Anti-microbial foams containing polymer-stabilized silver nanoparticles

Abstract

An absorbent wound dressing comprises a hydrophilic porous substrate and polymer-stabilized silver nanoparticles distributed throughout the porous substrate. The silver nanoparticles have a particle size d.sub.50 in the range of about 45 nm to about 85 nm and the silver nanoparticles are present in the substrate in an amount of about 0.16% to about 1.5% by weight of the total weight of the substrate. The wound dressing produces a 7-day log reduction of 4 or more for bacteria in accordance with the Modified AATCC Test Method 100. The wound dressing is also non-cytotoxic in accordance with ISO 10993-5 standard procedure for medical device cytotoxicity assessment.

Claims

1. A method for preparing a wound dressing comprising: mixing a prepolymer and an aqueous solution comprising an aqueous dispersion of polymer-stabilized silver nanoparticles in deionized water to produce a polyurethane emulsion; and curing the polyurethane emulsion to produce a three-dimensional, porous substrate having the polymer-stabilized silver nanoparticles distributed throughout the substrate; wherein the prepolymer is selected from the group consisting of an isocyanate-capped polyether, an isocyanate-capped polyester, and combinations thereof.

2. The method of claim 1, wherein the polymer-stabilized silver nanoparticles have a particle size d50 of about 45 nm to about 85 nm.

3. The method of claim 1, wherein the silver nanoparticles are present in an amount from about 0.16% to about 2.0% by weight of the substrate.

4. The method of claim 3, wherein the silver nanoparticles are present in an amount from about 0.75% to about 1.5% by weight of the substrate.

5. The method of claim 1, wherein the aqueous dispersion further comprises one or a combination of polyhexamethylene biguanide (PHMB) and chlorhexidine gluconate (CHG).

6. The method of claim 1, further comprising providing the polyurethane emulsion between casting liners to a desired thickness and width before the curing.

7. The method of claim 1, wherein the polyurethane emulsion is dispensed into a three-dimensional mold to form a desired three-dimensional configuration before the curing.

8. The method of claim 1, further comprising drying the three-dimensional, porous substrate.

9. The method of claim 1, where in the polymer-stabilized silver nanoparticles are distributed substantially uniformly throughout the substrate.

10. The method of claim 1, wherein the three-dimensional, porous substrate is produced without catalysts.

11. A method for preparing a wound dressing comprising: mixing a prepolymer and a hydrophilic polyol component comprising an aqueous dispersion of polymer-stabilized silver nanoparticles in deionized water to produce a polyurethane emulsion; and curing the polyurethane emulsion in a desired three-dimensional configuration to produce a porous substrate having the polymer-stabilized silver nanoparticles distributed throughout the substrate; wherein the prepolymer is selected from the group consisting of an isocyanate-capped polyether, an isocyanate-capped polyester, and combinations thereof.

12. The method of claim 11, wherein the polymer-stabilized silver nanoparticles have a particle size d50 of about 45 nm to about 85 nm.

13. The method of claim 11, wherein the silver nanoparticles are present in an amount from about 0.16% to about 2.0% by weight of the substrate.

14. The method of claim 13, wherein the silver nanoparticles are present in an amount from about 0.75% to about 1.5% by weight of the substrate.

15. The method of claim 11, wherein the aqueous dispersion further comprises one or a combination of polyhexamethylene biguanide (PHMB) and chlorhexidine gluconate (CHG).

16. The method of claim 11, further comprising providing the polyurethane emulsion between casting liners to a desired thickness and width before the curing.

17. The method of claim 11, wherein the polyurethane emulsion is dispensed into a three-dimensional mold to form a desired three-dimensional configuration before the curing.

18. The method of claim 11, further comprising drying the three-dimensional, porous substrate.

19. The method of claim 11, wherein the polymer-stabilized silver nanoparticles are distributed substantially uniformly throughout the substrate.

20. The method of claim 11, wherein the three-dimensional, porous substrate is produced without catalysts.

Description

EXAMPLE 1

Preparation of the Anti-Bacterial/Anti-Fungal Foams

(1) Hydrophilic polyurethane foams having a thickness of 5.00.5 mm were prepared with varying amounts of the polymer-stabilized silver nanoparticles as described herein.

(2) An isocyanate-terminated prepolymer was mixed with an aqueous component comprising a predetermined amount of the polymer-stabilized silver nanoparticle dispersion in deionized water. The resultant mixture or polyurethane emulsion was dispensed onto a moving bottom casting liner of the production line and sandwiched between a moving top casting liner. The top and bottom casting liners were removed at the end of the production line after the foam material is tack-free. The foam material can then be dried in an oven or similar device.

(3) In X80244, the aqueous component was prepared to produce a form that comprised 0.16% of polymer-stabilized silver nanoparticles in the dry foam. The aqueous component was mixed with an isocyanate-terminated prepolymer having an isocyanate content in the range of about 9% to about 10%. In X80245, CJNB#9-50(3), CJNB#9-52(3), CJNB#9-64, and CJNB#9-76, the same process was used, with the exception that the isocyanate-terminated prepolymer had an isocyanate content of about 6% to about 7%. The resulting polyurethane was poured onto the bottom casing liner and cast between top and bottom casting liners as described above.

(4) The physical and absorbent characteristics are set forth in Table 1 below:

(5) TABLE-US-00001 TABLE 1 Physical and Absorbent Characteristics of Polymer-Stabilized Silver Nanoparticle Foams. CJNB CJNB CJNB X80244 X80245 #9-50(3) #9-52(3) #9-64 0.16% 0.18% 0.75% 1.5% 1.25% nanosilver nanosilver nanosilver nanosilver nanosilver PROPERTY in dry foam in dry foam in dry foam in dry foam in dry foam Density (lbs/ft.sup.3) 4.92 6.09 6.46 6.76 6.92 Tensile Strength (psi) 46.23 13.25 12.33 14.59 15.46 Elongation at Break 177 273 243 276 269 (%) Tear Strength (lbs/in) 3.12 1.90 1.99 2.08 1.98 Absorption Rate of a 1 1 1 1 1 Water Drop (sec) Free Swell Absorptive 18.9 17.6 16.62 16.28 16.8 Capacity (g/g) Volume Expansion (%) 65 86 88 95 101 Fluid Retention Under 11.41 9.98 9.72 10.15 10.04 40 mm Hg Compression (g/g)

(6) Physical characteristics were measured as per ASTM standard D3574.

(7) Absorption rate of a water drop is the time to absorb a drop of water into foam substrate. The anti-microbial foams described herein take about 1 sec to absorb a drop of water into foam substrate indicating instantaneous absorption/wicking rate.

(8) Absorptive capacity of the foam is measured as per British Standard, BS EN 13726-1:2002, Test methods for primary wound dressingsPart 1: Aspects of Absorbency, Section 3.2: Free swell absorptive capacity. As shown in the results, the foam substrates can absorb 16-19 times of its own weight when in contact with a saline solution with the volume expansion of the foam from 65to slightly over 100%. High absorptive capacity is advantageous as it would absorb exudates and move fluid away from the wound/skin interface towards the dressing layer.

(9) Fluid retention under compression of 40 mm Hg pressure indicates the typical compression created by a bandage when wrap around the wound dressing. Results indicate that even under compression of 40 mm Hg pressure, foam still keeps a larger amount of exudate trapped inside the foam (without releasing back to wound bed) providing faster healing through exudate management.

(10) Anti-microbial agents can be provided or incorporated in the foam substrates described herein to control the wound bioburden in critical colonization and local infection.

EXAMPLE 2

In Vitro Cytotoxicity Tests

(11) A Minimal Essential Media (MEM) elution test was performed to determine the cytotoxicity of extractable substances. An extract of the test article was added to cell monolayers and incubated. The cell monolayers were examined and scored based on the degree of cellular destruction. All test method acceptance criteria were met. Testing was performed in compliance with U.S. FDA good manufacturing practice regulations 21 CFR Parts 210, 211 and 820.

(12) Procedure. The amounts of test article and controls extracted were based on ANSI/AAMI/ISO and USP surface area or weight recommendations. Test articles and controls were extracted in 1 MEM with 5% bovine serum for 24-25 hours at 371 C. with agitation. Multiple well cell culture plates were seeded with a verified quantity of industry standard L-929 cells (AC CCL-1) and incubated until approximately 80% confluent. The test article and control extracts were held at room temperature for less than four hours before testing. The extract fluids were not filtered, centrifuged or manipulated in any way following the extraction process. The test article and control extracts were added to the cell monolayers in triplicate. The cells were incubated at 371 C. with 51% CO.sub.2 for 483 hours.

(13) Acceptance Criteria. The United States Pharmacopeia & National Formulary (USP <87>) states that the test article meets the requirements, or receives a passing score (Pass) if the reactivity grade is not greater than 2 or a mild reactivity. The ANSI/AAMI/ISO 10993-5 standard states that the achievement of a numerical grade greater than 2 is considered a cytotoxic effect, or a failing score (Fail).

(14) TABLE-US-00002 TABLE 2 Culture Scores. Conditions of All cultures Reactivity Score No cell lysis, intracytoplastic granules None 0 Less than or equal to 20% rounding, occasional Slight 1 lysed cells Greater than 20% to less than or equal to 50% Mild 2 rounding, no extensive cell lysis Greater than 50% to less than 70% rounding Moderate 3 and lysed cell Nearly complete destruction of the cell layers Severe 4

(15) The acceptance criteria was based upon the negative and media controls receiving 0 reactivity grades and the positive controls receiving a 3-4 reactivity grades (moderate to severe). The test was considered valid as the control results were within acceptable parameters.

(16) TABLE-US-00003 TABLE 3 Negative, Media and Positive Control Scores. Amt. Scores Extraction Tested/Extraction Controls #1 #2 #3 Avg. Ratio Solvent Amt. Negative Control - 0 0 0 0 0.2 g/ml 4 g/20 ml polypropylene pellets Media Control 0 0 0 0 N/A 20 ml Positive Control - 4 4 4 4 0.2 g/ml 4.0 g/20 ml Latex Natural Rubber

(17) The cell monolayers were examined microscopically. The wells were scored as to the degree of discernable morphological cytotoxicity on a relative scale of 0 to 4.

(18) TABLE-US-00004 TABLE 4 In vitro Cytotoxicity Test Scores. Amt. Tested/ Extraction Scores Extraction Solvent Test Article #1 #2 #3 Avg. Result Ratio Amt. 3M Tegaderm 4 4 4 4 Fail 0.1 g/ml 0.6 g/6 ml AG Silver Sulfate Mesh 2 in. 2 in. Contreet AG 3 3 3 3 Fail 0.1 g/ml 2.0 g/20 ml Silver Foam Dressing, 4 in. 4 in. Acticoat 4 4 4 4 Fail 0.1 g/ml 2.0 g/20 ml Absorbent w/avec Silcryst Nanocrystals 4 in. 5 in. Acticoat Flex 3 4 4 4 4 Fail 0.1 g/ml 0.9 g/9.0 ml w/avec. Silcrys Nanocrystals 2 in. 2 in. Mepilex Ag 4 4 4 4 Fail 0.1 g/ml 2.0 g/20 ml with Safetac Technology, 4 in. 4 in. Essentra 0.17% 0 0 0 0 Pass 0.1 g/ml 2.0 g/20 ml nanosilver in dry foam CJNB#9-24C Essentra 1.25% 2 2 2 2 Pass 0.1 g/ml 2.0 g/20 ml nanosilver in dry foam CJNB#9-64 Essentra 1.5% 0 0 1 0 Pass 0.1 g/ml 2.0 g/20 ml nanosilver in dry foam CJNB#9-70 Essentra 1.5% 1 1 0 1 Pass 0.1 g/ml 2.0 g/20 ml Nanosilver in dry foam CJNB#9-71

EXAMPLE 3

In Vitro Anti-Bacterial Tests for X80244 and X80245

(19) The anti-bacterial activity of X80244 and X80245 foams was tested and compared to control foams. The anti-microbial performance of each foam was assessed using the Modified American Association of Textile Colorist and Chemist (AATCC) Test Method 100.

(20) At day zero, samples were prepared and placed in a small Petri dish, which was then placed in a large Petri dish with 10 ml of sterile water to keep the samples in a humid condition. Plates were labeled with sample identification, time point and organism name. Each challenge organism was adjusted to 1-510.sup.6 CFU/ml using a spectrophotometer (Staphylococcus aureus (ATCC 25922 or equivalent), Klesbsiella pneumoniae (ATCC 4352 or equivalent), Pseudomonas aeruginosa (ATCC 9027 or equivalent).

(21) Zero hour samples were inoculated with 1.0 ml of the challenge organism and immediately neutralized with 100 ml of D/E neutralizing broth and appropriate dilutions were made with sterile saline and each dilution was plated in duplicate. Plates were incubated for 24-48 hours at 372 C. Twenty-four hour samples were individually inoculated with 1.0 ml of the specified population of the challenge organism, while two sets of 3 day and 7 day samples (one set for zero hour and one set for 24 hour) were conditioned with 0.1 ml of 10% fetal bovine serum (FBS) in sterile deionized water. Samples were then incubated at 372 C.

(22) After 24 hours of incubation, 24 hour samples were removed, neutralized with 100 ml of neutralizer and appropriate dilutions were made with sterile saline and each dilution was plated in duplicate. The 3 and 7 day samples were conditioned with 0.1 ml of 10% FBS each day and aged at 372 C. until the testing point. At 3 day and 7 day time point a new set of inoculum was prepared and each sample was inoculated with the specified population of challenge organism. One set of samples was inoculated, immediately neutralized and plated for zero hour. A second set was inoculated and placed in the incubator at 372 C. for 24 hours.

(23) After incubation, each sample was individually neutralized with 100 ml of neutralizer. Appropriate dilutions were made with sterile saline and each dilution was plated in duplicate.

(24) TABLE-US-00005 TABLE 5 Anti-Bacterial Results after 24 hours. Log Percent Sample ID Zero time 24 Hour Reduction Reduction S. aureus X80245 Silver 1.85 10.sup.6 4.40 10.sup.4 2.83 99.85 0.18% silver Control 2.35 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction X80244 Silver 2.15 10.sup.6 5.85 10.sup.4 2.71 99.81 0.16% silver Control 1.95 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction K. pneumoniae X80245 Silver 1.95 10.sup.6 5.00 10.sup.1 5.78 99.99 0.18% silver Control 2.20 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction X80244 Silver 1.95 10.sup.6 6.90 10.sup.2 4.64 99.99 0.16% silver Control 1.85 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction P. aeruginosa X80245 Silver 2.10 10.sup.6 <1.00 10.sup.1 >6.48 >99.99 0.18% silver Control 2.30 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction X80244 Silver 2.10 10.sup.6 4.80 10.sup.3 3.80 99.98 0.16% silver Control 1.90 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction

(25) The polymer-stabilized silver nanoparticle foam having 0.16% and 0.18% of silver nanoparticles by weight of the foam demonstrated 24-hour log reductions of 2.71 and 2.83 for S. aureus, log reductions of 4.64 and 5.78 for K. pneumoniae, and log reductions of 3.80 and >6.48 for P. aeruginosa.

(26) TABLE-US-00006 TABLE 6 Anti-Bacterial Results after 3 Days. Log Percent Sample ID Zero time 3 Day Reduction Reduction S. aureus X80245 Silver 1.50 10.sup.6 6.65 10.sup.3 3.65 99.98 0.18% silver Control 2.50 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction X80244 Silver 2.35 10.sup.6 3.25 10.sup.4 2.97 99.89 0.16% silver Control 1.80 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction K. pneumoniae X80245 Silver 2.20 10.sup.6 <1.00 10.sup.1 >6.48 >99.99 0.18% silver Control 2.40 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction X80244 Silver 2.35 10.sup.6 5.15 10.sup.4 2.77 99.83 0.16% silver Control 1.60 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction P. aeruginosa X80245 Silver 1.40 10.sup.6 <1.00 10.sup.1 >6.48 >99.99 0.18% silver Control 1.90 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction X80244 Silver 1.55 10.sup.6 3.30 10.sup.5 1.96 98.90 0.16% silver Control 2.45 10.sup.6 >3.00 10.sup.7 No Reduction No Reduction

(27) The polymer-stabilized silver nanoparticle foam having 0.16% and 0.18% of silver nanoparticles by weight of the foam demonstrated 3-day log reductions of 2.97 and 3.65 for S. aureus, log reductions of 2.77 and >6.48 for K. pneumoniae, and log reductions of 1.96 and >6.48 for P. aeruginosa.

(28) TABLE-US-00007 TABLE 7 Anti-Bacterial Results after 7 Days. Log Percent Sample ID Zero time 7 Day Reduction Reduction S. aureus X80245 Silver 1.75 10.sup.6 2.50 10.sup.4 4.89 99.99 0.18% silver Control 1.75 10.sup.6 1.95 10.sup.9 No Reduction No Reduction X80244 Silver 1.85 10.sup.6 3.80 10.sup.4 5.12 99.99 0.16% silver Control 2.00 10.sup.6 5.00 10.sup.9 No Reduction No Reduction K. pneumoniae X80245 Silver 1.20 10.sup.6 1.65 10.sup.5 3.80 99.98 0.18% silver Control 1.25 10.sup.6 1.05 10.sup.9 No Reduction No Reduction X80244 Silver 1.65 10.sup.6 3.05 10.sup.4 5.19 99.99 0.16% silver Control 1.75 10.sup.6 4.75 10.sup.9 No Reduction No Reduction P. aeruginosa X80245 Silver 1.65 10.sup.6 2.65 10.sup.5 6.57 99.99 0.18% silver Control 1.75 10.sup.6 .sup.9.80 10.sup.11 No Reduction No Reduction X80244 Silver 1.95 10.sup.6 1.75 10.sup.8 3.17 99.93 0.16% silver Control 1.85 10.sup.6 .sup.2.60 10.sup.11 No Reduction No Reduction

(29) The polymer-stabilized silver nanoparticle foam having 0.16% and 0.18% of silver nanoparticles by weight of the foam demonstrated 7-day log reductions of 5.12 and 4.89 for S. aureus, log reductions of 5.19 and 3.8 for K pneumoniae, and log reductions of 3.17 and 6.57 for P. aeruginosa.

EXAMPLE 4

In Vitro Anti-Bacterial Tests for CJNB#9-50(3) and CJNB#9-52(3)

(30) The anti-bacterial activity of hydrophilic foams utilizing different amounts of silver nanoparticles were also compared using the same protocol as described above with respect to Example 3. The test samples (CJNB#9-50(3) and CJNB#9-52(3)) contained an amount of silver at 0.75% and 1.5% by weight of the dry foam, respectively.

(31) TABLE-US-00008 TABLE 8 Anti-Bacterial Results after 24 hours. Results (CFU/sample) Percent Reduction/Log Day-0 Zero Contact Time 24 Hour Contact Time Reduction Sample ID S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae Control 1.34 10.sup.6 1.56 10.sup.6 7.65 10.sup.6 8.70 10.sup.6 Not Not Applicable Applicable CJNB#9- 1.65 10.sup.6 1.35 10.sup.6 7.45 10.sup.2 <1.00 10.sup.1 99.99/ >99.99/ 50(3) 4.01 >5.94 0.75% Ag CJNB#9- 1.50 10.sup.6 1.25 10.sup.6 <1.00 10.sup.1 <1.00 10.sup.1 >99.99/ >99.99/ 52(3) >5.88 >5.94 1.5% Ag P. aeruginosa P. aeruginosa P. aeruginosa Control 1.06 10.sup.6 3.95 10.sup.6 Not Applicable CJNB#9- 1.45 10.sup.6 <1.00 10.sup.1 >99.99/>5.60 50(3) 0.75% Ag CJNB#9- 1.40 10.sup.6 <1.00 10.sup.1 >99.99/>5.60 52(3) 1.5%

(32) After 24 hours, the polymer-stabilized silver nanoparticle foam having 0.75% by weight of foam of silver nanoparticles demonstrated 24-hour log reductions of about 4.01 for S. aureus, >5.94 for K. pneumoniae, and >5.60 for P. aeruginosa. The polymer-stabilized silver nanoparticle foam having 1.50% by weight of foam of silver nanoparticles demonstrated 24-hour log reductions of about 5.88 for S. aureus, >5.94 for K. pneumoniae, and >5.60 for P. aeruginosa.

(33) TABLE-US-00009 TABLE 9 Anti-Bacterial Results after 3 days. Results (CFU/sample) Percent Reduction/Log Day-3 Zero Contact Time 24 Hour Contact Time Reduction Sample ID S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae Control 1.40 10.sup.6 1.55 10.sup.6 2.30 10.sup.7 2.55 10.sup.8 Not Not Applicable Applicable CJNB#9- 2.20 10.sup.6 2.20 10.sup.6 <1.00 10.sup.1 <1.00 10.sup.1 >99.99/ >99.99/ 50(3) >6.36 >7.41 0.75% Ag CJNB#9- 2.00 10.sup.6 1.50 10.sup.6 <1.00 10.sup.1 <1.00 10.sup.1 >99.99/ >99.99/ 52(3) >6.36 >7.41 1.5% Ag P. aeruginosa P. aeruginosa P. aeruginosa Control 2.20 10.sup.6 2.55 10.sup.8 Not Applicable CJNB#9- 1.75 10.sup.6 <1.00 10.sup.1 >99.99/>7.41 50(3) 0.75% Ag CJNB#9- 2.60 10.sup.6 <1.00 10.sup.1 >99.99/>7.41 52(3) 1.5%

(34) After 3 days, the polymer-stabilized silver nanoparticle foam having 0.75% by weight of foam of silver nanoparticles demonstrated 3-day log reductions of about >6.36 for S. aureus, >7.41 for K. pneumoniae, and >7.41 for P. aeruginosa. The polymer-stabilized silver nanoparticle foam having 1.50% by weight of foam of silver nanoparticles demonstrated 3-day log reductions of about >6.36 for S. aureus, >7.41 for K. pneumoniae, and >7.41 for P. aeruginosa.

(35) TABLE-US-00010 TABLE 10 Anti-Bacterial Results after 7 days. Results (CFU/sample) Percent Reduction/Log Day-7 Zero Contact Time 24 Hour Contact Time Reduction Sample ID S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae Control 2.80 10.sup.6 2.85 10.sup.6 1.89 10.sup.8 1.31 10.sup.9 Not Not Applicable Applicable CJNB#9- 2.85 10.sup.6 2.60 10.sup.6 3.65 10.sup.2 <1.00 10.sup.1 >99.99/ >99.99/ 50(3) 5.71 >8.12 0.75% Ag CJNB#9- 2.86 10.sup.6 2.45 10.sup.6 <1.00 10.sup.1 <1.00 10.sup.1 >99.99/ >99.99/ 52(3) >7.28 >8.12 1.5% Ag P. aeruginosa P. aeruginosa P. aeruginosa Control 2.85 10.sup.6 4.05 10.sup.8 Not Applicable CJNB#9- 2.55 10.sup.6 <1.00 10.sup.1 >99.99/>7.61 50(3) 0.75% Ag CJNB#9- 2.35 10.sup.6 <1.00 10.sup.1 >99.99/>7.61 52(3) 1.5%

(36) After 7 days, the polymer-stabilized silver nanoparticle foam having 0.75% by weight of foam of silver nanoparticles demonstrated 7-day log reductions of about 5.71 for S. aureus, >8.12 for K. pneumoniae, and >7.61 for P. aeruginosa. The polymer-stabilized silver nanoparticle foam having 1.50% by weight of foam of silver nanoparticles demonstrated 7-day log reductions of about >7.28 for S. aureus, >8.12 for K. pneumoniae, and >7.61 for P. aeruginosa.

EXAMPLE 5

In Vitro Anti-Fungal Test for CJNB#9-52(3)

(37) The anti-fungal activity of CJNB#9-52(3) (1.5% nanosilver in dry foam, 4-5 mm thickness) was tested and evaluated. Specified layers of sample were inoculated evenly with the challenge organism (Candida albicans). After inoculation, samples were incubated at 35-39 C. for 24 hours. Immediately after incubation, zero contact time samples were neutralized with D/E neutralizing broth. Serial dilutions were prepared and plated in duplicate using appropriate media. The 24 hour samples were processed similarly.

(38) All plates were then incubated at 281 C. for 48 hours. The number of organisms per specimen was reported and the percent reduction and log reduction of challenge organisms were calculated.

(39) TABLE-US-00011 TABLE 11 Anti-Fungal Activity after 24 Hours. Results Zero Contact 24 hour Contact % Reduction/ Time Time Log CFU/specimen CFU/specimen Reduction Sample ID C. albicans C. albicans C. albicans CJNB#9-52(3) 2.85 10.sup.6 9.15 10.sup.3 99.68/2.49 1.5% nanosilver

(40) As demonstrated in table above, the nanosilver foam exhibited a 99.68% reduction or a 2.49 log reduction of C. albicans after 24 hours.

EXAMPLE 6

(41) The anti-bacterial activity of CJNB#9-40, which comprises 0.75% polymer-stabilized silver nanoparticles and 0.5% PHMB in dry polyurethane form, was assessed using the same protocol as described above with respect to Example 3.

(42) TABLE-US-00012 TABLE 12 Anti-Bacterial Activity after 24 Hours. Results (CFU/sample) Percent Reduction/Log Day-0 Zero Contact Time 24 Hour Contact Time Reduction Sample ID S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae Control 1.34 10.sup.6 1.55 10.sup.6 7.65 10.sup.6 8.70 10.sup.6 Not Not Applicable Applicable CJNB#9-40 1.50 10.sup.6 1.45 10.sup.6 <1.00 10.sup.1 <1.00 10.sup.1 >99.99/ >99.99/ >5.88 >5.94 P. aeruginosa P. aeruginosa P. aeruginosa Control 1.06 10.sup.6 3.95 10.sup.6 Not Applicable CJNB#9-40 1.35 10.sup.6 <1.00 10.sup.1 >99.99/>5.60

(43) After 24 hours, CJNB#9-40 demonstrated 24-hour log reductions of about >5.88 for S. aureus, >5.94 for K pneumoniae and >5.60 for P. aeruginosa.

(44) TABLE-US-00013 TABLE 13 Anti-Bacterial Activity after 3 Days. Results (CFU/sample) Percent Reduction/Log Day-3 Zero Contact Time 24 Hour Contact Time Reduction Sample ID S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae Control 1.40 10.sup.6 1.55 10.sup.6 2.30 10.sup.7 2.55 10.sup.8 Not Not Applicable Applicable CJNB#9-40 2.75 10.sup.6 2.35 10.sup.6 2.50 10.sup.2 <1.00 10.sup.1 99.99/ >99.99/ 4.96 >7.40 P. aeruginosa P. aeruginosa P. aeruginosa Control 2.20 10.sup.6 2.95 10.sup.8 Not Applicable CJNB#9-40 2.55 10.sup.6 <1.00 10.sup.1 >99.99/>7.47

(45) After 3 days, CJNB#9-40 demonstrated 3-day log reductions of about >4.96 for S. aureus, >7.40 for K. pneumoniae and >7.47 for P. aeruginosa.

(46) TABLE-US-00014 TABLE 14 Anti-Bacterial Activity after 7 Days. Results (CFU/sample) Percent Reduction/Log Day-7 Zero Contact Time 24 Hour Contact Time Reduction Sample ID S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae Control 3.80 10.sup.6 2.85 10.sup.6 1.89 10.sup.8 1.31 10.sup.9 Not Not Applicable Applicable CJNB#9-40 2.95 10.sup.6 2.30 10.sup.6 <1.00 10.sup.1 <1.00 10.sup.1 99.99/ >99.99/ >7.28 >8.12 P. aeruginosa P. aeruginosa P. aeruginosa Control 2.85 10.sup.6 4.05 10.sup.8 Not Applicable CJNB#9-40 3.50 10.sup.6 <1.00 10.sup.1 >99.99/>7.61

(47) After 7 days, CJNB#9-40 demonstrated 7-day log reductions of about >7.28 for S. aureus, >7.61 for K. pneumoniae and >8.12 for P. aeruginosa.

EXAMPLE 7

In Vitro Anti-Bacterial Tests Comparing Silver Particle Sizes

(48) The anti-bacterial activity of hydrophilic foams utilizing different silver particle sizes were also compared using the same protocol as described above with respect to Example 3. Each of the test samples (CJNB#9-76 and CJNB#9-52(3)) contained an amount of silver at 1.5% by weight of the dry foam.

(49) TABLE-US-00015 TABLE 15 Anti-Bacterial Results for S. aureus. Silver Particle Zero Contact 24 Hour Log Size Time Contact Time Reduction CJNB#9-76 15-25 microns 2.95 10.sup.6 3.60 10.sup.4 1.91 CJNB#9-52(3) 30-100 nm 1.50 10.sup.6 <1.00 10.sup.1 >5.26

(50) As can be seen in table above, the foam having the larger silver particle size (CJNB#9-76) had a 24-hour log reduction of 1.91 relative to the initial inoculum concentration of S. aureus as compared to the foam having the smaller silver particle size (CJNB#9-52(3)), which had a significantly larger 24-hour log reduction of >5.26 relative to the initial inoculum concentration for the same organism. The smaller particle size has significantly greater anti-bacterial efficacy as against S. aureus.

(51) TABLE-US-00016 TABLE 16 Anti-Bacterial Results for P. aeruginosa. Silver Particle Zero Contact 24 Hour Log Size Time Contact Time Reduction CJNB#9-76 15-25 microns 1.71 10.sup.6 28.35 10.sup.6 No reduction CJNB#9-52(3) 30-100 nm 1.25 10.sup.6 <1.00 10.sup.1 >5.30

(52) As can be seen in table above, the foam having the larger silver particle size (CJNB#9-76) had no reduction relative to the initial inoculum concentration of P. aeruginosa as compared to the foam having the smaller silver particle size (CJNB#9-52(3)), which had a significantly larger 24-hour log reduction of >5.30 relative to the initial inoculum concentration for the same organism. The larger particle size is demonstrated here to have no anti-bacterial efficacy against P. aeruginosa, while the smaller particle size maintains a significant anti-bacterial efficacy.

(53) TABLE-US-00017 TABLE 17 Anti-Bacterial Results for K. pneumoniae. Silver Particle Zero Contact 24 Hour Log Size Time Contact Time Reduction CJNB#9-76 15-25 microns 1.25 10.sup.6 7.30 102.sup. 3.24 CJNB#9-52(3) 30-100 nm 1.45 10.sup.6 <1.00 10.sup.1 >5.32

(54) As can be seen in table above, the foam having the larger silver particle size (CJNB#9-76) had a 24-hour log reduction of 3.24 relative to the initial inoculum concentration of P. aeruginosa as compared to the foam having the smaller silver particle size (CJNB#9-52(3)), which had a significantly larger 24-hour log reduction of >5.32 relative to the initial inoculum concentration for the same organism. The smaller particle size has significantly greater anti-bacterial efficacy as against K. pneumoniae.

(55) It is to be understood that the detailed description and specific examples, while indicating preferred embodiments of the present disclosure, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present disclosure may be made without departing from the spirit thereof, and the disclosure includes all such modifications.