U.S. patent application number 14/930436 was filed with the patent office on 2016-02-25 for hydrophilizing plasma coating.
The applicant listed for this patent is BIOENERGY CAPITAL AG. Invention is credited to Alexey KALACHEV, Thomas KORDICK, Guido SCHROTER.
Application Number | 20160053063 14/930436 |
Document ID | / |
Family ID | 47710084 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160053063 |
Kind Code |
A1 |
SCHROTER; Guido ; et
al. |
February 25, 2016 |
HYDROPHILIZING PLASMA COATING
Abstract
The invention relates to a method for hydrophilizing surfaces of
polymer workpieces. The method has a step (a) of pretreating the
workpiece surfaces in a high-frequency gas plasma which is produced
on the basis of an inert gas in order to clean and activate the
workpiece surfaces; a step (b) of precoating the pretreated
workpiece surfaces with polyacrylic acid using a high-frequency gas
plasma made of a gas mixture, said gas mixture being composed of an
inert gas and a first gas made of biocompatible, polymerizable
carboxy group-containing monomers; and a step (c) of subsequently
coating the precoated workpiece surfaces using a second gas
substantially containing acrylic acid monomers.
Inventors: |
SCHROTER; Guido; (Berlin,
DE) ; KALACHEV; Alexey; (Berlin, DE) ;
KORDICK; Thomas; (Goldbach, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BIOENERGY CAPITAL AG |
Koln |
|
DE |
|
|
Family ID: |
47710084 |
Appl. No.: |
14/930436 |
Filed: |
November 2, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14351504 |
Apr 11, 2014 |
9173974 |
|
|
PCT/EP2013/000329 |
Feb 1, 2013 |
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14930436 |
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Current U.S.
Class: |
428/336 ;
428/447 |
Current CPC
Class: |
A61L 27/34 20130101;
B05D 7/54 20130101; Y10T 428/31913 20150401; B05D 5/04 20130101;
B05D 3/144 20130101; B05D 1/60 20130101; B05D 1/62 20130101; Y10T
428/264 20150115; B05D 2502/00 20130101; A61F 2/1613 20130101; G02C
7/049 20130101; B05D 2201/00 20130101; B05D 3/0466 20130101; C08J
7/0427 20200101; C08J 2433/02 20130101; C08J 2383/04 20130101 |
International
Class: |
C08J 7/04 20060101
C08J007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 1, 2012 |
EP |
12000648.1 |
Feb 1, 2013 |
EP |
PCT/EP2013/000329 |
Claims
1-19. (canceled)
20. A biocompatible polymeric workpiece with a hydrophilic surface
coating layer made of poly(meth)acrylic acid, wherein the
biocompatible polymeric workpiece comprises, at least at its
surface, a material which is substantially formed of a silicone,
which surface is coated by a two-step process with the hydrophilic
surface coating layer of poly(meth)acrylic acid.
21. The biocompatible polymeric workpiece of claim 20, the coating
layer of poly(meth)acrylic acid having an average thickness of 2-12
.mu.m.
22. The biocompatible polymeric workpiece of claim 20, the first
step of the two steps of the process providing a lesser coating
layer thickness than the second step of the two steps of the
process.
23. The biocompatible polymeric workpiece of claim 20, the coating
layer of poly(meth)acrylic acid consisting of poly(acrylic acid),
PAA.
24. The biocompatible polymeric workpiece of claim 20, the coating
layer of poly(meth)acrylic acid consisting of a lower,
plasma-deposited layer and an upper layer deposited from the gas
phase without plasma action.
25. The biocompatible polymeric workpiece of claim 24, the lower,
plasma-deposited layer having a thickness of about 5-40 nm.
26. The biocompatible polymeric workpiece of claim 24, the coating
layer of poly(meth)acrylic acid having an average thickness of 2-12
.mu.m.
27. The biocompatible polymeric workpiece of claim 24, the lower,
plasma-deposited layer being thinner than the upper layer deposited
from the gas phase without plasma action.
28. The biocompatible polymeric workpiece of claim 24, the coating
layer of poly(meth)acrylic acid consisting of poly(acrylic acid),
PAA.
29. The biocompatible polymeric workpiece of claim 20, wherein the
workpiece, except for the coating layer, consists entirely of the
silicone.
30. The biocompatible polymeric workpiece of claim 29, the coating
layer of poly(meth)acrylic acid having an average thickness of 2-12
.mu.m.
31. The biocompatible polymeric workpiece of claim 29, the lower,
plasma-deposited layer being thinner than the upper layer deposited
from the gas phase without plasma action.
32. The biocompatible polymeric workpiece of claim 29, the coating
layer of poly(meth)acrylic acid consisting of poly(acrylic acid),
PAA.
33. The biocompatible polymeric workpiece of claim 29, the coating
layer of poly(meth)acrylic acid consisting of a lower,
plasma-deposited layer and an upper layer deposited from the gas
phase without plasma action.
34. The biocompatible polymeric workpiece of claim 33, the lower,
plasma-deposited layer having a thickness of about 5-40 nm.
35. The biocompatible polymeric workpiece of claim 33, the coating
layer of poly(meth)acrylic acid having an average thickness of 2-12
.mu.m.
36. The biocompatible polymeric workpiece of claim 33, the lower,
plasma-deposited layer being thinner than the upper layer deposited
from the gas phase without plasma action.
37. The biocompatible polymeric workpiece of claim 33, the coating
layer of poly(meth)acrylic acid consisting of poly(acrylic acid),
PAA.
Description
[0001] The present invention relates to the surface treatment of
workpieces on the basis of biomaterials and in particular relates
to the permanent hydrophilizing of surfaces of such workpieces by
means of plasma enhanced chemical vapour deposition (PECVD) and
subsequent chemical vapour deposition (CVD).
[0002] There are high requirements to the biological compatibility
of workpieces intended for temporary or permanent use in human or
animal organs, such as e.g. contact lenses or implants, in order to
avoid inflammatory processes. In order to accordingly ensure a high
biocompatibility, the materials employed for manufacturing such
workpieces have properties predestining them both for the
respective use as also for the ensuing tissue contact.
[0003] The biological compliance of materials, also termed
bio-compatibility, is determined to a large extent by their surface
properties. For contact lenses, a hydrophilic surface is decisive
for a good bio-compatibility. For implants in the context of Tissue
Engineering (build-up of autologous tissue), a hydrophilic surface
of polymeric scaffold substances improves their being colonized by
tissue cells and, thereby, the therapeutic success. Also, in in
vitro testing methods with vital cells, a hydrophilic surface of
the polymeric substrate is advantageous for fixing the cells.
[0004] A biocompatible hydrophilizing of surfaces of polymeric
bio-materials may be achieved by a modification of the polymeric
surface by means of plasma oxidation, as described e.g. in the
international application WO 99/57177. It turned out, however, that
such hydrophilized surfaces are not sufficiently long-term
stable.
[0005] A more permanent hydrophiliation of polymeric biomaterial
surfaces is achieved by coating same with a hydrophilic
biocompatible material. In order to manufacture hydrophilic
surfaces on contact lenses made of polymethylmethacrylate (PMMA),
in the patent document U.S. Pat. No. 5,080,924 e.g. a plasma
deposition process for graft polymerising the surfaces with
polyacrylic acid has been suggested. The graft polymerised
PMMA-surfaces showed contact angles of water in the range of 35 to
50 degrees and are too large for a sufficient wetting of the
material's surface. For further reducing the contact angle, the
coating needs to be post-treated, e.g. by applying a further
biocompatible material different from polyacrylic acid, which
cross-links to the polyacrylic acid. Such a process involving
coating plural layers requires a higher apparative effort and also
results in longer coating times.
[0006] Starting out from what has been described above, it is
therefore desirable to provide a less complex coating of polymeric
biomaterials which enables a long-term stable surface
hydrophilation with water contact angles of 15 degrees or less.
[0007] Such coating comprises a process for hydrophilizing surfaces
of polymeric workpieces, wherein the process comprises a step (a)
of cleaning and activating the work piece surfaces in the course of
a pre-treatment with a high-frequency gas plasma formed on the
basis of an inert gas, a step (b) of pre-coating the pre-treated
workpiece surfaces with polyacrylic acid using a high-frequency gas
plasma formed from a gas mixture, wherein the gas mixture is
composed of an inert gas and a first gas formed of biocompatible,
polymerizable carboxy group containing monomers, and a step (c) of
follow-up-coating the pre-coated workpiece surfaces using a second
gas substantially containing acrylic acid monomers.
[0008] The coating further comprises providing a polymeric
workpiece with a hydrophilizing surface coating of polyacrylic
acid, obtainable by a process comprising the steps specified above,
wherein the contact angle of water on the workpiece surface coated
with polyacrylic acid has a value in the range of 2 to less than 10
degrees.
[0009] The workpieces coated with the specified process have a
long-term stable hydrophilic surface with excellent wettability,
which in contact with body tissue results in a good bio
compatibility, whereby irritations of the eye occur less frequently
with accordingly coated contact lenses, and body cells more readily
attach to accordingly coated scaffold substances for Tissue
Engineering.
[0010] If not clearly intended differently from the context, the
words "having", "comprising", "including", "encompassing", "with"
and the like in the specification and the claims as well as their
grammatical modifications are to be understood as comprising as
opposed to exclusive or exhaustive meaning; i.e. in the sense of
"including, but not limited to".
[0011] In preferred embodiments of the process, the biocompatible
polymerizable monomers forming the first gas are selected from
(meth)acrylic acid and (meth)acrylic acid anhydride, whereby in the
high frequency plasma a large proportion of acrylic acid monomers
is generated which attach to the workpiece surface activated in
step (a) of the process forming covalent bonds.
[0012] In other preferred embodiments, the gas used in step (a) of
the process for generating the high-frequency plasma contains the
first gas in an amount corresponding to a partial pressure of less
than one tenth of the partial pressure of the inert gas, so that an
efficient cleaning and activating of the workpiece surfaces is
ensured.
[0013] In order to achieve a stable attachment of the acrylic acid
monomers to the workpiece surface, in preferred embodiments in step
(b) a gas mixture is used in which the partial pressure of the
first gas is at least one fourth of, and maximally twice the
partial pressure of the inert gas.
[0014] With a view to obtaining a dense and stable poly(acrylic
acid) coating, the partial pressure of the inert gas in the second
gas used in step (c) is, in embodiments, less than one tenth of the
partial pressure of the acrylic acid monomer-forming gas.
[0015] In embodiments, Argon is used as the inert gas.
[0016] For an efficient control of the pre-coating process, in
embodiments the coating applied in step (b) is monitored by means
of a layer thickness control device, and the process terminated
upon reaching a layer thickness value selected from the range 50 to
400 .ANG..
[0017] In particularly preferred embodiments, in which contact
angles in the range of 2 to less than 10 degrees are achieved, the
pressure of the inert gas for the high-frequency plasma in step (a)
is set to a value in the range 15 to 60 mTorr (ca. 2 to 8 Pa) and
the pressure of the first gas for the high-frequency plasma in step
(b) to a value in the range 30 to 90 mTorr (ca. 4 to 12 Pa).
[0018] For fixing the acrylic acid polymer coating on the workpiece
surfaces, embodiments further include a step (cb), comprising
throttling the inert gas supply and supplying a second gas
immediately subsequent to step (b), wherein the pressure of the
second gas in step (cb) is less than 0.3 mTorr (ca. 40 mPa).
[0019] In order to promote the attachment to, and cross-linking of
acrylic acid monomers with the pre-coated workpiece surface,
embodiments further comprise a step (bc), carried out immediately
after step (b) or, if executed, step (cb), which further step
comprises a switching-off of the high-frequency plasmas, an
interrupting of the inert gas supply, and a supplying of the second
gas, wherein the pressure of the second gas in step (c) is between
1.5 and 6 Torr (ca. 0.13 to 0.8 kPa).
[0020] In order to improve the bio-compatibility, embodiments
comprise a step (d) subsequent to step (c) of removing water
soluble components from the hydrophilizing layer by means of
rinsing the coated workpiece in hydrophilic solvent, such as e. g.
in isotonic saline solution or, depending on the intended
application of the workpiece, in de-mineralized water.
[0021] In further preferred embodiments, the workpiece comprises,
at least at its surface, a material which is formed mainly or
substantially of a silicone, in particular poly(dimethylsiloxane),
a silicone hydrogel, or a porous bioresorbable polymer such as PLA
or PLGA. The thickness ranges of the workpieces in embodiments
relating to the first case relevant for contact lenses are
preferably between 50 and 300 .mu.m, between 5 and 40 .mu.m, or
between 2 and 12 .mu.m. The thickness of the coating in embodiments
with porous PLA or PLGA is preferably between 5 and 40 nm.
[0022] In embodiments, the workpieces are silicone contact lenses.
The hydrophilizing surface coating of these workpieces is comprised
of a PAA-layer with an average thickness of 5 to 40 .mu.m.
[0023] In other embodiments, the workpieces are a porous matrix of
poly(.alpha.-hydroxycarboxylic acids). The hydrophilizing surface
coating of these workpieces is comprised of a PAA-layer with an
average thickness of 5 to 40 nm.
[0024] Further features of the invention are apparent from the
following description of embodiments in conjunction with the claims
and the drawings. The invention is not limited by the described
embodiments, but determined by the scope of the appended claims. In
particular, the individual features of embodiments according to the
invention may be realized in a different number or combination than
in the examples described below. In the following explanation of
embodiments, reference is made to the appended drawings, which
show:
[0025] FIG. 1 a schematic depiction for illustrating a system for
biocompatibly coating of polymeric biomaterials;
[0026] FIG. 2 a flow diagram for illustrating the essential process
steps for coating polymeric biomaterials with poly(acrylic acid);
and
[0027] FIG. 3 a fluorescence diagram for illustrating the layer
thickness achievable with the process according to FIG. 2.
[0028] The scheme shown in FIG. 1 illustrates important components
of an apparatus 100 for coating polymeric workpieces 90 with a
material rendering their surfaces hydrophilic. The workpieces are
preferably either contact lenses and in this case particularly
those made of a silicone or a silicone hydrogel, or else a
polymeric scaffold, preferably made of PLA (polylactide) or PLGA
(polylactide-co-glycolide), suitable for Tissue Engineering.
[0029] The apparatus 100 comprises an evacuatable recipient 10 with
a device for generating a high-frequency plasma in the interior 15
of the recipient 10. The device for generating a high-frequency
plasma is symbolized in the scheme of FIG. 1 by means of two
electrodes 11 and 12, but is not limited to the use of electrodes.
It should be noted that in FIG. 1, for the sake of clarity and
conciseness, only such components are depicted which are deemed to
be required for understanding the invention. Such components as
e.g. pumps for evacuating the recipient 10, which are required for
operating the apparatus but are irrelevant for understanding the
invention, are deemed present despite not being shown in the
drawing. At least a vacuum or low pressure gauge 13 and a coating
application measuring device 14, such as an oscillating quartz, are
associated with the interior 15 of the recipient 10.
[0030] The coating apparatus 100 further includes an inert gas
reservoir 21 and one or more coating material reservoirs 22 and 23.
Each of the reservoirs or reservoir containers 21, 22 and 23,
respectively, is connected by an associated one of ducts 71, 72 and
73 with the recipient 10 in such a manner that gaseous or vaporized
substances kept in the reservoirs or reservoir containers can be
guided into the interior 15 of the recipient 10. Control valves 41,
42 and 43 arranged in the ducts 71, 72 and 73 enable regulation of
the flow of the respective gas or vapour into the recipient 10. In
the embodiment shown, the control valves may alternatively be used
for venting the reservoirs 21, 22 and 23. In other embodiments,
separate valves and, if desired, separate ducts are employed for
this purpose.
[0031] The apparatus 100 further includes a control 80, which is
adapted for controlling or, if desired, regulating the coating
processes e.g. by means of control leads 61, 62, 63, 64, 65 and
signal leads 66 and 67. Depending on the requirements, the control
can be adapted for a fully automatic or a semi-automatic coating
control. It may be noted that, deviating from German use of the
terms, in this text it is not discriminated between controlling and
regulating. Instead, both terms are used synonymously, i.e. the
term control may comprise returning a control quantity or its
measured value, respectively, in the same manner as the term
regulating may refer to a simple control chain. This also applies
to grammatical variations of these terms. A regulating (partial)
control of the apparatus 100 may be realized e.g. using the output
signals from sensor devices associated with the interior 15. For
example, the valves 41, 42 and 43 may be controlled, using the
vacuum or low pressure gauge 13 in such a manner that in the
interior 15 of the recipient 10 a predetermined constant gas or
vapour pressure with likewise predetermined partial pressures is
maintained. Furthermore, the control device 80 may be adapted to
monitor the building-up of the coating by means of the coating
thickness monitoring device 14 and to terminate same when a desired
coating thickness is reached. In addition, the control 80 is
typically arranged for controlling the high-frequency apparatus 11
and 12 in dependence of the process requirements.
[0032] The flow diagram 200 of FIG. 2 illustrates the important
steps of a process for hydrophilizing workpiece surfaces by coating
with poly(acrylic acid). Preferably, polymeric biomaterials are
used for manufacturing the workpieces 90 or their surface regions,
wherein the term "biomaterial" relates to all materials intended
for contact with biological tissue or body fluids, e.g. in the
course of therapeutic or diagnostic measures.
[0033] Subsequent to the preparation of the workpieces 90 in step
S0, optionally comprising cleaning the workpieces and arranging
same in the recipient 10 as well as subsequently evacuating the
recipient, the workpiece surfaces are initially prepared in step S1
for a subsequent coating.
[0034] To this end, the recipient 10 loaded with the one or more
workpieces is initially evacuated by means of pumps (not shown in
the drawings), preferably to a pressure of maximally 10.sup.-4 mbar
(10 mPa). After reaching the desired vacuum pressure, the interior
15 is purged with an inert gas, preferably Argon, while continually
pumping, wherein the inert gas supply is adjusted to the pumping
speed so that in the interior 15 of the recipient 10 a constant
pressure is maintained. The inert gas 31 is supplied to the
recipient from an inert gas reservoir 21. In embodiments the Argon
gas pressure is about 25 mTorr (ca. 3.3 Pa). After reaching a
stable inert gas pressure in the interior of the recipient 15, the
plasma generator, for example a high-frequency generator, is
switched on, whereby an inert gas plasma is generated which
surrounds the workpieces 90. The plasma cleans the work piece
surfaces by removing substances adsorbed thereon and furthermore
results in an activation of the workpiece surfaces by forming ions
and free radicals beneficial for the subsequent polymerisation
process.
[0035] The cleaning and activating effect of this first step S1 may
be influenced via the frequency of the generator, the power coupled
into the plasma, the exposure time to the plasma, and the type of
the inert gas used for the plasma, as is generally known. The
settings suitable for each individual application may be determined
by the skilled person. In the presently described process, Argon is
preferred as the inert gas, because it allows an activation of the
workpiece surfaces without generating new, undesired compounds.
Naturally, other inert gases may be employed instead, such as
nitrogen, if leading to comparable results. In an exemplary
embodiment, the exposition time to the Argon plasma is about 1
minute or less. After this time, the plasma generator is switched
off and the process continued with the first coating step S2.
[0036] Deviating from the above, the plasma employed for the
pre-treatment of the workpieces may be generated on the basis of a
mixture of the inert gas and a reactive component to be used in a
subsequent pre-coating step, instead of pure Argon. The partial
pressure of the reactive component in the gas mixture should be
less than one tenth than the partial pressure of the inert gas.
[0037] On transitioning from step S1 to step S2 of the process, the
inert gas supply into the interior of the recipient is preferably
maintained or optionally is adjusted so that it assumes a value
suitable for carrying out step S2. For generating the gas mixture,
a coating material gas made up of biocompatible, polymerizable
carboxy group-containing monomers in the vapour phase is admixed to
the inert gas in the recipient 10. The carboxy group-containing
monomers are preferably acrylic acid or an acrylic acid precursor,
such as e.g. (meth)acrylic acid anhydride. The partial pressure
P.sub.eSG of the first coating material gas in some embodiments is
at least one fourth of, and maximally twice the partial pressure
p.sub.IG of the inert gas. More preferably, the partial pressure
ratio p.sub.eSG:p.sub.IG is selected from the range 1:1 to 1:0.5.
For example, the partial pressure of Argon in embodiments of the
process is 30 mTorr (ca. 400 mPa) at a total pressure of the gas
mixture of 45 mTorr (ca. 600 mPa), resulting in a value of the
ratio of the Argon partial pressure p.sub.Ar to the first coating
material partial pressure (reactive component partial pressure)
P.sub.eSG of 2:1. As the reactive component for generating the
first coating material gas, preferably (meth)acrylic acid anhydride
is used, which is vaporized in one of the reservoirs 22 or 23 in
FIG. 1 and is guided to the interior 15 of the recipient 10 via
ducts 72 or 73. The partial pressure of the coating material gas is
adjusted via its inflow, in turn controlled via valves 42 or 43.
Naturally, instead of (meth)acrylic acid anhydride, (meth)acrylic
acid may be used. (Meth)acrylic acid or (meth)acrylic acid
anhydride are provided in the reservoirs 22 or 23 in liquid form,
for example in an amount of 150 ml. In order to prevent or inhibit
polymerization of the acrylic acid or its precursor material,
respectively, same may be doted with Cu(I)-chloride. Furthermore,
the reactive component containers 22 and 23, respectively, after
filling are de-aerated until bubbles n o longer appear in the
reactive component liquid. The vapour pressure of the reactive
components at common ambient temperatures of 22 to 25.degree. C. is
usually sufficient for forming the first coating material gas.
[0038] After adjusting the desired gas mixture and gas mixture
pressure the actual pre-coating process is initiated through
starting the plasma generator, whereby acrylic acid monomers
excited in the plasma attach to the activated workpiece surface
and, in the further course, form a poly(acrylic acid) layer. This
plasma enhanced pre-coating phase is maintained until a desired
coating thickness is reached. The building-up of the coating is
continually monitored by means of the coating deposition measuring
device 14. In principle, coatings with thicknesses of up to 30,000
nm, corresponding to 30 .mu.m, may be deposited, wherein a
respective coating process is terminated once the coating
deposition measuring device 14 indicates the achievement of the
desired coating thickness within a given tolerance of e.g. 50 to
400 .ANG.. The thickness of the hydrophilic coating to be deposited
in the pre-coating process depends on the particular application
and in the case of scaffold substances for Tissue Engineering
usually is in the range of 30 to 50 nm. For hydrophilizing contact
lenses pre-coatings with for example thicknesses in the range of
about 5 to 40 nm have proven useful. According to the application
and therefore also the required coating thickness, the pre-coating
phase may take between 10 and 80 or even 120 minutes. The gas
supplies are preferably not varied during the plasma coating. In a
first variant of the process, the pre-coating process is terminated
by switching off the plasma generator.
[0039] Subsequent to the first variant of the pre-coating step S2
described above, a first variant of the follow-up-coating step S3
follows in which, after switching off the plasma generator,
initially the inert gas supply is interrupted and the pre-coated
workpiece surface is exposed to, if possible, the full vapour
pressure of a reactive component formed by water-free acrylic acid.
The vapour pressure of the reactive component should not be below 5
Torr (ca. 667 Pa). Slightly cooling or warming the reactive
component in the reservoir 22 or 23 may be suitable to adjust the
pressure. The introduction of the reactive component into the
recipient 10 at full vapour pressure provides the reactive gas in
large amounts, which reacts with reactive centers present on the
pre-coated surface and provides a relatively thick poly(acrylic
acid) layer (PAA-layer), which may be crystalline.
[0040] In FIG. 3 a measurement diagram is shown, from which it may
be derived that a PAA-layer produced as described above has a
thickness of about 10 .mu.m. For this measurement, the hydrophilic
PAA-layer was stained with Rhodamin 6G as a fluorescence dye and
the fluorescence was measured in dependence of depth by means of
confocal microscopy. as may be gathered from the right portion of
the fluorescence tracks, the hydrophilic layer extends
significantly into the depth of the workpiece. The contact lens
measured in FIG. 3 at the site of the measurement has a thickness
of 117.5 .mu.m. The resolution of the measurement is 0.6 .mu.m.
From the obtained data, it may be derived that a coating thickness
on the surface of ca. 10.+-.0.6 .mu.m (region between the vertical
lines) and a penetration depth per side of ca. 15 to 20.+-.0.6
.mu.m was present. In the described variant, the process is
therefore particularly suitable for the application to silicone
contact lenses, for which hydrophilicity of the surface, durability
of the coating as well as the optical properties thereof are
equally important.
[0041] In a second variant of the process, the plasma generator is
not switched off at the end of the pre-coating step S2 and is
therefore still in operation at the time of transitioning to the
follow-up coating step S3. In this variant, the Argon supply is
almost or entirely stopped and the supply of the reactive gas, i.
e. the acrylic acid, is reduced so much that, with the
high-frequency generation maintained and continuously evacuating
the recipient 10, a pressure equilibrium in the range of less than
0.3 mTorr (ca. 40 mPa) is achieved. In an exemplary embodiment, the
pressure is adjusted to a value of less than 0.1 mTorr (ca. 13
mPa). This follow-up-coating phase is maintained for 5 to 15
minutes and with porous resorbable scaffold substances for Tissue
Engineering results in workpiece surfaces having particularly low
contact angles for water and excellent cell adhesion rates of e. g.
above 90% or above 95%. The described second variant of the process
is therefore particularly suitable for the manufacture of coated
scaffold substances, which are to be employed for the infiltration
of cells in the course of Tissue Engineering.
[0042] After terminating the process in step S4 the coated
workpieces 90 may be removed from the recipient a may optionally
subjected to a quality check.
[0043] the process described above allows for a durable
hydrophilization of polymeric biomaterial surfaces, which have an
excellent wetting with water and, thereby, a high
biocompatibility.
* * * * *