U.S. patent application number 12/746639 was filed with the patent office on 2010-12-02 for biodegradable single-phase cohesive hydrogels.
Invention is credited to Estelle Marie Piron, Guy Vitally.
Application Number | 20100303873 12/746639 |
Document ID | / |
Family ID | 39473297 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100303873 |
Kind Code |
A1 |
Piron; Estelle Marie ; et
al. |
December 2, 2010 |
BIODEGRADABLE SINGLE-PHASE COHESIVE HYDROGELS
Abstract
Biodegradable single-phase cohesive hydrogels useful, e.g., for
the formulation of viscosupplementation compositions or
compositions for filling wrinkles, contain a homogeneous blend of x
polymers, which may be identical or different, crosslinked prior to
the interpenetration thereof by mixing in the form of a
single-phase hydrogel, wherein such crosslinked polymers are
insoluble in water and miscible with one another, and x ranges from
2 to 5; in one embodiment, the hydrogels are such that the x
polymers have identical or different degrees of crosslinking, at
least one of the x polymers having a degree of crosslinking x1 and
at least one of the x polymers having a degree of crosslinking x2,
with x1 being greater than or equal to x2.
Inventors: |
Piron; Estelle Marie; (La
Bathie, FR) ; Vitally; Guy; (Le Bourget-du-Lac,
FR) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
39473297 |
Appl. No.: |
12/746639 |
Filed: |
December 8, 2008 |
PCT Filed: |
December 8, 2008 |
PCT NO: |
PCT/EP08/67029 |
371 Date: |
August 19, 2010 |
Current U.S.
Class: |
424/401 ; 514/54;
514/56; 514/57 |
Current CPC
Class: |
A61P 19/02 20180101;
A61K 8/042 20130101; A61L 27/26 20130101; A61K 8/733 20130101; A61L
27/52 20130101; A61K 2800/594 20130101; A61K 8/735 20130101; A61K
31/738 20130101; A61P 17/00 20180101; C08L 5/00 20130101; A61L
27/26 20130101; A61K 8/731 20130101; A61L 2400/06 20130101; A61P
13/02 20180101; A61P 27/02 20180101; A61P 17/16 20180101; A61L
27/58 20130101; A61K 8/736 20130101; A61K 2800/91 20130101; A61P
41/00 20180101; A61Q 19/08 20130101 |
Class at
Publication: |
424/401 ; 514/54;
514/57; 514/56 |
International
Class: |
A61K 8/73 20060101
A61K008/73; A61K 8/02 20060101 A61K008/02; A61Q 19/00 20060101
A61Q019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2007 |
FR |
07 59641 |
Claims
1.-24. (canceled)
25. A biodegradable single-phase cohesive hydrogel, comprising a
homogeneous mixture of x identical or different polymers,
crosslinked prior to their interpenetration by mixing, in the
single-phase hydrogel form, said crosslinked polymers being
insoluble in water and miscible with one another, and wherein x
ranges from 2 to 5.
26. The biodegradable single-phase cohesive hydrogel as defined by
claim 25, wherein the x polymers exhibit different degrees of
crosslinking, at least one of the x polymers exhibiting a degree of
crosslinking x1 and at least one of the x polymers exhibiting a
degree of crosslinking x2, with x1 being greater than or equal to
x2.
27. The biodegradable single-phase cohesive hydrogel as defined by
claim 25, wherein the x polymers exhibit identical degrees of
crosslinking.
28. The biodegradable single-phase cohesive hydrogel as defined by
claim 25, wherein the polymers comprise polysaccharides.
29. The biodegradable single-phase cohesive hydrogel as defined by
claim 28, wherein the polysaccharides are selected from the group
consisting of hyaluronic acid, keratan, heparin, cellulose and
derivatives thereof, alginic acid, xanthan, carrageenan, chitosan
and chondroitin and the biologically acceptable salts thereof.
30. The biodegradable single-phase cohesive hydrogel as defined by
claim 28, wherein the x polysaccharides are selected from the group
consisting of hyaluronic acid and the biologically acceptable salts
thereof.
31. The biodegradable single-phase cohesive hydrogel as defined by
claim 28, wherein at least one of the x polysaccharides is selected
from the group consisting of cellulose derivatives and the
biologically acceptable salts thereof.
32. The biodegradable single-phase cohesive hydrogel as defined by
claim 28, wherein at least one of the x polysaccharides is selected
from the group consisting of chondroitin and the biologically
acceptable salts thereof.
33. The biodegradable single-phase cohesive hydrogel as defined by
claim 28, wherein at least one of the x polysaccharides is selected
from the group consisting of chitosan and the biologically
acceptable salts thereof.
34. The biodegradable single-phase cohesive hydrogel as defined by
claim 25, wherein x is equal to 2.
35. The biodegradable single-phase cohesive hydrogel as defined by
claim 34, wherein the first of the x polymers is hyaluronic acid
and the second is selected from the group consisting of chondroitin
sulfate and salts thereof, chitosan and salts and derivatives
thereof, cellulose derivatives and salts thereof and alginic
acids.
36. The biodegradable single-phase cohesive hydrogel as defined by
claim 34, wherein the first of the x polysaccharides is selected
from the group consisting of hyaluronic acid and salts thereof,
cellulose derivatives and salts thereof and xanthan and the second
is selected from the group consisting of chondroitin sulfate and
salts thereof, chitosan and salts and derivatives thereof,
cellulose derivatives and salts thereof and alginic acids.
37. The biodegradable single-phase cohesive hydrogel as defined by
claim 25, further comprising one or more active principle(s)
selected from among antioxidants, antiseptics, anti-inflammatories
and local anesthetics, and mixtures thereof.
38. The biodegradable single-phase cohesive hydrogel as defined by
claim 37, comprising antioxidants selected from among mannitol
and/or sorbitol.
39. The biodegradable single-phase cohesive hydrogel as defined by
claim 37, comprising the local anesthetic lidocaine.
40. A process for the preparation of a biodegradable single-phase
cohesive hydrogel as defined by claim 25, comprising the stages of:
crosslinking a first polymer to a degree of crosslinking x1;
crosslinking a second polymer to a degree of crosslinking x2;
interpenetration by intimate mixing of the two polymers; hydration;
and final interpenetration by final mixing after hydration.
41. The process as defined by claim 40, comprising x stages of
crosslinking the x polymers before mixing the x crosslinked
polymers.
42. The process as defined by claim 40, wherein the crosslinkings
are carried out by the action of a polyfunctional crosslinking
agent selected from the group consisting of bi- or polyfunctional
epoxy compounds, divinyl sulfone, carbodiimides and
formaldehyde.
43. The process as defined by claim 40, wherein the crosslinking
agents employed in the crosslinking stages are identical or
different.
44. The process as defined by claim 40, wherein the degree of
crosslinking x1 is greater than or equal to the degree of
crosslinking x2.
45. The process as defined by claim 40, wherein the degrees of
crosslinking range from 0.02 to 0.4.
46. The biodegradable single-phase cohesive hydrogel as defined by
claim 25, formulated as a viscosupplementation composition.
47. The biodegradable single-phase cohesive hydrogel as defined by
claim 25, formulated as a composition for filling in wrinkles.
48. A kit comprising a biodegradable single-phase cohesive hydrogel
as defined by claim 25, packaged in a sterile syringe.
Description
[0001] The invention relates to the field of crosslinked
biodegradable hydrogels having esthetic applications, for example,
or medicinal applications.
[0002] Mention will be made, among the esthetic applications, for
example, of the filling in of fine lines, wrinkles and skin defects
and the increase in the volumes.
[0003] Mention will be made, among the medical applications, for
example, of periurethral injection for the treatment of urinary
incontinence by sphincter insufficiency, postsurgical injection for
preventing peritoneal adhesions in particular, injection for
replacement of deficient biological fluids (in the joints in
particular for replacing deficient synovial fluid) and injection
subsequent to surgery for far-sightedness by scleral incisions with
a laser.
[0004] In all these applications, the hydrogels used have to
exhibit optimized properties in terms of persistence in vivo, of
rheology and of viscosity in order to guarantee good
"injectability", these hydrogels being applied by injection using
needles of variable sizes depending on the applications but which
have to remain as fine as possible in order to minimize
postinjection reactions.
[0005] The optimization of these various properties results in
compromises which are often not very satisfactory as they are
sometimes incompatible. Specifically, in order to increase the
persistence in vivo, it is advisable to increase the degree of
crosslinking but, on increasing the degree of crosslinking, the
"injectability" is necessarily reduced.
[0006] Numerous solutions have been proposed and mention will be
made, among these, of compositions based on permanent or very
slowly biodegradable particles dispersed in an injection vector,
for example PMMA (polymethyl methacrylate) particles in a collagen
gel (Artecoll), acrylic hydrogel particles in a crosslinked sodium
hyaluronate gel (Dermalive, Dermadeep) or polylactic acid or
polylactide (PLA) particles in an aqueous vector (New Fill,
Sculptra, the PLA being resorbed in 1 to 4 years depending on the
size of the particles).
[0007] These implants are subject to controversy as a result of the
potential side effects due to the solid particles, in particular if
they are not round and if they have a permanent nature. Mention may
be made, among the complications listed, of inflammation, edema and
granuloma.
[0008] Mention may also be made of biodegradable implants based on
crosslinked or noncrosslinked polysaccharides essentially based on
sodium hyaluronate.
[0009] To get round these disadvantages, in the majority of the
documents of the prior art, for example in application FR 2 865
737, filed by Anteis S.A., or in FR 2 861 734, filed by Corneal
Industrie S.A., the products described are obtained by a
crosslinking carried out on a mixture of polymers in order to
obtain mixtures exhibiting the desired properties of persistence in
vivo, of rheology and of viscosity.
[0010] Another solution is recourse to interpenetrating polymer
networks IPN or semi-interpenetrating polymer networks (semi-IPN)
which make it possible to optimize the properties and to obtain
compositions exhibiting the targeted properties, such as, for
example, in application WO 2005/061611, filed by Innomed, which
describes compositions formed of semi-interpenetrating networks of
polysaccharides obtained by crosslinking at least one
polysaccharide in the presence of at least one other polysaccharide
which is not subject to crosslinking, or in U.S. Pat. No.
6,224,893, filed by MIT (Massachusetts Institute of Technology),
which describes compositions formed of at least two polysaccharides
which are subsequently crosslinked, for example by radiation, the
polymers being crosslinked independently of one another but while
being interpenetrating in order to form IPNs.
[0011] Injectable two-phase compositions have also been proposed.
Patent application FR 2 733 427 describes compositions which
comprise a continuous phase and a dispersed phase composed of
insoluble fragments of a hydrogel. The aqueous continuous phase
acts as vehicle for the injection of the fragments of the dispersed
phase.
[0012] However, these various solutions are not completely
satisfactory.
[0013] As regards the two-phase gels, the disadvantages in terms of
side reactions have been described in the literature and their
level of injectability is irregular as a result of the size of the
particles, which can be difficult to control.
[0014] Furthermore, the main mechanisms involved in the
decomposition of crosslinked polysaccharide gels are essentially
surface and random mechanisms, which are all the more pronounced
with regard to two-phase products exhibiting a greater
decomposition surface area.
[0015] As regards products obtained by carrying out crosslinking on
a mixture such as those described in application FR 2 865 737 or FR
2 861 734 or IPNs or semi-IPNs, although their perfect single-phase
or the interpenetration of the networks guarantee good persistence
in vivo and little or no side reaction, they do not make it
possible to provide a satisfactory solution as there are technical
difficulties in carrying out sometimes selective crosslinking
reactions on mixtures, in particular of natural polymers, due, for
example, to the variations in molecular weight. These products do
not make it possible to guarantee perfect reproducibility of the
physical properties from one batch to another, resulting in
difficulty in operating industrially.
[0016] The present invention makes it possible to solve these
various disadvantages.
[0017] The present invention consists of a biodegradable
single-phase cohesive hydrogel, characterized in that it is
composed of a homogeneous mixture of x identical or different
polymers, crosslinked prior to their interpenetration by mixing, in
the single-phase hydrogel form, said crosslinked polymers being
insoluble in water and miscible with one another and x being
between 2 and 5.
[0018] The cohesiveness and the single-phase nature of a gel
according to the invention is understood to mean the property of
said gel of retaining its stability and its unity without the
possibility of separation of the constituent gels.
[0019] The term "mixing" is understood to mean a juxtaposition of x
polymers without creation of a covalent bond between them.
Interactions take place between the various polymers due to the
presence of polar groups and of the aqueous medium; these
interactions are of the low energy weak bond type involving forces
such as, for example, intermolecular hydrogen bridges, indeed even
ionic bonds.
[0020] The mixture thus obtained exhibits properties comparable to
those of IPNs without being an IPN within the meaning of the IUPAC
definition; this is because this definition excludes mixtures of
networks crosslinked beforehand. In this instance, however, the
cohesive and crosslinked beforehand gels are intimately mixed,
generating weak interchain bonds between them.
[0021] They become indissociable from one another, thus generating
a network of intertwined crosslinked gels, the cohesiveness of
which is similar to that of IPNs.
[0022] Such a product exhibits the advantages of IPN networks
without the disadvantages of employing the latter and makes it
possible, by virtue of the use of a different degree of
crosslinking for each constituent gel (or an identical degree of
crosslinking, if the gels have very different molecular weights),
to create more or less dense networks before their final hydration
and, after mixing, to obtain a product having rheological
properties which can be "adjusted" by measuring the properties of
the various constituent gels before the mixing.
[0023] The crosslinking reactions can thus be carried out on
isolated polymers, thus avoiding the problems of selectivity.
[0024] Implementation is thus easy and makes it possible to meet
the final requirements while using natural products, the properties
of which, in particular the molecular weight, can vary from one
batch to another.
[0025] Furthermore, the implementation of the crosslinking
conditions is simple, each gel being crosslinked independently of
one another.
[0026] The mixture thus obtained will combine the advantages of
each of the various constituent gels while minimizing their
disadvantages, without bringing about the side effects observed
with the use of compositions based on particles.
[0027] An optimization and a synergy in the resulting properties
both in terms of injectability and in terms of persistence will be
observed.
[0028] The synergy is obtained as a result of the optimization of
the two parameters which act mutually on one another, low
crosslinking being favorable to the injectability and unfavorable
to the persistence and high crosslinking being favorable to the
persistence and, a contrario, unfavorable to the injectability.
[0029] The respective properties of the networks complement one
another; thus the gel with the highest elastic parameter will bring
about an increase in the elastic parameter of the combination, in
comparison with the least crosslinked gel. On the other hand, for
the injectability (related to the viscosity of the product), the
gel with the lowest level of injectability will make it possible to
reduce the level of injectability of the combination. The
characteristics of the final mixture are thus optimized, with a
synergy of the elastic and viscous parameters of the mixtures
obtained, which can be modified according to the respective
proportions of each of the constituent gels and the pathology
targeted.
[0030] It is thus possible to modify the viscosity of the mixture
by adjusting the proportion of each of the x polymers. In the case
of an excessively fluid final mixture, the addition of a highly
crosslinked polymer will make it possible to obtain a suitable
level of injectability. Conversely, in the case of an excessively
viscous final mixture, the addition of a weakly crosslinked polymer
will make it possible to reduce the degree of injectability of the
combination.
[0031] Thus, whatever the application targeted, the use of finer
needles than those generally used will make it possible to reduce
inflammatory reactions and postinjection traumas.
[0032] As the characteristics are reproducible, the persistence of
the gel will be known and predictable, apart from the factors of
inter-individual variation, and the reproducibility of the
injectability properties will make possible great control of the
action and the elimination of a number of side effects.
[0033] A hydrogel, because of its makeup, will exhibit
decomposition kinetics which depend on the number of gels mixed and
on the degrees of crosslinking. This is because the decomposition
kinetics depend on several parameters: the degree of crosslinking,
the concentration of polymer and the molecular weights of the
polymers used at the time of crosslinking.
[0034] The decomposition kinetics will be slowed down: this is
because to homogeneously mix gels with variable degrees of
persistence will make it possible to strengthen the overall
persistence by an effect of "diluting" the random cleavages of the
gel via either free radicals or enzymes (hyaluronidases, and the
like) present in the dermis or the biological fluid replaced. The
finished product thus manufactured will thus be more persistent for
equivalent levels of injectability, while remaining perfectly
biodegradable.
[0035] The persistence will also be optimized as a result of the
interpenetration of the networks, increasing the density of
crosslinks or chemical bonds while retaining the mechanical and
chemical independence of the 2 to x crosslinked gels. Thus, random
attack of the free radicals is statistically lower in comparison
with a simple single-phase gel (just 1 network, faster weakening of
the bonds at the surface, lower density of chemical bonds).
Accessibility to the core of the gel will also be rendered much
more difficult for decomposition by enzymes or via CD44 antigens.
Furthermore, the use of different molecular weights in each
single-phase gel crosslinked beforehand will make it possible to
form networks with a more or less dense structure or meshwork and
thus to further strengthen the persistence in vivo.
[0036] In one embodiment, the hydrogel according to the invention
is characterized in that the polymers are selected from
polysaccharides.
[0037] In one embodiment, the hydrogel according to the invention
is characterized in that the polymers are selected from the group
consisting of polylactic acids and their derivatives,
N-vinylpyrrolidone, polyvinyl acids, polyacrylamides and acrylic
polymers and biologically acceptable derivatives.
[0038] The polysaccharides are selected from the group consisting
of hyaluronic acid, keratan, heparin, cellulose and cellulose
derivatives, alginic acid, xanthan, carrageenan, chitosan,
chondroitin and their biologically acceptable salts.
[0039] In one embodiment, at least one of the x polysaccharides is
selected from the group consisting of hyaluronic acid and its
biologically acceptable salts.
[0040] In another embodiment, the hydrogel according to the
invention is characterized in that at least one of the x
polysaccharides is selected from the group consisting of cellulose
derivatives and their biologically acceptable salts.
[0041] In another embodiment, the hydrogel according to the
invention is characterized in that at least one the x
polysaccharides is selected from the group consisting of
chondroitin and its biologically acceptable salts.
[0042] In another embodiment, the hydrogel according to the
invention is characterized in that at least one of the x
polysaccharides is selected from the group consisting of chitosan
and its biologically acceptable salts and derivatives.
[0043] The polysaccharides which can be employed in the hydrogel
according to the present invention are of any type known in the
field and are preferably selected from those produced by bacterial
fermentation.
[0044] Generally, the polysaccharides which can be used in the
context of the present invention exhibit a molecular weight MW of
between approximately 0.02 and approximately 6 MDa, preferably of
between approximately 0.04 and approximately 4 MDa and more
preferably of between approximately 0.05 and approximately 3
MDa.
[0045] Preference is given in particular to hyaluronic acid and its
salts, especially its salts acceptable from the physiological
viewpoint, such as the sodium, potassium or calcium salts,
advantageously the sodium salt.
[0046] Use is also advantageously made of chondroitin sulfate and
its salts and cellulose derivatives, such as
hydroxypropylmethylcellulose or carboxymethylcellulose, and the
mixtures of two or more of them.
[0047] As sodium hyaluronate exhibits particularly advantageous
properties due to its high operating recoil in intradermal
injection, intra-articular injection, intra-peritoneal injection
and other injections, and also has excellent rheological
properties, the constituent gels of the hydrogel according to the
invention are preferably based on sodium hyaluronate.
[0048] In one embodiment, the x polymers are identical.
[0049] In one embodiment, the x polymers are different.
[0050] In one embodiment, the hydrogel according to the invention
is characterized in that x is equal to 2.
[0051] According to a specific embodiment, the first of the x
polysaccharides is selected from the group consisting of hyaluronic
acid and its salts, cellulose derivatives and their salts and
xanthan and the second is selected from the group consisting of
chondroitin sulfate and its salts, chitosan and its salts and
derivatives, cellulose derivatives and their salts and alginic
acids. In another specific embodiment, the first of the x polymers
is selected from the group consisting of hyaluronic acid and its
salts, cellulose derivatives and their salts and xanthan and the
second is selected from the group consisting of polylactic acids
and their derivatives and acrylic derivatives.
[0052] According to one embodiment, the first of the x polymers is
selected from the group of sodium hyaluronate and the second is
selected from the group consisting of chondroitin sulfate and its
salts, chitosan and its salts and derivatives, cellulose
derivatives and their salts and alginic acids.
[0053] In the hydrogel according to the present invention, the
ratio by weight of the highly crosslinked polysaccharide to the
weakly crosslinked polysaccharide can vary within very wide
proportions, according to the nature of the polysaccharides used,
their respective degrees of crosslinking and also the final
properties targeted.
[0054] Generally, the proportion by weight of the highly
crosslinked polysaccharide gel in the finished product is between
approximately 0.1 and 99.9%, preferably from 5 to 50%, of gel 1
exhibiting a degree of crosslinking x1 and from 50 to 95% of gel 2
exhibiting a degree of crosslinking x2 or even more preferably from
10 to 40% of gel 1 exhibiting a degree of crosslinking x1 and from
60 to 90% of gel 2 exhibiting a degree of crosslinking x2.
[0055] The invention also relates to the process for the
preparation of a biodegradable hydrogel according to the invention;
this process comprises a stage of developing specifications which
fix the rheological properties targeted as a function of the
applications.
[0056] For the determination of the degree of persistence, an
elasticity is targeted, that resulting from the degree of
crosslinking, and, for the determination of the injectability, the
viscosity at a high shear rate, also related to the degree of
crosslinking, is set; these parameters depend on the starting
materials, in particular on their molecular weight.
[0057] Having set the degrees of crosslinking and the respective
proportions of the constituent gels, the process for the
preparation of a biodegradable single-phase cohesive hydrogel
according to the invention is characterized in that it comprises at
least the stages of: [0058] crosslinking a first polymer to a
degree of crosslinking x1 [0059] crosslinking a second polymer to a
degree of crosslinking x2 [0060] interpenetration by intimate
mixing of the two polymers, [0061] hydration [0062] final
interpenetration by final mixing after hydration.
[0063] The hydration is carried out, for example, by immersion in
or addition of a buffered isotonic solution.
[0064] According to one embodiment, the process additionally
comprises x stages of crosslinking x polymers before mixing the x
crosslinked polymers.
[0065] The hydration is generally carried out in an aqueous medium
by simple mixing of the mixture of crosslinked gels with an aqueous
solution, advantageously a buffered physiological aqueous solution,
so as to obtain a final concentration which can vary within very
wide proportions according to the nature of the polysaccharides
used, their respective degrees of crosslinking and also the use
envisaged. The buffered solution which can be used can, for
example, be an osmolar physiological solution exhibiting a pH of
between approximately 6.8 and approximately 7.5.
[0066] This final concentration of total polysaccharides is
generally between approximately 5 and approximately 100 mg/g,
preferably between approximately 5 and approximately 50 mg/g, for
example approximately 20 mg/g, of hydrogel.
[0067] The process of the present invention thus makes it possible
to obtain a biodegradable single-phase cohesive hydrogel which can
be injected and with a long lasting persistence.
[0068] In the preparation process as described above, the two
crosslinking stages are carried out in a medium having a pH value
which is identical or different. Each of these stages can be
carried out in an acidic or basic medium, preferably in a basic
medium, for example at a pH of between 8 and 14, preferably between
8 and 13.
[0069] The crosslinking reactions employed in the process of the
invention are reactions well known to a person skilled in the art.
For each polysaccharide and/or crosslinking agent, a person skilled
in the art can develop and optimize the crosslinking conditions
according to said polysaccharide and said crosslinking agent:
degree of crosslinking, temperature, pH. However, it is specified
that the crosslinking stages are carried out at constant pH, either
acidic pH or basic pH, as indicated above.
[0070] The crosslinking agents which are involved in the
crosslinking stages are generally bi- or polyfunctional
crosslinking agents of various types and can, for example, be
selected from DVS (divinyl sulfone) in an alkaline medium (see U.S.
Pat. No. 4,582,865), bi- or polyfunctional epoxy compounds (see
U.S. Pat. No. 4,716,154), carbodiimides, or formaldehyde (see GB 2
151 244).
[0071] Preference is given in particular to agents of bi- or
polyepoxide type, the reactions taking place in a basic medium, to
generate ether bonds with the --OH functional groups of the
polysaccharide, or in an acidic medium, which gives rise to bonds
of ester type. Patent application WO 2000/46253 successively uses
these two pH conditions in order to optimize the crosslinking of
the polysaccharide. However, it is preferable to carry out the
crosslinking reactions under basic pH conditions since, in an
aqueous medium, the ester bonds resulting from an acid medium are
generally more labile than the ether bonds resulting from a basic
medium.
[0072] Use may be made, as crosslinking agent, of an epoxide or its
derivatives and in particular 1,4-butanediol diglycidyl ether
(BDDE), diepoxyoctane or 1,2-bis(2,3-epoxypropyl)-2,3-ethylene.
Preference is very particularly given to the use of 1,4-butanediol
diglycidyl ether (BDDE) for each of the crosslinking stages.
[0073] It should be understood that each of the crosslinking stages
can be carried out with one or more crosslinking agents, it being
possible for the latter to be identical or different in one or
another of the stages, under the pH conditions indicated above.
[0074] After each of the crosslinking stages, the polysaccharides
can advantageously be purified according to conventional
purification techniques (for example by washing with a continuous
stream of water, dialysis baths, and others), in order to remove
the unreacted residual crosslinking agent.
[0075] In addition, the crosslinking stages can advantageously be
followed by a neutralization stage (i.e., neutralization as far as
a pH value of approximately 7), for example by addition of an
appropriate amount of 1N hydrochloric acid.
[0076] In the hydrogel according to the invention, the x polymers
exhibit different degrees of crosslinking, at least one of the x
polymers exhibiting a degree of crosslinking x1 and at least one of
the x polymers exhibiting a degree of crosslinking x2, and x1 being
greater than x2.
[0077] In one embodiment, in the hydrogel according to the
invention, the x polymers exhibit identical degrees of
crosslinking, it being understood that the polymers can have
different molecular weights.
[0078] In one embodiment, x1 and x2 are between 0.02 and 0.4 and
preferably between 0.08 and 0.2.
[0079] On conclusion of the crosslinking, it may be advantageous to
neutralize the gel obtained according to standard processes known
in the field, for example by addition of acid, when the
crosslinking is carried out in a basic medium, and by addition of a
base, when the crosslinking is carried out in an acidic medium.
[0080] The mixture obtained on conclusion of the process can
optionally be subjected to an additional hydration stage, in order
to obtain a gel in the form of an injectable hydrogel suitable for
the applications envisaged.
[0081] The invention relates to the use of a hydrogel according to
the invention in the formulation of a viscosupplementation
composition.
[0082] The invention relates to the use of a hydrogel according to
the invention in the formulation of a composition for filling in
wrinkles.
[0083] The applications targeted are more particularly the
applications commonly observed in the context of injectable
polysaccharide viscoelastic products used or which can potentially
be used in the following pathologies or treatments: [0084] cosmetic
injections: for filling in wrinkles, skin defects or defects of
volume (cheekbones, chins, lips); [0085] treatment of
osteoarthritis, injection into the joint to replace or supplement
deficient synovial fluid; [0086] periurethral injection in the
treatment of urinary incontinence by sphincter insufficiency;
[0087] postsurgical injection for preventing peritoneal adhesions
in particular; [0088] injection subsequent to surgery for
far-sightedness by scleral incisions using a laser; [0089]
injection into the vitreous cavity.
[0090] More particularly, in cosmetic surgery, according to its
viscoelastic properties and properties of persistence, the hydrogel
according to the invention can be used: [0091] for filling in fine,
moderate or deep wrinkles and can be injected with thin needles
(27-gauge, for example); [0092] as volumizing product with
injection via needles with a larger diameter, for example from 22-
to 26-gauge, and with a greater length (30 to 40 mm, for example);
in this case, its cohesive nature will make it possible to
guarantee that it is maintained at the site of the injection.
[0093] The hydrogel according to the invention also has an
important application in joint surgery and in dental surgery for
filling in periodontal pockets, for example.
[0094] These implementational examples are in no way limiting, the
hydrogel according to the present invention being more widely
provided for: [0095] filling in volumes; [0096] generating spaces
within certain tissues, thus promoting their optimum functioning;
[0097] replacing deficient physiological fluids.
[0098] The hydrogel according to the invention can also have an
entirely advantageous application as matrix for releasing one (or
more) active principle(s) dispersed beforehand within it. The term
"active principle" is understood to mean any product which is
active pharmacologically: medicinal active principle, antioxidant
active principle (sorbitol, mannitol, and the like), antiseptic
active principle, anti-inflammatory active principle, local
anesthetic active principle (lidocaine, and the like), and the
like.
[0099] In practice, the hydrogel according to the invention,
preferably after purification and hydration to give the hydrogel,
can be packaged, for example in syringes, and sterilized according
to any means known per se (for example by autoclaving) in order to
be sold and/or used directly.
[0100] According to another aspect, the present invention relates
to a kit comprising a hydrogel according to the invention packaged
in a sterile syringe.
[0101] The characteristics of the gels according to the invention
are demonstrated in the examples below.
EXAMPLES
Degree of Crosslinking
[0102] The degrees of crosslinking x in the examples which follow
are defined by:
[0103] x=number of moles of crosslinking agent introduced into the
reaction medium/total number of disaccharide units introduced into
the reaction medium.
Example 1
Crosslinking Gel 1
Stage a): Hydration of Sodium Hyaluronate Fibers in the Form of a
Noncrosslinked Gel
[0104] Sodium hyaluronate fibers of injectable grade (1 g:
molecular weight: approximately 2.7 MDa) are weighed out in a
container. A 1% aqueous solution of sodium hydroxide in water (7.4
g) is added and the combined mixture is homogenized for
approximately 1 hour using a spatula at ambient temperature and 900
mm Hg.
Stage b): Crosslinking
[0105] BDDE (65 mg) is added to the noncrosslinked sodium
hyaluronate (NaHA) gel obtained in the preceding stage, the
combined mixture being homogenized with a spatula for approximately
30 minutes at ambient temperature. The combined mixture is
subsequently placed on a water bath at 50.degree. C. for 2 h 20 in
order to obtain a degree of crosslinking x1 of approximately
0.14.
Stage c): Neutralization, Purification
[0106] The crosslinked final gel is subsequently neutralized by
addition of 1N HCl and placed in a phosphate buffer bath in order
to stabilize the pH and to make possible its hydration or swelling
as far as 30 mg/g of HA. An NaHa hydrogel crosslinked by the route
conventionally used is thus obtained: G1 with an HA concentration
of approximately 30 mg/g.
[0107] A portion of the gel is stored at this concentration and the
other portion is diluted by addition of phosphate buffer in order
to obtain, at the end, 20 mg/g of HA. This gel is subsequently
homogenized before being filled into syringes which are sterilized
by autoclaving: sterile syringes comprising gel G1 at 20 mg/g.
Crosslinking Gel 2
Stage a): Hydration of Sodium Hyaluronate Fibers in the Form of a
Noncrosslinked Gel
[0108] Sodium hyaluronate fibers of injectable grade (1 g;
molecular weight: approximately 1.5 MDa) are weighed out and dried
beforehand in a container. A 1% aqueous solution of sodium
hydroxide in water (6.3 g) is added and the combined mixture is
homogenized for approximately 1 hour using a spatula at ambient
temperature and 900 mmHg.
Stage b): Crosslinking
[0109] BDDE (43 mg) is added to the noncrosslinked sodium
hyaluronate (NaHA) gel obtained in the preceding stage, the
combined mixture being homogenized with a spatula at ambient
temperature and atmospheric pressure for approximately 30 minutes.
The combined mixture is subsequently placed on a water bath at
50.degree. C. for 2 h 20 in order to obtain a degree of
crosslinking x2 of approximately 0.09.
Stage c): Neutralization, Purification
[0110] The crosslinked final gel is subsequently neutralized by
addition of 1N HCl and placed in a phosphate buffer bath in order
to stabilize the pH and to make possible its hydration or swelling
as far as 30 mg/g of HA. An NaHa hydrogel crosslinked by the route
conventionally used is thus obtained: G2 with an HA concentration
of approximately 30 mg/g.
Example 2
[0111] Mixing/interpenetration of Gel 1 and Gel 2 in the
proportions 10% G1-90% G2
[0112] Mixing/interpenetration of the gels G1 and G2 at 10%/90%
[0113] 18 g of gel G2 at 30 mg/g are weighed out and 2 g of gel G1
obtained at the end of the preceding stage c) (G1 at 30 mg/g) are
added thereto. 10 g of phosphate buffer are added and the 2 gels
are placed under slow mechanical stirring for 1 h under hyperbaric
pressure.
[0114] The mixture thus obtained is a homogeneous gel comprising 20
mg/g of HA and composed of 2 inter-penetrating networks; this gel
is then packaged into syringes and autoclaved.
Example 3
[0115] Mixing/interpenetration of Gel 1 and Gel 2 in the
proportions of 50%-50%
[0116] The gels obtained at the end of stage c) of each example
above: gel 1 crosslinked to x1 approximately 0.14 and G2
crosslinked to x2 approximately 0.09, both with a concentration of
approximately 30 mg/g of HA, are weighed out: 10 g of G1+10 g of
G2.
[0117] 10 g of phosphate buffer are also added and the 2 gels are
placed under slow mechanical stirring for 1 h under hyperbaric
pressure.
[0118] The mixture thus obtained is a homogeneous gel comprising 20
mg/g of HA and composed of 2 inter-penetrating networks; this gel
is then packaged into syringes and autoclaved.
Example 4
[0119] Characterization of the gels of examples 1 and 2: [0120] gel
G1 crosslinked to x1, [0121] mixture of 10% G1 and 90% G2
crosslinked to x2, [0122] mixture of 50% G1 and 50% G2, these 3
final products being all 3 at a final concentration of 20 mg/g of
HA.
[0123] Characterization of the extrusion force or
"injectability":
[0124] This test is carried out on the gels packaged into syringes
and sterilized, with 27G1/2 needles, on a tensile compression
testing machine with a rate of compression of 13 mm/min. The
results of the extrusion forces of each of examples 1, 2 and 3 are
given in the table below:
TABLE-US-00001 Gel tested Injectability (N) Gel 1 37 10% Gel 1 +
90% Gel 2 21 50% Gel 1 + 50% Gel 2 31
[0125] A lower injectability of the interpenetrating networks of
crosslinked gels in the comparison with the gel G1 alone is clearly
observed.
Decomposition Test
[0126] These various gels were also characterized by an in vitro
temperature decomposition test. This test makes it possible to
simulate the subsequent in vivo persistence of the gels injected
intradermally. It was developed on the basis of the specifications
of the test of persistence described in patent FR 2 861 734. The
gels were all placed in an oven at 93.degree. C. for 14 h, 24 h and
48 h, with characterization of the elasticity after each time. The
curves of the trend in the decomposition results for these various
gels subsequently make it possible to evaluate the half-life of
these various gels (period of time necessary to have G'=G'0/2, in
hours, with G'0=elasticity at t0 of the gel characterized). The
half-lives obtained are also given in the table below.
TABLE-US-00002 Gel tested 1/2 life (hours) Gel 1 19 10% Gel 1 + 90%
Gel 2 22.5 50% Gel 1 + 50% Gel 2 20.5
[0127] A greater decomposition is observed for Gel 1 alone, in
comparison with the two interpenetrating networks of gels
crosslinked beforehand.
[0128] Thus, for lower injectability and thus better control of the
surgical action, the half-lives of the interpenetrating networks of
gels obtained according to the invention are longer, guaranteeing a
greater time of in vivo persistence.
Example 5
[0129] In order to confirm the cohesiveness and the single-phase
nature of the hydrogels according to the invention, manual
centrifuging tests of 3 times 5 minutes were carried out on the
10/90 and 50/50 mixtures comprising 20 mg/g of NaHA obtained in the
preceding examples.
[0130] By comparison, a product of "two-phase" type, such as
described in the prior art, was prepared according to the procedure
of patent EP 0 466 300 with 50% of crosslinked NaHA particles
dispersed in 50% of noncrosslinked NaHA viscous product, the two
phases having been hydrated beforehand in phosphate buffer,
comprising 20 mg/g of NaHA.
[0131] The products according to the invention obtained in the
preceding examples do not show any separation on settling; the
product, if ejected after the centrifuging operations, still has a
homogeneous appearance.
[0132] On the other hand, the product of "two-phase" type shows,
after centrifuging, separated particles at the bottom of the
syringe. If the product is ejected from the syringe, the viscous
product exits first, followed by the particles, which have no
cohesiveness with one another, agglomerated at the bottom of the
syringe, and which render the injectability particularly
difficult.
Example 6
[0133] Mixing/interpenetrating of the gels G1 and G2 of example 1,
in order to finally obtain gels and mixtures of gels at a
concentration of 25.5 mg/g according to the process described in
example 2 with adjustment of the NaHA concentrations by addition of
phosphate buffer, in the following proportions:
[0134] IPN-Like Gel 1: 70% Gel 1 cross. x1+30% Gel 2 cross. x2
[0135] IPN-Like Gel 2: 50% Gel 1 cross. x1+50% Gel 2 cross. x2
[0136] IPN-Like Gel 3: 30% Gel 1 cross. x1+70% Gel 2 cross. x2
[0137] These gels are then packaged into syringes and sterilized by
autoclaving.
[0138] Characterization of the extrusion force and of the
elasticity of these IPN-like gels and of Gel 1 cross-linked to x1
and brought to an NaHA concentration of 25.5 mg/g:
[0139] The extrusion force is characterized on a Mecmesin
tensile/compression testing machine under a rate of compression of
50 mm/min with 23G1 1/4 needles; the results are given in the table
below.
[0140] The elasticity is characterized on a TA Instruments AR2000
Ex rheometer in oscillation at 25.degree. C., the value of the
elasticity being recorded at a frequency of 1 Hz; the results are
given in the table below.
TABLE-US-00003 Interpene- Interpene- Interpene- Gel 1 at trating
Gel 1 trating Gel 2 trating Gel 3 25.5 mg/g 25.5 mg/g 25.5 mg/g
25.5 mg/g Extrusion force 63 61 61 57 (N) 23G11/4 need. Rate 50
mm/min Elasticity: G' (Pa) 200 225 244 265 at 1 Hz
[0141] It is observed, with regard to the 3 interpenetrating gels,
that the extrusion forces are fairly close but all less than that
of Gel 1, for increasing elasticities. Thus, the use of this
technique of interpenetrating crosslinked gels makes it possible to
obtain finished products of variable rheology: increasing
elasticity (thus a better volumizing effect and a greater expected
persistence) for lower levels of injectability.
Example 7
[0142] Synthesis of Gel 3: A gel is synthesized according to the
protocol/operating conditions of example 1, Gel 1:
Stage a): Hydration of Sodium Hyaluronate Fibers in the Form of a
Noncrosslinked Gel
[0143] This stage is identical to stage a) of the synthesis of Gel
1 of example 1.
Stage b): Crosslinking the Gel
[0144] This stage is identical to stage b) of the synthesis of Gel
1 of example 1, with 81 mg of BDDE. A Gel 3 with a degree of
crosslinking x3 of approximately 0.17 is obtained.
Stage c): Neutralization, Purification
[0145] This stage is identical to stage c) of the synthesis of Gel
1 of example 1, in order to obtain a gel G3 with an HA
concentration of approximately 30 mg/g.
[0146] A portion of the gel is stored at this concentration and the
other portion is diluted by addition of phosphate buffer in order
to finally obtain 24 mg/g of HA; this gel is subsequently
homogenized before being filled into syringes which are sterilized
by autoclaving: sterile syringes comprising gel G3 at 24 mg/g.
Interpenetration Gel 1/Gel 3 in the proportions 80/20:
[0147] 16 g of gel G1 at 30 mg/g are weighed out and 4 g of gel G3
at 30 mg/g, obtained at the end of the preceding stage c), are
added thereto. 5 g of phosphate buffer are added and the 2 gels are
placed under slow mechanical stirring for 1 h.
[0148] The mixture thus obtained is a homogeneous gel comprising 24
mg/g of HA and composed of 2 inter-penetrating networks; this gel
is then packaged into syringes and autoclaved.
[0149] Characterization of the gels and interpenetrating gels
described above: [0150] Gel 3 with a degree of crosslinking x3, at
24 mg/g, [0151] Gel 1 with a degree of crosslinking x1 and brought
beforehand to 24 mg/g, packaged into syringes and sterilized,
[0152] and the mixture of interpenetrating gels 80% Gel 1+20% Gel
3, at 24 mg/g.
[0153] These gels are characterized by extrusion force. The tests
are carried out with 27G1/2 needles on a Mecmesim
tensile/compression testing machine with a rate of compression of
13 mm/min. The results for the extrusion forces of each of these
gels are given in the table below.
[0154] These gels are also characterized by the in vitro
temperature decomposition test described in example 4.
[0155] The 1/2 lives obtained are also given in the table
below.
TABLE-US-00004 Extrusion force (N) 27G1/2 needle - 1/2 life 13
mm/min (hours) Gel 1 - x1 - 24 mg/g 27 17 Gel 3 - x3 - 24 mg/g 30
21 80% Gel 1/20% Gel 3 - 24 mg/g 23 20.5
[0156] Thus, an equivalent persistence is observed for the
interpenetrating gel and for Gel 3 crosslinked to the highest
degree x3, for a lower level of injectability of this
interpenetrating gel.
Example 8
[0157] Synthesis of 3 single-phase crosslinked gels according to
examples 1 and 2: [0158] Gel 4: Stage a): identical to stage a) for
the synthesis of Gel 1 of example 1 with 1 g of HA with a molecular
weight of approximately 2.7 MDa and 6.8 g of a 1% aqueous solution
of sodium hydroxide in water. The homogenization conditions are the
same as in example 1. Stage b): Crosslinking: identical to stage b)
of the synthesis of Gel 1 of example 1 with 62 mg of BDDE. The
combined product is brought to 50.degree. C. on a water bath for 3
hours, in order to obtain a degree of crosslinking x4 of
approximately 0.13. Stage c): Neutralization, purification:
identical to stage c) of the synthesis of Gel 1 of example 1, in
order to obtain a Gel 4 at 30 mg/g. A portion of the gel is stored
at this concentration and the other portion is diluted by addition
of phosphate buffer in order to finally obtain 24 mg/g of HA; this
gel is subsequently homogenized before being filled into syringes
which are sterilized by autoclaving: sterile syringes comprising
gel G4 at 24 mg/g. [0159] Gel 5: Stage a): identical to stage a) of
the synthesis of Gel 4. Stage b): Crosslinking: identical to stage
b) of the synthesis of Gel 4 with 80 mg of BDDE. The combined
product is brought to 50.degree. C. on a water bath for 3 hours, in
order to obtain a degree of crosslinking x5 of approximately 0.17.
Stage c): Neutralization, purification: identical to stage c) of
the synthesis of Gel 4 in order to obtain a Gel 5 at 30 mg/g. A
portion of the gel is stored at this concentration and the other
portion is diluted by addition of phosphate buffer in order to
finally obtain 24 mg/g of HA; this gel is subsequently homogenized
before being filled into syringes which are sterilized by
autoclaving: sterile syringes comprising gel G5 at 24 mg/g. [0160]
Gel 6: Stage a): identical to stage a) of the synthesis of Gel 2 of
example 1 with 1 g of sodium hyaluronate with a molecular weight of
approximately 1.3 MDa and 5.7 g of a 1% aqueous solution of sodium
hydroxide in water.
Stage b): Crosslinking
[0161] Identical to stage c) of example 1 with 41 mg of BDDE. The
combined product is brought to 50.degree. C. on a water bath for 3
hours, in order to obtain a degree of crosslinking x6 of
approximately 0.09.
Stage c): Neutralization, Purification
[0162] Identical to stage c) of the synthesis of the preceding Gel
5 in order to obtain a Gel 6 at 30 mg/g. A portion of the gel is
stored at this concentration and the other portion is diluted by
addition of phosphate buffer in order to finally obtain 24 mg/g of
HA; this gel is subsequently homogenized before being filled into
syringes which are sterilized by autoclaving: sterile syringes
comprising gel G6 at 24 mg/g.
Interpenetration of Gels 4, 5 and 6 (respective proportions: 25%,
5% and 70%)
[0163] 5 g of gel G4 at 30 mg/g are weighed out, 1 g of gel G5 at
30 mg/g is weighed out and then 14 g of gel G6 at 30 mg/g are
weighed out. 5 g of phosphate buffer are added and the 3 gels are
placed under slow mechanical stirring for 1 h. A final single-phase
gel G7 comprising 24 mg/g of sodium hyaluronate and composed of 3
interpenetrating single-phase crosslinked gels is thus
obtained.
[0164] Characterization of the elasticity and of the extrusion
force of the 3 conventional gels and of the interpenetrating
mixture:
[0165] according to the methods described in the preceding
examples.
TABLE-US-00005 Gel G7 (inter- penetrating Gel 4 Gel 5 Gel 6 4, 5
and 6) 24 mg/g 24/mg 24 mg/g 24 mg/g Extrusion force (N) 31 38 18
16 23G11/4 need. Rate 13 mm/min Elasticity: G' (Pa) 245 415 186 224
at 1 Hz
[0166] Gel G7, composed of the interpenetration of the 3
crosslinked gels (G4, G5 and G6), has the lowest extrusion force,
for an elasticity value greater by approximately 20% than that of
the gel G6 with a close but slightly greater level of
injectability.
[0167] Its elasticity is lower by only 10% with respect to that of
Gel 4, the level of injectability of which is greater by more than
40%.
[0168] The advantage of these interpenetrating gels is clearly
perceived.
Example 9
[0169] Interpenetration of crosslinked HA and crosslinked CMC
(carboxymethyl cellulose) gels [0170] Crosslinked CMC gel: gel
G8
Stage a): Hydration of NaCMC in the Form of a Noncrosslinked
Gel
[0171] 1 g of sodium carboxymethyl cellulose with an intrinsic
viscosity (supplied by Sigma) is weighed out in a container. A 1%
aqueous solution of sodium hydroxide in water (7.3 g) is added and
the combined mixture is homogenized for approximately 90 minutes
using a spatula at ambient temperature and 900 mmHg.
Stage b): Crosslinking
[0172] BDDE (37 mg) is added to the noncrosslinked CMC gel obtained
in the preceding stage, the combined mixture being homogenized with
a spatula for approximately 30 minutes at ambient temperature. The
combined mixture is subsequently placed on a water bath at
50.degree. C. for 3 h in order to obtain a degree of crosslinking
x8 of approximately 0.19.
Stage c): Neutralization, Purification
[0173] The crosslinked final gel is subsequently neutralized by
addition of 1N HCl and placed in a phosphate buffer bath in order
to stabilize the pH and to make possible its hydration or swelling
as far as 45 mg/g of CMC. An NaCMC hydrogel crosslinked by the
route conventionally used is thus obtained: G8 with a CMC
concentration of approximately 45 mg/g. [0174] Interpenetration of
HA gel G1 and CMC gel G8
[0175] The HA gel G1 crosslinked to a level of 0.14, at a
concentration of 30 mg/g, is added in various proportions to the
crosslinked NaCMC gel G8, the phosphate buffer is added in order to
adjust the final concentrations to 26 mg/g of HA and 37 mg/g of CMC
and the 2 gels are placed under slow mechanical stirring with the
phosphate buffer for 1 hour under hyperbaric pressure. 3
interpenetrating gels as described below are thus obtained: [0176]
Gel 9: 30% G1+70% G8 [0177] Gel 10: 50% G1+50% G8 [0178] Gel 11:
70% G1+30% G8
[0179] These 3 interpenetrating gels are subsequently packaged into
syringes and characterized by rheology (elastic modulus G') and by
injectability under a rate of 13 mm/min with 27G1/2 needles. The
gels G1 and G8 are also adjusted to the concentrations of 26 mg/g
for G1 and 37 mg/g for G8 in order to compare them with the 3
interpenetrating gels.
[0180] The results of the characterizations are combined in the
table below.
TABLE-US-00006 G1 G8 G9 G10 G11 (cross- (cross- Interpene-
Interpene- Interpene- linked HA, linked CMC, trating gel trating
gel trating gel 26 mg/g) 37 mg/g) 30% G1 + 70% G8 50% G1 + 50% G8
70% G1 + 30% G8 Elastic modulus 235 265 240 243 264 G' at 1 Hz (Pa)
Injectability 33 18 18 12 16 27G1/2 need. (N)
[0181] A virtually constant elastic modulus is observed for the 5
interpenetrating or non-interpenetrating gels but with lower levels
of injectability for the inter-penetrating gels than for each
independent crosslinked gel, with a high synergistic effect with
regard to the 50/50 mixture (Gel 10).
* * * * *