MICROENCAPSULATION PROCESS

The present invention relates to a method for microencapsulating a cargo, which cargo is preferably a hydrophilic antimicrobial composition. Also encompassed by the present invention is a microcapsule containing a cargo, which cargo is preferably a hydrophilic antimicrobial composition, as well as a method of preventing contamination of a surface with microbes by using microcapsules containing a hydrophilic antimicrobial composition.

Background of the invention

A recent development in the field of antimicrobial compositions are compositions comprising one or more silicon-containing quaternary ammonium compound with optionally one or more silicon-free quaternary ammonium compounds. Such compositions are of particular interest because it is possible to tailor the composition to a specific species of bacterium or virus by selecting different combinations of silicon-containing quaternary ammonium compounds and silicon-free quaternary ammonium compounds, and thus increase the efficacy of the composition against that species.

By contrast, earlier antimicrobial compositions only have a limited efficacy, and this efficacy is only present over a limited range of microbes. Further advantages of the new quaternary ammonium compositions include that they are not deactivated by anionic soaps or surfactants and that the efficacy of the compositions can be tailored to different temperatures, dependent upon environmental needs.

One disadvantage, though, is that these compositions are only active for a limited period of time after application to a surface. This is a particular issue for paper products and nonwoven materials, because the composition becomes active as soon as the surface is dry.

This means that the composition has a very limited activity time on such materials. There is therefore a need to provide an improved ‘window of activity’ for these compositions.

Summary of the invention To solve the problem, the inventors have devised a new method for microencapsulation, which method enables compositions comprising at least one silicon-containing quaternary ammonium compound with optionally one or more silicon-free quaternary ammonium compounds to be microencapsulated.

This was a difficult task because, although various microencapsulation methods are known in the art, none are believed to be suitable for microencapsulating hydrophilic antimicrobial compositions, as hydrophilic antimicrobial compositions are specifically designed to rupture cell walls/membranes: the very mechanisms which make the compositions so effective against a broad range of microbes also make them very effective at rupturing capsule walls.

Furthermore, the vast majority of known microencapsulation methods have certain aspects that make them inconvenient, such as the need for time and energy consuming ultrasonication steps. Additionally, many of these methods are undesirable from safety and environmental perspectives, because they involve the use of harmful chemicals such as formaldehyde or rely on polymerisation which contributes to e.g. microplastic pollution of our oceans.

Thus, following extensive formulation development work, the inventors have surprisingly found that the problem of microencapsulating hydrophilic antimicrobial compositions - and, in particular, quaternary ammonium compositions - may be solved using a water-oil- water (WOW)-complex coacervation encapsulation method that additionally involves subjecting the outer capsule wall of the microcapsule to a crosslinking reaction to strengthen it. The method of the present invention is thus distinguished over known methods, inter alia, by (a) the use of a combination of WOW interactions and complex coacervation to microencapsulate antimicrobial compositions, and (b) the inclusion of a subsequent crosslinking step to strengthen the outer capsule wall.

By utilising the technique of microencapsulation, the present invention provides a new delivery mechanism for hydrophilic antimicrobial compositions that provides point-of- contact delivery. In doing so, the present invention improves the antimicrobial activity of such compositions by extending the period of time after application in which the compositions retain disinfectant capability.

The present invention provides the following aspects:

[1] A method for microencapsulating a cargo, comprising:

(a) dispersing the cargo and optionally a first stabiliser in a first aqueous solution to obtain a first composition,

(b) combining the first composition obtained in step (a) with an oil phase and optionally a second stabiliser to obtain a second composition, or

(a’) dispersing the cargo and optionally a second stabiliser in an oil phase to obtain a first composition,

(b’) combining the first composition obtained in step (a’) with a first aqueous solution and optionally a first stabiliser,

(c) combining the second composition obtained in step (b) or (b’) with a second aqueous solution to obtain a third composition, which second aqueous solution contains a first polymer, and then optionally adding a second polymer to the third composition,

(d) inducing coacervation in the composition obtained in step (c), and

(e) crosslinking the first and optionally second polymers in the composition obtained in step (d).

[2] The method according to [1], wherein the cargo is a hydrophilic antimicrobial composition, preferably comprising one or more quaternary ammonium compounds, more preferably comprising one or more silicon-containing quaternary ammonium compounds and/or one or more silicon-free quaternary ammonium compounds, more preferably comprising one or more silicon-containing quaternary ammonium compounds and one or more silicon-free quaternary ammonium compounds. [3] The method according to [1] or [2], wherein the cargo is a hydrophilic antimicrobial composition comprising two or more quaternary ammonium compounds selected from those of formula (1) below and optionally one or more quaternary ammonium compounds selected from those of formula (2) below: formula (1): R ¹ ₍ 4-x)-Si([-R ² -N ⁺ (H)i(R ³ )j][X“])x formula (2): [H _m -N ⁺ -R ⁴ _n ][Y“] wherein for each of formulae (1) and (2), R ¹ , R ² , R ³ , R ⁴ , i, X , Y and x are independently selected, and:

R ¹ is selected from the group consisting of alkoxy radicals, alkylether alkoxy radicals and alkyl radicals;

R ² is a divalent hydrocarbon radical; each of R ³ and R ⁴ is independently selected from the group consisting of benzyl, alkyl radicals, alkyl ether hydrocarbon radicals, hydroxyl-containing alkyl radicals, and nitrogen-containing hydrocarbon radicals; each of X~ and Y“ is independently selected from the group consisting of chloride, bromide, iodide, tosylate, hydroxide, sulfate, and phosphate; i = 0 to 2 and j = 1 to 3, provided that i + j = 3; m = 0 to 3 and n = 1 to 4, provided that m + n = 4; and x is 1 to 3.

[4] The method according to any one of the preceding aspects, wherein a first stabiliser is added in step (a) or (b’), which first stabiliser is preferably a sugar.

[5] The method according to any one of the preceding aspects, wherein a second stabiliser is added in step (b) or (a’), which second stabiliser is preferably an emulsifier. [6] The method according to any one of the preceding aspects, wherein the first aqueous solution comprises at least 90% v/v water, preferably at least 95% v/v water and more preferably at least 99.0% v/v water, such as at least 99.9% v/v water.

[7] The method according to any one of the preceding aspects, wherein the oil phase comprises one or more oils, such as organic and/or mineral oils, and optionally one or more active ingredients, preferably wherein the oil phase comprises at least one mineral oil, such as white liquid paraffin, at least one active ingredient and optionally one or more essential oils, more preferably wherein the at least one active ingredient is a hydrophobic antimicrobial compound.

[8] The method according to any one of the preceding aspects, wherein the first polymer is negatively charged under acidic conditions, and is preferably a polysaccharide.

[9] The method according to any one of the preceding aspects, wherein the first polymer is carboxylmethyl cellulose, sodium carboxymethyl cellulose, agar, Arabic acid, ghatti gum, poly acrylic acid, polyoxyethylene, sterculia gum, starch, gum acacia, xanthan gum, sodium alginate, carrageenan, cellulose, chitin, pectin, polyuronic acids, or chitosan, and is preferably gum acacia.

[10] The method according to any one of the preceding aspects, wherein the second polymer is added in step (c), and wherein the second polymer is positively charged under acidic conditions, and is preferably a protein.

[11] The method according to any one of the preceding aspects, wherein the second polymer is added in step (c), and wherein the second polymer is gelatin, whey protein, pea protein, soya, zein, potato protein, rice protein or wheat protein, and is preferably gelatin. [12] The method according to any one of the preceding aspects, wherein coacervation in step (d) is induced by lowering the pH, and wherein once step (d) has been completed the pH of the resultant composition is from 0.1 to 6.9, preferably from 1.0 to 6.0, and more preferably 2.0 to 5.0.

[13] The method according to any one of the preceding aspects, wherein before step (e) is carried out the temperature of the composition obtained in step (d) is reduced to 20 °C or lower and the composition is then kept at this reduced temperature for at least 1 minute, preferably at least 10 minutes.

[14] The method according to any one of the preceding aspects, wherein the second polymer is added in step (c), and wherein the crosslinking in step (e) is between the first and second polymers, either with or without the involvement of a crosslinking agent.

[15] The method according to any one of the preceding aspects, wherein the crosslinking in step (e) involves the addition of one or more crosslinking agents.

[16] The method according to any one of the preceding aspects, wherein after step (e) at least one additional agent is added to the reaction mixture, preferably wherein the additional agents area dispersant such as xanthan gum and/or an emollient such as mono propylene glycol (MPG).

[17] The method according to any one of the preceding aspects, wherein the microcapsules obtained following completion of step (e) comprise an outer capsule wall, an oil phase and one or more inner capsules, wherein:

- the one or more inner capsules are situated radially inwards of the outer capsule wall, the oil phase is situated in between the one or more inner capsules and the outer capsule wall, each of the one or more inner capsules comprises an aqueous solution in which is dispersed a cargo, which cargo is as defined in any one of [1] to [3],

- the oil phase is as defined in [1] or [7], and

- the outer capsule wall comprises crosslinked first and optionally second polymers, which first polymers are as defined in any one of claims [1], [8] or [9], and which second polymers are as defined in any one of claims [1], [10] or [H].

[18] A formulation containing microcapsules obtainable by a method according to any one of the preceding aspects, which formulation is preferably an aqueous composition.

[19] A microcapsule obtainable by a method according to any one [1] to [17],

[20] A microcapsule comprising an outer capsule wall, an oil phase and one or more inner capsules, wherein:

- the one or more inner capsules are situated radially inwards of the outer capsule wall,

- the oil phase is situated in between the one or more inner capsules and the outer capsule wall, each of the one or more inner capsules comprises an aqueous solution in which is dispersed a cargo, which cargo is as defined in any one [1] to [3], the oil phase is as defined in [1] or [7], and - the outer capsule wall comprises crosslinked first and optionally second polymers, which first polymers are as defined in any one of [1], [8] or [9], and which second polymers are as defined in any one of [1], [10] or [11],

[21] The microcapsule according to [20], wherein the microcapsule is obtainable by a method as defined in any one of [1] to [17],

[22] A formulation containing microcapsules as defined in any one of [19] to [21],

[23] An article which has microcapsules as defined in any one of [19] to [21] attached to it.

[24] A material which has been treated with microcapsules or a formulation containing microcapsules, wherein said microcapsules are as defined in any one of [19] to [21] and said formulation containing microcapsules is as defined in [18] or [22],

[25] Use of microcapsules or a formulation containing microcapsules to prevent contamination of a surface of an article with microbes during use of said article, wherein said microcapsules are as defined in any one of [19] to [21] and said formulation containing microcapsules is as defined in [18] or [22],

Description of the figures

Figure 1 depicts a polynuclear microcapsule (1) comprising a plurality of inner capsules (4), which inner capsules are surrounded by an oil phase (3), which oil phase is itself surrounded by an outer capsule wall (2). The inner capsules (4) comprise an aqueous solution (5) in which is dispersed, typically dissolved, a cargo.

Figure 2 depicts a mononuclear microcapsule (1) comprising a single inner capsule (4), which inner capsule is surrounded by an oil phase (3), which oil phase is itself surrounded by an outer capsule wall (2). The inner capsules (4) comprise an aqueous solution (5) in which is dispersed, typically dissolved, a cargo. Detailed description of the invention

Definitions

Unless otherwise indicated, the terms used within this document shall have their ordinary meaning as understood by the person skilled in the art. However, as used in the present invention, the particular terms given below shall have the following definitions.

Cargo: any active ingredient, species, compound, reagent, composition, formulation, etc., that is/shall be encapsulated within the microcapsules of the invention. The nature of the cargo is not limited in any particular way, e.g. it may be a solid, liquid, solution, gel, foam or mousse. Preferably, the cargo is an antimicrobial composition.

Antimicrobial composition: any composition that has efficacy against one or more microbes in removing, inactivating, killing, reducing or destroying said microbes. This includes antibacterial, antifungal and antiviral compositions.

Microbe: any microscopic organism that may exist as a single cell or group of cells. Examples include bacteria, fungi and viruses.

Quaternary ammonium composition: any composition comprising one or more quaternary ammonium compounds. Preferably, the quaternary ammonium composition comprises at least one silicon-containing quaternary ammonium compound. More preferably, the quaternary ammonium composition comprises at least one silicon- containing quaternary ammonium compound with optionally one or more silicon-free quaternary ammonium compounds

Quaternary ammonium compound: any chemical containing a quaternary ammonium moiety. Preferably, the quaternary ammonium compound is selected from those of formulae (1) or (2) below: formula (1): R ¹ ₍ 4-x)-Si([-R ² -N ⁺ (H)i(R ³ )j][X“])x formula (2): [H _m -N ⁺ -R ⁴ _n ] [Y ] wherein for each of formulae (1) and (2), R ¹ , R ² , R ³ , R ⁴ , i, X“, Y“ and x are independently selected, and:

R ¹ is selected from the group consisting of alkoxy radicals, alkylether alkoxy radicals and alkyl radicals;

R ² is a divalent hydrocarbon radical; each of R ³ and R ⁴ is independently selected from the group consisting of benzyl, alkyl radicals, alkyl ether hydrocarbon radicals, hydroxyl-containing alkyl radicals, and nitrogen-containing hydrocarbon radicals; each of X~ and Y“ is independently selected from the group consisting of chloride, bromide, iodide, tosylate, hydroxide, sulfate, and phosphate; i = 0 to 2 and j = 1 to 3, provided that i + j = 3; m = 0 to 3 and n = 1 to 4, provided that m + n = 4; and x is 1 to 3.

Microencapsulation method

The present invention provides a method for microencapsulation of a cargo. More particularly, the method is directed to microencapsulation of a hydrophilic cargo, preferably a hydrophilic antimicrobial composition

Specifically, the present invention provides a method comprising the following steps:

(a) dispersing, preferably dissolving, the cargo and optionally a first stabiliser in a first aqueous solution to obtain a first composition,

(b) combining the first composition obtained in step (a) with an oil phase and optionally a second stabiliser to obtain a second composition, or (a’) dispersing the cargo and optionally a second stabiliser in an oil phase to obtain a first composition,

(b’) combining the first composition obtained in step (a’) with a first aqueous solution and optionally a first stabiliser,

(c) combining the second composition obtained in step (b) or (b’) with a second aqueous solution to obtain a third composition, which second aqueous solution contains a first polymer, and then optionally adding a second polymer to the third composition,

(d) inducing coacervation in the composition obtained in step (c), and

(e) crosslinking the first and optionally second polymers in the composition obtained in step (d).

Steps (a) and (b) are preferred over steps (a’) and (b’).

The invention relates to using a water-oil-water (WOW) emulsion system in conjunction with coacervation and crosslinking in order to microencapsulate a cargo within the inner capsule(s) of the microcapsules. The cargo is dispersed, preferably dissolved, within the inner capsule(s) of the microcapsules.

The cargo may be a solute or liquid substance, such as an antimicrobial composition or a fragrance/flavour compound. Preferably the cargo is hydrophilic and more preferably the cargo is a hydrophilic antimicrobial composition. Even more preferably, the cargo is a quaternary ammonium composition. In this regard, quaternary ammonium compounds are known as surface disinfectants on humans, animals and other surfaces with good antimicrobial properties but there is a need for a delivery mechanism that enables these compounds to remain active for longer periods or to be activated at point-of-use. The present inventors have surprisingly found that microencapsulation achieves this goal.

In steps (a) to (c) or (a’) to (c), a WOW emulsion is formed. In the WOW emulsion, the cargo is present at last in the inner water phase. Thus, it is preferred that, within the WOW emulsion, the cargo is contained (preferably dissolved) within a water inner capsule which is surrounded by an oil phase, which oil phase is itself surrounded by more water. The WOW emulsion may be formed by any conventional means.

In some circumstances it may be desirable to have more than one type of cargo within the microcapsules. This can be achieved by dispersing the cargoes together in step (a) or (a’). For example, the two cargoes can be dispersed together in a single a first aqueous solution in step (a). In that instance, each inner capsule in the resulting product will contain the two cargoes. Alternatively, it may be desirable to have to have only one type of cargo present in each inner capsule. This can be achieved, for example, by preparing two separate first aqueous solutions in step (a), each containing a different cargo. If these different first aqueous solutions are combined with the oil phase in step (b) separately, then the cargo in each resulting inner capsule will depend upon the first aqueous solution from which it originates.

In step (d), coacervation is used to from the outer capsule wall of the microcapsule of the invention. In this regard, “coacervation” as used herein refers to the separation of a composition containing one or more macromolecular compounds into two or more immiscible liquid phases.

Any type of coacervation can be used in the method of the invention, including simple and complex coacervation, and all types of coacervation are encompassed by the present invention. Simple coacervation refers to the use of a desolvation agent to achieve phase separation. Complex coacervation refers to the use of two desolvation agents of opposite charge to achieve phase separation. In the context of microcapsule, the phase separation leads to the formation of the outer capsule wall. For both techniques, the desolvation agents are macromolecules and are preferably polymers.

Coacervation may be induced by a variety of methods including: changing temperature, changing pH, adding one or more salts, adding one or more non-solvents, adding one or more incompatible polymers or inducing a polymer-polymer interaction in some other way. In the method of the invention, coacervation is preferably induced by changing pH. Preferably, the method of the invention uses complex coacervation rather than simple coacervation. Hence, the second polymer is preferably added in step (c).

The composition obtained after step (d) contains microcapsules (1) comprising an outer capsule wall (2), an oil phase (3) and one or more inner capsules (4), wherein:

- the one or more inner capsules (4) are situated radially inwards of the outer capsule wall (2),

- the oil phase (3) is situated in between the one or more inner capsules (4) and the outer capsule wall (2), each of the one or more inner capsules (4) comprises an aqueous solution (5) in which is dispersed a cargo, which cargo is as defined herein,

- the oil phase (3) is as defined herein, and

- the outer capsule wall (2) comprises first and optionally second polymers, which first and second polymers are as defined herein.

The inner capsules (4) may contain more than one cargo and/or different cargoes may be present in each capsule. The oil phase (3) may further comprise one or more hydrophobic antimicrobial compounds.

Subsequently, in step (e), the polymers in the outer capsule wall (2) are crosslinked.

Between steps (d) and (e) a cooling step optionally takes place. Preferably, the cooling step does take place. In this regard, before step (e) is carried out the temperature of the composition obtained in step (d) is reduced to 20 °C or lower and the composition is then kept at this reduced temperature for at least 20 minutes. Preferably, the temperature of the composition obtained in step (d) is reduced to 20 °C or lower and more preferably 15 °C or lower. Thus, it is particularly preferred that the composition obtained in step (d) is cooled to around 10 °C. Preferably, the composition obtained in step (d) is kept at the reduced temperature between 1 minute and more preferably at least 10 minutes. Preferably, the composition obtained in step (d) is kept at the reduced temperature for no more than 120 minutes, more preferably no more than 60 minutes. Thus, it is particularly preferred that the composition obtained in step (d) is kept at the reduced temperature for 1 to 120 minutes, more preferably from 10 to 60 minutes for example for around 30 minutes.

The cooling step typically allows the outer capsule wall to harden. In particular, if the second polymer is added and is gelatin (which is especially preferred), the cooling step allows the natural gelation properties of gelatin to harden the outer capsule wall.

In step (e), a crosslinking reaction is initiated to further strengthen the outer capsule wall. The crosslinking may be achieved by any conventional means.

After completing of step (e), the microcapsules of the invention are fully formed and are contained within a formulation that is preferably an aqueous solution. The microcapsules consist of a cargo contained within a water inner capsule which is surrounded by an oil phase, which oil phase is itself surrounded by an outer capsule wall.

Further steps after step (e) may also be employed in the method of the present invention. For instance, one or more additional agents may be added.

Once obtained, the formulation containing the microcapsules of the invention may optionally be worked up to extract the microcapsules. Alternatively, the microcapsules may be left in the formulation.

The formulation and/or microcapsules may then be used to provide controlled release of the cargo contained within the microcapsules over an extended period of time, as well as providing point-of-use delivery of the cargo. This may be achieved by applying the formulation and/or microcapsules to a surface or material by any conventional means and then optionally allowing the surface or material to dry. This may constitute the final steps in the formation of a product or, alternatively, the surface or material may then be further processed to form a downstream product, e.g. as would be the case for facial tissues. The first and second aqueous solutions have important roles in the WOW interactions which result in the formation of the inner capsule and the second aqueous solution also has an important role in the coacervation interactions which result in the formation of the outer capsule wall.

Preferably, the first and second aqueous solutions are water, although they may comprise other reagents such as dyes, fragrances or further active ingredients. The first and second aqueous solutions, independently, preferably comprise at least 90% w/w water, more preferably at least 95% w/w, more preferably at least 99.0% w/w and even more preferably at least 99.9% w/w.

The first and second aqueous solutions together make up the majority of the composition obtained in step (e). Thus, they preferably account for at least 51% w/w of the composition obtained in step (e), more preferably at least 60% w/w and even more preferably at least 70% w/w.

The oil phase also has an important role in the WOW interactions which result in the formation of the inner capsule. Accordingly, the presence of more hydrophobic oils in the oil phase as opposed to less hydrophobic oils is preferred. The oil phase may comprise a single oil, such as a pure mineral oil or an organic oil. The preferred oil in this regard is white liquid paraffin. Typically, though, an oil containing a fragrance (e.g. essential oils such as eucalyptus oil) and/or an oil containing a colour (e.g. an oil-based dye) is also added to the oil phase, meaning that the oil phase is a mixture of two or more oils. Fragrances are preferably of natural origin, such as plant essential oils, e.g. lavender, eucalyptus, tea tree, menthol, camphor. Dyes are preferably pigmented oils or dyes of natural origin such as those sourced from plant roots, berries, bark and leaves.

Preferably, the oil phase is a mixture of a pure mineral oil and one or more essential oils. More preferably, the oil phase is a mixture of white liquid paraffin and one or more essential oils such as eucalyptus. The oil phase may also contain one or more other reagents, such as further active ingredients. For instance, the oil phase may be imbued with further antimicrobial properties by inclusion of one or more antimicrobial active ingredients. Thus, the present invention also provides a method for microencapsulating materials such as hydrophobic materials, which materials are contained within the oil phase of the microcapsules of the invention.

When present in the oil phase, the one or more other reagents are preferably hydrophobic. A hydrophobic reagent is typically one which has a hydrophilic-lypophilic balance (HLB) value of less than 10. Preferably, the one or more other reagents are active ingredients, such as antimicrobial active ingredients. Thus, the other reagents are preferably hydrophobic antimicrobial active ingredients. Preferred examples of hydrophobic antimicrobial ingredients include hydrophobic acids, terpenes and diols. More preferably, the hydrophobic antimicrobial ingredients are salicylic acid and/or p-menthane diol.

Alternatively, the one or more other reagents may comprise an amphiphilic antimicrobial compound. When used, such compounds will be present in the oil phase and/or may adopt a micellar position on the interface between the inner capsule and the oil phase.

The amount of oil phase in the composition obtained in step (e) is preferably from 2 to 49% w/w, more preferably 5 to 35% w/w, even more preferably 10 to 25% w/w. Thus, it is particularly preferred that the amount of oil phase in the composition obtained in step (e) is around 11% w/w.

In the method of the invention, first and second stabilisers are optionally added in steps (a) and (b) or (a’) and (b’) respectively. When added, these stabilisers facilitate the microencapsulation process. More specifically, the first stabiliser is used in step (a) to stabilise the cargo in the first aqueous solution and the second stabiliser is used to stabilise the water-in-oil emulsion that is formed in step (b). Preferably, the first and second stabilisers are both added in steps (a) and (b) respectively. Similar considerations apply when steps (a’) and (b’) are used. The first and second stabilisers may be, independently, any conventional stabiliser, including sugars, emulsifiers, surfactants and so on. Preferably, the first stabiliser is a sugar such as glucose, maltose, dextrose and sucrose. More preferably, the first stabiliser is sucrose. Preferably, the second stabiliser is an emulsifier, more preferably a water-in-oil emulsifier, even more preferably a water-in-oil emulsifier having a hydrophilic-lypophilic balance (HLB) value of between 2 and 7, more preferably between 3 and 6. Preferred examples of second stabilisers include lecithin, polyglycerol polyricinoleate (PGPR) or ammonium phosphatide. Preferably, the second stabiliser is PGPR.

Preferably, neither of the first or second stabilisers is non-ionic surfactant such as Tween 80 (Fisher Scientific, New Jersey, USA).

If present, the concentration of the first stabiliser in the composition obtained in step (e) is preferably from 0.01 to 5.00% w/w, more preferably from 0.05 to 2.00% w/w and even more preferably from 0.07 to 0.50% w/w. Thus, when the first stabiliser is present (which is preferred), it is particularly preferred that the concentration of the first stabiliser is around 0.10% w/w.

If present, the concentration of the second stabiliser in the composition obtained in step (e) is preferably from 0.10 to 5.00% w/w, more preferably from 0.30 to 3.00% w/w and even more preferably from 0.50 to 2.00% w/w. Thus, when the second stabiliser is present (which is preferred), it is particularly preferred that the concentration of the second stabiliser is around 0.80% w/w.

In the method of the invention, first and optionally second polymers are added in step (c) to enable coacervation to be used to form the outer capsule wall. This may be simple or complex coacervation. Preferably, both first and second polymers are added. Preferably, the coacervation is complex coacervation.

Addition of the first and optionally second polymers also allows for the subsequent crosslinking in step (e), which strengthens the outer capsule wall. The first and/or second polymer may conveniently also be an emulsifier, and thus also stabilise the WOW emulsion. However, this is not a necessary requirement and one or more separate emulsifiers may instead be added.

The first polymer is preferably negatively charged under acidic conditions and the second polymer, if added (which is preferred), is preferably positively charged under acidic conditions. However, the first and second polymer may be of a different charge under non-acidic conditions. For instance, when added (which is preferred), the second polymer is preferably an amphoteric polymer under neutral conditions that becomes positively charged under acidic conditions.

The first polymer may be synthetic or natural. Preferred synthetic polymers include PVA, polyurethane, polysiloxane and any carbon-based polymers comprising alcohol functional groups, e.g. polyvinyl alcohol. Preferred natural polymers include polysaccharides and proteins. Natural polymers are preferred.

It is particularly preferred that the first polymer is a polysaccharide. Thus, the first polymer is preferably a polysaccharide that is negatively charged under acidic conditions. Suitable examples include carboxylmethyl cellulose, sodium carboxymethyl cellulose, agar, Arabic acid, ghatti gum, poly acrylic acid, polyoxyethylene, sterculia gum, starch, gum acacia, xanthan gum, sodium alginate, carrageenan, cellulose, chitin, pectin, polyuronic acids and chitosan. Preferably, the first polymer is gum acacia.

The second polymer, if added (which is preferred), is preferably a protein. Thus, the second polymer is preferably a protein that is positively charged under acidic conditions and, as mentioned above, is preferably amphoteric under neutral conditions. Suitable examples include gelatin, whey protein, pea protein, soya, zein, potato protein, rice protein, wheat protein and any other amphoteric proteins. Preferably, the second polymer is gelatin or pea protein. More preferably, the second polymer is gelatin. In this regard, there are two main types of gelatin: gelatin obtained through acid hydrolysis of porcine skin/bone (Type A) and gelatin obtained through alkaline hydrolysis of bovine skin/bone (Type B). Both are suitable for use in the present invention and both are preferred. However, Type A gelatin is particularly preferred.

The concentration of the first polymer in the composition obtained in step (e) is preferably from 0.10 to 5.00% w/w, more preferably from 0.30 to 3.00% w/w and even more preferably from 0.50 to 2.00% w/w. Thus, it is particularly preferred that the concentration of the first polymer is around 0.80% w/w.

When added (which is preferred), the concentration of the second polymer in the composition obtained in step (e) is preferably from 0.10 to 5.00% w/w, more preferably from 0.30 to 3.00% w/w and even more preferably from 0.50 to 2.00% w/w. Thus, it is particularly preferred that the concentration of the second polymer is around 0.80% w/w.

In step (d), coacervation is induced. This is preferably done by reducing the pH of the composition obtained in step (c) to an acidic level. Thus, it is preferred that once step (d) has been completed, the pH of the resultant composition is from 0.1 to 6.9, more preferably from 1.0 to 6.0, more preferably from 2.0 to 5.0 and even more preferably from 3.0 to 5.0. It is particularly preferred that the pH is lowered to around 4.8.

The pH may be lowered by any conventional means, such as addition of any suitable acid. In this regard, suitable acids include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, citric acid, phosphoric acid and so on. Preferably, hydrochloric and and/or citric acid is used. More preferably, citric acid is used.

In step (e), a crosslinking reaction is carried out. The crosslinking may be achieved by any conventional means - such as by heat, pressure, change in pH or irradiation - with or without the use of one or more crosslinking agents. The crosslinking reaction may join individual molecules of the first polymer or, if a second polymer is added (which is preferable), the crosslinking reaction may also join (i) the first and second polymers and (ii) individual molecules of the second polymer. The linkage between the polymers may be direct - i.e. polymer-polymer linkage - or may include a crosslinking agent - i.e. polymer-crosslinking agent-polymer linkage. Preferably, crosslinking is achieved by adding one or more crosslinking agents. More preferably, crosslinking is achieved by adding one or more crosslinking agents and then raising the reaction pH. There is no particular limitation to the nature of crosslinking agents that may be used. For instance, crosslinking agents may utilise one or more of the following interactions: covalent bonds (in particular peptide or ester bonds), ionic bonds and electrostatic interactions. The crosslinking agents preferably contain at least one of the following functional groups: carbonyl, amine, alcohol and metal ion. Metal ions are preferably alkali metal ions or alkali earth metal ions such as Na ⁺ , K ⁺ , Mg ²⁺ and Ca ²⁺ . Preferably, the metal ion is an alkali earth metal ion such as Ca ²⁺ .

Exemplary groups of crosslinking agents include aldehydes, ketones, carboxylic acids, amines, amides, esters, alkali metal salts and alkali earth metal salts.

Exemplary crosslinking agents include adipic acid, adipic acid dihydrazide, formaldehyde, acetaldehyde, glyoxal, 1,5-pentanedial, maleic acid, oxalic acid, dimethylurea, poly(acrolein), diisocyanate, di vinyl sulfonate, sodium chloride and calcium chloride. Preferably, the crosslinking agent is 1,5-pentanedial, adipic acid and/or adipic acid dihydrazide. In this regard, adipic acid and adipic acid dihydrazide are particularly preferred as they are less toxic than other crosslinking agents, such as formaldehyde. More preferably, the crosslinking agent is 1,5-pentanedial.

When added, which is preferred, the crosslinking agent is added in an appropriate amount to achieve the desired degree of crosslinking in step (e). To this end, the skilled person can easily determine an appropriate dosing level.

Preferably, the crosslinking involves formation of one or more of the following interactions: peptide bond between carbonyl and amine functional groups, peptide bond between carboxyl and amine functional groups, ester bonds between carbonyl and alcohol functional groups, ester bonds between carboxyl and alcohol functional groups and ionic bonds involving Ca ²⁺ ions e.g. from calcium chloride. These interactions may be first polymer-first polymer interactions, first polymer-crosslinking agent interactions, first polymer-second polymer interactions, second polymer-crosslinking agent interactions and/or second polymer-second polymer interactions.

Preferably, the second polymer is added in step (d) and the crosslinking interactions are peptide and/or ester bonds.

During step (e), the pH is preferably raised. In this regard, the pH is preferably raised to at least 5.0, more preferably at least 6.0, and even more preferably at least 7.0. Preferably the pH is raised to no higher than 10.0, more preferably no higher than 9.0 and even more preferably no higher than 8.0. Thus, it is particularly preferred that the pH is raised to around 7.3. The pH can be raised by adding a base, such as a sodium hydroxide.

Where the first polymer is a negatively charged polysaccharide, the second polymer is an amphoteric protein and a crosslinking agent is used (as is preferred), the crosslinking step results in covalent bonds forming between the amine functional groups of the second polymer and the crosslinking agent. Covalent bonds between the alcohol functional groups of the first polymer and the crosslinking agent may also form, in addition to the ionic interactions that attract the first polymer to the second polymer. These covalent bonds strengthen the outer capsule wall of the microcapsules.

In addition to crosslinking agents, one or more catalysts may optionally be used in the crosslinking step. Suitable examples include sodium hypophosite, dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids.

In the method of the invention described above, it is particularly preferred that a second polymer is added in step (c) and that the crosslinking in step (e) is achieved. The skilled person can easily identify appropriate crosslinking reagents and reaction conditions to achieve crosslinking. For example, crosslinking can be achieved by changing the reaction pH to from around 6.5 to around 7.5, then adding 1,5-pentanedial, for example in two parts (typically half at the start and half after about one hour. Furthermore, in the method of the invention described above, it is especially preferred that the cargo is a hydrophilic antimicrobial composition comprising at least one silicon- containing quaternary ammonium compound and optionally one or more silicon-free quaternary ammonium compounds, the first polymer is gum acacia, the second polymer is added in step (c) and is gelatin, the pH is lowered in step (d) to induce complex coacervation between the first and second polymers, a crosslinking agent is added in step (e) and is 1,5-pentanedial, and xanthan gum is added as a dispersant after step (e).

In the method of the invention, the microcapsules (1) obtained following completion of step (e) comprise an outer capsule wall (2), an oil phase (3) and one or more inner capsules (4). More specifically:

- the one or more inner capsules (4) are situated radially inwards of the outer capsule wall (2),

- the oil phase (3) is situated in between the one or more inner capsules (4) and the outer capsule wall (2), each of the one or more inner capsules (4) comprises an aqueous solution (5) in which is dispersed a cargo, which cargo is as defined herein,

- the oil phase (3) is as defined herein, and

- the outer capsule wall (2) comprises crosslinked first and optionally second polymers, which first and second polymers are as defined herein.

The inner capsules (4) may contain more than one cargo and/or different cargoes may be present in each capsule. The oil phase may further comprise one or more hydrophobic antimicrobial compounds.

Cargo The method of the present invention may be used to microencapsulate a very broad range of cargoes - such as drugs, proteins, polymers, antimicrobials, aroma/flavour compounds, fragrances, minerals, nutrients, herbicides, pesticides and so on - provided that they are hydrophilic and/or water soluble. A hydrophilic cargo is typically one which has a hydrophilic-lypophilic balance (HLB) value of greater than 10.

Preferably, the cargo is an antimicrobial composition. Examples of antimicrobial compositions include disinfectants, antiseptics and antibiotics.

Preferably, the cargo is a hydrophilic antimicrobial composition. Suitable compounds for inclusion in such hydrophilic antimicrobial compositions are discussed further below.

More preferably, the cargo is a quaternary ammonium composition. More preferably, the cargo is a hydrophilic antimicrobial composition comprising at least one silicon-containing quaternary ammonium compound and/or at least one silicon-free quaternary ammonium compound, more preferably at least one silicon-containing quaternary ammonium compound and optionally one or more silicon-free quaternary ammonium compounds. More preferably, the cargo is a hydrophilic antimicrobial composition comprising at least two quaternary ammonium compounds selected from those of formula (1) below and optionally one or more quaternary ammonium compounds selected from those of formula (2) below: formula (1): R ¹ ₍₄ -x)-Si([-R ² -N ⁺ (H)i(R ³ ) _j ][X-]) _x formul a (2) : [H _m -N ⁺ -R ⁴ _n ] [ Y“] wherein for each of formulae (1) and (2), R ¹ , R ² , R ³ , R ⁴ , i, X“, Y“ and x are independently selected, and:

R ¹ is an alkoxy, alkylether alkoxy or alkyl group;

R ² is an alkylene group; each of R ³ and R ⁴ is independently a benzyl, alkyl, alkyl ether hydrocarbon, hydroxyalkyl, or nitrogen-containing hydrocarbon group; each of X- and Y“ is independently a halide, tosylate, hydroxide, sulfate, or phosphate; i = 0 to 2 and j = 1 to 3, provided that i + j = 3; m = 0 to 3 and n = 1 to 4, provided that m + n = 4; and x is 1 to 3.

As used herein, an “alkyl” group or moiety is typically a C1.20 alkyl, preferably a C1.12 alkyl, more preferably a Ci-6 alkyl and most preferably a C1.3 alkyl. Particularly preferred alkyl groups and moieties include, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl and hexyl.

As used herein, an alkylene group is an alkyl group as defined above which is divalent.

As used herein, an alkoxy group is an alkyl group as defined above which is attached to an oxygen atom. The alkoxy group is typically a C1.20 alkoxy group, preferably a C1.12 alkoxy group, more preferably a Ci-6 alkoxy group and most preferably a C1.3 alkoxy group. Particularly preferred alkoxy groups include, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, pentoxy and hexoxy.

As used herein, an alkyl ether hydrocarbon group is an alkyl group as defined above connected to another alkyl group as defined above via an oxygen atom. The alkyl ether hydrocarbon group is typically a C1.20 alkyl ether hydrocarbon group, preferably a C1.12 alkyl ether hydrocarbon group, more preferably a Ci-6 alkyl ether hydrocarbon group. Particularly preferred alkyl ether hydrocarbon groups include, for example, dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, isopropyl ethyl ether and tertbutyl propyl ether.

As used herein, an alkylether alkoxy group is an alkoxy group as defined above which is attached to an alkyl ether hydrocarbon group as defined above. A typical alkylether alkoxy group is butoxy ethyl ether. As used herein, a hydroxyalkyl group is typically an alkyl group as defined above substituted by one or more hydroxy groups, preferably 1, 2 or 3 hydroxy groups, more preferably 1 hydroxy group.

As used herein, a nitrogen-containing alkyl group is typically an alkyl group as defined above containing one or more nitrogen atoms, preferably 1, 2 or 3 nitrogen atoms.

As used herein, a halide group is typically chloride, fluoride, bromide or iodide and is preferably chloride, bromide or iodide.

Compositions comprising at least two quaternary ammonium compounds selected from those of formula (1) and optionally one or more quaternary ammonium compounds selected from those of formula (2) are better antimicrobial agents than conventional quaternary ammonium compounds: they have a wider kill range and are active under wider environmental conditions. However, it is believed that the superior cell wall-destroying ability of these compositions also disrupts/destroys capsule walls of microcapsules, so it is particularly difficult to encapsulate these compositions. Surprisingly, though, the method of the present invention can successfully microencapsulate these compositions.

Exemplary quaternary ammonium compounds include:

3-(trimethoxysilyl) propyl dimethyl octadecyl ammonium chloride, alkyl silyl dimethyl benzyl ammonium chloride, dioctyl silyl dimethyl ammonium bromide, quaternary ammonium compounds, benzyl-C 12- 18-alkyl dimethyl, salts with 1,2- benzisothiazol-3(2H)-one 1, 1-dioxide, benzalkonium chloride, didecyldimethylammonium chloride, and dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride. Preferably, the cargo is a hydrophilic antimicrobial composition comprising one or more of 3-(trimethoxysilyl) propyl dimethyl octadecyl ammonium chloride, alkyl silyl dimethyl benzyl ammonium chloride and dioctyl silyl dimethyl ammonium bromide. Thus, preferably the cargo comprises 3 -(trimethoxy silyl) propyl dimethyl octadecyl ammonium chloride. More preferably, the cargo comprises 3-(trimethoxysilyl) propyl dimethyl octadecyl ammonium chloride and alkyl silyl dimethyl benzyl ammonium chloride. Even more preferably, the cargo comprises 3-(trimethoxysilyl) propyl dimethyl octadecyl ammonium chloride, alkyl silyl dimethyl benzyl ammonium chloride and dioctyl silyl dimethyl ammonium bromide.

The concentration of the cargo in the composition obtained in step (e) is preferably from 0.01 to 25.00% r w, more preferably from 0.10 to 15.00% v/v, more preferably from 0.20 to 10.00% w/w and even more preferably from 0.30 to 5.00% w/w. Thus, the concentration of the cargo in the composition obtained in step (e) may be 0.20% w/w, 0.40% w/w, 0.50% w/w, 1.00% w/w, 1.25% w/w, 3.00% w/w, 5.00% w/w or 10.00% w/w.

Alternatively, the cargo may comprise an amphiphilic antimicrobial compound. When present in the cargo, such compounds will be present in the inner capsule and/or may adopt a micellar position on the interface between the inner capsule and the oil phase.

Preferably, the cargo is not an anthocyanin, such as a black raspberry anthocyanin.

Antimicrobial compounds

As discussed herein, antimicrobial compounds may be present in the cargo (i.e. dispersed within the inner capsule), in which case hydrophilic compounds are used. Antimicrobial compounds may also be present in the oil phase, in which case hydrophobic compounds are used. In addition, there are amphiphilic antimicrobial compounds, which may be present in the inner capsule or the oil phase, or may adopt a micellar position on the interface between the inner capsule and the oil phase. Antimicrobial compounds are well known to those of skill in the art (see, for example, J Surfactants Deterg. 2019 Sep; 22(5): 1119-1127, Falk). A skilled person can readily identify whether a given antimicrobial compounds is hydrophilic, hydrophobic or amphiphilic, and can thus determine how best it can be used in conjunction with the present invention. A non-exhaustive list of antimicrobial compounds is provided below.

• Alcohols, such as Ethanol, Benzyl alcohol, Isopropanol

• Aldehydes, such as Glutaraldehyde and formaldehyde

• Anionic surfactants such as Sodium dodecyl sulphate, sodium dodecyl benzene sulphonate, linear alkyl benzene sulphonate and sodium lauryl sulphate

• Amphiphiles, such as Didecyldimethylammonium chloride, alkyldimethylethylbenzylammonium chloride and Benzalkonium chloride

• Amphoterics such as; amine oxides and betaines,

• Azole derivatives, such as Enilconazole, Miconazole, Tebuconazole,

• Biguanides such as, Chlorohexidine, alexidine and polymeric biguanides

• Carbamates such as, Bendiocarb, Carbendazum, Carbofuran

• Diamidines, Propamidine and Dibromopropamidine

• Halogens such as Chlorine, Iodine,

• Halophenols; Chloroxyenol

• Neonicotinoids Imidacloprid, Sulphfoxaflor

• Peroxygens such as Hydrogen peroxide, ozone and paracetic acid

• Phenol, bisphenol and derivatives such as; m-Cresol, Hexachlorophene, Pentachlorophenol and Triclosan and Biphenol 2- ol

• Quinolones such as Ciprofloxacin

• Heavy metal derivatives such as Copper and silver

• Organic Acids, such as Lactic acid, Butylparaben, P-Hydroxylbenzoic acid ester, salycilic acid

• Organophosphates, Chloramidophos, DCPE

• Pyrethroids Allethrin and Cypermethrin,

• Terpenes such as Limonine, Cinnamaldehyde, Eugenol, Terpenen-4-ol, P- Menthane diol • Plant derived antimicrobials such as; Alkaloids, Phenolics, Terpenoids, Lectins, Polypeptides, Polyacetylenes.

• Quaternary ammonium compounds: o 1 ^st Generation: benzalkomium with (C12-C18) alkyl chains, o 2 ^nd Generation: aromatic rings with hydrogen and chlorine, methyl and ethyl groups o 3 ^rd Generation: dual quaternary ammonium compounds (QAC) mixture of alkyl dimethyl benzyl ammonium chloride. o 4 ^th Generation: dialkylmethyl aminos with twin chains. o 5 ^th Generations: combinations of dual QACs o 6 ^th Generation: polymeric QAC o 7 ^th Generation: bis-QAC with polymeric QAC

Microcapsules and formulation containing microcapsules

The product directly obtained following step (e) of the method of the invention is a formulation comprising microcapsules of the invention. Specifically, the formulation is an aqueous solution comprising the microcapsules of the invention. Conveniently, this formulation may itself be subsequently applied to downstream articles, with or without an initial step of concentrating the formulation (e.g. by filtration, sedimentation or centrifugation). Alternatively, the formulation may be worked up by any conventional means to isolate the microcapsules per se. For example, the microcapsules can be isolated by evaporation / air-drying of the aqueous solution within which they are contained, or by freeze-drying or spray drying. The dried microcapsules can then either be used in that form, or re-suspended in another medium.

The formulation is at least 50 % w/w water, preferably at least 60 % w/w, more preferably at least 70 % w/w. This allows the formulation to quickly evaporate from any article it is applied to upon drying, leaving the microcapsules behind. The first and second aqueous solutions together make up the majority of the composition obtained in step (e). As well as containing the microcapsules of the invention, the formulation may advantageously contain one or more additional agents.

The microcapsules (1) of the invention may be mononuclear or polynuclear. In this context, mononuclear refers to a microcapsule (1) having one inner capsule (4) within a single outer capsule (2), and polynuclear refers to a microcapsule (1) having more than one inner capsule (4) within a single outer capsule (2). Preferably, the microcapsules are polynuclear.

The structure of the dry polynuclear microcapsules (1) is as follows: two or more inner capsules (4), each consisting of an aqueous solution (5) comprising the cargo and optionally one or more stabilisers, are surrounded by an oil phase (3), which oil phase comprises one or more lipophilic compounds. The oil phase is itself surrounded by an outer capsule wall (2), which outer capsule wall comprises crosslinked polymers.

For dry mononuclear microcapsules (1), the same structure applies except that there is only one inner capsule (4) in the oil phase (3).

Preferably, the diameter of the microcapsules of the invention is less than 350 pm, more preferably less than 100 pm and even more preferably less than 50 pm.

Preferably, the diameter of the microcapsules of the invention is more than 500 nm, more preferably more than 750 nm and even more preferably more than 1000 nm.

Thus, it is particularly preferred that the diameter of the microcapsules is from 2 to 30 pm, more preferably 15 to 20 pm.

The diameter of the capsules can be determined by an appropriate technique, for example by observation under a microscope.

Additional agents The formulation containing microcapsules of the invention may comprise one or more additional agents. In other words, one or more additional agents may be added to the composition obtained in step (e) of the method of the invention after completion of step (e).

Illustrative functions of the additional agents include: dispersing the microcapsules uniformly within the composition, indicating rupture of capsules/release of cargo and preventing contamination of the formulation comprising the microcapsules. The function will vary depending on the final application of the microcapsules. For instance, if the microcapsules are destined to be applied to medical personal protective equipment, one or more antimicrobial agents may be added to the composition obtained in step (e) to prevent contamination of the formulation.

When added, the additional agents are added in an appropriate amount to achieve their desired effects. To this end, the skilled person can easily determine an appropriate dosing level.

Preferred additional agents include fragrances, dyes, further antimicrobial agents/active ingredients, dispersants, antifreeze agents and emollients, although other additional agents may also be added, such as viscosity modifiers. The further antimicrobial agents may or may not be based on quaternary ammonium compounds. For agricultural applications, preferred additional agents include minerals, nutrients, herbicides and pesticides.

Preferably, a dispersant and/or an emollient are added. Thus, it is particularly preferred that xanthan gum and mono propylene glycol (MPG) are added as additional agents. The xanthan gum acts as a dispersant and enables the microcapsule-containing formulation to retain a homogenous form, whilst the MPG acts as both an antifreeze agent and an emollient.

Release mechanism The microcapsule of the invention comprises a cargo. This cargo is protected by the microcapsule until such time that it is released from the microcapsule. In this way, the microcapsule of the invention provides an improved delivery system for the cargo, which delivery system allows a high degree of specificity for both time-of-release and location- of-release.

The cargo is released from the microcapsule of the invention by rupture. Rupture of the microcapsule may be achieved in a number of ways and is not particularly limited. For instance, the microcapsule can be ruptured by a change in the physical characteristics of the microcapsule and/or its surroundings (i.e. a physical mechanism), by a change in the mechanical characteristics of the microcapsule and/or its surroundings (i.e. a mechanical mechanism), or by a change in the chemical characteristics of the microcapsule and/or its surroundings (i.e. a chemical mechanism).

Examples of physical mechanisms include changes in temperature, changes in moisture level and exposure to UV. A change in temperature may be an increase or a decrease. Preferably, it is an increase. More preferably, it is an increase to high temperatures. Thus, if the microcapsule is ruptured by a change in temperature, then preferably this is done by heating the microcapsule and/or its surroundings to 50 °C to 120 °C, preferably 75 °C to 110 °C, more preferably 90 °C to 100 °C. A change in moisture level may be an increase or a decrease. Preferably, it is an increase. More preferably, it is an increase to high levels of humidity. Thus, if the microcapsule is ruptured by a change in moisture level, then preferably this is done by increasing the moisture level of the microcapsule and/or its surrounds to relative humidity values of from 50% to 100%, preferably from 60% to 100%, more preferably from 70% to 95%. As used here, relative humidity has its normal definition in the art, i.e. it is the ratio of the partial pressure of water vapour in the mixture to the equilibrium vapour pressure of water over a flat surface of pure water at a given temperature. The relative humidity can be determined by routine techniques known to those of skill in the art.

Alternatively, a change in moisture is measured by the amount of water added to a surface upon which the microcapsules have already been applied. Typically, to achieve mechanical rupture water may added to the microcapsules at a rate from 0.1 to 3.0 g/m ² , preferably from 0.5 to 2.0 g/m ² , more preferably from 0.8 to 1.5 g/m ² . Particularly preferably, water is added to the surface upon which the microcapsules have already been applied at a rate of 1.0 g/m ² .

Examples of mechanical mechanisms include shear release under mechanical pressure.

Examples of chemical mechanisms include ionic change and addition of chemical rupturing agents. Ionic change may be an increase or decrease in pH. This may be achieved by any routine means known in the art, for instance the addition of one or more bases to increase the pH and the addition of one or more acids to decrease the pH.

The release mechanism of the cargo from the microcapsule may be tailored to any desired application of the microcapsules of the invention. By way of example, in circumstances where the microcapsules are applied to a product and point-of-use release is desired, then it is advantageous to exploit a mechanical release mechanism, such as shear under mechanical pressure. Alternatively, when continuous release over an extended period of time is desired, then it is advantageous to exploit a physical release mechanism, such as a change in moisture level.

Preferably, the cargo is released by rupture of the microcapsule. More preferably, the cargo is released by physical or mechanical rupture of the microcapsule. Even more preferably, the cargo is released by shear under mechanical pressure, a change in moisture level or a change in temperature. It is often particularly preferable that the cargo is released by shear under mechanical pressure.

Uses

Formulations containing microcapsules prepared in accordance with the invention may be used to treat a surface or material. For instance, when the microcapsules contain one or more additional agents, the composition may be used to provide the surface or material with (e.g.) fragrance release at point-of-use. Furthermore, when the cargo contained within the microcapsules is a hydrophilic antimicrobial composition (which is preferred), the formulation can also be used to prevent a surface or material from becoming contaminated with microbes. This may be done with or without the presence of additional agents.

These effects are achieved by applying the formulation to the surface or material and then drying (e.g. by leaving for two hours to air-dry), resulting in the microcapsules being affixed to the surface or material. These microcapsules are stable and will remain intact on the surface or material for long periods of time, such as several months. However, these microcapsules are also readily sheared under mechanical pressure, such as the kind of pressures the surface or material would be subjected to during the course of normal use. Alternatively, the microcapsules may be ruptured under any of the other release mechanisms described above, such as moisture release or temperature release. Once ruptured, the microcapsules release the cargo contained therein (e.g. an antimicrobial composition and optionally one or more additional agents such as a fragrance). Hence, point-of-use delivery of the cargo is achieved.

Thus, the invention also provides an effective way to keep a surface or material substantially free of microbes for a significant period of time, such as several months. This involves first sterilising the surface or material by any conventional means, e.g. by UV irradiation, and then treating said surface or material with a formulation containing microcapsules containing an antimicrobial composition.

Exemplary surfaces or materials that may be treated include: plastics, woods, ceramics, stones, metals, papers, textiles, fabrics (including woven, knitted and non-woven fabrics) and skins (including human or animal skins, e.g. human hands).

Where the surface is skin, the formulation may be used directly or indirectly as a hand- sanitiser. For instance, the formulation may be directly applied to the hands, or mixed with further components (e.g. viscosity modifiers) to produce a hand-sanitising composition. Thus, the present invention provides a method of treating skin, preferably the skin on the hands of a human being, comprising applying to the skin a formulation comprising microcapsules obtained by the method of the present invention. This prevents the skin from becoming contaminated with microbes for an extended period of time.

The present invention also provides a formulation for use in a method of treatment of the skin, which formulation comprises microcapsules obtained by the method of the present invention, and which treatment involves applying the formulation to the skin. For instance, the formulation may be a hand-sanitiser or a hand cream that is applied to the skin. This prevents the skin from becoming contaminated with microbes for an extended period of time.

The present invention also provides the use of a formulation comprising microcapsules obtained by the method of the present invention for the manufacture of a medicament for the treatment of the skin, which treatment involves applying the formulation to the skin. This prevents the skin from becoming contaminated with microbes for an extended period of time.

Additionally, when a first treated surface or material comes into contact with a second untreated surface or material, the transfer of microcapsules from the first surface or material to the second occurs, thus providing the second surface or material with a lesser but notable degree of point-of-use delivery of the cargo. By way of example, if microcapsules containing an antimicrobial composition are applied to a hand towel and a person subsequently dries their hands with said towel, some microcapsules will be transferred to the person’s hands, helping to keep them free of microbes for an extended period.

The comments in this section of the description are directed to formulation containing microcapsules prepared in accordance with the invention. However, these comments apply mutatis mutandis to microcapsules per se which have been prepared in accordance with the invention. Downstream products/articles

Formulations containing microcapsules prepared in accordance with the invention may be applied to a broad range of products/articles, including the following:

Consumer paper disposables including facial tissues, toilet tissues, kitchen towels, hand towels, diapers, feminine care products, adult incontinence products and sanitary products;

Away from home products including face masks/coverings, couch roll, hand towels and non-woven textiles; and

- Medical/surgical products including surgical masks, bed sheets, warming blankets, mattress covering materials, gauze and other wound care materials, consultation table paper products, surgical gowns, patient gowns, pressure ulcer pads, IV therapy chair coverings, bed screens, bed curtains, masks, footware, footware products, footcare, door pads etc.

The formulation may be applied to the products/articles by any suitable conventional means, for instance via low pressure spray systems, padding or printing methods such as gravure, lithography and screen printing. Preferably, the formulations are applied via low pressure spray systems or padding. More preferably, the formulations are applied via low pressure spray systems.

The formulations may be applied to the products/articles at a concentration of 0.1 to 20 g/m ² , preferably 0.2 to 10 g/m ² , more preferably 0.4 to 6 g/m ² .

After the formulation has been applied to a product/article, the product/article is preferably dried. This may be done by any conventional means, such as heating, fans or natural (i.e. air) drying. Preferably, the product/article is air-dried.

After the formulation has been applied to a product/article, it is possible for further processing of said product/article to take place, without reducing the efficacy of the invention (i.e. without rupturing the microcapsules during processing). This may take place before or after the drying step. For example, the composition can be applied to tissue paper, the tissue paper allowed to dry, and then the tissue paper folded and packaged. Alternatively, the further processing may be used in place of the drying step.

Alternatively, the formulation may be applied to items (such as wet-wipes) which do not require drying. When used, such wet-wipes will result in a secondary application of the microcapsules to the surface or materials the wet-wipes are used to clean. More generally, articles coated with microcapsules in a primary application step may be capable of transferring those microcapsules to other articles in a secondary application step.

The comments in this section of the description are directed to formulations containing microcapsules prepared in accordance with the invention. However, these comments apply mutatis mutandis to microcapsules per se which have been prepared in accordance with the invention.

Examples

The following specific examples illustrate the invention in further detail.

Example 1 - Microencapsulation of hydrophilic antimicrobial composition

Using a commercially-available hydrophilic antimicrobial composition comprising silicon- containing quaternary ammonium and quaternary ammonium compounds as a cargo, a formulation containing microcapsules in accordance with the invention was prepared as follows:

Table 1 : exemplary amounts of reagents for use in method below.

1 = sucrose

2 = 50:50 mixture of white paraffin and essential oil.

3 = polyglycerol polyricinoleate (PGPR)

4 = gum acacia

5 = gelatin (Type A)

6 = citric acid

7 = 1,5-pentanedial

8 = xanthan gum

9 = mono propylene glycol (MPG)

Step 1 In a first reaction vessel, the cargo was combined with the water of the first aqueous solution, and to this first stabiliser was added. The components were dissolved by a combination of mixing and heating using a magnetic stirrer.

Step 2 The oil phase was added to the composition obtained in Step 1 while mixing at approximately 5400 rpm. The second stabiliser was then added.

Step 3 In a third reaction vessel, the first polymer was combined with the water for the second aqueous solution and mixed for 15 mins at 4200 rpm. This was then slowly added to the composition obtained in Step 2. The resultant mixture was combined with the water for WOW. Step 4 In a fourth reaction vessel, the second polymer was combined with the water for second polymer. The second polymer solution was then combined with the composition obtained in Step 3 and mixed for 10 mins at 3800 rpm.

Step 5 The acidifier was then added to the composition obtained in Step 4 to lower the pH to 4.8.

Step 6 The composition was then cooled to 10±3 °C.

Step 7 The crosslinking agent was then added to the composition in two parts (50% at start and 50% after 1 hour). The pH was then adjusted to 7.3 to 7.4 and the composition was left for two hours.

Step 8 In a fifth reaction vessel, the dispersant was combined with the antifreeze/emollient, and this mixture was then added to the composition obtained in Step 7.

Routine subsequent steps may be used to work up the formulation obtained in Step 8 and extract the microcapsules from the formulation, such as evaporation, freeze-drying or spray-drying. The dried microcapsules can then be applied to a material/surface.

Alternatively, the formulation obtained in Step 8 may be directly applied to a material/surface. The material/surface is then allowed to air dry. Once dry, the material//surface will have the microcapsules of the invention affixed to it.

It is important to note that the amounts of reagents given in Table 1 are merely exemplary and may vary depending on the requirements of the desired application, and that such variations fall within the scope of the present invention.

Example 2 - Evaluation of microencapsulation

Observation of microcapsules obtained in accordance with the method given in Example 1 was undertaken to confirm whether the cargo had been successfully microencapsulated.

Wet capsule observations Light microscopy was used at x 10 and x 40 magnification to observe the wet microcapsules. The microcapsules were observed to have the structural features of the polynuclear microcapsules depicted in Figure 1.

No evidence of residual outer capsule wall material, undissolved polymer, capsule rupture or partial capsule rupture was found. Further, no flocculation of capsules was observed at the sample substrate level. This confirmed that the wet capsules were stable.

Evidence of inner capsules within the outer capsules was however observed, with the inner capsules containing water, the quaternary ammonium composition and first and second stabilisers. No flocculation, lumps or ‘scrambled egg’ appearance was observed in the liquid formulation. This confirmed that the quaternary ammonium composition had been successfully microencapsulated.

Dry capsule observations

Light microscopy was used at x 10 and x 40 magnification to observe the dry microcapsules (wet microcapsules left to dry for 2 hours).

Clear outer capsule walls were observed between capsules, with the images suggesting that the outer capsule walls were both strong and intact. This confirmed that the dry capsules were stable.

Example 3 - Antimicrobial activity of microcapsules

The efficacy of the microcapsules of the invention against microbes is evaluated as follows.

Several 4 cm ² (surface area) samples of non-woven material are contaminated with a measured amount of a selected microbe (10,000 CFU). The samples are then treated with microcapsules of the invention prepared in accordance with Example 1 above, which are applied by spraying at a rate of 1 g per m ² . The levels of microbes on the surface are then measured at regular intervals and the results tabulated.

By modifying the mixture of quaternary ammonium compounds in the cargo contained within the microcapsule, the optimum antimicrobial composition for the selected microbe can be identified.

Example 4 - Application of microcapsules to non-woven material

Microcapsules additionally containing around 5.5% w/w eucalyptus oil in the oil phase were prepared in accordance with the method of the invention. Facial tissues were then sprayed with these microcapsules, at an amount of 0.8 to 1.2 g of microcapsule per m ² of tissue. This is a typical amount that would be sprayed by paper converters to apply fragrances to facial tissues.

The samples demonstrated good fragrance release over a three-week period. This is indicative of good cargo release over a three-week period because the fragrance (eucalyptus oil) was encapsulated along with the cargo. In other words, fragrance release indicates rupture of microcapsules.

This result suggests that, once dry, the microcapsules of the invention are stable for a significant period of time and achieve an improved ‘window of activity’ for cargoes in general and hydrophilic antimicrobial compositions in particular. This is done by extending the period of time after application in which the antimicrobial compositions retain disinfectant capability.

Example 5 - Rupture of microcapsules

Experiments were undertaken to assess whether the microcapsules of the invention are successfully ruptured under certain different conditions. To this end, microcapsules comprising a fragrance (eucalyptus oil) were prepared in accordance with the method of the invention described in the Example 1 above. Olfactory analysis was used at various points throughout the experiment to determine the amount of fragrance being released at a given time - a clear indication of the degree of rupture. Olfactory scores were ranked on a scale from 1 to 10, with 1 being the lowest score (i.e. very little fragrance released, and so by extension very little rupture) and 10 being the highest score (i.e. large amounts of fragrance released, and so by extension large amounts of rupture). More specifically, scoring 0-3 indicates low odour, 4-6 medium odour and 7-10 high odour. To conclusively corroborate the results of the olfactory analysis, images were taken using a 5MG LCOS digital camera and Brunel SP300 Compound Light Microscope.

Example 5 A - Rupture of microcapsules by mechanical mechanism

Microcapsules were prepared in accordance with the method of the invention described in the Example 1.

In a first assessment, these microcapsules were applied to a microscope glass slide without a cover slip using a glass rod and spread out over a thin layer, and an initial “wet” olfactory assessment was performed. The microcapsules were then left to dry for 12 hours, after which time a “dry” olfactory assessment was performed. To corroborate the olfactory assessment, images were taken using a 5MG LCOS digital camera and Brunel SP300 Compound Light Microscope. After 12 hours, the glass slide was subjected to a light mechanical abrasion, and a “ruptured” olfactory analysis then performed. Light microscopy was again used to corroborate the findings of the olfactory assessment.

In a second assessment, the first assessment was replicated except that a facial tissue was used in place of the microscope slide. The microcapsules were sprayed onto the surface of the facial tissue at a rate of 1.0 g/m ² , and an initial “wet” olfactory assessment was then performed. The facial tissue was then left to dry, after which time a “dry” olfactory assessment was performed. To corroborate the olfactory assessment, images were taken using a 5MG LCOS digital camera and Brunel SP300 Compound Light Microscope. Subsequently, the facial tissue was then rubbed, as of normal use, and a final “ruptured” olfactory assessment was performed. Light microscopy was again used to corroborate the findings of the olfactory assessment. The results of the first and second assessments are summarised in Table 2 below.

Table 2: olfactory results for mechanical rupture

In the first assessment, very little fragrance release was detected by the olfactory system after the drying stage, indicating that no rupture had yet occurred, and the relevant microscopy images demonstrated that the microcapsule walls were present and undisrupted, thus confirming the results of the olfactory analysis. Indeed, the fragrance was almost undetectable when the microcapsules had dried. By contrast, a score of 9 out of 10 was awarded after the addition of moisture, indicating a significant degree of rupture and release of cargo after application of mechanical pressure. Light microscopy confirmed that the microcapsules had been ruptured and the cargo released at this stage of the assessment. Similar findings were made during the second assessment

The results of the first and second assessments demonstrate that the microcapsules of the invention are secure and stable during application, and that they are successfully ruptured by mechanical shear when desired (e.g. during intended use of article upon which microcapsules have been applied). In particular, during wet and dry assessment, scores of 0-3 indicating low odour were awarded. By contrast, during rupture assessment, scores of 7-10 indicating high odour were awarded. All olfactory findings were corroborated by light microscopy. These findings are surprising.

Example 5B - Rupture of microcapsules by physical mechanism

Microcapsules were prepared in accordance with the method of the invention described in the Example 1. In a third assessment, the microcapsules were applied to a non-woven material and left to dry for 12 hours. Water was then sprayed at a rate of 1.0 g/m ² onto the surface of the nonwoven material. An olfactory analysis was then performed.

In a fourth assessment, the microcapsules were applied to a microscope slide without a cover slip using a glass rod and spread out over a thin layer, and an initial “wet” olfactory assessment was performed. The microcapsules were then left to dry for 12 hours, after which time a “dry” olfactory assessment was performed. To corroborate the olfactory assessment, images were taken using a digital camera (5MG LCOS) and Brunel SP300 Compound Light Microscope. After 12 hours, 1.0 pl of water was applied to the microscope slide whilst on the stage, and a final “ruptured” olfactory assessment was performed. Light microscopy was again used to corroborate the findings of the olfactory assessment.

In a fifth assessment, the fourth assessment was replicated except that a non-woven material was used in place of the microscope slide. The microcapsules were sprayed onto the surface of the non-woven material at a rate of 1.0 g/m ² , and an initial “wet” olfactory assessment was then performed. The non-woven material was then left to dry for 12 hours, after which time a “dry” olfactory assessment was performed. Finally, water was sprayed as of normal use at a rate of 1.0 g/m ² , and a “ruptured” olfactory assessment was then performed.

The results of the fourth and fifth assessments are summarised in Table 3 below.

Table 3: olfactory results for physical rupture Surprisingly, in the third assessment a fragrant odour of eucalyptus was released, indicating rupture of microcapsules. To confirm this finding, the second and third assessments were undertaken, using compound light microscopy. In the fourth assessment, very little fragrance release was detected by the olfactory system after the drying stage, indicating that no rupture had yet occurred, and the relevant microscopy images demonstrated that the microcapsule walls were present and undisrupted. A score of 7 out of 10 was awarded after the addition of moisture, indicating a significant degree of rupture. Light microscopy confirmed that the microcapsules had been ruptured and the cargo released.

The results of the third to fifth assessments demonstrate that the microcapsules of the invention are secure and stable during application, and that they are successfully ruptured by moisture when desired (e.g. during intended use of article upon which microcapsules have been applied). In particular, during wet and dry assessment, scores of 0-3 indicating low odour were awarded. By contrast, during rupture assessment, scores of 7-10 indicating high odour were awarded. All olfactory findings were corroborated by light microscopy. These findings are surprising.