Patent Application
20170275472
The present subject matter relates to materials possessing a combination of release-killing, contact-killing and anti-adhesion antimicrobial properties and details of their preparation, as well as physicochemical properties and methods of use for long-term disinfections of solid and porous surfaces.
According to a World Health Organization report (www.who.int/mediacentre/factsheets/fs310/en/), airborne and waterborne pathogens, such as tuberculosis, lower respiratory infections and pulmonary infections are among the top ten causes of deaths accounting for millions of death each year. Currently, filtration technology remains the most effective and economical means for air and water purification and disinfection. However a known problem with conventional filtration technology is the fact microbes trapped in filters remain viable to the extent they can grow in and colonize the filter. For example, in an air filter the warm and humid environment encourages microbial growth and presents a two-fold problem. Not only is filter performance degraded, but the colonization also poses a clear risk of contamination of the air to be filtered by the very pathogenic bacteria, viruses and fungi that the filter is designed to eliminate. A further known problem of conventional filtration technology is the ability of ultra-small cells and viruses to penetrate the filter.
Certain solutions attempt to address the problem of microbial colonization, contamination and fouling in air and water filters. Some examples in this regard are addition of a photocatalyst, as shown in U.S. Pat. Nos. 6,607,702 and 6,878,277 and U.S. Published Application Nos. 2009/0209897 and 2011/0159109; addition of metal, such as silver nanoparticles, or a metal oxide, such as zinc oxide nanoparticles, as shown in U.S. Pat. Nos. 5,618,762, 5,681,468 and 7,744,681 and U.S. Published Application Nos. 2005/0279211, 2007/0045176 and 2008/0302713); addition of other biocides in the filtration media, such as biostat, organic quaternary ammonium salt, phenol derivatives and isothiazolin-based compounds, as respectively shown in U.S. Pat. Nos. 5,288,298, 6,780,332, 5,762,797, 5,868,933, 6,171,496, and 7,942,957, and combining irradiation technologies with the filtration process, such as UV, magnetic or electric fields, plasma and polarization, as shown in U.S. Pat. Nos. 6,939,397 and 6,776,824.
These solutions present various drawbacks. For example, photocatalytic disinfection requires an additional light source, is slow, sensitive to humidity and vulnerable to surface contamination. The use of silver nanoparticles increases the material and manufacturing costs. Furthermore, widespread use and misuse of antimicrobial silver is responsible for the emergence of silver-tolerant and resistant bacteria. Though irradiation treatments are relatively safe and disinfect rapidly, the additional electrical devices and electricity result in higher device and disinfection costs. For these reasons, the manufacturability, safety and long-term stability of filters using ancillary technologies and those including natural and synthetic biocides remain a concern.
The present subject matter overcomes the shortcomings described. Filters prepared utilizing the instant specific colloidal encapsulation of biocide mixtures containing at least one volatile or semi-volatile biocide in an inorganic-organic shell capable of varying and controlling the release of the enclosed biocides provide measurable, unexpected benefits. The inorganic-organic shell comprises one or more polymers and one or more metal compounds, such as metal oxides, metal salts, metal complexes and/or metallic particles, possessing delayed killing, contact-killing and anti-adhesion properties. The antimicrobial coating solution can be coated on both porous and nonporous surfaces to create an antimicrobial surface exhibiting a combination of release-killing, contact-killing and anti-adhesion properties against microorganisms.
The present subject matter, in one embodiment is directed to an antimicrobial material for surface coating comprising: (a) biocides comprising at least one antimicrobial component selected from the group consisting of chlorine dioxide, hydrogen peroxide, peroxy acids, alcoholic compounds, phenolic compounds, essential oils, antimicrobial components of essential oils, bleach, antibiotics, antimicrobial phytochemicals, and combinations thereof; and inorganic-organic shells permeable to the biocides, comprising inorganic materials selected from the group consisting of metal oxides, metal complexes, metal salts, metal particles and combinations thereof; and organic materials comprising a nonionic polymer; wherein the inorganic materials are present in a concentration of 0.5-95 wt % of the inorganic-organic shells; and wherein the inorganic-organic shells enclose and contain the biocides permitting storage and release.
The present subject matter, in a further embodiment is directed to a method of producing an antimicrobial coating for application to porous materials or porous media, the method comprising: (a) preparing a biocide mixture; (b) preparing a suspension/solution of nonionic polymers and inorganic materials, the inorganic material being selected from the group consisting of metal oxides, metal complexes, metal salts, metal particles and combinations thereof; (c) preparing a stable emulsion comprising the biocide mixture encapsulated within inorganic-organic shells, the inorganic-organic shells comprising the suspension/solution of the nonionic polymer and the inorganic material; and (d) applying the antimicrobial coating on a porous material or in a porous medium.
The present subject matter, in another embodiment, is directed to a porous antimicrobial object, comprising a porous material or a porous medium with an antimicrobial coating produced by (a) preparing a biocide mixture; (b) preparing a suspension/solution of nonionic polymers and inorganic materials, the inorganic material being selected from the group consisting of metal oxides, metal complexes, metal salts, metal particles and combinations thereof; (c) preparing a stable emulsion comprising the biocide mixture encapsulated within inorganic-organic shells, the inorganic-organic shells comprising the suspension/solution of the nonionic polymer and the inorganic material; and (d) applying the antimicrobial coating on a porous material or in a porous medium.
The present subject matter includes any one or more of the embodiments, or elements thereof, described herein, or permutation or combination of some or all of the embodiments, or the elements thereof, described herein.
The instant subject matter relates to biocidal materials having a combination of contact and time-release biocide properties. The materials are capable of providing for both antimicrobial and anti-adhesion properties. The materials are specifically designed for incorporation into filtration systems, for example, air and water filters. Specifically, the subject matter relates to an antimicrobial coating for porous materials or porous media, comprising a colloidal encapsulation structure withgaseous, volatile, semi-volatile and/or non-volatile biocides enclosed with inorganic-organic shells permeable to the biocides. As discussed herein, the coatings of the present subject matter comprise various components, meaning the coatings include at least the recited components. However, it is also contemplated the coatings consist of the various recited components, meaning the coating is limited to the recited components.
The biocides may be, but are not limited to, chlorine dioxide, hydrogen peroxide, peroxy acids, alcoholic and phenolic compounds, essential oils and their effective components, and combinations thereof, as well as any commercially available biocides, such as bleach, antibiotics, antimicrobial phytochemicals, and combinations thereof. Examples of essential oils are, but are not limited to, thyme oil, tea tree oil, rosemary oil, eucalyptus oil, citral oil, their effective, antimicrobial components and other essential oils with antimicrobial activity. The essential oils may be diluted with solvents. Suitable solvents are, but are not limited to, ethylene glycol, propylene glycol, glycerol, dipropylene glycol, polyethylene glycol, and combinations thereof.
The inorganic-organic shell comprises organic materials and inorganic materials that accounts at least 0.5 wt % of the shell materials. Examples of the organic materials are, but are not limited to, nonionic polymers, such as polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyetherimide, polyethyleneimine and combinations thereof. Specific nonionic polymers are, but are not limited to, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol), other amphiphilic block copolymers, and combinations thereof. The inorganic materials are present in a concentration of 0.5-95 wt % of the inorganic-organic shells. The inorganic materials are, but are not limited to, metal oxides, metal complexes, metal salts, metal particles and combinations thereof. The addition of inorganic materials into inorganic-organic shells improves the durability and performance of the antimicrobial coatings particularly above room temperature. The metal oxides are, but are not limited to, alumina sol, copper oxide sol, silica sol, silver oxide sol, titaniasol, zinc sol, zirconia sol and combinations thereof. The metal oxide sol may be derived from a water-soluble metal salt, a metal alkoxide or commercially available colloidal metal oxides The metal complex are, but are not limited to complexes of metals such as silver, copper, zinc and combinations thereof. The metal complex may be derived from a water-soluble metal salts and metal hydroxides. The metal salts are nitrates, sulfates and halides of silver, copper, zinc and combinations thereof. The metal particles include silver, copper, zinc and combinations thereof.
Regarding the use of amphiphilic block copolymers in the inorganic-organic shell, it is important to note these are nonionic and are used in conjunction with inorganic materials as shown in
It is important to note the inorganic materials, according to the instant subject matter, for example metal, metal oxides, metal complexes, metal salts and metal nanoparticles, and combination thereof, are employed as part of the inorganic-organic shells and are not used as biocides. This is shown in the Examples, where the metals function as part of the inorganic-organic shell and not as a biocide. The inorganic component also influences the size and rigidity of the pores in the encapsulating shell and thus affects the release rate of the contained biocides.
It is important to note that when the inorganic material is a silica sol, the precursor is a sodium silicate solution. Furthermore, insofar as the instant inorganic-organic shell possesses a three-dimensional nature, use of silica or silica sol according to the instant subject matter does not result in the forming of a three dimensional silica network.
Production of the instant subject matter does not require sequential steps. Generally speaking, the antimicrobial material is prepared by storing the biocide mixture in the core of a shell made from a combination of an inorganic component of metal oxides, metal complexes, metal salts or metal particles, or combinations thereof with an organic component mainly comprising nonionic polymers. Specifically, this is done by mixing the biocide mixture with the prepared inorganic-organic mixture under required pH, concentration and temperature to induce the encapsulation of the biocide within an inorganic-organic shell. For example, chlorine dioxide dissolved in water solution containing hydrogen peroxide can be encapsulated within an inorganic-organic shell comprising of silica and polymer at room temperature and neutral pH. A mixture of phenolic compounds in essential oil is encapsulated within an inorganic-organic shell comprising of a metal compound and polymer at room temperature. Further encapsulation can be performed to create capsule-in-capsule structure to better control the release dosing of the biocides.
The present antimicrobial materials can be coated on surfaces by wiping, brushing, casting, dip-coating, spin-coating or spraying. The resulting antimicrobial coating exhibits the advantages of the different components displaying a multi-level, wide-spectrum and durable antimicrobial performance at broad range of temperatures. Further, the instant coatings are employed in methods for preparing a porous antimicrobial object, as well as providing additional multi-level antimicrobial activity to a porous object without changing its pore-related properties and functions. In other words, the porous material will function as originally intended with the added benefit and result of the coating as described herein.
The biocide mixtures were prepared from one or more gaseous, volatile, semi-volatile and/or non-volatile biocides. The biocides include disinfectants, germicides and antimicrobial volatile or semi-volative phytochemicals (VSPs). The typical embodiments include chlorine dioxide, hydrogen peroxide, peroxy acids, alcoholic, bleach and phenolic compounds, VSPs and combinations thereof, as well as any commercially available biocides. The antimicrobial volatile or semi-volatile phytochemicals include essential oils or their active components such as agarwood oil, cajuput oil, cananga oil, cinnamon bark oil, citronella oil, clove oil, eucalyptus oil, fennel oil, ginger oil, kaffir lime oil, nutmeg oil, olliumxanthorrhiza oil, origanum oil, patchouli oil, rosemary oil, sandalwood oil, tea tree oil, thyme oil and vetiver oil.
Metal oxide sols such as alumina sol, copper sol, silica sol, silver oxide sol, titania sol, zinc sol and zirconia sol were prepared by hydrolyzing or peptizing water-soluble salt, metal alkoxide or commercial colloidal metal oxide in acidic or basic media. A typical embodiment is silica sol because it has good chemical stability and biocompatibility. For the preparation of silica sol from water-soluble salt, diluted inorganic acid was added dropwise into water-soluble silicate solution under vigorous stirring to obtain a silica sol with the appropriate pH value. A typical silica concentration is in the range of 0-0.6 mol/1. For the preparation of silica sol from silicon alkoxide, diluted inorganic acid was added into tetraethyl orthosilicate. The prepared emulsion was stirred above room temperature to obtain clear silica sol with weak acidity. For the preparation of silica sol from commercial colloidal silica, diluted inorganic acid was added drop by drop into commercial colloidal silica such as Ludox products under vigorous stirring. The ranges of sol concentration and pH value depend on initial colloidal silica.
Metal complex such as copper, silver, titanium and zinc complex were prepared by reacting metal salts or metal hydroxides with ligands in water or solvents. Metal salt solutions such as silver nitrate, copper chloride, and zinc chloride can be added to form the inorganic-organic shells.
The antimicrobial material is prepared by encapsulating biocides within an inorganic-organic shell. This is done by mixing the biocide(s) with the pre-reacted inorganic-organic mixture of polymer and metal oxides, metal complexes, metal salts or metal particles at room temperature to create a stable emulsion stabilized by the inorganic-organic shells. The typical concentration range of the metal oxide or metal complex in the inorganic-organic shell and finalantimicrobial material is 0.5-95 wt % and 0-5 wt %, respectively.
Various porous materials and porous media were used as substrates for coating with the instant antimicrobial material. Porous materials include, but are not limited to, personal protective equipment, i.e. lab coats, facial masks, shoe covers and hair caps, household products, i.e. tissues, linens, napkins, curtains and tablecloths, clothes and infant products, i.e. diapers, wipes and toys. Porous media may include membranes and filters made up of different materials such as polymers, ceramics and metals. Typical embodiments are commercial polyethylene membrane and HEPA filters.
An antimicrobial coating according to the instant subject matter was prepared by applying antimicrobial material on porous materials and porous media.
Optical microscopy images of biocide capsule emulsions were collected on Olympus BH2-MJLT microscope. SEM images of biocide capsule emulsions, initial porous filters and porous filters with antimicrobial coating were made using JEOL JSM-6390 and JSM-6300F scanning electron microscopes equipped with energy dispersive X-ray detectors.
The judicious selection of biocides, inorganic and organic components, along with the appropriate coating procedure, the use of antimicrobial material doesn't change function-related physical properties of porous media or porous materials, such as filtration performance, color and macroscopic morphology.
Multi-level antimicrobial activities of antimicrobial coatings are believed to contribute to better filtration efficiencies for bacterium and virus (i.e., bacteriophage) aerosols and inhibit the growth of bacteria on HEPA filters. Table 1 and
Enterococcus
Pseudomonas
faccium
Pseudomonas putida
Legionella pneumophilia
Chryseobacterium indologenes
Serratiamarcescens
Klebsilla pneumonia
Enterobacteraerogenus
Stenotrophomonas maltophilia
Bactericidal activities against 106 CFU/ml Gram negative and Gram positive bacteria with contact time of 10 min of HEPA filters coated with polymer-encapsulated ClO2 capsules enclosed within outermost metal oxide-polymer shells.
It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated to explain the nature of the subject matter, may be made by those skilled in the art within the principle and scope of the instant subject matter as further expressed in the claims.
Sodium chlorite powder was dissolved in 50 ml of distilled deionized water to prepare sodium chlorite solution with concentration of 0.1 wt % to 40 wt %. The sodium chlorite solution was then mixed with 0.1 g to 2 g of 30 wt % hydrogen peroxide.
Sodium chlorite powder was dissolved in 50 ml of distilled deionized water to prepare sodium chlorite solution with concentration of 0.1 wt % to 40 wt %. The sodium chlorite solution was then mixed with 0.01 ml to 10 ml of 3% to 8% sodium hypochlorite or potassium hypochlorite solution.
Sodium chlorite powder was dissolved in 50 ml of distilled deionized water to prepare sodium chlorite solution with concentration of 0.1 wt % to 40 wt %. The sodium chlorite solution was then mixed with solutions containing metal ions (Cu2+, Zn2+, Ag+). The final concentration of metal ions ranges from 30 ppm to 3000 ppm.
Sodium chlorite powder was dissolved in 50 ml of distilled deionized water to prepare sodium chlorite solution with concentration of 0.1 wt % to 40 wt %. The sodium chlorite solution was then mixed with metal a micro- and/or nano-particle suspension (copper, zinc, silver). The final concentration of metal particles dispersed into solution ranges from 30 ppm to 30000 ppm.
Sodium chlorite powder was dissolved in 50 ml of distilled deionized water to prepare sodium chlorite solution with concentration of 0.1 wt % to 40 wt %. The sodium chlorite solution was then mixed with peracetic acid. The final concentration of peracetic acid ranges from 0.01 ppm to 10 ppm.
VSP mixtures were prepared of one or more phytochemicals including essential oils, e.g. mixture of thyme oil and tea tree oil, mixture of thymol (active component of thyme oil) and terpinen-4-oil (active component of tea tree oil).
One or more of the components from Example 6 were mixed with 50% to 100% alcohols to form VSP-alcohol mixture. The final concentration of VSP in the mixture varies from 0.1% to 50%.
One or more of the components from Example 6 were mixed with aromatic compounds such as 1% to 10% chloroxylenol solution. The final concentration of VSP in the mixture varies from 0.1% to 50%.
One or more of the components from Example 6 were mixed with solutions containing metal ions (Cu2+, Zn2+, Ag+). The final concentration of metal ions ranges from 30 ppm to 3000 ppm.
One or more of the components from Example 6 were mixed with metal micro- and/or nano-particle suspension such as copper, zinc, silver. The final concentration of metal particles dispersed into solution ranges from 30 ppm to 30000 ppm.
Biocide mixture from Examples 1-5 was encapsulated within a polymer shell (polyethylene glycol (PEG) with the molecular weight of 400 to 40000, polyvinyl alcohol (PVA) with the molecular weight of 31000 to 186000, polyvinyl pyrrolidone (PVP) with the molecular weight of 10000 to 360000, polyethylenimine (PEI) with the molecular weight of 1200 to 60000, PEO-PPO-PEO with the molecular weight of 1000 to 8000, and a combination of two or more thereof). The polymer shell was formed by adding the biocide mixture dropwise into the polymer solution under vigorous stirring. The emulsion can also be ultrasonically-treated for 1 minute.
Biocide mixture from Examples 6-10 was encapsulated within a polymer shell (PEG with the molecular weight of 400 to 40000, PVA with the molecular weight of 31000 to 186000, PVP with the molecular weight of 10000 to 360000, PEI with the molecular weight of 1200 to 60000, PEO-PPO-PEO with the molecular weight of 1000 to 8000). The polymer shell was formed by adding the biocide mixture dropwise into the polymer solution under vigorous stirring. The emulsion was then ultrasonic-treated for 1 minute.
Sodium silicate solution (2.88 g) was diluted with double deionized (DDI) water to obtain 40 ml of sodium silicate solution with 0.25 mol/l NaOH and 0.32 mol/l SiO2. Diluted nitric acid (1 mol/l, 8.20 ml) was added dropwise into the diluted sodium silicate solution under vigorous stirring to obtain acidic silica sol with pH value of 4.
Sodium silicate solution (2.88 g) was diluted with DDI water to obtain 40 ml sodium silicate solution with 0.25 mol/l NaOH and 0.32 mol/l SiO2. Diluted nitric acid (1 mol/l, 15.56 ml) was added dropwise into the diluted sodium silicate solution under vigorous stirring to obtain acidic silica sol with pH value of 1.
Sodium silicate solution (2.00 g) was mixed with DDI water (52 g), followed by adding diluted hydrochloric acid (1 mol/l, 7.24 ml) dropwise under vigorous stirring to obtain acidic silica sol with pH value of 6.
Commercially obtained dispalboehmite sol (20 wt %) was diluted with DDI water to obtain alumina sol with the concentration of 1-15 wt %.
Titanium isopropoxide (10 ml) was dissolved in isopropanol (23.6 ml), followed by adding HNO3 (2 mol/l, 3.4 ml) and DDI water (31.4 ml) under vigorous stirring to obtain an opaque suspension. The suspension was further stirred at 80° C. to evaporate the isopropanol and to peptize the titania precipitate. This was followed by cooling down to room temperature and stirring for overnight to obtain a clear titania sol (1 mol/l).
Copper (II) nitrate was dissolved in DDI water, followed by adding sodium citrate aqueous solution to prepare copper (II) citrate complex sol or aqueous suspension depending on the concentrations of copper (II) nitrate and sodium citrate. The obtained copper (II) citrate complex aqueous suspension was further filtered to obtain a clear copper (II) citrate complex sol.
Titanium(IV) tetrabutoxide (4.8 g) was hydrolyzed with DDI water (100 ml). The obtained titanium hydroxide precipitate was washed thoroughly with DDI water, and dissolved in hydrogen peroxide (30 wt %, 75 ml) to obtain a transparent orange titanium peroxo-complex sol. The sol was diluted with water to obtain the solution of different concentrations.
Zinc sulfate was dissolved in DDI water, followed by the addition of sodium hydroxide solution with slightly lower stoichiometric ratio to prepare a zinc hydroxide precipitate. The obtained zinc hydroxide precipitate was washed with DDI water and redispersed in a citric acid aqueous solution. The obtained mixture was further stirred for overnight and filtered to obtain a clear zinc citrate complex sol.
Silver nitrate was dissolved in DDI water in a brown bottle, followed by adding an ascorbic acid aqueous solution under vigorous stirring to obtain a silver/silver-ascorbic acid complex sol.
Biocide mixture from Examples 6-10 was added dropwise into a mixed suspension/solution containing a polymer used in Examples 11 and 12 and an inorganic material (Examples 13-21) under vigorous stirring. The mixture was then ultrasonic-treated for 1 minute to form an inorganic-organic shell.
Biocide mixture from Examples 6-10 was added dropwise into a mixed solution containing a polymer used in Examples 11 and 12 and a metal alkoxide under vigorous stirring. The mixture was then ultrasonic-treated for 1 minute to form an inorganic-organic shell by a hybrid of inorganic network interpenetrating the organic network.
Biocide mixture from Examples 6-10 was added dropwise into a polymeric organosilicon (e.g., polydimethylsiloxane) under vigorous stirring. The mixture was ultrasonic-treated for 1 minute to form an inorganic-organic shell formed by a molecularly mixed inorganic-organic network.
Polymer-encapsulated biocide from Examples 11 & 12 was added dropwise into secondary polymer solution under vigorous stirring. The secondary polymer can be PEG, PVA, PVP, PEI, PEO-PPO-PEO used in Examples 11 & 12 and a combination of two and more thereof. The mixture was then ultrasonic-treated for 1 minute to form capsule-in-capsule encapsulation with innermost polymer shell and outermost polymer shell.
In
Encapsulated biocide from Examples 22-24 was added dropwise into secondary polymer solution under vigorous stirring. The secondary polymer can be PEG, PVA, PVP, PEI, PEO-PPO-PEO. The mixture was then ultrasonic-treated for 1 minute to form an inorganic-organic inner shell with an outermost organic shell.
Encapsulated biocide from Examples 11 and 12 was added dropwise into a mixed suspension/solution containing a polymer used in Examples 11 and 12 and an inorganic material (Examples 13-21) involved in Example 22, a mixed solution containing a polymer used in Examples 11 and 12 and a metal alkoxide involved in Example 23, and a polymeric organosilicon involved in Example 24 under vigorous stirring. The mixture was then ultrasonic-treated for 1 minute to form an innermost organic shell and an outmost inorganic-organic shell.
Encapsulated biocide from Examples 22-24 was added dropwise into a mixed suspension/solution containing a polymer used in Examples 11 and 12 and an inorganic material (Examples 13-21) in Example 22, a mixed solution containing a polymer used in Examples 11 and 12 and a metal alkoxide involved in Example 23, and a polymeric organosilicon involved in Example 24 under vigorous stirring. The mixture was then ultrasonic-treated for 1 minute to form an innermost inorganic-organic shell and an outermost inorganic-organic shell.
A material according to any of the above Examples was wiped/brushed uniformly onto porous materials and porous media, followed by drying in a fume hood. The brushing and drying processes were repeated for several times to reach the expected loading.
A material according to any of the above Examples was cast on porous materials and porous media, followed by drying in a fume hood. The volume of emulsion is ca. 600 ml for per square meter of porous materials and porous media.
Porous materials and porous media were first immersed into a material according to any of the above Examples for 30 seconds, followed by removal with a constant rate (typically 1 min/s) and drying in a fume hood.
A material according to any of the above Examples was added on spinning porous materials and porous media to obtain antimicrobial coating. A typical spinning speed is 1000 rpm.
A material according to any of the above Examples was distributed uniformly on porous materials and porous media through a spray nozzle to obtain antimicrobial coating.
Porous materials and porous media with the instant antimicrobial coating prepared according to Examples 28-32 were cut into small pieces with the diameter of 15 mm. Then these pieces were placed into the flasks with the mixture of potassium iodide solution (2.5% (w/v), 40 ml) and sulphuric acid solution (50 wt %, 1 ml). The flasks were kept in the dark for 10 minutes, followed by titration with sodium thiosulphate solution (0.001 mol/l) until the color changed into light yellow. Starch solution (0.5% (w/v), 1 ml) was added in the flasks as an indicator. Titration was continued with sodium thiosulphate solution (0.001 mol/l) until the color changed from blue to colorless. The remaining ClO2 amounts within porous materials and porous media with antimicrobial coating were calculated according to the volume of consumed sodium thiosulphate solution.
Separate bacterium/mold suspensions (0.1 ml) were inoculated on tryptone soya agar plates. Porous materials and porous media with antimicrobial coating were cut into pieces with a 15 mm diameter and placed on the center of inoculated plates. The plates were incubated at room temperature 96 hours (Cladosporium) or for 48 hours (E. coli, MRSA and S. aureus), respectively. The inhibition zone size was calculated from the radius of clear annulus without mold or bacterial colony.
Separate bacterium suspensions (0.1 ml) were spread evenly on glass slides, porous materials and porous media without/with antimicrobial coating for different time. Then the slides, porous materials and porous media were immersed in a culture tube containing neutralizer (20 ml) for 30 minutes to stabilize and wash off the still surviving bacteria from the surface. The neutralizer solutions collecting bacteria were inoculated on tryptone soya agar plates for viable culturing. The plates were incubated at 37° C. for 24 hours. The viable bacteria were enumerated from formed colony number.
Separate virus suspensions (0.1 ml) were spread evenly on HEPA filters without/with antimicrobial coating for different time. Then the HEPA filters were immersed in a culture tube containing neutralizer (20 ml) for 30 minutes to stabilize and wash off the still surviving virus from the surface. The plaque assay (Madin-Darby canine kidney cell line for H1N1 and H3N2 influenza viruses, Buffalo green monkey epithelial cell line for Enterovirus 71) was performed to determine viable virus concentration.
The present patent application claims priority to provisional U.S. Patent Application No. 62/071,276 filed Sep. 19, 2014, which was filed by the inventor hereof and is incorporated by reference herein in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2015/089621 | 9/15/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62071276 | Sep 2014 | US |
