Microcapsules and methods thereof

Abstract

The present disclosure concerns a method of forming a microcapsule, comprising a) emulsifying an oil in an aqueous medium in the presence of an ionic surfactant to obtain an oil-in-water emulsion, the ionic surfactant is configured to form a layer of charged 5 groups at an oil-water interface; b) homogenising a first chargeable polysaccharide or derivative thereof with the emulsion of step a), the first chargeable polysaccharide or derivative thereof is configured to form a first layer of charged polysaccharide on the layer of charged groups, the first layer of charged polysaccharide having an opposite charge to the layer of charged groups, c) optionally homogenising a further chargeable 10 polysaccharide or derivative thereof with the emulsion of step b), the further chargeable polysaccharide or derivative thereof is configured to form a further layer of charged polysaccharide on the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge to the first layer of charged polysaccharide; d) optionally repeating step c); and e) cross-linking the first layer of charged 15 polysaccharide and the optional further layer of charged polysaccharides with a cross- linker in order to form the microcapsule; wherein the first and second chargeable polysaccharide or derivative thereof is selected independently from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof; and wherein the method is conducted at ambient temperature.

Description

[0001] Microcapsules and Methods Thereof

[0002] Technical Field

[0003] The present invention relates, in general terms, to microcapsules and methods of their fabrication.

[0004] Background

[0005] Currently used synthetic encapsulation materials are highly efficient and perform according to customers' expectations with respect to fragrance delivery and release, which translates into growing sales and profits for the manufacturers. The proposed ECHA restrictions on microplastics, formaldehyde and siloxanes in products allowed on EU / EEA marked threaten this status quo, and force companies to invest and search for technologies and solutions. Moreover, there is a growing group of customers aware of the environmental impact of the products they use. This fast-growing group makes conscious efforts to search for products that do not harm the environment. Hence, there is an urgent need to promote and develop technologies based on natural, biocompatible, and biodegradable materials that may successfully replace the existing, synthetic ones. Encapsulation of actives is of great importance in cosmetics, pharma, and consumer care industries as it allows greater stability of the sensitive ingredients and, consequently, longer shelf life of the products. A very important group of such actives are essential and fragrant oils used in perfumes, fresheners, softeners, aromatherapy, etc. Due to allergenic potential, sensitivity to external conditions and high price of the oils it is crucial that they may be effectively encapsulated in a simple process, with high yield, and released in controlled manner. The customers' expectation as well as changing legislation imply use of natural, biocompatible materials, with low allergenic potential, and abolishment toxic chemicals.

[0006] It would be desirable to overcome or ameliorate at least one of the above-described problems.

[0007] Summary

[0008] The present disclosure concerns a method of forming a microcapsule, comprising : a) emulsifying an oil in an aqueous medium in the presence of an ionic surfactant to obtain an oil-in-water emulsion, the ionic surfactant is configured to form a layer of charged groups at an oil-water interface; b) homogenising a first chargeable polysaccharide or derivative thereof with the emulsion of step a), the first chargeable polysaccharide or derivative thereof is configured to form a first layer of charged polysaccharide on the layer of charged groups, the first layer of charged polysaccharide having an opposite charge to the layer of charged groups, c) optionally homogenising a further chargeable polysaccharide or derivative thereof with the emulsion of step b), the further chargeable polysaccharide or derivative thereof is configured to form a further layer of charged polysaccharide on the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge to the first layer of charged polysaccharide; d) optionally repeating step c); and e) cross-linking the first layer of charged polysaccharide and the optional further layer of charged polysaccharides with a cross-linker in order to form the microcapsule; wherein the first and second chargeable polysaccharide or derivative thereof is independently selected from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof; and wherein the method is conducted at ambient temperature.

[0009] In some embodiments, the emulsifying step (step a)) further comprises mixing.

[0010] In some embodiments, the emulsion is characterised by a volume ratio of aqueous medium to oil of about 1 : 1 to about 15: 1. In some embodiments, the ratio is about 2: 1 to about 9: 1.

[0011] In some embodiments, the emulsion is characterised by a mass ratio of ionic surfactant to oil of about 1 : 500 to about 1 : 5. In some embodiments, the ratio is about 1 :450 to about 9:250. In some embodiments, the ratio is about 1 :450 to about 1 : 10.

[0012] In some embodiments, the oil is selected from fragrant oils, essential oils, natural oils, synthetic oils, and a combination thereof. In some embodiments, the oil is selected from orange oil, thyme oil, (R)-(+)-limonene, and oils comprising multiple fragrant molecules.

[0013] In some embodiments, the oil is void of an organic solvent. In some embodiments, the oil is characterised by a molecular weight of about 100 g / mol to about 200 g / mol.

[0014] In some embodiments, the ionic surfactant is selected from hexadecyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), dimethyldioctadecylammonium bromide (DDAB), sodium dodecyl sulfate (SDS), sodium lauryl ether sulfate (SLES), ammonium lauryl sulfate (ALS), sodium lignosulfonate, gum Arabic, and a combination thereof. In some embodiments, the ionic surfactant is selected from hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), sodium lignosulfonate, gum Arabic, and a combination thereof.

[0015] In some embodiments, the homogenising step (step b) and / or step c)) is performed at a homogenising speed of about 150 rpm to about 30000 rpm, or at a speed of about 20 kHz to about 100 kHz. In some embodiments, the speed is about 200 rpm to about 800 rpm. In some embodiments, the speed is about 2000 rpm to about 20000 rpm.

[0016] In some embodiments, step d) is performed at least 1 time.

[0017] In some embodiments, the layer of charged polysaccharide is covalently cross-linked.

[0018] In some embodiments, the cross-linker is selected from glyoxal, transglutaminase, adipic acid dihydrazide, glutaraldehyde, epichlorohydrin, and acrylates. In some embodiments, the cross-linker is adipic acid dihydrazide. In some embodiments, the cross-linker is glyoxal.

[0019] In some embodiments, the method is characterised by a mass ratio of cross-linker to a total mass of polysaccharide of about 1 : 1 to about 3: 1. In some embodiments, the ratio is about 2: 1.

[0020] In some embodiments, step e) further comprises adding a pH modulator.

[0021] In some embodiments, the pH modulator is an acid.

[0022] In some embodiments, the pH modulator is selected from hydrochloric acid, citric acid and acetic acid. In some embodiments, the pH modulator is hydrochloric acid. In some embodiments, cross-linking occurs at a pH of less than about 4.

[0023] In some embodiments, step e) further comprises mixing.

[0024] In some embodiments, the mixing is performed at a mixing speed of about 150 rpm to about 30000 rpm. In some embodiments, the mixing speed is about 350 rpm. In some embodiments, the mixing is performed at a mixing speed of about 20kHz to about 100 kHz.

[0025] In some embodiments, the ambient temperature is about 10 °C to about 30 °C.

[0026] In some embodiments, the method is characterised by a volume percentage of oil relative to the total volume used for forming microcapsules of about 4% to about 12%. In some embodiments, the volume percentage is about 5% to about 10%.

[0027] In some embodiments, the method is characterised by an encapsulation efficiency of more than about 90%.

[0028] In some embodiments, the method is characterised by a microcapsule size of about 0.1 pm to about 20 pm. In some embodiments, the method is characterised by a microcapsule size of about 0.1 pm to about 10 pm.

[0029] The present disclosure also concerns a microcapsule formed by the method as disclosed herein.

[0030] The present disclosure also concerns a microcapsule comprising a core and a shell, wherein the core comprises an oil; wherein the shell comprises: a) a layer of charged groups; b) a first layer of charged polysaccharide ionically attracted to the layer of charged groups, the first layer of charged polysaccharide having an opposite charge to the layer of charged groups; and c) optionally a further layer of charged polysaccharide ionically attracted to the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge to the first layer of charged polysaccharide; wherein the first layer of charged polysaccharide and the optional further layer of charged polysaccharide are cross-linked.

[0031] In some embodiments, the microcapsule is characterised by a particle size of about 0.1 pm to about 20 pm. In some embodiments, the size is about 0.1 pm to about 10 pm.

[0032] In some embodiments, the polysaccharide is selected from selected from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof.

[0033] The present disclosure also concerns a formulation, comprising microcapsules as disclosed herein.

[0034] Brief description of the drawings

[0035] Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the drawings in which:

[0036] Figure 1 shows a schematic representation of encapsulation process. Encapsulation of an essential or fragrant oil (hydrophobic compound) requires formulation of a single, O / W, emulsion (Step "A"), and deposition of a shell-forming material (Step "B"), followed by covalent cross-linking (Step"C"). Step "B" can be repeated using oppositely charged polyelectrolytes to form a thicker, multi-layered capsule shell.

[0037] Figure 2 shows examples of encapsulated essential oil (thyme oil) in sodium alginate- based capsule (top) and fragrant oil ((R)-(+)-limonene) in gum Arabic-based capsule (bottom). Length of the scale bars corresponds to 10 pm.

[0038] Figure 3 shows a visual assessment of stability of first-generation polysaccharide-based capsules, loaded with thyme oil, 14 days after preparation. Brown, yellowish and whitish colour of the aqueous phase result from excess of LA and SAMV in solutions, respectively. Layers of free oil are indicated.

[0039] Figure 4 shows a visual assessment of stability of first-generation polysaccharide-based capsules, loaded with orange oil, 14 days after preparation. Brown, yellowish and whitish colour of the aqueous phase result from excess of LA and SAMV in solutions, respectively. Layers of free oil are indicated.

[0040] Figure 5 shows a visual assessment of stability of first-generation polysaccharide-based capsules, loaded with (R)-(+)-limonene, 14 days after preparation. Brown, yellowish and whitish colour of the aqueous phase result from excess of LA and SAMV. Layers of free oil are indicated.

[0041] Figure 6 shows a visual assessment of stability of second-generation capsules, comprising SAMV, loaded with orange oil, (R)-(+)-limonene and thyme oil. Yellow colour result from colour of the orange oil.

[0042] Figure 7 shows a visual assessment of stability of second generation capsules, comprising lignin (bottom) and combination of lignin and chitosan (top), loaded with orange oil, (R)-(+)-limonene and thyme. Brownish colour of the aqueous phase result from excess of lignin alkaline. Indicated free layer of thyme oil.

[0043] Figure 8 shows a visual assessment of stability of second generation capsules, comprising Gum Arabic (bottom) and combination of gum Arabic and chitosan (top), loaded with orange oil, (R)-(+)-limonene and thyme oil. Yellow colour result from colour of the orange oil.

[0044] Figure 9 shows a visual assessment of stability of LA-based capsules, loaded with PERF 12-11723 Fresh Boost V2, 17 days after preparation. The sample compositions are provided in Table 6.

[0045] Figure 10 shows examples of size distribution and morphology of second-generation capsules. Length of the scale bars corresponds to 10 pm.

[0046] Figure 11 shows optical microscopy images of selected first-generation capsules. Length of the scale bars corresponds to 75 pm.

[0047] Figure 12 shows variation of size distributions between batches of LA-based capsules containing PERF 12-11723 Fresh Boost V2. Dates of samples preparation are indicated in sample names: 28 Aug 2023, 14 Sept 2023, and 10 Oct 2023. Sample composition is described in Table 6.

[0048] Detailed description

[0049] The present disclosure concerns a method of forming a microcapsule, the microcapsule encapsulating an oil within. The microcapsule may comprise fragrant oils, essential oils, natural oils and / or synthetic oils that may be used in personal care products and household products such as perfumes, fresheners, softeners and aromatherapy. Encapsulation may promote gradual release of the oils over a longer time at a stable release rate, ensuring that the fragrance is not overwhelming, for example in perfumes. The fragrant and / or essential oil may be released at an optimal concentration and may last longer. The forming methods comprises biodegradable polysaccharide-based microcapsules and may be free of organic solvents and toxic chemicals. The method may be free from the generation of chemical waste that require specialised treatments. The microcapsule may be formed using biodegradable and non-hazardous materials and the forming method may be environmentally friendly and scalable for different types of oil.

[0050] A microcapsule is a small, spherical shaped particle that comprises a core material surrounded by a shell. The core material may be an active ingredient such as fragrant oils and / or essential oils. The shell may be made from a polymeric material and may serve to encapsulate and protect the core material, controlling its release or interaction with the surrounding environment. A microcapsule may have a size ranging from 0.1 pm to about 1000 pm.

[0051] The present disclosure concerns a method of forming a microcapsule, comprising : a) emulsifying an oil in an aqueous medium in the presence of an ionic surfactant to obtain an oil-in-water emulsion, the ionic surfactant is configured to form a layer of charged ionic surfactant at an oil-water interface; b) homogenising a first chargeable polysaccharide or derivative thereof with the emulsion of step a), the first chargeable polysaccharide or derivative thereof is configured to form a first layer of charged polysaccharide on the layer of charged ionic surfactant, the first layer of charged polysaccharide having an opposite charge to the layer of charged ionic surfactant, c) optionally homogenising a further chargeable polysaccharide or derivative thereof with the emulsion of step b), the further chargeable polysaccharide or derivative thereof is configured to form a further layer of charged polysaccharide on the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge to the first layer of charged polysaccharide; d) optionally repeating step c); and e) cross-linking the first layer of charged polysaccharide and the optional further layer of charged polysaccharides with a cross-linker in order to form the microcapsule; wherein the first and second chargeable polysaccharide or derivative thereof is selected independently from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof; and wherein the method is conducted at ambient temperature.

[0052] An emulsion may be a heterogeneous mixture of two or more immiscible liquids, such as oil and water, where one liquid is dispersed in the other as droplets, stabilised by surfactants and / or emulsifying agents. The emulsion may be kinetically stable. Two liquids may form different types of emulsions. For example, oil and water may form an oil-in-water emulsion in which the oil is the dispersed phase and water is the continuous phase. Oil and water may also form a water-in-oil emulsion in which the water is the dispersed phase and oil is the continuous phase. The droplet size may range from several nanometres to several hundred micrometres. A nanoemulsion may be a kinetically stable dispersion of one liquid within another and may be stabilised by an emulsifier and / or surfactant. A nanoemulsion may be formed by high shear mixing or ultrasonic methods. The droplet size may range from about 20 nm to about 200 nm. A microemulsion may be a thermodynamically stable mixture of oil, water and surfactant. A microemulsion may be formed spontaneously upon mixing of the components and may not require high shear conditions. A microemulsion may be an oil-in-water microemulsion, a water-in-oil microemulsion or bicontinuous microemulsion. The droplet size may range from about 10 nm to about 100 nm.

[0053] A Pickering emulsion is a type of emulsion that is stabilised by solid particles instead of surfactants (e.g. soaps or detergents). The solid particles adsorb onto the interface between the two immiscible liquids, such as oil and water, and prevent the droplets from coalescing. This is not within the scope of the present disclosure.

[0054] The oil may be emulsified in an aqueous medium to form an oil-in-water emulsion. An oil-in-water emulsion is a type of emulsion where the dispersed phase is composed of a lipophilic liquid and / or phase (e.g. oil droplets) and the continuous phase is a hydrophilic liquid and / or phase (e.g. water). The dispersed phase may comprise one or more types of oils, such as fragrant oils, essential oils, natural oils, or synthetic oils. The oil droplets may be microscopic in size, ranging from a few nanometres to a few micrometres in diameter. The continuous phase may be a water-based medium, which may also comprise additives such as emulsifiers. An emulsifier may be used to stabilise the oil- in-water emulsion by reducing the interfacial tension between the oil and water phases.

[0055] In some embodiments, the oil is selected from fragrant oils, essential oils and a combination thereof. The oil may be natural oil, synthetic or a combination thereof. The oil may be a fragrance composition comprising natural oil, synthetic oil, or a combination of both fragrant and essential oils. Natural oils may be extracted or derived directly from natural sources such as plants, animals or minerals. Synthetic oils may be manufactured through chemical synthesis and may comprise of a blend of synthetic aromatic compounds such as alcohols, esters, ketones and terpenes. Fragrant oils may be a blend of synthetic or natural aromatic compounds and may be perfume oils. The fragrant oils may be formulated to mimic the scent of natural essential oils or to create different fragrance profile. The fragrant oil may be oils with a floral scent (rose oil, jasmine oil). a citrus scent (lemon oil, orange oil, bergamot oil). Essential oils may be concentrated, volatile and aromatic liquids extracted from various parts of plants, such as flowers, leaves, stems, roots or fruits. The essential oil may be lavender oil, peppermint oil, tea tree oil, lemon oil, thyme oil, orange oil, or rosemary oil.

[0056] The oil may be lavender oil, peppermint oil, tea tree oil, lemon oil, limonene, thyme oil, orange oil, bergamot oil, jasmine oil, rose oil, rosemary oil, synthetic oils, or oils comprising multiple fragrant molecules. In some embodiments, the oil is selected from orange oil, thyme oil, (R)-(+)-limonene, and oils comprising multiple fragrant molecules.

[0057] In some embodiments, the oil is void of an organic solvent. This may reduce the toxicity of the emulsion and / or microcapsule, improving biocompatibility for applications in personal care products. This may also improve safety and may be more environmentally friendly as most organic solvents such as alcohols, hydrocarbons, or halogenated solvents may be toxic, flammable or may have negative environmental impacts.

[0058] In some embodiments, the oil is characterised by a molecular weight of about 100 g / mol to about 200 g / mol. In other embodiments, the molecular weight is about 100 g / mol to about 180 g / mol, about 100 g / mol to about 150 g / mol, about 100 g / mol to about 130 g / mol, about 130 g / mol to about 200 g / mol, about 130 g / mol to about 180 g / mol, about 130 g / mol to about 150 g / mol, about 150 g / mol to about 200 g / mol, about 150 g / mol to about 180 g / mol, or about 180 g / mol to about 200 g / mol.

[0059] In some embodiments, the aqueous medium may be an aqueous suspension comprising an ionic surfactant. An aqueous suspension is a heterogeneous mixture where the molecules of the ionic surfactant are dispersed throughout a continuous liquid phase. The continuous phase may be water which acts as the medium in which the molecules of the ionic surfactant are suspended. The distribution of the ionic surfactant within the liquid phase may not be uniform. Over time, the dispersed ionic surfactant phase in the suspension may settle due to gravity. The stability of the aqueous suspension my depend on the concentration of the ionic surfactant, the viscosity of the liquid phase and the presence of any stabilising agents.

[0060] The ionic surfactant comprises an amphiphilic structure, wherein the ionic surfactant comprises a hydrophilic head group and a hydrophobic tail. The hydrophilic head group comprises an ionic (charged) part and the hydrophobic tail may comprise a hydrocarbon chain. The ionic head group may be positively charged (cationic) or negatively charged (anionic). Cationic surfactants may be hexadecyltrimethylammonium bromide (CTAB), cetyl pyridinium chloride (CPC), benzalkonium chloride (BAC) or dimethyldioctadecylammonium bromide (DDAB). Anionic surfactants may be sodium dodecyl sulfate (SDS), sodium lauryl ether sulfate (SLES), or ammonium lauryl sulfate (ALS). When dispersed in an aqueous medium, the charge on the ionic surfactant molecules may allow the ionic surfactant molecules to adsorb to the oil-water interface between the oil droplet and water, forming a layer of charged ionic surfactant around the oil droplet, the charged ionic surfactant comprising the charged groups. The ionic surfactant molecules may arrange themselves with the hydrophilic heads facing the aqueous environment and the hydrophobic tails pointing inwards into the oil droplet. This arrangement creates a charged surface, where the head groups of the ionic surfactant molecules carry an electrical charge. The charged nature of the layer of charged ionic surfactant may arise from the dissociation of the head groups, which may be positively charged or negatively charged. The layer of charged ionic surfactant around the oil droplet may provide electrostatic stabilisation and steric stabilisation.

[0061] The ionic surfactant may form a layer of charged groups at the oil-water interface, surrounding the oil droplet. The charged groups may be positively charged or negatively charged. In this regard, the aqueous medium may further comprise an acid or an alkaline in order to modulate the pH of the emulsion. Depending on the type of ionic surfactant, the pH may be modulated accordingly. For example, if the ionic surfactant is CTAB, the pH of the aqueous medium may be about 6 to less than about 8. For example, if the ionic surfactant is SDS, the pH of the aqueous medium may be about more than 6 to about 8.

[0062] The ionic surfactant may improve the stability of the emulsion and affect the oil droplet size and size distribution. The presence of the layer of charged ionic surfactant may increase the viscosity of continuous liquid phase, further contributing to the stability of the emulsion. When the ionic surfactant adsorbs at the oil-water interface, it may reduce the interfacial tension between the lipophilic phase (e.g. oil) and hydrophilic phase (e.g. water). The reduction may make it easier to break the oil into smaller droplets during the emulsification process. The layer of charged ionic surfactant may provide electrostatic stabilisation and prevent coalescence of oil droplets. The concentration of the ionic surfactant in the emulsion may affect the droplet size. A higher concentration of the ionic surfactant may lead to the formation of smaller oil droplets as more ionic surfactant molecules are available to adsorb at the oil-water interface and stabilise the smaller droplets.

[0063] In some embodiments, the ionic surfactant is selected from hexadecyltrimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), dimethyldioctadecylammonium bromide (DDAB), sodium dodecyl sulfate (SDS), sodium lauryl ether sulfate (SLES), ammonium lauryl sulfate (ALS), sodium lignosulfonate, gum Arabic, and a combination thereof. In some embodiments, the ionic surfactant is selected from hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), sodium lignosulfonate, gum Arabic, and a combination thereof. CTAB and SDS may be used as ionic surfactants in various industries such as personal care where the formation of charged layers at oil-water interfaces is important for stabilisation, wettability, and control. Gum Arabic is a natural emulsifier and stabiliser and may also be an ionic surfactant. Gum Arabic may be negatively charged at a pH above about 2.2, which is the approximate pKa, due to deprotonation of the carboxylic groups on its glucuronic acid residues. Gum Arabic may act as both a charged polysaccharide layer and an ionic surfactant in the formation of the microcapsules.

[0064] The lipophilic phase, e.g. oil, may be added to the aqueous suspension dropwise or at a speed of about 0.1 ml / min to about 2 ml / min. In other embodiments, the speed may be about 0.1 ml / min to about 1.5 ml / min, about 0.1 ml / min or about 1 ml / min, about 0.1 ml / min to about 0.5 ml / min, about 0.5 ml / min to about 2 ml / min, about 0.5 ml / min to about 1.5 ml / min, about 0.5 ml / min to about 1 ml / min, about 1 ml / min to about 2 ml / min, or about 1 ml / min to about 1.5 ml / min. The oil may be added using a pipette.

[0065] The emulsion may be formed by mixing. Mixing is a process of combining two or more substances to make them uniform and may involve multiple liquids. Mixing may be performed using various tools and methods. For example, an overhead stirrer at 350 rpm may be used. Based on the method of the present disclosure, this will give an oil droplet size of about 5 pm to about 30 pm.

[0066] Alternatively, the emulsion may be formed using a homogeniser. Homogenising may also be used. Homogenising may be a more intense and high-shear process and may reduce the size of dispersed particles. This may create a stable, uniform mixture in emulsions. High shear forces applied during homogenisation may reduce the size of the oil droplets and thus the size of the microcapsules formed. The homogenisation may be performed continuously to maintain the homogeneous suspension. When the homogenisation is performed at a mixing speed of about 5000 rpm to about 25000 rpm, the oil droplet size is about 100 nm to about 10000 nm. The homogenisation may be performed using an ultrasound homogeniser. An ultrasound homogeniser may use high frequency sound waves to break down and disperse particles in a liquid sample. When an ultrasound homogeniser is used at about 20 kHz to about 40 kHz, the oil droplet size is about 100 nm to about 10000 nm.

[0067] Both types of mixing have been found to be acceptable for forming microcapsules for use in consumer care products.

[0068] In some embodiments, the emulsifying step (step a)) further comprises mixing.

[0069] In some embodiments, the mixing is performed at a mixing speed of about 150 rpm to about 30000 rpm. In other embodiments, the speed may be about 150 rpm to about 25000 rpm, about 150 rpm to about 20000 rpm, about 150 rpm to about 15000 rpm, about 150 rpm to about 10000 rpm, about 150 rpm to about 5000 rpm, about 150 rpm to about 1000 rpm, about 1000 rpm to about 30000 rpm, about 1000 rpm to about 25000 rpm, about 1000 rpm to about 20000 rpm, about 1000 rpm to about 15000 rpm, about 1000 rpm to about 10000 rpm, about 1000 rpm to about 5000 rpm, about 5000 rpm to about 30000 rpm, about 5000 rpm to about 25000 rpm, about 5000 rpm to about 20000 rpm, about 5000 rpm to about 15000 rpm, about 5000 rpm to about 10000 rpm, about 10000 rpm to about 30000 rpm, about 10000 rpm to about 25000 rpm, about 10000 rpm to about 20000 rpm, about 10000 rpm to about 15000 rpm, about 15000 rpm to about 30000 rpm, about 15000 rpm to about 25000 rpm, or about 15000 rpm to about 20000 rpm. In other embodiments, the speed is about 150 rpm to about 800 rpm, about 150 rpm to about 600 rpm, about 150 rpm to about 300 rpm, about 300 rpm to about 1000 rpm, about 300 rpm to about 800 rpm, about 300 rpm to about 600 rpm, about 600 rpm to about 1000 rpm, about 600 rpm to about 800 rpm or about 800 rpm to about 1000 rpm. In some embodiments, the mixing speed is about 350 rpm. In some embodiments, the mixing speed is about 5000 rpm to about 25000 rpm.

[0070] In some embodiments, the mixing is performed using an ultrasound homogeniser.

[0071] In some embodiments, the mixing speed is performed at about 20 kHz to about 100 kHz. In other embodiments, the speed is about 20 kHz to about 80 kHz, about 20 kHz to about 50 kHz, about 20 kHz to about 40 kHz, about 40 kHz to about 100 kHz, about 40 kHz to about 80 kHz, about 40 kHz to about 50 kHz, about 50 kHz to about 100 kHz, or about 50 kHz to about 80 kHz.

[0072] In some embodiments, the emulsion is characterised by a volume ratio of aqueous medium to oil of about 1 : 1 to about 15:1. In other embodiments, the ratio is about 1:1 to about 13:1, about 1:1 to about 10:1, about 1:1 to about 8:1, about 1:1 to about 5:1, about 1:1 to about 3:1, about 1:1 to about 2:1, about 2:1 to about 15:1, about 2:1 to about 13:1, about 2:1 to about 10:1, about 2:1 to about 8:1, about 2:1 to about 5:1, about 2:1 to about 3:1, about 3:1 to about 15:1, about 3:1 to about 13:1, about 3:1 to about 10:1, about 3:1 to about 8:1, about 3:1 to about 5:1, about 5:1 to about 15:1, about 5:1 to about 13:1, about 5:1 to about 10:1, about 5:1 to about 8:1, about 8:1 to about 15:1, about 8:1 to about 13:1, about 8:1 to about 10:1, about 10:1 to about 15:1, or about 10:1 to about 13:1. An emulsion with a volume ratio of aqueous medium to oil of about 1 : 1 may be highly concentrated and may be difficult to stabilise. An emulsion with a volume ratio of aqueous medium to oil of about 15: 1 may be diluted, and the oil phase concentration may be too low in the microcapsule formed to be suitably used in personal care products or household products. In this regard, the ratio may be adjusted accordingly for various uses of the microcapsule. In some embodiments, the ratio is about 2: 1 to about 9:1. In some embodiments, the ratio is about 2:1. In some embodiments, the ratio is about 4:1. In some embodiments, the ratio is about 9:1.

[0073] In some embodiments, the emulsion is characterised by a mass ratio of ionic surfactant to oil of about 1:500 to about 1:5. In other embodiments, the ratio is about 1:500 to about 1:50, about 1:500 to about 1:100, about 1:500 to about 1:200, about 1:500 to about 1:300, about 1:500 to about 1:400, about 1:400 to about 1:10, about 1:400 to about 1:50, about 1:400 to about 1:100, about 1:400 to about 1:200, about 1:400 to about 1:300, about 1:300 to about 1:5, about 1:300 to about 1:50, about 1:300 to about 1:100, about 1:300 to about 1:200, about 1:200 to about 1:5, about 1:200 to about 1:50, about 1:200 to about 1:100, about 1:100 to about 1:5, about 1:100 to about 1:50, or about 1:50 to about 1:5. In some embodiments, the ratio is about 1:450 to about 9:250. In some embodiments, the ratio is about 1:450 to about 1:10.

[0074] Accordingly, the present disclosure concerns a method of forming a microcapsule, comprising: a) emulsifying an oil in an aqueous medium in the presence of an ionic surfactant to obtain an oil-in-water emulsion, the ionic surfactant is configured to form a layer of charged groups at an oil-water interface; b) homogenising a first chargeable polysaccharide or derivative thereof with the emulsion of step a), the first chargeable polysaccharide or derivative thereof is configured to form a first layer of charged polysaccharide on the layer of charged groups, the first layer of charged polysaccharide having an opposite charge to the layer of charged groups, c) optionally homogenising a further chargeable polysaccharide or derivative thereof with the emulsion of step b), the further chargeable polysaccharide or derivative thereof is configured to form a further layer of charged polysaccharide on the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge to the first layer of charged polysaccharide; d) optionally repeating step c); and e) cross-linking the first layer of charged polysaccharide and the optional further layer of charged polysaccharides with a cross-linker in order to form the microcapsule; wherein the first and second chargeable polysaccharide or derivative thereof is selected independently from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof; and wherein the method is conducted at ambient temperature.

[0075] Polysaccharides are large, complex carbohydrate molecules, comprising repeating monosaccharide units, such as glucose, fructose, or galactose. The way these monosaccharides are linked (the type of glycosidic bond) may determine the structure and properties of the polysaccharide. They may be linear (unbranched) or branched (with side chains). Polysaccharides may be naturally occurring, such as lignin, alginate, chitosan, gum Arabic, pectin, carrageenan, or starch. Naturally occurring polysaccharides may be biocompatible and biodegradable, making the capsules formed with naturally occurring polysaccharides suitable for use in personal care products such as cosmetic formulations.

[0076] Polysaccharides may be inherently charged or be chargeable depending on the pH of the emulsion. Some polysaccharides may carry an inherent charge due to their chemical structure and composition. For example, alginate and pectin are anionic due to the presence of carboxyl groups, while chitosan is cationic due to the presence of amino groups. A charged polysaccharide may interact electrostatically with the charged groups adsorbed at a surface of the oil droplet at the oil-water interface. This may lead to the formation of a charged polysaccharide layer around a layer of charged groups. In this regard, the pH of the emulsion may be modulated accordingly to facilitate the electrostatic attraction for forming the shell. Polysaccharides also include lignin derivatives. Polysaccharides suitable for forming the charged polysaccharide layer may be soluble in water and may contain chargeable groups, such as lignin, alginate, chitosan, gum Arabic, pectin, carrageenan, xanthan gum, and lignin alkaline.

[0077] In some embodiments, step b) comprises homogenising a first charged polysaccharide with the oil-in-water emulsion of step a), the first charged polysaccharide is configured to form a first layer of charged polysaccharide on the layer of charged groups, the first layer of charged polysaccharide having an opposite charge relative to the layer of charged groups.

[0078] In some embodiments, the first chargeable polysaccharide and / or further chargeable polysaccharide is selected from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof.

[0079] In some embodiments, step c) comprises optionally homogenising a further charged polysaccharide with the oil-in-water emulsion of step b), the further charged polysaccharide is configured to form a further layer of charged polysaccharide on the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge relative to the first layer of charged polysaccharide. This may form a bilayer of charged polysaccharide on the layer of charged solid particles. This step may be repeated (step d)) to form multiple layers of charged polysaccharide in a layer- by-layer manner. For example, a first layer of positively charged chitosan may form on the layer of charged groups, followed by a further layer of negatively charged alginate on the first layer of charged chitosan to form a bilayer of charged polysaccharide on the layer of charged groups.

[0080] In some embodiments, the method comprises homogenising a second charged polysaccharide with the oil-in-water emulsion of step b), the second charged polysaccharide is configured to form a further layer of charged polysaccharide on the first layer of charged polysaccharide, the second layer of charged polysaccharide having an opposite charge relative to the first layer of charged polysaccharide.

[0081] The second charged polysaccharide may be selected from lignin alkaline, chitosan, sodium alginate, gum Arabic and a combination thereof.

[0082] In some embodiments, the method comprises homogenising a third charged polysaccharide with the oil-in-water emulsion of step b), the third charged polysaccharide is configured to form a further layer of charged polysaccharide on the second layer of charged polysaccharide, the third layer of polysaccharide having an opposite charge relative to the second layer of charged polysaccharide.

[0083] The third charged polysaccharide may be selected from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof.

[0084] The homogenisation may be performed using a low-energy homogenisation or a high- energy homogenisation technique. The low-energy homogenisation may allow encapsulation of fragrance with smaller fraction of oil remaining free as compared to high pressure homogenisation. The low-energy homogenisation may be performed using rotor-stator mixers or overhead mixers. The lower shear forces and energy input associated with low-energy homogenisation may help to preserve the structure of the oil droplets and the capsules formed. The low-energy homogenisation may also minimise the risk of thermal degradation or oxidation and may require lower energy consumption. In some embodiments, the homogenisation is performed using an overhead mixer.

[0085] The high-energy homogenisation may be performed using high-shear rotor-stator homogeniser or ultrasound homogenisers. The high-energy homogenisation may increase the encapsulation effectiveness of the microcapsules. The high shear forces generated during homogenisation physically disrupt the larger oil droplets, causing them to break down into smaller, more uniform droplets. This may result in a significant reduction in the average droplet size, typically in the range of a few hundred nanometres to a few micrometres. The smaller droplet size increases the surface area-to-volume ratio and may allow for more efficient adsorption and coverage of the droplets by the ionic surfactant. This may enhance the emulsion's stability against coalescence. The high shear forces generated from the high energy homogenisation may help to prevent agglomeration of the capsules after forming. High-energy homogenisation may require continuous sample cooling due to large amount of heat generated during the process. The heat may affect the oil, thus the homogenisation may be carried out together with a cooling system.

[0086] In some embodiments, the homogenising step (step b) and / or step c)) is performed at a homogenising speed of about 150 rpm to about 30000 rpm. In other embodiments, the speed may be about 150 rpm to about 25000 rpm, about 150 rpm to about 20000 rpm, about 150 rpm to about 15000 rpm, about 150 rpm to about 10000 rpm, about 150 rpm to about 5000 rpm, about 150 rpm to about 1000 rpm, about 1000 rpm to about 30000 rpm, about 1000 rpm to about 25000 rpm, about 1000 rpm to about 20000 rpm, about 1000 rpm to about 15000 rpm, about 1000 rpm to about 10000 rpm, about 1000 rpm to about 5000 rpm, about 5000 rpm to about 30000 rpm, about 5000 rpm to about 25000 rpm, about 5000 rpm to about 20000 rpm, about 5000 rpm to about 15000 rpm, about 5000 rpm to about 10000 rpm, about 10000 rpm to about 30000 rpm, about 10000 rpm to about 25000 rpm, about 10000 rpm to about 20000 rpm, about 10000 rpm to about 15000 rpm, about 15000 rpm to about 30000 rpm, about 15000 rpm to about 25000 rpm, or about 15000 rpm to about 20000 rpm. In some embodiments, the speed is about 2000 rpm to about 20000 rpm.

[0087] In some embodiments, the homogenising step (step b) and / or step c)) is performed using an ultrasound homogeniser. In some embodiments, the homogenisation is performed at a homogenising speed of about 20 kHz to about 100 kHz. In other embodiments, the speed is about 20 kHz to about 80 kHz, about 20 kHz to about 50 kHz, about 20 kHz to about 40 kHz, about 40 kHz to about 100 kHz, about 40 kHz to about 80 kHz, about 40 kHz to about 50 kHz, about 50 kHz to about 100 kHz, or about 50 kHz to about 80 kHz.

[0088] In some embodiments, step d) is performed at least 1 time. In other embodiments, step d) is performed at least 2 times, at least 3 times, or at least 4 times. This may result in a microcapsule with three layers of charged polysaccharide, four layers of charged polysaccharide, five layers of charged polysaccharide, or six layers of charged polysaccharide.

[0089] The layer or layers of charged polysaccharide may undergo cross-linking reactions to form a stable shell around the oil droplet and the charged solid particles. The crosslinking may be triggered by the presence of specific ions, changes in pH, or the addition of cross-linking agents. The layer of charged polysaccharide may act as a barrier, controlling the release of the encapsulated oil. The layer of charged polysaccharide may further stabilise the emulsion by providing steric and / or electrostatic stabilisation in addition to the stabilisation provided by the charged solid particles. The stability of the capsule against partial release of oil may depend on the mass ratio between the crosslinker and the layers of polysaccharide. In some embodiments, step e) comprises cross-linking the first layer of charged polysaccharide and the optional further layer of charged polysaccharides with a crosslinker in order to form the capsule.

[0090] In some embodiments, the layer of charged polysaccharide is covalently cross-linked. Covalent cross-links may create stronger and more stable connections between the layers of charged polysaccharide, helping to maintain the shape and size of the microcapsule. It may improve the overall stability of the microcapsule, making the microcapsule less susceptible to dissociation, swelling, or deformation. The degree and nature of the covalent cross-links may be tailored to regulate the permeability of the microcapsule, allowing for controlled release or retention of the oil. Covalent cross-links may be more resistant to changes in pH and temperature compared to ionic or physical interactions, enhancing the stability and performance of the microcapsule in various environmental conditions.

[0091] The cross-linker may be a natural cross-linker or a synthetic cross-linker. Natural crosslinkers may be derived from natural sources such as living organisms or plants. A natural cross-linker may be an enzyme (e.g. transglutaminase) or phenolic compounds derived from natural sources (e.g. genipin). A synthetic cross-linker may be a chemically synthesised compound designed to create cross-linked structures, such as glutaraldehyde, epichlorohydrin, or acrylates. In some embodiments, the cross-linker is selected from glyoxal, transglutaminase, adipic acid dihydrazide, glutaraldehyde, epichlorohydrin, and acrylates. In some embodiments, the cross-linker is adipic acid dihydrazide. In some embodiments, the cross-linker is glyoxal.

[0092] In some embodiments, the mass ratio of cross-linker to a total mass of polysaccharide is about 1 : 1 to about 3: 1. The ratio may prevent the release of oil from the microcapsules. The ratio may result in aggregation of microcapsules into larger assemblies if the cross-linker is in excess of the polysaccharide.

[0093] In other embodiments, the ratio is about 1: 1 to about 2.5: 1, about 1 : 1 to about 2: 1, about 1 : 1 to about 1.5: 1, about 1.5: 1 to about 3: 1, about 1.5: 1 to about 2.5: 1, about 1.5: 1 to about 2: 1, about 2: 1 to about 3: 1, about 2: 1 to about 2.5: 1, or about 2.5: 1 to about 3: 1. Preferably, the mass ratio of crosslinker to a total mass of polysaccharide is 2: 1. In some embodiments, the method is characterised by a mass ratio of cross-linker to a total mass of polysaccharide of about 1: 1 to about 3: 1. In other embodiments, the mass ratio is about 1 : 1 to about 2.5: 1, about 1 : 1 to about 2: 1, about 1: 1 to about 1.5: 1, about 1.5: 1 to about 3: 1, about 1.5: 1 to about 2.5: 1, about 1.5: 1 to about 2: 1, about 2: 1 to about 3: 1, about 2: 1 to about 2.5: 1, or about 2.5: 1 to about 3: 1. In some embodiments, the mass ratio is about 2: 1.

[0094] In some embodiments, the cross-linking density of the polysaccharide is about 70% to about 95%. In other embodiments, the cross-linking density is about 70% to about 90%, about 70% to about 85%, about 70% to about 80%, about 70% to about 75%, about 75% to about 95%, about 75% to about 90%, about 75% to about 85%, about 75% to about 80%, about 80% to about 95%, about 80% to about 90%, about 80% to about 85%, about 85% to about 95%, about 85% to about 90%, or about 90% to about 95%.

[0095] In some embodiments, the cross-linking density of the shell is about 70% to about 95%. The shell refers to the polysaccharide formed around the oil droplet. In other embodiments, the cross-linking density is about 70% to about 90%, about 70% to about 85%, about 70% to about 80%, about 70% to about 75%, about 75% to about 95%, about 75% to about 90%, about 75% to about 85%, about 75% to about 80%, about 80% to about 95%, about 80% to about 90%, about 80% to about 85%, about 85% to about 95%, about 85% to about 90%, or about 90% to about 95%.

[0096] In some embodiments, step e) comprises adding the cross-linker to the emulsion of step d) in a step-wise manner or by parts. For example, if a total of 5 parts of crosslinker is to be added to the emulsion, 1 part may first be added to the emulsion and mixed for a certain duration. Subsequently, a second part may be added to the emulsion and mixed for a certain duration and so on for the third part, fourth part and fifth part.

[0097] In some embodiments, step e) further comprises adding a pH modulator. The pH modulator may alter the pH of the aqueous suspension to facilitate cross-linking of the layers of charged polysaccharide.

[0098] In some embodiments, the pH modulator is an acid. The acid may lower the pH of the aqueous suspension, facilitate the cross-linking of certain polysaccharides, such as alginate or chitosan, around the oil droplets. In some embodiments, the pH modulator is selected from hydrochloric acid, citric acid, and acetic acid. In some embodiments, the pH modulator is hydrochloric acid. Hydrochloric acid may introduce monovalent ions (Cl ) to the system. The monovalent ions may affect the solubility, conformation and / or reactivity of the charged polysaccharide and thus may affect their ability to be cross-linked. Acids such as phosphoric acid and sulfuric acid may introduce multivalent ions (PO43' and SC>42') which may affect or disrupt layer formation and cross-linking process. The hydrochloric acid may be IM HCI or about 3.7% HCI.

[0099] In some embodiments, cross-linking occurs at a pH of less than about 4. In other embodiments, the pH is about 3 to about 4.

[0100] In some embodiments, step e) further comprises mixing. Mixing may help to evenly distribute the cross-linker throughout the emulsion, promoting uniform cross-linking of the polysaccharides around the layer of charged groups, resulting in a consistent microcapsule structure. It may also help to keep the microcapsules formed separated and dispersed, preventing formation of large, undesirable aggregates. It may also help to control the size distribution of the microcapsules formed.

[0101] In some embodiments, the mixing is performed at a mixing speed of about 150 rpm to about 30000 rpm. In other embodiments, the speed may be about 150 rpm to about 25000 rpm, about 150 rpm to about 20000 rpm, about 150 rpm to about 15000 rpm, about 150 rpm to about 10000 rpm, about 150 rpm to about 5000 rpm, about 150 rpm to about 1000 rpm, about 1000 rpm to about 30000 rpm, about 1000 rpm to about 25000 rpm, about 1000 rpm to about 20000 rpm, about 1000 rpm to about 15000 rpm, about 1000 rpm to about 10000 rpm, about 1000 rpm to about 5000 rpm, about 5000 rpm to about 30000 rpm, about 5000 rpm to about 25000 rpm, about 5000 rpm to about 20000 rpm, about 5000 rpm to about 15000 rpm, about 5000 rpm to about 10000 rpm, about 10000 rpm to about 30000 rpm, about 10000 rpm to about 25000 rpm, about 10000 rpm to about 20000 rpm, about 10000 rpm to about 15000 rpm, about 15000 rpm to about 30000 rpm, about 15000 rpm to about 25000 rpm, or about 15000 rpm to about 20000 rpm. In other embodiments, the speed is about 150 rpm to about 800 rpm, about 150 rpm to about 600 rpm, about 150 rpm to about 300 rpm, about 300 rpm to about 1000 rpm, about 300 rpm to about 800 rpm, about 300 rpm to about 600 rpm, about 600 rpm to about 1000 rpm, about 600 rpm to about 800 rpm or about 800 rpm to about 1000 rpm. In some embodiments, the mixing speed is about 350 rpm. In some embodiments, the mixing may be performed using an overhead stirrer or overhead mixer. In some embodiments, the mixing may be performed using a homogeniser. The homogeniser may be a high energy homogeniser. High shear forces applied during homogenisation may reduce the size of the oil droplets and thus the size of the microcapsules formed. The homogenisation may be performed continuously to maintain the homogeneous suspension. The homogenisation may be performed using an ultrasound homogeniser. An ultrasound homogeniser may use high frequency sound waves to break down and disperse particles in a liquid sample. The ultrasound homogeniser may have a mixing speed of up to about 100 kHz.

[0102] In some embodiments, the mixing speed is about 20 kHz to about 100 kHz. In other embodiments, the speed is about 20 kHz to about 80 kHz, about 20 kHz to about 50 kHz, about 20 kHz to about 40 kHz, about 40 kHz to about 100 kHz, about 40 kHz to about 80 kHz, about 40 kHz to about 50 kHz, about 50 kHz to about 100 kHz, or about 50 kHz to about 80 kHz.

[0103] In some embodiments, the method is conducted at ambient temperature. The ambient temperature may have a temperature range of about 10 °C to about 30 °C. Oils such as fragrant oils, essential oils, natural oils, and / or synthetic oils, may comprise volatile, heat-sensitive oil molecules. These compounds may be easily degraded or lost when exposed to elevated temperatures. Encapsulating the oils at ambient temperature may help to preserve the aroma and composition of the encapsulated oil. Heating the oils during the microcapsule formation may lead to a breakdown or alteration of the oil molecules, resulting in a loss of fragrance or potency. Formation at ambient temperature may avoid this thermal degradation, helping to maintain the integrity and quality of the encapsulated oil. By forming the microcapsules at ambient temperature, the sensitive nature of the oils, such as fragrant oils and / or essential oils, may be better preserved, leading to enhanced aroma, potency and stability of the microcapsules. This may be beneficial in the use of the microcapsules in personal care and home fragrances.

[0104] In some embodiments, the ambient temperature is a temperature of about 10 °C to about 30 °C. In other embodiments, the temperature is about 10 °C to about 28 °C, about 10 °C to about 25 °C, about 10 °C to about 20 °C, about 10 °C to about 15 °C, about 15 °C to about 30 °C, about 15 °C to about 28 °C, about 15 °C to about 25 °C, about 15 °C to about 20 °C, about 20 °C to about 30 °C, about 20 °C to about 28 °C, or about 20 °C to about 25 °C. The method may result in residual polysaccharide. Residual polysaccharide may be polysaccharide left in the emulsion after the formation of the microcapsules. The residual polysaccharide may form assemblies of oppositely charged polysaccharides. After step e), any free polysaccharide may be cross-linked with other polysaccharides, solid particles in the emulsion, or a microcapsule shell. The assemblies of oppositely charged polysaccharide may be irregularly shaped as opposed to the capsules which may be mostly spherical. The presence of residual polysaccharide may mean that a portion of the oil may not be effectively encapsulated and may be present in the continuous phase in the emulsion. The residual polysaccharide may affect the size of the microcapsules formed. The higher the encapsulation efficiency, the fewer assemblies of residual polysaccharide that may be found in the emulsion after the formation of the capsules.

[0105] In some embodiments, the method is characterised by a volume percentage of oil relative to the total volume used for forming microcapsules of about 4% to about 12%. In other embodiments, the volume percentage is about 4% to about 11%, about 4% to about 10%, about 4% to about 8%, about 4% to about 5%, about 5% to about 12%, about 5% to about 11%, about 5% to about 10%, about 5% to about 8%, about 8% to about 12%, about 8% to about 11%, about 8% to about 10%, about 10% to about 12%, about 10% to about 11%, or about 11% to about 12%. In some embodiments, the volume percentage is about 5% to about 10%.

[0106] In some embodiments, the method is characterised by an encapsulation efficiency of more than about 90%. In other embodiments, the efficiency is more than about 92%, more than about 94%, more than about 96%, or more than about 98%.

[0107] In some embodiments, the method is characterised by a microcapsule size of about 0.1 pm to about 20 pm. In other embodiments, the method is characterised by a microcapsule size of about 0.1 pm to about 20 pm, about 0.1 pm to about 15 pm, about 0.1 pm to about 10 pm, about 0.1 pm to about 5 pm, about 0.1 pm to about 1 pm, about 0.1 pm to about 0.5 pm, about 0.5 pm to about 20 pm, about 0.5 pm to about 15 pm, about 0.5 pm to about 10 pm, about 0.5 pm to about 5 pm, about 0.5 pm to about 1 pm, about 1 pm to about 20 pm, about 1 pm to about 15 pm, about 1 pm to about 10 pm, about 1 pm to about 5 pm, about 5 pm to about 100 pm, about 5 pm to about 20 pm, about 5 pm to about 15 pm, about 5 pm to about 10 pm, about 10 pm to about 20 pm, or about 10 pm to about 15 pm. In some embodiments, the method is characterised by a microcapsule size of about 0.1 pm to about 10 pm. In some embodiments, the microcapsules agglomerate to form aggregates. The aggregates may comprise an assembly of single microcapsules. The aggregate may be about 30 pm to about 100 pm (Figures lOj and 10k).

[0108] The present disclosure also concerns a microcapsule formed by the method as disclosed herein.

[0109] The present disclosure also concerns a microcapsule comprising a core and a shell, wherein the core comprises an oil; wherein the shell comprises: a) a layer of charged groups; b) a first layer of charged polysaccharide ionically attracted to the layer of charged groups, the first layer of charged polysaccharide having an opposite charge to the layer of charged groups; and c) optionally a further layer of charged polysaccharide ionically attracted to the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge to the first layer of charged polysaccharide; wherein the first layer of charged polysaccharide and the optional further layer of charged polysaccharide are cross-linked.

[0110] In some embodiments, the microcapsule is characterised by a shell thickness of about 20 nm to about 500 nm. In other embodiments, the shell thickness is about 20 nm to about 400 nm, about 20 nm to about 250 nm, about 20 nm to about 200 nm, about 20 nm to about 150 nm, about 20 nm to about 100 nm, about 20 nm to about 50 nm, about 50 nm to about 500 nm, about 50 nm to about 400 nm, about 50 nm to about 250 nm, about 50 nm to about 200 nm, about 50 nm to about 150 nm, about 50 nm to about 100 nm, about 100 nm to about 500 nm, about 100 nm to about 400 nm, about 100 nm to about 250 nm, about 100 nm to about 150 nm, about 150 nm to about 500 nm, about 150 nm to about 400 nm, about 150 nm to about 250 nm, about 150 nm to about 200 nm, about 200 nm to about 500 nm, about 200 nm to about 400 nm, about 200 nm to about 250 nm, about 250 nm to about 500 nm, or about 250 nm to about 400 nm.

[0111] In some embodiments, the microcapsule is characterised by a particle size of about 0.1 pm to about 20 pm. In other embodiments, the size is about 0.1 pm to about 20 pm, about 0.1 pm to about 15 pm, about 0.1 pm to about 10 pm, about 0.1 pm to about 5 pm, about 0.1 pm to about 1 pirn, about 0.1 pm to about 0.5 pirn, about 0.5 pim to about 20 pim, about 0.5 pim to about 15 pim, about 0.5 pim to about 10 pim, about 0.5 pim to about 5 pim, about 0.5 pim to about 1 pim, about 1 pim to about 20 pim, about 1 pim to about 15 pim, about 1 pim to about 10 pim, about 1 pim to about 5 pim, about 5 pirn to about 100 pirn, about 5 pim to about 20 pirn, about 5 pim to about 15 pirn, about 5 pim to about 10 pirn, about 10 pim to about 20 pirn, or about 10 pirn to about 15 pim. In some embodiments, the size is about 0.1 pim to about 10 pim.

[0112] In some embodiments, the microcapsule is characterised by a cross-linking density of about 70% to about 95%. In other embodiments, the cross-linking density is about 70% to about 90%, about 70% to about 85%, about 70% to about 80%, about 70% to about 75%, about 75% to about 95%, about 75% to about 90%, about 75% to about 85%, about 75% to about 80%, about 80% to about 95%, about 80% to about 90%, about 80% to about 85%, about 85% to about 95%, about 85% to about 90%, or about 90% to about 95%.

[0113] In some embodiments, the polysaccharide is selected from selected from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof.

[0114] The present disclosure also concerns a formulation, comprising microcapsules as disclosed herein.

[0115] In some embodiments, the formulation further comprises an excipient and / or a solvent.

[0116] The formulation may contain any suitable carriers, diluents or excipients. These include all conventional solvents, dispersion media, fillers, solid carriers, coatings, antifungal and antibacterial agents, dermal penetration agents, surfactants, isotonic and absorption agents and the like. Excipients include any and all solvents, dispersion media, inert diluents, or other liquid vehicles, dispersion or suspension aids, granulating agents, surface active agents, disintegrating agents, isotonic agents, thickening or emulsifying agents, preservatives, binding agents, lubricants, buffering agents, oils, and the like, as suited to the particular dosage form desired. Various excipients used in formulating pharmaceutical compositions and known techniques for the preparation thereof is disclosed in G. A. R. Remington : The Science and Practice of Pharmacy, 21st ed. (2006), Lippincott Williams & Wilkins. Except insofar as any conventional excipient is incompatible with a substance or its derivatives, such as by producing any undesirable biological effect or otherwise interacting in a deleterious manner with any other component(s) of the formulation, its use is contemplated to be within the scope of this disclosure.

[0117] Excipients such as colouring agents, coating agents, and perfuming agents can be present in the formulation, according to the judgment of the formulator.

[0118] The solvent may be an aqueous medium. The term 'aqueous medium' used herein refers to a water based solvent or solvent system, and which comprises of mainly water. Such solvents can be either polar or non-polar, and / or either protic or aprotic. Solvent systems refer to combinations of solvents which result in a final single phase. Both 'solvents' and 'solvent systems' can include, and are not limited to, pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, dioxane, chloroform, diethylether, dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, nitromethane, propylene carbonate, formic acid, butanol, isopropanol, propanol, ethanol, methanol, acetic acid, ethylene glycol, diethylene glycol or water. Water based solvent or solvent systems can also include dissolved ions, salts and molecules such as amino acids, proteins, sugars and phospholipids. Such salts may be, but not limited to, sodium chloride, potassium chloride, ammonium acetate, magnesium acetate, magnesium chloride, magnesium sulfate, potassium acetate, potassium chloride, sodium acetate, sodium citrate, zinc chloride, HEPES sodium, calcium chloride, ferric nitrate, sodium bicarbonate, potassium phosphate and sodium phosphate.

[0119] The formulation may be for use in various products such as personal care products. The formulation may also be for use as coatings.

[0120] Examples

[0121] Introduction

[0122] Essential and fragrant oils help supporting our mental well-being by reducing anxiety, depression, or improving quality of sleep, help supporting our bodies as healing aids, pain relief aids, skin conditioning, nourishing, and protection aids. They also help preserving garments and textiles. Hence, the oils are widely used in range of personal care and household products. However, the volatile components of the oils tend to disseminate fast, making the fragrance initially strong and wearing off rapidly. Direct application of the oils onto skin may result in unpleasant sensation of stickiness, greasy skin, or skin irritations. Hence, there is a need to ensure that the active components from oils are released gradually over longer period, and that the applied formulation results in overall pleasant customer experience. These can be achieved by encapsulation. Encapsulation systems that successfully enclose majority of hydrophobic substances, may not be suitable for fragrant hydrophobic substances. Fragrant and essential oils contain high concentration of volatile molecules of low molecular weight, like cinnamaldehyde (132.16 g / mol) in cinnamon oil, limonene (136.24 g / mol) present in many coniferous and broadleaved trees but commonly extracted from citrus peel waste, or jasmone (164.246 g / mol), abundant in jasmine flowers. Moreover, fragrance molecules are amphiphilic in nature. The above in combination with intrinsic porosity of the capsules shell, makes encapsulation of fragrances and their retention, a challenge.

[0123] The high performance of currently available products containing encapsulated oils comes with a high and environmentally unacceptable price. The capsules are made using synthetic polymers. The rinsed-off plastic microparticles do not undergo biodegradation but instead they accumulate in environment entering a food chain.

[0124] Examples of currently used materials are (highlighted):

[0125] • A patent describes polymeric shell-core capsules with diameter ranging from 5 to 250 pm, comprising "polyurea, polyamide, or hybrid polymers formed from a mixture of organic and inorganic monomers or oligomers", formed by an interfacial polymerisation technique.

[0126] • Another patent describes microcapsules comprising polyisocyanate, polyamine, and or a polyhydroxy formed by an interfacial polymerisation technique.

[0127] • Another patent describes core-shell microcapsules comprising polysiloxane, a polyisocyanate and a polyamine, where the shell forms by interfacial polymerization between -NCO groups from the polyisocyanate and the hydroxyl groups present in the functionalized polysiloxane. The invention is also concerned with personal care or fabric care products containing the microcapsules.

[0128] • Another patent describes microcapsules comprising polymers formed from melamine-formaldehyde or urea-formaldehyde condensates, as well as similar types of aminoplasts, for rinse-off personal care and cleaning products.

[0129] To address this problem in 2019 European Chemicals Agency (ECHA) proposed restriction on microplastics in products allowed on EU / EEA market. At the same time ECHA proposed restrictions on use of formaldehyde and siloxanes D4, D5 and D6 used in consumer care products to increase smooth and silky feeling. In response to the growing need of biodegradable and non-hazardous substitutes for the currently used synthetic materials, and in preparation for expected ECHA restrictions, environmentally friendly and scalable microencapsulation technology suitable for different types of oils, including fragrant and essential oils, was developed. The oils may be encapsulated in biodegradable polysaccharide-based systems, without use of organic solvents and toxic chemicals. The technology may use water responsibly and may not generate chemical waste that require specialized treatments. The microcapsules (also referred to as capsules herein) may be incorporated not only into liquid formulations of various products for personal use, but may be considered for other applications, like coatings. The principles of the technology are demonstrated on model, commercially available, fragrant and essential oils.

[0130] Materials and Methods

[0131] Lignin alkaline (L0082) was purchased from TCI; hexadecyltrimethylammonium bromide (CTABr, H5882-lkg), Thyme Oil (W306509-lkg-K), Orange oil (W282510-lkg- K), (R)-(+)-Limonene (W263303-lkg-K), Chitosan (Aldrich, 448877), sodium alginate, medium viscosity (A2023-250g), Gum Arabic from acacia tree (Sigma-Aldrich G9752- 500g), adipic acid dihydrazide (A0638-25G), sodium dodecyl sulphate (SDS, 436146- 100g), sodium hydroxide and hydrochloric acid were purchased from Sigma-Aldrich. PERF 12-11723 Fresh Boost V2 was from by Henkel. All chemicals were used as received.

[0132] Stock solutions used to prepare second-generation samples:

[0133] Preparation of lignin alkaline stock solution :

[0134] Lignin alkaline (LA) powder was dissolved in deionized (DI) water to prepare 51.199 [mg / ml] stock solution. This solution was stored in closed bottle, in dark cabinet at room temperature for further use.

[0135] Preparation of adipic acid dihydrazide stock solution:

[0136] Adipic acid dihydrazide (AAD) was dissolved DI water to prepare 99.84 [mg / ml] stock solution, and solution was stored for further use.

[0137] Preparation of chitosan stock solution :

[0138] Chitosan was dissolved in 2 % acetic acid to prepare 2 % w / v solution, and solution was stored for further use. Preparation of sodium alginate stock solution :

[0139] Sodium alginate of medium viscosity (SAMV) was dissolved in DI water to prepare 20.06 [mg / ml] stock solution, and solution was stored in a fridge for further use.

[0140] Preparation of CTABr stock solution:

[0141] Solution of 15 [mg / ml] of CTABr was prepared in DI water, and solution was stored for further use.

[0142] Preparation of SDS stock solution : Solution of 50 [mg / ml] of SDS was prepared in DI water, and solution was stored for further use.

[0143] Formation of capsules:

[0144] Four different essential and fragrant oils were encapsulated, namely: orange oil, thyme oil, (R)-(+)-limonene and PERF 12-11723 Fresh Boost V2. A schematic representation of the encapsulation process is shown in Figure 1, and examples of resulting capsules are shown in Figure 2. During encapsulation, the mixing was continuous, with mixing / homogenisation rates remaining unchanged during the process. To avoid overheating, the samples produced using ultrasound homogenizer were cooled in water bath (Lauda, Alpha) set to 15 °C, during homogenization. The samples produced with overhead mixer were produced without cooling, at room temperature.

[0145] The process of encapsulation of the oils required two steps. In the first step a single oil- in-water (O / W) emulsion was formed, followed by formation of polysaccharide-based capsule shell in the second step. The shell may comprise a single layer or multiple layers. The exact compositions of the capsules are shown in Tables 1-6.

[0146] The first-generation samples were produced as follows: (R)-(+)-limonene or orange oil or thyme oil and CTABr solution were mixed at 350 rpm (IKA Overhead Stirrer with Digital Display, RW20) for 10 min to form O / W emulsion. Next, the solution of shellforming polysaccharide (or its derivative) was slowly added. The homogenization continued for another 10 min, and the addition of the shell-forming ingredients continued under the same conditions until the shell of desired composition was formed. The technology has been demonstrated on single- and multi-layer capsules. Subsequently, the capsules were cross-linked with adipic acid dihydrazide stock solution at pH<4, adjusted by addition of IM HCI. After the addition of the cross-linker the sample was mixed for additional 10 min at 350 rpm. The thus prepared samples were left under gentle mixing (Ratek Roller Mixer, model BTR5-12V) for 1-4 hours. Preparation of second-generation samples as well as the encapsulation of PERF 12- 11723 Fresh Boost V2 followed a similar protocol but using ultrasound homogenizer with cooling system. First, oil and respective emulsifier solution were homogenized (Hielscher UP400St Ultrasonic Processor, power mode, power 200W) for 10 min with 5s on I 2s off intervals, to form O / W emulsion. Next, the solution of shell-forming polysaccharide (or its derivative) was slowly added. The homogenization continued for another 10 min, and the addition of the shell-forming ingredients continued under the same conditions until the shell of desired composition was formed. The technology has been demonstrated on single- and multi-layer capsules. Subsequently, the capsules were cross-linked with adipic acid dihydrazide stock solution at pH<4, adjusted by addition of IM HCI. After the addition of the cross-linker the sample was homogenised for additional 10 min. Several batches of alike compositions containing PERF 12-11723 Fresh Boost V2 were prepared to assess process reproducibility and capsules stability upon storage at room temperature prior their dispatch for assessment. After approximately 24 hrs from addition of cross-linker, 1 M NaOH was added to samples containing PERF 12-11723 Fresh Boost V2 to neutralize the pH.

[0147] Table 1. Composition of second-generation, triple-layer capsules containing model essential and fragrant oils comprising lignin alkaline (LA) as a main encapsulating material.

[0148] Table 2. Composition of second-generation, double-layer capsules containing model essential and fragrant oils comprising lignin alkaline (LA) as a main encapsulating material.

[0149] Table 3. Composition of second-generation, single-layer capsules containing model essential and fragrant oils comprising gum Arabic (GA) as a main encapsulating material.

[0150] Table 4. Composition of second-generation, triple-layer capsules containing model essential and fragrant oils comprising gum Arabic (GA) as a main encapsulating material. Table 5. Composition of second-generation, triple-layer capsules containing model essential and fragrant oils comprising sodium alginate (SAMV) as a main encapsulating material.

[0151] Table 6. Composition of samples containing PERF 12-11723 Fresh Boost V2 as an encapsulated material.

[0152] Where applicable, the capsules size distribution was measured using Malvern Zetasizer. Prior measurements, the stock suspension of capsules was diluted with DI water. The pH of the samples was not adjusted. The samples with visually observable oil release were not characterized further.

[0153] Encapsulation effectiveness, understood as amount of oil encapsulated during the process, was evaluated visually for presence of residual oil layer at the end of the encapsulation process as well as for presence of uncoated oil droplets using optical microscope.

[0154] Solid content analysis was performed using METTLER TOLEDO, Halogen Moisture Analyzer, at drying temperatures 50°C and 85 °C, respectively. Results and Discussion

[0155] Process of encapsulation of fragrant and essential oils was realized using low- and high- energy homogenization equipment, being overhead mixer and ultrasound homogenizer, respectively. High-energy homogenization process requires continuous sample cooling due to large amount of heat generated during the process, that may affect the oils. Therefore, a cooling was introduced when applicable. Capsules produced using low- energy process are referred to as "first-generation capsules", and capsules produced using high energy process are referred to as "second-generation capsules". The main differences between the two processes were encapsulation effectiveness, defined as part of oil phase encapsulated during the process, and size of the capsules. Encapsulation effectiveness was greater when high-energy homogenization method was used. Respective encapsulation effectiveness is summarized in Table 7 and Table 8. Additionally, Figures 3-8 illustrate differences in samples' appearance. The results show that not all polysaccharides are equally effective encapsulants of fragrant and essential oils.

[0156] Table 7. Comparison of encapsulation effectiveness in first generation capsules comprising different polysaccharides for three model fragrant and essential oils, "x" marks systems with released oil.

[0157] Table 8. Comparison of encapsulation effectiveness in second generation capsules comprising different polysaccharides for three model fragrant and essential oils, "x" marks systems with released oil. The most effective encapsulant in first-generation capsules was lignin alkaline, followed by sodium alginate. In second-generation capsules oil release was observed in singlelayered lignin alkaline capsules. Effectiveness of the encapsulation was improved by introduction of high energy homogenization method.

[0158] In both generations of capsules, the effect of encapsulated oil type was observable for each capsule's composition, i.e., capsules comprising the same polysaccharides form suspensions of different properties. For example, second-generation capsules comprising gum Arabic (GA) loaded with thyme oil appear different than the same capsules loaded with orange oil or (R)-(+)-limonene (Figure 8). Similarly, second- generation capsules comprising lignin and chitosan (Figure 7), as well as GA and chitosan (Figure 8), loaded with (R)-(+)-limonene and orange oil separate from suspension more than capsules loaded with thyme oil. Spontaneous separation of capsules from suspension may be an additional benefit, considering recovery and further processing of the capsules. Second-generation of SAMV capsules with (R)-(+)-limonene (Figure 6) appear more hydrophobic and form well defined separate layer on top of aqueous phase. Separation of suspensions comprising the same capsules with thyme oil and orange oil is less defined. The aggregated SAMV capsules containing orange oil and (R)-(+)-limonene tend to accumulate at the walls of storage containers and may be difficult to disperse. For that reason, these capsules could have been analysed using light scattering methods. In contrary, the same capsules loaded with thyme oil form relatively stable suspensions. In such cases, depending on application, alternative shell compositions appear more suitable, for example, lignin or combination of lignin and chitosan (Table 8). It is noted that instability of capsules suspension does not imply instability of the capsules.

[0159] Stability of capsules against (partial) release of oil depends also mass ratio between cross-linker and shell material (C / S). This is best illustrated in first-generation capsules, prepared with overhead mixer (Figures 3-5). Applying this low energy method, the most effective material was combination of LA and chitosan, that successfully encapsulated orange and (R)-(+)-limonene oils at C / S = 1.19 mg / mg. SAMV with C / S = 1.92 mg / mg, and LA alone, with C / S =1.92 and 3.23 mg / mg, respectively, failed to encapsulate effectively two out of three oils (see Table 7). In second-generation capsules the C / S ratio was fixed at C / S=2. This was sufficient to prevent oil release as observed in first- generation capsules. Based on the second-generation samples prepared as described above, a model commercial fragrance: PERF 12-11723 Fresh Boost V2, was encapsulated in capsules comprising LA and chitosan. These samples were prepared with three different C / S ratios, 1, 2, and 3, respectively, to evaluate effect of degree of cross-linking on the capsules' stability. At C / S = 1, suspension of capsules was fluid; at C / S =2 suspension of capsules became slightly thicker fluid and formed thick gel-like paste at C / S=3 indicating excess of the cross-linker, leading to formation of larger aggregates or networks of capsules. In all samples free oil was not observed, and preliminary release studies did not indicate significant difference in release rates.

[0160] The capsules are polydisperse in size. Second-generation capsules are smaller than the first-generation capsules, with majority having less than 10 pm in diameter. The size distributions as well as sample optical microscopy images are shown in Figure 10. For comparison, optical microscopy images of selected first-generation capsules are shown in Figure 11. Large size polydispersity may be potentially reduced by application of membrane emulsification.

[0161] Size distributions of batches of like capsules are similar, as illustrated with LA-based capsules containing PERF 12-11723 Fresh Boost V2, in Figure 12.

[0162] To further characterized the capsules, a solid content analysis was performed. As a standard protocol, the evaluation was done at 50 °C (Table 9). Additional evaluation at 85 °C was done for capsules loaded with PERF 12-11723 Fresh Boost V2 (shaded row in Table 9).

[0163] Table 9. Solid content analysis measured for second-generation samples, with no observable significant oil release. Drying temperature was 50 °C, except Sample 16 that was dried at 85 °C. Switch off condition was weight change of 1 mg / 140 s (equipment default).

[0164]

[0165] Solid content analysis results show that after drying the remaining amount of material is more than calculated amount of solids added to encapsulation reaction volume (last column in Table 9). This may be due to inhomogeneous capsules suspension, resulting from aggregation and / or creaming, as well as due to residual oil that did not evaporate at the set drying temperature. It is noted that the samples after drying still had a well- defined fragrance. The highest amounts of residue mass were recorded, for specific capsule composition, for encapsulated thyme oil as compared to orange oil and (R)-(+)- limonene. Capsules comprising GA appear to supress evaporation of oils to the same extent as the final dry content was very similar for all three model oils. With exception of LA / chitosan / LA capsules with thyme oil, capsules comprising GA had the highest dry content at 50 °C. Triple-layer shells, comprising GA / chitosan / GA appear less effective in suppression of oil evaporation than single-layer shell comprising GA only. This is contrary to observations in LA-based capsule, where multi-layer shells were more effective. This may be due to different gelling properties of GA and LA as well as the effect of chitosan on gelling of GA resulting in formation of more permeable barrier.

[0166] Advantages and applications

[0167] • Use of natural, abundant, biocompatible and biodegradable material that may replace synthetic additives in consumer care products.

[0168] • Capsules may be formed in simple and adaptable process, under mild conditions.

[0169] • Formulation of capsules may not require organic solvents or harmful materials (waste management).

[0170] • Capsules may be loaded with various fragrant oils; type of oil may affect the capsules size (Figure 2).

[0171] • The capsules may be used in personal care products as an alternative to capsules composed of synthetic materials, improving the biodegradability potential, and reducing risks of adverse effects on human body.

[0172] Conclusions and Outlook

[0173] A simple, yet effective method to encapsulate fragrant and essential oils, also comprising multiple components, in polysaccharides has been developed and demonstrated using four different fragrant and essential oils. Encapsulation yield depends on homogenization method and was higher when high-energy method (ultrasound homogenizer) was used. Composition and type of oil may affect encapsulation process. Therefore, a specific fragrant / essential oil may require process optimization with respect to homogenization conditions, choice of emulsifier as well as choice of the encapsulating material. A tuneable capsule shell composition allows addressing specific requirements with respect to further application of the capsules i.e., surface hydrophobicity required to incorporate the capsules into various formulations. In-depth understanding of surface properties warrants further studies. The technology offers environmentally friendly alternative to processes based on synthetic and harmful materials by using only natural encapsulation materials (polysaccharides), elimination of organic solvents, toxic crosslinkers, and using mild encapsulation conditions. Moreover, materials used for encapsulation may be derived from by-products of other industrial processes, e.g., lignin. The technology is versatile and may be applied to different fragrant and essential oils.

[0174] It will be appreciated that many further modifications and permutations of various aspects of the described embodiments are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.

[0175] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0176] Throughout this specification and the claims which follow, unless the context requires otherwise, the phrase "consisting essentially of", and variations such as "consists essentially of" will be understood to indicate that the recited element(s) is / are essential i.e. necessary elements of the invention. The phrase allows for the presence of other non-recited elements which do not materially affect the characteristics of the invention but excludes additional unspecified elements which would affect the basic and novel characteristics of the method defined.

[0177] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

Claims1. A method of forming a microcapsule, comprising : a) emulsifying an oil in an aqueous medium in the presence of an ionic surfactant to obtain an oil-in-water emulsion, the ionic surfactant is configured to form a layer of chargeable groups at an oil-water interface; b) homogenising a first chargeable polysaccharide or derivative thereof with the emulsion of step a), the first chargeable polysaccharide or derivative thereof is configured to form a first layer of charged polysaccharide on the layer of charged ionic surfactant groups, the first layer of charged polysaccharide having an opposite charge to the layer of charged ionic surfactant groups, c) optionally homogenising a further chargeable polysaccharide or derivative thereof with the emulsion of step b), the further chargeable polysaccharide or derivative thereof is configured to form a further layer of charged polysaccharide on the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge to the first layer of charged polysaccharide; d) optionally repeating step c); and e) cross-linking the first layer of charged polysaccharide and the optional further layer of charged polysaccharides with a cross-linker in order to form the microcapsule; wherein the first and second chargeable polysaccharide or derivative thereof is selected independently from lignin alkaline, chitosan, sodium alginate, gum Arabic and a combination thereof; and wherein the method is conducted at ambient temperature.

2. The method according to claim 1, wherein the emulsifying step (step a)) further comprises mixing.

3. The method according to claim 1 or 2, wherein the emulsion is characterised by a volume ratio of aqueous medium to oil of about 1 : 1 to about 15: 1.

4. The method according to any one of claims 1 to 3, wherein the emulsion is characterised by a mass ratio of ionic surfactant to oil of about 1 : 500 to about 1 : 5.

5. The method according to any one of claims 1 to 4, wherein the oil is selected from fragrant oils, essential oils, natural oils, synthetic oils, and a combination thereof.

6. The method according to any one of claims 1 to 5, wherein the oil is void of anorganic solvent.

7. The method according to any one of claims 1 to 6, wherein the oil is characterised by a molecular weight of about 100 g / mol to about 200 g / mol.

8. The method according to any one of claims 1 to 7, wherein the ionic surfactant is selected from, hexadecyltrimethylammonium bromide (CTAB), benzalkonium chloride (BAC), dimethyldioctadecylammonium bromide (DDAB), sodium dodecyl sulfate (SDS), sodium lauryl ether sulfate (SLES), ammonium lauryl sulfate (ALS), sodium lignosulfonate, gum Arabic, and a combination thereof.

9. The method according to any one of claims 1 to 8, wherein the homogenising step (step b) and / or step c)) is performed at a homogenising speed of about 150 rpm to about 30000 rpm, or at about 20 kHz to about 100 kHz.

10. The method according to any one of claims 1 to 9, wherein step d) is performed at least 1 time.

11. The method according to any one of claims 1 to 10, wherein the layer of charged polysaccharide is covalently cross-linked.

12. The method according to any one of claims 1 to 11, wherein the cross-linker is selected from glyoxal, transglutaminase, adipic acid dihydrazide, glutaraldehyde, epichlorohydrin, and acrylates.

13. The method according to any one of claims 1 to 12, wherein the method is characterised by a mass ratio of cross-linker to polysaccharide of about 1: 1 to about 3: 1.

14. The method according to any one of claims 1 to 13, wherein step e) further comprises adding a pH modulator.

15. The method according to claim 14, wherein the pH modulator is an acid.

16. The method according to claim 14 or 15, wherein the pH modulator is selected from hydrochloric acid, citric acid and acetic acid.

17. The method according to any one of claims 1 to 16, wherein cross-linking occurs at a pH of less than about 4.

18. The method according to any one of claims 1 to 17, wherein step e) further comprises mixing.

19. The method according to claim 18, wherein the mixing is performed at a mixing speed of about 150 rpm to about 30000 rpm, or at about 20 kHz to about 100 kHz.

20. The method according to any one of claims 1 to 19, wherein the temperature is about 10 °C to about 30 °C.

21. The method according to any one of claims 1 to 20, wherein the method is characterised by a volume percentage of oil relative to the total volume used for forming microcapsules is about 4% to about 12%22. The method according to any one of claims 1 to 21, wherein the method is characterised by an encapsulation efficiency of more than about 90%.

23. The method according to any one of claims 1 to 22, wherein the method is characterised by a microcapsule size of about 0.1 pm to about 20 pm.

24. A microcapsule formed by the method according to any one of claims 1 to 23.

25. A microcapsule comprising a core and a shell, wherein the core comprises an oil; wherein the shell comprises: a) a layer of charged groups; b) a first layer of charged polysaccharide ionically attracted to the layer of charged groups, the first layer of charged polysaccharide having an opposite charge to the layer of charged groups; and c) optionally a further layer of charged polysaccharide ionically attracted to the first layer of charged polysaccharide, the further layer of charged polysaccharide having an opposite charge to the first layer of charged polysaccharide; wherein the first layer of charged polysaccharide and the optional further layer of charged polysaccharide are cross-linked.

26. The microcapsule according to claim 25, wherein the microcapsule is characterised by a particle size of about 0.1 pm to about 20 pm.

27. The microcapsule according to claim 25 or 26, wherein the polysaccharide is selected from selected from lignin alkaline, chitosan, sodium alginate, gum Arabic or and a combination thereof.

28. A formulation, comprising microcapsules according to any one of claims 25 to 27.

Images