embodiment, the nanofiber is biodegradable. 
     It has been recognized that surgical site infections are a leading cause of postsurgical infections. Antimicrobial chemicals (e.g., chlorhexidine (CHG) or polyvinylpyrrilodone iodine (PVP-I)) are used to reduce the risks of infection. However, it has been observed that little of the antimicrobial chemical is effective against microbes, because penetration is superficial and may not reach areas where microorganisms (e.g., bacteria) reside on the skin. 
     Other modifications and alterations will occur to others upon their reading and understanding of the specification. For example, the nanofibers of the present invention may be arranged into a bar code configuration, or other machine readable code format. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.