Note: Descriptions are shown in the official language in which they were submitted.
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CONTROLLED RELEASE COMPOSITIONS COMPRISING GELLAN GUM GELS
?he present invention relates to a composition and method for the
e~active controlled timed release of various molecular weight biologically
active
molecules ragging from small molecular weight vitamins to largo proteins to an
intaided recipient such as a human or animal in an therapeutically effective
manner
and amount employing gellan gum.
BACKGROUND OF TIC SON
Facapsulation of ingredients in gels, such as gellan gum, is known.
For example, Japanese Patent No. 62125850 discloses encapsulation of
ingredicats,
such as food, oils, medicines aad the like, within beads of gellan gum. This
published
patent applicatioa reports that in as example, a salad oil emulsion was added
as O.SmI
size drops to a 1% gellan gum solution. This publication reports that
resulting beads
had a 0.35mm thick skin gad contained 0.3m1 of oil in each sphere.
U.S. Pateat No. 4,553.366 discloses a gelled food product which
comprises a matrix containing at least one dispersed food ingredient which
comprises
vegetable, fruit, meat, fish, sugar, and/or mill:.
GB Patent No. 2219803 discloses a gelling composition which
comprises a blend of gellan, kappa-carrageenan and mattnan. This gelling
composition is said to be useful as a gelling matrix in food products such as
pet foods
and the like.
Japanese Patern No. 63267361 discloses a gel which is said to contain
fragrances, microbicides, insecticides, and the like, in addition to a
gelation agent
selected from gellaa gum, and its combination with carrageenan, gelatin, agar,
locust
baaa, gum, xanthan gum, carboxymethyl cellulose and the like.
Most conventional tablets are hard to swallow, especially for children
and the elderly. It is proposed that gellan gum gels, with their moist jelly-
like easy to
swallow texture, can present an attractive alternative for oral delivery. The
gel
structure could be swallowed by itself or suspended in a liquid formulation.
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However, controlled release of biologically active molecules .is desired
in particular when the bioavailability of the biologically active molecule is
required to
be delivered in an effective manner over a long period of time (i.e. several
hours)
and/or with constant release rato, and/or independently of dosage strength.
OHJECTNES OF TIC INVENTrON
It is an objective of the invention to provide a control release system.
This and other objects arc met in this invention which is described in detail
hereinafter.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides a composition and a method whereby
gellan gum gals can be used effectively to, release biologically active
molecules in an
effective controlled release manner over time. A method is also provided for
setting,
adjusting and regulating the release characteristics for as intended recipient
and user
such as a human or an animal. A therapeutic effective amount of active
ingredient is
delivered to the recipient by this invernion.
DETAILED DESCRIPTION OF THE INVENTION
According in one embodiment of the present invention, a gellan gum is
provided with an effective pore size range that can be easily modified to
affect the
release characteristics of a biologically active molecule to its intended
recipient such
as a human or an animal.
Accordingly, the present invention, enables a "tunable" release of
biologically active molecules to the intended target over, during and after a
desired
time.
Such tuning can be achieved in several ways including by varying gum
concentration, the nature and concentratiaa of gelling canons, and by
incorporating
other polymers in the gel nerwork. A polymer of choice to be added to gellan
gum gel
is xantban gum. Increasing the concentration of xanthan gum in the gel
increases the
viscosity in the gel and reduce its effective gore size. One skilled in the
art will
recognizo that affecting the average effective pore size or the viscosity is
the gel will
affect tho release characteristics of such system after reading this
specification.
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A useful property of gellan gum for the present invention is its ability
to gel with most canons, including counter ions of the biologically active
molecule to
be incorporated into the gel. Aptly, the gel phase employed in this invention
comprises a gellaa gum.
Gellan gum refers to and includes the extracellular polysaccharide
obtained by the aerobic fermentation of the microorganism, Sphtngonsonaa
elodea, in
a suitable nutrient medium. Various forms of gellan gum are known (e.g.,
native,
deaeylated, dcacylated clarified, partially deacylated, and partially
deacylated
clarified) and may be employed as a gel in practicing this invention. Mixtures
thereof
may be employed.
It is preferred that the gellan gum employed in a gel of this invention
comprises a "low acyl" gellaa gum. As used herein, the term "low acyl" denotes
a
level of acylanon of the gellan gum of about 0.3 to about 30% by weight
although
gellan gum with greater or lower acylation levels may be employed in
practicing this
invention if desired. Another way for tuning release characteristics from the
gel
would be to mix some native gellan gum (high aryl content) with its deacylated
form.
Gellan Gum is a naturally occuring polysaccharide that is product by
inoculating a carefully formulated fermentation medium with the microorganism
Sphingomonas elodea (ATTC 31461 ). Gellan gum is available in clarified form
KELOGEL~ for foods and industrial products and a clarified form GELRITE c$
from
Monsanto Company, St. Louis, Missouri, for microbioiogical media, plant
tiessue
culture and pharmaceutical applications. The gelling mechanism of Gellan Gum
is
based on canon inducted macromolecular chain reorganization. Gellan gum
includes
nonclarified, clarified, and partially clarified native, deacylated and
partial deacylated
forms as well as mixtures thereof and the like.
A process for the preparation of gels useful herein comprises admixing
water with gellan gum to a concentration from about 0.1 % to about 5% by
weight to
form a gum containing composition, with or without sequestrant, optionally
with other
polymers, and maintaining said gum composition at a tempaatme su~ciently warm
to maintain full hydration of said gum such that gelanon will occur upon
subsequent
cooling. A biologically-active ingredient may then be admixed with the warm
solution
along with optionally admixing solubilizing and suspending aids. Further
optionally
admixing therewith includes cartons. Cooling the warm solution containing said
biologically active ingredient to a temperature in the range sufficient to
induce
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gelation then follows. The biologically active ingrediem is thus within the
gcllod
gum.
It is preferred that tho gellan gum be present in the gelled phase in an
amount of about 0.1 to about 5% by weight, based on the weight of the gelling
agem
in water, for example, about 0.25 to about 2.5% by weight although grcatar or
lessor
amounts may be employed if desired.
The gelled phase may also optionally contain a preservative. A
preferred preservative is n-propyl p-hydroxybenzoato and the like. The
preservative is
suitably employed in a minor amount, such as not greater than about 0.2% by
weight
of the gelled phase although greater or lesser amounts may be employed if
desired.
Optionally, if desired, the golfed phase may feather contain a biocide,
typically present in an amount of about 0.05% to about 2.5% by weight based on
the
weight of the gelled phase although greater or lesser amounts may be employed
if
desired.
If desired, the gellan gum may typically be gelled by a suitable cation
such as calcium, magnesium, mixtures thereof and the like. A particularly
attractive
method of inducing gclation is to use the counter ion of biologically active
molecules)
to be incorporated into the gel.
The form and texture of the gel will depcad on the desired application.
For cxamplo, to be used as an oral (intact) delivery system care should be
taken to
obtain a gel hard enough to be handled easily by hand without breaking or
damage to
the gal. If the gol needs to be mixed with food, a softer, easier to break gel
structure
maybe desirable. Such change of texture can easily be adjusted by the person
skilled in
the art by varying gum and cation concentration and other optional additives
after
reading this specification.
If one of skill in the art should desire to employ multivalent gelling
canons, these illustrative canons could be suitably provided by salts such as
calcium
chloride, magnesium chloride, calcium sulphate, magnesium sulphate, mixtures
thereof and the like. Other suitable rations may be employed if desired,
including
that of the biologically active molecule(s).
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1n an instance where monowalerat gelling canons are employed in
practicing this invention, it is preferred that the gelling solution remains
substantially
free of multivalent ions, such as calcium, magnesium or the like. One of skill
in the
art will appreciate that it is normal practice in the art to use multivalent
ions to
increase gel strength.
As hereinbefore described, an object of the present invention is to
contain within a gel having effective release properties a biologically active
ingredient
for its subsequent controlled release from the gel. Aptly, the active
ingredients
comprise small molecules or largerprotcins whose release characteristics may
be
different and can be tuned in different ways for effective release to a human
or animal
as has been discovered in this invention.
Examples of such biologically active molecules includes without
limitation, for small species, ascorbic acid (vitamin C), sodium naproxen,
sodium
salicylate, ibuprofen and for larger proteins, insulin, myoglobin, bovine
somatotmpin,
and albumin, mixtures thereof and the like. Those of skill in the art will
recognize
that other biologically active molecules may be employed equally well in
practicing
this invention and that examples provided herein are for illustration only and
are not
intended to be limiting in any way.
It can be appreciated from the above recitation that the range of
biologically active ingredients having a wido range of molecular weights can
be
employed in practicing this invention according to the Examples and teachings
herein
without limitation.
Gelation is desirably achieved by addition of gelling cations, typically
monovalent or divalent ions such as calcium, potassium or sodium. Such catioas
may
be present in sufficient quantity in the biologically active ingredient such
that no
external source is needed. If added to warm solution, the mixture is allowed
to cool
and set to form a gel. If it is required for the solution to be kept at room
temperature
(i.e, for temperature sensitive or volatile biologically active molecules),
the addition
of a slow diffusing (dissolving) catioa source is preferred.
EXAMPLES
Examples are provided by way of illustration and are not intended to
limit the invention in any way.
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Pxample for Gelled System
To 10 mL of dionized water brought to approximately 90 C was added
30 mg of GELRITEm gellan gum and stirred until fully hydrated to form a 0.3%
solution. Then the solution was cooled down to 55°C and 100 mg (to
obtain a dose of
ca. 10 mglmL) of Albumin dissolved in 1 mL water was added to the warm
solution
and stirred until properly dispersed. To this solution was added 0.5 mL of a
warm
concentrated solution of calcium chloride to reach 6 mM overall calcium
concentration. Using a preset 2 xnL pipet, warm aliquots were tranafarred into
round
I 0 shaped molds and left overnight to set upon cooling. Other formulations
(with
various gellan gum concentration and other actives were also prepared in a
similar
way and arc summarized in Table 1 following.
Active GELRITEm Active Dose Overall Calcium
1 Ingredient Initial (per mL of Concentration
S Gel)
Concentration
Albumin 0.3% 10 mglmL 6 mM
Albumin 0.5% 10 m mL 6 mM
Albumin 0.75% 10 mg/mL 6 mM
Albumin 1.0% 10 mghmI. 6 mM
20 Albumin 0.3% ZO mg/mL 6 mM
Albumin 0.5% 20 mg/mL 6 mM
Albumin 0.75% 20 m mL 6 mM
Albumin 1.0% 20 mg/mL 6 rnM
Myoglobin 0.5% 10 mglmL 6 mM
25 Myoglobia 0.75% 10 mglmL 6 mM
Insulin 0.5% 10 mg/mI, 6 mM
Bovine 0.3% 10 mglmL 6 mM
Sotnatotrn
in
Bovine 0.5% 10 mglmL 6 mM
30 Somatotropin
Bovine 0.75% 10 mglmL 6 mM
Somatotropin
Bovine 1.0'/0 10 mglmL 6 mM
Somatotropin
35 Ascorbic 0.5% 10 mg/mL 6 mM
Acid
Ascorbic 0.75% 10 mg/mL 6 mM
Acid
Sodium 0.5% 10 mg/mL 6 mM
Naproxen
Sodium 0.75% 10 mg/mL, 6 mM
40 N xen
Sodium 0.?5% 100 mglmL No calcium
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Naproxen added
Ibuprofen 0.75% 75 mg/mL No calcium
added
Ibuprofen 0.75% 100 mghnI, No calcium
.
added
Ibttpmfen 0.75% 125 mglmL No calcium
added
Ibuprofen 0.75% 150 mg/mL No calcium
added
Sodium 0.75% 150 mglmL No calcium
Salicylate added
Sodium 0.75% 180 mglmL No calcium
Salicylate added
Sodium 0.75% 210 mghnL No calcium
Salicylate added
Sodium 0.75% 250 mg/taL No calcium
Salicylatc added
1 S Release rates for the active ingredient were obtained using an
automated dissolution apparatus with the basket attachments (USP I) at 50 tpm
and
37°C with I liter of solvent. Release media were dionized water for the
proteins,
O.1M phosphate buffer for sodium naproxcn, simulated gastric fluid (SGF) for
vitamin
C and sodium salicylate, and simulated intestinal fluid {SIF) for Ibuprofen.
Samples
of the fluid were removed at timed intervals and compared to the appropriate
standard
solution on a UV spectrophotometer. Typical release curves are presented in
Figures 1 to 9 attached.
Figure 1: Release of various actives from 0.5% GELRII'E gels (6 mM Ca). In all
cases, active dose: 10 mg/mL. Average of 3 different gels for each curve.
Figure 2: Effect of GET.RTTl: (OR) conce~ation on the release of Na-Naproxen
(active dose: IO mg/mL) from gels (6 mM Ca): USP 50 RPM, 37°C in O.1M
phosphate bufFer. Average of 3 gels for each curve.
Figure 3: Effect of GELRITE (GR) concentration on the release ofMyoglabin
(active
dose: 10 mglmL) from gels (6 mM Ca). USP 50 RPM, 37°C in deiorused
water.
Average of 3 gels for each curve.
Figure 4: Effect of GELRITE (GR) concentration on the release of Albumin
(active
dose: 10 mgJmL) from gels {6 mM Ca). USP 50 RPM, 37°C in deionized
water.
Average of 3 gels for each curve.
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WO 99/22768 PCTNS98/Z3093
.$.
Figure 5: F.ff'ect of active dose on the release of Albumin from 0.5% (6 mM
Ca)
GELkIT'E gels. USP SO RPM, 37°C in deionized water. Average of 3 gels
for each
Figure 6: Effect of active dose on the release of Vitamin C from 0.5% (6 mM
Ca)
GELRI'TE gels. USP SO RPM, 37°C in simulated gastric fluid (pH 1.2).
Average of 3
gels for each cmvc.
Figure 7: Effect of active dose on the release of Ibuprofen from 0.75% (No
calcium
added) GELRITE gels. USP 50 Rl'M, 37°C in simulated intestinal fluid
(pH 6.8).
Average of 3 gels for each curve.
Figure 8: Effect of active dose on the release of sodium salicylate from 0.75%
(No
calcium added) GELRITE gels. USP 50 RPM, 37°C in simulated gastric
fluid (pH
1.2). Average of 3 gels for Each curve.
Figure 9: Effect of release medium I solubility on the release characteristics
of small
molecular weight active ingredients from 0.75%.(No calcium added) GELRITE
gels.
USP 50 RPM. 37°C in simulated gastric fluid (pH 1.2) for Vitamin C and
sodium
salicylate, is simulated intestinal fluid (pH 6.8) for sodium Naproxen, and in
phosphate buffer for Ibuprofen. Active dose is 150 mglmL in all cases except
for
~litamin C which is I00 mglmL. Average of 3 gels for oach curve.
As seen in Figure 1, there is a profound difference in release
characteristics between small molecules (i.e. Vitamin C and Naproxen) and
larger
proteins (i.e. myoglobia and albumin). For small molecules ts° (the
time needed to
release 50% of the drug fiom th.e gel) is less than 1.5 hours (ca. 30 minutes
for
vitamin C)~ For largo proteins tso is more than 5 hours. It also appears that
the larger
the protein the slower the release rate. Therefore such gels can be used to
release
biologically active molecules at different rates according to their molecular
weight.
For small molecules such as ascorbic acid and sodium naproxen, gum
concentration has little effect on the release characteristics. This is
depicted in
Figure 2. In this case, one can see that increasing gum concentration in the
gel from
0.5% to 0.75% (a 50% increase) has no significant effect on the release
curves.
However, for larger proteins, the gel network has a pronounced effect on the
release
characteristics. Hence an effective way of tuning release characteristics of
protcuns
and the Iike would be to chance sum concentration in the comaosition.
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In Figure 3, one can see that the same increase in gum concentration
(i.e, from 0.5% to 0.75%) has a profound effect on the release ofmyoglobin
from the
gets. Similarly, as shown in Figure 4, the release of albumin from the gels is
significantly affected when gum concentration is increased fiom 0.5% to 1.0%.
Therefore, for a given protein, the higher the gum concentration the smaller
the
release rate. Without being bound by theory it is believed that this can be
explained in
terms of gel effective pore size which decreases as gum concentration
increases and
can be used as a way of tailoring proteins release characteristics.
Those skilled in the art wilt recognize that blending gellan gum with
another gelling or non gelling po.tymcr would be another way of changing the
effective pare size in the gel and therefore would also affect rolease
characteristics.
Concentration can also be employed. Preferred polymeric additives to Gelrite
gels
would be, but arc not limited to, xanthaa gum and native gellan gum (high acyl
content).
The effect of active loading in gels is shown in Figures 5-8. For small
loadings, up to ca. 30 mglmL, release curves of both large (see Figure 5) and
small
(sec Figure 6).molecules are affected. The higher the active concentration the
faster
the release. On the other hand, for higher loadings, above ca.
Figura 6 shows that for Ibuprofen, almost identical release curves are
obtained when increasing loading from 75 mglmL to 150 mglmL (an increase of a
factor 2). Similarly for sodium salicylate, an increase from I50 mglmL to 250
mg/mL
has little effect on rcicase characteristics. This is depicted in Figure 8 and
such
praperry can be used to obtain oral dosage forms with release characteristics
independent of the dosage strangth, this can be attractive to design similar
systesns for
both children and adults.
Another important parameter to take into account is the solubility of
the drug in the release medium. Typical examples for small moiecuies are shown
in
Figure 9. When the active molecule is very soluble in the release medium, fast
release
may occur. This is the case for vitamin C in SGF and Ibuprofen in phosphate
buffer.
However when solubility of the active is reduced, such as Naproxea in SIF or
sodium
salicylate in SGF, a significant lowering in release rate is observed. The
most
significantly affected active ingredient is sodium salicylate, which probably
toms into
less soluble salicylic acid in the SOF low pH environment.
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Different drugs require di~ereat release profiles. For example, if it
may be desired for a pals killer or headache medicine to be released rather
quickly
while blood pressure regulators or anthihistaminics might require extended
release
profiles. It is an obj ect of the invention to show that release profiles from
gellan gum
gels is drug dependent and should be used in a case-by-case basis.
For a given drug, it might be of interest to obtain different release rates
from a similar formulation. It is an object of this invention to show that for
a specific
cases (proteins or large molecules) an increase of gellan gum concentration in
the gels
reduces release rates.
It might be desirable to obtain the same release characteristics from
formulation containing different level of actives. For example, an adult may
require
the delivery of 500mg of a given drug over a period of five hours while a
child would
i 5 require only 250mg over the same period of time. This is an object of this
invention
to show that in some cases (small soluble drugs with high loading) release
rates are
independent of drug loading.
However, in some cases, it might be of interest to have a loadiag-
dependent release rate from a given formulation. This is another abject of
this
invention to show that in specific cases, for example high molecular weight
proteins at
low loading, release rates are dependent of loading.
Examples of other freestanding gel compositions containing vitamins,
analgesics, antihistamines, decongestants, antitussives that were successfully
prepared
are summarized in Table 2 following.
TABLE 2
Active Name Active Dose Gelrite~ Comments
(mg/mL) Concentration
(%)
Na Napraxen 125 1.0 Clear gels,
no
calcium added
Na-Salicylate 100 0.5 Clear gels,
no
calcium added
Acetaminophen 100 0.75 White opaque
gels,
6mM Ca'~"~'
added
Pseudoephcdrine30 0.75 CleatGcls,6mM
Ca~"~' added
(weaker gels
without Ca't"~)
Phenyipmpanolataine12.5 0.75 Clear Gels,
6mM
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HCl Cai'~' added
(weaker
gels without
Cad
Chloropherinamine2 0.75 Clear Gels,
6mM
Ca'~"+ added
Bromopheniratnine2 0.75 Clear Gels,
6mM
Ca'~"t' added
Deactromethotphaa5 0.75 Clear Gels,
bml~
Ca'~'~' added
Diphenydramine I2.5 0.75 Clear Gels,
6mM
Ca'~'~ added
(weaker gels
without Ca~"~')
Thus, it is apparent that there has been provided, in accordance with
the instant invention, a process that fully satisfies the objects and
advantages set forth
herein above. While the invention has been described with respect to various
specific
examples and embodiments thereof, it is understood that the invention is not
limited
thereto and many alternatives, modifications and variations will be apparcrn
to those
skilled in the art in light of the foregoing description. Accordingly, it is
intended to
embrace all such alternatives, modifications and variation as fall within the
spirit and
1 S broad scope of the in~entioa.
