U.S. patent application number 11/104771 was filed with the patent office on 2005-08-25 for method of promoting osteogenesis.
This patent application is currently assigned to INION LTD.. Invention is credited to Kaikkonen, Auvo, Nieminen, Tuomo, Nieuwenhuis, Jan, Pirhonen, Eija, Weber, Franz.
Application Number | 20050186251 11/104771 |
Document ID | / |
Family ID | 21722648 |
Filed Date | 2005-08-25 |
United States Patent
Application |
20050186251 |
Kind Code |
A1 |
Pirhonen, Eija ; et
al. |
August 25, 2005 |
Method of promoting osteogenesis
Abstract
Novel polymer compositions that are useful in the manufacture of
medical implants, implants having osteogenic properties and methods
of making said implants are disclosed. Polymer compositions
comprise a base material including a polymer matrix of resorbable
polymer(s) or copolymer(s), and N-methyl-2-pyrrolidone (NMP),
wherein NMP is present in an amount imparting osteogenic properties
for the composition.
Inventors: |
Pirhonen, Eija; (Tampere,
FI) ; Nieuwenhuis, Jan; (Gorinchem, NL) ;
Kaikkonen, Auvo; (Tampere, FI) ; Nieminen, Tuomo;
(Tampere, FI) ; Weber, Franz; (Singen,
DE) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
28 STATE STREET
28th FLOOR
BOSTON
MA
02109-9601
US
|
Assignee: |
INION LTD.
Tampere
FI
|
Family ID: |
21722648 |
Appl. No.: |
11/104771 |
Filed: |
April 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11104771 |
Apr 13, 2005 |
|
|
|
10006800 |
Dec 4, 2001 |
|
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Current U.S.
Class: |
424/426 |
Current CPC
Class: |
A61L 27/18 20130101;
A61P 19/08 20180101; A61L 27/58 20130101; A61L 27/18 20130101; C08L
67/04 20130101; A61K 31/4015 20130101 |
Class at
Publication: |
424/426 |
International
Class: |
A61F 002/00 |
Claims
1. A method of promoting osteogenesis comprising the steps of:
providing a resorbable polymer composition comprising a base
material including a polymer matrix of resorbable polymer(s) or
copolymer(s), and N-methyl-2-pyrrolidone (NMP), wherein NMP is
present in an amount imparting osteogenic properties for the
composition, and implanting the resorbable polymer composition into
a recipient to promote osteogenesis.
2-11. (canceled)
12. The method of claim 1, wherein NMP is present in an amount
between 0.05 and 50 weight- %.
13. A method of promoting osteogenesis comprising the steps of:
selecting polymer(s) or copolymer(s), adding NMP to the polymer(s)
or copolymer(s) in an amount imparting osteogenic properties to the
polymer(s) or copolymer(s), mixing the polymer(s) or copolymer(s)
to form a polymer matrix, forming an implant from the polymer
matrix, and implanting the implant into a recipient to promote
osteogenesis.
14. The method of claim 1, wherein the polymer matrix is selected
from a group consisting of polyglycolide, polylactides,
polycaprolactones, polytrimethylenecarbonates,
polyhydroxybutyrates, polyhydroxyvalerates, polydioxanones,
polyorthoesters, polycarbonates, polytyrosinecarbonates,
polyorthocarbonates, polyalkylene oxalates, polyalkylene
succinates, poly(malic acid), poly(maleic anhydride), polypeptides,
polydepsipeptides, polyvinylalcohol, polyesteramides, polyamides,
polyanhydrides, polyurethanes, polyphosphazenes,
polycyanoacrylates, polyfumarates, poly(amino acids), modified
polysaccharides, modified proteins and their copolymers,
terpolymers or combinations or mixtures or polymer blends
thereof.
15. The method of claim 1, wherein the polymer matrix is selected
from the group consisting of polyglycolide,
poly(L-lactide-co-glycolide), poly(D,L-lactide-co-glycolide),
poly(L-lactide), poly(D,L-lactide), poly(L-lactide-co-D,L-lactide),
polycaprolactone, poly(L-lactide-co-capro- lactone),
poly(D,L-lactide-co-caprolactone) polytrimethylenecarbonate,
poly(L-lactide-co-trimethylenecarbonate),
poly(D,L-lactide-co-trimethylen- ecarbonate), polydioxanone and
their copolymers, terpolymers or combinations or mixtures or
polymer blends thereof.
16. A method of promoting osteogenesis comprising the steps of:
selecting polymer(s) or copolymer(s) to form a polymer matrix,
forming an implant from said polymer matrix, adding NMP to the
implant, and implanting the implant into a recipient to promote
osteogenesis.
17. The method of claim 16, wherein NMP is added to the implant
preoperatively.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to novel polymer compositions
that are useful in the manufacture of medical implants. More
particularly, embodiments of the invention relate to polymer
compositions having osteogenic properties. The polymer compositions
are biodegradable or bioresorbable and they can be fashioned into
medical implants for implantation in the body. Implants having
osteogenic properties and methods of making said implants are also
disclosed.
BACKGROUND OF THE INVENTION
[0002] The healing process of bone is a complicated cascade of
events. Rapid and diverse events are activated by a fracture or
osteotomy of a bone in order to limit the loss of blood and
initiate cellular migration resulting in repair. Current concepts
suggest that these cellular events are controlled to a large part
by growth factors, low-molecular-weight glycoproteins, inducing
migration, proliferation and differentiation of an appropriate
subset of cells in the site of the fracture.
[0003] Despite of the amount of known details the bone healing as a
whole is still a poorly understood process. Based on this lacking
information and experimental data research has revealed several
methods to enhance bone growth, such as mechanical stimulation,
electromagnetic fields, low-intensity ultrasound, osteoconductive
materials, for instance hydroxyapatite, tricalcium phosphate,
bioactive glass etc., and osteoinductive materials, such as growth
factors.
[0004] Osteoinduction is a process where any substance, stimulation
etc. starts or enhances a cellular response resulting in a bone
formation process. Growth factors are a wide group of molecules
known to possess this effect. According to the current knowledge,
bone morphogenetic proteins (BMP) are the only growth factors known
to induce bone formation heterotopically by inducing
undifferentiated mesenchymal cells to differentiate into
osteoblasts. Consequently, several BMPs are shown to boost the bone
healing process when supplementary doses are given.
[0005] For example, U.S. Pat. No. 5,725,491 discloses a
biodegradable film dressing as a delivery system of various
therapeutic agents, such as BMPs. The therapeutic agent is
delivered from the film dressing in a certain and controlled
release rate. However, BMPs are produced by genetic engineering,
which is still rather expensive. Also, delivery of a correct dose
of BMPs is difficult and presents great challenges for the
future.
[0006] Known materials, methods and implants are expensive and
exploitation of such materials, methods and implants is
constrained.
BRIEF DESCRIPTION OF THE INVENTION
[0007] An object of the present invention is to provide novel
resorbable polymer compositions having osteogenic properties so as
to alleviate the above disadvantages. Another object is to provide
novel resorbable implants having osteogenic properties. A further
object is to provide methods of making resorbable implants having
osteogenic properties.
[0008] These objects are achieved by providing resorbable polymer
compositions, resorbable implants and methods of making resorbable
implants comprising a base material including a polymer matrix of
resorbable polymer(s) or copolymer(s) and N-methyl-2-pyrrolidone
(NMP).
[0009] According to one embodiment of the invention, the polymer
matrix comprises Polylactide/Polyglycolide/Trimethylene carbonate
copolymer (PLA/PGA/TMC) with a composition of 80/10/10.
[0010] According to another embodiment of the invention, the
polymer matrix comprises Poly D, L-lactide/Poly
L-lactide/Trimethylene carbonate copolymer (PLDLA/PLA/TMC) with a
composition of 55/40/5.
[0011] According to a third embodiment of the invention, the
polymer matrix comprises 80 wt-% P(L/DL)LA (70/30) and 20 wt-%
PLLA/TMC (70/30).
[0012] According to a fourth embodiment of the invention, the
implant is a membrane.
[0013] According to one embodiment of the method of the invention,
the method comprises the steps of selecting polymer(s) or
copolymer(s) of a polymer matrix of the implant, mixing said
polymer(s) or copolymer(s) to form the polymer matrix, forming the
implant from said polymer matrix, and adding NMP to the implant in
an amount imparting osteogenic properties for said implant.
[0014] According to another embodiment of the method of the
invention, the method comprises the steps of selecting polymer(s)
or copolymer(s) of a polymer matrix of the implant, adding NMP to
the polymer matrix in an amount imparting osteogenic properties for
the implant, and forming the implant from the mixture of said
polymer matrix and NMP.
[0015] An advantage of polymer compositions, implants and methods
of the invention is that substantially inexpensive products are
achieved as compared with known solutions enhancing bone
healing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In the following the invention will be described in greater
detail by means of preferred embodiments with reference to the
attached drawings, in which
[0017] FIG. 1a is a microscope view of a histological section of a
defect created in rabbit calvarial bone where said defect is
covered by a (PLA/PGA/TMC) 80/10/10 membrane treated with NMP as
described in example 1,
[0018] FIG. 1b is a second microscope view of a histological
section of a defect created in rabbit calvarial bone where said
defect is covered by an OsseoQuest membrane,
[0019] FIG. 1c is a third microscope view of a histological section
of a defect created in rabbit calvarial bone where said defect is
without any membrane, and
[0020] FIG. 2 is a graph showing repair of rabbit calvarial bone
defects.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention relates to a combination of
N-methyl-2-pyrrolidone (NMP) and resorbable polymers or copolymers.
The invention is based on the unexpected realization that by
combining a resorbable matrix material and NMP in a certain ratio,
an implant having osteogenic properties is achieved. The implant
thus induces bone growth due to the osteogenic properties of the
polymer composition and enhances bone healing after osteotomies and
bone fractures.
[0022] The implant forms include, but are not limited to,
membranes, films, plates, mesh plates, screws, taps or other formed
pieces.
[0023] The implant can be prepared for example of polyglycolide,
polylactides, polycaprolactones, polytrimethylenecarbonates,
polyhydroxybutyrates, polyhydroxyvalerates, polydioxanones,
polyorthoesters, polycarbonates, polytyrosinecarbonates,
polyorthocarbonates, polyalkylene oxalates, polyalkylene
succinates, poly(malic acid), poly(maleic anhydride), polypeptides,
polydepsipeptides, polyvinylalcohol, polyesteramides, polyamides,
polyanhydrides, polyurethanes, polyphosphazenes,
polycyanoacrylates, polyfumarates, poly(amino acids), modified
polysaccharides (like cellulose, starch, dextran, chitin, chitosan,
etc.), modified proteins (like collagen, casein, fibrin, etc.) and
their copolymers, terpolymers or combinations or mixtures or
polymer blends thereof. Polyglycolide,
poly(L-lactide-co-glycolide), poly(D,L-lactide-co-glycolide),
poly(L-lactide), poly(D,L-lactide), poly(L-lactide-co-D,L-lactide),
polycaprolactone, poly(L-lactide-co-caprolactone),
poly(D,L-lactide-co-caprolactone) polytrimethylenecarbonate,
poly(L-lactide-co-trimethylenecarbonate),
poly(D,L-lactide-co-trimethylen- ecarbonate), polydioxanone and
copolymers, terpolymers and polymer blends thereof are highly
preferred polymers.
EXAMPLE 1
[0024] Polylactide/Polyglycolide/Trimethylene carbonate copolymer
(PLA/PGA/TMC), with a composition of 80/10/10, granulates were
compression moulded to form a film with a thickness of 0.2 mm. Used
compression temperature was 180.degree. C. and pressure 130 bar.
From the film 10 rectangular pieces were cut, each with a width of
20 mm.
[0025] The weight of the individual film pieces were measured with
balance with an accuracy of 1 mg. The film pieces were then
immersed individually into NMP for 30 seconds. After immersion the
film pieces were air dried for 20 minutes and the weight of the
pieces was measured again.
[0026] The weight of the film pieces before and after immersion
into NMP are shown in table 1. The average amount of NMP diffused
into polymeric film was 44.19%.
1TABLE 1 The weight of the film pieces before and after immersion
into NMP Weight before Weight after NMP Polymer NMP immersion into
immersion into content content content NMP (mg) NMP (mg) (mg) (%)
(%) 56.41 98.95 42.54 57.01 42.99 67.29 115.40 48.11 58.31 41.69
60.22 105.40 45.18 57.13 42.87 59.77 101.35 41.58 58.97 41.03 56.48
110.25 53.77 51.23 48.77 66.62 118.52 51.9 56.21 43.79 64.16 114.42
50.26 56.07 43.93 62.58 114.24 51.66 54.78 45.22 56.29 104.32 48.03
53.96 46.04 62.53 114.82 52.29 54.46 45.54
[0027] GTR membranes produced with the method described here in
were used in a comparable rabbit study disclosed in example 2.
EXAMPLE 2
[0028] This rabbit study shows the osteogenetic effect of
PLA/PGA/TMC and PLDLA/PLA/TMC membranes when treated with NMP. The
details of the tested membranes can be found in the following table
2.
2TABLE 2 Materials and codes of example 2 Code Materials E1M-11 NMP
PLA/PGA/TMC (80/10/10), treated with NMP (see EXAMPLE 1) E1M-11
PLA/PGA/TMC (80/10/10) E1M-3 NMP PLDLA/PLA/TMC (55/40/5), treated
with NMP (as in EXAMPLE 1) E1M-3 PLDLA/PLA/TMC (55/40/5) OsseoQuest
PLA/PGA/TMC supplier W. L. GORE & Associates, Inc. E1M-11 with
holes PLA/PGA/TMC (80/10/10), with holes manufactured using Laser
TMC/PLA PLA/TMC (70/30)
[0029] The study design included eight rabbits with four 6-mm
artificial craniotomy defects each. The defects were treated with
biodegradable membranes and a commercial biodegradable OsseoQuest
membrane as shown in table 2. Controls treated without any
membranes were included, too. The matrixes of the resorbable
membranes are also presented in table 2.
[0030] The rabbits were sacrificed 4 weeks after the operation and
the calvarial bone excised. Thorough histological analysis was
performed in order to assess the degree and type of bone
regeneration.
[0031] FIGS. 1a to 1c illustrate examples of some histological
sections from the middle of the defect. It is clearly evident that
the bone formed during the 4-week repair phase is more a cancellous
bone than a cortical bone. A cellular interaction with the membrane
was not observed.
[0032] FIG. 2 shows the percentage of a full-thickness repair of
rabbit calvarial bone defects. The middle sections of the defects,
6 mm in diameter in the calvarial bone were evaluated. The
percentage of repair was determined by pixel number of the defect
filled with bone.times.100/pixel number of the defect area. The
different membranes are specified by name. `Control` means the
defect without the application of a membrane.
[0033] Evaluation of the level of a full-thickness repair of the
bone defect revealed that the use of membranes improved bone
healing. The percentage of repair without a membrane, i.e.
`control`, was 31.3.+-.4.1% of the defect area of the middle
section. Essential improvement of bone healing as compared with the
control was achieved with OsseoQuest (55.78.+-.9.9%), and E1M-11
NMP (77.6.+-.8.8%). A direct comparison of bone healing enhanced by
OsseoQuest and E1M-11 NMP shows a clearly better healing with
E1M-11 NMP. Furthermore, E1M-3NMP shows a healing effect
essentially similar to OsseoQuest.
[0034] As shown in FIG. 2 the membranes of the present invention,
i.e. E1M-3 NMP and E1M-11 NMP, increase markedly the healing
response in the defect as compared with the membranes with an
identical polymeric composition, i.e. E1M-3, E1M-11, that do not
comprise NMP.
EXAMPLE 3
[0035] According to one embodiment of the method of the present
invention, NMP is added to the polymer matrix that has been already
fashioned into the form of a medical implant.
[0036] Polymer compositions were prepared by dry-mixing
commercially available granular-form base materials with
commercially available copolymer additives. The material
composition was 80 wt-% P(L/DL)LA (70/30) and 20 wt-% PLLA/TMC
(70/30). The components were weighed according to a desired weight
ratio into a container which was then rotated in a Turbula T2F
shaker mixer for 30 minutes until a homogenous dry mixture was
obtained. The resulting mixture was then dried in vacuum at
60.degree. C. for 8 to 12 hours and thereafter melt-blended and
injection-moulded in to plate-shaped test pieces. The
injection-moulding machine used was a fully electric Fanuc Roboshot
Alpha i30A injection-moulding machine with a mould clamping force
of 300 kN. The injection unit was equipped with high speed (max. 66
cm.sup.3/s to 330 mm/s), high pressure (max. 2500 bar) injection
options. The barrel diameter was 16 mm and it was equipped with
three-band heater zones, a standard profile anticorrosion screw and
a standard open nozzle with a 2.5 mm hole. The extruder
melt-blending and homogenization conditions of the material during
the metering phase of the process included a back pressure of 40 to
60 bar, a screw speed of 60 to 100 rpm and barrel temperatures of
160 to 230.degree. C. Injection moulding conditions included a
nozzle temperature of 180 to 230.degree. C., an injection speed of
80 to 300 mm/s, a maximum injection pressure of 2500 bar, a pack
pressure of 1000 to 2300 bar for 3 to 8 s, a cooling time of 10 to
22 s and a mould temperature of 20 to 30.degree. C. The total cycle
time was 20 to 40 s consisting of the following phases during one
injection-moulding process cycle: closing of the mould, injection
of the molten polymer into the mould, pack pressure, cooling while
extruder was metering for the next cycle during cooling phase,
opening the mould and ejection of article from the mould.
[0037] The plates were sterilized by gamma irradiation with a
nominal dose of 25 kGy. After sterilisation, the plates were
submerged in NMP (1-Methyl-2-pyrrolidinone, 99%, Acros Organics,
Inc., USA) for 30 seconds. After submerging the plates were set for
30 minutes on a plastic holder at room conditions at 20.degree. C.
Thickness, length and mass of the plates were measured before
submerging and 30 minutes thereafter. Dimensions were measured with
a slide gauge and mass with an analysis balance. Additionally, 30,
60 and 120 minutes after the submerging of the plate, it was bent
to 45.degree. angle to find out softening and bending
characteristics of the plate. The diffusion depth of the NMP was
analysed with SmartScope Flash optical 3D-measuring device.
Approximately 1 mm of the material was cut off from the edge of the
plate. The depth of the diffusion was measured from the cut
cross-section of the plate 120 minutes after submerging. The
results of the NMP diffusion after 30 min of submerging are shown
in table 3.
3TABLE 3 Mass and dimensions of the plate before and after
submerging in the NMP Mass Thickness Mass of the of the of the NMP
outer plate in the Thickness layer Length (mg) plate (mg) (mm) (mm)
(mm) Initial 470.8 -- 1.01 0 23.5 30 min after 575.7 104.9 1.15
0.15 23.6 submerging
[0038] The thickness of the plate was increased 13% and its mass
was increased 22% due to the submerging of the plate in NMP. The
increase of the mass can be seen as the diffusion of NMP into the
plate. The increase of the thickness is due to the swelling of the
outer layer of the plate. The thickness of the swollen outer layer
of the plate was ca. 0.15 mm. The length was not changed due to the
submerging. Moreover, 30 minutes after submerging the plate was
softened and bendable by hand.
[0039] Resorbable polymer matrix absorbs NMP when immersed into it.
Thereafter, an implant loaded with NMP is implanted into the body,
and NMP is released gradually during a certain period of time. If
the rate of releasing is appropriate, NMP owns osteogenic
properties. As with almost any pharmaceuticals, the concentration
of NMP must be within certain limits, called a therapeutic window.
Below the window, NMP is inefficacious. Correspondingly, above the
window, NMP presents an adverse event by inhibiting certain
proteins, other molecules or cell lines. The NMP content is
preferably between 0.05 and 50 weight- %, more preferably between
0.1 and 10 weight-%.
[0040] According to one preferred embodiment of the method of the
present invention, NMP is mixed with a polymer matrix or one of its
components before the polymer matrix is fashioned into the form of
a medical implant. The mixing can take place in an extruder, in a
mixer or similar equipment known per se.
[0041] NMP may be applied to the implant as well by packing said
implant into a container with NMP already in the production
process. NMP will be absorbed to the polymer matrix of the implant
during storage in said container.
[0042] The polymer composition of the present invention can be
fashioned into implants by injection moulding, compression
moulding, extrusion or with another melt-moulding process known by
persons skilled in the art.
EXAMPLE 4
[0043] Example 4 presents one preferred embodiment of the present
invention, where the implant is a barrier membrane in Guided Tissue
Regeneration (GTR) to treat a periodontal defect.
[0044] The membrane comprises PLA/PGA-matrix polymers. The membrane
is packaged in a slot of a package, such as a plastic blister. The
preparation of the membrane is conducted as one stage of surgical
operation as follows:
[0045] 1. After opening the package, a proper amount of NMP is
poured into the membrane slot. The membrane is fully immersed in
NMP for an adequate period, for example 30 seconds to 3 minutes,
preferably for 30 seconds.
[0046] 2. The membrane is removed from the slot.
[0047] 3. NMP is allowed to diffuse into the polymer matrix of the
membrane for 15 to 20 minutes.
[0048] 4. The membrane is ready for use as a barrier between the
gingival soft tissue and the healing bone tissue and/or periodontal
tissues in order to prevent the gingival soft tissue filling the
defect side. In the conditions of a normal operating theater
temperature and humidity, the membrane stays malleable for several
hours.
[0049] Implants of the invention can be used for example in guided
bone regeneration applications, where the effect of a NMP loaded
barrier membrane is required to avoid soft tissue ingrowth in the
area where new bone formation is required, and to enhance bone
regeneration.
[0050] It will be obvious to a person skilled in the art that, as
the technology advances, the inventive concept can be implemented
in various ways. The invention and its embodiments are not limited
to the examples described above but may vary within the scope of
the claims.
* * * * *