U.S. patent application number 09/789883 was filed with the patent office on 2002-10-24 for cubic liquid crystalline compositions and methods for their preparation.
Invention is credited to Lynch, Matthew Lawrence, Spicer, Patrick Thomas.
Application Number | 20020153508 09/789883 |
Document ID | / |
Family ID | 26909708 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020153508 |
Kind Code |
A1 |
Lynch, Matthew Lawrence ; et
al. |
October 24, 2002 |
Cubic liquid crystalline compositions and methods for their
preparation
Abstract
Cubic liquid crystalline gel precursors, bulk cubic liquid
crystalline gels, and dispersions of cubic liquid crystalline gel
particles, and methods for their preparation, are disclosed. The
precursors, gels, and dispersions can be used as skin penetration
enhancers. The precursors, gels, and dispersions are prepared by
methods employing hydrotropes that do not detrimentally affect the
cubic liquid crystalline structure of the gels and particles.
Inventors: |
Lynch, Matthew Lawrence;
(Cincinnati, OH) ; Spicer, Patrick Thomas;
(Cincinnati, OH) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY
INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Family ID: |
26909708 |
Appl. No.: |
09/789883 |
Filed: |
February 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60215113 |
Jun 29, 2000 |
|
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|
Current U.S.
Class: |
252/299.01 ;
252/299.5 |
Current CPC
Class: |
A61K 9/1274 20130101;
A61P 1/02 20180101; A61Q 19/00 20130101; Y10S 514/937 20130101;
C09K 19/54 20130101; Y10S 514/964 20130101; C09K 2019/528 20130101;
A01N 25/04 20130101; C09K 19/00 20130101; A61K 8/0295 20130101 |
Class at
Publication: |
252/299.01 ;
252/299.5 |
International
Class: |
C09K 019/52; C09K
019/54 |
Claims
What is claimed is:
1. A cubic gel precursor comprising: (A) a hydrotrope, (B) an
amphiphile capable of forming a cubic liquid crystalline phase, and
optionally (C) a solvent, wherein ingredients (A), (B), and (C) are
present in mass fractions relative to each other such that
1.0=a+b+c wherein a is the mass fraction of ingredient (A), b is
the mass fraction of ingredient (B), and c is the mass fraction of
ingredient (C), and wherein 1.0>a>0, 1.0>b>0,
1.0>c.gtoreq.0; and with the proviso that a, b, and c do not
fall within a cubic liquid crystalline phase region on a phase
diagram representing phase behavior of ingredients (A), (B), and
(C).
2. The precursor of claim 1, wherein 0.5.gtoreq.a.gtoreq.0.05,
0.8.gtoreq.b.gtoreq.0.1, and 0.8.gtoreq.c.gtoreq.0.
3. The precursor of claim 1, wherein ingredient (A) is selected
from the group consisting of low molecular weight alcohols;
polyols; alcohol ethoxylates; surfactants derived from mono- and
poly-saccharides; copolymers of ethylene oxide and propylene oxide;
fatty acid ethoxylates; sorbitan derivatives; sodium butyrate;
nicotinamide; procaine hydrogen chloride; and ethylene glycol,
propylene glycol, glycerol, and polyglyceryl esters, and the
ethoxylated derivatives thereof; and combinations thereof.
4. The precursor of claim 1, wherein ingredient (B) is a
monoglyceride having the formula: 2wherein R is selected from the
group consisting of monovalent hydrocarbon groups of 6 to 22 carbon
atoms, and monovalent halogenated hydrocarbon groups of 6 to 22
carbon atoms.
5. The precursor of claim 1, wherein ingredient (C) is a polar
solvent selected from the group consisting of water, glycerol,
glycols, formamides, ethylammonium nitrate, and combinations
thereof.
6. A bulk cubic liquid crystalline gel comprising: (A) a
hydrotrope, (B) an amphiphile capable of forming a cubic liquid
crystalline phase, and (C) a solvent, wherein ingredients (A), (B),
and (C) are present in mass fractions relative to each other such
that 1.0=a+b+c wherein a is the mass fraction of ingredient (A), b
is the mass fraction of ingredient (B), and c is the mass fraction
of ingredient (C), and wherein 1.0>a>0, 1.0>b>0,
1.0>c>0; and with the proviso that a, b, and c fall within a
cubic liquid crystalline phase region on a phase diagram
representing phase behavior of ingredients (A), (B), and (C).
7. The gel of claim 6, wherein 0.1.gtoreq.a.gtoreq.0.005,
0.75.gtoreq.b.gtoreq.0.45, and 0.6.gtoreq.c.gtoreq.0.1.
8. The gel of claim 6, wherein ingredient (A) is selected from the
group consisting of low molecular weight alcohols; polyols; alcohol
ethoxylates; surfactants derived from mono- and poly-saccharides;
copolymers of ethylene oxide and propylene oxide; fatty acid
ethoxylates; sorbitan derivatives; sodium butyrate; nicotinamide;
procaine hydrogen chloride; and ethylene glycol, propylene glycol,
glycerol, and polyglyceryl esters, and the ethoxylated derivatives
thereof; and combinations thereof.
9. The gel of claim 6, wherein ingredient (B) is a monoglyceride
having the formula: 3wherein R is selected from the group
consisting of monovalent hydrocarbon groups of 6 to 22 carbon
atoms, and monovalent halogenated hydrocarbon groups of 6 to 22
carbon atoms.
10. The gel of claim 6, wherein ingredient (C) is a polar solvent
selected from the group consisting of water, glycerol, glycols,
formamides, ethylammonium nitrate, and combinations thereof.
11. A dispersion comprising: (A) a hydrotrope, (B) an amphiphile
capable of forming a cubic liquid crystalline phase, and (C) a
solvent, wherein ingredients (A), (B), and (C) are present in mass
fractions relative to each other such that 1.0=a+b+c wherein a is
the mass fraction of ingredient (A), b is the mass fraction of
ingredient (B), and c is the mass fraction of ingredient (C), and
wherein 1.0>a>0, 1.0>b>0, 1.0>c>0; and with the
proviso that a, b, and c fall within a region representing cubic
liquid crystalline phase in combination with at least one other
phase on a phase diagram representing phase behavior of ingredients
(A), (B), and (C), with the proviso that the dispersion is formed
as cubic liquid crystalline gel particulates dispersed in the other
phase.
12. The dispersion of claim 11, wherein 0.1.gtoreq.a.gtoreq.0.005,
0.3.gtoreq.b.gtoreq.0.03, and 0.9.gtoreq.c.gtoreq.0.6.
13. The dispersion of claim 11, wherein ingredient (A) is selected
from the group consisting of: low molecular weight alcohols;
polyols; alcohol ethoxylates; surfactants derived from mono- and
poly-saccharides; copolymers of ethylene oxide and propylene oxide;
fatty acid ethoxylates; sorbitan derivatives; sodium butyrate;
nicotinamide; procaine hydrogen chloride; and ethylene glycol,
propylene glycol, glycerol, and polyglyceryl esters, and the
ethoxylated derivatives thereof; and combinations thereof.
14. The dispersion of claim 11, wherein ingredient (B) is a
monoglyceride having the formula: 4wherein R is selected from the
group consisting of monovalent hydrocarbon groups of 6 to 22 carbon
atoms, and monovalent halogenated hydrocarbon groups of 6 to 22
carbon atoms.
15. The dispersion of claim 11, wherein ingredient (C) is a polar
solvent selected from the group consisting of water, glycerol,
glycols, formamides, ethylammonium nitrate, and combinations
thereof.
16. The dispersion of claim 11, further comprising (D) a
stabilizer.
17. Cubic liquid crystalline gel particles comprising: (A) a
hydrotrope, (B) an amphiphile capable of forming a cubic liquid
crystalline phase, (C) a solvent, and (D) a stabilizer, wherein
ingredients (A), (B), and (C) are present in relative mass
fractions relative to each other such that 1.0=a+b+c wherein a is
the mass fraction of ingredient (A), b is the mass fraction of
ingredient (B), and c is the mass fraction of ingredient (C), and
wherein 1.0>a>0, 1.0>b>0, 1.0>c>0; and with the
provisos that a, b, and c fall within a cubic liquid crystalline
phase region on a phase diagram representing phase behavior of
ingredients (A), (B), and (C), and that ingredients (A), (B), and
(C) have a particulate form.
18. The particles of claim 17, wherein ingredient (A) is selected
from the group consisting of low molecular weight alcohols;
polyols; alcohol ethoxylates; surfactants derived from mono- and
poly-saccharides; copolymers of ethylene oxide and propylene oxide;
fatty acid ethoxylates; sorbitan derivatives; sodium butyrate;
nicotinamide; procaine hydrogen chloride; and ethylene glycol,
propylene glycol, glycerol, and polyglyceryl esters, and the
ethoxylated derivatives thereof; and combinations thereof.
19. The particles of claim 17, wherein ingredient (B) is a
monoglyceride having the formula: 5wherein R is selected from the
group consisting of monovalent hydrocarbon groups of 6 to 22 carbon
atoms, and monovalent halogenated hydrocarbon groups of 6 to 22
carbon atoms.
20. The particles of claim 17, wherein ingredient (C) is a polar
solvent selected from the group consisting of water, glycerol,
glycols, formamides, ethylammonium nitrate, and combinations
thereof.
21. A method for preparing a cubic gel precursor comprising the
steps of: 1) combining (A) a hydrotrope with (B) an amphiphile
capable of forming a cubic liquid crystalline phase, and 2)
optionally adding (C) a solvent, wherein ingredients (A), (B), and
(C) are combined in mass fractions relative to each other such that
1.0=a+b+c wherein a is the mass fraction of ingredient (A), b is
the mass fraction of ingredient (B), and c is the mass fraction of
ingredient (C), and wherein 1.0>a>0, 1.0>b>0,
1.0>c.gtoreq.0; and with the proviso that a, b, and c do not
fall within a cubic liquid crystalline phase region on a phase
diagram representing phase behavior of ingredients (A), (B), and
(C), and with the proviso that amounts of each ingredient in the
composition are such that cubic phase gel forms upon occurrence of
a stimulus.
22. The method of claim 21, wherein ingredient (B) is a liquid, and
ingredients (A) and (B) are combined by mixing.
23. The method of claim 21, wherein ingredient (B) is a solid, and
ingredients (A) and (B) are combined by a method selected from the
group consisting of: (a) heating ingredient (B) to a temperature
greater than its melting point and then mixing ingredient (B) with
ingredient (A), (b) fragmenting ingredient (B) into solid particles
and thereafter combining ingredient (B) with ingredient (A), (c)
dissolving ingredient (A) in an aqueous hydrotrope solution, and
combining the solution with ingredient (B).
24. The method of claim 21, wherein step 2) is carried out at a
time selected from the group consisting of during and after step
1).
25. The method of claim 21, further comprising: 3) applying the
stimulus.
26. The method of claim 25, wherein the stimulus is selected from
the group consisting of: (a) addition of a specified material
selected from the group consisting of additional hydrotrope,
amphiphile, and solvent, (b) removal of a material selected from
the group consisting of a portion of the hydrotrope, amphiphile,
and solvent, (c) a temperature change, (d) a pH change, (e)
addition of a salt, (f) a pressure change, and (g) combinations
thereof.
27. The method of claim 25, further comprising: 4) removing the
hydrotrope after step 3).
28. A method for preparing a cubic liquid crystalline gel
composition comprising the steps of: 1) combining in a composition,
ingredients comprising (A) a hydrotrope and (B) an amphiphile
capable of forming a cubic liquid crystalline phase, and 2) mixing
the product of step 1) with (C) a solvent, wherein ingredients (A),
(B), and (C) are combined in mass fractions relative to each other
such that 1.0=a+b+c wherein a is the mass fraction of ingredient
(A), b is the mass fraction of ingredient (B), and c is the mass
fraction of ingredient (C), and wherein 1.0>a>0,
1.0>b>0, 1.0>c>0; and with the proviso that a, b, and c
fall within a cubic liquid crystalline phase region on a phase
diagram representing phase behavior of ingredients (A), (B), and
(C).
29. The method of claim 28, wherein step 1) is carried out by a
method selected from the group consisting of: a) heating ingredient
(B) to a temperature greater than its melting point and then mixing
with the hydrotrope, b) fragmenting ingredient (B) into solid
particles and combining the solid particles with the hydrotrope,
and c) dissolving ingredient (A) in an aqueous hydrotrope solution,
and combining the solution with ingredient (B).
30. The method of claim 28, wherein step 2) is carried out at a
time selected from the group consisting of during and after step
1).
31. The method of claim 28, further comprising: 3) removing the
hydrotrope after step 2).
32. A method for preparing a dispersion of cubic gel particles
directly from a precursor comprising the steps of: 1) dispersing a
cubic gel precursor comprising: (A) a hydrotrope, (B) an amphiphile
capable of forming a cubic liquid crystalline phase, and optionally
(C) a solvent, wherein ingredients (A), (B), and (C) are present in
mass fractions relative to each other such that 1.0=a+b+c wherein a
is the mass fraction of ingredient (A), b is the mass fraction of
ingredient (B), and c is the mass fraction of ingredient (C), and
wherein 1.0>a>0, 1.0>b>0, 1.0>c.gtoreq.0; and with
the proviso that a, b, and c do not fall within a cubic liquid
crystalline phase region on a phase diagram representing phase
behavior of ingredients (A), (B), and (C) wherein dispersing is
carried out by a method selected from the group consisting of a)
dispersing the precursor in additional (C) solvent, and b)
dispersing additional (C) solvent in the precursor, and thereafter
diluting.
33. The method of claim 32, wherein step 1a) is carried out by a
method selected from the group consisting of: i) applying fluid
shear, ii) applying ultrasonic waves, iii) extruding through a
small pore membrane, iv) cross membrane emulsifying, v) impinging
from opposing jets of a stream of the precursor and a stream of
solvent, and vi) combining streams of solvent and the precursor in
a micro-mixer.
34. The method of claim 32, wherein step 1b) is carried out by a
method selected from the group consisting of: i) spraying a fine
mist of the precursor into an environment comprising solvent
vapors, and thereafter diluting; ii) bubbling vaporized solvent
into the precursor, and thereafter diluting.
35. The method of claim 32, further comprising: 2) stabilizing the
product of step 1).
36. The method of claim 35, wherein step 2) is carried out by a
method selected from the group consisting of: a) adding (D) a
stabilizer, b) forming a coating of lamellar liquid crystalline
phase on surfaces of particles formed in step 1) c) directly
dispersing the product of step 1) into a viscous matrix comprising
the stabilizer and solvent.
37. The method of claim 35, wherein steps 1) and 2) are combined by
adding (D) the stabilizer to (C) the solvent to form a stabilizing
composition and thereafter combining the stabilizing composition
with the product of step 1).
38. The method of claim 35, further comprising the step of: 3)
removing ingredient (A) after step 2).
39. The method of claim 32, wherein the precursor is diluted prior
to step 1).
40. The method of claim 38, further comprising the step of: 4)
isolating the particles during or after step 3).
41. A method for preparing a dispersion of cubic liquid crystalline
gel particles comprising fragmenting a bulk cubic liquid
crystalline gel comprising: (A) a hydrotrope, (B) an amphiphile
capable of forming a cubic liquid crystalline phase, and (C) a
solvent, wherein ingredients (A), (B), and (C) are present in mass
fractions relative to each other such that 1.0=a+b+c wherein a is
the mass fraction of ingredient (A), b is the mass fraction of
ingredient (B), and c is the mass fraction of ingredient (C), and
wherein 1.0>a>0, 1.0>b>0, 1.0>c>0; and with the
proviso that a, b, and c fall within a cubic liquid crystalline
phase region on a phase diagram representing phase behavior of
ingredients (A), (B), and (C).
42. The method of claim 41, wherein fragmenting can be carried out
by a method selected from the group consisting of: a) subjecting
the bulk cubic liquid crystalline gel to fluid shear, b)
ultrasonication, c) dispersal in a micromixer, and d) membrane
emulsification.
43. The method of claim 41, further comprising the step of:
isolating the particles after fragmentation.
44. A method for preparing dispersions of cubic liquid crystalline
gel particles comprising the steps of: 1) heating (B) a solid
amphiphile capable of forming a cubic liquid crystalline phase to a
temperature greater than or equal to its melting point, 2)
combining the product of step 1) with (A) a hydrotrope, 3) adding
(C) water, wherein ingredients (A), (B), and (C) are present in
mass fractions relative to each other such that 1.0=a+b+c wherein a
is the mass fraction of ingredient (A), b is the mass fraction of
ingredient (B), and c is the mass fraction of ingredient (C), and
wherein 1.0>a>0, 1.0>b>0, 1.0>c.gtoreq.0; and with
the proviso that a, b, and c fall within an isotropic liquid phase
region on a phase diagram representing phase behavior of
ingredients (A), (B), and (C) 4) forming a dispersion by a route
selected from the group consisting of i) dispersing the product of
step 3) into (C) the water, and thereafter stabilizing; ii)
spraying the isotropic liquid into a humid environment, diluting
with sufficient water to form a colloidally unstable dispersion of
cubic gel particles, and thereafter stabilizing; iii) diluting the
isotropic liquid with sufficient water to form an interfacially
stabilized emulsion phase, sterically stabilizing said emulsion
phase, and thereafter, further diluting with additional water; and
iv) dispersing water into the isotropic liquid, further diluting
with sufficient water to form an unstable particle dispersion, and
thereafter stabilizing.
45. The method of claim 44, further comprising the step of: 4)
removing ingredient (A) after step 3).
46. The method of claim 45, further comprising the step of: 5)
isolating the particles.
47. A method for manufacturing a cubic liquid crystalline phase
material comprising the steps of: 1) preparing a precursor
comprising (A) a hydrotrope, (B) an amphiphile capable of forming a
cubic liquid crystalline phase, and optionally (C) a solvent,
wherein ingredients (A), (B), and (C) are present in mass fractions
relative to each other such that 1.0=a+b+c wherein a is the mass
fraction of ingredient (A), b is the mass fraction of ingredient
(B), and c is the mass fraction of ingredient (C), and wherein
1.0>a>0, 1.0>b>0, 1.0>c.gtoreq.0; and with the
proviso that a, b, and c fall at a starting point on a phase
trajectory within an isotropic liquid region on a phase diagram
representing phase behavior of ingredients (A), (B), and (C); 2)
diluting the product of step 1) with ingredient (C) until an end
point is reached on the phase trajectory, wherein the end point
lies on a tie line between the isotropic liquid region and a cubic
phase containing region on the phase diagram.
48. A method for delivering an active ingredient to a substrate
comprising: 1) preparing a cubic gel precursor comprising: (A) a
hydrotrope, (B) an amphiphile capable of forming a cubic liquid
crystalline phase, (C) a solvent, and (D) an active ingredient,
wherein ingredients (A), (B), and (C) are combined in mass
fractions relative to each other such that 1.0=a+b+c wherein a is
the mass fraction of ingredient (A), b is the mass fraction of
ingredient (B), and c is the mass fraction of ingredient (C), and
wherein 1.0>a>0, 1.0>b>0, 1.0>c.gtoreq.0; and with
the proviso that a, b, and c fall within an isotropic liquid region
on a phase diagram representing phase behavior of ingredients (A),
(B), and (C), and with the proviso that amounts of each ingredient
in the composition are such that cubic phase gel forms upon
occurrence of a stimulus; and 2) spraying the precursor onto a
substrate.
49. The method of claim 48, wherein the active ingredient is an
agrochemical and the substrate is a plant surface.
Description
FIELD OF THE INVENTION
[0001] This invention relates to cubic liquid crystalline
compositions, precursors thereof, and methods for their
preparation. More particularly, this invention relates to improved
methods for preparing dispersions of cubic liquid crystalline gel
particles.
BACKGROUND OF THE INVENTION
[0002] "Amphiphilic substance" means a molecule with both
hydrophilic and hydrophobic (lipophilic) groups. Amphiphilic
substances spontaneously self-associate in aqueous systems forming
various types of aggregates. Examples of these aggregates include
lamellar phases, hexagonal phases, and cubic phases. These phases
are thermodynamically stable. The long-range order in these phases,
in combination with liquid-like properties in the short-range
order, gave rise to the notation "liquid crystalline phases".
Cubic Gel Precursors
[0003] Liquid crystalline phases (i.e., bulk cubic liquid
crystalline gels and dispersions of cubic liquid crystalline gel
particles) can be formed from precursors including an amphiphilic
molecule such as a lipid and a polar liquid. The cubic liquid
crystalline gel phase structures can form in response to some
event, such as a temperature change or dilution of the precursor.
In some applications, a cubic gel precursor forms a bulk cubic
liquid crystalline gel only when needed for the specific
application. For example, precursors have been used in
antiperspirants, in which a water-insoluble liquid crystalline
phase forms when the precursor contacts sweat (salt water). The
resulting bulk liquid crystalline gel has a cubic or hexagonal
liquid crystal structure that blocks pores. Precursors have also
been used to deliver a therapeutic agent to treat periodontal
disease, for example, by putting the precursor comprising a
monoglyceride and an active ingredient into a reservoir such as a
periodontal pocket. The precursor forms bulk cubic liquid
crystalline gel on contact with saliva and then provides controlled
release of the therapeutic agent.
[0004] However, in these applications, some uncontrolled stimulus
(such as sweating or salivating) is always required for the
precursor to form bulk cubic liquid crystalline gel. No control can
be exercised over the properties of the bulk cubic liquid
crystalline gel formed. Furthermore, particulate cubic liquid
crystalline gel cannot be formed directly from the precursor.
Therefore, it is an object of this invention to provide precursors
that can directly form either bulk or particulate cubic liquid
crystalline gels. It is a further object of this invention to
provide a method for using the precursor to prepare bulk and
particulate cubic liquid crystalline gels with controlled
properties.
Bulk Cubic Liquid Crystalline Gel
[0005] The liquid crystalline phases have distinct hydrophilic and
hydrophobic domains, which give them the ability to dissolve
(solubilize) or disperse water-soluble, oil-soluble, and
amphiphilic compounds. Liquid crystalline phases are highly ordered
structures that restrict the diffusion of added ingredients,
thereby making them useful for controlled-release purposes. Cubic
liquid crystalline phases can be prepared as pastes and thus are
particularly useful as delivery vehicles due to their rheological
properties. Cubic liquid crystalline phases are also advantageous
in that they are mechanically robust and resistant to physical
degradation.
[0006] Bulk cubic liquid crystalline gels prepared in advance
(i.e., before administration rather than in situ, as in the
treatment of periodontal disease described above) can also be used
as controlled release reservoirs of pharmaceutical materials.
However, bulk cubic liquid crystalline gels are typically difficult
to prepare due to the properties of the raw materials and
Theological properties of the gels themselves. Lipids that yield
cubic liquid crystalline phases, such as monoglycerides, are
typically waxy solids at room temperature. Therefore, the bulk
cubic liquid crystalline gel is prepared by equilibrating at high
temperature or over many hours, or both, because transport of water
is slow through solid lipids. Processes that require long hold
times at high temperatures to manufacture bulk cubic liquid
crystalline gels are not economically practical, particularly on a
commercial scale. Therefore, it is a further object of this
invention to provide a method for forming a bulk cubic liquid
crystalline gel at relatively low temperature (e.g., room
temperature) and in a relatively short amount of time (e.g., within
minutes). It is a further object of this invention to provide an
economical and practical method for preparing commercial scale
quantities of bulk cubic liquid crystalline gels.
[0007] Bulk cubic liquid crystalline phases are high-viscosity
solid-like gels, which makes large-scale processing to form
dispersed particles of cubic liquid crystalline phase difficult.
Large scale processing of bulk solid and solid-like materials is
difficult because of problems associated with adequate mixing and
homogenizing. High energy input is required, and this energy can
degrade liquid crystalline structures. For example, high energy
input processes, such as those employing high shear can physically
degrade crystalline structures. High energy input processes, such
as those employing high temperatures can chemically degrade the
compounds making up the liquid crystalline structures. Furthermore,
high energy input processes are costly and require more precise
control and maintenance. Therefore, it is an object of this
invention to provide methods for preparing cubic liquid crystalline
phase materials that are less costly and more efficient than the
methods involving bulk solid processing.
Dispersed Cubic Liquid Crystalline Gel Particles
[0008] Lamellar phases have a bilayer sheet structure. When a
lamellar phase is dispersed in excess water, the lamellar phase
forms vesicles and liposomes. "Vesicle" means an enclosed shell
comprised of one bilayer of amphiphilic molecules. "Liposome" means
an enclosed shell comprised of more than one bilayer of amphiphilic
molecules. Vesicles and liposomes can be spheroidal, ellipsoidal,
or irregularly shaped; however, spheroidal shells are the most
stable.
[0009] Vesicles and liposomes suffer from the drawback that they
are non-equilibrium states, which means that, inevitably, they will
degrade. Furthermore, vesicles and liposomes are relatively
expensive to manufacture. Therefore, it is an object of this
invention to provide a stable, less expensive alternative to
vesicles and liposomes.
[0010] Bulk cubic liquid crystalline gel can also be dispersed to
form particles. Dispersed particles of cubic liquid crystalline
phases are structurally distinct from vesicles and liposomes.
Dispersed cubic gel particles have a cubic or spherical outer
structure with a bicontinuous cubic internal structure. The
bicontinuous cubic internal structure has distinct hydrophilic and
lipophilic domains, and is described in S. Hyde et al., The
Language of Shape, Elsevier, Amsterdam, 1997, chapters 1 and 4.
[0011] Typically, cubic liquid crystalline gel particles are formed
via fragmentation and dispersion of homogeneous bulk cubic liquid
crystalline gel. Fragmentation is carried out in combination with a
fragmentation agent such as polysaccharides, proteins, amphiphilic
macromolecules and lipids, amphiphilic polymers, and amphiphilic
compounds. Fragmentation also requires the use of a high energy
input process by, for example, high shear milling or
sonication.
[0012] Fragmenting and dispersing solid and solid-like materials,
such as bulk cubic liquid crystalline gel, are difficult and
impractical above very small processing scales (e.g., on the order
of several grams, or less) without significant energy input and
hold time. This makes commercial scale production of dispersed
cubic gels expensive and impractical. Furthermore, high energy
input processes can create non-equilibrium structures, such as
vesicles and liposomes. Therefore, it is an object of this
invention to develop a means for producing dispersed cubic liquid
crystalline gel particles that does not require a fragmentation
step. It is a further object of this invention to provide a method
for forming cubic gel particles instantaneously by homogeneous
nucleation upon dilution. It is a further object of this invention
to provide an economical and practical method for preparing
commercial scale quantities of cubic liquid crystalline gel
particle dispersions.
SUMMARY OF THE INVENTION
[0013] It has been surprisingly found that cubic liquid crystalline
phase gels can be prepared in the presence of a hydrotrope.
(Hydrotropes are perversely well-known for their efficiency at
disrupting liquid crystalline materials, see Pearson, J. T., Smith,
J. M., "The Effect of Hydrotropic Salts on the Stability of Liquid
Crystalline Systems," J. Pharn. Pharmac., 26, 123-124 (1974).) This
invention relates to compositions that can be in the form of a
cubic gel precursor, a bulk cubic liquid crystalline gel, or a
dispersion of cubic liquid crystalline gel particles. The precursor
comprises: (A) a hydrotrope and (B) an amphiphile that is capable
of forming cubic liquid crystalline phase structures. The bulk
cubic liquid crystalline gel comprises ingredients (A), (B) and (C)
a solvent. The dispersed cubic liquid crystalline gel particles
comprise ingredients (A), (B), (C), and preferably (D) a
stabilizer. This invention further relates to methods for preparing
the above compositions. The methods of this invention are
commercially advantageous in that bulk solids handling of
ingredient (B) can be eliminated when ingredient (B) is a solid at
room temperature, and the fragmentation step required by methods
for dispersing bulk liquid crystalline materials to form
dispersions of particles having liquid crystalline structures can
be eliminated by preparing dispersions of cubic gel particles
directly from the cubic gel precursor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a ternary phase diagram showing the phase behavior
of a system of monoolein, ethanol, and water.
[0015] FIG. 2 is a flow diagram of the method steps for the
preferred methods for preparing dispersions of cubic gel particles
according to this invention.
[0016] FIG. 3 is a ternary phase diagram showing the phase behavior
of ethanol, monoolein, and water.
[0017] FIG. 4 is a ternary phase diagram showing the phase behavior
of ethanol, monoolein, and water.
[0018] FIG. 5 is a ternary phase diagram showing the phase behavior
of 1,2-hexanediol, monoolein, and water.
[0019] FIG. 6 is a ternary phase diagram showing the phase behavior
of 1,2-hexanediol, monoolein, and water.
[0020] FIG. 7 is a ternary phase diagram showing the phase behavior
of ethanol, monoolein, and water.
[0021] FIG. 8a is a cryo-TEM image of a cubic gel particle prepared
according to Example 8 of this invention.
[0022] FIG. 8b is a cryo-TEM image of a cubic gel particle prepared
according to Example 12 of this invention.
[0023] FIG. 8c is a cryo-TEM image of cubic gel particles prepared
according to Example 18 of this invention.
[0024] FIG. 9 is a phase diagram showing the phase behavior of
ethanol, monoolein, and water in Example 6.
[0025] FIG. 10 is a phase diagram showing the phase behavior of
ethanol, monoolein, and water in Example 10.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Publications and patents are referred to throughout this
disclosure. All U.S. patents cited herein are hereby incorporated
by reference.
[0027] All percentages, ratios, and proportions used herein are by
weight unless otherwise specified. All measurements are made at
25.degree. C., unless otherwise specified.
Definition and Usage of Terms
[0028] The following is a list of definitions for terms, as used
herein:
[0029] "Amphiphile" means a molecule with both hydrophilic and
hydrophobic (lipophilic) groups (e.g, surfactants, lipids, and
polymers).
[0030] "Bulk cubic gel" means a viscous, structurally isotropic gel
(clear, translucent, or opaque) having a normal or reversed cubic
liquid crystalline structure, with a composition matching a cubic
liquid crystalline region of a phase diagram representing the phase
behavior of a hydrotrope, a surfactant, and a solvent. Bulk cubic
gel may also be referred to herein as bulk cubic liquid crystalline
gel.
[0031] "Colloidally stable" means that when cubic gel particles are
dispersed in a solvent, the particles do not coalesce, flocculate,
or agglomerate over time.
[0032] "Cubic gel precursor" means a formulation that will form a
cubic liquid crystalline phase upon action by a stimulus. The
stimulus can be the addition of some specified material such as
additional hydrotrope, amphiphile, or solvent; the removal of some
specified material such as a portion of the hydrotrope, amphiphile,
or solvent; a temperature change; a pressure change; addition of
salt; or a pH change in aqueous systems. Cubic gel precursor may
also be referred to herein as cubic liquid crystalline gel
precursor.
[0033] "Cubic gel particles" means the dispersed form of bulk cubic
gel; technically they are cubic liquid crystalline gel in
equilibrium with either the solvent, isotropic liquid phase,
lamellar phase, or a combination of two of these.
[0034] "Gel" means a rheologically semisolid system. Gel includes
cubic liquid crystalline materials such as bulk cubic gels and
dispersions of cubic gel particles.
[0035] "Hydrotrope" means a surfactant-type molecule (comprising at
least one hydrophilic group and at least one hydrophobic group),
wherein the molecule has too short or too soluble a hydrophobic
group or too insoluble or too large a hydrophilic group to display
surfactant phase behavior. Hydrotropes are highly soluble in water
and do not form aggregates in solution (e.g., micelles).
Hydrotropes dissolve amphiphiles. Hydrotropes do not prevent
formation of a cubic liquid crystalline phase upon dilution of a
mixture of the hydrotrope and amphiphile with a solvent. The
hydrotropes enhance the miscibility of weakly polar and otherwise
water-insoluble molecules (such as monoolein) with aqueous
solutions; this effect is commonly known as "salting-in". The
hydrotrope is typically present in a substantial concentration
(i.e., 1% or more) to display the hydrotropic properties described
above.
[0036] "L1" means a dilute liquid phase.
[0037] "L2" means a concentrated liquid phase.
[0038] "Lipid" means any amphiphilic molecule of intermediate
molecular weight that contains a substantial portion of aliphatic
or aromatic hydrocarbon.
[0039] "Paste" means a liquid for topical application, preferably
to the skin of an animal (preferably a human), whose viscosity is
enhanced to the point that flow is largely inhibited by the
presence of undissolved, as well as dissolved, solids.
[0040] "Stabilizer" means an agent that prevents aggregation,
coalescence, and flocculation of dispersed phase particles.
Stabilizers impart colloidal stability to dispersed cubic gel
particles. Stabilizers include polymers, small particulates that
absorb upon surfaces of the particles, ionic materials, and liquid
crystalline phase adsorbed to the surfaces of the particles.
[0041] "Surfactant" means an amphiphile that exhibits the following
properties in water: (1) it reduces the interfacial tension, and
(2) it self-assembles in solution at low concentrations.
[0042] "Thermodynamically stable" means that a system is at its
lowest energy state.
Compositions
[0043] This invention relates to cubic gel precursors, bulk cubic
gels, and cubic gel particles.
Cubic Gel Precursor
[0044] The cubic gel precursor comprises (A) a hydrotrope and (B)
an amphiphile. The precursor may optionally further comprise (C) a
solvent. The precursor must not form a cubic phase gel.
Hydrotrope
[0045] Ingredient (A) is a hydrotrope. The hydrotrope is capable of
dissolving (B) the amphiphile. The hydrotrope must not prevent
formation of a cubic liquid crystalline phase upon dilution of a
mixture of the hydrotrope and amphiphile with the solvent.
Preferred hydrotropes allow for formation of cubic gel particles
dispersed in isotropic liquid phases.
[0046] Suitable hydrotropes include alcohols; polyols; alcohol
ethoxylates; surfactants derived from mono- and poly-saccharides;
copolymers of ethylene oxide and propylene oxide; fatty acid
ethoxylates; sorbitan derivatives; sodium butyrate; nicotinamide;
procaine hydrogen chloride; and ethylene glycol, propylene glycol,
glycerol, and polyglyceryl esters, and the ethoxylated derivatives
thereof; combinations thereof; and others.
[0047] Examples of preferred hydrotropes include alcohols such as
methanol and ethanol and polyols such as 1,4-butanediol and
1,2-hexanediol. Preferred alcohols include ethanol. Preferred
polyols include 1,4-butanediol. Other preferred hydrotropes include
sodium butyrate, nicotinamide, and procaine hydrogen chloride.
Without wishing to be bound by theory, it is believed that the
hydrotrope must have sufficient hydrophilic character for cubic
liquid crystalline phase to form when the hydrotrope is present in
amounts up to about 10%.
[0048] Whether a compound is suitable to use as ingredient (A) can
be determined by one skilled in the art without undue
experimentation. The determination can be made by preparing a
composition comprising the compound to be tested for use as the
hydrotrope, the selected amphiphile, and the selected solvent and
allowing the composition to equilibrate, for example, by the method
described below in Reference Example 1. If the composition forms a
cubic phase or cubic phase in combination with another phase, then
the hydrotrope is suitable to use in this invention. If the
composition forms a cubic phase or cubic phase in combination with
an isotropic liquid, then the hydrotrope is preferred.
[0049] Polarized light microscopy (PLM) can be used to determine
whether the composition formed cubic phase. PLM can be carried out
on a polarized light microscope or constructed light box, as
described by Laughlin, R. G., J. Colloid Interface Sci., 55,
239-242 (1976). Polarized light microscope textures define the
phase/colloidal state of sample. Lamellar and hexagonal phases give
birefringence (see Hecht, E., Optics, 2.sup.nd ed., Addison-Wesley
Publishing Co., Reading, Mass., pp. 282-289 (1984)) and distinct
textures such as Maltese Crosses (see Rosevear, F. B., J. Am. Oil
Chemists Soc., 31, 628-638 (1954)). This is a consequence of the
anisotropic phase structure of these particular phases, and their
orientation relative to polarization of the light. However, L1, L2,
L3, and cubic phases show no birefringence and appear dark in the
microscope. Birefringence is a function of sample thickness, so
sometimes it is difficult to see with a light microscope. Instead,
the bulk sample can be placed in the aforementioned light box to
secure a very thick sample.
[0050] Cubic phases are very viscous while the other phases are
(i.e., L1, L2, and L3) are less viscous, like water. Therefore,
lack of birefringence in combination with bulk solid-like
theological properties indicates the presence of cubic phase.
Amphiphile Capable of Forming Cubic Liquid Crystalline Phase
[0051] Ingredient (B) is an amphiphile that is capable of forming a
cubic liquid crystalline phase. Ingredient (B) can be a single
amphiphile or a combination (e.g., mixture) of two or more
amphiphiles. Suitable amphiphiles are surfactants that must be
capable of forming cubic liquid crystalline phases in the presence
of ingredients (A) and (C) a solvent. Amphiphiles comprise a
hydrophilic group and a lipophilic group. Suitable hydrophilic
groups, and methods for the selection of suitable hydrophilic
groups, are disclosed in Laughlin, R. G., The Aqueous Phase
Behavior of Surfactants, Academic Press, New York, 1994, pp. 255;
and in International Patent Publication No. WO 99/12640 at page
12.
1TABLE 1 Anionic Hydrophilic Groups Functional Group General
Formula Alkyl carboxylate salts RCO.sub.2.sup.-M.sup.+
Alkanesulfonate salts RSO.sub.3.sup.-, M.sup.+ Alkyl sulfate salts
ROSO.sub.3.sup.-, M.sup.+ N-Alkylsulfamate salts RNHSO.sub.3.sup.-,
M.sup.+ Akylsulfinate salts RSO.sub.2.sup.-, M.sup.+
S-Alkylthiosulfate salts RSSO.sub.3.sup.-, M.sup.+ Phosphonate
salts RPO.sub.3.sup.=, 2M.sup.+ Phosphate monoester salts
ROPO.sub.4.sup.=, 2M.sup.+ Phosphinate salts R(R')PO.sub.2.sup.-,
M.sup.+ Nitroamide salts RN.sup.-NO.sub.2, M.sup.+
Trisulfonylmethide salts RSO.sub.2(CH.sub.3SO.sub.2).sub.2C.sup.-,
M.sup.+ Xanthate salts RSCS.sub.2.sup.-, M.sup.+
[0052]
2TABLE 2 Cationic Hydrophilic Groups Functional Group General
Formula Quaternary ammonium salts RN.sup.+(CH.sub.3).sub.3, X.sup.-
Primary, secondary, and tertiary RN.sup.+H.sub.n(CH.sub.3).sub.3-n,
X.sup.- ammonium salts N-alkylpyridinium salts
RNC.sub.5H.sub.5.sup.+, X.sup.- Quaternary phosphonium salts
RP.sup.+(CH.sub.3).sub.3, X.sup.- Ternary sulfonium salts
RS.sup.+(CH.sub.3).sub.2, X.sup.- Ternary sulfoxonium salts
RS.sup.+(.fwdarw. O)(CH.sub.3).sub.2, X.sup.-
Bis(phosphoranylidyl)ammonium [R(CH.sub.3).sub.3P .fwdarw. N .rarw.
P(CH.sub.3).sub.3R].sup.+, X.sup.- salts
[0053]
3TABLE 3 Zwitterionic Hydrophilic Groups Functional Group General
Formula Ammonioacetates
R(CH.sub.3).sub.2N.sup.+CH.sub.2CO.sub.2.sup.- Ammonio hexanoates
R(CH.sub.3).sub.2N.sup.+(CH.sub.2).sub.5CO.sub.2.sup.- Ammonio
alkanesulfo- R(CH.sub.3).sub.2N.sup.+(CH.sub.2).sub.3SO.sub.3.sup.-
nates Ammonioalkyl sulfates R(CH.sub.3).sub.2N.sup.+(CH.sub.2)NOS-
O.sub.3.sup.- Trimethylammonio-
RPO.sub.2.sup.-OCH.sub.2CH.sub.2N.s- up.+(CH.sub.3).sub.3 ethyl
alkylphospho- nates Trimethylammonio-
RCO.sub.2CH.sub.2CH(OH)CH.sub.2OPO.sub.2.sup.-O(CH.sub.-
2).sub.2N.sup.+(CH.sub.3).sub.3 ethylphosphate acylglyceryl
esters
[0054]
4TABLE 4 Dipolar Hydrophilic Groups Functional Group General
Formula Aliphatic amine oxides R(CH.sub.3).sub.2N .fwdarw. O
Phosphine oxides R(CH.sub.3).sub.2P .fwdarw. O Phosphonate esters
R(CH.sub.3O).sub.2P .fwdarw. O Phosphate esters
RO(CH.sub.3O).sub.2P .fwdarw. O Arsine oxides R(CH.sub.3).sub.2As
.fwdarw. O Sulfoxides R(CH.sub.3)S .fwdarw. O Sulfoximines
R(CH.sub.3)S(.fwdarw. O) .fwdarw. NH Sulfone diimines
R(CH.sub.3)S(.fwdarw. NH).sub.2 Ammonioamidates RC(O)N - N +
(CH.sub.3).sub.3 Amides RC(O)N(CH.sub.3).sub.2
[0055]
5TABLE 5 Single Bond Hydrophilic Groups Functional Group General
Formula Primary Amines RNH.sub.2
[0056] In Tables 1-5, R represents a hydrocarbon group, preferably
an alkyl group. M represents a metal atom. The subscript n is 1, 2,
or 3. X represents a halogen atom. The groups in Tables 1-5 are
exemplary and not intended to limit the scope of this invention set
forth in the claims. One skilled in the art would be able to select
appropriate hydrophilic groups without undue experimentation.
[0057] Suitable lipophilic groups include monovalent hydrocarbon
groups, substituted monovalent hydrocarbon groups, and siloxanes.
Suitable monovalent hydrocarbon groups have 6 to 22 carbon atoms,
preferably 8 to 22 carbon atoms, more preferably 10 to 18 carbon
atoms. Substituted monovalent hydrocarbon group include halogenated
monovalent hydrocarbon groups, typically having 6 to 22 carbon
atoms. The monovalent hydrocarbon groups and substituted monovalent
hydrocarbon groups can be saturated or unsaturated, branched or
unbranched. Preferred branched hydrocarbon groups typically have 8
to 22 carbon atoms. Preferred linear hydrocarbon groups have 8 to
18 carbon atoms.
[0058] Suitable lipophilic groups are disclosed in International
Patent Publication No. WO 99/12640 at page 12-13. One skilled in
the art would be able to select appropriate lipophilic groups
without undue experimentation.
[0059] Suitable amphiphiles for ingredient (B) also include those
disclosed in U.S. Pat. No. 5,756,108. These include
3,7,11,15-tetramethyl-1,2,3-hexadecanetriol, phytanetriol,
N-2-alkoxycarbonyl derivatives of N-methylglucamine, and
unsaturated fatty acid monoglycerides.
[0060] Suitable amphiphiles for ingredient (B) include surfactants
having HLB values of 2.1 to 4.6, see Porter, M. R., Handbook of
Surfactants, 2.sup.nd ed., Blackie Academic & Professional, pp.
188-236.
[0061] A preferred class of surfactants for use as ingredient (B)
comprise monoglycerides having the general formula: 1
[0062] wherein R is selected from the group consisting of
monovalent hydrocarbon groups of 6 to 22 carbon atoms, preferably 8
to 22 carbon atoms, more preferably 10 to 18 carbon atoms; and
monovalent halogenated hydrocarbon groups of 6 to 22 carbon atoms.
The monovalent hydrocarbon groups can be saturated or unsaturated,
branched or unbranched. Preferred branched hydrocarbon groups
typically have 8 to 22 carbon atoms. Preferred linear hydrocarbon
groups have 8 to 18 carbon atoms. Preferred monoglycerides have a
melting point .gtoreq.40.degree. C. International Patent
Publication No. WO 99/12640 discloses suitable amphiphiles that can
form cubic liquid crystalline phase at pages 12-13 and 28-31.
[0063] Preferred amphiphiles for ingredient (B) include
monoglyceride surfactants such as glycerol monooleate (HLB of 3.8),
glycerol monostearate (HLB 3.4), ethoxylated alcohol surfactants
such as C.sub.12EO.sub.2, C.sub.12EO.sub.23, and C.sub.16EO.sub.3,
wherein EO represent an ethylene oxide group, (see Lynch et al.,
"Aqueous Phase Behavior and Cubic Phase-Containing Emulsions in the
C12E2-Water System," Langmuir, Vol. 16, No. 7, pp. 3537-3542
(2000)), monolinolein, and combinations thereof.
[0064] As long as the monoglyceride has sufficient purity to form
cubic liquid crystalline phase in combination with solvent and the
hydrotrope, the monoglyceride is suitable for ingredient (B). The
monoglyceride is typically greater than about 40% to 100% pure,
preferably about 82.5 to 100% pure. However, monoglycerides having
purity less than about 40% may also be suitable.
[0065] Some diglyceride and triglyceride impurities can prevent the
monoglycerides from forming cubic liquid crystalline phases.
Therefore, the monoglycerides are preferably free of amounts
diglyceride and triglyceride impurities high enough to prevent the
monoglycerides from forming cubic liquid crystalline phases.
[0066] Suitable monoglycerides are known in the art and are
commercially available. Preferred monoglycerides include glycerol
monooleate available under the tradename DIMODAN.RTM. from Danisco
A/S doing business as Grindsted Products A/S of Denmark.
Solvent
[0067] Ingredient (C) is a solvent. Ingredient (C) can be polar or
nonpolar. Suitable polar solvents include water, glycerol,
polyglycols such as polyethylene glycol, formamides such as
formamide, n-methyl formamide and dimethylformamide, ethylammonium
nitrate, and combinations thereof. Suitable nonpolar solvents
include oily solvents such as hydrocarbons and substituted
hydrocarbons (e.g., halogenated hydrocarbons). Hydrocarbons are
exemplified by alkanes and fatty esters such as lanolin. The
solvent must not break down liquid crystals, therefore, some
amphiphilic oils and fatty acid diglycerides are unsuitable for use
as the solvent.
[0068] The amounts of each ingredient in the precursor depend on
the phase behavior of the specific ingredients selected. Cubic gel
precursor comprises a composition wherein the amounts of
ingredients (A), (B), and (C) match any area of the phase diagram
not already comprising cubic phase (i.e., containing no cubic phase
alone and no cubic phase in equilibrium with another phase). One
skilled in the art would be able to select appropriate amounts of
each ingredient without undue experimentation by using a phase
diagram, as exemplified in FIG. 1.
[0069] FIG. 1 represents a ternary phase diagram 100 of a ternary
system of (A) ethanol 103, (B) monoolein 106, and (C) water 109.
Single phases (other than cubic phases) can be used as a precursor.
For example, compositions falling in the single phase regions of
the phase diagram, such as the isotropic liquid region 124 and the
lamellar region 121, are suitable precursors. Compositions falling
in the multiple phase region 112 wherein cubic phase does not form
are also suitable as precursors. Compositions that do not fall in
the Pn3m cubic phase region 115 and the Ia3d cubic phase region 118
are suitable precursors. (See Luzzati et al., J. Mol. Biol., 229,
540-551 (1993) for a description of the types of cubic phases,
including Pn3m and Ia3d cubic phases.)
[0070] The precursor can be used in an application where formation
of cubic phase is desired under a certain set of conditions (i.e.
the presence of sweat, saliva, or other material that will change
the system composition such that it is in the area surrounding
either of the two cubic phases 115, 118 or within the two cubic
phases 115, 118). As a result, the mass fractional composition of
the system of components (A), (B), and (C) relative to each other
needs to simply obey the following equation:
1.0=a+b+c
[0071] wherein a is the mass fraction of ingredient (A), b is the
mass fraction of ingredient (B), and c is the mass fraction of
ingredient (C), and 1.0>a>0, 1.0>b>0,
1.0>c.gtoreq.0. Preferably, a, b, and c are all greater than
zero, however when c is 0, the system is a binary system of
hydrotrope and amphiphile. In a preferred embodiment of the
invention, the precursor is a composition falling within the
isotropic liquid region (e.g., region 124 in FIG. 1) on the phase
diagram.
[0072] The mass fractions of ingredients (A), (B), and (C) in the
cubic gel precursor depend on various factors including the
specific compounds selected for ingredients (A), (B), and (C).
However, typically, 0.5.gtoreq.a.gtoreq.0.05,
0.8.gtoreq.b.gtoreq.0.1, and 0.8.gtoreq.c.gtoreq.0. Preferably, the
mass fraction of ingredient (A) is high enough such that a mixture
of ingredients (A) and (B) forms an isotropic liquid at 25.degree.
C.
[0073] Phase diagrams such as that shown in FIG. 1 can be used for
any system comprising ingredients (A), (B), and (C) to determine
the amounts of each ingredient in the cubic gel precursor, bulk
cubic gels, and cubic gel particle dispersions of this invention.
Phase diagrams can be obtained by one skilled in the art without
undue experimentation using, for example, the methods disclosed by
Laughlin, R. G., The Aqueous Phase Behavior of Surfactants,
Academic Press, Inc., 1994, pp. 521-546.
[0074] The cubic gel precursor of this invention may be used to
directly form either bulk cubic gel, dispersed cubic gel particles,
or a combination of the two, all depending on the desires of the
formulator.
Bulk Cubic Liquid Crystalline Gel
[0075] This invention further relates to a bulk cubic liquid
crystalline gel comprising:
[0076] (A) a hydrotrope,
[0077] (B) an amphiphile capable of forming a cubic liquid
crystalline phase, and
[0078] (C) a solvent,
[0079] wherein ingredients (A), (B), and (C) are present in mass
fractions relative to each other such that
1.0=a+b+c
[0080] wherein a is the mass fraction of ingredient (A), b is the
mass fraction of ingredient (B), and c is the mass fraction of
ingredient (C), and wherein 1.0>a>0, 1.0>b>0,
1.0>c>0; and with the proviso that a, b, and c fall within a
cubic liquid crystalline phase region on a phase diagram
representing phase behavior of ingredients (A), (B), and (C).
[0081] The mass fractions of ingredients (A), (B), and (C) in the
bulk cubic gel depend on various factors including the specific
compounds selected for ingredients (A), (B), and (C). However,
typically, 0.1.gtoreq.a.gtoreq.0.005, 0.75.gtoreq.b.gtoreq.0.45,
and 0.6.gtoreq.c.gtoreq.0.1.
[0082] Ingredients (A), (B), and (C) are as described above for the
cubic gel precursor. However, the amounts of ingredients (A), (B),
and (C) differ, such that the system forms bulk cubic gel. The
amount of each ingredient in the bulk cubic gel depends on the
phase behavior of the specific ingredients selected. One skilled in
the art would be able to select appropriate amounts for each
ingredient without undue experimentation by using a phase diagram.
The amount of each ingredient must be such that the combined
ingredients will form a cubic liquid crystalline phase or a cubic
liquid crystalline phase in combination with one or more other
phases. Any combination of the amounts of the ingredients that fall
within the cubic liquid crystalline region in the phase diagram
will be suitable for this invention. For example, referring to FIG.
1 again, the amounts of water 109, ethanol 103, and monoolein 106
must be such that they fall in one of the cubic phase regions 115,
118 in the phase diagram.
Dispersed Cubic Liquid Crystalline Gel Particles
[0083] This invention further relates to cubic liquid crystalline
gel particles, and dispersions thereof. The cubic liquid
crystalline gel particles have the same composition as that
described above for the bulk cubic gel, however, the form differs.
The particles have a particulate form, rather than a bulk gel. The
particles typically range in size from 10 micrometers to 50
nanometers. The dispersion comprises:
[0084] (A) a hydrotrope,
[0085] (B) an amphiphile capable of forming a cubic liquid
crystalline phase, and
[0086] (C) a solvent,
[0087] wherein ingredients (A), (B), and (C) are present in mass
fractions relative to each other such that
1.0=a+b+c
[0088] wherein a is the mass fraction of ingredient (A), b is the
mass fraction of ingredient (B), and c is the mass fraction of
ingredient (C), and wherein 1.0>a>0, 1.0>b>0,
1.0>c>0; and with the proviso that a, b, and c fall within a
region representing cubic liquid crystalline phase in combination
with at least one other phase on a phase diagram representing phase
behavior of ingredients (A), (B), and (C), with the proviso that
the dispersion has the form cubic liquid crystalline gel particles
dispersed in the other phase. (Referring again to FIG. 1,
dispersions according to this invention fall within the region
representing cubic liquid crystalline phase in combination with
another phase 127 on the phase diagram 100.)
[0089] The mass fractions of ingredients (A), (B), and (C) in the
dispersions depend on various factors including the specific
compounds selected for ingredients (A), (B), and (C). However,
typically, 0.1.gtoreq.a.gtoreq.0.005, 0.3.gtoreq.b.gtoreq.0.03, and
0.9.gtoreq.c.gtoreq.0.6.
[0090] The cubic liquid crystalline gel particles, and dispersions
thereof, comprise ingredients (A), (B), and (C), described above,
and preferably (D) a stabilizer. Suitable stabilizers include
water-soluble polymers such as Poloxamer 407 or Carbomer cellulosic
polymer, sub-micron or micron-sized solid particles such as clays
or crystalline waxes, or coatings of lamellar liquid crystalline
phases on the cubic liquid crystalline particle surfaces.
[0091] Suitable water-soluble polymers include polyoxyethylene
polyoxypropylene copolymers such as Poloxamer 407, which is a
polyoxyethylene polyoxypropylene block copolymer of the formula
HO(CH.sub.2CH.sub.2O).sub.x(CH(CH.sub.3)CH.sub.2)).sub.y(CH.sub.2CH.sub.2-
O).sub.zOH wherein the average values of x, y, and z are 98, 67,
and 98, respectively. Poloxamer 407 is known in the art and
commercially available as HODAG.RTM. Nonionic 1127-F, from Lambent
Technologies Inc., of Norcross, Ga.; PLURACARE.RTM. F-127 from BASF
Corporation of Parsippany, N.J.; SYNPERONIC.RTM. PE/F-127 from
Imperial Chemical Industries, PLC., of London, England; MACOL.RTM.
27 from Mazer Chemicals, Inc., of Gurnee, Ill.; and PLURONIC.RTM.
F-1127 from Wyandotte Chemicals Corporation of Wyandotte, Mich.
[0092] Carbomer cellulosic polymer is a homopolymer of acrylic acid
crosslinked with an allyl ether of pentaerythritol or an allyl
ether of sucrose. Carbomer cellulosic polymer is available as
SYNTHALEN.RTM. from 3V Sigma of Milan, Italy and CARBOPOL.RTM. from
the B.F. Goodrich Company of New York, N.Y.
[0093] Suitable (D) stabilizers are disclosed in the C.T.F.A.
International Cosmetic Ingredient Dictionary, 4.sup.th ed., ed. J.
M. Nikitakis, et al., The Cosmetic, Toiletry, and Fragrance
Association, Washington, D.C.; and in Evans, The Colloidal Domain,
2.sup.nd ed., Wiley, N.Y., pp. 575-588 (1999).
[0094] The amount of ingredient (D) added is typically 1 to 2%
based on the weight of ingredient (C).
Methods of the Invention
[0095] This invention further relates to methods for preparing the
cubic gel precursor, bulk cubic liquid crystalline gel, and
dispersed cubic liquid crystalline gel particles described
above.
Cubic Gel Precursor
[0096] A preferred method for preparing the cubic gel precursor of
this invention comprises the steps of:
[0097] 1) combining ingredients (A) the hydrotrope with (B) the
amphiphile, both described above, and
[0098] 2) optionally adding (C) the solvent described above,
[0099] wherein the amounts of each ingredient in the composition
are as described above. The precursor does not form cubic gel by
itself.
[0100] In step 1), the hydrotrope and amphiphile can be combined by
any convenient means. When ingredient (B) is a liquid, ingredients
(A) and (B) can be combined by simply mixing. When ingredient (B)
is a solid such as monoolein, ingredients (A) and (B) are
preferably combined by heating ingredient (B) to a temperature
greater than its melting point and then combining (e.g., mixing)
the melted amphiphile with the hydrotrope. The exact temperature
depends on the melting point of the specific amphiphile selected
for ingredient (B). Alternatively, ingredient (B) can be fragmented
into solid particles and then combined with the hydrotrope; or the
hydrotrope may be dissolved in an aqueous hydrotrope solution, and
the solution combined with ingredient (B) in step 1).
[0101] Step 2) can be carried out during or after step 1). Step 2)
can be carried out by, for example, mixing by any convenient means.
The product of step 2) contains amounts of ingredients (A), (B),
and (C) corresponding to any region on the relevant phase diagram
where cubic phase does not form. However, the amounts of
ingredients (A), (B), and (C) are preferably such that the product
of step 1) is an isotropic liquid at 25.degree. C. Referring to
FIG. 1, for example, any combination of (A) ethanol, (B) monoolein,
and (C) water that falls in the isotropic region 124 of the phase
diagram 100 is suitable to use as the precursor.
Bulk Cubic Liquid Crystalline Gel
[0102] Bulk cubic liquid crystalline gel can be prepared by
applying a stimulus to the precursor prepared as described above.
The stimulus can be selected from the group consisting of: a
temperature change; a pressure change; addition of a salt; a pH
change; addition of a specified material such as additional
hydrotrope, amphiphile, or solvent; removal of a specified material
such as a portion of the hydrotrope, amphiphile, or solvent;
combinations thereof; and others. When an ingredient is added or
removed, the result must be to bring the relative amounts of each
ingredient into a cubic phase region on the relevant phase diagram.
Referring to FIG. 1, for example, adding a sufficient amount of an
ingredient selected from the group consisting of (A) ethanol 103,
(B) monoolein 106, and (C) water 109 to bring the relative amounts
of (A), (B), and (C) into a cubic phase region 115, 118 of the
phase diagram 100 will cause bulk cubic liquid crystalline gel to
form.
[0103] The precursor can be diluted, for example, by mixing the
precursor with additional (A) hydrotrope, (B) amphiphile, or (C)
solvent. A material can be removed from the precursor by, for
example, evaporation.
[0104] In an alternative embodiment of the invention, bulk cubic
liquid crystalline gel can be prepared directly by combining
amounts of ingredients (A), (B), and (C) corresponding to a cubic
phase region on the relevant phase diagram.
[0105] After formation of the bulk cubic liquid crystalline gel has
been completed, the hydrotrope is not always necessary. The
hydrotrope may optionally be removed, e.g., by evaporation. All or
a portion of the hydrotrope may be removed.
Dispersed Cubic Liquid Crystalline Gel Particles
[0106] Dispersed cubic liquid crystalline gel particles can be
prepared from bulk cubic gel or directly from the cubic gel
precursor.
[0107] Preparing a dispersion of cubic gel particles directly from
the precursor can be carried out by a method comprising:
[0108] 1) a dispersing step selected from the group consisting
of
[0109] a) dispersing the precursor described above in a solvent,
and
[0110] b) dispersing solvent in the precursor and thereafter
diluting; and preferably
[0111] 2) stabilizing the product of step 1).
[0112] Steps a) and b) may be carried out by several alternate
methods. These methods include applying fluid shear such as in a
shear mill, applying ultrasonic waves, extruding through a small
pore membrane (membrane emulsification), cross membrane
emulsification, impinging from opposing jets a stream of the
precursor and a stream of solvent, using a static mixer, or
combining streams of solvent and the precursor in a micro-mixer
that utilizes either laminar or turbulent shear flow conditions to
disperse the streams. The precursor may also be contacted with
solvent (e.g., water) by spraying a fine mist of the precursor into
an environment comprising solvent vapors (e.g., a humid
environment). Such a spray allows the formation of droplets with a
surface coating of cubic liquid crystalline phase. The droplets can
then be collected in bulk in water to disperse the particles and
complete their conversion to cubic liquid crystalline gel
particles. Alternatively, solvent (e.g. water) can be added to the
precursor by bubbling vaporized solvent (e.g., steam) into the
precursor. The product of step 1) is an dispersion of cubic liquid
crystalline gel particles that is unstable against aggregation.
[0113] The product of step 1) is stabilized (i.e., sterically
stabilized), for example, by adding (D) a stabilizer described
above, or by forming a coating of lamellar liquid crystalline phase
on the surfaces of the particles. The product of step 1) may also
be stabilized by direct dispersion into a viscous aqueous matrix
such as that formed by a water-soluble stabilizer such as Carbomer
cellulosic polymer. The product of step 2) is a dispersion of
colloidally stable cubic liquid crystalline gel particles.
[0114] In an alternative embodiment of the invention, steps 1) and
2) are combined. Steps 1) and 2) are combined by adding (D) the
stabilizer to (C) the solvent to form a stabilizing composition and
thereafter combining the stabilizing composition with the product
of step Ingredient (A) the hydrotrope may or may not be desirable
in the final product, and ingredient (A) is not always necessary
once cubic liquid crystalline gel particles form. Therefore, this
method may further comprise optional step 3). Step 3) comprises
removing ingredient (A) after step 2). Ingredient (A) may be
removed by, for example, dialysis and flash evaporation.
[0115] In an alternative embodiment of the invention, the precursor
may be diluted to form an intermediate such as a dispersion of
lamellar liquid crystalline particles, vesicles, or an easily
dispersed emulsion. Any of these intermediates can be used to form
a colloidally stable dispersion of cubic liquid crystalline gel
particles by further dilution in combination with any of the above
dispersion and stabilization techniques in steps 1) and 2). This is
because the dispersions may be formed and stabilized prior to
particle formation. This offers the advantages that intermediates
are easier to disperse and stabilize than the potentially more
viscous dispersions, and once stabilized, the resulting stabilized
intermediates can be diluted to form cubic liquid crystalline gel
particles that require no further stabilization.
[0116] Alternatively, cubic gel particles can be prepared by
fragmenting the bulk cubic gel. Fragmenting the bulk cubic gel can
be carried out by, for example, subjecting the bulk cubic gel to
shear in a shear mill, ultrasonication, micromixer dispersal, or
membrane emulsification. However, if too much energy input is
carried out, the cubic liquid crystalline structure of the
particles can physically degrade, so care must be exercised when
fragmenting the bulk cubic gel. When the structure of the particles
degrades, other structures, such as vesicles, can form.
[0117] FIG. 2 is a flow diagram 200 showing methods for preparing
dispersions of cubic gel particles according to the preferred
embodiments of this invention. In each method, a solid amphiphile
is first melted 201 by heating to a temperature greater than or
equal to its melting point. Next, the amphiphile is combined with a
hydrotrope, and optionally a solvent 202. The combination
comprising the amphiphile and hydrotrope, with or without solvent,
forms an isotropic liquid at 25.degree. C. After this, there are 4
potential preferred routes for preparing dispersions of cubic gel
particles.
[0118] In the first route, the isotropic liquid is dispersed into
water 204, thereby forming a colloidally unstable dispersion of
cubic gel particles. The unstable dispersion is then stabilized
205, by the methods described above.
[0119] In the second route, the isotropic liquid is sprayed into
humid air 206. This forms droplets comprising a liquid core
comprising the amphiphile coated by cubic gel phase material. The
droplets are diluted 207 with sufficient water to form a
colloidally unstable dispersion of cubic gel particles. Thereafter,
the resulting mixture is stabilized 208, by the methods described
above.
[0120] In the third route, the isotropic liquid is diluted with
sufficient water to form an interfacially stabilized emulsion phase
209. The emulsion phase is sterically stabilized by a method
described above 210. Thereafter, the stabilized emulsion phase is
further diluted with additional water to form a colloidally stable
particle dispersion 211.
[0121] In the fourth route, water is dispersed into the isotropic
liquid to form an inverse particle dispersion 212 (i.e., droplets
of water dispersed in the isotropic liquid, rather than cubic phase
particles dispersed in water). Thereafter, the inverse dispersion
is further diluted with more water to form a colloidally unstable
particle dispersion 213. The unstable particle dispersion is
stabilized by a method described above 214.
[0122] After preparing a dispersion, the particles may optionally
be isolated therefrom by any conventional means. For example, the
particles can be isolated by removing a sufficient amount of an
ingredient selected from the group consisting of (C) the solvent
and a combination of (C) the solvent and (A) the hydrotrope. The
particles may be dried by evaporation. Alternatively, the particles
may be removed from the dispersion by centrifugation or
filtration.
[0123] FIG. 3 is a ternary phase diagram 300 showing the phase
behavior of ethanol 321, monoolein 324, and water 327. Single
phases (other than cubic phases) can be used as a precursor. For
example, compositions falling in the single phase regions of the
phase diagram, such as the isotropic liquid region 342 and the
lamellar region 339, are suitable precursors. Precursors can be
diluted with one or more ingredients to form bulk cubic gels
falling in the Pn3m cubic phase region 333 or the Ia3d cubic phase
region 336. Precursors can also be diluted to form cubic gel
particle dispersions falling in the multiple phase region 330. The
phase diagram 300 can be used to carry out the above methods. For
example, a precursor 309 falling in the isotropic liquid region 342
can be prepared as described above. The precursor 303, 306, or 309
can be diluted to form a dispersion of cubic gel particles 315 by
adding solvent 327.
[0124] Furthermore, the yield of processes producing all forms of
cubic phase (bulk cubic gels, dispersions of cubic gel particles)
can be predicted using the phase diagram 300. By predetermining the
desired end fraction of cubic phase, the starting and ending points
on a phase trajectory 312 can be determined and a process developed
from the trajectory 312. If, for example, a suspension of about 60%
(w/w) cubic gel particles is desired, the ending point 315 of a
phase trajectory 312 must lie on an equilibrium tie line 318
between the isotropic liquid phase region 342 and a cubic phase
region 333. Dilution with solvent 327 is represented by a straight
line 312 drawn from the starting point to the solvent 327 corner of
the phase diagram 300. The starting point of the above dilution
process can fall anywhere on a line 312 drawn from the solvent 327
corner through the midpoint of a cubic-liquid tie line 318 and out
through the phase diagram 300.
[0125] The particles formed in the dispersions typically have
particle sizes in the range of about 10 nanometers to about 100
micrometers. However, the exact particle size range depends on the
method used to make the particles. For example, particles prepared
from precursors that are isotropic liquids typically have sizes in
the range of about 10 to about 500 nanometers. Particles prepared
from precursors that are emulsions typically have sizes in the
range of about 100 nanometers to about 100 micrometers.
Methods of Use
[0126] The precursors of this invention can be used as anti-wetting
agents. For example, a precursor can be placed between sheets of
tissue to provide an absorbent core in, for example, diapers and
pads. With the addition of liquid, the precursor forms bulk cubic
gel to hold the liquid.
[0127] The bulk cubic gels of this invention can be used to
generate trans-membrane protein crystal structures.
[0128] In a preferred embodiment of the invention, the precursors,
bulk cubic gels, and particularly the dispersions and cubic gel
particles of this invention are used as delivery vehicles in
topical pharmaceutical and cosmetic compositions. The compositions
may further comprise one or more pharmaceutically active
ingredients, such as non-steroidal anti-inflammatory drugs (e.g.,
ketoprofen), or cosmetic ingredients, such as perfumes or dyes. In
a more preferred embodiment of the invention, the active ingredient
also has hydrotropic properties and may be used in addition to the
hydrotrope described above as component (A). Alternatively, the
active ingredient may be used instead of component (A), or instead
of a portion of component (A). Compositions containing an active
ingredient can be prepared by the methods described above, wherein
the active ingredient is added concurrently with component (A).
[0129] In one embodiment of the invention, the precursors, gels,
dispersions, and particles described above can be used as delivery
vehicles for active ingredients such as pharamceutically active
ingredients, agrochemicals, and others. Suitable agrochemicals
include pesticides, herbicides, and others. The pesticides and
herbicides may be water-soluble or oil-soluble and may be
incorporated into the ternary system as an active ingredient with
hydrotropic properties or as an active ingredient separate from the
hydrotrope.
[0130] Examples of suitable pesticides include organophosphates
such as diazinon and non-organophosphates such as diclofop-methyl,
terrazole, vinclozolin, atrazine, oxamyl propargite, and triallate.
Examples of suitable herbicides include atrazine, nicosulfuron,
carfentrazone, imazapyr, benefin, and acifluorfen.
[0131] In a preferred embodiment of the invention, the controlled
release delivery of active ingredients, including agrochemicals
such as herbicides and pesticides to a substrate such as a plant or
insect surface may be carried out using cubic gel precursors in two
main ways: evaporation and dilution. The uniqueness of the
evaporation and dilution processes is their ability to produce a
"responsive" liquid that provides targeted delivery of an active
ingredient in response to some specified stimulus, such as dilution
by residual moisture or evaporation as a consequence of spraying.
Evaporation and dilution processes may be represented by a line
drawn from a starting point to an ending point on the ternary phase
diagram.
Dilution
[0132] In the dilution process, the starting point is any
previously described precursor region on the phase diagram and the
ending point is any region of single-phase cubic liquid crystal or
multiple-phase (in which at least one phase is cubic liquid
crystal). The trajectory of a dilution path will be determined by a
straight line drawn between the starting point and the solvent apex
of a ternary phase diagram. Once the starting point is chosen, the
ending point falls along that straight line.
[0133] In one embodiment of the dilution process, a mixture of
amphiphile and either an active ingredient with hydrotropic
properties or a separate active in combination with a hydrotrope is
combined to form an isotropic liquid precursor. The precursor is
then sprayed onto a substrate coated with solvent, such as a leaf
surface coated with residual moisture (i.e., dew droplets).
Spraying disperses the precursor into small droplets that coat the
substrate and contact the solvent. Mixing of the solvent on the
substrate, e.g., the water on the leaf, with the precursor
constitutes dilution and drives the droplet system into the
cubic+solvent region of the phase diagram, producing a coating of
solvent, active ingredient, and cubic liquid crystalline material
which slowly releases the active ingredient into the substrate.
Monoglycerides are preferred as the amphiphile in the precursor for
plant applications because it is thought that monoglycerides will
enhance leaf surface penetration by the active ingredients.
Evaporation
[0134] Evaporation is similar to dilution in that the starting
point on the ternary phase diagram is also a precursor from which
solvent and/or hydrotrope is evaporated to drive the system to an
ending point on the phase diagram in a region of single-phase cubic
liquid crystal or multiple-phase (in which at least one phase is
cubic liquid crystal). In the case of evaporation, choosing a
starting point dictates that the process trajectory will progress
toward the amphiphile apex of the phase diagram. The exact path
taken will be a function of the vapor pressure of the mixture of
the solvent and the hydrotrope, and may not be linear as in the
case of dilution. Evaporation may occur during spraying and/or
after deposition onto the target substrate.
[0135] In one embodiment of the evaporation process, a mixture of
amphiphile, hydrotrope, solvent, and active ingredient is combined
to form an isotropic liquid precursor. The precursor is then
sprayed onto a substrate such as a leaf surface. Spraying disperses
the precursor into small droplets, increasing their surface area
and thus their ability to evaporate solvent and/or hydrotrope. As
the solvent and/or hydrotrope evaporate, the droplet system rapidly
passes into the cubic liquid crystalline regions of the ternary
phase diagram, again producing a coating of solvent, active, and
cubic liquid crystalline material which slowly releases the active
into the substrate such as the leaf surface. Monoglycerides are
preferred as the amphiphile in the precursor for plant applications
because it is thought that monoglycerides will enhance leaf surface
penetration by the active ingredients.
[0136] This invention offers the further advantage that pore size
of the cubic liquid crystalline materials (i.e., bulk cubic gels,
cubic gel particles, and dispersions of cubic gel particles) can be
controlled. Pore size depends on the amount of component (A). In
general, pore size increases as the amount of component (A)
increases.
EXAMPLES
[0137] These examples are intended to illustrate the invention to
those skilled in the art and should not be interpreted as limiting
the scope of the invention set forth in the claims.
Reference Example 1
Determination of Hydrotrope Utility
[0138] A compound for use as a hydrotrope is dissolved in water in
amounts to form a hydrotrope solution. The solution is added to
monoolein (DIMODAN.RTM. MO90K) to yield a composition. The
composition is left to equilibrate overnight at a temperature of 25
to 30.degree. C.
[0139] Polarized light microscopy (PLM) is used to determine
whether the composition exhibits birefringence or distinct
textures. PLM can be carried out on a polarized light microscope or
constructed light box, as described by Laughlin, R. G., J. Colloid
Interface Sci, 55, 239-242 (1976). Rheological properties of the
composition are also observed. Compositions containing a viscous
phase that exhibits no birefringence and no distinct textures by
PLM form cubic phase. Formation of cubic phase means that the
compound is suitable to use as a hydrotrope in this invention at
the amount of the compound specified.
Examples 1 to 4 and Comparative Examples 1 to 5
[0140] Various compounds are evaluated according to Reference
Example 1. The compounds, the compositions prepared, and the
results are in Table E1, below. FIG. 4 is a ternary diagram 400
showing the data points in Example 3. FIG. 5 is a ternary diagram
500 for 1,2-hexanediol 516, monoolein 517, and water 518. FIG. 5
shows the data points 501-515 and phases formed at each point in
Comparative Example 2. FIG. 6 is a ternary diagram 600 for
1,2-hexanediol 613, monoolein 614, and water 615. FIG. 6 shows the
data points 601-612 and phases formed at each point in Comparative
Example 3. FIG. 7 is a ternary diagram 700 for ethanol 713,
monoolein 714, and water 715. FIG. 7 shows the data points 701-712
and phases formed at each point in Example 4 and Comparative
Example 4.
6TABLE E1 Hydrotrope Test Results Amount of Amount Amount of Fig.
Point Compound of Amphiphile Example Compound No. No. (%) Water (%)
(%) Phase(s) Formed Ex. 1 ethanol 4 404 9 55 36 cubic and lamellar
405 6 56 38 cubic and lamellar Comp. ethanol 4 401 20 48 32 L1 and
lamellar Ex. 1 402 12 53 35 L1 403 10 54 36 L1 Ex. 2 1,4- 10 80 10
cubic and L1 butanediol procaine 10 80 10 cubic and L1 hydrogen
chloride Comp. 1,2- 5 501 10 81 9 liquid water and L1 Ex. 2
hexanediol 502 10 71 19 L1 and lamellar 503 10 64 26 L1 and
lamellar 504 12 53 35 L1 and lamellar 505 10 45 45 L1 and lamellar
506 20 72 8 L1 507 20 64 16 L1 508 20 56 24 L1 509 20 49 31 L1 510
20 40 40 L1 and lamellar 511 30 63 7 L1 512 30 56 14 L1 513 30 49
21 L1 514 30 42 28 L1 515 30 34 36 L1 Ex. 3 1,2- 6 601 6 56 38
cubic and lamellar hexanediol 602 4 58 38 cubic and lamellar 603 2
59 39 cubic and lamellar 604 6 38 56 cubic and lamellar 605 4 39 57
cubic and lamellar 606 2 39 59 cubic and lamellar 607 6 28 66 cubic
and lamellar 608 2 29 69 cubic and lamellar Comp. 1,2- 6 609 16 13
71 lamellar Ex. 3 hexanediol 610 10 14 76 lamellar 611 5 14 81
lamellar 612 5 12 83 lamellar Ex. 4 ethanol 7 701 11 88 1 cubic
& isotropic liquid 702 10 70 20 cubic & isotropic liquid
703 10 59 31 cubic & isotropic liquid 704 10 48 42 cubic &
isotropic liquid Comp. ethanol 7 705 20 65 14 L1 Ex. 4 706 20 55 25
L1 and lamellar 707 19 49 32 L1 and lamellar 708 20 42 39 lamellar
709 29 60 11 L1 and lamellar 710 28 52 20 L1 and lamellar 711 30 40
30 lamellar 712 30 29 41 lamellar Comp. 2-propanol 10 80 10 Turbid
solution and L1 Ex. 5 phase
[0141] Example 1 and Comparative Example 1, and Example 4 and
Comparative Example 4, show that ethanol can be used as a
hydrotrope in a system with monoolein and water according to this
invention, when the ethanol is present at relatively low levels
(i.e., less than or equal to 10% of the system). Comparative
Example 1 and Comparative Example 4 show that when the amount of
ethanol is too high, (above about 10 or 11%), the system does not
form cubic phase. Example 4 shows that ethanol is a preferred
hydrotrope for use in this invention because in a system of
ethanol, monoolein, and water, cubic phase in equilibrium with
liquid water can be formed.
[0142] Example 2 shows that 1,4-butanediol and procaine hydrogen
chloride are effective as hydrotropes in a system with monoolein
and water according to this invention.
[0143] Example 3 shows that 1,2-hexanediol is suitable to use as a
hydrotrope in a system with monoolein and water according to this
invention. However, Example 3, and Comparative Examples 2 and 3
show that 1,2-hexanediol does not form cubic phase in equilibrium
with liquid water at the practical amounts of 1,2-hexanediol used
in this invention.
[0144] Comparative Example 5 shows that 2-propanol is not preferred
to use as a hydrotrope in a system of monoolein and water according
to this invention because the system does not form cubic phase when
10% 2-propanol is present.
Reference Example 2
Cryo-Transmission Electron Microscopy
[0145] Samples were evaluated to determine whether cubic phase had
formed by cryo-TEM. For cryo-TEM, the samples were prepared in a
controlled environment vitrification system (CEVS) which is
described in detail by Bellare, J. R.; Davis, H. T.; Scriven, L.
E.; Talmon, Y., Controlled environment vitrification technique, J.
Electron Microsc. Tech., 1988, 10, 87-111. A 3 .mu.l drop of the
sample solution was placed on a carbon-coated holey polymer support
film mounted on a standard 300-mesh TEM grid (Ted Pella, Inc.). The
drop was blotted with filter paper until it was reduced to a thin
film (10-200 nm) spanning the holes (2-8 .mu.m) of the support
film. The sample was then vitrified by rapidly plunging it through
a synchronous shutter at the bottom of the CEVS into liquid ethane
at its freezing point. The vitreous specimen was transferred under
liquid nitrogen into a Philips CM120 transmission electron
microscope for imaging. The temperature of the sample was kept
under -170.degree. C. throughout the examination.
Reference Example 3
Small Angle X-ray Scattering (SAXS)
[0146] SAXS is a technique that measures the fluctuations in
electron density in a material over the size range of about 1000-5
nm, which makes it suitable to characterize structures in a sample
over this spatial range. SAXS consists of illuminating a sample
with a collimated beam of x-rays of the appropriate wavelength and
measuring the distribution of intensity scattered. If the
structures are periodic, SAXS is particularly well suited to assess
the type of periodicity and its dimensions. Periodic distributions
in matter in a material will cause periodic distribution of
scattered intensity over the appropriate angular range.
[0147] SAXS was performed on samples with CuK.alpha. radiation
(.lambda.=0.154 nm) generated with a Rigaku RU-300 rotating anode.
The generator was operated at 40 kV and 40 mA with a 0.2.times.0.2
mm focal size (a 0.2.times.2 mm filament run in point mode). The
patterns were collected with the Siemens 2-dimensional small angle
scattering system which consists of the HI-STAR wire detector and
Anton Parr HR-PHK collimation system. Collimation is achieved with
a single 100 mm diameter pinhole 490 mm from the focal spot. The
size of the focal spot restricts beam divergence. A 300 mm guard
pinhole is placed 650 mm from the focal spot, just in front of the
sample. The detector is placed a distance of 650 mm from the
sample. Ni filters were used to eliminate the K.beta. radiation.
Because of the small beam size and large sample-to-detector
distance, two dimensional profiles (qx, qy) can be obtained with a
minimum of instrumental smearing, so no smearing corrections were
employed.
Example 5
[0148] A bulk cubic gel according to this invention is prepared by
melting 50% monoolein, adding 2% ethanol, and then adding 48%
water. The sample is analyzed according to the method in Reference
Example 3. The results are in Table E2.
Comparative Example 6
[0149] A dispersion of cubic gel particles is prepared as in
Example 5, except that ethanol was omitted. The sample is analyzed
according to the method in Reference Example 3. The results are in
Table E2.
Comparative Example 7
[0150] Predicted values for Pn3m cubic phase of a system of
monoolein and water were obtained. See Funari, S. S. and Gert, R.,
"X-ray Studies on the C12EO2/Water System", J. Phys. Chem. B 1997,
101, 732 and Winey, Thomas and Fetters, "Morphologies in Binary
Blends", J. Chem. Phys. 1991, Vol. 95, No. 12, Pg. 9368. The
results are in Table E2.
7TABLE E2 Comparison of peak spacing form SAXS data for
monoolein/water systems with that predicted from Pn3m cubic phase.
Comparative Comparative Miller Index Example 5 Example 6 Example 7
of Reflection d.sub.hkl/d.sub.110 d.sub.hkl/d.sub.110
d.sub.hkl/d.sub.110 110 1.00 1.00 1.00 111 0.819 0.816 0.816 200
0.707 0.704 0.707 211 0.574 0.573 0.577 220 0.495 0.496 0.500
[0151] The Miller Index describes the symmetry of the liquid
crystalline structures. The ratio d.sub.hkl/d.sub.110 represents
the angular position of one peak relative to the primary peak
(110). Peaks spaced at about the same intervals as those shown in
Comparative Example 7 have the same structure as Comparative
Example 7. Example 5 and Comparative Examples 6 and 7 show that the
periodic structure and type of structure of the bulk cubic gel
according to this invention correspond well to the periodic
structure and type of structure of known cubic phase materials
consisting of monoolein and water. Therefore, the compositions of
this invention form cubic phase.
Example 6
[0152] A precursor is formed by melting 0.5 g monoolein and mixing
in 0.5 g ethanol to form a clear, low viscosity (isotropic) liquid.
9.0 g of water are added. A colloidally unstable dispersion of 9%
cubic phase particles in 91% water forms. This is illustrated in
FIG. 9.
[0153] FIG. 9 is a phase diagram 900 showing the phase behavior of
ethanol 903, monoolein 906, and water 909. The precursor 912 falls
within the isotropic liquid region 915 of the phase diagram 900.
The dispersion 939 falls within a multiple phase region 921 wherein
cubic phase is present with liquid water. The dispersion 918 falls
on an equilibrium tie line 933 between the isotropic liquid phase
region 915 and the Pn3m cubic phase region 924.
Example 7
[0154] 1.0 g monoolein is melted and mixed with 0.5 g ethanol and
0.18 g water to form a clear, low viscosity (isotropic) liquid 936.
8.4 g of water are added. A colloidally unstable dispersion of 22%
cubic phase particles and 78% water forms. This is also illustrated
in FIG. 9. FIG. 9 is a phase diagram 900 showing the phase behavior
of ethanol 903, monoolein 906, and water 909. The precursor 936
falls within the isotropic liquid region 915 of the phase diagram
900. The dispersion 918 falls within a multiple phase region 921
wherein cubic phase is present with liquid water. The dispersion
939 falls on an equilibrium tie line 933 between the isotropic
liquid phase region 915 and the Pn3m cubic phase region 924.
Example 8
[0155] 0.5 g ethanol is mixed with 0.5 g melted monoolein to form a
clear, low viscosity (isotropic) liquid. 9.0 g of a 1.2% polymer
(Poloxamer 407) solution is added. A colloidally stable dispersion
of 9% cubic phase particles and 91% water and polymer forms. A
cryo-TEM image was obtained by the method of Reference Example 2.
The image is in FIG. 8a.
Example 9
[0156] 1.0 g monoolein is melted and mixed with 0.5 g ethanol and
0.18 g water to form a clear, low viscosity (isotropic) liquid. 8.4
g of a 1.2% polymer (Poloxamer 407) solution are added. A
colloidally stable dispersion of 22% cubic phase particles and 78%
water and polymer forms.
[0157] Examples 7-10 show that dispersions of cubic gel particles
can be successfully prepared according to the methods of this
invention.
Example 10
[0158] A precursor 1012 is prepared by mixing 0.20 g melted
monoolein and 0.40 g ethanol to form a clear liquid. An
intermediate in the form of a macroemulsion having both large
(i.e., 5-10 .mu.m diameter) particles as well as small (i.e.
100-150 nm in diameter) particles is formed by adding 1.40 g water.
Particle diameter is measured by optical microscopy. The particles
under a microscope are photgraphed and compared to photographs of
calipers with 1 micrometer divisions. The emulsion is diluted by
adding 4.24 g water. A colloidally unstable dispersion of cubic
liquid crystalline particles 1036 forms. This is illustrated in
FIG. 10.
[0159] FIG. 10 is a phase diagram 1000 showing the phase behavior
of ethanol 1003, monoolein 1006, and water 1009. The precursor 1012
falls within the multiple phase region 1021 of the phase diagram
1000. The dispersion 1036 falls within a multiple phase region 1021
wherein cubic phase is present with liquid water. The dispersion
1036 falls on an equilibrium tie line 1033 between the isotropic
liquid phase region 1036 and the Pn3m cubic phase region 1024.
Example 11
[0160] A precursor is prepared by mixing 0.20 g melted monoolein
and 0.40 g ethanol to form a clear liquid. An intermediate in the
form of an emulsion having a narrower particle size distribution
than that of Example 10 is prepared by adding 1.40 g water to form
an emulsion. The emulsion is sheared for five minutes in a high
shear mill at 15,000 RPM to reduce the particle size. The emulsion
is diluted by adding 4.24 g water. A colloidally unstable
dispersion of cubic liquid crystalline particles forms.
Example 12
[0161] Example 10 is repeated, except that rather than adding 4.24
g water to dilute the emulsion, 4.24 g of an aqueous polymer
(Poloxamer 407) solution is used instead. This substitution causes
a colloidally stable dispersion to form, and the presence of the
polymer does not affect the phase behavior of the system in that
cubic phase still forms. A cryo-TEM image was obtained by the
method of Reference Example 2. The image of a cubic gel particle
formed in the dispersion is in FIG. 8b. Example 12 shows that the
dispersions prepared according to the methods of this invention
(with the hydrotrope present) form cubic liquid crystalline gel
phase particles.
Example 13
[0162] Example 11 is repeated, except that rather than adding 4.24
g water to dilute the emulsion, 4.24 g of an aqueous polymer
(Poloxamer 407) solution is used instead. This substitution causes
a colloidally stable dispersion to form, and the presence of the
polymer does not affect the phase behavior of the system.
Example 14
[0163] 5.0 g ethanol, 25.0 g melted monoolein, and 70.0 g water are
mixed directly. A colloidally unstable dispersion of cubic liquid
crystalline particles forms.
Example 15
[0164] 5.0 g ethanol, 25.0 g melted monoolein, and 70.0 g of a 1.5%
polymer (Poloxamer 407) solution are combined directly. A
colloidally stable dispersion of cubic liquid crystalline particles
forms.
[0165] Examples 11-15 show that dispersions of cubic gel particles
can be successfully prepared according to the methods of this
invention.
Example 16
[0166] A cubic gel precursor is prepared by mixing 40.0 g ethanol
with 30.0 g melted monoolein. An isotropic liquid precursor forms.
Example 16 shows that cubic gel precursors can be prepared
according to the methods of this invention.
Example 17
[0167] 5.0 g ethanol and 68.0 g melted monoolein are mixed and form
an isotropic liquid. 27.0 g water is added. A viscous, isotropic
bulk cubic liquid crystalline gel forms. Example 17 shows that bulk
cubic liquid crystalline gels can be prepared according to the
methods of this invention.
Example 18
[0168] Cubic gel particles are prepared from the bulk cubic gel
prepared in Example 17 by applying ultrasonic energy for 5 minutes.
Images of the particles were obtained by the method of Reference
Example 2. The images are in FIG. 8c.
Example 19
[0169] A precursor is prepared by mixing 10.465 g monoolein with
4.45831 g water until cubic phase formed. The cubic phase is
diluted to L1 phase with 17.2242 g ethanol, and 0.0042 Sudan II red
dye is added to form a solution. The solution is put into a spray
bottle and sprayed on the leaves of a plant. After evaporation of
the ethanol, the leaves are visualized under a Nikon microscope
with 10.times. objective. Cubic phase forms on the leaves of the
plant.
[0170] This example shows that the precursors of this invention can
be used to form cubic liquid crystalline phases on plant
surfaces.
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