U.S. patent application number 09/885287 was filed with the patent office on 2002-02-14 for coating for metallic implant materials.
This patent application is currently assigned to Merck Patent Gesellschaft mit Beschrankter Haftung. Invention is credited to Dard, Michel, Rossler, Sophie, Scharnweber, Dieter, Sewing, Andreas, Worch, Hartmut.
Application Number | 20020018798 09/885287 |
Document ID | / |
Family ID | 7645842 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020018798 |
Kind Code |
A1 |
Sewing, Andreas ; et
al. |
February 14, 2002 |
Coating for metallic implant materials
Abstract
A biomimetically produced bone-analogous coating, comprising
organic and inorganic main constituents, is suitable for coating
metallic implant materials of any desired surfaces. The coating
comprises a collagen matrix mineralized with calcium phosphate.
Inventors: |
Sewing, Andreas; (Dieburg,
DE) ; Dard, Michel; (Seeheim-Jugenheim, DE) ;
Rossler, Sophie; (Dresden, DE) ; Scharnweber,
Dieter; (Dresden, DE) ; Worch, Hartmut;
(Dresden, DE) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Assignee: |
Merck Patent Gesellschaft mit
Beschrankter Haftung
Postfach
Darmstadt
DE
|
Family ID: |
7645842 |
Appl. No.: |
09/885287 |
Filed: |
June 21, 2001 |
Current U.S.
Class: |
424/423 ;
623/16.11 |
Current CPC
Class: |
A61L 27/34 20130101;
A61L 2430/02 20130101; A61L 27/34 20130101; C08L 89/06 20130101;
A61L 27/46 20130101; A61L 27/54 20130101; C08L 89/06 20130101; A61L
27/34 20130101 |
Class at
Publication: |
424/423 ;
623/16.11 |
International
Class: |
A61F 002/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2000 |
DE |
DE 100 29 520.7 |
Claims
1. A bone-analogous coating for metallic implant materials,
comprising a collagen matrix mineralized with a calcium phosphate
phase.
2. A coating according to claim 1, wherein the collagen matrix is
layered.
3. A coating according to claim 1, wherein the calcium phosphate
phase of the matrix contains amorphous calcium phosphate
(Ca.sub.9(PO.sub.4).sub.6- .nH.sub.2O), hydroxyapatite
(Ca.sub.10(PO.sub.4).sub.6(OH).sub.2), octacalcium phosphate
(Ca.sub.8H.sub.2(PO.sub.4).sub.6.5H.sub.2O), brushite
(CaHPO.sub.4.2H.sub.2O) or mixtures thereof.
4. A coating according to claim 1, wherein the calcium phosphate
phase is doped with fluoride, silver, magnesium or carbonate ions
or combinations thereof.
5. A coating according to claim 1, wherein the collagen is collagen
of type I.
6. A coating according to claim 1, wherein the collagen is a
mixture of collagen of types I to III.
7. A coating according to claims 1, wherein said coating further
contains gelatin.
8. A coating according to claims 1, further containing growth
factors, peptide sequences, hormones, antibiotics or mixtures
thereof.
9. A coated metallic implant comprising a metallic implant having
an outer layer, wherein the outer layer comprises a coating
according to claim 1.
10. A coated metallic implant according to claim 9, wherein the
metallic implant is made of titanium or titanium alloy.
11. A process for the electrochemical coating of metallic implant
materials with a mineralised collagen matrix comprising: a) coating
a metallic implant material by immersion in a collagen solution at
a pH of less than 8 and a temperature 4-40.degree. C., and b)
coating said metallic implant material with a calcium phosphate
phase (CPP) in an electrochemically assisted process by means of
galvanostatic polarization in an electrolyte solution comprising
calcium ions and phosphate ions, wherein process steps a) and b)
are performed simultaneously or sequentially.
12. A process according to claim 11, wherein an additional process
step b) is placed in front of process step a).
13. A process according to claim 11, wherein the process steps a)
and b) proceed alternately a number of times.
14. A process according to claim 11, wherein the process steps a)
and b) are combined into one step, the metallic implant material to
be coated being electrochemically polarized cathodically in a
collagen solution comprising calcium ions and phosphate ions.
15. A process according to claim 11, wherein a cathodic current
flow of -0.2 to -50 mA/cm.sup.2 flows for 25 to 40 minutes during
the galvanostatic polarization in process step b).
16. A process according to claims 11, wherein the mineralised
collagen matrix is layered.
17. A process according to claims 11, wherein the coating further
comprises gelatin.
18. A process according to claim 11, wherein a cathodic current
flow of -0.5 to -30 m/cm.sup.2 flows for 30 to 40 minutes during
the galvanostatic polarization in process step b).
19. A process according to claim 11, wherein a cathodic current
flow of -1 to -10 mA/cm.sup.2 flows during the galvanostatic
polarization in process step b).
20. A process according to claim 11, wherein the galvanostatic
polarization in process step b) is performed at a temperature of
30-40.degree. C.
21. A coated metallic implant comprising a metallic implant having
an outer layer, wherein the outer layer is 0.04-150 .mu.m thick and
comprises a coating according to claim 1.
Description
[0001] The invention relates to a biomimetically produced
bone-analogous coating, comprising an organic and inorganic main
constituent, for metallic implant materials of any desired surface
geometry and to a process for its preparation. The main components
of this coating are collagen and calcium phosphate phases which
form the organic and inorganic main constituent of the bone. The
coating according to the invention is suitable to a particular
extent as a matrix for the inclusion of further inductive
substances such as growth factors, adhesion proteins or
pharmacological active compounds.
[0002] On the question of an improved adaptation of the
physicochemical and biochemical properties of the surfaces of
implants to the local surrounding tissue with the aim of optimizing
the biocompatibility and biofunctionality, various approaches have
been followed.
[0003] In addition to mere changes in the topography of the implant
surface, such as etching or sand blasting, at present coatings with
calcium phosphate phases (CPP) play an important role. Most widely
advanced in use is the coating of implants in contact with bone
with hydroxyapatite and increasingly also more readily soluble
calcium phosphate phases [Yang et al., J. Mater. Sci., Mater. in
Med. 6, 258-65 (1995); Remer, P., Schwerpunktprogramm
Gradientenwerkstoffe, 3rd Ed. Darmstadt 31.3.1998; Floquet et al.,
Rev. Stomatol. Chir. Maxillofac. 98, 47-9 (1997)]. These methods
for the coating of implants with the inorganic main component of
bone and compounds derived therefrom aim particularly at a more
rapid establishment of the implant due to a locally increased
supply of calcium and phosphate ions. The coating of implant
surfaces with calcium phosphate phases (CPP) is at present mainly
carried out by plasma spraying processes. On account of the process
conditions, these layers have properties which differ strongly in
crystallinity and solution behaviour from the mineral phase of the
bone and on account of the high layer thicknesses can lead to the
mechanical failure of the layers [Filiaggi et al., J. Biomed. Mat.
Res. 27(2), 191-8 (1993); Gross et al., Int. J. Oral Maxillofac.
Implants 12 (5), 589-97 (1997); Posner et al., Phosphate Minerals,
Springer Verlag, Berlin/Heidelberg (1984)].
[0004] Electrochemically assisted processes [Shirkhanzadeh, J.
Mater. Sci.:Mater. in Med. 9, 76-72 (1998); Szmukler-Moncler et
al., Biological Mech. Of Tooth Eruption, Resorption and Replacement
by implants (Eds. Z. Davidovitch and J. Mah), 481-85 Harvard
Society for the Advancement of Orthodontics, Boston, USA (1998)]
offer the possibility of producing calcium phosphate phases (CPP)
with lower layer thicknesses. The deposition of calcium phosphate
phases (CPP) is realized by cathodic polarization of the implant in
Ca.sup.2+/H.sub.xPO.sub.4.sup.(3-x)--conta- ining solution. The
polarization of the implant leads to an alkalization of the
electrolyte near to the surface (2H.sub.2O+2e.sup.-.fwdarw.H.sub.2-
+2OH.sup.-), by means of which a precipitation reaction is induced
in front of the sample surface and the precipitation product formed
is deposited on the metallic implant surface.
[0005] A further approach to the field of surface modification of
implant materials consists in achieving a `biologization` of
implant surfaces by utilizing organic compounds occurring in
surrounding tissue for the surface modification. In this
connection, on the one hand, immobilized proteins and protein
sequences are used which exert their action in the immobilized
state (collagen, adhesion proteins, RGD sequences) or proteins
which are released over a certain period of time. Depending on the
immobilized substance, a largely general, positive action on the
biocompatibility of the implant surface (collagen, certain adhesion
proteins) or the adhesion of certain cell types is aimed at
(extended RGD sequences) [Schaffner et al., J. of Mat. Sci.: Mat.
in Med. 10, 837-39 (1999)].
[0006] The prior art previously mentioned shows that processes
which have set themselves the goal of the production of a
bone-analogous composite phase, formed from the inorganic and
organic constituents of the bone for the coating of metallic
implants were unknown up to now. Methods which comprise both
hydroxyapatite and collagen are only restricted to mixtures of the
components which are moreover assigned to further exogenous
substances as carrier materials.
[0007] WO 99/30672 (Uni Tubingen) describes a coating for
prostheses of organic polymer material in whose surface
hydroxyapatite or collagen can be included. The polymer material
here is only the adhesion promoter; a composite of collagen and a
calcium phosphate phase which is similar to bone cannot be referred
to.
[0008] A further possibility for the inclusion of scleroproteins
and calcium phosphate is presented in DE19811900 (Feinchemie). A
biocompatible composite material consisting of an inorganic gel and
a bioactive component (collagen, elastin, fibrin) is described.
Moreover, calcium phosphates or their precursors can be present in
the dissolved form. This composite material is accordingly only a
mixture of the main constituents of the bone, which is moreover
assigned to an inorganic gel as a carrier.
[0009] In WO 92/13984 (Queen's University of Kingston), a process
for the electrochemical production of ceramic coatings from calcium
phosphate compounds is described. It is not excluded here that the
electrolyte also contains biological non-toxic compounds such as
collagen or impurities. The coating is a uniform microporous
ceramic material made of associated nonorientated crystallites.
This layer can also contain biologically active compounds as
precipitation products. As a ceramic calcium phosphate coating, the
coating described accordingly differs markedly from a mineralized
collagen/calcium phosphate matrix.
[0010] Implants for use in the maxillary area or joint replacement
are preferably manufactured from metallic materials in order to
meet the mechanical demands. Here, the immediate surface, which can
differ greatly from the basic material in its properties, is often
neglected. However, it is known that the properties of the surface
especially are of crucial importance for the interactions between
implant and surrounding tissue. Thus conformational changes of
adsorbed proteins can contribute significantly to formation of a
fibrous intermediate layer, which in turn can result in an
inadequate stability of the implant.
SUMMARY OF THE INVENTION
[0011] A teaching of the present invention starts from the object
of modifying implant surfaces specifically with biochemical
information in order to achieve a rapid osteointegration with
formation of high-grade bony tissue after implantation.
[0012] Upon further study of the specification and appended claims,
further objects and advantages of this invention will become
apparent to those skilled in the art.
[0013] The objects are achieved by means of a bone-analogous
coating, comprising organic and inorganic main constituents, for
implant materials of any desired surface geometry, the coating
comprising a collagen matrix mineralized with calcium
phosphate.
[0014] Suitable implant materials are generally conductive
materials such as conductive polymers or metals used in dental
technology or in the endoprosthesis and trauma fields. Titanium and
titanium alloys such as TiAl.sub.6V.sub.4 are particularly
preferred.
[0015] The coating according to the invention is produced under
conditions which make possible the inclusion of organic components.
For the biomimetic production of a matrix which is analogous to
bone, the invention therefore utilizes electrochemically assisted
processes, which can be carried out under almost physiological pH
and temperature conditions and thus make possible the inclusion of
biomolecules.
[0016] These can be present in the electrolyte solution or in
immobilized form on the implant surface. The main components of the
layer consist of collagen and hydroxyapatite, the organic and
inorganic main component of the bone. By means of the subject
according to the invention, it is possible for the first time to
comprehend a permeable structure, analogous to the bone structure
produced in vivo, in its essential features in vitro and to produce
it with good adhesion to a metallic implant surface.
[0017] The mineralised collagen matrix is constructed in the form
of layers. This has the advantage that by means of this the
production of graded layers having a varying degree of
mineralization of the collagen matrix is also possible. The
preferred overall thickness of the matrix coating is about 0.04
.mu.m-150 .mu.m, especially about 3-8 .mu.m. The preferred range
for the typical dimensions of the hydroxyapatite crystals is about
300-500 nm in length and 50-60 nm in diameter.
[0018] The inorganic main constituent or the calcium phosphate
phase (CPP) preferably contain amorphous calcium phosphate
(Ca.sub.9(PO.sub.4).sub.6.- nH.sub.2O), hydroxyapatite
(Ca.sub.10(PO.sub.4).sub.6(OH.sub.2), octacalcium phosphate
(Ca.sub.8H.sub.2 (PO.sub.4).sub.6.H.sub.2O) or brushite
(CaHPO.sub.4.2H.sub.2O). However, mixtures of the phases mentioned
beforehand are also possible.
[0019] The calcium phosphate phase can additionally be doped with
ions such as fluoride, silver, magnesium or carbonate.
[0020] The use of type I collagen is preferred, which is
responsible in the bone for the elastic properties and in the
mineralized state brings about the high strength of the bone
together with the hydroxyapatite crystallites. Furthermore, the
collagen can also be a mixture of the types I to III. The types I
to III belong to the group of fibril-forming collagens. Gelatin can
additionally be added to the collagen. In addition to collagen,
which can also be derived from recombinant production, the
inclusion of other matrix proteins is also possible.
[0021] A further advantage of the invention involves the
possibility of utilizing the layers described as a matrix for
bone-specific proteins (BMP, TGF.beta. etc.). In addition to growth
factors and cell-specific adhesion peptides, the inclusion of
pharmacological active compounds, such as antibiotics, is also
possible.
[0022] The invention further relates to a metallic implant made of
a parent substance and of an outer layer carried by this, the outer
layer being a coating according to the invention.
[0023] The invention also relates to a process for the
electrochemically assisted coating of metallic implant materials of
any desired surface with collagen and calcium phosphate phases
(CPP), comprising
[0024] a) coating of the metallic implant material by immersion in
a collagen solution at a pH of about less than 8 and a temperature
of about 4 to 40.degree. C. for a few minutes.
[0025] b) coating of the collagen-coated sample with calcium
phosphate phases (CPP) in an electrochemically assisted process by
means of galvanostatic polarization in an electrolyte solution
comprising calcium ions and phosphate ions under defined current
density and temperature. The preferred ranges for current density
and temperature are, respectively about -0.2 to -50 mA/cm.sup.2 and
about 30-40.degree. C., more preferably a current density of about
-1 to -10 mA/cm.sup.2 and a temperature of about 37.degree. C.
[0026] The above process steps a and b may be preformed
simultaneously or sequentially.
[0027] The coating can be carried out in an electrolysis cell in
which the metallic implant is cathodically polarized. The layer
deposition takes place near to physiological pH and temperature
conditions. The electrolyte comprises a
Ca.sup.2+/H.sub.xPO.sub.4.sup.(3-x)--containing solution, which can
additionally contain collagen or other substances (growth factors,
antibiotics). The implant surface can have any desired surface
geometry (structure; rough, polished, etched), a chemical
modification (generation of functional groups), a calcium phosphate
layer, a protein layer and a layer prepared according to Patent No.
WO 98/17844 (TU Dresden) or DE-19504386 (TU Dresden) or a
combination thereof. By means of a process of calcium phosphate
deposition and the immobilization of collagen under physiological
pH and temperature conditions, which is carried out simultaneously,
a mineralized collagen layer can be produced on the titanium
surface. The degree of the mineralization, i.e. the nature of the
calcium phosphate phases (CPP) and degree of coating, are specified
here by the electrochemical parameters. This process can be
assisted by the addition of groups of substances influencing
mineralization (e.g. bone sialoprotein, osteopontin).
[0028] Preferably, the coating process comprises firstly carrying
out a coating of the sample with calcium phosphate phases (CPP) in
an electrochemical process via galvanostatic polarization in an
electrolyte solution comprising calcium ions and phosphate ions at
defined current density and temperature, followed by a coating of
the sample, coated with calcium phosphate phases (CPP), by
immersion in a collagen solution at a pH of less than 8 and a
temperature of about 4 to 40.degree. C. for a few minutes, and
subsequently coating of the collagen/CPP-coated sample with further
calcium phosphate phases (CPP) in a fresh electrochemical process
by means of galvanostatic polarization under defined current
density and temperature.
[0029] The process steps mentioned beforehand can preferably also
proceed a number of times under alternating conditions, i.e. a
sequence of the process steps a) and b) according to the scheme
a-b-a-b-a-b etc.
[0030] Also preferred is a process in which the process steps a)
and b) are combined into one step, the metallic implant material to
be coated being electrochemically polarized cathodically in a
collagen solution comprising calcium ions and phosphate ions.
[0031] A process is even more preferred in which a cathodic current
flow of -0.5 to -30 mA/cm.sup.2 flows for approximately 30 minutes
during the galvanostatic polarization in process step b).
[0032] The advantages of the mineralised bone-analogous collagen
matrix according to the invention can be shown impressively in the
cell test. While cell adhesion for osteoblasts still shows
comparatively good values with biomimetically produced
hydroxyapatite layers after one hour, cell proliferation on the
layers according to the invention is clearly preferred. The
increase in the cell count takes place here at a significantly
earlier point in time and the maximum value of the cell count is
very much more rapidly achieved than for pure hydroxyapatite
layers. A corresponding measurement curve for a proliferation test
over the course of 17 days with MC3T3 mouse osteoblasts is shown in
FIG. 1.
[0033] The invention is described and explained in greater detail
below with the aid of exemplary embodiments with reference to FIG.
1.
[0034] In the foregoing and in the following examples, all
temperatures are set forth uncorrected in degrees Celsius; and,
unless otherwise indicated, all parts and percentages are by
weight.
[0035] The entire disclosure of all applications, patents and
publications, cited above and below, and of corresponding German
Application No. 100 29 520.7, filed Jun. 21, 2000 is hereby
incorporated by reference.
EXAMPLE 1
[0036] A cylinder of TiAl.sub.6V.sub.4 (h=2 mm, .O slashed.10 mm)
is metallographically prepared using a sealing TiO.sub.2 polish.
The cylinder is then cleaned in acetone and ethanol in an
ultrasonic bath and rinsed with distilled water.
[0037] The sample is then immersed in a collagen solution which is
prepared in the following manner: acid-soluble freeze-dried calf
skin collagen type I is dissolved in 0.01 M acetic acid and
adjusted to a concentration of 0.1 mg/ml at 4.degree. C. The
collagen molecules are reconstituted in two process steps: pH
adjustment to 7.4 using double-concentrated phosphate buffer and
temperature increase to 36.degree. C. After 3 hours, the solution
consists of native reconstituted fibrils. The sample remains in
this solution for 10 minutes, then it is rinsed with deionized
water.
[0038] The sample coated with collagen is incorporated as a working
electrode in a three-electrode arrangement, consisting of a
saturated calomel electrode as reference electrode and a platinum
sheet as counter-electrode in a thermostated electrolysis cell. The
electrolyte solution used is a stock solution which is prepared in
the following way: 10 ml of stock solution of CaCl.sub.2 and
NH.sub.4H.sub.2PO.sub.4 in each case, in the concentrations 33 mM
and 20 mM, are diluted and mixed so that 200 ml result; 1.67 mM in
calcium ions and 1.0 mM in phosphate ions. The pH is adjusted to
6.4 using dilute NH.sub.4OH solution.
[0039] After connection to the potentiostat, mineralization/coating
with calcium phosphate phases (CPP) is carried out by means of
galvanostatic polarization under cathodic current flow at -1
mA/cm.sup.2. After 30 minutes, the cathodic polarization is
complete; the sample is taken out of the electrolyte solution and
rinsed with deionized water. The deposited layer appears whitish.
Electron-microscopic examination shows a layer consisting of a
collagen network and spherical CP clusters. IR-spectroscopic
investigations furnish proof that the mineral phase consists of
amorphous calcium phosphate.
EXAMPLE 2
[0040] A cylinder of TiAl.sub.6V.sub.4 is prepared as in Example 1.
The construction of the electrolysis cell and the electrolyte for
calcium phosphate deposition are identical to that in Example 1.
After connection to the potentiostat, coating with CPP is carried
out by means of galvanostatic polarization under cathodic current
flow at -10 mA/cm.sup.2. After 30 minutes, the cathodic
polarization is interrupted, and the sample is taken out of the
electrolyte solution and rinsed with deionized water. A crystalline
CPP, hydroxyapatite, is now present on the TiAl.sub.6V.sub.4
surface. The sample is now immersed in a collagen solution which is
identical to that in Example 1. The sample coated with
hydroxyapatite remains in this solution for 10 minutes, then it is
rinsed with deionized water and again incorporated into the
electrolysis cell. After connection to the potentiostat, deposition
of hydroxyapatite again takes place by means of galvanostatic
polarization under cathodic current flow at -10 mA/cm.sup.2. After
20 min, the sample is taken out and rinsed with deionized water.
The deposited layer appears whitish. Electron-microscopic
examination shows a closed layer which consists of agglomerates of
small needles. A network of mineralized collagen fibrils is
situated on this layer. IR-spectroscopic and X-ray diffraction
investigations furnish proof that the mineral phase consists of
hydroxyapatite. The characteristic amide bands in the IR spectrum
furthermore show that the collagen is not present in denatured
form, but on the contrary a good agreement exists between the
mineralized layer and a spectrum for native bone.
EXAMPLE 3
[0041] A cylinder of TiAl.sub.6V.sub.4 is prepared as in Example 1.
The construction of the electrolysis cell is identical to that in
Example 1.
[0042] A collagen solution containing native assembled collagen
fibrils is prepared as in Example 1. This solution is centrifuged
at 5 000 g and 4.degree. C. for 15 min, and the pellet is taken up
with deionized water and dispersed by shaking. The solution is then
centrifuged at 5 000 g and 4.degree. C. again for 15 min. The
pellet obtained in the centrifugation is now taken up in the
electrolyte for calcium phosphate deposition described in Example 1
and homogenized by means of a disperser.
[0043] This solution is used as an electrolyte for a simultaneously
carried-out process for the deposition and mineralization of
collagen. After connection to the potentiostat, mineralization is
carried out by means of galvanostatic polarization under cathodic
current flow at -10 mA/cm.sup.2. After 30 minutes, the cathodic
polarization is complete, and the sample is taken out of the
electrolyte solution and rinsed with deionized water.
[0044] The deposited layer appears whitish. Electron-microscopic
examination shows a composite of collagen fibrils and CPP.
IR-spectroscopic and X-ray diffraction investigations furnish proof
that the mineralization of the fibrils takes place mainly by means
of the crystalline phase hydroxyapatite. The more readily soluble
amorphous calcium phosphate phase is partially found. The
characteristic amide bands in the IR spectrum furthermore show that
the collagen is not present in denatured form, but on the contrary
a good agreement exists between the mineralized layer and a
spectrum for native bone.
EXAMPLE 4
[0045] A cylinder of TiAl.sub.6V.sub.4 is prepared as in Example 1.
The construction of the electrolysis cell and the electrolyte for
the calcium phosphate deposition are identical to that in Example
1. After connection to the potentiostat, coating with CPP by means
of galvanostatic polarization is carried out under cathodic current
flow at -10 mA/cm.sup.2. After 30 minutes, cathodic polarization is
interrupted, and the sample is taken out of the electrolyte
solution and rinsed with deionized water. A crystalline CPP,
hydroxyapatite, is now present on the TiAl.sub.6V.sub.4 surface.
The sample is now immersed in a collagen solution which is
identical to that in Example 1. The sample coated with
hydroxyapatite remains in this solution for 10 minutes, then it is
rinsed with deionized water and again incorporated into the
electrolysis cell. After connection to the potentiostat, partial
mineralization of the collagen is carried out under cathodic
current flow at -10 mA/cm.sup.2 for 15 min. Finally, the sample is
rinsed with deionized water. The deposited layer appears whitish.
In a second process step, the binding of integrin-specific
cell-selective peptide sequences to the immobilized collagen layer
is carried out. The binding is carried out covalently by means of a
thiol anchor and SMPB (sulfosuccinimidyl
4-(pmaleimidophenyl)butyrate) to the phosphate groups of the
collagen.
[0046] Electron-microscopic examination shows a homogeneous layer
of hydroxyapatite needles, on which a partially mineralized network
of collagen fibrils is present. The activity of the RGD sequences
is evident from adhesion and proliferation experiments using
MC3T3-E1 cells. Relative to comparable pure collagen layers, the
RGDcoated surfaces show increased cell adherence and cell
proliferation beginning after shorter times.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] Various other features and attendant advantages of the
present invention will be more fully appreciated as the same
becomes better understood when considered in conjunction with the
accompanying drawings, in which like reference characters designate
the same or similar parts throughout the several views, and
wherein:
[0048] FIG. 1
[0049] shows the cell proliferation of MC3T3 mouse osteoblasts on
hydroxyapatite and on the bone-analogous collagen/hydroxyapatite
matrix, in each case on TiAl.sub.6V.sub.4 substrates. The
absorption is proportional to the cell count (WST-1 test).
[0050] The preceding examples can be repeated with similar success
by substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples.
[0051] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *