ACTIVE AGENTS

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to the area of controlled release. More specifically the invention relates to films of microfibrillated cellulose, nanofibril cellulose, nanocrystalline cellulose or whiskers or similar structures for controlled release of drugs, pesticides, herbicides or other molecules.

Description of the related art

Drug delivery is a very important field when it comes to pharmacy. Some substances may have disadvantages that may limit their clinical use, e.g. short in vivo half-lives and low oral bioavailability, which may result in the need for frequent administration of the active substance using different administration methods. Frequent administrations are inconvenient, and result in poor patient compliance and an oscillating drug concentration in the blood. These problems can be circumvented through the use of some sort of controlled release technology. Controlled release products provide prolonged delivery of a drug while maintaining its blood concentration within therapeutic limits.

Traditionally, the most popular form of drug delivery has been ingestion in tabular form. The justification for a modified release dosage form over a conventional tablet is either to circumvent problems in drug absorption or metabolism, or to optimize therapy itself. There is a variety of routes available for drug delivery: oral, nasal, gastrointestinal tract, the eye, skin, and even the vaginal mucosa, as well as implants and targeted drug delivery.

Barriers around reservoirs are often used to control release of drugs, pesticides and herbicides. These barriers can have different physicochemical characteristics and chemical compositions, but it is essential that one can vary the transport and the permeation of the penetrant through the membranes and thus be able to control the release of the penetrant. In many cases the barriers are made of water-insoluble materials. One way to regulate the release rate is to add water-soluble agents to the barrier-forming solution. During exposure to water the water-soluble agent dissolves and leaves pores in the membrane. Thus generally, by regulating the number of pores in the barrier, the permeability of the barrier and the drug release can be controlled. Micro fibrillated cellulose (MFC) consists of long microfibrils produced by delamination of cellulosic fibres in high-pressure homogenizers. MFC is an extensively studied material since it is renewable and has desirable properties originating from its nano- and microstructures. Despite this, very few studies focus on the "wet applications" of MFC, and to the inventors' knowledge no studies are related to the permeability of, or diffusion in, MFC containing films in the wet state (dried films exposed to aqueous solutions). Regarding films and coatings, it is previously known that MFC films have promising properties as an oxygen and air barrier, or even as an oil barrier (1) For wet applications it is known that MFC solutions form strong hydrogels even at low concentrations (2), and MFC has been shown to strongly augment composite hydrogel properties (3).

The present invention relates to films of water-insoluble microfibrillated cellulose (MFC; also known as cellulose nanofibrilles, nanofibril cellulose (NFC)) and/or whiskers (also known as nanocrystalline cellulose (NCC) or nanocellulose). These films would have a great potential in the controlled release area. Such controlled release mainly depends on the diffusion properties of the films, which in turn depends on the porosity and structure of the films. Films for controlled release are often made of one insoluble film-forming polymer and a pore-forming agent. We believe that it for first time has been shown that MFC might be used as the water-insoluble component in films for controlled release of e.g. drugs.

A well known class of pore-forming agents is water-soluble cellulose derivatives, such as hydroxypropyl methyl cellulose (HPMC) and hydroxypropyl cellulose (HPC), which are commonly used in controlled release preparations, see for example U.S. 2009/0214642, US Patent No. 4,680,323 or S. Kamel et al. (4). Normally, when making barrier films using a pore-forming agent, the pore-forming agent is released from the film upon contact with an aqueous solution, leaving pores in the film that increases the permeability of the film. The inventors have surprisingly found that when using MFC as the water-insoluble component of a film, together with e.g. HPMC as the water-soluble (expected pore-forming) agent, the permeability of the film is on the contrary reduced upon contact with the aqueous solution. This is partly due to that HPMC interacts so strongly with the MFC film that it does not leave the film completely upon aqueous contact, but instead forms a gel inside the film that blocks the intrinsic pores of the MFC film so that the permeability decreases. Moreover, HPMC partially forms a gel inside the films and swells the films leading to longer pathway and lower permeability. Further, the formed multi-layered structure of the MFC-film also decreases the permeability of the film, the unique structure probably forming due to HPMC induced modification of the aggregation of MFC. HPMC may be replaced by other hydrophilic polymers, such as HPC or chitosan, which would function in a similar way. This low permeability of the films is very interesting from a controlled release perspective, rendering many possible applications. . It would therefore be interesting to use MFC-containing films, with a content of water-soluble agent from 1-80%, for controlled release of e.g. drugs. Even though including a water-soluble agent is preferred, it is believed that pure MFC films may also have potential in the controlled release area.

One traditional way of producing films for controlled release is to dissolve both the water-insoluble component (such as a water-insoluble polymer) and the water-soluble agent, like a hydrophilic polymer, in an organic solvent. During the film formation the solvent evaporates and the two polymers often phase separate into different regions, which gives rise to a film structure with insoluble and soluble regions. The structure of the water-soluble polymer in dry film will determine the pore structure of the film after exposure to water. Thus, the phase separation is critical for the final pore structure and thus also for controlling the release rates. The polymers used for controlling films are synthetic or semi synthetic. If one could replace these with unmodified cellulose, which is a green biomaterial, it would be a benefit for society. In addition, the film formation process using MFC will not include pore formation, which will lead to more robust structures and ways to control the release rates.

Another traditional way to produce films for controlling the release rates is by using aqueous latex dispersions of insoluble polymer and sometimes dissolved hydrophilic agents. The latex dispersions are stabilized by surfactants. During the film formation the latex particles should coaleasce to form a film. The film formation process includes some problems like migration of dispersion stabilizers. A further difficulty with this process is that films formed using different process parameters and annealing temperatures and times will lead to differing results, different film annealing, and thus different release rates.

To replace the synthetic or semi synthetic insoluble film forming polymer with eg.

MFC, NFC or NCC would be advantageous from an environmental point of view. The lack of surfactants in the water suspension during the film forming process would also avoid the problem of surfactant migration in the films. It is also likely that the film formation process when using eg. MFC, NFC or NCC would be more robust. Further, surfactant migration can cause problems if the material is used on a person's skin as surfactants often cause skin rash or dermatitis

Hence, barriers or films containing MFC would be beneficial from several aspects, such as environmental (MFC is renewable and there is no need for organic solvents), stability (more stable structure and permeability over time compared to latex particle films, whose permeability is affected by the time of storage) and better permeability control since the permeability is mainly due to the one-dimensional swelling compared to a pore structure through the film, and thus less sensitive to structural changes.

Patent application WO 10069046 relates to a method of controlling the dispersibility and barrier properties of dried forms of NCC in aqueous media by controlling the ionic strength and/or the pH of the aqueous media. The application concerns barrier properties of NCC films in aqueous solutions, but does not relate to the area of pharmaceuticals or controlled release. Further, the usage of other additives to control the structure and permeability is not discussed. The application thus does not disclose the scope of the invention.

U.S. Patent No. 6,821,531 discloses the development of a powdered/microfibrillated cellulose excipient suitable for use as a filler-binder-disintegrant in the design and development of solid compacts and capsules, and as a drug carrier or bodying agent in the manufacture of dermatological products. MFC is intended to be inside and fill the capsules, instead of being around the capsules as a controlled release film. In this patent the cellulose disintegrates the tablet and thus speeds up the release but does not control or extend the drug release rate.

The paper of John . Jackson et al. (5) describes the use of NCC as a drug delivery excipient. The very large area and negative charge of NCC suggests that large amounts of drugs might be bound to the surface of this material with the potential for high payloads and optimal control of dosing. NCC is thus used as a drug carrier. Rather than being used as a barrier/film around the drug, the drug is bound to the surface of the NCC. The interaction between drugs and the surface of NCC will depend on ionic strength, the solvent and temperature used, which may lead to less robust drug release rates compared to barrier system where the effect of these parameters will have minor influence on the drug release rate. Moreover, the controlled release is due to surface interactions between NCC and the drug. The paper describes prolonged release from a suspension in contrast to the present invention, which relates to controlled release from a well defined depot. Additionally, the paper discusses pure NCC, and thus relates to an ionic interaction between an active agent and NCC surface.

U.S. Patent No. 6,627,749 describes powdered oxidized cellulose as a drug carrier. It relates to the manufacture of powdered/microfibrillated oxidized cellulose suitable for use as an immobilizing matrix or a carrier for drugs. The patent relates to the release from microparticles or pellets of the material, but does not use the cellulose as a barrier for controlled release, nor does it focus on the use of other exipients for modification of the material structure or release. Furthermore, the cellulose that is used in this patent was oxidized, so that it contains pH sensitive acid groups, and thus showed a pH dependent behavior. In contrast, a pH dependence is not desired or expected for the present invention, where a constant behavior (permeability) is desired.

Thus, we believe that it for first time has been shown that MFC might be used as the water-insoluble component in films for controlled release of e.g. drugs. We also believe that these films have excellent properties when it comes to permeability and permeability control, since the permeability may be controlled by the amount of the hydrophilic polymer or water- soluble agent.

SUMMARY OF THE INVENTION

The general purpose of the invention is to provide films comprising MFC, NFC and/or NCC (herein after referred to as MFC/NFC/NCC) providing controlled permeability of molecules or compounds. The ratio between MFC/NFC/NCC and other components in the film mixture can be used to control the permeability thereof.

A primary object of the invention is to provide mixtures of MFC and/or NFC and/or NCC and optionally a hydrophilic polymer, such as HPMC, to form films or barriers that control the permeability of molecules or active agents, such as drugs, water, pesticides, herbicides, taste-masking agents, flavourings, food additives, nutrients and vitamins. The ratio between MFC and HPMC may be used to control the permeability of the films. HPMC may be replaced by other polymers with the ability to hydrate and swell, or with other agents that dissolve in water, such as lactose, but without the possibilities to swell.

Another object of the present invention is to use films or barriers comprising MFC and/or NFC and/or NCC for the controlled release of active agents, drugs, pesticides, herbicides, taste-masking agents, flavorings, food additives, nutrients and vitamins.

The invention is based on the surprising finding that, when using MFC and/or NFC and/or NCC as the insoluble component when preparing a film, the water-soluble (expected pore-forming) agent does not form pores in the barrier. Instead it is partially released upon contact with an aqueous solution, the part not released from the films remains due to interactions with the MFC/NFC/NCC.

However, due to the hydrophilic nature it forms a gel inside the MFC film and swells. Furthermore, the presence of the water-soluble agent affects the aggregation behaviour and leads to a layered structure of the formed films. Thus, these features will decrease the permeability of the film instead of increasing it as would normally happen in a film when using a pore-forming agent. By regulating the amount of water-soluble (hydrophilic) agent the permeability of the film may be controlled. These new films may render many new

possibilities in the controlled release area.

The invention is described in detail below. The examples and experimental details are disclosed to provide an improved understanding and guidance for those skilled in the art.

Other objects and advantages of the present invention will become obvious to the reader. For the avoidance of doubt, the description of a feature as an Object' of the invention does not necessarily imply that the object is achieved by all embodiments of the invention. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of the description and should not be regarded as limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

Figure 1 shows a typical plot of the volume of radioactive labelled water that have diffused across the film at given time points, here for a sample with 50 % w/w HPMC and a thickness of 38 μηι.

Figure 2 displays the water permeability, normalized versus film thickness, for MFC- HPMC films with varying HPMC content. Error bars indicate one standard deviation (n = 2- 3).

Figure 3 (a-d) illustrates swelling behavior for MFC-HPMC films, depending on HPMC content, a) Water uptake per initial dry weight for initial HPMC contents of; 0 % (A), 20 % (♦), 35 % (o), 50 % (x), and 65 % (·) w/w. b) Swelling per actual dry weight for the samples in "a", c) Changes in film thickness when swelling (·) and swelling per initial dry weight (o) for samples with varying HPMC content submerged for 3 h. d) Water uptake after 24 h for films during the first swelling (black) and the same films re-swollen after drying (grey). Error bars indicate Min/Max (n=2).

Figure 4 shows percentage of HPMC released at different times for MFC-HPMC films with 20 % (x), 35 % (o) and 65 % (A) w/w HPMC. Figure 5 (a-f) illustrates micrographs of MFC-HP MC films after preparation. Top are SEM images of films with: (a) 0 %, (b) 20 % and (c) 50 % w/w HPMC. Bottom are AFM images of films with: (d) 0 %, (e) 20 % and (f) 50 % w/w.

Figure 6 (a-f) shows SEM images of swollen and freeze dried MFC HPMC films. Top row images are at a magnification of lOOOOX for samples with initial HPMC contents of (a) 0 %, (b) 20 % and (c) 50 % w/w. Bottom row is images are at a magnification of 100000X for samples with initial HPMC contents of (d) 0 %, (e) 20 % and (f) 50 % w/w.

Figure 7 shows a SEM image of the cross-section of a swollen and freeze dried MFC HPMC film having initial HPMC content of 50 % w/w.

Figure 8 illustrates a schematic drawing of the close to unidirectional swelling of a layered-structured film composed of non-swelling lamellas and swelling inter layer regions. A schematic example is given of the tortuous path experienced by penetrants (illustrated as an orange spheres) crossing the film in the swollen state.

DETAILED DESCRIPTION OF THE INVENTION AND

PREFERRED EMBODIMENTS THEREOF

The present invention relates to barriers in the form of films of water-insoluble microfibrillated cellulose, MFC, also known as cellulose nanofibrilles or nanofibril cellulose (NFC), or whiskers, also known as nanocrystalline cellulose (NCC) or nanocellulose. These films would have a great potential in the controlled release area. Such controlled release mainly depends on the properties of mass transport, for example flow and diffusion, of the films, which in turn depends on the structure of the films. Films for controlled release are often made of one insoluble film-forming polymer and a pore-forming agent. We believe that it for first time has been shown that MFC and/or NFC and/or NCC might be used as the water-insoluble component in films for controlled release of e.g. drugs.

The general purpose of the invention is to provide films of MFC/NFC/NCC that decrease the permeability of molecules such as active agents, drugs, water, pesticides, herbicides, hygiene products, taste-masking agents, flavorings, food additives, food agents, food products, nutrients or vitamins, i.e. that functions as a barrier. The ratio between MFC/NFC/NCC and water soluble agent can be used to control the permeability. As is apparent, MFC may be replaced by nanocrystalline cellulose (NCC) or nanofibrillar cellulose (NFC). This means that MFC and/or NFC and/or NCC, i.e. mixtures of these in any combination, may be used as the water-insoluble component of the film. MFC/NFC/NCC might be used without a water-soluble (hydrophilic) agent. A well-known class of water-soluble pore-forming agents are cellulose derivates, such as hydroxypropyl methyl cellulose (HPMC) and hydroxypropyl cellulose (HPC). Normally, when making barrier films using a pore-forming agent, the pore-forming agent is released from the film upon contact with an aqueous solution, leaving pores in the film that increases the permeability of the film. The inventors have surprisingly found that when using

MFC/NFC/NCC as the water-insoluble component of a film, together with e.g. HPMC as the water-soluble (expected pore-forming) agent, the permeability of the film is on the contrary reduced upon contact with the aqueous solution. This is due to the fact that HPMC interacts so strong to the MFC/NFC/NCC film that it does not leave the film completely upon aqueous contact, but instead forms a gel inside the film that blocks the intrinsic pores of the

MFC/NFC/NCC film so that the permeability decreases.

Further, the film of MFC/NFC/NCC and HPMC can exhibit a layered structure. The layered structure causes the film to swell unidirectionally, i.e. mostly increasing the film thickness, and causes a longer diffusive path for a penetrant when crossing the film. This further decreases the permeability of the film. It is within the scope of the invention that HPMC may be replaced by other hydrophilic polymers, such as HPC or, methyl cellulose, sodium carboxymethylcellolose, hydroxyethylcellulose, ethyl hydroxyethylcellulose or other modified hydrophilic cellulose derivatives, or modified starch, or chitosan, alginate or other water-soluble polysaccharides or chemically modified versions thereof, or polyacrylic acid, or polyethylene oxide, or polymethacrylates or povidone or polyethylene oxide or other water- soluble synthetic polymers, or salts of the above mentioned polymers, which would function in the same way. The hydrophilic polymers listed above can also be crosslinked.

The inventors have the following three different hypotheses for the observed close to unidirectional swelling (increasing film thickness) and the observed decrease in permeability. 1. The film structure formed during the film creation is influenced by the addition of hydrophilic or water soluble agent in such a way that the MFC/NFC/NCC in the film forms a multi-layer structure. For a water soluble agent with swelling capability, but that will eventually dissolve and leave the film, the MFC/NFC/NCC is initially swollen by the swelling pressure from the water soluble component pushing the MFC/NFC/NCC layers apart, when the water soluble agent is released from the film the film maintains its swollen structure. Thus the effect on permeability is derived from the swelling of the MFC/NFC/NCC film and from the structure of the swollen film. 2. The film structure formed during the film creation is influenced by the addition of hydrophilic or water soluble agent in such a way that the MFC NFC/NCC in the films forms a multi-layer structure. For a hydrophilic agent (for example a crosslinked polymer) or a water soluble agent that interacts strongly with the MFC/NFC/NCC, the agent will not leave the film. Thus the agent will remain in the film and swell, leading to swelling of the film as a whole. The difference from hypothesis 1 is that the swollen agent remains in the film. Thus the effect on permeability is derived from the swelling of the film, the structure of the film and any effects from the remaining hydrophilic or water soluble agent on diffusion inside the film. 3. The film structure formed during the film creation is influenced by the addition of hydrophilic or water soluble agent in such a way that the MFC/NFC/NCC in the film forms a multi-layer structure. For a non swelling water soluble agent (for example non polymer salts) the water soluble agent would not swell. On the other hand, if agent do induce the formation of a multi-layered MFC/NFC/NCC structure, the MFC/NFC/NCC film could swell by that water occupies the inter layer spaces and pushes the layers apart. Similar to hypothesis 1, the effect on permeability is for this hypothesis 3 derived from the swelling of the

MFC/NFC/NCC film and from the structure of the swollen film. Thus hypothesis 3 motivates the use of water-soluble agents that are non swelling for achieving the desired effects of the innovation. The phenomena according to these hypotheses could also occur simultaneously. For example one part of a water soluble polymer could act according to hypothesis 1 , whilst another part could interact with the MFC/NFC/NCC, acting according to hypothesis 2.

The low permeability of the films according to the invention is very interesting from a controlled release perspective, rendering many possible applications in pharmaceutics, food products, pesticides, herbicides, hygiene products, medical devices, implants etc, and may be used in many forms such as; tablet coatings, pellet coatings, capsule coatings, on

microspheres, controlled release layers etc.

It would therefore be interesting to use films comprising MFC, with a content of water-soluble (hydrophilic) agent from 1-80% (w/w), such as 1% water-soluble agent, or 5%, or 10% or 15% or 20% or 25% or 30% or 35% or 40% or 45% or 50% or 55% or 60% or 65% or 70% or 75% or 80% (w/w) water-soluble agent, for controlled release of active agents, e.g. drugs. The content water-soluble agent may vary in the interval from 1-80% (w/w), or 5-80% or 5-65% or 15-65% or 20-65% or 20-55% (w/w) water-soluble agent. It would therefore be interesting to use films comprising NFC, with a content of water- soluble (hydrophilic) agent from 1-50% (w/w), such as 1% water-soluble agent, or 5%, or 10% or 15% or 20% or 25% or 30% or 35% or 40% or 45% or 50% water-soluble agent, for controlled release of active agents, e.g. drugs. The content water-soluble agent may vary in the interval from 1 -50% (w/w), or 5-50% or 5-40% or 15-40% or 20-35% or 20-35% (w/w) water-soluble agent.

It would therefore be interesting to use films comprising NCC or whiskers, with a content of water-soluble (hydrophilic) agent from 1-50% (w/w), such as 1% water-soluble agent, or 5%, or 10% or 15% or 20% or 25% or 30% or 35% or 40% or 45% or 50% water- soluble agent, for controlled release of active agents, e.g. drugs. The content water-soluble agent may vary in the interval from 1-50% (w/w), or 5-50% or 5-40% or 15-40% or 20-35% or 20-35%) (w/w) water-soluble agent.

It would also be interesting to use films comprising MFC, NFC, whiskers or NCC, without any water-soluble (hydrophilic) agent for controlled release of active agents, e.g. drugs.

To clarify the invention further, we hereby define some of the components in more detail. Thus, for the purpose of the present invention the following terms shall be taken to have the indicated meaning. The term "film "means an object having a larger ratio between surface area and thickness, i.e. essentially two-dimensional. It can provided as a coating on an object or it can be free-standing, i.e. it can be handled as a separate object. The term "water soluble agent" means an agent where a minimum of 1 g of the agent can be dissolved in 10000 g solvent. The term "hydrophilic polymer" means a polymer that either is soluble in water according to the above definition or swells (absorbs water solutions) at least 10 % per dry weight of polymer. The invention provides an absorbent composite comprising a superabsorbent polymer and cellulosic fibrils. Superabsorbent materials are commonly understood as being crosslinked polymers with the capacity to absorb liquid many times their own weight upon swelling. The cellulosic fibrils are nano fibrils. The term "nanofibrils" means individual fibrils having a diameter equal to or less than 100 nm at all points along the nanofibril. The diameter may vary along its length. The nanofibrils may exist as individual fibres and/or as clusters of nanofibrils.

The term "nanofibrillated cellulose (NFC)" is used interchangeably with the term "nanofibrils". From nanofibrils one can produce "Whiskers". These are a particular form of nanofibrils having an aspect ratio (length/width) of at least 2. Nanofibrils having a smaller aspect ratio do not qualify as whiskers. The term "microfibres" means individual fibres having a diameter equal or greater than 100 nm but less than or equal to 100 μιη at all points along the microfibre. More specifically, the microfibres may have a diameter greater than 100 nm but less than or equal to 10 μηι or a diameter greater than 100 nm but less than or equal to 1 μπι. The diameter may vary along the length of the microfibre. The microfibres may exist as individual microfibres and/or as clusters of microfibres in the composite. The term MFC (microfibrillated cellulose) is used interchangeably with the term "microfibres".

Microfibrillated cellulose may comprise a fraction of nanofibrils.

Suitably, the composite does not contain cellulosic fibres having an average diameter greater than 100 μηι. The absorbent composite may further comprise cellulosic microfibres having a diameter greater than 100 nm but less than or equal to 100 μιη. Additionally, the absorbent composite may comprise cellulosic microfibres having a diameter greater than 100 nm but less than or equal to 10 μπι. Nanocrystalline cellulose (NCC) or cellulose whiskers are cellulosic material having dimensions less than 100 nm in any direction. The aspect ratio of whiskers should be least 2.

The term "cellulosic " refers to fibrils or fibres from natural sources such as woody and non-woody plants, regenerated cellulose and the derivatives from these fibres by means of chemical, mechanical, thermal treatment or any combination of these. Further, "cellulosic" also refers to cellulosic or cellulose-containing fibres produced by microorganisms.

The term "polymer" includes, but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term

"polymer" shall include all possible configurational isomers of the material. These

configurations include, but are not limited to isotactic, syndiotactic and atactic symmetries.

The term "crosslinked" is used herein to describe a material composed of linear polymer chains which have been submitted to crosslinking by means of a cross-linking agent so that the linear polymer chain has been transformed into a 3-dimensional network structure.

The term "swelling" (or any alternative forms thereof) is used to describe when a material (for example polymers, crosslinked or not) is diluted by absorbing water, but retains a structural integrity separating it (making it distinguishable by analysis) from the surrounding liquid on timescales relevant for the application. The term "controlled release" means release of an agent at a controlled rate for an extended time, at least 1 h. With "film" or "barrier" or "membrane" is meant a thin coating or layer that acts as a bar for passage of an agent.

A primary object of the invention is to provide mixtures of MFC and/or NFC and/or NCC, and HPMC, or other suitable hydrophilic polymer, to form films or barriers that decrease the permeability of e.g. water. The ratio between MFC/NFC/NCC and e.g. HPMC may be used to control e.g. the water permeability and diffusion properties of the films. An increased amount of e.g. HPMC decreases the film permeability. HPMC may also be replaced in the mixture by other polymers with the ability to hydrate and swell, such as HPC or, methyl cellulose, sodium carboxymethylcellolose, hydroxyethylcellulose, ethyl hydroxyethylcellulose or other modified hydrophilic cellulose derivatives, or modified starch, or chitosan, alginate, pectin or other water-soluble polysaccharides or chemically modified versions thereof, or other polysaccharides, or polyacrylic acid, or polyethylene oxide, or polymethacrylates or povidone or polyethylene oxide or polyvinylalcohol (PVOH) or polyvinylaccetate (PVA) other water-soluble synthetic polymers, or sodium alginate, lignin, keratin, fibroin, proteins, or salts of the above mentioned polymers or the crosslinked versions of the above mentioned polymers.

Alternatively, HPMC may be replaced by other agents that dissolve in water, such as sugars and sugar alcohols, such as lactose, mannitol, glucose or taste improving agents such as water-soluble salts or sodium chloride, but without the possibilities to swell.

Another object of the present invention is to use MFC-containing films as barriers, for the controlled release of active agents, drugs, chemical compounds, pesticides, herbicides, taste-masking agents, flavorings, food additives, food products, nutrients, vitamins or other active agents. The barriers in the form of films may surround reservoirs like tablets, dry capsules, microspheres and solutions (to form a capsule with liquid in the inner part), or be used as controlled release layers in medical devices or other devices requiring controlled release, or implants. The barrier material can be applied on tablets and capsules with ordinary coating technologies, such as film coating in fluidized beds or pan coating, or electrospinning, wet spinning, dry spinning, dry-jet wet spinning, melt spinning- gel spinning, electrospraying, casting, spray drying, aerosolizing, atomizing, molding, pressing or extruding.

One embodiment of the invention is to provide a film containing microfibrillated cellulose (MFC), nanofibril cellulose, nanocellulose, nanocrystalline cellulose or whiskers, and prefereably a water-soluble agent. The alternative without a water-soluble agent is also a possibility. Another embodiment is providing a film, wherein the water-soluble agent is a hydrophilic polymer, such as a water-soluble cellulose derivative.

In a preferred embodiment, the hydrophilic polymer is chosen from HPMC, HPC, chitosan, polyacrylic acid, sodium alginate, pectin cellulose, starch, lignin keratin, fibroin, polysaccharides, proteins, polyvinylalcohol (PVOH), polyvinylaccetate (PVA), methyl cellulose, sodium carboxymethylcellolose, hydroxyethylcellulose, ethyl

hydroxyethylcellulose, modified starch, polyethylene oxide, or polymethacrylates or povidone or polyethylene oxide. Preferably, the hydrophilic polymer is HPMC.

In another embodiment the water-soluble agent is chosen from sugars or sugar alcohols, such as lactose, mannitol or glucose, or taste improving agents such as water-soluble salts or sodium chloride.

In one embodiment concentration of the water-soluble agent is 1 -80%, preferably 1- 60% in the film. In another embodiment the concentration of the water-soluble agent is 5- 80%. In another embodiment the concentration of the water-soluble agent is 5-65%. In another embodiment the concentration of the water-soluble agent is 15-65%. In another embodiment the concentration of the water-soluble agent is 5-50%. In another embodiment the concentration of the water-soluble agent is 10-50%. In another embodiment the concentration of the water-soluble agent is 20-65%. In another embodiment the concentration of the water-soluble agent is 20-55%.

Another embodiment of the invention is use of the film mentioned above, for the controlled release of a compound. In one embodiment the compound is a drugs, water, pesticides, herbicides, taste-masking agents, flavourings, food additives, food agents, food products, nutrients or vitamins. In one preferred embodiment the compound is a drug.

Another embodiment of the invention is the use of said film, for the coating of an object, such as a microsphere, a tablet, a capsule, a nanocapsule, a pellet, an implant, a solution or a medical device. Another embodiment is the use of said coated objects for the controlled release of a compound. The compound may be an active agent, drug, water, pesticides, herbicides, taste-masking agents, flavourings, food additives, food agents, food products, nutrients or vitamins.

Another embodiment of the invention is a method for modifying the permeability of a film comprising MFC/NFC/NCC by altering the concentration of a water-soluble agent. In the method, the water-soluble agent is chosen from HPMC, HPC, chitosan, polyacrylic acid, sodium alginate, pectin cellulose, starch, lignin keratin, fibroin, polysaccharides, proteins, polyvinylalcohol (PVOH), polyvinylaccetate (PVA), methyl cellulose, sodium carboxymethylcellolose, hydroxyethylcellulose, ethyl hydroxyethylcellulose, polyethylene oxide, or polymethacrylates or povidone or polyethylene oxide, modified starch, sugars or sugar alcohols, such as lactose, mannitol or glucose, or taste improving agents such as water- soluble salts or sodium chloride. In one embodiment of the method, a higher concentration of the water-soluble agent corresponds to a decreased permeability of the film.

In another aspect of the invention there is provided is a method for producing said barriers or films, the method comprising:

a) Mixing MFC or NFC or FCC, water and preferably a hydrophilic polymer or other suitable agent, to obtain a coating composition;

b) Coating an object with the coating composition from step a), using, any of film coating in fluidized beds or pan coating, or electrospinning, wet spinning, dry spinning, dry-jet wet spinning, melt spinning- gel spinning, electrospraying, casting, spray drying, aerosolizing, atomizing, molding, pressing or extruding, or other suitable methods.

c) Drying the films, e.g. using a coating equipment, in an oven or in ambient conditions.

Within the scope of this invention, the inventors have made films acting as barriers of water-insoluble microfibrillated cellulose, with surprising properties. In particular it can be used as a barrier that can control the release of compounds. It has been previously assumed that addition of the water-soluble agent, HPMC, would create pores in the films and thus increase the permeability. However, it was surprisingly found that the water permeability decreased by adding the water-soluble and pharmaceutically approved polymer HPMC. SEM pictures did not show any increased pore formation, rather the opposite. One could see macroscopic one-dimensional swelling increasing the thickness of the barriers and it was found that the water-soluble agent was partially released. Freeze drying of barriers after exposure to water showed that a layered structure had been formed. The layers are mainly composed of MFC, and were probably formed through alteration of the inherent aggregation tendency of MFC in the presence of HPMC. The HPMC has swelling capability and the inventors assume that this is one reason for the observed macroscopic swelling that is mainly one-dimensional, i.e. dramatically increasing the film thickness without significantly altering the film in the length dimension. As mentioned above, the HPMC is partially dissolved during the experiment, but not completely released. The decrease in permeability can be explained by that the transport distance for the penetrant increases due to that it must pass around the MFC planes with low permeability and that the thickness of the barrier has increased due to the swelling.

/. Theory behind the invention

The permeability of a film is determined by the rate of diffusion of molecules through the film. Fick's first law of diffusion for ideal solutions is:

where j is the flux per unit area, D is the diffusion coefficient c is concentration of the diffusing specie and z is the direction of diffusion.

The diffusive flow over a film is more commonly written in terms of permeability (P) as: / = -PA(c _d - c _a ) (2)

where the permeability coefficient is depending on the effective diffusion coefficient in the film (D _e ) and the film thickness (h) as:

ρ = τ (3)

In summary, the theory behind the invention is based on both the properties of MFC and a hydrophilic agent, such as HPMC, and the properties of such a combination. HPMC is an associative polymer that forms complexes between and within polymer chains, and could potentially interact strongly to the MFC in the films. The similarity of the materials may make it possible for non-substituted regions of the HPMC to form hydrogen bonds with the MFC surfaces. If HPMC binds strongly to the MFC, it will not leave the film, but will gel inside the film. This will lead to gel blocking of the inherent pores of the MFC films, thus decreasing the permeability of the films. This leads to gel blocking of the inherent pores of the MFC films, which leads to decreasing D _e and reduced permeability of the films. The structured multi layers formed in the MFC film further decrease D _e and thereby the permeability. Finally, the layered structure causes unidirectional swelling of the film thickness (h), decreasing the permeability even further.

2. Production of the MFC/NFC/NCC -containing barriers/films

HPMC and MFC/NFC/NCC were prepared as stock solutions and mixed to achieve HPMC concentrations of 0, 20, 35, 50 65 and 80% w/w in the formed films. By keeping the solutions at 30 °C in a desiccator with freshly dried silica gel orange, the films were acquired,

2.1 Characterization of the film structure The structure of the MFC/NFC/NCC -HPMC film was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The structure of the film after submersion was analyzed using SEM on both dried and freeze dried samples. Both analyses revealed that the films were dense and non-porous on the investigated length scales. Samples with increasing HPMC content displayed more individual fibres in the structure. The AMF results showed that the presence of high HPMC concentrations prevents aggregation of the MFC/NFC/NCC during film formation, thus rendering altered structures for high HPMC contents.

2.2 Analysis of water permeability

The water permeability of the films was determined using an Ussing chamber utilizing tritiated water as the diffusing probe. Films with < 50% HPMC were durable and kept their integrity throughout the 3 h analysis. The diffusive flow through the films was close to constant. Films with >50% HPMC were increasingly fragile, but showed a constant diffusive flow up to the point of rupture.

2.3 Analyzing the swelling of the films

The swelling of the films was analyzed using both gravimetrical analysis and microscopy observations. Swelling analyses were conducted on films containing 0-65% w/w HPMC. All samples showed very quick initial swelling, and the swelling per initial dry weight increased dramatically for HMPC contents > 30% w/w.

2.4 Release of HPMC

The release of HPMC from the films was analyzed using size exclusion

chromatography, multiangle light scattering, coupled with refractive index detection (SEC- MALS-PvI) and through gravimetrical analysis. The analysis revealed that some, but not all, of the HPMC was released from the films. A larger percentage of HPMC was released from films with higher HPMC content.

3. Uses of the barriers

The MFC/NFC/NCC containing barriers of the invention may be used in several applications, such as coatings, films and controlled release layers. These barriers, coatings, layers and films may be used to surround reservoirs like tablets, dry capsules, nanocapsules, microspheres and solutions (to form a capsule with liquid in the inner part) and may further be used as controlled release layers in medical devices, implants or other devices requiring controlled release. These reservoirs may be used in different controlled release applications, such as slow release from tablets, pellets, microspheres, microcapsules, patches, transdermal delivery systems etc, and may be administered by several routes, such as via oral, rectal, vaginal, nasal, subcutaneous, transdermal, pulmonary, intravenous or intramuscular administration, or via injections.

The controlled release layers may be used for active agents, drugs, chemical agents, pesticides, herbicides, hygiene products, taste-masking agents, flavorings, food additives, food agents, food products, nutrients or vitamins, or to deliver other molecules to the body.

In summary, the inventors for the first time shows that the permeability of films composed of MFC/NFC/NCC and HPMC surprisingly decreased with increasing HPMC content. The observed permeability values were in the same range as for film systems used in controlled drug delivery, indicating these films as possible new alternatives for controlled release. The films with high MFC contents were also shown to have great swelling capacity per weight network in the films, in fact being in the superabsorbent range. It is believed that the observed swelling and permeability is due to HPMC affecting the nano and micro structure of the formed films by influencing the aggregation of MFC, with the MFC self assembling into fine layered structures.

EXAMPLES

Example 1 /. Materials

Micro fibrillated cellulose (MFC) was bought from the Paper and Fibre Research Institute PFI, Trondheim, Norway. The MFC had been prepared from commercial bleached kraft pulp using a mechanical pre-treatment followed by homogenization according to Eriksson et al (6), and has previously been characterized as highly heterogeneous (3).

Hydroxypropyl methyl cellulose (HPMC) was of the grade 90 SH 100 SR, Shin-Etsu

Chemical Co., Ltd., Tokyo, Japan. Water used for the permeability analyses was ultrapure deionized (Maxima USF, Elga, UK). The swelling and release experiments were performed using deionized water. Phosphate buffer for SEC-RI analysis was prepared from analytical grade ingredients. Tritiated water (PerkinElmer, USA) was used as the diffusing species in the water permeability measurements.

2. Film preparation

Stock solutions of HPMC and MFC were prepared having a concentration of 0.4 % w/v. These stock solutions were mixed to get HPMC concentrations of 0, 20, 35, 50, 65 and 80 % w/w in the films. Films were obtained by pouring 45 g solution into 100 ml weigh boats (VWR, Stockholm, Sweden) and evaporating the water at 30 °C in a desiccator with freshly dried silica gel orange (Sigma-Aldrich, Steinheim, Germany) until dry (about 3 weeks), the silica gel was replenished every three days. The films were stored in desiccators with Silica gel orange in between analyses.

3. Scanning electron microscopy (SEM)

Films were analyzed after preparation and after submersion for 3 h in the Ussing chambers using an SEM LEO Ultra 55 SEM equipped with a field emission gun (LEO

Electron Microscopy Group, Germany) in secondary electron detection mode. The previously submerged films were prepared for analysis both by drying at 70 °C and by freezing at -32 °C followed by freeze drying using a Jouan LP3 freeze dryer (Jouan, France). Before SEM analysis all samples were sputter coated with gold in Argon atmosphere for about 1 min using a S150B Sputter Coater (Edwards, England).

4. Atomic force microscopy (AFM)

AFM analysis of films after preparation was performed using a Digital Instrument Nanoscope Ilia with a type G scanner (Digital Instrument Inc.). The used cantilever was a Mikro Masch silicon cantilever NSC 15. The AFM was operated at a resonance frequency of about 330 kHz in tapping mode, scan rate was 1 Hz and the measurements were performed in air.

5. Characterization of film structure after preparation

The structural dependence of the formed films on HPMC contents was investigated by subjecting as prepared films, with 0, 20, and 50 % w/w HPMC, to AFM and SEM analysis. As seen in Fig. 5, both analyses, at different length scales, revealed that the films were dense and non-porous. As seen in the AFM micrographs (Fig 5d-f), samples with increasing MFC content displayed more individual fibres in the structure. The AFM results suggests, as indicated by other results, that the presence of high HPMC concentrations prevents aggregation of the MFC during film formation. Leading to altered film structures for high HPMC contents.

6. Characterization of film structure after swelling To get further information on films structure in the swollen state, the structure responsible for the permeability and swelling results, film samples with 0, 20, and 50 % w/w HPMC were investigated using SEM after submersion for 3 h in Ussing chambers. At that time close to all of the swelling and HPMC release had already occurred (see Fig. 3 and 4). In an attempt to preserve the structures of the swollen films they were freeze-dried prior to the SEM analysis. It is common that conclusions regarding the structure of porous controlled release films in the wet state are drawn from the structure of submerged films after conventional drying. Therefore this method was investigated as well. It was found that conventional drying did change the structure of the films. The change in structure upon drying is in line with the swelling results that reswollen films had dramatically decreased swelling.

The SEM analysis of freeze-dried films revealed a highly porous structure for the pure MFC, having hundreds of nanometers in pore sizes. HPMC-containing films had more dense structures with increasing MFC content (Fig. 6). This may seem strange as the pore size generally increases with decreasing concentration of network within the sample. There are however several logical explanations for the observed decrease in pore size, all in line with previously discussed results: First, if the presence of HPMC as suggested hinders the aggregation of MFC into larger structures, the resulting decrease in effective fibre radii should promote a decreased pore size as discussed in works on pore sizes in fibrous matrixes (7-9). Also, not all the HPMC was released from the films. Any remaining HPMC should lead to a smaller observed pore size as it will also form a dry network structure upon drying. Finally, SEM analysis of a swollen and freeze-dried film displayed a structure having stacked layers in the z-direction (see Fig. 7). Care should be taken when interpreting freeze-dried structures as describing the true structure of a wet sample. However, the swelling results did show that almost all of the film swelling occurred in the z-direction. This would be expected for a layered structure where the individual layers exhibited low swelling and deformability, but where the interlayer regions are swellable. Such behavior has been reported for a novel anisotropic hydrogel by Haque et al. (10). In such systems swelling would mainly occur when water occupies the inter-layer spaces, pushing the layers apart (see schematic drawing in Fig. 8). The swelling results in combination with the layered structure observed in SEM, strongly suggests that the network structure of the wet samples was of the layered form. The hypothesis is further supported by that a lamellar structure has been previously observed for dry MFC films (1 1). A layered structure would also exhibit locally higher MFC

concentrations in the layers than suggested by the swelling (Q _Ka\ ) and as SEM analyses would have been performed on the surface of a layer, this would further explain the observed decrease in pore size.

7. Water permeability analysis

Water permeability was analyzed using a modified Ussing chamber with the setup previously described (12). Briefly, a film sample was placed between a donor and acceptor compartment. Initial film thickness was measured at five different positions using an IP 54 micrometer (Mitutoyo, Japan) and was averaged. Initially 15 ml of dissolution H ₂ 0 was simultaneously added to the donor and the acceptor compartments, and two paddles were used to stir the contents of the two chambers at a speed of about 200 rpm. After 5 minutes a small amount of tritiated labelled water (10 μΐ, 400 kBq) was added to the donor compartment. At determined times 500 μΐ sample was extracted from the acceptor compartment and was replaced by the same amount of H ₂ 0. The temperature was maintained at 37 °C during the analyses. The extracted samples were weighed and analyzed using a scintillator counter (1414 LSC, Win Spectral, Wallac). The tritium activity in the acceptor compartment at the different times was used to calculate the amount of water that had diffused through the film at each time. The film permeability was then calculated from Eq. 5.

The water permeability of films composed of MFC, having different initial amount of the conventionally pore-forming water-soluble polymer HPMC (0, 20, 35, 50, 65 and 80 % w/w), was analyzed. Films with < 50 % HPMC kept their integrity throughout the 3 h analysis without breaking. The films displayed a close to constant diffusive flow through the analysis, as seen in the exemplifying Fig. 1. Films having > 50 % HPMC were more fragile and could only be analyzed for about 1 h before breaking. However, in these experiments the films were exposed to water from two sides, which will not be the case when they act as barriers for controlled release applications. None the less, the diffusive flow was rather constant up to the point of rupture. The permeability normalized for initial film thickness (PN) was about the same for 0 and 20 % w/w HPMC content. For higher HPMC contents PN decreased more than twofold, opposite of what would normally be expected with increasing content of water- soluble polymer (13, 14). For HPMC contents of 35 - 80 % w/w the permeability was also reduced, with a small minimum for 50 % w/w HPMC (see Fig. 2). Of great promise for applications is that the investigated films exhibited PN values similar to those reported for currently used controlled release polymer film systems (15, 16).

By visual inspection it was observed that all the films had turned white after submersion and that a considerable swelling had occurred in the z-direction of films having > 35 % w/w HPMC. As seen from Eq. 6, increased film thickness would lead to decreased permeability if the other parameters were constant. On the other hand, it is well known that the diffusion coefficient (D) in swollen polymer matrixes increases with decreasing polymer concentration (17, 18). Also, swelling of the films would lead to an increase of the partition coefficient (H). An increase in either D or H should lead to an increase in permeability. In order to separate the mechanisms behind the unexpected decrease in permeability with increasing HPMC content and investigate if HPMC did remained in the films or was released, swelling analyses and HPMC release studies were conducted. 8. Swelling of films

For analysis of swelling and weight loss during swelling, rectangular film pieces were cut out and the dry weights (4-10 mg) were recorded using a Shimadzu AUW220D

(Shimadzu Philippines Manufacturing Inc., Philiphines). The films were swollen in 5 ml H ₂ 0 in Non-Tissue Culture Treated Plates, 12 Well, Flat bottom with Low Evaporation Lid (Becton Dickinson and Company, Franklin Lakes, USA). The swelling studies were performed at 37 °C and shaking at 300 rpm using a Grant-bio PHMP-4 (Grant Instruments Ltd., Cambridg, UK). At specified times (10 min to 24 h) the weights of the swollen samples were recorded and the swelling degree per initial weight was calculated as:

where m is the wet mass of the film and is the initial dry weight of the film. The samples were then dried and the weight was again recorded, the swelling degree per actual dry weight was subsequently calculated as:

^Qreal - ⁽⁵⁾

where is the weight of the dried film. Samples submerged for 24 h, and followed by drying, were also re-swollen and the degree of swelling was again calculated using Eq. 8 and 9.

Dimensional changes upon swelling were investigated by cutting out small rectangular film pieces and recording their initial and swollen thickness using a microscope. Initial film thicknesses were determined using an Olympus BH2 research microscope with a Microscope digital camera system DP 12 (Olympus) in reflectance mode. Film thicknesses of samples submerged for 3 h, as described for mass uptake determination, were determined using an USB-microscope (Digimicro, China), with an in-image reference of known dimension to determine sample dimensions. The unidimensional swelling of the film, the change in film thickness, was calculated as:

where h is the wet thickness of the film and h _t is the initial thickness of the dry film. Swelling analyses for films containing 0 - 65 % w/w HPMC (the films with 80 % w/w

HPMC were excluded due to their very fragile nature) revealed that all samples displayed very quick initial swelling and that the swelling per initial dry weight (Q,) increased dramatically for HPMC contents >35 % w/w (Fig. 3a). The dimensional changes of films swollen for 3 h showed that most of the swelling took place by increasing the thickness (h) of the films; see Fig. 3b and Table 1. From re-dried films the swelling per actual material present within the wet films was calculated (Q _rea d- The acquired Q _rea i values were surprisingly large for films having HPMC contents >35 % w/w (as high as 52 g/g) for the films with 65 % w/w HPMC (see Fig. 3c).

To determine if the large swelling was an effect derived from the structure of the films and if this structure was retained upon swelling, films swollen for 24 h were dried and re- swollen. From the results it was clear that the high swelling (Q _rea i) was not retained upon re- swelling (Fig. 3d), but some small increase of the swelling was still seen for samples with higher initial HPMC content. Thus, the extremely large swelling for films with > 35 % w/w HPMC was derived from the structure present in the films after preparation and this structure was altered upon swelling and subsequent drying. The structural alteration is probably due to the aggregation of fine structures during drying. This is supported by the fact that MFC is known to form aggregates upon drying (3, 11, 19).

9. Size exclusion chromatography, multiangle light scattering, refractive index detection (SEC-MALS-RI)

HPMC release from the films was determined as follows. Film pieces were cut out and their dry weights recorded. The film pieces were then subjected to USP release studies; 500 ml phosphate buffer, pH 6.8, 75 rpm, 37 °C. Samples were taken out at specified time point and were analyzed with regard to HPMC concentration using a SEC-MALS-RI system. The column used was a TSKgel GMPWxl 7.8mmx300mm 13um (TOSOHAAS, Germany). The MALS used was a DAWN EOS (Wyatt Technology, Santa Barbara, USA) and the RI detector was an OPTILAB rEX (Wyatt Technology, Santa Barbara, USA). SEC-MALS-RI analysis of HPMC release from films (20, 35 and 65 % w/w HPMC) revealed that some, but not all, of the HPMC was released from the films; see Fig. 4. The HPMC released determined by SEC-MALS-RI was in good agreement with calculations based on weight loss after swelling for pure MFC films and films containing HPMC.

Interestingly, a larger percentage of the HPMC was released from films having higher initial HPMC content, indicating that interactions between MFC and HPMC are a cause for the retention of some HPMC. Given that MFC exists as particles such interactions should occur at the surfaces of the MFC. Thus, samples with a higher surface area of the MFC should release less HPMC per MFC. Indeed, the mass HPMC retained within the films per mass of initial MFC after 24 h was 0.14, 0.26 and 0.41 for films with 20, 35 and 65 % w/w HPMC, respectively. As reasoned based on the swelling results, it seems as if films with higher HPMC content had formed different structures during the film-forming process, and as if those structures had an increased MFC surface area, which could be because HPMC prevents aggregation of MFC during film formation, similarly to that hemicelluloses prevents the coalescence of cellulose microfibrills during drying (20).

10. Discussion on the mass transport through the films

Based on the permeability results and the swelling results it can be concluded that the highly surprising permeability effects observed were mainly derived from the high

unidirectional swelling of the films, increasing the film thickness h in Eq. 6. However, the highly swollen films also had a layered structure, which further decreased the permeability, without the layered structure the same reduction in permeability would not have been achieved. Finally, it cannot be excluded that some reduction in permeability is also derived from gelled HPMC that remains in the films and causes some blocking of the pores in the MFC network.

Example 2 1. Materials

Nano fibrillated cellulose (NFC, generation 1) was kindly provided by INNVENTIA

AB, Sweden and nanocrystalline cellulose (NCC) was prepared as follows:

Microcrystalline cellulose (MCC) powder (Avicel PH 101, FMC) was mixed with Milli-q water and hydrolysed by adding sulphuric acid drop wise to a final acid concentration of 64% w/w for 3 h at 45 °C with continuous stirring. The hydrolysis was quenched by adding a 10- fold amount of water to the reaction mixture. The resulting mixture was centrifuged (5100 rpm, Sigma 4K15 centrifuge, UK) for 10 minutes at room temperature. The supernatant was decanted to concentrate the cellulose and remove excess water and acid. The precipitate was rinsed, re-centrifuged and dialyzed against water for 5 days. The suspension was sonicated (Vibracell Sonicator, Sonics and Materials Inc., Danbury, CT) at 60% output while cooling in an ice bath. The cellulose were then converted to sodium salt by conductometric titration with 0.020 M NaOH. The sulphonate groups of the nanocrystals were removed according to Kloser and Gray (Kloser, E.; Gray, D G. Langmuir. 2010, 26 (16), 13450-13456.).

Hydroxypropyl methyl cellulose (HPMC) was of the grade 90 SH 100 SR, Shin-Etsu Chemical Co., Ltd., Tokyo, Japan. Tritiated water (PerkinElmer, USA) was used as the diffusing species in the water permeability measurements. 2. Film preparation

Stock solutions of HPMC and NFC were prepared having a total concentration of 0.47 % w/v, with a HPMC concentration of 0 or 35% (w/w) in the film. Stock solution from NCC was prepared having a total concentration of 0.97% (w/v), with HPMC concentration of 35% (w/w) in the film. The films was sprayed using an airbrush compressor (Dynamic TC318 - Airbrush Kompressor) through a nozzle.

3. Water permeability analysis

Water permeability was analysed using a modified Ussing chamber with the setup previously described above. Briefly, a film sample was placed between a donor and acceptor compartment. Initial film thickness was measured at six different positions using an IP 54 micrometer (Mitutoyo, Japan) and was averaged. Initially 15 ml of dissolution H ₂ 0 was simultaneously added to the donor and the acceptor compartments, and two paddles were used to stir the contents of the two chambers at a speed of about 200 rpm. After 5 minutes a small amount of tritiated labelled water (10 μΐ, 400 kBq) was added to the donor compartment. At determined times 500 μΐ sample was extracted from the acceptor compartment and was replaced by the same amount of H ₂ 0. The experiments were performed at room temperature during the analyses. The extracted samples were weighed and analysed using a scintillator counter (Tri-Carb Liquid Scintillation Analyzer B2810TR, PerkinElmer, USA). The tritium activity in the acceptor compartment at the different times was used to calculate the amount of water that had diffused through the film at each time. The film permeability was then calculated.

Films with 0 and 35% HPMC kept their integrity throughout the 3 h analysis without breaking. The films displayed a close to constant diffusive flow through the analysis, as seen in the exemplifying Fig. 1. The permeability normalized for initial film thickness (P^). For 35% HPMC contents P _N was 2.12 10 ^"11 m ² /s for NFC and 5.73 10 ^"12 m ² /s for NCC. For NFC with 0% HPMC / was equal to 4.33 10 ¹¹ m ² /s, but it was not possible to determine the for the NCC case with 0% HPMC since the films from pure NCC were very brittle. The decrease with increased content of HPMC was thus confirmed for the NFC case.

By visual inspection it was observed that all the films had turned white after submersion and that a considerable swelling had occurred in the z-direction of films having > 35 % w/w HPMC.

REFERENCES

1. C. Aulin, M. Gallstedt and T. Lindstrom, Cellulose, 2010, 17, 559-574.

2. O. Ikkala, R. H. A. Ras, N. Houbenov, J. Ruokolainen, M. Paakko, J. Laine,

M. Leskela, L. A. Berglund, T. Lindstrom, G. ten Brinke, H. Iatrou, N. Hadjichristidis and C. F. J. Faul, Faraday Discuss., 2009, 143, 95-107.

3. M. Larsson, M. Stading and A. Larsson, Soft Mater., 2010, 8, 207-225.

4. S. amel N. Ali, K. Jahangir, S. M. Shah, A. A. El-Gendy, eXPRESS

Polymer Letters, 2008, 11(2): 758-778.

5. J. K. Jackson, K. Letchford, B. Z. Wasserman, L. Ye, W. Y. Hamad, H. M.

Burt. Int. J. ofNanomedicine, 2011, 6, 321-330.

6. 0. Eriksen, Syverud, K. and Gregersen, 0, Nord. Pulp Paper Res. J. , 2008,

23, 299-304.

7. A. G. Ogston, Transactions of the Faraday Society, 1958, 54, 1754-1757.

8. M. J. Lazzara, D. Blankschtein and W. M. Deen, J. Colloid Interf. Sci.,

2000, 226, 1 12-122.

9. A. P. Chatterjee, J. App. Phys., 2010, 108, 063513-063517.

10. M. A. Haque, G. Kamita, T. Kurokawa, K. Tsujii and J. P. Gong,

Adv.Mater., 2010, 22, 51 10-51 14.

11. M. Minelli, M. G. Baschetti, F. Doghieri, M. Ankerfors, T. Lindstrom, I.

Siro and D. Plackett, J. Membrane Sci., 2010, 358, 67-75.

12. J. Hjartstam and T. Hjertberg, J. Appl. Polym. Sci. , 1999, 74, 2056-2062.

13. P. Sakellariou and R. C. Rowe, Prog. Polym. Sci., 1995, 20, 889-942.

14. J. Parmar, M. Rane, V. Dias and A. Rajabi-Siahboomi, Pharma Times,

2010, 42, 34-39.

15. M. Larsson, J. Hjartstam, J. Berndtsson, M. Stading and A. Larsson, Eur. J.

Pharm. Biopharm., 2010, 76, 428-432.

16. M. Marucci, J. Hjaertstam, G. Ragnarsson, F. Iselau and A. Axelsson, J.

Controlled Release, 2009, 136, 206-212.

17. L. Masaro and X. X. Zhu, Prog. Polym. Sci., 1999, 24, 731-775.

18. A. H. Muhr and J. M. V. Blanshard, Polymer, 1982, 23, 1012-1026.

19. E. L. Hult, P. T. Larsson and T. Iversen, Polymer, 2001 , 42, 3309-3314. 0. S. Iwamoto, K. Abe and H. Yano, Biomacromolecules, 2008, 9, 1022-1026.