Marker composition

Abstract

Marker composition comprising water, 1-10 wt.% non-ionic surfactant selected from alkyl polyglucosides, alcohol ethoxylates and alcohol ethoxylate propoxylates, or mixtures thereof, 1-5% organic solve

Description

FIELD OF THE INVENTION The present invention relates to a marker composition for marking a medical device or a surface, for example as part of a decontamination procedure or for establishing the efficacy of such a procedure, and to a carrier composition to which a dyestuff can be added to form such a marker composition. BACKGROUND TO THE INVENTION Within the healthcare market, decontamination procedures are widely used for disinfection and cleaning. Areas of particular importance include the reprocessing of medical devices, such as example surgical instruments, ultrasound probes, endoscopes and the like. For infection control and patient safety, it is essential that any process used for decontamination or disinfection is effective in practice, taking into account the products used for disinfection, the training and performance of the user, environmental factors, and so on. Existing methods for reprocessing such medical devices typically include multiple process steps. For example, a first step may be performed in which the device is cleaned with a cleaning agent, for the removal of gross contaminants and soiling from the surface. In a second step, disinfection or sterilization may takes place using chemical, thermal, or radiative means. In a third step, a rinsing process may be performed to remove left over chemical residue, particularly where the disinfection step uses a chemical disinfectant. One example of a three-step decontamination system, in which a chlorine dioxide-based disinfecting agent is used, is described in WO 2005 / 107823 A1. Many other disinfectant compositions are also used in the art, including those based on chlorine, peracetic acid, hydrogen peroxide, hypochlorite, quaternary ammonium compounds, tertiary amines and so on. Disinfection may also be achieved for example by exposure to UV radiation, steam or heat. The minimum requirement for device reprocessing is to disinfect the device. Cleaning and / or rinsing stages may be required depending on the type of device, type of disinfection medium, levels of contamination / soiling, and prevailing regulatory and legislative frameworks. Similar considerations apply to the decontamination and disinfection of work surfaces. Effective disinfection relies on the user ensuring that all parts of the surface to be treated are adequately exposed to the disinfecting agent. UK Patent Application Publication No. GB 2618158 A discloses a composition containing a dyestuff that exhibits a distinctive colour change upon exposure to the relevant disinfecting agent and can be applied to a medical device or a work surface before performing a disinfection operation. The choice of dyestuff for use in such compositions is influenced by several considerations. It is preferable that the colour of the composition when applied to the medical device is clearly distinguishable from the device to be disinfected, and is sufficiently strong to make it clear to the user where the composition has or has not been applied. For clinical environments, it may be desirable to use naturally-derived dyestuffs without negative safety indications, such as those used in the food and cosmetics industries. However, such naturally-derived dyestuffs are often less strong in colour than their synthetic counterparts, requiring high dyestuff loading to produce adequate colour. Furthermore, naturally-derived dyestuffs -particularly those which oxidise in the presence of a high-level disinfectant - may be susceptible to degradation when a composition containing the dyestuff is stored for a prolonged period and / or subjected to environmental changes. Such dyestuffs may also be sensitive to minor pH changes and degradation due to impurities, resulting in a detrimental effect on colour if a composition is contaminated during use. Against that background, it would be desirable to provide a marker composition for marking a medical device or a work surface that allows for high loading and good stability of a dyestuff, in particular a naturally-derived dyestuff. SUMMARY OF THE INVENTION Aspects of the invention are specified in the independent claims. Preferred features are specified in the dependent claims. In a first aspect, the invention provides a marker composition for application to a medical device or a surface. The marker composition comprises a carrier composition including water; from 1 wt% to 10 wt% nonionic surfactant selected from the group consisting of: alkyl polyglucosides, alcohol ethoxylates, alcohol ethoxylate propoxylates, and mixtures of two or more thereof; from 1 wt% to 5 wt% organic solvent selected from the group consisting of: glycol ethers, methoxymethyl butanol, propane-1,2-diol, isopropylideneglycerol and mixtures thereof; and from 0.01 wt% to 3 wt% of a neutral or anionic viscosity modifier. The marker composition further comprises a dyestuff. The quantity of dyestuff present is such that at least some of the dyestuff is present as a dispersed solid phase. For example, the marker composition may be a suspension or a colloid, in the form of a sol, with at least some of the dyestuff present as solid particles suspended in the carrier composition. Thus the carrier composition (plus any dissolved dyestuff) forms the liquid phase of the marker composition and is preferably an aqueous solution. Said another way, the carrier composition that forms the liquid phase may be an aqueous solution of the nondyestuff constituents of the marker composition, together with some dissolved dyestuff where the dyestuff is soluble. The combinations of nonionic surfactant, organic solvent and viscosity modifier used in the compositions described herein function well as a carrier for dyestuffs, in particular naturally-derived or protein-based dyestuffs. In particular, the carrier composition allows for a high loading of the dyestuff, beyond its solubility limit, with solid particles of dyestuff suspended in the marker composition to form a stable colloid. When the marker composition is spread on a surface, the solid particles of dyestuff are deposited on the surface. In this way, for a given dyestuff, a stronger colour depth can be achieved on the marked surface than would be the case with the same dyestuff in solution. This can allow the use of naturally-derived dyestuffs that would exhibit insufficient colour depth in solution only. Furthermore, it has been found that protein-based pigments in naturally-derived dyestuffs exhibit notable stability in the marker composition. This means that such dyestuffs can be used without significant degradation of the exhibited colour over a suitable shelf life (typically at least six months and up to one year or longer). In the context of this specification, the term “pigment” is used to refer to a substance that exhibits a colour resulting from selective colour absorption, which may be a single compound or two or more associated compounds (such as pigment-protein complexes). The term “dyestuff” is used to refer to a substance or mixture of substances that includes a pigment. A dyestuff may consist only of the pigment or may include a pigment together with one or more other substances (including additional pigments). Said another way, the dyestuff may comprise up to 100 wt% pigment. In some embodiments, the dyestuff comprises up to 10 wt% pigment, up to 20 wt% pigment, or up to 30 wt% pigment. The quantity of dyestuff present in the marker composition depends in part on the solubility of the dyestuff. Generally, the carrier composition may comprise at least 1 wt%, or at least 3 wt%, or at least 5 wt%, or from 6 wt% to 10 wt%, of the dyestuff. In the marker composition of the invention, the dyestuff comprises a protein-based pigment. For example, the dyestuff may comprise phycocyanin. In one embodiment, the dyestuff comprises spirulina extract, which includes the pigment phycocyanin. In that case, the marker composition may comprise at least 5 wt%, and more preferably from 6 wt% to 10 wt%, of the spirulina extract. Other suitable dyestuffs include anthocyanin, anthocyanidin and betanin dyestuffs. The dyestuff may exhibit a colour change upon exposure to a high-level disinfectant composition. For example, the dyestuff (or the pigment) may be oxidised in the presence of chlorine dioxide so that the initial colour of the dyestuff changes colour (for example to colourless) upon exposure to a chlorine dioxidebased disinfecting agent. Alternatively, the colour change may arise from oxidation of the dyestuff when the disinfecting agent is a different agent, such as chlorine, peracetic acid, hydrogen peroxide, hypochlorite and so on. In further examples, a colour change may arise due to UV-induced or thermal degradation of the dyestuff when the disinfecting agent is UV light or high temperature, respectively. The nonionic surfactant helps the marker composition to wet the surface of medical devices, which are typically smooth and may be hydrophobic. Surfactants typically promote foaming, and in some applications, it is desirable that the marker composition is dispensed as a foam, since foams can be easily dispensed onto an applicator (such as a wipe) and spread onto a surface. However, it can be desirable to avoid excessive foaming on the surface to be marked, to avoid nonuniformity of colour or undesirable light-scattering effects. To that end, when tested using the Ross-Miles method, the nonionic surfactant preferably achieves an initial foam height of 70 mm or less, preferably 50 mm or less, and / or foam collapse of 10% or more, preferably 20% or more after 5 minutes. It has been found that a nonionic surfactant mixture comprising one or more alkyl polyglucosides and one or more alcohol ethoxylate propoxylates produces particularly good results, with a suitable balance between wetting and foaming abilities to achieve uniform coverage when applied to a surface. The carrier composition may comprise from 1 wt% to 5 wt% of the nonionic surfactant. The choice of organic solvent has been found to be important in stabilising dyestuffs, particularly those with protein-based pigments, and affects how the marker composition deposits on the surface. Particularly suitable solvents include 3-methoxy-3-methyl-1 -butanol and dipropylene glycol n-propyl ether. The carrier composition may comprise from 2 wt% to 4 wt% of the organic solvent. The pH of the carrier composition may be adjusted to suit the dyestuff selected. For example, the pH may be between 2 and 7. When the dyestuff is a spirulina extract, the pH is preferably between 5 and 6, and still more preferably between 5.5 and 6. Where the dyestuff is an anthocyanin, a pH range of between 2 and 4 has been found to be suitable. The carrier composition may comprise a pH modifier (i.e. an acid or base added to adjust the pH to a target value). The pH modifier is preferably selected from the group consisting of: citric acid, sodium hydroxide, sodium carbonate and mixtures thereof. The presence of a viscosity modifier (which may also be referred to as a rheology modifier or thickening agent) is important in maintaining the dispersion of the solid phase in the composition. The viscosity modifier also has a positive effect on the spreading behaviour of the composition. It has been found that suitable viscosity modifiers are neutral or anionic. The viscosity modifier may be selected from the group consisting of natural polysaccharides, polysaccharide derivatives, xanthan gums, guar gums, hydroxyethyl cellulose, cellulose derivatives, polyacrylates and mixtures thereof. The marker composition preferably has a viscosity between 250 cP and 350 cP, measured using a Brookfield rotational viscometer with RV spindle 1 at 20 rpm. The carrier composition may further comprise a humectant, for example a triol (such as glycerine / glycerol) or a sugar-based humectant (such as a betaine, sorbitol, or trehalose). The carrier composition may comprise from 1 wt% to 5 wt%, and preferably from 1 wt% to 3 wt% of the humectant. The carrier composition may further comprise a sequestering agent. Sequestering agents are useful in protecting the pigments, by chelating impurities (particularly metal impurities) that may be introduced during manufacture of the composition or in use. The sequestering agent may for example be selected from the group consisting of: glutamic acid, N,N-diacetic acid, tetrasodium glutamate diacetate and mixtures thereof. The carrier composition may further comprise a preservative, such as a mixture of phenoxyethanol, butylbenzisothiazolone and bis(3-aminopropyl) dodecylamine, commercially available as parmetol BPX (RTM). The invention extends, in a second aspect, to an applicator wipe for applying a marker composition to a medical device or a surface, where the applicator wipe carries a marker composition according to the first aspect of the invention. The wipe preferably comprises a polypropylene substrate. It has been found that the marker composition remains stable (i.e. without degradation of the pigment) on such wipes for sufficiently long to provide an acceptable shelf life. Also disclosed is a carrier composition for a dyestuff, for example a dyestuff comprising a protein-based pigment, the carrier composition comprising water; from 1 wt% to 10 wt% nonionic surfactant selected from the group consisting of: alkyl polyglucosides, alcohol ethoxylates, alcohol ethoxylate propoxylates, and mixtures of two or more thereof; from 1 wt% to 5 wt% organic solvent selected from the group consisting of: glycol ethers, methoxymethyl butanol, propane-1,2-diol, isopropylideneglycerol, and mixtures thereof; and up to 3 wt% of a neutral or anionic viscosity modifier. A suitable dyestuff can be added to the carrier composition to provide a marker composition as described above. The carrier composition may be as described in the context of any embodiment of the marker composition of the first aspect of the invention. Also disclosed is a marker composition for application to a medical device or a surface, comprising a carrier composition including water, from 1 wt% to 10 wt% nonionic surfactant selected from the group consisting of: alkyl polyglucosides, alcohol ethoxylates, alcohol ethoxylate propoxylates, and mixtures of two or more thereof, from 1 wt% to 5 wt% organic solvent selected from the group consisting of: glycol ethers, methoxymethyl butanol, propane-1,2-diol, isopropylideneglycerol, and mixtures thereof, and up to 3 wt% of a neutral or anionic viscosity modifier. The marker composition further comprises at least 5 wt% spirulina extract as a dyestuff. Preferred and / or optional features of each aspect and embodiment of the invention may also be used, alone or in appropriate combination, in the other aspects and embodiments also. DESCRIPTION OF THE PREFERRED EMBODIMENTS In this specification, unless the context demands otherwise, the amount of a component in a composition is expressed as wt% (wt / wt% or weight / weight). This corresponds to the mass of each component relative to the total mass of the composition, expressed as a percentage. The present invention resides in a carrier composition to which a dyestuff can be added, and in a marker composition consisting of the carrier composition to which the dyestuff has been added. In the marker composition, the amount of dyestuff added exceeds the solubility limit of the dyestuff, so that at least some of the dyestuff remains as a solid (undissolved) phase, dispersed in the liquid phase. It will be understood that, in this specification, information (including composition and properties) provided in respect of the carrier composition can be applied equally to the marker composition and vice versa, except where the context demands otherwise. The carrier composition is an aqueous solution, comprising one or more nonionic surfactants, one or more organic solvents and one or more viscosity modifiers. Optionally, the carrier composition may also include one or more humectants, one or more sequestering agents, one or more preservatives, and / or one or more pH modifiers. The surfactant contributes to the ability of the marker composition to wet the surface of the medical device or the work surface. Good wetting ability is important, since medical device surfaces are often designed to resist wetting (i.e. they may have hydrophobic properties and a smooth texture). However, charged surfactants (i.e. anionic or cationic surfactants) and amphoterics were found in testing to have a detrimental effect on the stability of the dyestuff. For example, poloxamers and decylamine oxides were tested and found not to be suitable. Nonionic surfactants are therefore selected. It is desirable that the surfactants do not excessively foam. The foaming tendency of the or each surfactant may be tested using the Ross-Miles method. Suitable surfactants preferably achieve an initial foam height of 70 mm or less, preferably 50 mm or less, and / or foam collapse of 10% or more, preferably 20% or more after 5 minutes. Testing revealed that suitable nonionic surfactants are alkyl polyglucosides, alcohol ethoxylates, alcohol ethoxylate propoxylates, and mixtures of two or more thereof. Alcohol ethoxylate propoxylates with chain lengths of C6 to C15 with between 6 and 8 moles of ethoxylation and 4 moles of propoxylation may be particularly suitable. It has been determined that a blend of two commercially-available nonionic surfactants, namely AG 6210 (a blend of alkyl polyglucosides, in particular decyl glucoside and caprylyl glucoside and available from Nouryon) and Berol (RTM) 185 (alcohol ethoxylate propylate, available from Nouryon), provides the desired wetting properties without excessive foaming and without causing degradation of the dyestuff. As an alternative to AG 6210, a decyl glucoside (e.g. SugaDet D (RTM, Colonial Chemical)) may be used in this blend. Other suitable tested nonionic surfactants include Genapol EP 2424 and Genapol EP 2484 (RTMs, Clariant), and decyl glucoside. The carrier composition comprises from 1 wt% to 10 wt% of the nonionic surfactant (i.e. the total amount of nonionic surfactant, whether a single compound or a mixture of two or more compounds). Preferably, the carrier composition comprises from 1 wt% to 5 wt%, or from 2 wt% to 5 wt%, or from 2 wt% to 4 wt% of the nonionic surfactant. The solvent is a water-soluble organic solvent. It is desirable that the solvent is low toxicity, has a high flash point (to reduce flammability), is biodegradable and has a suitable evaporation rate to allow for spreading and even drying of the marker composition after application to the surface. Simple solvents such as ethanol and isopropyl alcohol are therefore not preferred for one or more of these reasons. Suitable tested solvents include glycol ethers such as dipropylene glycol n-propyl ether (available as Dowanol DPnP, Dow Chemicals), 3-methoxy-3-methyl-1-butanol, propane-1,2-diol and isopropylideneglycerol. More generally, the solvent may be a diol, particularly an isoprene diol or branched-chain dialcohol, or a ketal. The carrier composition comprises from 1 wt% to 5 wt% of the solvent. Preferably, the carrier composition comprises from 2 wt% to 4 wt% of the solvent. The viscosity modifier is provided to stabilise the dispersion of the dyestuff solid phase and to thicken the composition for optimum spreadability on the surface. It was found through testing that cationic viscosity modifiers had a negative effect on the stability of the dyestuff. Suitable tested viscosity modifiers include xanthan gum, hydroxyethyl cellulose, nonionic guar gums, and polyacrylates. The carrier composition preferably comprises from 0.01 wt% to 3 wt% of the viscosity modifier. Preferably, the carrier composition comprises from 0.1 wt% to 1 wt% of the viscosity modifier. The carrier composition may include a humectant to help disperse the viscosity modifier. It has also been found that humectants can help stabilise the dyestuff. Triols (in particular glycerol) or sugar-based humectants (such as sorbitol) are suitable. When present, the humectant may comprise from 0.5 wt% to 5 wt%, or from 1 wt% to 3 wt%, or from 1 wt% to 2 wt% of the composition. The carrier composition may include a sequestering agent or chelating agent. When present, a sequestering agent can chelate impurities, in particular heavy metals, which might otherwise cause degradation of protein-based pigments. A sequestering agent may therefore improve the shelf-life of the marker composition and increase tolerance to impurities introduced during manufacturing or in use. Suitable sequestering agents include tetrasodium glutamate diacetate (an aminopolycarboxylate-based chelating agent), available as Dissolvine (RTM) GL38 (Glutamic acid, N,N-diacetic acid, tetrasodium salt, Nouryon), trisodium ethylenediamine disuccinate, disodium EDTA and tetrasodium EDTA. The carrier composition may for example comprise from 0.01 wt% to 5 wt% of the sequestering agent. Preferably, the carrier composition comprises from 0.1 wt% to 1 wt% of the sequestering agent. The carrier composition may include a preservative, such as parmetol BPX (Vink Chemicals). The composition may include up to 2 wt%, and preferably from 0.1 wt% to 1.5 wt % of the preservative. The dyestuff to be added to the carrier composition to form the marker composition is most preferably a natural dyestuff. Examples of suitable dyestuffs may include anthocyanins, anthocyanidins and betanins. Preferably, however, the dyestuff is a blue spirulina extract, in which the colour is primarily derived from phycocyanin (a protein-based pigment). Commercially-available examples include Natpure Xfine Spirulina SL615 (RTM, Sensient Beauty) and Vegebrite Ultimate Spirulina (RTM, Naturex). It has been observed that adjusting the pH of the carrier composition to within a target range can optimise stability, colour depth and hue of the dyestuff. To this end, the composition may include a pH modifier, such as citric acid, sodium hydroxide and / or sodium carbonate. The behaviour of commercial dyestuffs with respect to pH is typically well-documented and a target pH range can be determined accordingly. For example, a pH range of from 4 to 7, preferably from 5 to 6, and most preferably from 5.5 to 6 has been found to be appropriate for dyestuffs based on blue spirulina extract. The amount of dyestuff to be added to the carrier composition to form the marker composition, in which at least some of the dyestuff is present as a dispersed solid phase at room temperature and pressure, depends on the solubility of the dyestuff. To determine an appropriate quantity, powdered dyestuff can be added incrementally to the carrier composition, with suitable mixing or stirring at room temperature and pressure. Initially (and assuming that the dyestuff has some water solubility) the dyestuff will predominantly dissolve. Once a solubility limit is reached, further dyestuff will remain in the solid phase and will become dispersed in the aqueous solution liquid phase. Thereafter, sufficient dyestuff can be added to achieve the desired colour depth. For example, the amount of dyestuff may be up to 0.5 wt%, up to 1 wt%, up to 2 wt%, up to 3 wt%, up to 4 wt%, up to 5 wt% higher than the observed solubility limit of a dyestuff. It is generally preferred to use the minimum amount of dyestuff that achieves the desired colour depth, and it has been found that the marker composition of the invention exhibits good colour depth at a lower dyestuff loading than other tested formulations. It has been found that, for the blue spirulina extract described above, the solubility limit in the carrier solution was between 4 wt% and 5 wt%, and adding about 3 wt% more dyestuff in excess of the solubility limit produced a stable marker solution with good colour depth. In this context, colour depth refers to the intensity of observed colour compared to a colourless composition. The total amount of dyestuff in the marker composition (including dissolved dyestuff and dispersed solid) may be at least 5 wt%. For example, the total amount of dyestuff may be from 5 wt% to 15 wt%, or from 5 wt% to 10 wt%. The marker composition may be produced in a single manufacturing process, in which the carrier composition is produced and then the dyestuff is immediately added. Alternatively, the carrier composition could be produced in a first manufacturing process, and stored and / or transported for use in a marker composition manufacturing process in which the dyestuff is added at a later date or different location. The marker composition may be supplied as a liquid composition in any suitable container or dispenser. For example, the marker composition may be supplied in a bottle, a foam dispenser, a spray bottle, a pump bottle and so on. Conveniently, the marker composition can be dispensed onto a suitable applicator, such as a wipe or sponge, for application to a medical device or a surface. Alternatively, the marker composition could be sprayed, poured or otherwise directly applied to the surface to be marked. In the case of a medical device, the device may be dipped into a vat of the marker composition. It is also possible for the marker composition to be pre-applied to an applicator wipe, for example a wipe with a polypropylene substrate. It has been found through testing that the marker composition remains stable when impregnated into or carried on such wipes. After application of the marker composition to the wipes, each wipe can be sealed in an individual sachet for storage. The invention will be further disclosed with reference to the following examples. Example 1 - carrier composition 1 L of a marker composition was prepared as follows. First, 15 g of glycerine (humectant) was mixed by hand with 2 g of xanthan gum (viscosity modifier) for a minimum of 15 minutes. The mixture was then added to 894.5 g of de-ionised water and the mixture was mixed by stirring the mixture with an overhead stirrer for a further 15 minutes to fully dissolve the glycerine and xanthan gum. Then, the following constituents were added: Sodium hydroxide pH modifier 1 g Glutamic acid, N,N-diacetic acid, tetrasodium salt (Dissolvine GL38) Sequestering 2.5 g agent 3-methoxy-3-methyl-1 -butanol Organic 30 g solvent Alkyl polyglucoside 65% (AG 6210, Nouryon) Nonionic 27.5 g surfactant Alcohol ethoxylate / propoxylate 90% (Berol 185, Nouryon) Nonionic 17.5 g surfactant phenoxyethanol, butylbenzisothiazolone and bis(3-am inopropyl)dodecylam ine (parmetol BPX, Vink Chemicals) Preservative 10 g The mixture was mixed for 30 minutes to dissolve all components. The pH of the resulting solution was tested and adjusted as required to a value of between pH 5 5 and pH 6 by addition of citric acid monohydrate or sodium carbonate. The result was a carrier composition with the following composition: Water 90.6 wt% Xanthan gum 0.2 wt% Glycerine 1.5 wt% Sodium hydroxide 0.1 wt% Glutamic acid, N,N-diacetic acid, tetrasodium salt (Dissolvine GL38) 0.25 wt% 3-methoxy-3-methyl-1 -butanol 3 wt% Alkyl polyglucoside (non-water component of AG 6210, Nouryon) 1.8 wt% Alcohol ethoxylate / propoxylate (non-water component of Berol 185, Nouryon) 1.6 wt% phenoxyethanol, butylbenzisothiazolone and bis(3-am inopropyl)dodecylam ine (parmetol BPX, Vink Chemicals) 1 wt% Example 2 - marker composition 5 85 g of a spirulina extract dyestuff (Natpure (RTM) Xfine Spirulina SL615, Sensient Beauty) was added to the carrier composition of Example 1 and mixed to distribute the dyestuff throughout the composition. After mixing, some of the dyestuff remained as a distributed solid phase. 10 The result was a marker composition with a strong blue colour and the following composition (with the wt% of each component expressed with respect to the mass of the final marker composition): Water 83.5 wt% Xanthan gum 0.18 wt% Glycerine 1.4 wt% Sodium hydroxide 0.09 wt% Glutamic acid, N,N-diacetic acid, tetrasodium salt (Dissolvine GL38) 0.23 wt% 3-methoxy-3-methyl-1 -butanol 2.7 wt% Alkyl polyglucoside (non-water component of AG 6210, Nouryon) 1.65 wt% Alcohol ethoxylate / propoxylate (non-water component of Berol 185, Nouryon) 1.45 wt% phenoxyethanol, butylbenzisothiazolone and bis(3-am inopropyl)dodecylam ine (parmetol BPX, Vink Chemicals) 0.9 wt% Spirulina extract (Natpure Xfine Spirulina SL615) 7.8 wt% The marker composition of Example 2 exhibited good stability in storage. 5 Example 3 - use of the marker composition The marker composition of Example 2 was applied by wipe to a transvaginal ultrasound probe. The probe was inspected and the coverage of the marker 10 composition was assessed. It was observed that, after wiping, a blue colour was visible on the probe over all wiped areas of the probe, with adequate uniformity. After application of the marker composition, the probe was subjected to a disinfection procedure using a two-part disinfectant system producing chlorine 15 dioxide as the active disinfectant (Tristel Duo (RTM)). The two parts of the Tristel Duo product were dispensed as foams onto a wipe and mixed by scrunching and folding the wipe in accordance with the product instructions. Upon application of the disinfectant-carrying wipe to the probe, the areas of the probe that were contacted by the disinfectant rapidly changed colour from blue to colourless. Further modifications and variations not explicitly described above can also be contemplated without departing from the scope of the invention as defined in the appended claims.

Claims

1. A marker composition for application to a medical device or a surface, comprising a carrier composition including:water;from 1 wt% to 10 wt% nonionic surfactant selected from the group consisting of: alkyl polyglucosides, alcohol ethoxylates, alcohol ethoxylate propoxylates, and mixtures of two or more thereof;from 1 wt% to 5 wt% organic solvent selected from the group consisting of: glycol ethers, methoxymethyl butanol, propane-1,2-diol, isopropylideneglycerol, and mixtures thereof; andfrom 0.01 wt% to 3 wt% of a neutral or anionic viscosity modifier;and a dyestuff, wherein the quantity of dyestuff present is such that at least some of the dyestuff is present as a dispersed solid phase;wherein the dyestuff comprises a protein-based pigment.

2. The marker composition of Claim 1, wherein the dyestuff comprises phycocyanin.

3. The marker composition of Claim 2, wherein the dyestuff comprises spirulina extract.

4. The marker composition of Claim 3, comprising at least 5 wt% of the spirulina extract.

5. The marker composition of Claim 4, comprising from 6 wt% to 10 wt% of the spirulina extract.

6. The marker composition of any preceding claim, wherein the nonionic surfactant is a mixture of one or more alkyl polyglucosides and one or more alcohol ethoxylate propoxylates.

7. The marker composition of any preceding claim, wherein the carrier composition comprises from 1 wt% to 5 wt% of the nonionic surfactant.

8. The marker composition of any preceding claim, wherein the organic solvent is 3-methoxy-3-methyl-1 -butanol.

9. The marker composition of any preceding claim, wherein the organic solvent comprises dipropylene glycol n-propyl ether.

10. The marker composition of any preceding claim, wherein the carrier composition comprises from 2 wt% to 4 wt% of the organic solvent.

11. The marker composition of Claim 2 or of any of Claims 3 to 10 when dependent on Claim 3, having a pH of between 4 and 7.

12. The marker composition of Claim 11, having a pH of between 5 and 6.

13. The marker composition of any preceding claim, wherein the carrier composition further comprises a pH modifier selected from the group consisting of: citric acid, sodium hydroxide, sodium carbonate, and mixtures thereof.

14. The marker composition of any preceding claim, wherein the viscosity modifier is selected from the group consisting of natural polysaccharides, polysaccharide derivatives, xanthan gums, guar gums, hydroxyethyl cellulose, cellulose derivatives, polyacrylates and mixtures thereof.

15. The marker composition of any preceding claim, wherein the viscosity of the marker composition is between 250 cP and 350 cP, measured using a Brookfield rotational viscometer using RV spindle 1 at 20 rpm.

16. The marker composition of any preceding claim, wherein the carrier composition further comprises a humectant selected from the group consisting of: triols, and sugar-based humectants.

17. The marker composition of any preceding claim, wherein the carrier composition further comprises a sequestering agent.

18. The marker composition of Claim 17, wherein the sequestering agent is selected from the group consisting of: glutamic acid, N,N-diacetic acid, tetrasodium glutamate diacetate and mixtures thereof.

19. The marker composition of any preceding claim, wherein the marker composition is a sol or a suspension.

20. An applicator wipe for applying a marker composition to a medical device or a surface, wherein the applicator wipe carries a marker composition according to any preceding claim.

21. The applicator wipe of Claim 20, wherein the wipe comprises a polypropylene substrate.

22. A carrier composition for a dyestuff, the carrier composition comprising: water;from 1 wt% to 10 wt% nonionic surfactant selected from the group consisting of: alkyl polyglucosides, alcohol ethoxylates, alcohol ethoxylate propoxylates, and mixtures of two or more thereof;from 1 wt% to 5 wt% organic solvent selected from the group consisting of: glycol ethers methoxymethyl butanol, propane-1,2-diol, isopropylideneglycerol,and mixtures thereof; and up to 3 wt% of a neutral or anionic viscosity modifier.