Note: Descriptions are shown in the official language in which they were submitted.
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BTOpQLYM15R8 Dl!5RIVE:D FROI~ ~IYDROIIYZA.Bl~E DIACID FAT8
~CENICA~ FIF~D
This invention relates to the area of organic
synthesis and, in particular, the synthesis of
biocompatible polymers.
0 R~PO~ND OF T~S INV~N~ON
Over the last 20 years, many classes of
biodegradable polymers have been under development for a
wide variety of biomedical applications.l The most
actively pursued biomaterials include: the
lactide/glycolide copolymers, polyorthoesters,
polycaprolactones, polyphosphazenes and
polyanhydrides.l~2~3 One of the widely studied
application~ of these polymers is their use in
implantable drug delivery systems. For this application,
polyanhydrides are a unique class of polymers because some
of them demonstrate a near zero order drug release and a
relatively rapid biodegradation in vivo.
Some of the desired physico-chemical and
mechanical properties in a single polymer that could be
used in an implantable or injectable drug delivery system
are:
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a. hydrophobic enough so that the drug is released
in a predictable and controlled way;
b. biocompatible when implanted in the target organ;
c. being completely eliminated from the implantation
site in a predictable time;
d. suitable physical properties for device
fabrication properties (low melting point,
usually below 100~C, and soluble in common
organic solvents);
e. flexible enough before and during degradation so
that it does not crumble or fragment during use;
and
f. easy to manufacture at a reasonable cost.
Some of these ideal properties are
displayed by some of the polyanhydrides. For example,
poly(carboxyphenoxy propane) ~PtCPP)] displays near zero
order erosion and release kinetics.~ However, this polymer
displays an extremely slow degradation rate, and it is
estimated that a drug delivery device prepared from
P(CPP) would take almost three years to completely degrade
in vivo.
In U.S. Patent 5,171,812, a class of aliphatic
copolyanhydrides was synthesized from dimers and trimers of
unsaturated fatty acids (FAD and FAT, respectively) with
sebacic acid. This class of polymers were demonstrated to
have the properties suitable for developing various types
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of implantable drug delivery devices, including:
microspheres, films, rods, and beads.
In a recent publication,5 a class of aliphatic
copolyanhydrides was synthesized from nonlinear hydrophobic
S dimers (FAD) of erucic acid and sebacic acid (SA). This
class had some biocompatible characteristics even though
there was a rapid partial degradation within the first ten
days with the release of the SA component, a residue which
i8 mostly the FAD comonomer remains and is not easily
degraded.
Although these polymers were found suitable for
drug delivery applications both in vivo and in vitro,
studies in dogs showed that when implanted in muscle, the
polymer degraded to the synthetic fatty acid dimer which
was not eliminated from the implantation site even after
six month~. This semisynthQtic fatty acid dimer is not
easily metab~lized in the body because it contains a non-
natural structure of a C-C bridge (Structure 1) which is
difficult to be metabolized by body enzymes.
8tructur~ atty ac~d D~ -r
HOOC ----
~ ~,~ ~ , ,COOH
2s
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The FAD and related oligomers of fatty acids are
the coupling products of two or more unsaturated fatty
acids in which the original fatty acids are connected via
a chemically stable C-C bond (non-hydrolyzable). Because
the oligomerized fatty acids contain a non-natural
structure (C-C branching points), they may not be
eliminated at the same rate and capacity as natural fatty
acids, which are readily eliminated from the body by
a ~-oxidation process.
8~NMARY OF T~ lNV~10~ aND ADVANTAG~8
According to the present invention, a monomeric
diacid derivative comprising at least two fatty acids
coupled by a hydrolytically or enzymatically degradable
bond is formed. In a biological environment, the bond
degrades forming naturally occurring fatty acid products
thereby allowing elimination.
In general, the monomeric diacid derivative has
the structure
H
Rl--C--R--COOH
'2-COOH
wherein R, R1 and R2 are aliphatic organic residues with 0
to 20 carbon atoms and can be the same or different, S is
an enzymatically or hydrolytically degradable bond selected
from the group consisting of ester, amide, urethane,
acetal, urea, and carbonate bonds can be formed.
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- The absence of stable C-C nonhydroyzable
branching bonds allows these monomers to be first
hydrolyzed to the respective natural acids and then rapidly
eliminated since naturally occurring fatty acids are formed
and are readily eliminated from the body via ~-oxidation.
BRIEF D28CRIPTION OF TB DRA~ING8
Other advantages of the present invention will be
readily appreciated as the same becomes better understood
lo by reference to the following detailed description when
considered in connection with the accompanying drawings
wherein:
FIGURE 1 is a graph showing hydrolytic
degradation of polymers based on ricinoleic acid as
determined by weight loss and conversion of anhydride to
acid groups, degradation being determined in 0.1M phosphate
buffer pH 7.4 at 37~C;
FIGURE 2 is a graph showing in vitro release of
ciprofloxacin from ricinoleic acid maleate-based polymeric
devices, drug release being determined in 0.lM phosphate
buffer pH 7.4 at 37~C; and
FIGURE 3 is a graph showing in vitro release of
ciprofloxacin from ricinoleic acid maleate-sebacic acid
copolymer based polymeric devices, drug release being
determined in 0.lM phosphate buffer pH 7.4 at 37~C.
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DETAI~ED DE8CRlPTION OF TB PR~F~RRED EMBODIMENT
The present invention relates to biodegradable
polymers containing novel hydrolyzable diacid fats which
provide hydrophobicity and improved physical and mechanical
properties to the polymers as compared to biopolymers that
do not contain these monomeric units, and yet are
completely degradable to natural products when exposed to
biological environments.
In searching for an alternative hydrophobic
monomer that possesses similar properties to the FAD but is
more readily eliminated from the body, i.e. does not
contain a stable C-C coupling bond, applicants have
synthesized a new class of fatty-acid-based-diacid monomers
with similar properties to the FAD monomer but that
hydrolyze to the natural fatty acid.
The diacids were synthesized from fatty acids
containing a hydroxyl or amine side group and aliphatic
diacid derivatives. The general structure of these
monomers is:
H
Rl--C--R--COOH
R2--COOH
wherein R, Rl and R2 are aliphatic organic residues with 0
to 20 carbon atoms and can be the same or different, S is
an enzymatically or hydrolytically degradable bond selected
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- from the group consisting of ester, amide, urethane,
acetal, urea, or carbonate bonds can be formed. Examples
of other useful monomers are diacid derivatives of tartaric
acid and glycerylmonostearate.
These monomers are synthesized, for example,
from natural hydroxy fatty acids which are reacted with
dicarboxylic acid derivatives, such as cyclic anhydrides,
to provide diacid monomers suitable for anhydride and ester
polymerization. The reaction is conducted in an organic
solvent where the hydroxy acid is reacted under reflux with
the cyclic anhydride. When other reactive acids are used,
the reaction conditions should be adjusted. The natural
molecules are therefore linked by an hydrolyzable bond
which include: ester, amide, imide, orthoester, carbonate,
urethane, urea or phosphate ester. These diacid fats can
be polymerized or copolymerized into a polyanhydride or
polyester and form polymers that are, in general, of a low
melting point (below 100~C), soluble in common organic
solvents, and pliable materials.
This invention is demonstrated by the synthesis
and characterization of polymers based on ricinoleic acid.
Natural hydroxy fatty acids, such as 12-hydroxy stearic
acid and ricinoleic acid were reacted with cyclic
anhydrides such as succinic or maleic anhydride, to provide
diacid monomers suitable for anhydride and ester
polymerization. These monomers are expected to degrade in
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WO 96122270 PCTIIB95~00007
vivo into their fatty acid and succinic acid counterparts
since they are bound by a hydrolyzable ester bond.
The structures of the diacids are:
1. Ricinoleic ~cid m~le~te (RAhI)
CH
o ,.
c=o
o
II. 1'-Hydroxysteanc acid succinate (~SAS)
'~ r~~ ~
III. 12-Hydroxystearic acid maleate (HSAM)
a~
Diacids were synthesized based on Ricinoleic
acid, 12-hydroxy oleic acid. The hydroxyl group was
reacted with maleic anhydride to form ricinoleic acid
maleate (I). Hydrogenolysis of this diacid forms the
saturated derivative, 12-hydroxy stearic acid succinate
(II). A third diacid monomer was synthesized from the
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reaction between 12-hydroxy stearic acid and maleic
anhydride (III). These diacid monomers were incorporated
into a polyanhydride or polyester and used as carriers for
drugs.
The diacid fats used a~ examples in this
application have the following general structures:
8tructur- 2. Naturally occurring f~tty ac~
co~t~ining ~i~ci~ uonom-r~
A. monogfycsridQ dica~boxyfic acid
CH2-O-CO-(CH2)X-CH3
ICH2--~Z (CH2)jCOOH
HOOC(CH2)yZ~cH2
B. Ta~taric ac~d diafkyl derivative
COOH
CH O-Z- (C~)x~C~3
CHb-(CH~x-Z~o CH
COOH
C. Oicarbox~ic acid fat
CH3 (CH2~v ICH (C~)W--COOH
M
(CH2)~,- COOH
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--10--
where: x-5-25; y=1-12; v+w=25; Z=CO,C0-O,CO-NH; and M=O-
CO, O-CO-O, O-CO-NH, O-P02-0, NH-CO.
These monomers are diacid derivatives of
monoglycerides, tartaric acid and fatty acids having an
additional functional group with one or more natural
molecules linked by an hydrolyzable bond which include:
ester, amide, imide, orthoester, carbonate, urethane, urea
or phosphate ester. These diacid fats can be polymerized
or copolymerized into a polyanhydride or polyester and form
polymers that are, in general, of a low melting point
(below 100~C), soluble in common organic solvents, and
pliable materials that are useful in making biodegradable
medical devices. For example, microspheres loaded with
drugs can be prepared for the delivery of drugs in vivo and
in vitro. Because these monomers hydrolyze in a biological
environment to their o~iginal natural and safe
counterparts, they are biocompatible and their elimination
time after polymer degradation is within three months.
These monomers are polymerized into
polyanhydrides and into polyesters as described in the
examples.
Additionally, these diacid fats can be used as
plasticizing components in plastics such as nylon,
polyurethane as substitute for oligomerized fatty acids
with the advantage of simple structure and ease of
preparation.
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The present invention allows the preparation
of a drug release system which will deliver a
pharmacologically effective amount of a drug. The drug is
held or entrapped in a polymer matrix. The matrix
essentially consists of repeating units of a monomeric
diacid derivative comprising at least two fatty acids
coupled by a hydrolytically or enzymatically degradable
bond whereby said degradable bond in a biological
environment degrades forming naturally occurring fatty acid
lo products. As the bonds degrade the drug is released. The
bonds can be ester, amide, urethane, urea and carbonate
bonds.
The drugs in solid form are melted or dispersed
in the polymer to form a matrix, small molecules, as well
as large molecules, such as peptides, proteins, and
antibodies, can be delivered from the polymer matrix. The
duration of drug release is mostly affected by the
hydrophobicity of the drug, drug loading, and polymer
composition.
Further, the present invention can be used as a
biocompatible, biodegradable, implantable material
essentially consisting of repeating units of a monomeric
diacid derivative comprising at least two fatty acids
coupled by a hydrolytically or enzymatically degradable
bond whereby said degradable bond in a biological
environment degrades forming naturally occurring fatty acid
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products. The bonds can be ester, amide, urethane, urea
and carbonate bonds. The implantable material can be used
to form dressings, sutures and the like that need to be
implanted but not remain in the body. For example, they
can be used as films for surgical adhesion prevention by
placing the polymer film at the abraded area during
surgery.
In general, the method for synthesizing the
biodegradable polymer containing hydrolyzable diacid fats
requires the preparation of at least one highly pure
prepolymer of monomeric diacid derivative comprising at
least two fatty acids coupled by a hydrolytically or
enzymatically degradable bond. The prepolymer is then
polymerized at a temperature and reaction time to form a
polyanhydride or polyester of an appropriate molecular
weight. The polymerization is stopped when a molecular
weight between 10,000 and 100,000 is obtained for the
needed application or device.
A copolymer is formed from at least two highly
pure prepolymers polymerized together as described above.
U.S. Patent 4,757,128 to Domb et al., issued July 1988,
discloses examples of classes of monomers that can be
copolymerized with the monomers of the present invention to
form copolyanhydrides. Typical and useful co-monomers are
the aliphatic diacid such as adipic, subernic, dodedecane
dicarboxylic acid. Other co-monomers can be iso-phthalic
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- acid, terephthalic acid, carboxphenoxypropane. The
copolymer of RAM with subernic acid gave a Mw of 32,000,
the copolymer with iso-phthalic acid gave a Mw of 24,000.
The ricinoleic acid maleate of the present
invention are useful as plasticizer for plastic modeling.
The following is the preferred method of preparing the
formulation.
Ricinoleic acid maleate containinq ~lasticizer
Low volatile polyester mixtures based on
Ricinoleic acid maleate are useful as plasticizer for
plastic modeling:
A mixture of adipic acid (58 grams), ricinoleic
acid maleate (7 grams), propylene glycol (38 grams), and n-
hexanol (13 grams) was heated at 140~C for five hours while
water was distilled. To the reaction mixture, 0.05% of
stannous octoate was added as catalyst and the reaction
temperature was increased to 180~C and a vacuum of 0.1 mm
Hg waa applied for an additional three hours. The
resulting viscous polymer had a molecular weight of 700 as
determined by gel permeation chromatography. The resulting
oligomer was mixed 30 weight percent with polyvinylchloride
(PVC) to form a flexible sheet which had a loss of 0.5
weight percent in the volatility test at 105~C for three
days compared to 1.2 to 2.5% with the phthalate
plasticizer. Other plasticizers were prepared similarly
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w~s6l22270 PCTnB9S/00007
using hydroxy stearic acid succinate or hydroxy stearic
acid maleate instead of ricinoleic acid maleate.
Preparation of hydrophilic plasticizer:
Ricinoleic acid maleate was reacted with two equivalents of
poly(ethylene glycol) MW~ 2,000 in toluene with 1% H3PO4
(85% concentration) as catalyst. ~he reaction was
continued for five hours at 110~C. Toluene was eva~orated
to dryness to form an oily material. The material was
mixed in PVC to form a flexible sheet which had a loss of
.6% at 105~C for three days volatility test.
The following examples illustrate the preparation
of and use of the monomers and polymers of the present
invention:
Materials and Methods
The following compounds were used: ricinoleic
acid (Kodak 91% pure), maleic anhydride (BDH, 99.5%),
Sebacic acid (Aldrich 99%), acetic anhydride, toluene
(dried by azeotropic distillation before use), EtOH (abs.),
CH2C12, and CHC13 (all Frutarom analytical grade).
IR spectroscopy was performed on an Analect
Instruments FTIR spectrometer model fx-6160 using a Data
system MAP-67. Monomer, prepolymer, and polymer samples
were film cast onto NaCl plates or dissolved in chloroform
and placed in a NaCl cell.
Ultraviolet spectroscopy was performed on a
Kontron~ Instruments Uvikon spectrophotometer model 930.
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--15--
- Melting points were determined on an
Electrothermal melting point apparatus. Melt transition
temperatures and degree of crystallinity were determined by
a Perkin Elmer DSC 7 differential scAnning calorimeter,
calibrated with zinc and indium standards. The heating
rate was 20~C/min for all the polymers, under nitrogen
atmosphere.
Molecular weights of the polymers and prepolymers
were estimated on a GPC system composed of a Spectra
10Physics P1000 pump, Applied Biosystems 759A Absorbance UV
detector at 254 nm, Spectra Physics Data Jet injector, and
a WINner/286 data analysis computer system. Samples were
eluted in dichloromethane through a linear Styroget, 104 A
pore size, at a flow rate of 1 ml/min and monitored at 254
lS nm. Molecular weight of polymers were determined relative
to polystyrene st~n~Ards (Polysciences, PA), with a
molecular weight range of 400 to l,S00,000 using Maxima 840
computer program (Waters, MA).
lH-NMR spectra were obtained on a Varian 300 MHz
spectrometer at 23~C using deuterated chloroformtTMS
solvent. Chemical shifts were expressed in ppm downfield
from Me4Si as an internal stAn~Ard. The values are given
in d scale.
Tensile strength measurements were attained using
an Instron Tensile Tester Model 1114 at room temperature.
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--16--
Catalytic hydrogenation was performed using 3% Pd
on activated carbon (Aldrich) using a Parr apparatus.
Evaporation's were carried out on a Buchi RE 111 Rotavapor.
~m~les
1. ~onomer and Polymor Rynthesi~
Ricinoleic acid maleate (RAM). A solution of
ricinoleic acid (144 g, 0.48 mol) and maleic anhydride (61
g, 0.61 mol) in toluene (350 ml) was stirred at 80-sooc
overnight. The excess of maleic anhydride which
precipitated was removed by filtration. The solution was
washed four times with distilled water, dried over MgSO4 and
evaporated to dryness to give 140.92 g (73%) of product as
a dark orange oil. Titration (using THF as solvent and
phenolphthalein as indicator) with 0.1 N NaOH showed 88%
diacid product; IR 1740, 1715 cm~l; lH-NMR 6.33 (dd, 2H,
HOOC-C~=C~-COO-), S.45 (m, lH, C-C~=CH-C), 5.28 (m, lH,
C-CH=C~-C), 5.00 (quintet, lH, methine), 2.33 (m, 2H, C~2-
COOH), 2.00 (dd, 2H, OCO-C-C~2-CH=CH), 1.60 (m, 4H, C~2-CH2-
COOH and COO-CH-C~2-CH2), 1.25 (broad d, 18H, aliphatic
methylenes), 0.83 (t, 3H, -CH3)
t 2-hydroxysteric acid succinate (HSAS). A
solution of RAM (50 g. 0.13 mol) in abs. EtOH (- 100 ml)
was hydrogenated over 3 g Pd/C at 85 atm overnight. The
catalyst was filtered off, and the solution was evaporated
to dryness yielding 46.83 g (94%) of an oily orange liquid,
which upon cooling to room temperature solidified to an
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--17--
off- white solid which was dissolved in hot EtOH and left
to recrystallize in the freezer for two weeks. The product
was filtered and dried to give 37.0 g (74%), mp 50-52~C; IR
1740, 1715 cm~l; lH-NMR 4.88 (quintet, lH, methine), 2.77
(t, 2H, HOCO-C~2-CH2-COO-CH), 2.63 (t, 2H, HOCO-CH2-Ca2-COO-
CH), 2.42 (t, 2H, C~2-COOH), 1.62 (m, 4H, C~2-CH-OCO-CH2),
1.52 (m, 2H, C~2-CH2-COOCO), 1.23 (m, 22H, aliphatic
methylenes), 0.85 (t, 3~, C~2-CH3)
12-hydroxystearic acid maleate rHSA~). A
solution of ricinoleic acid (50 g, 0.17 mol) in abs. EtOH
(-100 ml) was hydrogenated over 3 g Pd/C at 80 atm
overnight. The solidified product was dissolved in CH2Cl2,
and the catalyst was removed by filtration. The solution
was evaporated yielding 50 g (100%) of product.
Recrystallization from EtOH gave 35.0 g (70%). The FTIR
and NMR spectra were similar to those described in the
Aldrich 93 catalogs, mp 73-75~C (lit: Aldrich 93 catalog
80-81~C). A solution of 12-hydroxystearic acid (34.45 g,
0.11 mol) and maleic anhydride (14.5 g, 0.148 mol) in
toluene (240 ml) was stirred at 88~C overnight. The
solution was washed four times with distilled water, dried
over MgSO4 and evaporated to dryness to yield 40.0 g
(88%). Titration (using THF as solvent and
phenolphthalein as indicator) with 0.1 N NaOH showed 96%
diacid product; IR 1740, 1715 cm 1; lH-NMR 6.38 (d, 2H,
COCH=C~CO), 5.02 (t, lH, C~OCO), 2.36 (t, 2H, C~2COOH), 1.61
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--18--
(m, 6H, ~2CCOCHO and C~2CH2COOH), 1.27 (m, 22H, (CH2)ll),
0.88 (t,3H,C~3)-
Preparation of prepolymers. The prepolymers of
sebacic acid (SA) were prepared as previously described. 6
Briefly, sebacic acid prepolymer was prepared from the
purified diacid monomer by refluxing it in excess acetic
anhydride for 30 minutes and evaporating it to dryness.
The hot clear viscous residue was dissolved in
dichloromethane and the prepolymer was precipitated in a
lo mixture of hexane/isopropyl ether (1:1). The solid was
collected by filtration and dried by vacuum at room
temperature.
Prepolymers of the fatty acid ester based
monomers were prepared as follows: Solutions of each
monomer dissolved in acetic anhydride (120~C, 1:5 w/v) were
stirred under reflux for 20 min.
The RAM prepolymer solution was evaporated to
drynes~ to give an orange oil product. Mw-3800 Mn-3520; IR
2900, 2850, 1810, 1720 cm~l; lH-NMR 6.30 (dd, 2H, CO-CH=CH-
CO), 5.42 (d, lH, CH=CH), 5.38 (d, lH, CH=C~), 4.98
(quintet, lH, methine), 2.45 (t, 2H when prepolymer is
head-to-tail, CH2-COO-), 2.40 (t, 2H when prepolymer is
head-to-head, CH2-COO-), 2.32 (s, 3H, C~3-COOCO-CH=CH), 2.21
(s, 3H, CH3-COOCO-CH2-CH2), 2.00 (dd, 2H, C-C~2-CH=CH), 2.30
(m, 2H, CH=CH-CH2-CH2-) 1.60 (m, 4H, C~2- CH2-COOCO- and
CH=CH-COO-CH-CX2-CH2), 1.30 (broad d, 16H, aliphatic
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WO 96/22270 PCTIIB95100007
methylenes), 0.87 (t, 3H, CH2-C~3). The HSAS prepolymer
gave a semisolid off-white product. Mw-1788 Mn-1382; IR
2900, 2850 1820, 1730 cm~l; lH-NMR 4.88 (quintet, lH,
methine), 2.77 (t, 2H, COOCO-C~2-CH2-COO-CH), 2.65 (t, 2H,
COOCO-CH2-C~2-COO-CH), 2.44 (t, 2H, C~2-COOCO), 1.65 (m, 4H,
CR2-CH-OCO-CH2), 1.55 (quintet, 2H, CR2- CH2-C0OCO) 1.25 (m,
22H, aliphatic methylenes), 0.85 (t, 3H, CH2-CH3).
The HSAM prepolymer gave a viscous oil. Mw-1788
Mn-1382; IR 2900, 2850, 1820, 1730 cm~l, lH- NMR 6.26 (dd,
2H, CO-CH=CH-CO), ~.92 (quintet, lH, methine), 2.47 (t, 2H
when prepolymer is head-to-tail, CH2-COO-), 2.40 (t, 2H when
prepolymer is head-to-head, CH2-C0O-), 2.25 (s, 3H, C~3-
COOCO-CH=CH), 2.17 (s, 3H, C~3-COOCO-CH2-CH2), 1.52 (m, 4H,
CX2-CH2-COOCO- and CH=CH-COO-CH-C~2-CH2), 1.21 (broad, d,
22H, aliphatic methylenes), 0.83 (t, 3H, C~2-CH3).
Pre~aration of polymers. The prepolymers
underwent melt polycondensation. Typically, RAM prepolymer
(10 g, 33 mmol) was placed in a KIMAX~ glass tube with a
side arm or a round bottomed flask and polymerized at 180~C
under reduced pressure (0.1-0.5 mm Hg). The polymerization
was complete after 90 minutes. The by-products, acetic
anhydride and acetic acid, were trapped in a liquid N2 trap.
The homopolymers were viscous yellow oils.
- Copolymers were prepared similarly by
polymerizing a mixture of prepolymers at 180~C under
reduced pres~ure. In a typical experiment, RAM prepolymer
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--20--
(5 g, 17 mmol) was mixed with sebacic acid prepolymer (SA-
diAc) (5 g, 21 mmol) and polymerized at 180~C under reduced
pressure for 60-90 minutes depending on the amount being
polymerized. The crude polymers were dissolved in CH2C12
(1.5 w/v) and filtered into stirring di-isopropyl ether
(100-200 ml). The precipitate was separated by filtration,
washed with di-isopropyl ether, and dried in the Rotavapor.
Molecular weights and thermal characterization
of the polymers are shown in Table 1. The IR and lH-NMR
of homopolymers of RAM,HSAM,HSAS, and 1:1 copolymers with
SA (d ppm) are listed in Table 2.
Mechanical ProDerties. These series of polymers
had similar mechanical properties to the FAD class of
polymers. They formed very flexible films with similar
strength as seen in Table 3.
2. ~ynth~ of poly--t-rs conta~n~ng fatty
diac$d monom-rs. Biodegradable polyesters were
synthesized from the reaction between lactide, ricinoleic
acid maleate, and propylene glycol in the molar ratio 8:1:1
and 1% stannous octoate as polymerization catalyst. The
mixture of the monomers were polymerized at 100~C under
nitrogen with constant stirring. After 24 hours, the
temperature was raised to 140~C, the reaction was continued
for another 24 hours and then a vacuum of 0.1 mm Hg was
applied and the reaction was continued for another 8 hours.
The viscous melt was solidified into a pliable tan mass.
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--21--
Polymers containing HSAM and HSAS monomers at various
ratios were prepared similarly. The data analysis of these
polymers is summarized in Table 4. All polymers were
soluble in dichloromethane, chloroform, and
tetrahydrofuran. IR spectra of the polymers showed esters
peaks at 1720 nm.
3. 8ynthesis of d~st-aryl tartaric acid. Into
a flask were placed 100 ml dichlomethane, tartaric acid
(0.1 mole), triethylamine (0.4 mole), and stearoyl chloride
(0.2 mole). The reaction was left for 24 hours with
constant stirring. The reaction mixture was washed with
o.lN HCl solution to yield distearyl tartaric
acid.
4. In vivo biocompatibility and elimination
studi-J. The biocompatibility and the elimination time of
these new polymers as compared to poly(FAD-SA)50:50 and
poly(sebacic acid) {PSA} was studied in rats as follows:
Clean specimens (30 mg, 2x2x4 mm in size) of the
following polymers:
1. poly(RAM-SA)30:70,
2. poly (HSAM - SA) 50: 50,
3. poly(HSAS-SA)50:50,
4. poly(FAD-SA)50:50,
5. Vicril (Ethicon),
6. poly(FAD-SA)50:50, and
7. poly(sebacic acid) {PSA}
CA 02210800 1997-07-17
WO 96S22270 PCT/lb551~0007
were implanted subcutaneously in four dorsal sites of male
Sprague-Dawley rats (250-300 g). Six rats were used in the
study and each rat was implanted randomly with four
different specimens. All animal work was done under
sterile conditions. The polymer specimens were dipped in
70% alcohol prior to insertion. The animals were
sacrificed after 12 and 30 days post implantation, and the
implantation sites were examined macroscopically and
histologically. The polymer remnants were retrieved and
analyzed.
Macroscopically, no swelling or pathological
signs were observed in any of the groups during the
experiment and at sacrifice. The animals appeared healthy
and did not show any weight loss. The implantation sites
were clean and normal without any swelling and the remnants
of the implanted polymers were easily retrieved. At the
implant site of the new polymers, a small amount of polymer
remnants (30-40% of the original mass) in the form of a
soft mass was seen. The animals implanted with poly(FAD-
SA)50:50 had solid remnants in the site of about 70~ of the
original implant size. About 20% of the PSA remained at
the implant site after 12 days, and the Vicril polymer
remained intact. Histopathology examination of tissue
specimens from the area confined to the tissue in direct
2S contact with the polymer device showed mild inflammation
which was rated 2 in a scale from 1 to 5 where: 1 -
CA 02210800 1997-07-17
PCT111~3100007
WO 96122270
--23-
resembles no irritation; 2 - slight inflammation; 3 -
moderate; 4 - marked; and 5 - severe inflammation. No
encapsulation was found with any of the samples.
A second group of rats which were implanted with
the polymers under similar conditions were completely
eliminated from the site after 12 weeks. In comparison,
Vicril polymers remained almost intact, poly(FAD-sA)so:5o
was only 60% eliminated.
This experiment indicates that the new fatty acid
based polymers are biocompatible. The elimination time in
vivo of these polymers is shorter than for the FAD-based
polymers.
The rat model has been considered highly
predictable of human response for toxicant elimination7 and
biocompatibility. 8
5. In vitro hydrolysis. The hydrolysis of the
l:1 copolymers with SA was studied by:
(a) weight loss of the sample;
(b) monitorinq the change of molecular weight by
gel permeation chromatograph (GPC);
(c) monitoring the disappearance of the anhydride
linkage and the formation of carboxylic acid by FTIR
spectroscopy; and
(d) the release of sebacic acid from the polymer
by HPLC analysis.
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WO 96122270
--24--
The hydrolysis studies were conducted in 0.1 M
phosphate buffer pH 7.4 at 37~C using rectangular samples
3x5x8 mm in size and weighing about 100-150 mg. The
samples were taken out from the buffer at different time
intervals and were weighed after being dried thoroughly in
the oven. The percent weight loss of the sample and the
transformation of the anhydride bond to acid as a function
of time are shown in Figure 1. The change in molecular
weight was monitored by GPC showing a drastic drop in
molecular weight in the first 24 hours and then stabilized
at about 6,000-7,000 from then on. The samples were
observed visually for the changes in the external
appearance. At any stage of the experiment, the samples
did not crumble nor were there any cracks visible.
6. In vi~o ~n~ymat~c degradat~on. The
enzymatic degradation of these new monomers were compared
to those of the oligomerized fatty acids. The monomers
RAM, HSAM, HSAS, FAD, and FAT (200 mg) were mixed in a
solution containing esterase (2 ml, containing 50 units of
esterase from porcine liver, Sigma Chemical Company, St.
Louis, Missouri) and were incubated for 24 hours at 37~C.
The monomers or their degradation products were extracted
with chloroform and analyzed by lH NMR. The lH NMR spectra
of the FAD and FAT monomers were identical before and after
treatment. The RAM, and HSAS monomers contained about 10%
ricinoleic acid or 12-hydroxy stearic acid, respectively.
CA 02210800 1997-07-17
WO 96/22270 PCT/~5S,'0~û~7
This study demonstrates the biodegradability of the new
monomers compared to the oligomerized fatty acid monomers.
7. In vitro drug r-leas-. Ciprofloxacin (5% by
weight) was incorporated in rectangular tablets (3x5x8 mm
in size and 200 mg weight) of poly(RAM-SA)l:l,
P(HSAM:SA)l:l, P(HSAS:SA)l:l, P(FAD:SA)1:1 and poly(suberic
anhydride) by the melt method. In vitro drug release was
determined in phosphate buffer pH 7.4 at 37~C.
Ciprofloxacin concentration was determined by W detection
at 272 nm. The results are shown in Figure 2. The drug
release followed a first order kinetics (r2=0.89-0.99) with
a fast release during the first lO days and a slow release
thereafter.
In a second experiment, Ciprofloxacin (5% weight)
was incorporated in rectangular tablets (3x5x8 mm in size
and 20 mg weight) of poly(RAM-SA) of various compositions
by the melt method. In vitro drug release was determined
in phosphate buffer pH 7.4 at 37~C. Ciprofloxacin
concentration was determined by W detection at 272 nm.
The results are shown in Figure 3. The drug release
followed a first order kinetics (r2=0.96) with a fast
release during the first 10 days and a slow release
thereafter. The drug release rate was increased with the
increase in the sebacic acid content in the polymer;
however, a small difference in the release profile was
found for the polymers composed of 40 to 80% sebacic acid
CA 02210800 1997-07-17
WC)96122270 PCT/lb9S~ ~7
--26--
(SA). Similar results were reported for the FAD-SA
copolymers.
The preparation of dimer oleic acid or dimer
erucic acid (FAD) contains two steps. In the first step,
oleic acid or erucic acid undergo a coupling reaction using
clay as a catalyst. In the second step, the product is
hydrogenated to saturate the double bonds in the product.
During the first step, many by-products are formed,
including trimers and tetramers, that are difficult to
remove. Also, the FAD product contains cyclic and aromatic
by-products which counts to about 30% of the Priipol 1004
and lOo9 products which are the most available pure FAD
products (based on producer, Unicema, information). The
product of the present invention contains only one
component, the linear diacid monomer which is synthesized
in a single esterification step (condensation reaction in
general) which cannot form other oligomers or cyclic
materials, but the linear diacid as described herein.
The invention has been described in an
illustrative manner, and it is to be understood that the
terminology which has been used is intended to be in the
nature of words of description rather than of limitation.
Obviously, many modifications and variations of
the present invention are possible in light of the above
teachings. It is, therefore, to be understood that within
the scope of the appended claims the invention may be
practiced otherwise than as specifically described.
CA 02210800 1997-07-17
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W~ 96122270
--27--
T~ Mol-cul~r ~-~g~t~ ~nd th~ l ch~ract-r~ation
o~ f~tty aci~ ~-t-r pol~-r~
Polym~r of Molecular weiBhtMel~ing pointb TmC ~d
Mw Mn (~C) Tm~(~C~ (J/gm)
RAM 27,800 11,400 viscous oil ~ ---
HSAM ~9,500 9,400 sernic~li~
HSAS 15,~00 8,700 sem~ d --- _
RAM:SA 10:9010,5007,200 72-76 86.18 98.59
2AM:SA '0:808,500 6,200 68-74 81.33 108.99
RAM:SA 30:7014,00010,800 68-70 79.33 103.02
R~M:SA 40:606,100 5,000 6S-70 76.63 65.~ 1
RAM:SA 50:50135,~001~,900 56-62
HSAM:SA 50:50 32,000 11,600 65-68 67.31 50.59
HSAS:SA 50:50 28,700 13,000 68-70 70.39 78.45
PSA 465,800 23,400 83 88.64 131.88
a Polymers s~ l,P i; r~ by melt con~ncq*~n
b. ~elting poin~s d~,...no~ on an '~le.,llull.~---al melting yoin~ dy~d~u~
c. Melting ~qn ci n(~n ~ n ~ e dLh. --~ned by DSC.
d ~c ûf crystqllinity is obs~in~d from the ~H dLt,c...~ncd by DSC, Iqrger ~H values
insinuate high~ degree of ~ystqllinity~
CA 02210800 1997-07-17
WO 961 2270 PCT~IB9~/00007
--28--
T~ 2. Oth-r c~r~ct-ri~tic~ of poly~-r~
rR. All polyme~s had typical IR p~aks at ~900, . 850. 1805, and 1740 cm-l.
1 H-N~IR of homopolymers of RAM,HSAM,HSAS, and 1: 1 copolymers wirh SA (d ppm):
PR~M: 6.~7 (dd, 2H, CO-CH=CH-CO), 5.43 (m, lH, CH=CH3, 5.31 (m, IH,CE~=CH),
4.96 (m, lH, methine), 2.47 (t, 2H when prepolymer is he~d-to-t3il, CH2-COO-), '.1~ (t, 'H
when prepolymcr is head-~o-head, CH2-COO-). 2.30 (m, 2H, CH=CH-CH2-CH2-), 2.00
(dd7 2H,CH-CH2-CH=CH), 1.60 (m, 4H, C~l2-cH2-cQQco- ~nd CH=CH-CQQ-CH-
CH2-CH2), 1.29 (brd, 16H, aliphatic methylenes), 0.88 (t, 3H, CH2-CH3).
PHSAS: 4.88 (quintet, lH, methine3, 2.76 (t, 2H, COOC~CH2-CH2-COO-CH~, 2.64 (t,
2H, COOCO-CH2-CH2-COO-CH), 2.43 (t, 2H, CH2-cooco)~ 1.65 (m, 4H, CH2-CH-
QCQ-CH2), 1.51 (brrm, 2H, CH2-CH2-COOCO), 1.25 (m, 2 'H, aliphatic me2h~!enes), 0.88
(t, 3H, CH2-CH3).
rHSAM: 6.30 (dd, 2H, CO-CH=CH-CO), 4.98 (quintct, IH, methine), '.52 (t, 'H ~vhen
prepolymer is head-to-tail, CH2-COO-), 2.42 (t, 2H when prepolymer is head-to-head. CHq-
COO-), 1.58 (m, 4H, CH2-CH2-COOCa and CH=CH-COaCH-C~12-CH~), 1.24 (brd,
~2H, ~lirh~*c methylenes), 0.83 (t, 3H, CH2-CH3).
P(RAM-SA)l:l: 6.~7 (s, 2H, CO-CH=CH-CO), 5.4S (brm,lH,COOCO-CH~-COO-
CH), 5.33 (brm, lH, COOCO-CH=CH-COO-CH), 4.98 (brm, IH, methine), 2.53 ~t, 2H
whcn RAM pr~polymer is head-to-tail, CH2-COO ), 2.44 (t, 2H when RAM prepolymer is
head-to-head, CH2-COO-), 2.35 (m, 2H, -o-cH-cH2-cH=cH-cH2-)~ 2.09 (dd, 2H.-O-CH-CH2-CH=CH-), 1.65 (m, 4H, C~I2-CH2-COOCO-andCH=CH-COaCH-CH2-CHL), 1.'~
and 1.25 (two brs, ~lirh~ti~ methylenes f~m RAM and from SA), 0.87 (t, 3H, CH2-CH3).
P(HSAS-SA)1:1: 4.88 (quintet, lH, methine), 2.77 (t, 2H, COOCO-CH2-CH2-COO-
CH), 2.66 ~t, 2H, COOCO-CH2-CH2-COO-CH), 2.44 (t, 6H, CH2-COOCO), 1.65 ~m, 6H,
CH2-CH-OCO CH2), 1.51 (brm, 4H, CH2-CH2-COOCO), 1.32 (m, 12H, CEI2-CH2-
CH2-CH2-COO), 1.25 (m, ~lirh~*~ methylenes), 0.88 (t, 3H, CH2-CH3).
P(HSAM-SA)1:1: 6.30 (brm, 2H, CO-CH=CH-CO), 4.98 (brm, IH, meshine), '.~4 (t,
CH2-COO-), 1.62 (tt, 2H, CH2-cH2-cooco-)~ 1.56 (dt, 4H, -cH2-co~cH-cH2-
(CH2)4-CH3 and -CH2-COaCH-CII2-(CH2)9-COa),1.32 and 1.'5 (two brd. 31ipha~ic
methylenes from HSAM and h~m SA),0.88 (t, 3H, CH2-CH3).
CA 02210800 1997-07-17
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WO 96122270
--29--
T~ 3. ~- :h-n~c~l prop~rti~ of f~tty ~ci~ polym~rs
Polymer Mw Mn Tensile Compression
co~"~ on Strength at b~
(~lP3) (%)
P(RAM-SA)l:1135,'00 5,300 3.2 buclcled before b~e~ng
P(HSAM-SA)l:l 4,300 2,100 2.7 22.95
P(HSAS-SA)1:1 9,400 3,300 2.5 20.91
P(FAD SA)I:173,000 5,900 5.7 9.75
PSA 18,600 5,800 7.~ 1.57
4 . D~t~ analy~i~ for ~iaci~ fat cont- ~ n~ n~
lacti~- copoly~-r~
Polymer: Viscosity Meltin~ point
(dL ~) (oC)
P(LA-RAM-PG!8:1:10.22 42~7
P(L9.-HSAM-PG)8:1:10.15 38-45
P(LA-HSAS-PG)8: 1:10.20 47-~0
CA 022l0800 l997-07-l7
W096122270 PCT/~S~007
-30-
~ R~C~8
1. Domb et al., Polymeric Biomateria}s, NY (in press)
2. Domb et al., Polym. Adv. ~echnol. (in press)
3. Domb et al., Biopolymers (in press)
4. Leong et al., Biomed. Mat. Res, 19:941 (1985)
5. Domb and Maniar (1993) J. Polymer Sci.:Part A:Polymer
Chem. 31:1275-1285
6. Domb and Langer ( 1987) J. Polym. Sci. Part A: Polym.
Chem., 1987, 25:3373
7. Ratacliffe et al. (1984) J. Pharm. Pharmacol. 36:431
8. Laurencin et al. (1990) J. Biomed. Mat. Res, 24:1463
