U.S. patent application number 10/733258 was filed with the patent office on 2004-07-01 for machine and method for producing porous membranes for medical use.
This patent application is currently assigned to Integrated Biomaterial & Cell Technologies S.r.I.. Invention is credited to Soldani, Giorgio.
Application Number | 20040123435 10/733258 |
Document ID | / |
Family ID | 32338248 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040123435 |
Kind Code |
A1 |
Soldani, Giorgio |
July 1, 2004 |
Machine and method for producing porous membranes for medical
use
Abstract
The machine (1) for producing porous membranes (2) for medical
use comprises a plurality of reserves (25a, 25b, 25c, 26a, 26b,
26c) of components (18a, 18b, 18c, 19a, 19b, 19c) which constitute
fluid substances, first and second guns (16, 17) supplied from the
reserves (25a, 25b, 25c, 26a, 26b, 26c) for spraying the fluid
substances onto an element (37) on which the substances are
deposited and build up, the element (37) and the guns (16, 17)
being mobile relative to one another for substantially even
distribution of the fluid substances designed to form the membrane
(2).
Inventors: |
Soldani, Giorgio; (Pisa,
IT) |
Correspondence
Address: |
ARENT FOX KINTNER PLOTKIN & KAHN, PLLC
Suite 600
1050 Connecticut Avenue, N.W.
Washington
DC
20036-5339
US
|
Assignee: |
Integrated Biomaterial & Cell
Technologies S.r.I.
|
Family ID: |
32338248 |
Appl. No.: |
10/733258 |
Filed: |
December 12, 2003 |
Current U.S.
Class: |
28/100 |
Current CPC
Class: |
B29K 2105/206 20130101;
B29C 31/10 20130101; B01D 69/04 20130101; B01D 2323/42 20130101;
B29K 2105/06 20130101; B29C 41/08 20130101; B29C 41/52 20130101;
B01D 67/0004 20130101; B29C 41/365 20130101; B29C 41/20
20130101 |
Class at
Publication: |
028/100 |
International
Class: |
A44B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2002 |
EP |
02425778.4 |
Claims
What is claimed is:
1. A machine for producing porous membranes (2) for medical use,
starting with fluid substances consisting of mixtures (18, 19) of
two or more components (18a, 18b, 18c, 19a, 19b, 19c), the machine
being of the type comprising: reserves (25a, 25b, 25c, 26a, 26b,
26c) of said components (18a, 18b, 18c, 19a, 19b, 19c), spray means
(36) for the fluid substances, connected to the reserves (25a, 25b,
25c, 26a, 26b, 26c), a support (11) constituting an element (37) on
which the fluid substances sprayed by the means (36) are deposited
and build up, the element (37) and the spray means (36) being
mobile relative to one another for substantially even distribution
of the fluid substances designed to form the membrane (2), the
machine further comprising, upstream of the spray means (36), mixer
means (23, 24) for mixing together the components (18a, 18b, 18c,
19a, 19b, 19c) which form the fluid substances, in the desired
relative mixing quantities, these relative quantities providing the
membrane (2) with given chemico-physical properties.
2. The machine according to claim 1, further comprising a central
control unit (35) designed to act upon the mixer means (23, 24) to
alter the relative quantities for mixture of the components (18a,
18b, 18c, 19a, 19b, 19c) of the fluid substances, according to the
desired values set on the control unit (35).
3. The machine according to claim 1 or 2, wherein the spray means
(36) comprise at least a first nozzle (16a) and a second nozzle
(17a) for spraying a first mixture (18) and a second mixture (19)
at the support (11).
4. The machine according to claim 3, further comprising at least
one pump (21, 22) for supplying the fluid substances to the nozzles
(16a, 17a).
5. The machine according to claim 3 or 4, further comprising at
least one source (27) of pressurized gas for activating the nozzles
(16a, 17a).
6. The machine according to any of the foregoing claims from 1 to
5, wherein the support (11) comprises a cylindrical element (12,
12c) for producing tubular porous membranes (2), the cylindrical
element (12, 12c) being designed to turn about an axis of rotation
(A).
7. The machine according to any of the foregoing claims from 1 to
5, wherein the element (37) on which the fluid substances sprayed
are deposited and build up is a stent (40) designed to be covered
by the substances, the stent (40) being supported by the machine
using a wire (41) passing inside it and made to rotate about an
axis of rotation (A).
8. The machine according to claim 7, further comprising a heating
element (46) designed to heat a given zone (48) close to the stent
(40).
9. The machine according to claim 6, wherein the spray means (36)
comprise a first carriage (13) supporting the nozzles (16a, 17a),
the first carriage (13) and the cylindrical element (12, 12c) being
mobile relative to one another in a direction (D) substantially
parallel with the axis of rotation (A) of the cylindrical element
(12, 12c).
10. The machine according to claim 9, wherein the first carriage
(13) is driven by drive means so that it slides in the direction
(D) substantially parallel with the axis of rotation (A) of the
cylindrical element (12, 12c).
11. The machine according to any of the foregoing claims from 6 to
10, further comprising a second carriage (29) supporting an
extractor hood (31), the second carriage (29) sliding in the
direction (D) substantially parallel with the axis of rotation (A)
and the extractor hood (31) being positioned over the nozzles (16a,
17a).
12. The machine according to any of the foregoing claims from 1 to
11, wherein one of the mixtures (18, 19) comprises a polymer and
the other mixture (18, 19) comprises a non-solvent for the
polymer.
13. The machine according to any of the foregoing claims from 1 to
12, further comprising means (43) for the insertion of membrane (2)
stiffening elements (45) during membrane (2) formation.
14. The machine according to claim 13, wherein the stiffening
elements (45) comprise a filament (42) designed for insertion in
the membrane (2).
15. The machine according to claim 13, wherein the stiffening
elements (45) comprise a tubular mesh (44) designed for insertion
in the membrane (2).
16. A method for producing porous membranes (2) for medical use
starting with fluid substances consisting of mixtures (18, 19) of
two or more components (18a, 18b, 18c, 19a, 19b, 19c), comprising
the steps of: supplying the fluid substances to spray means (36),
depositing and building up the fluid substances sprayed by the
spray means (36) on a supporting means (11), providing drive means
for the spray means (36) and the supporting means (11) for
substantially even distribution of the substances designed to form
the membrane (2), wherein the supply step comprises the further
step of changing the relative quantities for mixture of the
components (18a, 18b, 18c, 19a, 19b, 19c), according to the desired
values, relative to the chemico-physical properties required of the
membrane (2).
17. The method according to claim 16, wherein the step of changing
the relative quantities for mixture of the components (18a, 18b,
18c, 19a, 19b, 19c) occurs substantially instantaneously according
to a stepped function.
18. The method according to claim 16, wherein the step of changing
the relative quantities for mixture of the components (18a, 18b,
18c, 19a, 19b, 19c) occurs continuously according to a gradual
function.
19. The method according to any of the foregoing claims from 16 to
18, wherein the chemico-physical properties comprise the level of
porosity of the membrane (2).
20. The method according to any of the foregoing claims from 16 to
19, further comprising the step of inserting stiffening elements
(45) in the membrane (2) during membrane (2) formation.
21. The method according to any of the foregoing claims from 16 to
19, further comprising the step of heating a zone (48) close to a
support (11) forming an element (37) on which the fluid substances
sprayed are deposited and build up.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a machine and method for
producing porous membranes for medical use.
[0002] In particular, the present invention relates to a machine
and method for producing biocompatible and heamocompatible
membranes designed to constitute vascular prostheses and artificial
tissues for medical use.
[0003] The prior art describes many techniques for the production,
using polymers, of small-diameter porous or filamentous tubular
tissues.
[0004] In addition to the now consolidated production techniques
using extrusion, a spray method for producing membranes is known,
by which they are obtained, for example, from thermodynamically
unstable polymeric solutions. Specifically, the unstable solution
is generated with the addition of a non-solvent to a dilute
polymeric solution and the membranes are obtained with spray
deposition, using a single spray means, or with simultaneous but
separate spray deposition of the unstable polymeric and non-solvent
solution by separate spray means, on a supporting element designed
to define the shape of the membrane.
[0005] The method described above allows the production, for
example, of small-diameter vascular prostheses or flat membranes
obtained by cutting tubular membranes with a larger diameter
longitudinally.
[0006] The vascular prostheses or flat membranes, hereinafter
generally referred to as porous membranes, obtained with the
above-mentioned techniques, although having indisputable positive
aspects, are not free of disadvantages.
[0007] The main disadvantage consists of the fact that the
chemico-physical properties of the porous membranes obtained with
the spray method, particularly the porosity of the membrane
structure, are difficult to control.
[0008] Generally speaking, with the known methods, it is difficult
to obtain membranes able to simultaneously fulfil
haemocompatibility and biocompatibility requirements and provide
adequate mechanical strength.
SUMMARY OF THE INVENTION
[0009] Therefore, the aim of the present invention is to provide a
machine for producing porous membranes which are free of the
above-mentioned disadvantage and, at the same time, are practical
for use and simple and economical to produce.
[0010] Accordingly the present invention provides a machine for
producing porous membranes for medical use as described in claim
1.
[0011] Another aim of the present invention is to provide a method
for producing membranes for medical use, in particular tubular
membranes, which can be used as prostheses, especially vascular
prostheses, and more specifically small-diameter vascular
prostheses, the method being simple and flexible to implement.
[0012] Accordingly the present invention also provides a method for
producing porous membranes for medical use as described in claim
16.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The technical features of the present invention, in
accordance with the above-mentioned aims, are set out in the claims
herein and the advantages more clearly illustrated in the detailed
description which follows, with reference to the accompanying
drawings, which illustrate a preferred embodiment of the invention
without limiting the scope of the inventive concept, and in
which:
[0014] FIG. 1 is a schematic illustration of a preferred embodiment
of a machine for producing porous membranes, made in accordance
with the present invention;
[0015] FIG. 2 is a top perspective view of a machine for producing
membranes, made in accordance with the present invention;
[0016] FIGS. 3, 4, 5 and 6 are front elevation views of a portion
of the machine illustrated in FIG. 2 in as many different operating
configurations;
[0017] FIGS. 7, 8 and 9 are top plan views of a portion of the
machine illustrated in FIGS. 1 and 2 in as many different operating
configurations;
[0018] FIG. 10 is an enlarged cross-section of the detail P
illustrated in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] With reference to FIG. 2, the numeral 1 indicates as a whole
a portion of a machine for producing porous membranes 2 made in
accordance with the present invention.
[0020] The machine 1 comprises a frame 3 and a central body 4
extending longitudinally in a direction D.
[0021] The central body 4 has a first and a second spindle 5, 6
which are coaxial with one another, driven in synchronized rotation
about an axis A parallel with the direction D, by respective
toothed belts 7, 8.
[0022] The toothed belts 7, 8 are in turn driven by toothed
pulleys, of which FIG. 2 fully illustrates only one, labeled 9,
keyed to opposite ends of a shaft 10. The shaft 10 is turned by
drive means of the known type which are not illustrated or
described in any further detail.
[0023] The shaft 10 has an axis of rotation B parallel with the
above-mentioned axis A of the spindles 5, 6.
[0024] Each spindle 5, 6 supports one end of a supporting element
11. In FIG. 2 the supporting element 11 consists of a cylindrical
body 12 with a small diameter.
[0025] At the side of the central body 4, the machine 1 comprises a
first carriage 13 which slides longitudinally in the direction D,
on guide parts 14. A threaded rod 15 engages as it turns with the
carriage 13, to drive the carriage in the direction D. The threaded
rod 15 is turned by drive means of the known type and not
illustrated.
[0026] With reference to FIGS. 1 and 2, the first carriage 13
comprises first and second guns 16, 17 with nozzles 16a, 17a
designed to spray fluid substances, respectively consisting of
first and second mixtures 18, 19.
[0027] The mixtures 18 and 19 are supplied to the guns 16, 17
through pipes 20 by pumps 21, 22.
[0028] The mixtures 18, 19 are formed at and by mixer parts 23, 24
to which a plurality of stored reserves of components designed to
form the above-mentioned mixtures 18, 19 are fluidly connected.
[0029] In particular, for example FIG. 1 illustrates three reserves
25a, 25b, 25c of components 18a, 18b, 18c for the first mixture 18
and three reserves 26a, 26b, 26c of components 19a, 19b, 19c for
the second mixture 19.
[0030] The machine 1 also comprises a source 27 of pressurized gas
supplied to the guns 16, 17 by pipes 28 to activate the nozzles
16a, 17a for spray emission of the mixtures 18, 19.
[0031] The nozzles 16a, 17a of the two guns 16, 17 are angled in
such a way that they substantially converge on the same point of
the cylindrical body 12.
[0032] With reference to FIG. 2, on the side of the cylindrical
body 12 opposite the first carriage 13, the machine 1 comprises a
second carriage 29 which also slides longitudinally in the
direction D on respective guide parts 30 and is driven by a
threaded rod 15.
[0033] The second carriage 29 is covered by an extractor hood 31,
one of whose intakes 32 is positioned over the guns 16, 17.
[0034] As shown in FIG. 1, the hood 31 is connected, by a manifold
schematically illustrated with a line 33, to a suction source, also
schematically illustrated with a block 34.
[0035] Again with reference to FIG. 1, the machine 1 also comprises
a central control unit 35 designed to act on the above-mentioned
mixer parts 23, 24 as well as the guns 16, 17 and on the drive
means of the spindles 5, 6 and carriages 13, 29.
[0036] The guns 16, 17, together with the nozzles 16a, 17a, the
source 27 of pressurized gas and the pumps 21, 22 as a whole
define, for the machine 1, means 36 for spraying the mixtures 18,
19.
[0037] In practice, as illustrated in FIG. 2, the cylindrical body
12 is mounted on the central body 4 of the machine 1, with its ends
12a, 12b fixed to the respective spindles 5, 6.
[0038] Through the above-mentioned drive means, which are not
illustrated, by means of the shaft 10 and belts 7, 8, the
cylindrical body 12 which forms the supporting element 11 is turned
about its axis A.
[0039] Starting with a first limit position of the first carriage
13, illustrated in FIG. 2, the first nozzle 16a is activated by a
flow of pressurized gas from the source 27 through the pipe 28. The
pressurized gas, in accordance with known methods which are not
described in any further detail, causes the spray emission of the
first mixture 18 from the nozzle 16a, creating a first jet 16b. The
first mixture is supplied to the nozzle 16a by the first pump 21
through the pipe 20.
[0040] The first pump 21 sends the first mixture 18 to the first
nozzle 16a, drawing it from the first mixer 23 to which the three
reserves 25a, 25b, 25c of the components 18a, 18b, 18c are
connected.
[0041] Similarly to the above description with reference to the
first nozzle 16a, and substantially simultaneously with this, the
second nozzle 17a is also activated by a flow of pressurized gas
from the source 27, through the pipe 28. The pressurized gas causes
the spray emission of the second mixture 19 from the nozzle 17a,
creating a second jet 17b. The second mixture 19 is supplied to the
nozzle 17a by the second pump 22 through the pipe 20.
[0042] The second pump 22 sends the second mixture 19 to the second
nozzle 17a, picking it up from the second mixer 24, to which the
three reserves 26a, 26b, 26c of the components 19a, 19b, 19c are
connected.
[0043] Again starting from the limit position illustrated in FIG.
2, the first carriage 13 begins to move, driven by the rotation of
the threaded rod 15 which as it turns engages with the carriage 13,
in the direction D, as indicated by the arrow F1. At the same time,
the cylindrical body 12 which constitutes the supporting element 11
is turned by the spindles 5, 6 about the axis A.
[0044] Similarly to the above description, the second carriage 29
begins to move, in the direction D as indicated by the arrow F1,
driven by the rotation of the threaded rod 15 which as it turns
engages with the carriage 29.
[0045] The extractor hood 31, integral with the second carriage 29
also moves in the direction D as indicated by the arrow F1,
substantially synchronized with the first carriage 13 and remains
over the nozzles 16a, 17a. The extractor action of the hood 31 is
mainly intended to promote the regular emission of the jets 16b,
17b of the mixtures 18, 19 directed onto the supporting element
11.
[0046] The above-mentioned movements, simultaneously with the
spraying action of the nozzles 16a, 17a, allows the fluid
substances consisting of the mixtures 18, 19 to be deposited on the
supporting element 11, the latter therefore constituting an element
37 on which the fluid substances are deposited and build up.
[0047] While the supporting element 11 carries on rotating about
its own axis A continuously, the movement of the carriages in the
direction D continues with an alternating motion. That is to say,
when a second, opposite limit position, not illustrated and defined
by the desired longitudinal dimensions for the membrane 2 being
formed is reached, the direction of carriage 13, 29 movement is
inverted and the movement continues in the direction indicated by
the arrow F2.
[0048] The repetition in succession of numerous cycles of
alternating carriage 13, 29 movement allows a given amount of the
mixtures 18, 19 to be deposited, said amount designed to form the
body of the membrane 2.
[0049] In other words, according to the desired thickness of the
membrane 2 and considering the mixture fluid flow rate of nozzles
16b, 17b, the number of alternating motion feed cycles for the
carriages 13, 29 is established.
[0050] A first set of such feed cycles is performed by the machine
1 with the mixtures 18, 19 having respective first compositions
given by particular relative quantities for mixing of the
components 18a, 18b, 18c, 19a, 19b, 19c stored in the reserves 25a,
25b, 25c, 26a, 26b, 26c.
[0051] The values required of these first compositions are set on
the central control unit 35 which operates directly on the mixer
parts 23, 24 in order to make up the first compositions.
[0052] As illustrated in FIG. 10, the mixtures 18, 19 in their
first configurations form a first layer 38 of the porous membrane
2, this first layer 38 having predetermined chemico-physical
properties.
[0053] When executing the commands set on it, the central control
unit 35 therefore acts on the mixer parts 23, 24 to change the
relative quantities of the components 18a, 18b, 18c, 19a, 19b, 19c
stored in the reserves 25a, 25b, 25c, 26a, 26b, 26c and to create
the second compositions of the mixtures 18, 19.
[0054] The machine 1 performs a second set of cycles with the
mixtures 18, 19 with the second compositions.
[0055] As they are deposited on the first layer 38, the mixtures 18
and 19, in their second compositions, create a second layer 39 of
the porous membrane 2, this second layer 39 having predetermined
chemico-physical properties which are different to those of the
first layer 38 below it.
[0056] In particular, as illustrated in FIG. 10, these
chemico-physical properties include the porosity of the membrane 2
which, for example with reference to tubular membranes for vascular
prostheses, advantageously involves two different layers, the
first, internal layer 38 in contact with the hematic fluid and more
porous, and the second, external layer 39, more compact and with
greater mechanical strength.
[0057] Advantageously, the mixers 23, 24, not illustrated in
detail, are of the solenoid valve type, programmable and allow
sequential valve opening so that the nozzles 16a, 17a can be
supplied with predetermined quantities of the components 18a, 18b,
18c in the reserves 25a, 25b, 25c and, at the same time, the
components 19a, 19b, 19c in the reserves 26a, 26b, 26c.
[0058] As illustrated in FIG. 3, the element 37 on which the
substances are deposited and build up is the cylindrical body 12
described above with reference to FIG. 2, designed for producing
tubular porous membranes 2 suitable for use as vascular prostheses
even with very small diameters. The ends of the cylindrical body
12, not illustrated, are connected to the machine 1 spindles 5, 6
to turn about its axis A.
[0059] With reference to FIG. 4, the element 37 on which the
substances are deposited and build up consists of a cylindrical
drum 12c with a diameter larger than that of the above-mentioned
cylindrical body 12. Use of the drum 12c as an element 37 on which
the substances are deposited and build up is intended to produce
flat porous membranes obtained by cutting tubular membranes 2
produced with the above-mentioned method longitudinally.
[0060] With reference to FIG. 5, the element 37 on which the
sprayed fluid substances are deposited and build up consists of a
stent 40. The stent 40 is a tubular element, made of metal or
plastic for insertion, for example, in a blood vessel to hold it
open and prevent constriction or pressure from the outside. The
stent 40 is supported by a fine supporting wire 41, advantageously
made of polytetrafluoroethylene, which passes inside it and whose
opposite ends, not illustrated in the drawing, are connected to the
machine 1 spindles 5, 6 to turn about its axis A. As it turns about
the axis A, the wire 41 causes the stent 40 to rotate.
[0061] During normal machine 1 operation, the stent 40 is hit by
one or both of the jets 16b, 17b from the nozzles 16, 17 and, by
means of the above-mentioned technique, a dense membrane 2 is
formed on its surface, where the term dense refers to a membrane 2
whose porosity is very low, that is to say, which is substantially
closed and impermeable. Since stents are tubular elements with gaps
in the surface, the fluid substances sprayed can advantageously be
deposited evenly on both the outer surface and in the inner tubular
face, passing through the gaps in the outer surface.
[0062] FIG. 6 illustrates a preferred embodiment of the
configuration illustrated in FIG. 5. In this improved
configuration, the machine 1 comprises a heating element 46,
schematically illustrated in the drawing. This element 46 is
located below the stent 40 which is mounted on the supporting wire
41. The heating element 46 is regulated by a temperature control
unit 47 and powered by known means, not illustrated or described in
further detail, for heating a zone 48 close to the stent 40.
[0063] Advantageously, thanks to the heat, when the particles of
fluid substances sprayed by the nozzles 16a, 17a make contact with
the stent 40, they form a substantially smooth and even layer on
its surface. Moreover, the higher temperature created in the zone
48 by the presence of the heating element 46 allows the solvents
present in the fluids sprayed to rapidly evaporate, increasing
adhesion to the stent 40 by the membrane 2 as it is formed.
[0064] FIG. 7 illustrates an alternative embodiment of the machine
1 disclosed. This alternative embodiment allows the above-mentioned
procedure for spray depositing the fluid substances to be performed
at the same time as a filament 42 of a suitable strengthening
material (polyester, polyurethane, silicone, etc.) is wound around
the supporting element 11. In particular, the filament 42 is
incorporated in the porous membrane 2 being formed on the rotating
cylindrical body 12. The filament 42 is wound in a spiral, with a
predetermined pitch, by the respective movements of the rotating
support 12 and of a rotary dispenser element 43 for the filament
42. The element 43 can slide in the direction D, driven by drive
means which are not illustrated.
[0065] FIGS. 8 and 9 illustrate yet another embodiment of the
machine 1 disclosed. In this embodiment, once the nozzles 16 and 17
have deposited a predetermined quantity of the fluid substances on
the cylindrical body 12, providing a given porous membrane 2
thickness, a tubular strengthening mesh 44 is inserted on the
cylindrical body 12. The mesh 44, advantageously made of polyester,
is then covered with another material, which may or may not be
porous, again deposited with the spray technique described above.
Advantageously, the tubular mesh 44 has substantially wide links,
allowing substantial continuity between the material
spray-deposited before insertion of the mesh 44 and that deposited
over the mesh 44.
[0066] Therefore, the mesh 44 is incorporated between two polymeric
layers.
[0067] Where special needs require it, the tubular mesh 44 can also
only be coated on its outer wall, by inserting the mesh 44 directly
on the cylindrical body 12 without previously spray-depositing any
material on the body 12, as described above.
[0068] The strengthening filament 42 and the tubular mesh 44
together constitute membrane 2 stiffening elements 45.
[0069] The operations described above with reference to FIGS. 7, 8
and 9 may also be performed with large deposit and build up
elements 37, such as the cylindrical drum 12c, to obtain
strengthened flat porous membranes 2.
[0070] Advantageously, depending on the required membrane 2
composition, the control unit 35 acts upon the mixer parts 23, 24,
altering the relative quantities of components 18a, 18b, 18c, 19a,
19b, 19c, for example, in a substantially instantaneous way, with a
stepped function, or continuously with a gradual function.
[0071] Advantageously, but without limiting the scope of the
present invention, in a preferred embodiment of the present
invention the first mixture 18 comprises a polymer and the second
mixture 19 comprises a non-solvent for the polymer.
[0072] The invention described can be subject to modifications and
variations without thereby departing from the scope of the
inventive concept. Moreover, all the details of the invention may
be substituted by technically equivalent elements.
* * * * *