Method for reducing adhesion of microorganisms to fabrics

Abstract

The present invention relates to a method for finishing fibers and/or fabrics, the intention being to reduce the adhesion of microorganisms, especially of bacteria and/or yeasts, to the fibers and/or fabrics. The method involves applying a composition ZS comprising selected hydrophilic silane derivatives to the fibers and/or fabrics. The invention further relates to a method for the quantitative determination of the adhesion of microorganisms to fibers and/or fabrics.

Claims

1. A method for finishing fibers and/or fabrics, comprising the steps of a) providing a composition ZS comprising at least one hydrophilic silane derivative S of the general formula (I) ##STR00022## where R.sup.1, R.sup.2 and R.sup.3 independently of one another are H or C.sub.1-C.sub.6 alkyl; a is an integer from 1 to 10; R.sup.4 is selected from: ##STR00023## where X is a bond, OT,OTCH(OH), OTCH(OH)T, OC(?O) or OC(?O)T, where T and T independently of one another are selected from C.sub.1-.sub.12 alkylene; R.sup.5 is independently at each occurrence H or C.sub.1-6 alkyl; Y is H; C.sub.1-12 alkyl; C.sub.1-12 hydroxyalkyl, C.sub.1-12 haloalkyl, C.sub.7-20 arylalkyl, C(=O)(C.sub.1-12 alkyl); (CH.sub.2).sub.aSi(OR.sup.1)(OR.sup.2)(OR.sup.3), TO(CH.sub.2).sub.aSi(OR.sup.1)(OR.sup.2)(OR.sup.3); TCH(OH)O(CH.sub.2).sub.aSi(OR.sup.1)(OR.sup.2)(OR.sup.3), or TCH(OH)-TO(CH.sub.2).sub.aSi(OR.sup.1)(OR.sup.2)(OR.sup.3) where R.sup.1, R.sup.2, R.sup.3, T, T and a are as defined above; b is a number from 0 to 20; or ##STR00024## where p=1 to 20 and R.sup.9 is selected from OH, OCH.sub.3, OCH.sub.2CH.sub.3 and NH.sub.2; and optionally at least one solvent L; b) applying the composition ZS to the fibers and/or fabrics; c) optionally washing and/or drying the fibers and/or fabrics.

2. The method as claimed in claim 1 characterized in that R.sup.1, R.sup.2 and R.sup.3 independently of one another are methyl or ethyl and a is 3.

3. The method as claimed in claim 1, characterized in that R.sup.4 is a group selected from:
OCH.sub.2CH.sub.2.sub.bOY(x) where b=2 to 20 and Y is selected from H and C.sub.1-C.sub.6 alkyl;
OY(xi) where Y is selected from H, C.sub.1-6 alkyl and C(?O)(C.sub.1-12 alkyl); ##STR00025## where a is 2 to 6, b is 2 to 10, and R.sup.1, R.sup.2 and R.sup.3 are independently of one another methyl or ethyl; ##STR00026## where a is 2 to 6, b is 2 to 20 and R.sup.1, R.sup.2 and R.sup.3 are independently of one another methyl or ethyl.

4. The method as claimed in claim 1, characterized in that the composition ZS comprises a solvent L selected from the group consisting of water, mono- and polyhydric C1-6 alcohols, glycol, glycol derivatives, polyglycols, polyglycol ethers, ethers and mixtures thereof.

5. The method as claimed in claim 1, characterized in that the composition ZS comprises at least one solvent L selected from the group consisting of water, methyl triglycol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, propylene glycol monomethyl ether, propylene glycol dimethyl ether, propylene glycol monoethyl ether, propylene glycol diethyl ether, methanol, ethanol, propanol and butanol.

6. The method as claimed in claim 1, characterized in that the composition ZS comprises 0.0001 to 10 wt %, based on the overall composition ZS, of the at least one hydrophilic silane derivative S.

7. The method as claimed in claim 1, characterized in that the composition ZS is applied in step b by pad mangle methods, foam application, spraying methods, coating or an exhaust method.

8. The method as claimed in claim 1, characterized in that the fibers and/or fabrics comprise synthetic fibers.

9. The method for finishing fibers and/or fabrics as claimed in claim 1, where the finishing is directed to reducing the accretion of microorganisms onto the fibers and/or fabrics, and where the method comprises the following additional steps for quantitative determination of the accretion of the microorganisms onto the fibers and/or fabrics: a1) preparing an aqueous suspension comprising one or more different microorganisms; b1) contacting the aqueous suspension comprising one or more different microorganisms with the finished fibers and/or fabrics from step b) or c) or with part of the finished fibers and/or fabrics from step b) or c); c1) separating the fibers and/or fabrics from the supernatant suspension and washing the fibers and/or fabrics; d1) removing the accreted microorganisms from the fibers and/or fabrics by exposure to shearing and/or ultrasound and/or enzymes; e1) determining the amount of microorganisms removed.

10. A method for coating a solid substrate with a composition comprising at least one hydrophilic silane derivative S of the general formula (I) as in claim 1, wherein the accretion of microorganisms onto the solid substrate is reduced.

11. The method as claimed in claim 10, characterized in that the solid substrate is a substrate selected from glass, ceramic, plastic, metal, fibers and fabrics.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the results relating to the wash stability of the antiadhesive effect (reduction in adhered bacteria in %) with respect to S. aureus, concerning a silane derivative coating on polyester fabric samples as per example 3.2.

(2) FIG. 2 shows the results relating to the wash stability of the antiadhesive effect (reduction in adhered bacteria in %) with respect to P. aeruginosa, concerning a silane derivative coating on polyester fabric samples as per example 3.2.

(3) The abbreviations in FIGS. 1 and 2 are elucidated below:

(4) S2, S3 and S5 denote the corresponding hydrophilic silane derivatives S2, S3 and S5, or polyester fabric samples as per example 3.2 that have been coated with the corresponding silane derivatives;

(5) A, B, and C denote the corresponding pretreatments of the polyester fabric samples (A), (B) and (C) as per example 3.2, i.e., A denotes an unwashed fabric sample; B denotes a fabric sample washed twice at 30? C. just with water, without addition of a detergent; C denotes a fabric sample washed once at 30? C. in accordance with laundry standard EN ISO 6330, method 8A, with addition of an ECE B detergent.

(6) Furthermore, the numbers 0.1; 0.01 and 0.001 denote the corresponding coating concentrations of 0.1 wt %; 0.01 wt % and 0.001 wt % of hydrophilic silane derivative S, based on the weight of the coated textile material.

(7) The invention is elucidated in more detail by the claims and by the examples below:

EXAMPLE 1

Coating of Polyester Fabric Samples

(8) A 10 wt % strength solution of each of the hydrophilic silane derivatives S1 to S4 identified below in methyl triglycol (triethylene glycol monomethyl ether, 2-[2-(2-methoxyethoxy)ethoxy]ethanol was prepared. The hydrophilic silane derivative S5 was dissolved in water to give a 10 wt % strength solution.

(9) Hydrophilic silane derivatives S tested S1 methoxy(polyethyleneoxy)propyltrimethoxysilane (9-12 EO units); (manufacturer: Gelest, SIM 6492 72) S2 bis[3-(triethoxysilylpropoxy)-2-hydroxypropoxy)]polyethylene oxide (5-10 EO units); (manufacturer: Gelest, SIB 1824.2) S3 N-(triethoxysilylpropyl)-O-polyethylene oxide-urethane, (4-6 EO units); (manufacturer: Gelest, SIT 8192.0) S4 N-(triethoxysilylpropyl)gluconamide (50% strength solution in ethanol) (manufacturer: Gelest, SIT 8189.0) S5 N-(trimethoxysilylpropyl)ethylenediaminetriacetyl acid, trisodium salt (45% strength solution in water) (manufacturer: Gelest, SIT 8402.0)

(10) The structural formulae of the hydrophilic silane derivatives S1 to S5 are indicated above in the formulae (S1) to (S5).

(11) The above-described solutions (compositions ZS) were applied by a padding method to polyester fabric samples to give application concentrations on the fabric of 0.1 wt %, 0.01 wt % or 0.001 wt % of hydrophilic silane derivative S, based on the total amount of the coated fabric.

(12) In an alternative procedure, the commercial products identified above were applied directly by a padding method to polyester fabric samples to give application concentrations on the fabric of 0.1 wt %, 0.01 wt % or 0.001 wt % of hydrophilic silane derivative S, based on the total amount of the coated fabric.

EXAMPLE 2

Method for the Quantitative Determination of the Adhesion of Microorganisms to Fabrics (Syto9 Assay)

(13) 2.1 Production of the Fabric Titer Plates

(14) Circular fabric samples with a diameter of 0.6 cm were punched from coated and uncoated cotton and polyester fabrics. The fabric samples were fixed to a microtiter plate. The fabric samples were washed with acetone and sterilized with UV light for 60 minutes.

(15) 2.2 Bacterial Culture and Bacterial Propagation

(16) Model microorganisms used were various gram-positive and gram-negative bacteria and yeasts, more particularly Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Staphylococcus epidermidis (S. epidermidis) and Candida albicans (C. albicans).

(17) The strains were coated fresh from glycerol bacterial cultures onto tryptic soy agar (TSA). Incubation took place overnight at 33? C. The nutrient medium prepared was a tryptic soy broth (TSB), with 30% of the amount recommended by the manufacturer, supplemented with 0.25% of glucose. The nutrient medium had a pH of 7 to 7.2. The nutrient medium was inoculated with the bacterial cultures and after inoculation was cultivated overnight at 37? C. and 160 rpm.

(18) The resulting overnight cultures were centrifuged at 8500 g for 15 minutes and washed with 50 ml of isotonic saline solution (0.9 wt %). Bacterial suspensions in isotonic saline solutions were prepared. The optical density of the various bacterial suspensions was determined at 595 nm and adjusted to a level of about 1.2.

(19) 2.3 Calibration

(20) In order to be able to correlate the colony-forming units (CFU) and the relative fluorescence units (RFU) in a standard plot, dilution series of the various microorganisms with five-fold dilution were prepared (80 m isotonic saline solution and 20 m microorganism solution). Drops each of 5 ?l of the diluted solutions were applied dropwise to three different agar plates (nutrient agar, plate count agar, and tryptic soy agar). The agar plates were incubated with rotation overnight at 33? C. The colony-forming unit count (CFU/ml) was determined on the following day.

(21) In the case of staining with Syto9 (Life Sciences), the same dilution series were prepared for the same time in a black polystyrene plate.

(22) 2.4 Biofilm Formation

(23) 50 ?l of the final microorganism suspension in isotonic saline solution (0.9 wt %) prepared as described under 2.2 were added to the coated and uncoated fabric samples fixed on the microtiter plate (see 2.1). The microtiter plates were closed and sealed off with Parafilm. The microtiter plates were placed in an antievaporation box and incubated at 33? C. for 2 h and at 40 rpm. The expected colony-forming unit count (CFU) of the inoculum at the start was 10.sup.6-10.sup.7 CFU/ml.

(24) After the biofilm had formed, the planctonic cells were removed and used as a sample for determining the optical density at 595 nm. For this purpose, the samples were made up to a volume of 150 ?l, and 100 ?l were withdrawn for the optical density determination in a photometer. The optical density of the corresponding control solution with sterile isotonic saline solution was subtracted from the optical densities found. Through the determination of the planctonic cells after the formation of biofilm, the amount of bacteria available for adhesion was monitored.

(25) The fabric samples and the resulting biofilm were washed three times with 200 to 300 ?l of isotonic saline solution.

(26) 2.5 Mechanical or Enzymatic Removal of the Adhered Microorganisms

(27) The fabric samples obtained under 2.4 (after formation of biofilm) were placed together with 100 ?l of isotonic saline solution into wells of a 96-well microtiter plate.

(28) Investigations into the removal of the adhered microorganisms from the fabric surfaces were carried out with vortexing, ultrasound, with enzymatic treatment, or with combinations thereof. Treatment in the vortex amounted to 5 minutes and was performed horizontally. The ultrasound treatment was carried out in an ultrasound bath for 5 minutes. For the enzymatic removal, the fabric samples were treated with enzymes, such as trypsin or a mixture of different enzymes, for example, during incubation at 37? C. for 1 hour.

(29) Following removal of the adhered bacteria, the fabric samples were removed from the microtiter plates.

(30) The number of removed bacteria in the resulting suspension was determined by staining with Syto9 and fluorescence measurement (fluorescence filter with excitation at 485/20 nm and emission at 528/20 nm) or by staining with BacTiterGlo and bioluminescence measurement. Furthermore, it is possible to determine the number of adhered and removed microorganisms by means of protein assay (e.g., BCA assay, Bradford Assay) or optical density proliferation assay.

(31) The relative variables (e.g., fluorescence units (RFU)) concerning the coated and uncoated fabrics were compared, allowing the reduction in adhered bacteria in % to be determined in accordance with the following formula:
Reduction in adhered bacteria[%]=[(RFU.sub.uc?RFU.sub.uc)/RFU.sub.uc]*100
where RFU.sub.uc=relative fluorescence units of the removed bacteria of the uncoated substrate RFU.sub.c=relative fluorescence units of the removed bacteria of the coated substrate

(32) The statistical significance of each data series was ascertained. The relative measurement units (e.g., relative fluorescence units (RFU)) can be correlated with the aid of calibration plots (see 2.3) to the colony-forming units per ml (CFU/ml).

EXAMPLE 3

Investigation of the Finished Polyester Fabric Samples

(33) 3.1 Determinations of the Antiadhesive Effect with Respect to Various Microorganisms

(34) As described in example 1, polyester fabric samples were each finished with a hydrophilic silane derivative S1 to S5, to give application concentrations on the fabric of 0.1 wt % (hydrophilic silane derivative S, based on total amount of coated fabric). The commercial products described in example 1 were applied directly by a padding method to polyester fabric samples.

(35) Bacterial adhesion to the polyester fabric samples was investigated using the microtiter plate Syto9 assay, as described in example 2.

(36) For this purpose, polyester fabric samples with a diameter of 0.6 cm were punched out and transferred to a 96-well microtiter plate. The adhesion of S. aureus DSMZ 20231 and P. aeruginosa DSMZ 1117as representative examples of gram-positive and gram-negative bacteriawas determined as described in example 2, with the adhered bacteria having been removed from the fabric samples by treatment in a vortex. The quantitative determination of the removed bacteria was accomplished by staining with Syto9 and fluorescence measurement (microtiter plate-Syto9 assay). Normal saline solution was used as a sterile control. The experiments were repeated twice independently of one another.

(37) The results in relation to the coating on PES (polyester) fabrics are shown in table 1 below.

(38) TABLE-US-00001 TABLE 1 Results relating to the reduction in bacterial adhesion to polyester fabric samples Reduction in adhered Silane bacteria [%] No. derivative S S. aureus P. aeruginosa 1 S1 34 41 2 S2 85 64 3 S3 55 48 4 S4 58 57 5 S5 46 17

(39) The reduction in the adhesion of the two microorganisms was calculated according to the formula given under 2.5. It was shown that polyester fabrics can be successfully coated with the hydrophilic silane derivatives S1 to S5 described, and that these coated fabrics exhibit an up to 85% reduced adhesion of bacteria relative to the uncoated fabrics.

(40) 3.2 Investigation of the Wash Stability of the Antiadhesive Coating

(41) Polyester fabric samples were coated with the hydrophilic silane derivatives S2, S3 and S5, as described in example 1, by the application in each case of a 10 wt % strength solution of the silane derivative, as described in example 1, to polyester fabric samples by a padding method.

(42) Fabrics were investigated in each case with coating concentrations of 0.1 wt %; 0.01 wt % and 0.001 wt % of hydrophilic silane derivative, based on the weight of the coated textile material.

(43) The fabric samples were investigated for the wash stability of the antiadhesive effect of the silane coating. The antiadhesive effect was determined by means of the Syto9-microtiter plate assay described in example 3, in a 96-well microtiter plate. Here, separately in each case, the adhesion of the two strains S. aureus and P. aeruginosa to the various fabric samples was assessed.

(44) The antiadhesive effect was determined in each case on fabric samples with the following pretreatments (A), (B) and (C): (A) on an unwashed fabric sample; (B) on a fabric sample washed twice at 30? C. only with water, without addition of a detergent; (C) on a fabric sample washed once at 30? C. in accordance with laundering standard EN ISO 6330, method 8A, with addition of an ECE B detergent.

(45) For each combination, two independent experiments were conducted in each case, in order to obtain information on the reliability of the results.

(46) The results are summarized in tables 2 (testing with respect to S. aureus) and 3 (testing with respect to P. aeruginosa) below. The reduction in the adhesion of the two microorganisms is indicated in each case in %, based on the adhesion to uncoated fabric samples.

(47) The wash stability results are also shown in graph form in FIGS. 1 and 2. FIG. 1 shows the results of table 2 for the wash stability of the antiadhesive effect (reduction in adhered bacteria in %) with respect to S. aureus in relation to a silane derivative coating on polyester fabric samples. FIG. 2 shows the results of table 3 for the wash stability of the antiadhesive effect (reduction in adhered bacteria in %) with respect to P. aeruginosa in relation to a silane derivative coating on polyester fabric samples.

(48) It was found that the maximum reduction in bacterial adhesion of about 40% to 60% is retained under the laundering conditions for all samples investigated. It was shown that the antiadhesive coating of the invention has a high wash stability.

(49) TABLE-US-00002 TABLE 2 Wash stability of the antiadhesive effect with respect to S. aureus, polyester fabric samples, tested using the Syto9 assay Coating Reduction in Silane concentration Wash adhered bacteria No. derivative [%] pretreatment [%] 1 S2 0.1 (A) 55 2 (B) 48 3 (C) 49 4 0.01 (A) 71 5 (B) 31 6 (C) 66 7 0.001 (A) 30 8 (B) 52 9 (C) 10 S3 0.1 (A) 47 11 (B) 46 12 (C) 61 13 0.01 (A) 63 14 (B) 34 15 (C) 58 16 0.001 (A) 57 17 (B) 54 18 (C) 69 19 S5 0.1 (A) 72 20 (B) 68 21 (C) 38 22 0.01 (A) 44 23 (B) 22 24 (C) 53 25 0.001 (A) 69 26 (B) 59 27 (C) 75

(50) TABLE-US-00003 TABLE 3 Wash stability of the antiadhesive effect with respect to P. aeruginosa, polyester fabric samples, tested using the Syto9-microtiter plate assay Coating Reduction in Silane concentration Wash adhered bacteria No. derivative [%] pretreatment [%] 1 S2 0.1 (A) 68 2 (B) 45 3 (C) 75 4 0.01 (A) 79 5 (B) 36 6 (C) 75 7 0.001 (A) 62 8 (B) 87 9 (C) 55 10 S3 0.1 (A) 85 11 (B) 36 12 (C) 76 13 0.01 (A) 65 14 (B) 37 15 (C) 71 16 0.001 (A) 63 17 (B) 46 18 (C) 69 19 S5 0.1 (A) 68 20 (B) 69 21 (C) 67 22 0.01 (A) 78 23 (B) 54 24 (C) 73 25 0.001 (A) 81 26 (B) 42 27 (C) 77
3.3 Investigation of the Antimicrobial Effect of the Coated Fabrics

(51) The antimicrobial activity of the coated fabric samples was investigated, in a determination of polyester fabric samples, each coated with a silane derivative S1 to S5, with the aid of the ISO-standardized method as per JIS L 1902, with respect to Staphylococcus aureus.

(52) The procedure here is that the fabric sample was inoculated with a defined amount of a microbial suspension (inoculum). Test specimens with a weight of approximately 0.4 g were investigated in a triplicate determination.

(53) The inoculated fabric sample was incubated in a closed system at 37? C. over a period of 18 hours. Following incubation, the bacteria of a defined amount of a dilution solution were recorded. The difference in the bacterial count of the fabric sample at 0 hours in comparison to the fabric sample after 18 hours served as a basis for evaluation. The antimicrobial activity is reported as a logarithmic or percentage value. Here, a reduction in the microbe count of 0% corresponds to inadequate antimicrobial action, a microbe reduction in the range from 0.1 to less than 90% to an inadequate antibacterial action, and a microbe reduction of greater than 90% to a good antibacterial action.

(54) The results relating to the antimicrobial action of the coated fabrics are summarized in table 4 below.

(55) It was found that the coated polyester fabrics exhibit as good as no antimicrobial activity with respect to Staphylococcus aureus, with values below log 1 being rated as no effect.

(56) TABLE-US-00004 TABLE 4 Antimicrobial activity on polyester fabric samples Coating Antimicrobial activity[log] concentration Washed once at Silane [%, based on Washed twice 30? C., without derivative fabric] Unwashed with water detergent untreated ?0.5 ?0.1 ?0.5 S2 0.1 ?0.2 0.00 ?0.4 0.01 ?0.4 0.1 ?0.6 0.001 0.2 0.1 ?0.1 S3 0.1 0.0 0.3 ?0.4 0.01 ?0.1 0.8 ?0.1 0.001 ?0.5 ?0.3 ?0.8 S5 0.1 ?0.5 ?0.4 ?0.6 0.01 ?0.3 ?0.2 ?0.6 0.001 0.5 0.9 ?0.3

EXAMPLE 4

Investigations on the Adhesion of Microorganisms to a Glass Surface

(57) 4.1 Production of the Coated Glass Samples

(58) Silane derivatives S1, S3, S4 and S5 as identified above in example 1 were used to produce coatings on glass slides. As a control (comparison sample) K, an uncoated glass slide cleaned with isopropanol was used.

(59) For the coating of the slides they were immersed for 60 seconds into a 0.1% strength solution of the corresponding silane derivative in ethanol/water as solvent with a water fraction of 5%. The solutions had been adjusted with acetic acid beforehand to a pH in the range from 4 to 5. The wetted slides were subsequently dried at 160? C. for 1 hour.

(60) 4.2 Determination of the Bacterial Adhesion Via Fluorescence Microscopy

(61) The slides wetted with the bacterial suspension were analyzed by microscope to determine the adhering bacteria. For this purpose, the test culture itself was admixed with a fluorescent dye, which labels the adhering bacteria and hence labels them with unambiguous identifiability on the sample surface. The fluorescent dye used was DAPI (4,6-diamidine-2-phenylindole), which binds to DNA and fluoresces under UV excitation. In order to determine the adhesion characteristics, the cell counts per cm.sup.2 were ascertained in 30 measuring windows, and the adhesion pattern was evaluated. Cell attachment was evaluated on an Olympus IX 51 using the Labflow AnalySIS image processing program.

(62) Bacterial suspensions produced and used were suspensions of test cultures of the strains Staphylococcus aureus and Escherichia coli. The concentration of the bacterial suspension was 10.sup.9 microbes/ml.

(63) The results of these measurements are summarized in table 5 below.

(64) TABLE-US-00005 TABLE 5 Results of microscopic evaluation - cell counts ascertained per cm.sup.2 Reduction in cell count Cell count [1/cm.sup.2] relative to control [%] Silane derivative S. aureus E. coli S. aureus E. coli S1 110 000 296 000 76 63 S3 77 000 233 000 83 71 S4 383 000 389 000 17 51 S5 219 000 306 000 52 61 K (control) 460 000 791 000

(65) All samples show much less of an adhesion by bacteria in comparison to the glass control, with both general and species-specific trends being discernible.

(66) In the case of adhesion experiments with S. aureus it is noted that there is a wide scatter of the results. For instance, with sample S4, only 16% reduction in adhesion relative to the control is ascertained, whereas the sample S3 shows a reduction of 83%. Very good results were achieved in this experiment by specimens S1 and S3. In the case of microscopic inspection, the coated surfaces S4, like the other specimens, showed only a few grapelike assemblies of S. aureus, which represents the typical cell morphology of the Staphylococci. The control, in contrast, in part showed a congregation of the cells to form very large assemblies, which were not observed on the coated specimens.

(67) The cell adhesions in the case of E. coli were comparatively close to one another for all of the samples and gave a reduction in cell count by at least 50 percent relative to the control K (uncoated glass slide). Microscope inspection showed that in the case of the adhesion of E. coli there was predominantly adhesion of individual cells, with stringlike assemblies being observed sporadically.

(68) In both series of tests, very good results were achievable in particular for the glass surfaces coated with silane derivatives S3 and S1.