Colour changing compositions

Abstract

The present invention relates to compositions comprising a metal, a metal aggregation inhibitor, and a colour changing agent. The metal is bindable to the colour changing agent to provide a change in colour on binding and/or release thereof.

Claims

1. A composition comprising: a metal; a metal aggregation inhibitor; and a colour changing agent; wherein the metal is bindable to the colour changing agent to provide a change in colour on binding and/or release thereof, wherein the metal and colour changing agent are present at a molar ratio of about 1:1 to 20, and wherein the metal and aggregation inhibitor are present at a molar ratio of about 1:0.5 to 30.

2. The composition according to claim 1, wherein the metal and colour changing agent are present at a molar ratio of about 1:2 to 13.

3. The composition according to claim 1, wherein the metal and aggregation inhibitor are present at a molar ratio of about 1:0.5 to 7.

4. The composition according to claim 1, wherein the metal and aggregation inhibitor are present at a molar ratio of about 1:5 to 25.

5. The composition according to claim 1, wherein the composition is sprayable, comprising a liquid vehicle.

6. The composition according to claim 5, wherein the liquid vehicle is present at a level of about 50 ml to 1,000 ml for about 0.1 g of the metal, metal aggregation inhibitor and colour changing agent components.

7. The composition according to claim 1, further comprising a surfactant.

8. The composition according to claim 7, wherein the metal and surfactant are present at a weight ratio of about 1:500 to 7,000.

9. The composition according to claim 7, wherein the surfactant is hexadecyl-trimethyl-ammonium bromide (HDTMA), a polysorbate, an aliphatic phenol ethoxylate, an aliphatic sulfobetaine, or an aliphatic trimethylammonium bromide.

10. The composition according to claim 1, wherein the metal is iron.

11. The composition according to claim 1, wherein the colour changing agent is a chromeazurol or a tannin.

12. The composition according to claim 1, wherein the colour changing agent is chromeazurol S (CAS).

13. The composition according to claim 1, wherein the aggregation inhibitor is an aliphatic-trimethyl-ammonium bromide.

14. The composition according to claim 1, wherein the aggregation inhibitor is hexadecyl-trimethyl-ammonium bromide (HDTMA).

15. A substrate comprising a substrate carrier having a composition therein, wherein the composition comprises: a metal; a metal aggregation inhibitor; and a colour changing agent; wherein the metal is bindable to the colour changing agent to provide a change in colour on binding and/or release thereof; and wherein the metal and aggregation inhibitor are present at a molar ratio of about 1:0.5 to 30.

16. The substrate according to claim 15, wherein the substrate carrier is a non-woven material.

17. The substrate according to claim 15, wherein the substrate carrier comprises cellulose, polyester, lignin, protein, acrylic, nylon, aramid, polyurethane, alginate and/or mixtures thereof.

18. The substrate according to claim 15, wherein the substrate carrier comprises cellulose, polyester, lignin and/or mixtures thereof.

19. The substrate according to claim 15, wherein the substrate carrier comprises pulp, wool, silk, jute, linen, ramie, sisal, bagasse, banana, hemp, flax, camel hair, kenaf and/or mixtures thereof.

20. The substrate according to claim 15, wherein the substrate is absorbent.

21. The substrate according to claim 15, wherein the substrate is a wipe, a paper towel; or a tissue.

22. The substrate according to claim 15, wherein the substrate is moistened.

23. The substrate according to claim 15, wherein the metal is iron.

24. The substrate according to claim 15, wherein the colour changing agent is a chromeazurol or a tannin.

25. The substrate according to claim 15, wherein the colour changing agent is chromeazurol S (CAS).

26. The substrate according to claim 15, wherein the aggregation inhibitor is an aliphatic-trimethyl-ammonium bromide.

27. The substrate according to claim 15, wherein the aggregation inhibitor is hexadecyl-trimethyl-ammonium bromide (HDTMA).

28. A sprayable composition comprising: a metal; a metal aggregation inhibitor; a colour changing agent; a surfactant; and a liquid vehicle; wherein the metal is bindable to the colour changing agent to provide a change in colour on binding and/or release thereof; wherein the metal and aggregation inhibitor are present at a molar ratio of about 1:0.5 to 30.

29. The sprayable composition according to claim 28, wherein the metal and aggregation inhibitor are present at a molar ratio of about 1:0.5 to 7.

30. The sprayable composition according to claim 28, wherein the metal and colour changing agent are present at a molar ratio of about 1:1 to 15.

31. The sprayable composition according to claim 28, wherein the metal and surfactant are present at a weight ratio of about 1:500 to 7,000.

32. The sprayable composition according to claim 28, wherein the surfactant is hexadecyl-trimethyl-ammonium bromide (HDTMA), a polysorbate, an aliphatic phenol ethoxylate, an aliphatic sulfobetaine, or an aliphatic trimethylammonium bromide.

33. The sprayable composition according to claim 28, wherein the surfactant is a polysorbate, an aliphatic phenol ethoxylate, an aliphatic sulfobetaine, or an aliphatic trimethylammonium bromide.

34. The sprayable composition according to claim 28, wherein the liquid vehicle is water.

Description

(1) The invention will now be further described, by way of example only, with reference to the accompanying examples and FIGURE, in which:

(2) FIG. 1 shows an emission spectrum for CAS at variable pH.

EXAMPLES

Example 1

(3) Stock solutions of compositions in accordance with the present invention were prepared by mixing the following solutions:

(4) Stock Solution A:

(5) 50 ml of a solution comprising 0.06 g CAS in 50 ml H.sub.2O; 9 ml of a solution comprising 0.0027 g hydrated FeCl.sub.3 (FeCl.sub.3.6H.sub.2O) in 10 ml 10 mM HCl; 8 ml of a solution comprising 0.0146 g HDTMA in 8 ml H.sub.2O; and 33 ml of a solution comprising 2 g Tween® 80 in 33 ml H.sub.2O
Stock Solution B: 50 ml of a solution comprising 0.06 g CAS in 50 ml H.sub.2O; 9 ml of a solution comprising 0.0081 g hydrated FeCl.sub.3 (FeCl.sub.3.6H.sub.2O) in 10 ml 10 mM HCl; 8 ml of a solution comprising 0.0146 g HDTMA in 8 ml H.sub.2O; and 33 ml of a solution comprising 2 g Tween® 80 in 33 ml H.sub.2O

(6) 10 ml of each stock solution were diluted with 90 ml water to provide compositions for use as a cleaning spray.

(7) 10 ml of each stock solution were diluted with 10 ml of water to provide compositions for use in a label. Compositions may be added to the label by mixing with the carrier (e.g. agar) at a temperature of about 40° C.

Example 2

(8) A range of tests were performed to investigate the colouring effect of increasing molar ratio of iron relative to CAS S (hydrated FeCl.sub.3 (FeCl.sub.3.6H.sub.2O) to CAS S). The results were as follows: 1:0.0099 [1000×]—Blue 1:0.099 [100×]—Blue 1:0.485 [50×]—Blue 1:0.99 [10×]—Blue 1:9.9 [1×]—Pale Blue 1:19.8 [0.5×]—Red 1:99 [0.1×]—Red 1:198 [0.05×]—Red

(9) A deep blue colour was obtained with a ratio of 1:3.3.

Example 3

(10) Stock solution B was diluted by a factor of two to yield a solution for visibility testing. The solution was then made to the following dilutions, with the resulting qualitative visibility: 1×—dark blue, very little changes to orange seen with bacteria 2×—dark blue, still hard to see changes to orange with bacteria 5×—dark to medium blue, adding bacteria you can visibly see a grey and orange 10×—medium blue, mixing with bacteria shows a transparent orange colour 20×—near transparent blue, difficult to see orange colour because of high transparency 50×—almost completely clear with a hint blue

(11) Testing was performed in a 50 ml falcon tube with each dilution at a volume of 10 ml. 1 ml of OD 1 Bacteria (E-coli BL21 (DE3) cells and grown to an optical density of 1 as determined using UV-VIS) in water was added to each dilution to a final volume of 11 ml. The dilutions were placed at a volume of 1 ml on white weighing boats.

Example 4

(12) Membrane testing was performed with 10 kDa MWCO dialysis tubing. Dialysis tubing was cut to 10 cm in length to form a cylinder of tubing open and both ends. After tying one end of the dialysis tubing, the formulation was added to 5 ml total volume and then the second end was tied off to prevent any leaking of the formulation from the ends of the tubing.

(13) The membrane with the formulation was put into milk at room temperature for 24 hours. The results were compared with adding 5 ml total volume directly to the milk and also compared relative to a control which comprised of the membrane filled with 5 ml of water. No observable colour change occurred in the milk when the membrane was used. The formulation inside the membrane did change colour from blue to orange indicating that detection of siderophores was still possible.

Example 5

(14) An exemplary composition suitable for inclusion in a substrate, such as a surface wipe, is given below.

(15) TABLE-US-00001 Weight (g) Molar mass Moles Chromeazurol S 0.03 605.28 4.96E−04 Iron(III) chloride hexahydrate 0.00135 270.3 4.99E−05 (1-hexadecyl)trimethylammonium 0.0365 364.45 1.00E−03 bromide

(16) 0.0008475 g of the composition was mixed with 12.25 mL water and then doped into a 10×10 cm cellulose wipe.

Example 6

(17) An experiment was conducted to demonstrate the effect of pH on the colour of compositions in accordance with the present invention. A series of compositions having pH between 0.8 and 12.8 were prepared in accordance with the following procedure.

(18) Preparatory solutions with a pH between 0.8 and 6.8 were prepared from a stock solution comprising hydrochloric acid (1 mL, 37%) in distilled water (50 mL) and then diluted with sufficient further distilled water to yield solutions having a pH level 0.3 units lower than that intended for the final compositions for testing (e.g. where the final composition for testing was intended to have a pH of 1.8, then the preparatory solution was prepared by diluting the stock solution with further distilled water to a pH of 1.5).

(19) Preparatory solutions with a pH between 7.8 and 12.8 were prepared from a stock solution comprising sodium hydroxide (0.4 g) in distilled water (50 mL) and then diluted with further distilled water to yield solutions having a pH level 0.3 units higher than that intended for the final compositions for testing.

(20) Preparatory solutions were then diluted 1:1 (volume) with a water-mixed composition prepared in accordance with Example 5, to yield final compositions for testing having the desired pH.

(21) The (unbuffered) final compositions for testing were observed to have colouring as set out in the table below.

(22) TABLE-US-00002 pH Colour 0.8 Red 1.8 Blue 2.8 Blue 3.8 Blue 4.8 Blue 5.8 Blue 6.8 Blue 7.8 Blue 8.8 Blue 9.8 Blue 10.8 Orange 11.8 Yellow 12.8 Green

(23) A light absorbance study was conducted (Nanodrop 2000 Spectrophotometer, 0.1 mm path length) on the final compositions for testing to determine absorbance of CAS at 458 nm (λ.sub.max absorption for CAS S) at variable pH between 1 and 13. The results are shown in FIG. 1.