Field

The present invention relates to a composition comprising amorphous silica and filter media comprising said amorphous silica. The invention also relates to uses and methods of the amorphous silica and filter media in air filtration.

Background to the Invention

The word Silica relates to a group of minerals composed of silicon and oxygen, the two most abundant elements in the earth's crust. Silica can come in multiple forms and is found commonly in the crystalline state and rarely in an amorphous state. It is composed of one atom of silicon and two atoms of oxygen resulting in the chemical formula SiOz.

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular three dimensional framework of alternating silicon and oxygen atoms. The particles contain nanometer-scale voids and pores, which may contain water or some other liquids or may be filled by gas or vacuum. These porous silica particles have multiple uses, for example as catalysts, catalyst carriers, in filtration, and in chromatographic media etc.

The particles can be adapted to the different requirements of each application for example by altering pore size and characteristics, the mechanical strength and the binding properties.

Summary of the Invention

The present inventors have developed an amorphous silica having enhanced binding properties for proteins, microorganisms and/or pathogens, such as airborne proteins, microorganisms and/or pathogens. In particular, the amorphous silica may be used to bind airborne viruses such as coronaviruses which have an outer lipid membrane covered in spike proteins that give the distinctive ‘corona’ like appearance. The present invention, for the first time, uses the protein affinity of silica for the efficient capture of protein-containing microorganisms and pathogens. The surface properties of amorphous silica, which is an oxide adsorbent, depend on the presence of silanol groups. The OH groups act as the centres of molecular adsorption during their specific interaction with adsorbates capable of forming a hydrogen bond with the OH groups. It has surprisingly been found that silica with an optimised silanol and group I metal content can effectively bind and remove proteins, microorganisms and pathogens from air. As such, the present amorphous silica has a number of useful applications in filter media within face masks and air purifier systems and can effectively remove airborne pathogens. A first aspect provides a composition comprising amorphous silica having a Group I metal content of 500 to 2500ppm and having 2 to 7.6 silanol groups per nm ² .

In one example, the amorphous silica is in a substantially spherical form, a core shell form or a solid form. In one example, the amorphous silica further comprises a reactive group suitable for attaching the amorphous silica onto a substrate. In one example, the reactive group suitable for attaching the amorphous silica to a substrate is an amine, preferably a quaternary amine group or other ligand. In one example, the amorphous silica comprises a surface area of 150 to 250 m ² /g and/or a D50 particle size in a range from 5 to 100 pm. In one example, the amorphous silica comprises a pore size of 6 to 10 nm, and/or a pore volume of 0.2 to 0.6 mL/g. In one example, the composition further comprises a moisture indicator, preferably wherein the moisture indicator is cobalt chloride.

A second aspect provides a filter medium comprising a substrate and the composition according to the first aspect attached thereto.

In one example, the substrate comprises and/or is a fibrous material and/or a 3-dimensional scaffold which is negatively charged, optionally wherein the fibrous material is woven or nonwoven and/or wherein the 3-dimensional scaffold comprises interconnected porosity. In one example, the filter medium further comprises a permeable layer which encases the composition according to the first aspect and the substrate to which the composition is attached.

A third aspect provides a kit comprising the filter medium according to the second aspect and a diagnostic test capable of detecting a protein and/or a microorganism and/or a pathogen.

A fourth aspect provides a kit comprising the filter medium according to the second aspect and a face covering, suitable for covering a subject’s mouth and nose.

A fifth aspect provides a face covering comprising the composition according to the first aspect or a filter medium according to the second aspect.

A sixth aspect provides a kit comprising the filter medium according to the second aspect, an air purifier system and optionally a UV light and/or a heater and/or a steam generator, and or cold plasma.

A seventh aspect relates to the use of the composition according to the first aspect in a filter medium. An eighth aspect relates to a method of providing a filter medium according to the second aspect comprising: attaching the composition according to the first aspect to a substrate to provide the filter medium.

In one example, the method further comprises encasing the filter medium within a material having a pore size of less than the particle size of the amorphous silica.

A ninth aspect relates to a method of removing airborne microorganisms and/or pathogens from air, the method comprising; exposing a composition according to the first aspect or a filter medium according toto the air, and allowing the airborne microorganisms to couple to the amorphous silica.

A tenth aspect relates to the use of the composition according to the first aspect or the filter of the second aspect, in removing airborne microorganisms and/or pathogens.

An eleventh aspect relates to a method of detecting airborne microorganisms and/or pathogens, the method comprising; exposing a composition according to the first aspect or a filter medium according to the second aspect to air and allowing the airborne microorganisms, pathogens and/or proteins associated with the airborne microorganisms and/or pathogens to couple to the amorphous silica; and detecting the presence of the microorganisms, pathogens and/or the proteins associated with the microorganisms and/or pathogens coupled to the amorphous silica.

A twelfth aspect provides the composition of the first aspect, or the filter medium of the second aspect, the kit of the fourth aspect or the face covering of the fifth aspect for use in the prevention of infection due to airborne microorganisms and/or pathogens.

Figures

Figure 1. Images of amorphous silica particles attached to cotton fibres, acquired using a Tescan S8000G scanning electron microscope. Figures 1A and B shows the amorphous silica particles attached to cotton fibres. Figures 1 C and D showed zoomed in imaged of the amorphous silica particles attached to cotton fibres. The silica particles were attached to the cotton fibres via a quaternary amine. Figure 1 D also shows the presence of a heat sensitive glue on the silica particles.

Figure 2. Images of cotton swabs to which the amorphous silica particles may be attached. Figure 3. Images of a face covering comprising a pocket into which the filter medium may be inserted.

Figure 4. Figure 4A shows images of room purifiers which may be used in combination with the filter medium. Figure 4 B shows the filter media which may be used in a room purifier.

Figure 5. Images of filter media suitable for use in room filters/purifiers.

Figure 6. Schematic of the experimental set-up used to determine the ability of the amorphous silica to bind airborne protein containing particles. The nebuliser was used to produce aerosolised protein which flowed through the filter medium containing the amorphous silica or a control filter medium by means of a vacuum. Any particles which were not bound by the filter medium containing the amorphous silica or a control filter medium were absorbed onto a syringe filter placed behind the filter medium containing the amorphous silica or control filter medium.

Figure 7. Figure 7 A shows the concentration of aerosolised BSA in ppm which passed through the silica containing filter medium and the control (blank) mask. Figure 7B shows the average m/z = 848 ion count (x10 ^A 5) of aerosolised myoglobin which passed through the silica containing filter medium and the control (blank) filter medium. Figure 7C shows the average m/z = 874 ion count (x10 ^A 5) of aerosolised cytochrome C which passed through the silica containing filter medium and the control (blank) filter medium.

Figure 8. Figure 8A shows the average m/z = 848 ion count (x10 ^A 5) aerosol sample which passed through the which passed through the silica containing filter medium and the control (blank) filter medium. Figure 8B shows the average highest abundance peak ion count (x10 ^A 4) of the aerosol sample which passed through the silica containing filter medium and the control (blank) filter medium.

Figure 9. Figure 9A shows a size comparison of particles generally filtered by masks, coronavirus, Bacillus, PM2.5, red blood cell, and PM10. Figure 9B shows a schematic of a coronavirus which have a large single positive RNA stranded genome of 28-32 kilobase size (making it the largest RNA genome of the RNA virus family) enclosed in a nucleocapsid of helical symmetry These viruses infect human cells via S (spike) protein binding to receptors on host cells, followed by release of viral RNA into the cell cytoplasm. Various host receptors have been associated with the different human coronaviruses so far described: the host receptor for HCoV- 229E is aminopeptidase N while HCoV-OC43 uses 2,3 or 2,6 alpha sialic acid receptors (as does influenza virus). The S protein of SARS CoV binds to angiotensin converting enzyme 2 (ACE2) and of MERS CoV to dipeptidyl peptidase 4 (DPP4) ⁵ . SARS-CoV-2 has also been demonstrated to bind to ACE2, a transmembrane receptor which is widely expressed in lung, heart, kidney and gastrointestinal tissue.

Detailed Description of the Invention

According to the present invention there is provided a composition comprising amorphous silica, as set forth in the appended claims. Also provided is a filter medium comprising the amorphous silica along with kits, methods and uses of the composition comprising amorphous silica and the filter medium. Other features of the invention will be apparent from the dependent claims, and the description that follows.

Composition

The first aspect provides a composition comprising amorphous silica having a Group I metal content of 500 to 2500ppm and having 2 to 7.6 silanol groups per nm ² .

The term “amorphous silica” as used herein refers to a three-dimensional, inorganic polymeric silicon dioxide (SiOz) not having a crystalline structure as determined by x-ray diffraction. The amorphous silica may be acidic, for example having a pH of less than 7. The acidity of the silica may be achieved by the presence of a Group I metal or a mixture thereof. Group I metals include lithium, sodium, potassium, rubidium, caesium and francium. In one example, the amorphous silica comprises sodium and/or potassium. The Group I metal content may be between approximately 500 to 2500 ppm, or between approximately 750 to 2250 ppm, or between approximately 1000 to 2000 ppm, or between approximately 1250 to 1750 ppm, or between approximately 1400 to 1600 ppm, preferably the Group I metal content is approximately 1500 ppm. In contrast, the Group I metal content of amorphous silica for conventional applications, for example catalysts, catalyst carriers, conventional filtration, and chromatographic media, is typically reduced or minimized, for example below 100 ppm, as measured by inductively coupled plasma (ICP), such as inductively coupled plasma atomic emission spectroscopy (ICP-AES).

Methods for producing amorphous silica comprising a metal content are known in the art. For example silica particles may be produced via hydrolysis and condensation of metal alkoxides (Si(OR)4) such as tetraethylorthosilicate (TEOS, Si(OC2Hs)4) or inorganic salts such as sodium silicate (NazSiOs) in the presence of mineral acid (e.g., HCI) or base (e.g., NH3) as catalyst. The hydrolysis of TEOS molecules forms silanol groups. The condensation/polymerization between the silanol groups or between silanol groups and ethoxy groups creates siloxane bridges (Si- O-Si) that form the entire silica structure.

The amorphous silica comprises silanol groups. Without wishing to be bound by theory it is believed that the presence of the silanol groups and to a certain extent the presence of the Group I metal, such as sodium, generate a negative charge on the silica. This negative charge allows electrostatic interaction and binding of particles such as proteins, microorganisms and pathogens onto the silica. In particular viruses comprise nucleic acid encased in a protein coat as such the negative charge on the silanols can interact and bind the protein in the protein coat, effectively immobilising the virus on the silica. Bacteria also comprise numerous surface exposed proteins which are generally used for interaction between the bacterium and the host cell. As such the silanol groups can interact and bind these surface exposed proteins.

The amorphous silica comprises 2 to 7.6 silanol groups per nm ² , preferably there are 3 to 7.6 silanol groups per nm ² , or 4 to 7.6 silanol groups per nm ² , or 5 to 7.6 silanol groups per nm ² , or 6 to 7.6 silanol groups per nm ² . In order to increase the number of silanol groups acid washing of the silica may be performed. In contrast, the number of silanol groups per nm ² of amorphous silica for conventional applications, for example catalysts, catalyst carriers, conventional filtration, and chromatographic media, is typically reduced, for example below 2 silanol groups per nm ² , as measured by CP/MAS solid state NMR.

Silica is the preferred material for use in the present composition, however other negatively charged materials may also be used such as zeolites, silica aerogel, metal oxides and polyesters.

The amorphous silica may be used in a number of different forms for example; in a substantially spherical form, a core shell form or a solid form, as such the silica may be hollow or solid. Spherical silica particles may be less harmful, compared with silica particles having different morphologies, if accidentally inhaled as such, preferably the silica is in a substantially spherical form.

The composition may comprise other components for example a substrate to hold the silica. As such the amorphous silica may further comprise a reactive group suitable for attaching the amorphous silica onto a substrate. The reactive group may be an amine, preferably a quaternary amine group or other suitable ligand. Other suitable ligands includes reactive groups which can carry a charge. The term “quaternary amine group” refers to positively charged polyatomic ions comprising the structure NR ⁺ 4 wherein R is an alkyl group or an aryl group. In contrast to primary, secondary, or tertiary ammonium cations, quaternary amine groups are permanently charged irrespective of the pH. The quaternary amine group may be present within quaternary ammonium salt also known as “quats”. Suitable quaternary amine groups which may be used to attach the amorphous silica to the substrate include Hexadecyl ethyl dimethyl ammonium bromide, Tetradecyl trimethyl ammonium bromide, Hexadecyl trimethyl ammonium bromide, Octadecyl trimethyl ammonium chloride, Octadecyl trimethyl ammonium bromide, Dodecyl trimethyl ammonium bromide, Tetradecyl dimethyl benzyl ammonium chloride (Benzalkonium chloride), Hexadecyl dimethyl benzyl ammonium chloride, Tetradecyl dimethyl dichlorobenzyl ammonium chloride, 1 -Hexadecylpyridinium chloride (cetylpyridinium chloride).

The reactive group is attached to the silica such that it may form a bridge between the silica and the substrate. In particular a silane group may be used to attach the reactive group to the surface of the silica. The surface of the amorphous silica can be modified to introduce functional groups such as quaternary amine groups, amine groups, or other ligands. The surface modification may be performed via co-hydrolysis with tetraethylorthosilicate (TEOS) and various organosilane reagents. In the manner it is possible to introduce functional groups including quaternary amine, amine, carboxylate, amine/phosphonate, polyethylene glycol, octadecyl, and carboxylate/octadecyl groups.

Where an amine group is used to attach the silica to the substrate, control of the pH may be required in order to ensure the amine is in the positively charged state, for example the pH should be lower than the pKa of the amine group to ensure a positive charge. Where a quaternary amine group is used to attach the silica to the substrate this can be performed at any pH range as they are permanently charged independent of the pH.

The amorphous silica comprises a surface area of 150 to 250 m ² /g or 175 to 250 m ² /g, or 200 to 250 m ² /g as measured by nitrogen porosimetry. The D50 particle size of the amorphous silica may be in a range from 5 to 100 pm, or 10 to 95 pm, or 20 to 90 pm, or 30 to 85 pm, 40 to 80 pm, 45 to 75 pm, 50 to 70 pm, 55 to 65 pm. In one example, the D50 particle size of the amorphous silica is in a range of 40 to 60 pm. The particle size of the amorphous silica may be in a range from 5 to 100 pm, or 10 to 95 pm, or 20 to 90 pm, or 30 to 85 pm, 40 to 80 pm, 45 to 75 pm, 50 to 70 pm, 55 to 65 pm. In one example, the particle size of the amorphous silica is in a range of 40 to 60 pm. The particle size distribution may be measured by use of light scattering measurement of the particles in an apparatus such as a Malvern Mastersizer 3000, arranged to measure particle sizes from 10 nm to 3500 micrometres, with the particles wet-dispersed in a suitable carrier liquid (along with a suitable dispersant compatible with the particle surface chemistry and the chemical nature of the liquid) in accordance with the equipment manufacturer’s instructions and assuming that the particles are of uniform density. Where the amorphous silica is solid it may comprise a surface area of 1 to 5 m ² /g, or 2 to 4 m ² /g, or 3 m ² /g as measured by nitrogen porosimetry.

In one example, the amorphous silica is porous. The pore size may be in a range of 6 to 10 nm. The pore volume may be in a range of 0.2 to 0.6 mL/g as measured by nitrogen porosimetry.

Other components of the composition may comprise one or more of a moisture indicator, a pH indicator and/or an antimicrobial agent such as silver nanoparticles, gold nanoparticles, copper nanoparticles.

The moisture indicator may be cobalt chloride. The cobalt chloride may be incorporated into the composition by pre-washing the silica with cobalt chloride. When water is adsorbed onto the silica this reduces its binding efficacy, as such the presence of the moisture indicator may provide a visual indication that the composition is no longer working as effectively or that the composition needs regenerating. The amorphous silica may be regenerated by drying out the silica. This could be achieved by a heat source, a microwave source or a UV source. The UV source has the added benefit that it may help to kill/inactivate microorganisms and/or pathogens that have bound to the amorphous silica. Preferably the UV source comprises UV-C.

The composition may also comprise pH indicators such as phenolphthalein, methyl red, bromothymol blue etc.

An antimicrobial agent, such as nanoparticles thereof, may also be incorporated into the composition. Gold, silver and copper nanoparticles all have reported antimicrobial activity as such the presence of these particles may help to kill/inactivate microorganisms and/or pathogens that have bound to the amorphous silica. The composition may also be combined with substances such as paint, varnish, stains such that it may be applied to surfaces, such as walls or fabrics, including furnishings.

Filter Medium

The second aspect provides a filter medium comprising a substrate and the composition according to the first aspect attached thereto.

The substrate provides a structure that the composition comprising the amorphous silica is attached to. The amorphous silica may be directly attached to the substrate for example via a reactive group present on the surface of the silica, such as an amine, a quaternary amine or other suitable ligand. Where an amine or a quaternary amine is used for attachment it is preferred that the substrate carries a negative charge such that the negative charge of the substrate will interact with the positive charge of the amine or a quaternary amine.

The filter medium is intended to filter air as such the substrate may be permeable and may comprise gaps, pores or channels through which the air can pass through the filter medium. Alternatively, the air may be filtered by passing air over the filter medium rather than through the filter medium. In this case the substrate may not be permeable and may be solid.

The substrate may be a fibrous material and/or a 3-dimensional scaffold which carries a negative charge. The fibrous material may be woven or non-woven or a mixture thereof, and may include a naturally occurring material, for example cellulose fibres such as plant fibres from seed, leaf, bast, fruit and/or stalk and/or animal fibres and/or synthetic fibres. Seed fibres are collected from the seeds of various plants, for example cotton; leaf fibres are collected from the cells of leaves, for example, banana, pineapple (PALF); bast fibres are collected from the outer cell layers of a plant's stem, for example are flax, jute, kenaf, industrial hemp, ramie, rattan, and vine fibres; fruit fibres are collected from the fruit of the plant, for example, coconut fibre (coir) and stalk fibres are collected from the stalks of plants, for example straws of wheat, rice, barley, bamboo and straw. Animal fibres include hair, wool and silk. Synthetic fibres which may carry a negative charge include polyester, polystyrene, polyvinylidene chloride, polyurethane, polyethylene, polypropylene, polyvinyl chloride and polytetrafluoroethylene. The fibrous material may be woven to form a mesh structure. The 3-dimensional scaffold may comprise interconnected porosity such that air may pass through. The 3-dimensional scaffold may be a naturally occurring material such as a sponge or may be synthetic. Method for making synthetic fibrous and/or 3- dimensional scaffolds are known in the art for example using methods such as electrospinning. In one example, the substrate is a fabric such as cotton or polyester.

The substrate may be flexible and/or conformable in order to allow it to easily fit within filter devices. This flexibility and/or conformability also allows the filter medium to be used within face coverings and masks as it is easily insertable and the filter can adapt to face shapes. The substrate may also be cuttable such that bespoke filter medium shapes can be made, for example filter media can be produced with a shape that is compatible with commercially available air filters.

The amorphous silica may attach to the substrate via a reactive group. However other methods may also be used to attach the particles, for example using a heat sensitive glue. The glue may be used as an alternative to the reactive group or may also be used in combination with the reactive group. The heat sensitive glue is more suitable for attaching larger amorphous silica particles to the substrate, for example amorphous silica particles with a particle size D50 in the range of 30 to 100 pm, or 40 to 100 pm, or 50 to 100 pm, or 60 to 100 pm.

The filter medium may be provided with additional layers. The additional layers may have certain properties such as disinfectant, antimicrobial or biocidal properties. These layers may have similar permeability characteristics to the filter medium and they may be sandwiched between two layers of the substrate with the composition comprising the amorphous silica particles attached thereto. The disinfectant properties of the additional layer may help to kill/inactivate any bound microorganisms and/or pathogens. The disinfectant, antimicrobial or biocidal properties may be achieved by immobilising disinfectant, antimicrobial or biocidal compounds onto the additional layer.

The filter medium may further comprise a permeable layer which encases the composition comprising the amorphous silica and the substrate to which the composition is attached. This permeable layer comprises pores which allow air to pass through. It is preferred that the pores have a diameter which is smaller than the diameter of the amorphous silica particles. For example wherein silica particles with a particle size in the range of 5 to 100 pm are used, then the diameter of the pores should be less than 5 pm, or wherein silica particles with a particle size in the range of 40 to 60 pm are used, then the diameter of the pores should be less than 40 pm. Preferably a pore size of less than 40 pm, or less than 30 pm, or less than 20 pm or less than 10 pm is used. As such, in the event that any of the amorphous silica particles do not attach to the substrate, the permeable layer will prevent the free silica particles from escaping from the filter medium. When used within a face covering or mask this is a useful safety precaution to prevent inhalation on the silica particles.

The permeable layer may be made from fabric, such as muslin, cotton or cotton-polyester blends. Other fabrics are known.

The permeable layer encases the composition comprising the amorphous silica and the substrate to which the composition is attached. A variety of methods can be used to encase the composition and substrate, for example heat sealing, or pressure sealing using appropriate heat sensitive or pressure sensitive glue may be used.

The filter medium may also be provided in a non-permeable outer layer. This outer layer is designed to protect the filter medium prior to use. As such, a sterilised filter medium may be provided within the non-permeable outer layer. The outer layer is then removed prior to use.

The filter medium may be used in a variety of different air filter devices, face coverings, and bioaerosol samplers

Kits

The third aspect provides a kit comprising the filter medium according to the second aspect or the composition according to the first aspect and a diagnostic test capable of detecting a protein and/or a microorganism and/or pathogen. As used herein the term “microorganism” encompasses bacteria, archaea, protozoa, algae, fungi, viruses, and multicellular animal parasites such as helminths. As used herein the term “pathogen” encompasses infectious agents which cause disease including algae, bacteria, fungi, prions, viroids, viruses, and parasites such as protozoa or helminths. The diagnostic test may be used to detect virus, bacteria, fungus, protozoa, helminths, archaea, and/or prions. The diagnostic test may be used to detect airborne microorganisms, pathogens and/or proteins associated with airborne microorganisms and/or pathogens. Preferably the diagnostic test is used to detect bacteria, viruses and/or proteins specifically associated with bacteria and/or viruses. For example the diagnostic test may be designed to identify a surface exposed protein on a bacterium or virus. More preferably the diagnostic test is used to detect an airborne bacteria and/or viruses or proteins specifically associated with airborne bacteria and/or viruses. Examples of airborne bacteria and viruses include coronaviruses, influenza, parainfluenza, rhinoviruses, varicella zoster virus, mumps orthorubulavirus, rubeola virus, Mycobacterium tuberculosis, Corynebacterium diphtheriae, Bordetella pertussis.

The amorphous silica of the composition and filter medium is able to effectively bind proteins, microorganisms and pathogens present in the air. As such, these bound particles can subsequently be detected on the composition or on the filter medium. After composition or filter medium has been exposed to air, the composition or filter medium can be subjected to a diagnostic test to identify any bound proteins, microorganisms and/or pathogens.

The term “diagnostic test” refers to any test or technique that can be used to identify specific proteins, microorganisms and/pathogens, as such it encompasses different analytical tests such as antibody tests, ELISA, polymerase chain reaction, mass-spectrometry, SDS-PAGE.

Diagnostic/analytical tests are known within the art which can detect proteins, microorganisms and/or pathogens. In particular the diagnostic test may be used to detect airborne viruses such as Influenza, parainfluenza, rhinovirus, SarsCoV2, SarsCoV, MersCoV, Influenza type A H1 N1 , H5N1 , H9N2, varicella zoster virus, mumps orthorubulavirus, rubeola virus. The diagnostic test may identify proteins associated with these airborne viruses, for example to detect SarsCoV2, the diagnostic test may detection the spike protein. The spike protein is a viral membrane protein responsible for cell entry it binds to the receptor on the target cell and mediates subsequent virus-cell fusion. Detection of the spike protein would also be suitable for other coronaviruses.

Diagnostic/analytical tests to identify protein, microorganisms and/or pathogens are known within the art, these may comprise antibody tests, ELISA, polymerase chain reaction, mass- spectrometry, SDS-PAGE to identify bacterial or viral DNA, bacterial culture tests. In particular the diagnostic test may comprise and antibody test to identify the presence of the spike protein, in order to identify SarsCoV2 in the sample.

Prior to performing the diagnostic test the composition or filter medium may be subject to a processing step in order to remove the adsorbed protein, microorganisms and/or pathogens from the composition or filter medium. Desorption of the adsorbed material, such as protein microorganisms and/or pathogens, can be performed with a suitable eluent. This can also be achieved whilst preserving biological activity. Examples include, TMAC and various solvent combinations such as chloroform-methanol. Removal of the adsorbed material may be achieved by disrupting the binding interaction. This may be achieved by exposing the composition or filter media to trimethyl ammonium chloride. The kit according to the third aspect may be used in a variety of environments as the filter can be used in any suitable air purifier or ventilation system. As such the filter may be installed in work places, commercial buildings, hospital wards, home environments, animal housing such as cattle sheds. The filter can then be removed and tested using a diagnostic/analytical assay to identify protein, microorganisms and/or pathogens. The filter may be tested on site if suitable analytical techniques can be performed such as in a hospital or a lab or the filter may be sent to a testing centre for analysis for example if the filter was installed in a home or commercial property.

The fourth aspect provides a kit comprising the filter medium according to the second aspect and a face covering, suitable for covering a subject’s mouth and nose.

The term “face covering” refers to an item that covers the nose and/or mouth. It may encompass face masks such as surgical masks, masks suitable for use as personal protective equipment, reusable fabric face coverings or single use face coverings.

The filter medium may be provided separately from the face covering and inserted into the face covering prior to use. As such, the face covering should comprise a suitable pocket which the filter medium can fit within. The filter medium is preferably a suitable size such that it fits easily within the face covering but also fills a significant portion of the face covering in order that the majority of inhaled and exhaled air passes through the filter. As discussed above the filter medium may be provided in a non-permeable outer layer that is removed prior to use.

The fifth aspect provides a face covering comprising the composition according to the first aspect or a filter medium according to the second aspect.

As such the face covering may be designed to contain the composition comprising the amorphous silica particles. For example, cotton is a common material used in face covering and the composition may be directly attached to the cotton of the face covering. Alternatively, the face covering may encase the composition comprising the amorphous silica particles, in this case the face covering should be made of a material comprising pores which are smaller than the diameter of the silica particles, in order to prevent the silica particles escaping from the face covering. Alternatively, the face covering may comprise a pocket within which the filter medium fits.

The composition and/or the filter medium may also comprise a moisture indicator. This helps to provides a visual clue of when the composition and/or the filter medium has become wet and so it less effective at binding proteins, microorganisms and/or pathogens. This will indicate to the user that the filter should be replaced or regenerated using heat. A sixth aspect provides a kit comprising the filter medium according to the second aspect, an air purifier system and optionally a UV light and/or a heater, and/or steam generator and/or cold plasma.

The air purifier system may be any commercially available system, for example comprising an air conditioning unit, a HEPA filter, air cabin filters, vehicle filters including car, train, bus, coach filters. In this case the substrate used in the filter medium may not be permeable. Wherein the substrate of the filter medium is not permeable, the air is filtered by passing air over the surface of filter medium. In order to increase the adsorption of protein, microorganisms and/or pathogens devices that increase the turbidity of the air may be used and/or the filter medium disposed to increase turbidity for example by including serpentine channels. Alternatively, the substrate used in the filter medium is permeable and the air is filtered by passing air through the filter medium.

The air purifier and filter medium may optionally be provided with a UV source which can be used to kill/i nactivate any microorganisms/pathogens which are bound to the filter. Regular use of the UV source will reduce the chance of filter accidentally contaminating other surfaces or people when it is removed or replaced. Preferably the UV source comprises UV-C.

The kit may comprise other components to kill/inactivate any microorganisms/pathogens which are bound to the filter. Suitable components include heaters, steam generators and cold plasma.

The kit comprising the filter medium according to the second aspect and an air purifier system and the kit comprising a face covering and the filter medium according to the second aspect, may be used to reduce transmission of airborne microorganisms and/pathogens. They may be used in a variety of settings for example in crowded environments, hospital wards, commercial settings or work places where there may be infected subjects. As the kits result in the binding of airborne microorganisms and pathogens, including viruses, bacteria and fungi, they help to reduce the amount of microorganisms and pathogens circulating in the air and thereby reduce transmission.

Methods and Uses

The seventh aspect relates to the use of the composition according to the first aspect in a filter medium.

The eighth aspect relates to a method of providing a filter medium according to the second aspect comprising; attaching the composition according to the first aspect to a substrate to provide the filter medium.

As discussed above the attachment may be performed using a reactive group present on the surface of the amorphous silica particles, or other physical attachment means could be used such as heat sensitive adhesive.

The method may further comprise encasing the filter medium within a material having a pore size of less than the particle size of the amorphous silica. A variety of methods can be used to encase the filter medium, for example heat sealing, or pressure sealing using appropriate heat sensitive or pressure sensitive adhesive may be used.

The method may further comprise incorporating additional layers with disinfectant or antimicrobial properties. These layers may be incorporated by using a suitable adhesive.

The ninth aspect relates to a method of removing airborne microorganisms and/or pathogens from air, the method comprising; exposing a composition according to the first aspect or a filter medium according to the air, and allowing the airborne microorganisms and/or pathogens to couple to the amorphous silica.

The composition or the filter medium may be exposed to the air by passing air through or over the surface of the composition or filter medium. The air may be an air sample taken for analysis, or air which is in general circulation. The air may also be a breath sample obtained from a subject, or it may be air which is inhaled and exhaled by a person through the composition or filter medium. As the air passes through or over the composition or filter medium the airborne microorganisms and/or pathogens will couple to the amorphous silica via electrostatic interactions with the silanol groups. As such the airborne microorganisms and/or pathogens are removed from the air as they are bound to the amorphous silica.

Preferably the method removes airborne bacteria and/or viruses from the air. For example, the method may remove influenza, parainfluenza, rhinovirus, SarsCoV2, SarsCoV, MersCoV, Influenza type A H1 N1 , H5N1 , H9N2, varicella zoster virus, mumps orthorubulavirus, rubeola virus, Mycobacterium tuberculosis, Corynebacterium diphtheriae and/or Bordetella pertussis. Preferably the method removes coronaviruses including SarsCoV2, SarsCoV, MersCoV.

The tenth aspect relates to the use of the composition according to the first aspect or the filter of the second aspect, in removing airborne microorganisms and/or pathogens. The eleventh aspect relates to a method of detecting airborne microorganisms and/or pathogens, the method comprising; exposing a composition according to the first aspect or a filter medium according to the second aspect to air and allowing the airborne microorganisms, pathogens and/or proteins associated with the airborne microorganisms to couple to the amorphous silica; and detecting the presence of the microorganisms, pathogens and/or the proteins associated with the microorganisms and/or pathogens coupled to the amorphous silica.

Once the airborne microorganisms and/or pathogens are bound to the amorphous silica they can then be detected via standard diagnostic tests. These tests may involve PCR reactions to identify bacterial or viral genetic material, or bacterial culture tests, they may comprise antibody tests or ELISAs to identify proteins associated with the airborne microorganisms and/or pathogens, or a combination of these techniques. The proteins associated with the airborne microorganisms and/or pathogens may be surface expose proteins for example to detect a coronavirus such as Sars-CoV2 the test may detect the presence of the surface exposed spike protein.

The method may comprise a step of removing the bound microorganisms and/or pathogens from the amorphous silica. This may be achieved by disrupting the electrostatic interaction binding the microorganisms and/or pathogens to the amorphous silica. This may be achieved by exposing the composition or filter media to trimethyl ammonium chloride.

Preferably the diagnostic test identifies airborne bacteria, viruses and/or proteins associated with the airborne bacteria and/or viruses. In particular the test may detect influenza, parainfluenza, rhinovirus, SarsCoV2, SarsCoV, MersCoV, Influenza type A H1 N1 , H5N1 , H9N2, varicella zoster virus, mumps orthorubulavirus, rubeola virus, Mycobacterium tuberculosis, Corynebacterium diphtheriae and/or Bordetella pertussis. Preferably the method detects coronaviruses including SarsCoV2, SarsCoV, MersCoV.

The twelfth aspect provides the composition of the first aspect, or the filter medium of the second aspect, the kit of the fourth aspect or the face coveringof the fifth aspect for use in the prevention of infection due to airborne microorganisms and/or pathogens, or for use in the reduction of transmission of airborne microorganisms and/or pathogens.

Also provided is a method for preventing infection due to airborne microorganisms and/or pathogens comprising using the composition of the first aspect, or the filter medium of the second aspect, the kit of the fourth aspect or the face covering of the fifth aspect. Since the composition is able to effectively bind and subsequently remove harmful airborne microorganisms and/or pathogens this will help to prevent and/or reduce the incident of infection by such infective agents.

The composition comprising the amorphous silica is able to effectively bind airborne viruses and bacteria such as influenza, parainfluenza, rhinovirus, SarsCoV2, SarsCoV, MersCoV, Influenza type A H1 N1 , H5N1 , H9N2, varicella zoster virus, mumps orthorubulavirus, rubeola virus, Mycobacterium tuberculosis, Corynebacterium diphtheriae and/or Bordetella pertussis. These viruses and bacteria result in diseases such as influenza, common colds, Covid-19, SARS, MERS, bird flu, chickenpox, mumps, measles, tuberculosis, diptheria, whooping cough. All of these diseases can be transmitted by airborne transmission. As such by using the compositions and filter medium comprising the amorphous silica particles these infective agents can be effectively removed from air circulation and thereby reduce the chances of airborne transmission and effectively prevent subsequent infections from occurring. Preferably the method reduces transmission of coronaviruses including SarsCoV2, SarsCoV, MersCoV.

Definitions

Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of” or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention, such as colourants, and the like.

The term “consisting of” or “consists of” means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of” or “consisting essentially of”, and also may also be taken to include the meaning “consists of” or “consisting of”.

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.

EXAMPLES

EXAMPLE 1 - Binding of airborne proteins by filter media containing amorphous silica particles.

Myoglobin (0.01 g, 5.9 x10 ^-7 mol) was dissolved in 10 mL of distilled water (1000 parts per million solution). Referring to Figure 6 a nebuliser was used to produce a fine mist of aerosolised protein (5 pm in diameter, to replicate droplets produced by coughing or talking). The filter was attached to the front of the test rig and a PTFE 0.22 pm syringe filter attached to the back, a vacuum line was attached to the syringe filter to simulate breathing through the filter. The nebuliser was run for 2 minutes, the syringe filter was attached to a syringe filled with 50% water 50% methanol (+1 % formic acid) and eluted into the Waters ACQUITY (RTM) QDa (RTM) Mass Detector. The ionisation method used was electrospray and the MS was run in positive mode with a mass range of 500-1250 Da. The silica coated filters were compared against control (blank) filters made of the same material. This procedure was repeated with BSA and cytochrome C. In the experiments with all of the aerosolised proteins the filter media containing amorphous silica particles effectively removed the airborne proteins compared to the control filter media.

EXAMPLE 2 - Use of the filter media containing amorphous silica particles in a room filter

A room purifier containing a filter medium comprising amorphous silica particles will be installed within a hospital ward. The patients within the hospital ward are known to be infected with Covid 19 caused by infection with SARS-CoV2. The room purifier will be installed in the hospital ward for a number of days. The filter medium will be removed and analysed for the presence of SARS-CoV2. In this way the filter medium can be used to determine the presence of airborne viral particles and also be used to remove the airborne viral particles from circulation.