WO2023063882A9

WO2023063882A9 - A method of coating a gel particle and a coated gel particle

Info

Publication number: WO2023063882A9
Application number: PCT/SG2022/050710
Authority: WO
Inventors: Praveen Thoniyot; Wenguang Zhao
Original assignee: Agency For Science, Technology And Research
Priority date: 2021-10-14
Filing date: 2022-10-04
Publication date: 2023-07-06
Also published as: WO2023063882A3; WO2023063882A2

Abstract

There is provided a method of coating a gel particle, the method comprising heterocoagulating nanoparticles onto a gel microparticle to form a coating layer over the gel microparticle. Also provided is a coated gel particle comprising a gel microparticle; and a coating layer over the gel microparticle, wherein said coating layer comprises a heterocoagulated form of nanoparticles on the gel microparticle.

Description

A METHOD OF COATING A GEL PARTICLE AND A COATED GEL PARTICLE

TECHNICAL FIELD

The present disclosure relates broadly to a method of coating a gel particle and said coated gel particle.

BACKGROUND

Microencapsulation is a process that involves surrounding microparticles or micrometer sized droplets by a shell, coating, or embedding microparticles in a homogeneous or heterogeneous matrix, in order to obtain small core-shell capsule structures with enhanced properties. These enhanced properties provided by microencapsulation include being able to better protect the capsular contents from leaking out which may cause undesirable immunological reactions in biological systems; increasing the longevity of the actives in the formulation when in storage; improving the sensorial aspects such as taste masking or skin feel of the microparticles; and enhancing the efficacy of actives e.g. by allowing release of the actives on demand etc, depending on the intended application.

Thus, an effective encapsulation of water soluble actives or microorganisms such probiotics is very much desired by various industries including consumer care (cell based antiaging actives), agrochemicals (microorganisms for nitrogen fixing) and food and nutrition (probiotics, vitamins).

However, although there is currently a number of established techniques available for hydrophobic actives to be encapsulated, there are only a few methods that would be considered to be somewhat successful for encapsulating hydrophilic actives. These methods for encapsulating hydrophilic actives include spray drying, spray chilling, spray freeze drying, extrusion, electrospraying, layer- by-layer shell formation; fluidized bed drying; and other physicochemical techniques such as emulsification and coacervation. Despite the success of these methods is encapsulating hydrophilic actives, it should be noted that most of the time, the techniques mentioned above require energy intensive processes or multiple steps which can adversely affect scalability and sustainability.

Another alternative approach to the above techniques is the use of gelation (chemical or ionic gelation or extrusion) to immobilize the hydrophilic active in a gel network. Gelation of the ingredient in a matrix is an inexpensive encapsulation method. However, the gel capsules obtained are extremely porous, affect viability of the microorganism, and/or can result in the premature release of the actives.

In view of the above, there is a need to address or at least ameliorate the above-mentioned problems. In particular, there is a need to provide a versatile, efficient and scalable coating technique on gel particles that may increase the performance and stability of actives contained therein.

SUMMARY

According to one aspect, there is provided a method of coating a gel particle, the method comprising heterocoagulating nanoparticles onto a gel microparticle to form a coating layer over the gel microparticle.

In one embodiment, the gel microparticle is porous.

In one embodiment, heterocoagulating nanoparticles onto the gel microparticle comprises adding a dispersion of the gel microparticles to a dispersion of the nanoparticles.

In one embodiment, the dispersion of the gel microparticles and the dispersion of the nanoparticles are aqueous dispersions. In one embodiment, the dispersion of the gel microparticles comprises the surfactant in a concentration of from 0.1 % w/w to 10.0% w/w.

In one embodiment, the dispersion of nanoparticles comprises the surfactant in a concentration of from 0.1 % w/w to 10.0% w/w.

In one embodiment, the nanoparticles and gel microparticles are oppositely charged.

In one embodiment, heterocoagulating nanoparticles with the gel microparticle further comprises stirring a mixture of the gel microparticles and the nanoparticles that is obtained after adding the dispersion of the gel microparticles to the dispersion of the nanoparticles.

In one embodiment, the gel microparticle has a particle size of in the range of from 1 .0 pm to 500.0 pm.

In one embodiment, nanoparticles have a particle size of in the range of from 2.0 nm to 500.0 nm.

In one embodiment, the heterocoagulating step is carried out in the presence of a surfactant.

In one embodiment, the surfactant comprises a neutral/non-ionic surfactant selected from the group consisting of octylphenol polyethoxylated surfactants, octylphenoxypolyethoxyethanol surfactants, polyoxyethylene surfactants and combinations thereof.

In one embodiment, the gel microparticle is a hydrogel microparticle.

In one embodiment, the hydrogel microparticle encapsulates one or more hydrophilic cargo. In one embodiment, the nanoparticles are selected from the group consisting of poly(methyl methacrylate) (PMMA), poly(methyl methacrylate-co- butyl methacrylate (PMMA-BMA), poly(methyl methacrylate-co-methyl acrylate) (PM MAMA), poly(methyl methacrylate-co-ethyl acrylate) (PMMAEA), poly(methyl methacrylate-co-butyl acrylate) (PMMABA), poly-N-isopropyl acrylamide (PNIPAM), poly-methyl-methacrylate-co-poly-styrene-co-polyethyl-hexyl- acrylate-co-poly-acrylic acid, poly(caprolactone) (PCL), poly(valerolactone), poly(butyrolactone), polyurethane, polyamides, polyacrylates, poly(meth)acrylates, polymethacrylates, polystyrene, polyalkylene, polyacetates silica nanoparticles, zirconia nanoparticles, titania nanoparticles, carbon nanoparticles and combinations thereof.

In one embodiment, the step of heterocoagulating nanoparticles with the gel microparticle to form the coating layer is substantially devoid of an organic solvent.

According to another aspect, there is provided a coated gel particle comprising a gel microparticle; and a coating layer over the gel microparticle, wherein said coating layer comprises a heterocoagulated form of nanoparticles on the gel microparticle.

In one embodiment, the gel microparticle is a hydrogel microparticle.

In one embodiment, the coating layer comprises one or more of a poly(methyl methacrylate) (PMMA), poly(methyl methacrylate-co-butyl methacrylate (PMMA-BMA), poly(methyl methacrylate-co-methyl acrylate) (PMMAMA), poly(methyl methacrylate-co-ethyl acrylate) (PMMAEA), poly(methyl methacrylate-co-butyl acrylate) (PMMABA), poly-N-isopropyl acrylamide (PNIPAM), poly-methyl-methacrylate-co-poly-styrene-co-polyethyl-hexyl- acrylate-co-poly-acrylic acid, poly(caprolactone) (PCL), poly(valerolactone), poly(butyrolactone), polyurethane, polyamides, polyacrylates, poly(meth)acrylates, polymethacrylates, polystyrene, polyalkylene, polyacetates silica nanoparticles, zirconia nanoparticles, titania nanoparticles, carbon nanoparticles derivatives thereof or combinations thereof.

In one embodiment, the gel microparticle encapsulates one or more hydrophilic cargo.

DEFINITIONS

The term “biocompatible” as used herein broadly refers to a property of being compatible with biological systems or parts of the biological systems without substantially or significantly eliciting an adverse physiological response such as a toxic reaction, an immune reaction, an injury or the like. Such biological systems or parts include blood, cells, tissues, organs or the like.

The term "polymer" as used herein refers to a compound comprising repeating units and is created through a chemical process of polymerization or a compound obtained from nature which contains repeating units (e.g. natural latex particles). The units composing the polymer are typically derived from monomers and/or macromonomers. A polymer typically comprises repetition of a number of constitutional units.

The terms “monomer” or “macromonomer” as used herein refer to a chemical entity that may be covalently linked to one or more of such entities to form a polymer.

The term "bond" refers to a linkage between atoms in a compound or molecule. The bond may be a single bond, a double bond, or a triple bond.

The term "micro" as used herein is to be interpreted broadly to include dimensions from about 1 micron to about 1000 microns. The term "nano" as used herein is to be interpreted broadly to include dimensions less than about 1000 nm, less than about 500 nm, less than about 100 nm or less than about 50 nm.

The term “heterocoagulation” to be interpreted as the aggregation of differently sized structures as a result of the difference in individual Brownian motion. For example, smaller sized structures such as nanoparticles or polymers may aggregate onto larger structures such as microparticles during heterocoagulation.

The terms "coupled" or "connected" as used in this description are intended to cover both directly connected or connected through one or more intermediate means, unless otherwise stated.

The term "associated with", used herein when referring to two elements refers to a broad relationship between the two elements. The relationship includes, but is not limited to a physical, a chemical or a biological relationship. For example, when element A is associated with element B, elements A and B may be directly or indirectly attached to each other or element A may contain element B or vice versa.

The term "adjacent" used herein when referring to two elements refers to one element being in close proximity to another element and may be but is not limited to the elements contacting each other or may further include the elements being separated by one or more further elements disposed therebetween.

The term "and/or", e.g., "X and/or Y" is understood to mean either "X and Y" or "X or Y" and should be taken to provide explicit support for both meanings or for either meaning. Further, in the description herein, the word “substantially” whenever used is understood to include, but not restricted to, "entirely" or “completely” and the like. In addition, terms such as "comprising", "comprise", and the like whenever used, are intended to be non-restricting descriptive language in that they broadly include elements/components recited after such terms, in addition to other components not explicitly recited. For example, when “comprising” is used, reference to a “one” feature is also intended to be a reference to “at least one” of that feature. Terms such as “consisting”, “consist”, and the like, may in the appropriate context, be considered as a subset of terms such as "comprising", "comprise", and the like. Therefore, in embodiments disclosed herein using the terms such as "comprising", "comprise", and the like, it will be appreciated that these embodiments provide teaching for corresponding embodiments using terms such as “consisting”, “consist”, and the like. Further, terms such as "about", "approximately" and the like whenever used, typically means a reasonable variation, for example a variation of +/- 5% of the disclosed value, or a variance of 4% of the disclosed value, or a variance of 3% of the disclosed value, a variance of 2% of the disclosed value or a variance of 1 % of the disclosed value.

Furthermore, in the description herein, certain values may be disclosed in a range. The values showing the end points of a range are intended to illustrate a preferred range. Whenever a range has been described, it is intended that the range covers and teaches all possible sub-ranges as well as individual numerical values within that range. That is, the end points of a range should not be interpreted as inflexible limitations. For example, a description of a range of 1 % to 5% is intended to have specifically disclosed sub-ranges 1 % to 2%, 1 % to 3%, 1 % to 4%, 2% to 3% etc., as well as individually, values within that range such as 1 %, 2%, 3%, 4% and 5%. It is to be appreciated that the individual numerical values within the range also include integers, fractions and decimals. Furthermore, whenever a range has been described, it is also intended that the range covers and teaches values of up to 2 additional decimal places or significant figures (where appropriate) from the shown numerical end points. For example, a description of a range of 1 % to 5% is intended to have specifically disclosed the ranges 1.00% to 5.00% and also 1.0% to 5.0% and all their intermediate values (such as 1.01 %, 1.02% ... 4.98%, 4.99%, 5.00% and 1.1 %, 1.2% ... 4.8%, 4.9%, 5.0% etc.,) spanning the ranges. The intention of the above specific disclosure is applicable to any depth/breadth of a range.

Additionally, when describing some embodiments, the disclosure may have disclosed a method and/or process as a particular sequence of steps. However, unless otherwise required, it will be appreciated that the method or process should not be limited to the particular sequence of steps disclosed. Other sequences of steps may be possible. The particular order of the steps disclosed herein should not be construed as undue limitations. Unless otherwise required, a method and/or process disclosed herein should not be limited to the steps being carried out in the order written. The sequence of steps may be varied and still remain within the scope of the disclosure.

Furthermore, it will be appreciated that while the present disclosure provides embodiments having one or more of the features/characteristics discussed herein, one or more of these features/characteristics may also be disclaimed in other alternative embodiments and the present disclosure provides support for such disclaimers and these associated alternative embodiments.

DESCRIPTION OF EMBODIMENTS

Exemplary, non-limiting embodiments of a method of coating a gel particle, and said gel particle are disclosed hereinafter.

In various embodiments, there is provided a method of coating a gel particle, the method comprising heterocoagulating nanoparticles onto/with a gel microparticle to form a coating layer over the gel microparticle. The coated gel particle/microparticle may be in the form of a capsule or a microcapsule. Therefore, in various embodiments, the method may also relate to a method of producing or forming gel capsules. Advantageously, forming a capsule around a gel particle can provide longevity of immobilized materials in the inner gel core. For example, the method may be useful for encapsulation of hydrophilic actives and aqueous suspensions, which for example may include water soluble actives, cells, cell extracts, microorganisms and actives suspended in an aqueous phase of an inner gel core. Embodiments of the method disclosed herein offer a versatile approach where a variety of actives, organisms, gel materials and nanoparticles and/or latex can be used to obtain the final capsules.

In various embodiments, the method disclosed herein utilizes a single step to encapsulate/coat the gel particle. By applying the technique of heterocoagulation, the gel particle may be directly encapsulated/coated with a coating by nanoparticles without the need for complicated surface modification techniques or in situ chemical reactions involving various toxic reactants during the formation of the coating layer. For example, embodiments of the method disclosed herein are different from those that rely on chemical reactions to chemically modify the surface of the gel (e.g. to obtain a silica modified hydrogel surface) or involves the use of initiators for surface medication, which may undesirably affect any immobilized actives that are sensitive to free radicals (e.g., tri-n-butyl borane complexed with 3-methoxypropyl amine (TN BB -MO PA)).

Thus, various embodiments of the method disclosed herein utilize preformed gel microparticles and preformed nanoparticles for heterocoagulation. Advantageously, embodiments of the process disclosed herein are simple, efficient and scalable as compared to known processes which require in situ chemical reactions to directly modify the surface of a capsule or particle.

Furthermore, embodiments of the method disclosed herein advantageously allow for soft gel particles to be effectively coated in a simple and straightforward manner. It will be appreciated that successfully achieving a uniform coating and/or film formation on soft gel particles without collapse of the gel is by no means trivial. Such consideration would not have been as relevant for the coating of hard microcapsules (e.g. silica microcapsules etc). Thus, there is generally no strong expectation of success in adopting any known methods of coating hard microcapsules to coat soft gel particles. For example, applying the concept of coating a hard micrometer-sized particle (e.g. silica or hard polymer capsule containing hydrophobic actives) with latex particles (nanometer sized), to form a protective film may not be easily envisaged for coating gel particles that are soft. This is because many soft gel particles have a high-water content and do not have a clear solid boundary with a continuous medium (e.g. water), thus making the surface for coating ambiguous. Furthermore, the surface of such high- water content soft gel (e.g. hydrogel) is not understood to contain functional groups that can facilitate film formation to achieve stable surface modification. Moreover, gels typically also have huge micrometer size pores (e.g. 5-10 times larger than latex nanoparticles) in the structure that would become swollen in the continuous medium (e.g. water), which makes using nanoparticles as a possible coating element counter-intuitive. Accordingly, coating such a structure with latex nanoparticles is indeed not trivial and the applicability of embodiments of the methods to obtain excellent coating results on gel particles which are generally soft in nature is indeed surprising.

Thus, in various embodiments disclosed herein, the gel microparticle is substantially porous or porous. The pore size of the gel microparticle may be in the range of from about a few nanometers to tens of micrometres such as from about 10 nm to about 10,000 nm, from about 100 nm to about 8,000 nm, from about 200 nm to about 6,000 nm, from about 300 nm to about 5,000 nm, from about 400 nm to about 3,000 nm, from about 500 nm to about 1 ,000 nm, or from about 50 nm to about 1 ,000 nm. After heterocoagulation of the nanoparticles to form a coating layer, the pores of the gel microparticle may be substantially covered or blocked, thereby reducing undesirable leakage of cargo or contents (such as actives) from within the gel microparticle to the outside. Accordingly, the coating layer may be a shell of a capsule formed. Thus, the resulting gel microparticle or capsule may be substantially less porous than the initial gel microparticle after formation of the coating layer. It will be appreciated that porosity of the gel particles will depend on the polymer content and crosslinking present within the gel and thus the pore sizes can range from few nanometers to tens of micrometers depending on the factors above and type of materials.

In various embodiments, heterocoagulating nanoparticles with the gel microparticle comprises adding a dispersion of the gel microparticles to a dispersion of the nanoparticles. In other words, the gel microparticles may be introduced into a volume of nanoparticles dispersion and not vice versa such that gel microparticles “enter” into a sea of nanoparticles. Accordingly, the volume of nanoparticles remains largely unmoved whereas the gel microparticles are moved from one location (i.e. their original location) to another (i.e. the volume of nanoparticles). Advantageously, in various embodiments, adding the gel microparticles to the nanoparticles reduces the likelihood of coagulation as compared to adding nanoparticles to gel microparticles, the latter may result in coagulation (e.g., massive coagulation) and/or the entire system may precipitate. In various embodiments, adding a dispersion of the gel microparticles to a dispersion of the nanoparticles may comprise introducing a smaller volume of dispersion of the gel microparticles (e.g. in a piecemeal fashion such as dropwise) to a larger volume of dispersion of the nanoparticles.

The dispersion of the gel microparticles may be an aqueous or a water dispersion of gel microparticles. The dispersion of the nanoparticles may be an aqueous or a water dispersion of nanoparticles. In various embodiments, both the dispersions of gel microparticles and nanoparticles are aqueous or water dispersions. Thus, various embodiments of the methods disclosed herein are completely different from methods that require the gel to be present as a suspension in oil in order to carry out the surface modification. Advantageously, conducting the coating process in aqueous/water-based mediums is environmentally friendly and is a unique yet versatile alternative to surface modification using chemical techniques that typically utilize harsh or environmentally unfriendly chemicals. Accordingly, in various embodiments, the step of heterocoagulating nanoparticles with the gel microparticle to form the coating layer is substantially devoid of an organic solvent (e.g. to dissolve one or more reactants) or a reactant (surfactant not taken into account) e.g. that may be required for a chemical reaction to take place.

In various embodiments, the heterocoagulating step is carried out in the presence of a surfactant. Advantageously, the presence of a surface helps to stabilize the dispersion of the heterocoagulated gel particles and in some cases also aids in the formation of film formation e.g. a continuous coating layer over the gel microparticle. In various embodiments, the surfactant comprises a neutral/non-ionic surfactant selected from the group consisting of octylphenol polyethoxylated surfactants (e.g., all members of the Triton family including Triton™ X-100, Triton™ X-114 and Triton™ X-405), octylphenoxypolyethoxyethanol surfactant (e.g., IGEPAL® CA-630), polyoxyethylene surfactant (e.g., Brij® L23) and combinations thereof. In various embodiments, the neutral surfactants aids in stabilising the dispersion of the heterocoagulated microparticles without mass aggregation, while the continuous coating layer is formed with the opposite charged nanoparticles adsorbed to the gel microparticles.

The method may further comprises mixing a surfactant with the nanoparticles to form a surfactant-nanoparticles mixture prior to the heterocoagulating step. Accordingly, in various embodiments, the dispersion of nanoparticles comprises a surfactant. For example, the dispersion of the nanoparticles may comprise the surfactant in a concentration/amount (e.g. mass concentration) of from about 0.1 % w/w to about 10.0% w/w, from about 0.2% w/w to about 9.5% w/w, from about 0.3% w/w to about 9.0% w/w, from about 0.4% w/w to about 8.5% w/w, from about 0.5% w/w to about 8.0% w/w, from about 0.6% w/w to about 7.5% w/w, from about 0.7% w/w to about 7.0% w/w, from about 0.8% w/w to about 6.5% w/w, from about 0.9% w/w to about 6.0% w/w, from about 1.0% w/w to about 5.5% w/w, from about 1.5% w/w to about 5.0% w/w, from about 2.0% w/w to about 4.5% w/w, from about 2.5% w/w to about 4.0% w/w, or from about 3.0% w/w to about 3.5% w/w. Accordingly, in various embodiments the final concentration of the surfactant in the nanoparticle dispersion is within the concentration values listed above. In some embodiments, the surfactants are added to the dispersion in the above concentrations. In some embodiments, the concentration of the surfactant is similar or identical or very different to the concentration of the nanoparticles. For example, in some embodiments, 1 .0% w/w surfactant may be used with 5.0% w/w nanoparticles. In various embodiments, the surfactant comprises a neutral/non-ionic surfactant selected from the group consisting of octylphenol polyethoxylated surfactants (e.g., all members of the Triton family including Triton™ X-100, Triton™ X-114 and Triton™ X-405), octylphenoxypolyethoxyethanol surfactant (e.g., IGEPAL® CA-630), polyoxyethylene surfactant (e.g., Brij® L23) and combinations thereof.

The method may further comprises mixing a surfactant with the gel microparticles to form a surfactant-microparticles mixture prior to the heterocoagulating step. Accordingly, in various embodiments, the dispersion of gel microparticles comprises a surfactant. For example, the dispersion of the gel microparticles may comprise the surfactant in a concentration/amount (e.g. mass concentration^ from about 0.1 % w/w to about 10.0% w/w, from about 0.2% w/w to about 9.5% w/w, from about 0.3% w/w to about 9.0% w/w, from about 0.4% w/w to about 8.5% w/w, from about 0.5% w/w to about 8.0% w/w, from about 0.6% w/w to about 7.5% w/w, from about 0.7% w/w to about 7.0% w/w, from about 0.8% w/w to about 6.5% w/w, from about 0.9% w/w to about 6.0% w/w, from about 1.0% w/w to about 5.5% w/w, from about 1.5% w/w to about 5.0% w/w, from about 2.0% w/w to about 4.5% w/w, from about 2.5% w/w to about 4.0% w/w, or from about 3.0% w/w to about 3.5% w/w. Accordingly, in various embodiments the final concentration of the surfactant in the gel microparticle dispersion is within the concentration values listed above. In some embodiments, the surfactants are added to the dispersion in the above concentrations. In various embodiments, the surfactant comprises a neutral/non-ionic surfactant selected from the group consisting of octylphenol polyethoxylated surfactants (e.g., all members of the Triton family including Triton™ X-100, Triton™ X-114 and Triton™ X-405), octylphenoxypolyethoxyethanol surfactant (e.g., IGEPAL® CA-630), polyoxyethylene surfactant (e.g., Brij® L23) and combinations thereof.

In various embodiments, the gel microparticle has a particle size of from about 1.0 pm to about 500.0 pm, from about 2.0 pm to about 490.0 pm, from about 3.0 pm to about 480.0 pm, from about 4.0 pm to about 470.0 pm, from about 5.0 pm to about 460.0 pm, from about 6.0 pm to about 450.0 pm, from about 7.0 pm to about 440.0 pm, from about 8.0 pm to about 430.0 pm, from about 9.0 pm to about 420.0 pm, from about 10.0 pm to about 410.0 pm, from about 15.0 pm to about 400.0 pm, from about 20.0 pm to about 350.0 pm, from about 25.0 pm to about 300.0 pm, from about 30.0 pm to about 250.0 pm, from about 35.0 pm to about 200.0 pm, from about 40.0 pm to about 150.0 pm, from about 45.0 pm to about 100.0 pm, from about 50.0 pm to about 95.0 pm, from about 55.0 pm to about 90.0 pm, from about 60.0 pm to about 85.0 pm, from about 65.0 pm to about 80.0 pm, or from about 70.0 pm to about 75.0 pm.

Accordingly, embodiments of the method disclosed herein are different from methods which work with larger particles such as millimeter-sized (e.g., 1 to 5 mm) capsules (e.g. hydrogel capsules) as a host of different considerations need to be taken into account due to differences physical characteristics as a result of the size differences.

In various embodiments, the concentration of the gel microparticles (e.g. when in the dispersion) is from about 5% w/w to about 30% w/w, from about 6% w/w to about 28% w/w, from about 8% w/w to about 26% w/w, from about 10% w/w to about 26% w/w, from about 10% w/w to about 25% w/w, from about 11 % w/w to about 24% w/w, from about 12% w/w to about 23% w/w, from about 13% w/w to about 22% w/w, from about 14% w/w to about 21 % w/w, from about 10% w/w to about 20% w/w, or from about 15% w/w. In various embodiments, the concentration of the gel microparticles is of the above values before or prior to heterocoagulation. In various embodiments, the gel microparticle comprises a charged gel microparticle. The gel microparticle may be negatively charged or positively charged. It will be appreciated that various gel microparticles may be used in embodiments of the method disclosed herein for example when the gel microparticle is charged or contains charge(s) present on the surface of the microparticle. In various embodiments, the gel microparticle contains or has been modified to contain negative/positive charge(s). The gel microparticle may be gel capsule having a non-solid core (e.g. hollow) that is capable of carrying or being filled with cargoes or actives (e.g. water soluble active). The gel microparticle may have a soft outer shell i.e. gelatinous-like outer shell. The gel microparticle may be a hydrogel e.g. a soft hydrogel capsule. In various embodiments, the gel microparticle is porous or has a porous outer shell or surface prior to heterocoagulation. Accordingly, in various embodiments, the capsule obtained after the heterocoagulation step is less porous (lower porosity) or substantially non-porous relative to the gel microparticle present prior to the heterocoagulation step.

In various embodiments, the gel microparticle is a hydrogel microparticle. In various embodiments, the gel microparticle comprises polyethylene glycol (PEG), acrylate gel based microparticles, collagen-derived proteins/peptides (e.g., gelatin), carbohydrates, glycosaminoglycans or mucopolysaccharides (e.g., hyaluronic acid) and polysaccharides or a salt thereof (e.g., natural seaweed/algae/macroalgae-derived polysaccharide or a salt thereof selected from the group consisting of alginic acid or algin, alginate, agar, agarose, agaropectin, carrageenan and combinations thereof). Accordingly, the gel microparticle may be a gel particle based on or derived from one or more of the above components. For example, the gel microparticle may be an alginate gel microparticle, a hyaluronic acid gel microparticle, an acrylate gel based microparticle, PEG based gel microparticle, or gelatine gel microparticle.

In some embodiments, the method further comprises, prior to the heterocoagulating step, (a-i) a step of passing a solution of gel microparticle precursor, such as one containing polyethylene glycol (PEG), acrylate gel based microparticles, collagen-derived proteins/peptides, carbohydrates, glycosaminoglycans or mucopolysaccharides and/or polysaccharide or a salt thereof selected from the group consisting of alginic acid or algin, alginate, agar, agarose, agaropectin, carrageenan and combinations thereof, through a nozzle under pressure to obtain microdroplets of polyethylene glycol (PEG), acrylate gel based microparticles, collagen-derived proteins/peptides, carbohydrates, glycosaminoglycans or mucopolysaccharides and/or polysaccharide or a salt thereof selected from the group consisting of alginic acid or algin, alginate, agar, agarose, agaropectin, carrageenan and combinations thereof; (a-ii) a step of adding said microdroplets to a crosslinking solution; and (a-iii) a step of drying said microdroplets and/or allowing said microdroplets to harden in the crosslinking solution into a gel-like structure. The step of drying/allowing to harden may comprises ionic/ionotropic gelation and/or crosslinking. In various embodiments, gelation and/or crosslinking is achieved by exchange of ions. For example, when microdroplets of sodium alginate solution are dried or allowed to harden in the crosslinking solution containing calcium ions, the sodium ions in the microdroplets of sodium alginate are replaced by calcium ions to form a crosslinked gel-like structure. The crosslinking solution may comprise multivalent cations and optionally a surfactant. The multivalent cations may comprise divalent cations (such as Ca²⁺, Ba²⁺ and Sr²⁺) and the surfactant comprises polysorbate-type nonionic surfactants (such as polysorbate 20 (or TWEEN® 20) and polysorbate 80 (or TWEEN® 80). In various embodiments, different formation mechanism (e.g., microfluidics) may be adopted for different gel particles.

The method may further comprise (a-iv) a step of passing the mixture containing the gel microparticles through a filter to obtain gel microparticles in a desired size range; and (a-v) a step of washing the gel microparticles with aqueous medium (e.g., deionized water). In various embodiments, the step of washing may be repeated once, twice thrice or more as appropriate. In various embodiments, the capsule/gel microparticle obtained is substantially stable. For example, the capsules/gel microparticles do not aggregate and/or therefore may be stored in deionized water for further use.

In various embodiments, the gel microparticle encapsulates one or more cargoes. Accordingly, the method may further comprise a step of loading/encapsulating one or more cargoes into the gel microparticle. In various embodiments, the one or more cargoes may already be loaded into the gel microparticle at the time of forming the gel microparticles. For example, the one or more cargoes may be dissolved or suspended in the solvent or medium used for formation of the gel microparticle (e.g. step a-i above). The one or more cargoes may be hydrophilic. The one or more cargoes may comprise one of the following: hydrophilic/water-soluble/water-compatible actives, sensitive cells, cell extracts, live cells, proteins, organisms, micro-organisms such as probiotics, vitamins, bacteria (e.g., rhizobium), pharmaceutical formulations, personal care products, home care products, cosmetics (e.g. antiaging actives), nutraceuticals, agricultural and aqua cultural supplies, animal feed (e.g., fish feed) or combinations or mixtures or derivatives thereof. Advantageously, embodiments of the method disclosed herein have a high encapsulation efficiency (e.g., actives can be encapsulated in a sustained and/or long-lasting manner) and/or high scalability (e.g., production can be scaled up to kilograms or even tonnes at an industrial scale) and/or high versatility (e.g., can be used for a wide range of gels, actives, and latex materials).

The nanoparticles may have a size that is no less than about 500 times, no less than about 600 times, no less than about 700 times, no less than about 800 times, no less than about 900 times or no less than about 1000 times smaller than the microparticle. In various embodiments, the nanoparticle has a particle size of from about 2.0 nm to about 500.0 nm, from about 2.0 nm to about 450.0 nm, from about 2.0 nm to about 400.0 nm, from about 2.0 nm to about 350.0 nm, from about 2.0 nm to about 300.0 nm, from about 2.0 nm to about 250.0 nm, from about 2.0 nm to about 200.0 nm, from about 2.0 nm to about 150.0 nm, from about 2.0 nm to about 100.0 nm, from about 3.0 nm to about 99.0 nm, from about 4.0 nm to about 98.0 nm, from about 5.0 nm to about 97.0 nm, from about 6.0 nm to about 96.0 nm, from about 7.0 nm to about 95.0 nm, from about 8.0 nm to about 94.0 nm, from about 9.0 nm to about 93.0 nm, from about 10.0 nm to about 92.0 nm, from about 15.0 nm to about 91 .0 nm, from about 20.0 nm to about 90.0 nm, from about 25.0 nm to about 85.0 nm, from about 30.0 nm to about 80.0 nm, from about 35.0 nm to about 75.0 nm, from about 40.0 nm to about 70.0 nm, from about 45.0 nm to about 65.0 nm, from about 50.0 nm to about 60.0 nm, or about 55.0 nm. Therefore, in various embodiments, it will be appreciated that the disclosed method is different from methods that use regular butter milk proteins (RBMP) for heterocoagulation on gel particles. It will be appreciated that RBMP are usually micrometer sized aggregated structures and depositing such structures on gel surface is completely different from embodiments disclosed herein which comprise nanometer sized particle deposition via heterocoagulation.

In various embodiments, the nanoparticles comprise charged nanoparticles. The nanoparticles may be negatively charged or positively charged. It will be appreciated that various different nanoparticles may be used in embodiments of the method disclosed herein for example, when the nanoparticles may have different charges. In various embodiments, the nanoparticles contain or has been modified to contain negative/positive charge(s). For example, charged nanoparticles may be obtained by dissolving the nanoparticles (e.g., polymeric nanoparticles) in an organic solvent and making nanoemulsions using high energy (e.g., ultrasound, ultrasonic mixing, high sheer mixing etc.) in the presence of a surfactant (e.g., a charged surfactant) in water. Although it may be preferable in some embodiments for the nanoparticles to have opposite surface charge compared to the gel particles for the coating of nanoparticles to happen on the gel particles, it will be appreciated that this preference does not completely prohibit using the neutral nanoparticles for the heterocoagulation process. For example, neutral nanoparticles may first be modified to a charged particle by surfactant switching and then can be used for the coating of the oppositely charged gel particles. Accordingly, in some embodiments, the nanoparticles are neutral particles which may be further modified by a surfactant to become a charged particle prior to heterocoagulation onto the gel.

The nanoparticles may be selected from the group consisting of organic nanoparticles, inorganic nanoparticles and hybrid organic-inorganic nanoparticles (or mixtures of organic and inorganic nanoparticles).

The organic nanoparticles may comprise natural and synthetic nanoparticles. In various embodiments, the organic nanoparticles comprise cellulose nanoparticles, lignin nanoparticles, gelatin nanoparticles, natural latex nanoparticles or organic polymer latex nanoparticles such as poly(methyl methacrylate) (PMMA), poly(methyl methacrylate-co-butyl methacrylate (PMMA- BMA), poly(methyl methacrylate-co-methyl acrylate) (PM MAMA), poly(methyl methacrylate-co-ethyl acrylate) (PMMAEA), poly(methyl methacrylate-co-butyl acrylate) (PMMABA), poly-N-isopropyl acrylamide (PNIPAM), poly-methyl- methacrylate-co-poly-styrene-co-polyethyl-hexyl-acrylate-co-poly-acrylic acid, poly(caprolactone) (PCL), poly(valerolactone), poly(butyrolactone), polyurethane, polyamides, polyacrylates, poly(meth)acrylates, polymethacrylates, polystyrene, polyalkylene, polyacetates or combinations thereof.

The inorganic nanoparticles may comprise silica nanoparticles, zirconia nanoparticles, titania nanoparticles, carbon nanoparticles or combinations thereof. In various embodiments, the inorganic nanoparticles comprise pure inorganic nanoparticles. The carbon nanoparticles may be inorganic carbon compounds such as carbides, carbonates, cyanides, graphite, carbon dioxide and carbon monoxide.

The hybrid organic-inorganic nanoparticles may comprise organic nanoparticles (e.g., organic polymer latex nanoparticles) and inorganic nanoparticles (e.g., silica nanoparticles, zirconia nanoparticles, titania nanoparticles, carbon nanoparticles or combinations thereof). In various embodiments, the hybrid organic-inorganic nanoparticles comprise organic nanoparticles stabilized with inorganic nanoparticles. The inorganic nanoparticles may be present as stabilizing agents. For example, a hybrid organic-inorganic nanoparticle may be a latex particle that contains inorganic nanoparticles as stabilizing agents. In some embodiments, the hybrid organic-inorganic nanoparticles comprise PCL-silica nanoparticles.

In various embodiments, the concentration of the nanoparticles is from about 0.1 % w/w to about 10.0% w/w, from about 0.2% w/w 5 to about 9.5% w/w, from about 0.3% w/w to about 9.0% w/w, from about 0.4% w/w to about 8.5% w/w, from about 0.5% w/w to about 8.0% w/w, from about 0.6% w/w to about 7.5% w/w, from about 0.7% w/w to about 7.0% w/w, from about 0.8% w/w to about 6.5% w/w, from about 0.9% w/w to about 6.0% w/w, from about 1.0% w/w to about 5.5% w/w, from about 1.5% w/w to about 5.0% w/w, from about 2.0% w/w 10 to about 4.5% w/w, from about 2.5% w/w to about 4.0% w/w, or from about 3.0% w/w to about 3.5% w/w. In various embodiments, the concentration of the nanoparticles is of the above values prior to heterocoagulation.

In some embodiments, the method further comprises, prior to the heterocoagulating step, (b-i) a step of mixing organic nanoparticles with inorganic nanoparticles under/using high energy/power (e.g., ultrasound/ultrasonic mixing, high sheer mixing etc.) to form a dispersion/emulsion/nanoemulsion of hybrid organic-inorganic nanoparticles; and optionally (b-ii) a step of removing/evaporating solvent from the dispersion/emulsion/nanoemulsion of hybrid organic-inorganic nanoparticles to obtain hybrid organic-inorganic nanoparticles. The method may further comprise, prior to the mixing step, a step of adding organic nanoparticles to inorganic nanoparticles to form an organic- inorganic nanoparticles mixture. The organic nanoparticles may be prepared/mixed/present in a suitable solvent such as an organic solvent (e.g., dichloromethane, pentane, tetrahydrofuran, benzene, chloroform, diethyl ether, acetonitrile, hexane, petroleum ether, cyclohexane, heptane, ethyl acetate or combinations thereof). The inorganic nanoparticles may be present in the form of a colloidal solution. The colloidal solution may be prepared by mixing inorganic nanoparticles with aqueous medium (e.g., deionized water).

In some embodiments, the method further comprises, prior to the heterocoagulating step, (c-i) a step of mixing one or more polymers with a surfactant/emulsifier (e.g., charged surfactant/emulsifier) under/using high energy/power (e.g., ultrasound/ultrasonic mixing, high sheer mixing etc.) to form a dispersion/emulsion/nanoemulsion of organic polymer latex particles (e.g., charged organic polymer latex particles); optionally (c-ii) a step of removing/evaporating solvent from the dispersion/emulsion/nanoemulsion of organic polymer latex particles (e.g., charged organic polymer latex particles) to obtain organic polymer latex particles (e.g., charged organic polymer latex particles). The one or more polymers may be prepared/mixed/present in a suitable solvent such as an organic solvent (e.g., dichloromethane, pentane, tetrahydrofuran, benzene, chloroform, diethyl ether, acetonitrile, hexane, petroleum ether, cyclohexane, heptane, ethyl acetate or combinations thereof). The surfactant/emulsifier may be present in the form of a colloidal solution. The colloidal solution may be prepared by mixing surfactant/emulsifier with aqueous medium (e.g., deionized water). The step of mixing to form a dispersion/emulsion/nanoemulsion may comprise mixing over a time duration of at least about 1 minute, at least about 2 minutes, at least about 3 minutes, at least about 4 minutes, at least about 5 minutes, at least about 10 minutes, or at least about 15 minutes. The step of removing/evaporating solvent may comprise stirring the dispersion/emulsion/ nanoemulsion at a stirring rate in the range of from about 100 rpm to 500 rpm over a time duration of at least about 10 minutes, at least about 15 m inutes, at least 30 about 20 m inutes, at least about 25 m inutes, at least about 30 minutes, at least about 40 minutes, at least about 50 minutes, at least about 60 minutes, at least about 2 hours, at least about 3 hours, at least about 4 hours, at least about 5 hours, at least about 6 hours, at least about 12 hours, at least about 24 hours, at least about 36 hours, at least about 48 hours, at least about 60 hours, or at least about 72 hours. In some embodiments, the method further comprises, prior to the heterocoagulating step, (d-i) a step of mixing one or more monomers in the presence of an initiator and/or surfactant/emulsifier and/or a suitable solvent to form a stable dispersion/emulsion of organic polymer latex particles; and optionally (d-ii) a step of passing the dispersion/emulsion of organic polymer latex particles through a filter to obtain organic polymer latex nanoparticles in a desired size range. The step of mixing may comprise warming/heating the mixture to a temperature that is from about 40°C to about 100°C. The step of mixing may be performed in an inert atmosphere or in the absence of oxygen (e.g., dissolved oxygen). The initiator may comprise an anionic inhibitor or a cationic inhibitor (e.g., 2,2’-azobis (2-methylpropionamidine) dihydrochloride (AIBA) or 2,2’- azobis(N,N’-dimethyleneisobutyramidine) dihydrochloride (ADIBA)) and the solvent comprises aqueous medium (e.g., deionized water). The surfactant/emulsifier may comprise an anionic surfactant/emulsifier (e.g., sodium dodecyl sulfate (SDS)) or cationic surfactant/emulsifier (e.g., cetyl trimethyl ammonium bromide (CTAB)) and the solvent comprises organic solvent (e.g., dichloromethane, pentane, benzene, chloroform, diethyl ether, hexane, petroleum ether, cyclohexane, heptane, ethyl acetate or combinations thereof). In various embodiments, the surfactant/emulsifier is present in an aqueous medium (e.g., deionized water). It will be appreciated that various solvents that are substantially immiscible with aqueous medium may be used in embodiments of the method disclosed herein. The monomers may comprise methyl methacrylate (MMA), butyl methacrylate (BMA), methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), N-isopropyl acrylamide (NIPAM), styrene, ethylhexylacrylate, acrylic acid, caprolactone, valerolactone, butyrolactone, urethane, amides, acrylates, (meth)acrylates, methacrylates, alkenes, acetates and combinations thereof.

In various embodiments, the nanoparticles are formed by one of the following reactions: emulsion polymerization, pickering emulsion polymerization, mini emulsion polymerization and emulsion solvent evaporation. In various embodiments, the nanoparticles comprise natural latex or latex obtained from nature/natural sources.

In various embodiments, the heterocoagulating step is carried out in the presence of two different/opposite/opposing charges (e.g., one is a positive charge and the other is a negative charge). In various embodiments, the heterocoagulating step may be carried out in the presence of gel microparticles and nanoparticles having charges that are opposite to each other. A first charge may be associated with the gel microparticle and a second charge may be associated with the nanoparticles, the second charge having a polarity that is opposite to that of the first charge. For example, when the gel microparticle is positively charged, the nanoparticles used are negatively charged and when the gel microparticle is negatively charged, the nanoparticles used are positively charged. In some embodiments, the method further comprises modifying the surface of the gel microparticle to impart a charge that is opposite to that of the nanoparticles, prior to the heterocoagulation (e.g. when the gel microparticle has a neutral surface prior to surface modification). Thus, advantageously, embodiments of the method disclosed herein may be applied to various gels with synthetic latex or natural latex when the latex and gels are of opposite charges. In some embodiments, the gel microparticle may be neutral and stabilized by an ionic surfactant that is has an opposite charge to the latex or nanoparticles.

In various embodiments, heterocoagulating nanoparticles with the gel microparticle further comprises stirring a mixture of the gel microparticles and the nanoparticles that is obtained after adding the dispersion of the gel microparticles to the dispersion of the nanoparticles. The stirring may be at a stirring rate in the range of from about 100 rpm to about 500 rpm. It will be appreciated that the stirring rate is dependent on various parameters including batch size (or volume) and size of stirrer. For example, in some embodiments, stirring a larger volume (of mixture) with a larger stirrer size at a lower stirring rate will achieve a radial flow that is similar to that achieved by stirring a smaller volume (of mixture) with a smaller stirrer size at a higher stirring rate. In various embodiments, the heterocoagulating step comprises stirring the mixture for a time duration of about 1 minute, about 5 minutes, about 10 minutes, about 15 minutes, about 20 minutes, about 25 minutes or about 30 minutes.

In various embodiments, the heterocoagulating step comprises physical changes to the nanoparticles but does not comprise chemical changes to the nanoparticles. In various embodiments, the heterocoagulating step is substantially devoid of a polymerization reaction and/or use of monomers/chemical curing agents/cross-linkers.

The overall formation of the coating layer/film over the gel microparticle may comprise (1 ) heterocoagulating nanoparticles on the gel microparticle, followed by (2) forming a coating layer/film from the heterocoagulated nanoparticles obtained in (1 ). The (first) heterocoagulating step may comprise only physical interactions and/or the (second) subsequent step of forming a coating layer/film from the heterocoagulated nanoparticles obtained in step (1 ) comprises physical and/or chemical interactions.

For example, in some embodiments, the (second) subsequent step of forming a coating layer/film from the heterocoagulated nanoparticles may comprise chemical reactions/changes (e.g., chemical cross-linking, chemically/covalently attaching/conjugating/coupling/ anchoring/ grafting/functionalizing the nanoparticles or the gel microparticle or their surfaces thereof). In other embodiments, the (second) subsequent step of forming a coating layer/film from the heterocoagulated nanoparticles comprises physical reactions/changes (e.g., physical inter-mixing of polymer chains from latex particles).

In various embodiments where the coating layer/film is formed from the heterocoagulated nanoparticles via cross-linking, the nanoparticles used comprise latex nanoparticles that are capable of cross-linking or forming cross- links such as latex containing epoxy groups (e.g., glycidyl methacrylate) and latex containing amino groups etc. In various embodiments where the coating layer/film is formed from the heterocoagulated nanoparticles via mere physical inter-mixing of polymer chains from latex particles, the nanoparticles used comprise one of more different types of latex nanoparticles and optionally carried out in the presence of or exposure to one or more of following conditions/components: plasticizer, temperature or any other mechanism.

Thus, the overall formation of the coating layer/film may comprise physical/non-chemical interactions/changes and optionally chemical interaction/changes.

In various embodiments, the method disclosed herein is conducted as a one-pot direct synthesis process to form the coated capsule (e.g. heterocoagulated latex shell around the microgel core). The one-pot synthesis is performed in a one-step procedure having only one active step; or a two-step procedure, where one of the steps (e.g. second step) may be a passive step (e.g., the passive formation of the coating layer/film from the heterocoagulated particles). For example, preformed gel microparticle and/or preformed nanoparticles may be used to directly form the coating layer/film such that the gel surface is modified directly by the latex/emulsion particles. Advantageously, using preformed soft gel materials and preformed latex may provide a diverse platform for encapsulating gel microparticles in a simple and efficient manner. Accordingly, various embodiments of the method disclosed herein do not include steps for preparing the gel microparticle and nanoparticles and/or additional steps such as surface modification of the gel surface directly using chemical processes.

In various embodiments, the heterocoagulating step and/or the entire method is substantially devoid of an organic solvent or medium that is used for or participates in a chemical reaction (e.g. for which a chemical reaction takes place in). In various embodiments, the heterocoagulating step and/or the entire method is carried out using an aqueous medium such as deionized water as the primary medium. Advantageously, embodiments of the methods disclosed herein are safe and non-toxic to the environment as compared to methods which require the use of harsh and toxic chemicals and/or organic solvents.

The method may further comprise one or more post heterocoagulation steps. For example, the method may further comprise a step of purifying the capsule formed in the mixture to remove any impurities such as excess/free polymer particles. The step of purifying the capsule may comprise centrifuging the mixture, filtering the mixture, washing the mixture, creaming the mixture, allowing the mixture to settle and/or subsequently decanting the mixture etc. For example, the method may also further comprise a step of concentrating the mixture. In various embodiments, the step of washing may be repeated once, twice or thrice. The step of washing may comprise adding a washing medium (e.g. deionised water) to form a suspension containing the microparticles/capsules (e.g. aqueous suspension), concentrating the suspension containing the microparticles/capsules to obtain a concentrated suspension of capsules (e.g. in an aqueous medium to form an aqueous suspension) before diluting the suspension with additional washing medium. The method may also further comprise adding one or more stabilizing agents (e.g. to reduce/prevent coagulation/agglomeration/aggregation in the concentrated suspension of capsules for storage).

In some embodiments, there is provided a method of coating hydrogel microparticles such as alginate microparticles with polymeric nanoparticles, the method comprising (i) adding monomers to a cationic initiator in a polymerization reaction to obtain positively-charged polymeric nanoparticles; and (ii) adding hydrogel microparticles to the mixture, thereby obtaining coated hydrogel microparticles, wherein the monomers are selected from the group consisting of methyl methacrylate, butyl acrylate and butyl methacrylate. Such a method of heterocoagulation using a cationic initiator results in a positively charged latex polymer that subsequently complexes with the hydrogel particle. It will be appreciated that besides using cationic latex and anionic gel, it will also be possible to use cationic gels and anionic latex. In some embodiments, it will also be possible to use neutral gel particles that is stabilized by an ionic surfactant and an oppositely charged latex to coat the gel microparticle.

There is also provided a coated gel particle comprising a gel microparticle; and a coating layer over the gel microparticle, wherein said coating layer comprises a heterocoagulated form of nanoparticles on the gel microparticle. For example, the coated gel particle may be a capsule comprising a gel microparticle; and a coating layer over the gel microparticle, wherein said coating layer is formed from nanoparticles (e.g. formed from polymeric nanoparticles and coating layer may be selected from the group consisting of an organic polymer coating layer, an inorganic coating layer (e.g., inorganic polymer coating layer) and a hybrid organic-inorganic polymer coating layer). Advantageously, various embodiments of the capsule/coated gel microparticle are substantially stable. For example, the capsule/gel microparticles do not aggregate and/or therefore may be stored in deionized water for further use.

The gel microparticle may have one or more characteristics or properties as earlier described. In various embodiments, the gel microparticle is a hydrogel microparticle. In various embodiments, the gel microparticle has a particle size falling in the range of from about 1.0 pm to about 500.0 pm, from about 2.0 pm to about 490.0 pm, from about 3.0 pm to about 480.0 pm, from about 4.0 pm to about 470.0 pm, from about 5.0 pm to about 460.0 pm, from about 6.0 pm to about 450.0 pm, from about 7.0 pm to about 440.0 pm, from about 8.0 pm to about 430.0 pm, from about 9.0 pm to about 420.0 pm, from about 10.0 pm to about 410.0 pm, from about 15.0 pm to about 400.0 pm, from about 20.0 pm to about 350.0 pm, from about 25.0 pm to about 300.0 pm, from about 30.0 pm to about 250.0 pm, from about 35.0 pm to about 200.0 pm, from about 40.0 pm to about 150.0 pm, from about 45.0 pm to about 100.0 pm, from about 50.0 pm to about 95.0 pm, from about 55.0 pm to about 90.0 pm, from about 60.0 pm to about 85.0 pm, from about 65.0 pm to about 80.0 pm, or from about 70.0 pm to about 75.0 pm. The coating layer may have one or more characteristics or properties as earlier described. For example, the coating layer may be selected from the group consisting of an organic polymer coating layer, an inorganic coating layer (e.g., inorganic polymer coating layer) and a hybrid organic-inorganic polymer coating layer. The coating layer may comprise one or more of a poly(methyl methacrylate) (PMMA), poly(methyl methacrylate-co-butyl methacrylate (PMMA-BMA), poly(methyl methacrylate-co-methyl acrylate) (PM MAMA), poly(methyl methacrylate-co-ethyl acrylate) (PMMAEA), poly(methyl methacrylate-co-butyl acrylate) (PMMABA), poly-N-isopropyl acrylamide (PNIPAM), poly-methyl- methacrylate-co-poly-styrene-co-polyethyl-hexyl-acrylate-co-poly-acrylic acid, poly(caprolactone) (PCL), poly(valerolactone), poly(butyrolactone), polyurethane, polyamides, polyacrylates, poly(meth)acrylates, polymethacrylates, polystyrene, polyalkylene, polyacetates silica nanoparticles, zirconia nanoparticles, titania nanoparticles, carbon nanoparticles, derivatives thereof or combinations thereof. In various embodiments, the coatings are different from coatings that use/contain chitosan or poly-urea-formaldehyde (PUF) polymers and are therefore substantially devoid of such contents. In various embodiments, the coating layer is biodegradable. In various embodiments, the coating layer is a substantially continuous coating layer or film. For example, when soft polymer particles or polymer particles with higher % of non-ionic surfactant that is capable of softening the latex/polymer particles are used, a substantially continuous coating layer may be formed. In some embodiments, where hard inorganic particles (e.g. silica particles) are used, the layer may be made with discrete nanoparticles. Such layer of discrete nanoparticles can provide benefits of protection/encapsulation at high nanoparticle coverage.

In various embodiments, the capsule comprises a hydrophilic and/or porous core. In various embodiments, the capsule and/or gel microparticle encapsulates one or more hydrophilic cargo. The capsule may comprise one of the following actives loaded/encapsulated in a core of the capsule: hydrophilic/water-soluble/water-compatible and/or sensitive cells, cell extracts, live cells, proteins, organisms, micro-organisms such as probiotics, vitamins, bacteria (e.g., rhizobium), pharmaceutical formulations, personal care products, home care products, cosmetics (e.g. antiaging actives), nutraceuticals, agricultural and aqua cultural supplies, animal feed (e.g., fish feed) or combinations or mixtures or derivatives thereof.

In various embodiments, the capsule comprises one or more of the following properties: non-toxic, hypoallergenic, biocompatible, degradable, environmentally benign, chemically stable and physically stable. Therefore, in various embodiments, the capsules may be useful in an application selected from the group consisting of: coating, therapy, medicine, agriculture, catalyst, printing, film, fibre, cosmetics, cosmeceutical, consumer care, personal care, health care, stimuli-driven delivery, and combinations thereof.

In various embodiments, there is provided gel capsules comprising alginate microparticles coated by PMMA latex or PMMA-BA latex. Thus, in such embodiments, the gel capsule may be a microcapsule comprising a hydrogel microparticle in the form of an alginate microparticle wherein the microparticle is coated by polymeric nanoparticles selected from the group consisting of polymethyl methacrylate (PMMA) and polymethyl methacrylate-co-butyl acrylate (PMMA-BA).

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a schematic diagram showing film formation through heterocoagulation of nanoparticles with a gel particle containing actives in accordance with various embodiments disclosed herein.

FIG. 2 is a schematic diagram of an air brush arrangement used for gel particle formation in an example disclosed herein. FIG. 3 is a schematic diagram showing gel particle formation and encapsulation using heterocoagulation in an example disclosed herein.

FIG. 4 is a graph showing the size distribution of silica nanoparticles using master sizer in an example disclosed herein.

FIG. 5 is a graph showing the size distribution of calcium alginate gel particles using master sizer in an example disclosed herein.

FIG. 6 is a graph showing the size distribution of calcium alginate gel particles heterocoagulated with silica nanoparticles using master sizer in an example disclosed herein.

FIG. 7A is a scanning electron microscope (SEM) image of the calcium alginate gel particles in an example disclosed herein at 2,000X magnification.

FIG 7B is a SEM image of the calcium alginate gel particles of FIG. 7A at 20,000X magnification. A high degree of porosity of on the surface of the particles can be seen.

FIG. 8A is a scanning electron microscope (SEM) image of the calcium alginate gel particles in an example disclosed herein before heterocoagulation with silica.

FIG 8B is a SEM image of the calcium alginate gel particles after heterocoagulation with nano silica in an example disclosed herein after heterocoagulation with silica.

FIG. 9 are SEM images of positively charged latex particles prepared for heterocoagulation with alginate gel particles in accordance with some examples disclosed herein. The images in the top row are positively charged PMMA latex particles while the images in the bottom row are positively charged P(MMA-BA) latex particles.

FIG. 10A and FIG. 10B are representative SEM images of positively charged latex particles heterocoagulated to alginate gel particles and film formed on alginate gel particles in accordance with some examples disclosed herein. FIG. 10A shows the surface modification of alginate gel by PMMA latex in presence of T riton (5%) while FIG. 10B shows the surface modification of alginate gel by PMMA-BA latex in presence of Triton (1 %).

EXAMPLES

Example embodiments of the disclosure will be better understood and readily apparent to one of ordinary skill in the art from the following examples, tables and if applicable, in conjunction with the figures. It should be appreciated that other modifications related to structural, biological and/or chemical changes may be made without deviating from the scope of the invention. Example embodiments are not necessarily mutually exclusive as some may be combined with one or more embodiments to form new example embodiments. The example embodiments should not be construed as limiting the scope of the disclosure.

A simple process of coating a soft gel particle is illustrated in the following examples. In the following examples, it has been demonstrated that nanometersized particles (polymer, inorganics, and combinations) can be heterocoagulated onto micrometer-sized hydrogel suspensions leading to encapsulation of hydrophilic actives and aqueous suspensions. Forming a capsule around a gel particle will provide longevity of immobilized materials in the inner gel core. In addition to water soluble actives, the embodiments of the process disclosed herein will be ideal for encapsulation of cells, cell extracts, microorganisms and actives suspended in aqueous phase. The possibility to vary the components of the gel phase and material to be used as nanoparticles leads to a versatile technology for sustainable encapsulation in water. As an illustration, hydrogel is used as the gel microparticle to be coated in the following examples. Hydrogel is chosen as an example as hydrogels have been used in delivery of various actives including proteins, cells and nutrients. However, since hydrogel is a very porous structure, long term protection and controlled release of actives from hydrogel micro particles are difficult and there is a need for hydrogel microparticles to modulate release of actives and protect the content from the hydrogel’s environment. The following examples show that embodiments of the coating method disclosed herein are capable of effectively coating and encapsulating hydrogel microparticles with polymer latex and/or inorganic particles in a simple manner via the hetero-coagulation approach to provide additional protection to a gel particle.

FIG. 1 provides a general overview of the method 100 of film formation through heterocoagulation of nanoparticles with a gel particle containing actives detailed in the examples below. As shown in FIG. 1 , a hydrogel particle 102 containing actives 104 is provided. The hydrogel particle 102 is then added to nanosized particles 106 which heterocoagulate with the hydrogen particle 102. Thus, the surface of the hydrogel particle 102 is modified by physical interactions with the nanosized particles 106. The heterocoagulation of nanosized particles 106 and the hydrogel particle 102 eventually results in a coating film 108 being formed around the hydrogel particle. The actives in the hydrogel particle 106 is better protected from unwanted leakages from the coated hydrogel particle which may also be collectively considered as a capsule.

Materials and methods

Low viscosity alginic acid sodium salt from brown algae, methylacrylate, n-butyl methylacrylate, calcium chloride, cetyl trimethyl ammonium bromide, dichloromethane, TritonX-100, TWEEN® 20, LUDOX® SM, LUDOX® CL used were purchased from Merck, 2,2’-azobis (2-methylpropionamidine) dihydrochloride was purchased from TCI. Micro air brush was purchased in online handicraft store. SEM was recorded using FE-SEM JSM7900F. The sizes of the particles were analyzed with Malvern Mastersizer 2000 Particle Size Analyzer.

Example 1 : Gelation of Sodium Alginate Microparticles

Microparticles were obtained through the ionic gelation technique. Sodium alginate solution (1.5 g/100 mL) was prepared and dissolved overnight. Calcium chloride (CaCl2, 0.3 mol/L) with Tween-20 (1 g/100 mL) was prepared and stirred at 70rpm. With reference to FIG. 2, a micro-airbrush 202 was positioned at an angle of 22.5° to the horizontal with a distance of 30cm and operated with air pressure of 1 bar gauge pressure. 40m L of Sodium alginate solution was loaded into the micro-airbrush 202 and was sprayed onto a gently stirred CaCl2-Tween solution 204. The resulting microparticles were allowed to harden in the CaCl2- Tween-20 solution 204 for 30 min. The resulting microparticles were then filtered with 76um wire mesh to remove large aggregates and then washed two to three times with deionized water with filter paper to remove the unreacted calcium. The final suspension (50mL) was obtained. The microparticles may be stored in D.l water for future use.

Example 2: Synthesis of positively charged PMMA latex

Deionized water (80.0g) and methyl methacrylate (MMA, 20.0g) was heated to 70°C in the 150mL round bottom flask with stirring at 700rpm. Dissolved oxygen was removed by bubbling of nitrogen gas for 20min. (AIBA, 0.075g) was added. The reaction mixture was continued to be stirred at 70°C for 4hr. The final latex was filtered to remove any aggregates.

Example 3: Synthesis of positively charged P(MMA-BA) latex

Deionized water (95.0g) was heated to 70°C in the 150mL round bottom flask with stirring at 700rpm. Dissolved oxygen was removed by bubbling of nitrogen gas for 20min. 2,2’-azobis (2-methylpropionamidine) dihydrochloride, (AIBA, 0.0188g) was added. Methyl methacrylate (MMA, 3.0g), butyl acrylate (BA, 2.0g) premix was fed to the flask at 2.5mL/hr for 2hr. The reaction mixture was continued to be stirred at 70°C for another 4hr. The final latex was filtered to remove any aggregates.

Example 4: PCL latex with Silica nanoparticles

1.0%w/w silica colloidal solution was prepared by adding Ludox-SM (30%w/w, 0.803g) into D.l water (24.1 g). Polycaprolactone (PCL, 0.731 g) was dissolved in dichloromethane (DCM, 36.55g) and was then added to the prepared silica colloidal solution. The mixture was then subjected to high power ultrasonic for emulsification for 5min. The resulting emulsion was then stirred in a glass beaker at 200rpm overnight to evaporate the DCM to obtain PCL-silica nanoparticle. The PCL-silica nanoparticle obtained is a hybrid nanoparticle PCL latex (~200nm) stabilized by silica (<20nm). In some way, this particle is quite similar to the heterocoagulated gel particle itself (~20 micrometer particles stabilized by ~0.2micrometer latex) but at much smaller dimensions.

Example 5: Emulsification of PCL latex with CTAB

Cetyl Trimethyl Ammonium Bromide (CTAB, 0.25g) into D.l water (24.1 g). Polycaprolactone (PCL, 0.731 g) was dissolved in dichloromethane (DCM, 36.55g) and was then added to colloidal solution. The mixture was then subjected to high power ultrasonic for emulsification for 5min. The resulting emulsion was then stirred in a glass beaker at 200rpm overnight to evaporate the DCM.

Example 6: Heterocoaqulation of latex to alginate microparticles

Triton-Xi 00 (0.02g, 0.1 %w/w) was added to 5%w/w P(MMA-BMA) latex (20mL) while on another similar run, Triton-X100 (1 g, 5.0%w/w) was added to 5%w/w PMMA latex (20mL). The mixture was stirred for 10min. With reference to FIG. 3, the heterocoagulation process was carried out by adding 20mL of alginate microparticles mixture 302 (20%w/w gel microparticle, 0.1 %w/w Triton- Xi 00) to the latex mixture 304 at the stirring rate of 300rpm for 1 min. The combined mixture 306 was then stirred for another 10min. The mixture was then left for particles to settle in a 50m L tube. The combined mixture 306 was then washed 3 times with D.l water and centrifugation at WOOrpm for 5m in to remove excess latex. The final mixture 308 was filled with D.l water to make up 20mL in volume.

Example 7: Heterocoagulation of Silica nanoparticles to alginate microparticles

The heterocoagulation process was done by adding of alginate microparticles mixture (5.0mL) to the silica particles suspension (2.0mL, 30%). The size distribution of silica particles used were determined using light scattering and results are shown in FIG. 6. The combined mixture was shaken for 1 min and rested for 30min. The mixture was then washed 3 time with D.l water by centrifugation at WOOrpm for 5m in to remove excess silica nanoparticles. The final wash was filled with D.l water to make up 5mL in volume.

Results and Discussion

The size distribution of sodium alginate gel particles obtained in Example 1 were determined using light scattering and results are shown in FIG. 5. By adjusting the angle of the nozzle and air pressure sodium alginate particles below 50 pm could be obtained. The median diameter (D50) was around 30 pm and 90% of the particles in the distribution was below 70 pm (D90). The simple set up used currently could be used to generate varying particle size in the range of 10 pm to 100 pm by tuning the spray angle and air pressure.

An SEM image of the gel particles showed a collapsed structure demonstrating the structural instability under SEM conditions of high vacuum (FIG. 7A) and porous network nature of calcium alginate gel surface under higher magnification of 20,000X (FIG. 7B). This is normally expected at low alginate concentrations (1.5wt/vol% in the current case) and such low polymer concentration gels are ideal for encapsulating actives such as live cells, proteins, bacteria etc. In order to see whether heterocoagulation on the gel surface can be attempted, alginate micro particles mixture (5.0mL) were added to the silica particles suspension (2.0mL, 30%) containing positively charged silica nanoparticles. The final gel particles were obtained after the process described in Example 7. Surprisingly, non-collapsed SEM image of the gel particle can be obtained, indicating that silica nanoparticles are capable of reinforcing the surface of the gel particle and preventing the gel structure from collapsing completely (FIG. 8B).

Encouraged by these results above, the inventors set out to prepare different latex particles and proceeded with encapsulation of gel particles with latex. Hard cross-linked methyl methacrylate (MMA) latex and soft methyl methacrylate-co-butyl methacrylate (MMA-BMA) latex were prepared as described in Example 2 and Example 3. The SEM image of these latex particles are shown in FIG. 9.

Similar to the case of the Ludox-SM silica particles in Example 7, both polymers( PMMA, P(MMA-BMA) ) modified the gel surface efficiently and formed a smooth layer of polymer around the gel particles. (FIG. 10A and FIG. 10B) It was observed that the neutral surfactant used Triton played an important role in the film formation.

Above results shows that coating a hydrogel micro particle with polymer latex (or inorganic particles) can be achieved by heterocoagulation process.

Conclusion

To the best of the inventors’ knowledge, coating of a hydrogel microparticle with polymer latex (or inorganic/hybrid particles) has not been previously described since it is not expected for hydrogel surface as produced to undergo heterocoagulation and film formation with latex particles. The inventors have shown herein that it is possible to successfully coat a soft gel particle using a simple and straightforward method of heterocoagulation through their investigative work in controlling the addition of hydrogel to latex, removal of residual ions from the initial gel suspension, introduction of neutral stabilizing surfactant, modifying the charge on the latex particle etc.

Without being bound by theory, it is believed that the present technology can be used to encapsulate variety of hydrophilic actives for application in personal care, home care, agriculture, aquaculture and animal feed sector. If the food grade or pharma grade gel and polymer particles are used, the technology can also be expanded into numerous more applications in these areas as well.

Furthermore, it will be appreciated that the technology may be carried by using preformed nanoparticles (e.g. positively charged polymeric nanoparticles) and preform gel particles to carry out heterocoagulation to form a core-shell gel particle which increases the efficiency and scalability of the process. Indeed, the inventors have shown by way of examples the possibility of using and preformed latex particles (e.g. 200-600nm) to form a protective layer over preformed gel microcapsules (e.g. 10-100 micrometers). Coating gel particles within these dimensions using preformed gel particles and preformed latex particles is not trivial since gels have huge micrometer sized pores and channels which are much higher than the latex particles. The use of preformed particles is also advantageous in the sense that in situ chemical preparation of a coating layer is not required. Such in situ approaches are not suitable for gel capsules where free radical sensitives cells and actives are encapsulated. On the other hand, the approach of using a separate step for adding preformed polymer particles e.g. having a charge that is opposite to the gel is more versatile and can be used for a wide range of gels, actives, and latex materials. It will be appreciated by a person skilled in the art that other variations and/or modifications may be made to the embodiments disclosed herein without departing from the spirit or scope of the disclosure as broadly described. For example, in the description herein, features of different exemplary embodiments may be mixed, combined, interchanged, incorporated, adopted, modified, included etc. or the like across different exemplary embodiments. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Claims

39 CLAIMS

1 . A method of coating a gel particle, the method comprising: heterocoagulating nanoparticles onto a gel microparticle to form a coating layer over the gel microparticle.

2. The method of claim 1 , wherein the gel microparticle is porous.

3. The method of any one of the preceding claims, wherein heterocoagulating nanoparticles onto the gel microparticle comprises adding a dispersion of the gel microparticles to a dispersion of the nanoparticles.

4. The method of any one of the preceding claims, wherein the dispersion of the gel microparticles and the dispersion of the nanoparticles are aqueous dispersions.

5. The method of any one of the preceding claims, wherein the dispersion of the gel microparticles comprises the surfactant in a concentration of from 0.1 % w/w to 10.0% w/w.

6. The method of any one of the preceding claims, wherein the dispersion of nanoparticles comprises the surfactant in a concentration of from 0.1 % w/w to 10.0% w/w.

7. The method of any one of the preceding claims, wherein the nanoparticles and gel microparticles are oppositely charged.

8. The method of any one of the preceding claims, wherein heterocoagulating nanoparticles with the gel microparticle further comprises stirring a mixture of the gel microparticles and the nanoparticles that is obtained after adding the dispersion of the gel microparticles to the dispersion of the nanoparticles. 40

9. The method of any one of the preceding claims, wherein the gel microparticle has a particle size of in the range of from 1 .0 pm to 500.0 pm.

10. The method of any one of the preceding claims, wherein the nanoparticles have a particle size of in the range of from 2.0 nm to 500.0 nm.

11 . The method of claim 1 , wherein the heterocoagulating step is carried out in the presence of a surfactant.

12. The method of claim 1 or 2, wherein the surfactant comprises a neutral/non- ionic surfactant selected from the group consisting of octylphenol polyethoxylated surfactants, octylphenoxypolyethoxyethanol surfactants, polyoxyethylene surfactants and combinations thereof.

13. The method of any one of the preceding claims, wherein the gel microparticle is a hydrogel microparticle.

14. The method of any one of the preceding claims, wherein the hydrogel microparticle encapsulates one or more hydrophilic cargo.

15. The method of any one of the preceding claims, wherein the nanoparticles are selected from the group consisting of poly(methyl methacrylate) (PMMA), poly(methyl methacrylate-co-butyl methacrylate (PMMA-BMA), poly(methyl methacrylate-co-m ethyl acrylate) (PM MAMA), poly(methyl methacrylate-co-ethyl acrylate) (PMMAEA), poly(methyl methacrylate-co- butyl acrylate) (PMMABA), poly-N-isopropyl acrylamide (PNIPAM), poly- methyl-methacrylate-co-poly-styrene-co-polyethyl-hexyl-acrylate-co-poly- acrylic acid, poly(caprolactone) (PCL), poly(valerolactone), poly(butyrolactone), polyurethane, polyamides, polyacrylates, poly(meth)acrylates, polymethacrylates, polystyrene, polyalkylene, polyacetates silica nanoparticles, zirconia nanoparticles, titania nanoparticles, carbon nanoparticles and combinations thereof. 41 The method of any one of the preceding claims, wherein the step of heterocoagulating nanoparticles with the gel microparticle to form the coating layer is substantially devoid of an organic solvent. A coated gel particle comprising: a gel microparticle; and a coating layer over the gel microparticle, wherein said coating layer comprises a heterocoagulated form of nanoparticles on the gel microparticle. The coated particle of any one of the preceding claims, wherein the gel microparticle is a hydrogel microparticle. The coated particle of any one of the preceding claims, wherein the coating layer comprises one or more of a poly(methyl methacrylate) (PMMA), poly(methyl methacrylate-co-butyl methacrylate (PMMA-BMA), poly(methyl methacrylate-co-m ethyl acrylate) (PM MAMA), poly(methyl methacrylate-co- ethyl acrylate) (PMMAEA), poly(methyl methacrylate-co-butyl acrylate) (PMMABA), poly-N-isopropyl acrylamide (PNIPAM), poly-methyl- methacrylate-co-poly-styrene-co-polyethyl-hexyl-acrylate-co-poly-acrylic acid, poly(caprolactone) (PCL), poly(valerolactone), poly(butyrolactone), polyurethane, polyamides, polyacrylates, poly(meth)acrylates, polymethacrylates, polystyrene, polyalkylene, polyacetates silica nanoparticles, zirconia nanoparticles, titania nanoparticles, carbon nanoparticles derivatives thereof or combinations thereof. The coated particle of any one of the preceding claims, wherein the gel microparticle encapsulates one or more hydrophilic cargo.