ORAL CARE COMPOSITIONS

Field of the Invention
The present invention relates to oral care compositions
which exhibit enhanced mildness without compromising
foamability, product texture or phase stability.
Background of the Invention
Foam is a desirable characteristic of oral care compositions
such as dentifrices, since it enables the dentifrice to
spread throughout the oral cavity during brushing and
contact tooth surfaces thoroughly. Compositions with good
foaming ability are also preferred by consumers since the
foaming provides the perception that the composition is
cleaning effectively.
Good foaming ability is generally achieved in oral care
compositions by the use of an anionic surface active agent.
Sodium lauryl sulphate (SLS) is the most commonly used
anionic surfactant, and a typical dentifrice contains up to
2 or 3% of SLS (by weight based on total weight) for its
foaming and surfactant action.
Anionic surface active agents such as SLS have been
associated in some cases with mild adverse effects such as
unpleasant flavour reactions when drinking or eating citrus
shortly after tooth brushing. Accordingly, for consumers
susceptible to these effects it would be desirable to reduce
the content of anionic surface active agents such as SLS.
However, other surface active agents generally do not foam
as well as the anionic surface active agents.
Efforts have been made in the prior art to reduce the
surfactant content of a high foaming toothpaste. According
to US 4,301,141, the inclusion in a toothpaste of gelatin or
a gelatinous egg white product makes it possible to
significantly reduce the toothpaste surfactant content and
still obtain high foaming ability.
However, attempts to reproduce toothpastes described in the
specific examples of US 4,301,141 have resulted in products
which immediately phase separate on storage and which have a
pronounced unpleasant "jelly-like" texture. Furthermore, the
level of sodium lauryl sulphate in these products is not
particularly low, ranging from 1.5 to 2% (by weight based on
total weight) .
It is an object of the present invention to provide oral
care compositions which have a significantly reduced level
of anionic surfactant compared to conventional levels, but
which do not suffer from the disadvantages described above.
Summary of the Invention
The present invention provides a non-aerated, foamable oral
care composition comprising less than 1.5 anionic
surfactant (by total weight anionic surfactant based on the
total weight of the composition) , abrasive cleaning agent
and hydrophobin.
The composition of the invention is mild to oral mucosa yet
exhibits excellent foamability, texture and storage
stability .
In another aspect the invention provides the use of
hydrophobin for boosting mildness in a non-aerated, foamable
oral care composition.
Hydrophobins are a group of very surface-active, fungal
proteins known to self-assemble on various
hydrophobic/hydrophilic interfaces. The self-assembled films
coat fungal structures and mediate their attachment to
surfaces. Hydrophobins have been proposed for use in
cosmetics, for the purpose of surface binding.
US2003/0217419 suggests that hydrophobins can be used to
treat the surface of keratin materials in order to obtain a
cosmetic deposit that withstands several shampoo washes. CA
2 612 458 describes a cosmetic composition containing a
hydrophobin polypeptide sequence, which is alleged to bind
to keratin-containing materials, mucosa or teeth.
Detailed Description of the Invention
The term "non-aerated" in the context of the present
invention means a composition into which gas (i.e. air or
other gas such as carbon dioxide, nitrogen, nitrous oxide,
propane, butane, isobutane, dimethyl ether or mixtures
thereof) has not been intentionally incorporated prior to
usage by the consumer.
The term "foamable" in the context of the present invention
means a composition which is capable of forming a foam in
the process of usage by the consumer, such as during tooth
brushing with the composition.
Anionic Surfactant
The oral care composition of the invention comprises less
than 1.5% anionic surfactant (by total weight anionic
surfactant based on the total weight of the composition) .
Examples of anionic surfactants include the sodium,
magnesium, ammonium or ethanolamine salts of C to Cis alkyl
sulphates (for example sodium lauryl sulphate) , C to Cis
alkyl sulphosuccinates (for example dioctyl sodium
sulphosuccinate) , Cs to Cis alkyl sulphoacetates (such as
sodium lauryl sulphoacetate) , Cs to Cis alkyl sarcosinates
(such as sodium lauryl sarcosinate) , Cs to Cis alkyl
phosphates (which can optionally comprise up to 10 ethylene
oxide and/or propylene oxide units) and sulphated
monoglycerides .
Mixtures of any of the above described anionic surfactants
may also be used.
The total amount of anionic surfactant in compositions of
the invention preferably ranges from 0 to 1.5 , more
preferably from 0.25 to 1.0% by total weight anionic
surfactant based on the total weight of the composition.
This provides the optimum balance between mildness and
foaming.
Abrasive Cleaning Agent
The oral care composition of the invention comprises
abrasive cleaning agent.
Suitable abrasive cleaning agents include abrasive silicas
(such as silica xerogels, hydrogels and aerogels and
precipitated particulate silicas) , calcium carbonates,
dicalcium phosphate, tricalcium phosphate, calcined alumina,
sodium and potassium metaphosphate, sodium and potassium
pyrophosphates, sodium trimetaphosphate, sodium
hexametaphosphate and particulate hydroxyapatite.
Calcium carbonates are a preferred class of abrasive
cleaning agent in compositions of the invention. The amount
of calcium carbonate in compositions of the invention
generally ranges from 10% to 70%, more preferably from 20%
to 50% by weight based on the total weight of the
composition .
Abrasive silicas are another preferred class of abrasive
cleaning agent in compositions of the invention. The amount
of abrasive silica in compositions of the invention
generally ranges from 2% to 20%, more preferably from 5% to
12% by weight based on the total weight of the composition.
Mixtures of any of the above described abrasive cleaning
agents may also be used.
The total amount of abrasive cleaning agent in compositions
of the invention will depend on the particular agent (or
agents) used, but suitably ranges from 3 to 75% by total
weight abrasive cleaning agent based on the total weight of
the composition.
Hydrophobin
The oral care composition of the invention comprises at
least one hydrophobin.
Hydrophobins are a well-defined class of proteins (Wessels,
1997, Adv. Microb. Physio. 38: 1-45; Wosten, 2001, Annu Rev.
Microbiol. 55: 625-646) capable of self-assembly at a
hydrophobic/hydrophilic interface, and having a conserved
sequence :
n-C-X5-9-C-C-Xii-39-C-X8-23 _ - - -C -C - - _ - m
(SEQ ID No. 1 )
where X represents any amino acid, and n and m independently
represent an integer. Typically, a hydrophobin has a length
of up to 125 amino acids. The cysteine residues (C) in the
conserved sequence are part of disulphide bridges. In the
context of this invention, the term hydrophobin has a wider
meaning to include functionally equivalent proteins still
displaying the characteristic of self-assembly at a
hydrophobic-hydrophilic interface resulting in a protein
film, such as proteins comprising the sequence:
X -C-Xi-5o-C-Xo-5 _ -X - oo_ -X - oo_ C-Xi-5o-C-Xo-5 _ C-Xi-5o-C-Xm
(SEQ ID No. 2 )
or parts thereof still displaying the characteristic of
self-assembly at a hydrophobic-hydrophilic interface
resulting in a protein film. In accordance with the
definition of this invention, self-assembly can be detected
by adsorbing the protein to Teflon and using Circular
Dichroism to establish the presence of a secondary structure
(in general, a-helix) (De Vocht et al ., 1998, Biophys. J .
7 : 2059-68) .
The formation of a film can be established by incubating a
Teflon sheet in the protein solution followed by at least
three washes with water or buffer (Wosten et al ., 1994,
Embo . J . 13: 5848-54) . The protein film can be visualised by
any suitable method, such as labelling with a fluorescent
marker or by the use of fluorescent antibodies, as is well
established in the art. m and n typically have values
ranging from 0 to 2000, but more usually m and n in total
are less than 100 or 200. The definition of hydrophobin in
the context of this invention includes fusion proteins of a
hydrophobin and another polypeptide as well as conjugates of
hydrophobin and other molecules such as polysaccharides.
Hydrophobins identified to date are generally classed as
either class I or class II. Both types have been identified
in fungi as secreted proteins that self -assemble at
hydrophobic-hydrophilic interfaces into amphipathic films.
Hydrophobin-like proteins have also been identified in
filamentous bacteria, such as Actinomycete and Streptomyces
sp. (WO01/74864; Talbot, 2003, Curr. Biol, 13: R696-R698).
These bacterial proteins by contrast to fungal hydrophobins,
may form only up to one disulphide bridge since they may
have only two cysteine residues. Such proteins are an
example of functional equivalents to hydrophobins having the
consensus sequences shown in SEQ ID Nos. 1 and 2 , and are
within the scope of this invention.
The hydrophobins can be obtained by extraction from native
sources, such as filamentous fungi, by any suitable process.
For example, hydrophobins can be obtained by culturing
filamentous fungi that secrete the hydrophobin into the
growth medium or by extraction from fungal mycelia with 60%
ethanol. It is particularly preferred to isolate
hydrophobins from host organisms that naturally secrete
hydrophobins. Preferred hosts are hyphomycetes (e.g.
Trichoderma) , basidiomycetes and ascomycetes. Particularly
preferred hosts are food grade organisms, such as
Cryphonectria parasitica which secretes a hydrophobin termed
cryparin (MacCabe and Van Alfen, 1999, App . Environ.
Microbiol 65: 5431-5435).
Alternatively, hydrophobins can be obtained by the use of
recombinant technology. For example host cells, typically
micro-organisms, may be modified to express hydrophobins and
the hydrophobins can then be isolated and used in accordance
with the present invention. Techniques for introducing
nucleic acid constructs encoding hydrophobins into host
cells are well known in the art. More than 34 genes coding
for hydrophobins have been cloned, from over 16 fungal
species (see for example W096/41882 which gives the sequence
of hydrophobins identified in Agaricus bisporus ; and Wosten,
2001, Annu . Rev. Microbiol. 55: 625-646). Recombinant
technology can also be used to modify hydrophobin sequences
or synthesise novel hydrophobins having desired/improved
properties .
Typically, an appropriate host cell or organism is
transformed by a nucleic acid construct that encodes the
desired hydrophobin. The nucleotide sequence coding for the
polypeptide can be inserted into a suitable expression
vector encoding the necessary elements for transcription and
translation and in such a manner that they will be expressed
under appropriate conditions (e.g. in proper orientation and
correct reading frame and with appropriate targeting and
expression sequences) . The methods required to construct
these expression vectors are well known to those skilled in
the art .
A number of expression systems may be used to express the
polypeptide coding sequence. These include, but are not
limited to, bacteria, fungi (including yeast) , insect cell
systems, plant cell culture systems and plants all
transformed with the appropriate expression vectors.
Preferred hosts are those that are considered food grade -
generally regarded as safe' (GRAS) .
Suitable fungal species, include yeasts such as (but not
limited to) those of the genera Saccharomyces ,
Kluyveromyces Pichia, Hansenula , Candida, Schizo
saccharomyces and the like, and filamentous species such as
(but not limited to) those of the genera Aspergillus ,
Trichoderma , Mucor, Neurospora, Fusarium and the like.
The sequences encoding the hydrophobins are preferably at
least 80% identical at the amino acid level to a hydrophobin
identified in nature, more preferably at least 95% or 100%
identical. However, persons skilled in the art may make
conservative substitutions or other amino acid changes that
do not reduce the biological activity of the hydrophobin.
For the purpose of the invention these hydrophobins
possessing this high level of identity to a hydrophobin that
naturally occurs are also embraced within the term
"hydrophobins" .
Hydrophobins can be purified from culture media or cellular
extracts by, for example, the procedure described in
WO01/57076 which involves adsorbing the hydrophobin present
in a hydrophobin-containing solution to surface and then
contacting the surface with a surfactant, such as Tween 20,
to elute the hydrophobin from the surface. See also Collen
et al ., 2002, Biochim Biophys Acta. 1569: 139-50; Calonje et
al., 2002, Can. J . Microbiol. 48: 1030-4; Askolin et al .,
2001, Appl Microbiol Biotechnol. 57: 124-30; and De Vries et
al., 1999, Eur J Biochem. 262: 377-85.
Typically, the hydrophobin is in an isolated form, typically
at least partially purified, such as at least 10% pure,
based on weight of solids. By "isolated form", we mean that
the hydrophobin is not added as part of a naturallyoccurring
organism, such as a mushroom, which naturally
expresses hydrophobins. Instead, the hydrophobin will
typically either have been extracted from a naturallyoccurring
source or obtained by recombinant expression in a
host organism.
Hydrophobin proteins can be divided into two classes: Class
I , which are largely insoluble in water, and Class II, which
are readily soluble in water.
Preferably, the hydrophobins chosen are Class II
hydrophobins . More preferably the hydrophobins used are
Class II hydrophobins such as HFBI, HFBII, HFBIII, or Cerato
ulmin .
The hydrophobin can be from a single source or a plurality
of sources e.g. a mixture of two or more different
hydrophobins .
The total amount of hydrophobin in compositions of the
invention will generally be at least 0.001%, more preferably
at least 0.005 or 0.01%, and generally no greater than 2% by
total weight hydrophobin based on the total weight of the
composition .
Product Form
A preferred type of product form in the context of the
present invention is a dentifrice. The term "dentifrice"
denotes formulations which are used to clean the surfaces of
the oral cavity. The dentifrice is an oral composition that
is not intentionally swallowed for purposes of systemic
administration of therapeutic agents, but is retained in the
oral cavity for a sufficient time to contact substantially
all of the dental surfaces and/or mucosal tissues for
purposes of oral activity. Preferably the dentifrice is
suitable for application with a toothbrush and is rinsed off
after use. Preferably the dentifrice is in the form of a
paste or a gel (or a combination thereof) .
A dentifrice composition according to the invention will
generally contain further ingredients to enhance performance
and/or consumer acceptability such as water, humectant, and
binder or thickening agent.
For example, the dentifrice will usually contain a liquid
phase in an amount of from 40 to 99% by weight based on the
total weight of the dentifrice. Such a liquid phase
typically comprises water and a humectant in various
relative amounts, with the amount of water generally ranging
from 10 to 45% by weight (based on the total weight of the
dentifrice) and the amount of humectant generally ranging
from 30 to 70% by weight (based on the total weight of the
dentifrice) . Typical humectants include glycerol, sorbitol,
polyethylene glycol, polypropylene glycol, propylene glycol,
xylitol (and other edible polyhydric alcohols) , hydrogenated
partially hydrolyzed polysaccharides and mixtures thereof.
Furthermore, the dentifrice will usually contain a binder or
thickening agent in an amount of from 0.5 to 10% by weight
based on the total weight of the dentifrice. Suitable
binders or thickening agents include carboxyvinyl polymers
(such as polyacrylic acids cross-linked with polyallyl
sucrose or polyallyl pentaerythritol ), hydroxyethyl
cellulose, hydroxypropyl cellulose, water soluble salts of
cellulose ethers (such as sodium carboxymethyl cellulose and
sodium carboxymethyl hydroxyethyl cellulose) , natural gums
(such as carrageenan, gum karaya, guar gum, xanthan gum, gum
arabic, and gum tragacanth) , finely divided silicas,
hectorites, colloidal magnesium aluminium silicates and
mixtures thereof.
Optional Ingredients
Flavouring agents are generally used in oral care
compositions (such as dentifrices) at levels up to about 5%
by weight based on the total weight of the composition.
Commonly used flavouring agents are peppermint oil,
spearmint oil, oil of wintergreen and mixtures thereof. A
number of other flavouring agents have been suggested for
use in oral products including sassafras, clove, sage,
eucalyptus, marjoram, cinnamon, lemon and orange.
Mixtures of any of the above described flavouring agents may
also be used.
Advantageously, we have found that in compositions of the
invention, the level of flavouring agent may be reduced
without significant loss of flavour impact.
Accordingly, the total amount of flavouring agent in
compositions of the invention preferably ranges from 0 to
1.5% by total weight flavouring agent based on the total
weight of the composition. More preferably the total amount
of flavouring agent ranges from 0.1 to 1.0% by total weight
flavouring agent based on the total weight of the
composition. This provides the optimum balance between
formulation cost and flavour impact.
Compositions of the present invention may also contain
further optional ingredients customary in the art, such as
fluoride ion sources, anticalculus agents, buffers,
sweetening agents, colouring agents, opacifying agents,
preservatives, antisensitivity agents and antimicrobial
agents .
The invention is further illustrated with reference to the
following, non-limiting Examples.
EXAMPLES
Ob ective
A study was carried out to compare formulations according to
the present invention with formulations according to US
4,301,141, which describes the use of gelatin or gelatin
hydrolysate to produce mild foaming toothpastes.
Formulations
Toothpastes were prepared having ingredients as follows:
Examples 1 and 2 (according to the invention)
Ingredient Example 1 Example 2
(% w/w) (% w/w)
Sorbitol 65.4 45.0
Sodium saccharin 0.3 0.2
Polyethylene glycol 1500 2 .0 2 .0
Sodium fluoride 0.2 0.3
Abrasive silica 8.5 8.0
Thickening silica 9.0 10 .0
Sodium carboxymethyl cellulose 0.6 0.7
Titanium dioxide - 1.0
Zinc citrate - 2 .0
Hydrophobin* 0.1 0.1
Sodium lauryl sulphate 0.75 0.75
Flavour 0.6 0.6
Water to 100 to 100
Comparative Examples A and B (according to Examples 1 and 2
respectively of US 4,301,141)
Ingredient Example A Example B
(% w/w) (% w/w)
Sorbitol 12 .0 12 .0
Calcium carbonate 25.0 25.0
Thickening silica 2 .0 2 .0
Sodium carboxymethyl cellulose 0.8 1.0
Sodium salt of p-hydroxybenzoic 0.2 0.2
acid methyl ester
Sodium lauryl sulphate 2 .0 1.5
Sodium myristoyl taurate 0.5 0.5
Gelatin 3.0 -
Gelatin hydrolysate - 3.5
Flavour 2 .0 2 .0
Water to 100 to 100
Example 3 (according to the invention)
[* The specific hydrophobin used was Class II Hydrophobin
HFBII, obtained from VTT Biotechnology, Finland. It had been
purified from Trichoderma reesei essentially as described in
WO00/58342 and Linder et al ., 2001, Biomacromolecules 2 :
511-517.]
Foaming Evaluation
Samples of each toothpaste were foamed by taking 2 g of the
paste in 30ml sterilin, diluting it with 4 mL of de-ionised
water and vigorously shaking by hand for 90 seconds.
Results and Conclusions
It was noted that both Comparative Example A and Comparative
Example B immediately phase separated on storage. It was
also observed that the texture of these formulations was
slimy and "jelly-like".
By contrast, no stability or textural negatives were
observed for any of Examples 1 to 3 according to the
invention .
The foaming results are shown below in Table 1.
Table 1
It can be seen that all of Examples 1 to 3 produced
significantly more foam than either Comparative Example A or
Comparative Example B .
A non-aerated, foamable oral care composition
comprising less than 1.5% anionic surfactant (by total
weight anionic surfactant based on the total weight of
the composition) , abrasive cleaning agent and
hydrophobin .
A non-aerated, foamable oral care composition according
to claim 1 , where the hydrophobin is a Class II
hydrophobin .
A non-aerated, foamable oral care composition according
to claim 2 , where the Class II hydrophobin is HFBI,
HFBII, or a mixture thereof.
An oral care composition according to any one of claims
1 to 3 , in which the amount of anionic surfactant
ranges from 0.25 to 1.0% by total weight anionic
surfactant based on the total weight of the
composition .
An oral care composition according to any one of claims
1 to 4 , in which the abrasive cleaning agent is
selected from abrasive silicas, calcium carbonates and
mixtures thereof.
An oral care composition according to any one of claims
1 to 5 , in which the amount of abrasive cleaning agent
ranges from 3 to 75% by total weight abrasive cleaning
agent based on the total weight of the composition.
7 . An oral care composition according to any one of claims
1 to 6 , in which the amount of hydrophobin ranges from
0.01% to 2% by total weight hydrophobin based on the
total weight of the composition.
8 . An oral care composition according to any one of claims
1 to 7 , which is in the form of a dentifrice and which
comprises water, humectant, and binder or thickening
agent .
9 . An oral care composition according to any one of
claims 1 to 8 , which further comprises a flavouring
agent in an amount ranging from 0.1 to 1.0% by total
weight flavouring agent based on the total weight of
the composition.
10. The use of hydrophobin for boosting mildness in a nonaerated,
foamable oral care composition.