U.S. patent application number 14/148044 was filed with the patent office on 2017-04-27 for gels.
This patent application is currently assigned to Aortech International plc. The applicant listed for this patent is Aortech International plc. Invention is credited to Mark Bown, Mansour Mehrabi, Ramasri Mudumba, Ajay D. Padsalgikar, Sriram Venkataramani.
Application Number | 20170114187 14/148044 |
Document ID | / |
Family ID | 38624454 |
Filed Date | 2017-04-27 |
United States Patent
Application |
20170114187 |
Kind Code |
A9 |
Mehrabi; Mansour ; et
al. |
April 27, 2017 |
GELS
Abstract
The present invention relates to biostable gel comprising: (a)
at least one silicon-containing polyol, polyamine, polyepoxy or
polyisocyanate having 1 or more functional groups and a molecular
weight of at least 20,000 which is cured in the presence of: (b) at
least one diol, diamine or diisocyanate having a molecular weight
of less than 10,000; and/or (c) an initiator, processes for their
preparation and their use in the manufacture and repair of
biomaterials and medical devices, articles or implants, in
particular the manufacture of a soft tissue implant such as breast
implants and the repair of orthopaedic joints such as spinal
discs.
Inventors: |
Mehrabi; Mansour; (Victoria,
AU) ; Venkataramani; Sriram; (Victoria, AU) ;
Bown; Mark; (Notting Hill, AU) ; Padsalgikar; Ajay
D.; (Plymouth, MN) ; Mudumba; Ramasri;
(Victoria, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Aortech International plc |
Glasgow |
|
GB |
|
|
Assignee: |
Aortech International plc
Glasgow
GB
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20140323676 A1 |
October 30, 2014 |
|
|
Family ID: |
38624454 |
Appl. No.: |
14/148044 |
Filed: |
January 6, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12226508 |
Jun 22, 2009 |
8623986 |
|
|
PCT/AU2007/000511 |
Apr 19, 2007 |
|
|
|
14148044 |
|
|
|
|
60802080 |
May 18, 2006 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 2400/06 20130101;
A61L 27/52 20130101; A61K 31/695 20130101; C08G 18/61 20130101;
C08G 77/26 20130101; A61L 27/18 20130101; C08G 18/8108 20130101;
C08L 83/04 20130101; C08G 2220/00 20130101; A61L 27/18 20130101;
C08G 77/16 20130101; C08G 77/388 20130101; C08G 77/18 20130101;
C08G 18/10 20130101; C08G 77/46 20130101; C08G 77/20 20130101; C08G
77/38 20130101; C08G 18/10 20130101; C08G 77/14 20130101; C08G
18/61 20130101; C08L 83/04 20130101 |
International
Class: |
C08G 77/38 20060101
C08G077/38; C08G 77/388 20060101 C08G077/388 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 20, 2006 |
AU |
2006902072 |
Claims
1. (canceled)
2. A silicon-containing polyol, polyamine, polyepoxy or
polyisocyanate of formula (I) or (II): ##STR00016## in which
R.sub.a and R.sub.b are both absent or independently selected from
C.sub.1-6alkyl, OH, C.sub.1-6alkoxy, (CH.sub.2).sub.3OR.sub.1 and
Si(R.sub.7)(R.sub.8)(CH.sub.2).sub.3OR.sub.2; R.sub.1 and R.sub.2
are independently selected from C.sub.1-6 alkylene optionally
substituted with OH, NCO, expoxy or NR'R'' in which R' and R'' are
independently selected from H, CO.sub.2H and C.sub.1-6 alkyl;
R.sub.3 to R.sub.8 are independently selected from vinyl, C.sub.1-6
alkyl and C.sub.1-6 alkylene which may be optionally interrupted by
O and optionally substituted with OH, NCO, epoxy, C.sub.1-6alkyl
acrylate or NR'R'' in which R' and R'' are as defined above;
R.sub.9 is C.sub.1-4 alkyl; R.sub.10 is optionally substituted
C.sub.1-4 alkyl or ##STR00017## in which R.sub.1 and R.sub.9 are as
defined above; x is 100 to 1000; y is 0 to 200; and n is 30 to
500.
3. A silicon-containing polyol, polyamine, polyepoxy or
polyisocyanate of formula (I) having the formula: ##STR00018##
##STR00019## ##STR00020## in which x and y in the compounds of
formulae (Ia), (Ib), (Ic), (Ig), (Ih) and (Ij) are as defined in
claim 8.
4. A silicon-containing polyol, of formula (II) having the formula:
##STR00021##
Description
RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/226,508, filed Jun. 22, 2009, which
application is a nationalization under 35 U.S.C. 371 of
PCT/AU2007/000511, filed Apr. 19, 2007 and published as WO
2007/121513 A1, on Nov. 1, 2007, which claimed priority under 35
U.S.C. 119 to Australian Application No. 2006902072, filed Apr. 20,
2006; and which claimed priority under 35 U.S.C. 119(e) to U.S.
Provisional Patent Application Ser. No. 60/802,080, filed May 18,
2006; which applications and publication are incorporated herein by
reference and made a part hereof in their entirety.
FIELD
[0002] The present invention relates to silicon-containing
biostable gels and processes for their preparation. The gels
possess properties which make them useful in the manufacture and
repair of biomaterials and medical devices, articles or implants,
in particular the manufacture of soft tissue implants such as
breast implants and the repair of orthopaedic joints such as spinal
discs.
BACKGROUND
[0003] Polymer gels are semi-solid systems that respond in a liquid
like fashion under certain circumstances but their molecules do not
have motion that is independent of each other, hence they behave
like solids in other circumstances.
[0004] Gels can be synthesised as physical gels where a
cross-linked network is swelled by a non reactive liquid. Without
the presence of this swelling medium the cross-linked network would
be a solid. Silicone gels currently used in breast implants are
physical gels where a cross-linked polydimethylsiloxane (PDMS)
system is swollen by a non reactive, low molecular weight PDMS.
These gels are inherently prone to leakage of the low molecular
weight liquid PDMS and contain heavy metal catalysts such as
platinum and tin which can leach out of the implant in an in-vivo
situation.
[0005] Hydrogels are other examples of physical gels, where
hydrophilic groups in the cross-linked network can attract water
molecules and are swollen by them. In a physical gel the parts by
weight of the swelling medium can be as high as 90%. This swelling
medium can be extracted out of the gel by most solvents and
biological fluids.
[0006] There is a need for a gel that mimics the behaviour of a
PDMS-based physical gel, but is chemically formulated so as to
avoid the complications of a physical gel.
SUMMARY
[0007] International Patent Publication No. WO 2006/034547
describes silicon-containing biostable gels. We have now found that
increasing the molecular weight of the silicon-containing component
of the gels specifically disclosed in WO 2006/034547 allows curing
to occur at room temperature. The use of higher molecular weight
components also increases the stoichiometry of curing which assists
in reducing the amount of solvent extractables which are free to
migrate from the gel.
[0008] According to the present invention there is provided a
biostable gel comprising: [0009] (a) at least one
silicon-containing polyol, polyamine, polyepoxy or polyisocyanate
having 1 or more functional groups and a molecular weight of at
least 20,000 which is cured in the presence of: [0010] (b) at least
one diol, diamine or diisocyanate having a molecular weight of less
than 10,000; and/or [0011] (c) an initiator.
[0012] The amount of polyol, polyamine, polyepoxy or polyisocyanate
(a) present in the gel is preferably 80 to 100% and the amount of
diol, diamine or diisocyanate (b) is preferably 0 to 20% based on
the total weight of the gel.
[0013] The molecular weight of diol, diamine or diisocyanate is
preferably 500 to 10000, more preferably 2000 to 6000.
[0014] The gel preferably has an average functionality of 1 to 5,
more preferably 2.05 to 3.5, most preferably 2.1 to 3.25.
[0015] The present invention also provides a process for preparing
the biostable gel defined above which comprises the steps of:
[0016] (i) mixing components (a) and (b) or (c) as defined
above.
[0017] In another embodiment, the process for preparing the
biostable gel defined above comprises the steps of: [0018] (i)
preparing a prepolymer having terminally reactive polyisocyanate
groups from component (b) defined above; and [0019] (ii) mixing the
prepolymer of step (i) with component (b) as defined above.
[0020] Some of the silicon-containing polyols, polyamines,
polyepoxys or polyisocyanates (a) defined above are novel and form
part of the invention.
[0021] Further according to the present invention there is provided
a silicon-containing polyol, polyamine, polyepoxy or polyisocyanate
of formula (I) or (II):
##STR00001##
[0022] in which
[0023] R.sub.a and R.sub.b are both absent or independently
selected from C.sub.1-6alkyl, OH, C.sub.1-6alkoxy,
(CH.sub.2).sub.3OR.sub.1 and
Si(R.sub.7)(R.sub.8)(CH.sub.2).sub.3OR.sub.2;
[0024] R.sub.1 and R.sub.2 are independently selected from
C.sub.1-6 alkylene optionally substituted with OH, NCO, expoxy or
NR'R'' in which R' and R'' are independently selected from H,
CO.sub.2H and C.sub.1-6 alkyl;
[0025] R.sub.3 to R.sub.8 are independently selected from vinyl,
C.sub.1-6 alkyl and C.sub.1-6 alkylene which may be optionally
interrupted by O and optionally substituted with OH, NCO, epoxy,
C.sub.1-6alkyl acrylate or NR'R'' in which R' and R'' are as
defined above;
[0026] R.sub.9 is C.sub.1-4 alkyl;
[0027] R.sub.10 is optionally substituted C.sub.1-4 alkyl or
##STR00002##
in which R.sub.1 and R.sub.9 are as defined above;
[0028] x is 100 to 1000, preferably 300 to 600;
[0029] y is 0 to 200, preferably 0 to 10; and
[0030] n is 30 to 500, preferably 50 to 200.
[0031] The present invention further provides a process for the
preparation of the silicon-containing polyol, polyamine, polyepoxy
or polyisocyanate of formula (I) or (II) defined above which
comprises the steps of:
[0032] (i) reacting a compound of formula (A) or (B)
##STR00003##
in which R.sub.3 to R.sub.10 and x and y are as defined above
[0033] with a compound of formula (C)
##STR00004##
and
[0034] (ii) subjecting the product of step (i) to
hydrosilation.
[0035] The gels of the present invention possess visco-elastic
properties and have a natural tissue feel to suit, for example,
soft tissue implant gel applications such as breast implants. These
gels also have a low level of extractables preferably less than
15%, more preferably less than 10%, most preferably less than 5%
based on the total weight of the gel.
[0036] In a particularly preferred embodiment suitable for breast
implant applications, the gel is a reaction product of: [0037] (a)
the silicon-containing polyol, polyamine, polyepoxy or
polyisocyanate of formula (I) or (II) defined above; and [0038] (b)
C.sub.1-6 alkane diol or diamine, polysiloxane diol or diamine such
as PDMS and/or a diisocyanate such as MDI.
[0039] Thus, the present invention also provides a biomaterial,
device, article or implant which is wholly or partly composed of
the gels defined above.
[0040] The present invention further provides a filler material for
a medical implant such as a breast implant which comprises the gel
defined above.
DETAILED DESCRIPTION
[0041] The biostable silicon-containing gel of the present
invention is a chemical gel. When a cross-linked network is
formulated such that the reactive groups are in a perfect balance
then, during the course of the reaction, the network begins to
vitrify and ends up being a hard solid. If the reaction is not
allowed to go to completion by creating an imbalance in the
reactive groups, then an off-stoichiometric system occurs which is
capable of gelation. Thus, one reactive group is in excess and
remains incompletely reacted. This excess amount acts similar to
the non-reactive swelling medium in physical gels. However, usually
lower amounts of unreacted material, in comparison to the swelling
agents, can be formulated to achieve a similar effect to a physical
gel and that, in turn, implies lower extractable species. The level
of extractables in the gel of the present invention is preferably
less than 15%, more preferably less than 10%, most preferably less
than 5% based on the total weight of the gel.
[0042] The term "extractables" refers to the unreacted portion of
the gel which is generally fluid and free to migrate out of the gel
at body temperature of 38.degree. C. and more specifically, refers
to the unreacted fluid portion of a gel which is extracted by
organic solvents at temperatures in the range from 20.degree. C. to
40.degree. C.
[0043] The term "biostable" refers to the stability of the polymer
when in contact with cells and/or bodily fluids of living animals
or humans.
[0044] The term "average functionality" of a polymerisation system
refers to the average number of functional groups per monomer for
all types of monomer molecules and is defined by the following
formula:
f avg = i n i f i i n i ##EQU00001##
[0045] in which
[0046] n.sub.i is number of molecules of monomer i with
functionality groups f.sub.i.
[0047] Preferably, the average functionality of the gel is 2 to 5,
more preferably 2.05 to 3.5, most preferably 2.1 to 3.25.
[0048] The components (a) and (b) are preferably mixed so that the
NCO/OH or NH.sub.2 ratio is less than 1, more preferably from 0.4
to 0.7 so as to provide the appropriate rheological response.
[0049] It will be understood that the molecular weight values
referred to herein are "number average molecular weights".
Silicon-Containing Polyol, Polyamine, Polyepoxy or
Polyisocyanate
[0050] The silicon-containing polyol, polyamine, polyepoxy or
polyisocyanate (a) can have 1 or more functional groups provided
that the average functionality of the gel is preferably 1 to 5.
Component (a) is preferably a long chain macromer.
[0051] The functional groups of component (a) are preferably
independently selected from OH, NCO, epoxy and NR'R'' in which R'
and R'' are independently selected from H, CO.sub.2H and C.sub.1-6
alkyl, preferably H and C.sub.1-4 alkyl or are groups capable of
activation by free radical initiation such as groups containing
double or triple bonds, for example, vinyl or C.sub.1-6alkyl
acrylates.
[0052] Suitable silicon-containing polyols, polyepoxys polyamines
or polyisocyanates (a) include compounds of the formula (I) or (II)
defined above such as T-triols, T-vinylsiloxanes, T-epoxysiloxanes
and T-triisocyanates.
[0053] Representative examples of compounds of the formula (I) are
as follows:
##STR00005## ##STR00006## ##STR00007##
[0054] A representative example of a compound of the formula (II)
is as follows:
##STR00008##
[0055] The molecular weight of component (a) is at least 20,000,
preferably 30,000 to 200,000, more preferably 40,000 to 80,000.
Diol or Diamine
[0056] The diol or diamine may be a polyether, polycarbonate,
polyalkylene or C.sub.1-6 alkane. The diol or diamine may also
contain silicon such as a polysiloxane diol or diamine or a
silicon-based polycarbonate.
[0057] Suitable polyether diols and diamines include those
represented by the formula (III)
A-[(CH.sub.2).sub.m--O].sub.n-A'
in which
[0058] A and A' are OH or NHR wherein R is H or optionally
substituted C.sub.1-6 alkyl, more preferably optionally substituted
C.sub.1-4 alkyl;
[0059] m is an integer of 4 or more, preferably 4 to 18; and
[0060] n is an integer of 2 to 50.
[0061] Polyether macrodiols of formula (III) wherein m is 4 to 10
such as polytetramethylene oxide(PTMO), polyhexamethylene oxide
(PHMO), polyheptamethylene oxide, polyoctamethylene oxide (POMO)
and polydecamethylene oxide (PDMO) are preferred.
[0062] The preferred molecular weight range of the polyether is 200
to 5000, more preferably 200 to 2000.
[0063] Suitable polycarbonate diols include poly(alkylene
carbonates) such as poly(hexamethylene carbonate) and
poly(decamethylene carbonate); polycarbonates prepared by reacting
alkylene carbonate with alkanediols for example 1,4-butanediol,
1,10-decanediol (DD), 1,6-hexanediol (HD) and/or 2,2-diethyl
1,3-propanediol (DEPD); and silicon based polycarbonates prepared
by reacting alkylene carbonate with
1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane (BHTD) and/or
alkanediols.
[0064] It will be appreciated when both the polyether and
polycarbonate macrodiols are present, they may be in the form of a
mixture or a copolymer. An example of a suitable copolymer is a
copoly(ether carbonate) macrodiol represented by the formula
(IV)
##STR00009##
in which
[0065] R.sub.1 and R.sub.2 are the same or different and selected
from an optionally substituted C.sub.1-6 alkylene, C.sub.2-6
alkenylene, C.sub.2-6 alkynylene, arylene or a heterocyclic
divalent radical; and
[0066] p and q are integers of 1 to 20.
[0067] Although the compound of formula (IV) above indicates blocks
of carbonate and ether groups, it will be understood that they also
could be distributed randomly in the main structure.
[0068] Examples of C.sub.1-6 alkane diols or diamines include
methane diol, butane diol or hexane diol.
[0069] Suitable polysiloxane diols or diamines are represented by
the formula (V):
##STR00010##
in which
[0070] A and A' are OH or NHR wherein R is H or optionally
substituted C.sub.1-6 alkyl, more preferably optionally substituted
C.sub.1-4 alkyl;
[0071] R.sub.11, R.sub.12, R.sub.13 and R.sub.14 are independently
selected from hydrogen or optionally substituted C.sub.1-6
alkyl;
[0072] R.sub.15 and R.sub.16 are the same or different and selected
from optionally substituted C.sub.1-6 alkylene, C.sub.2-6
alkenylene, C.sub.12-6 alkynylene, arylene or a heterocyclic
divalent radical; and
[0073] p is an integer of 1 or greater.
[0074] A preferred polysiloxane is PDMS which is a compound of
formula (V) in which A and A' are hydroxyl, R.sub.11 to R.sub.14
are methyl and R.sub.15 and R.sub.16 are as defined above.
Preferably R.sub.15 and R.sub.16 are the same or different and
selected from propylene, butylene, pentylene, hexylene,
ethoxypropyl (--CH.sub.2CH.sub.2OCH.sub.2CH.sub.2CH.sub.2--),
propoxypropyl and butoxypropyl.
[0075] Other silicon-containing diols of the formula (V) are
1,3-bis(4-hydroxybutyl)tetramethyl disiloxane (BHTD) (compound of
formula (V) in which A and A' are OH, R.sub.11, R.sub.12, R.sub.13
and R.sub.14 are methyl, R.sub.15 and R.sub.16 are butyl and
R.sub.17 is O), 1,4-bis(3-hydroxypropyl)tetramethyl disilylethylene
(compound of formula (V) in which A and A' are OH, R.sub.1,
R.sub.12, R.sub.13 and R.sub.14 are methyl, R.sub.15 and R.sub.16
are propyl and R.sub.17 is ethylene) and
1-4-bis(3-hydroxypropyl)tetramethyl disiloxane, more preferably
BHTD.
[0076] The polysiloxanes may be obtained as commercially available
products such as X-22-160AS from Shin Etsu in Japan or prepared
according to known procedures. The preferred molecular weight range
of the polysiloxane macrodiol is 200 to 6000, more preferably from
200 to 5000.
[0077] Other preferred polysiloxanes are polysiloxane macrodiamines
which are polymers of the formula (V) wherein A is NH.sub.2, such
as, for example, amino-terminated PDMS.
[0078] Suitable silicon-containing polycarbonates include those
described in International Patent Publication No. WO 98/54242, the
entire content of which is incorporated herein by reference.
[0079] A preferred silicon-containing polycarbonate has the formula
(VI):
##STR00011##
in which
[0080] R.sub.11, R.sub.12, R.sub.13, R.sub.14 and R.sub.15 are as
defined in formula (V) above;
[0081] R.sub.16 is an optionally substituted C.sub.1-6 alkylene,
C.sub.2-6 alkenylene, C.sub.2-6 alkynylene, arylene or a
heterocyclic divalent radical;
[0082] R.sub.17 is a divalent linking group, preferably O, S or
NR.sub.18;
[0083] R.sub.18 and R.sub.19 are same or different and selected
from hydrogen or optionally substituted C.sub.1-6 alkyl;
[0084] A and A' are as defined in formula (V) above;
[0085] m, y and z are integers of 0 or more; and
[0086] x is an integer of 0 or more.
[0087] Preferably z is an integer of 0 to 50 and x is an integer of
1 to 50. Suitable values for m include 0 to 20, more preferably 0
to 10. Preferred values for y are 0 to 10, more preferably 0 to
2.
[0088] A preferred silicon-containing polycarbonate is a compound
of the formula (VI) in which A and A' are hydroxyl.
[0089] Particularly preferred silicon-containing polycarbonate
diols are compounds of the formula (VI) in which A and A' are
hydroxyl, R.sub.11, R.sub.12, R.sub.13 and R.sub.14 are methyl,
R.sub.18 is ethyl, R.sub.19 is hexyl, R.sub.15 and R.sub.16 are
propyl or R.sub.14 butyl and R.sub.17 is 0 or
--CH.sub.2--CH.sub.2--, more preferably R.sub.5 and R.sub.16 are
propyl when R.sub.17 is 0 and R.sub.15 and R.sub.16 are butyl when
R.sub.17 is --CH.sub.2--CH.sub.2--. The preferred molecular weight
range of the silicon-based polycarbonate macrodiol is from 400 to
5000, more preferably from 400 to 2000.
Diisocyanate
[0090] The diisocyanate may be an aliphatic or aromatic
diisocyanate such as 4,4'-diphenylmethane diisocyanate (MDI),
methylene biscyclohexyl diisocyanate (H.sub.12MDT), p-phenylene
diisocyanate (p-PDI), trans-cyclohexane-1,4-diisocyanate (CHDI),
1,6-diisocyanatohexane (DICH), 1,5-diisocyanatonaphthalene (NDI),
para-tetramethylxylene-diisocyanate (p-TMXDI),
meta-tetramethylxylene diisocyanate (m-TMXDI), 2,4-toluene
diisocyanate (2,4-TDI) isomers or mixtures thereof or isophorone
diisocyanate (IPDI). Aromatic diisocyanates such as MDI are
preferred.
Initiator
[0091] The term "initiator" refers to at least one molecule which
when activated by an energy source, will result in free radical
polymerisation of polymers in a curing step. The energy source
initiating the polymerisation may be thermal, photolytic or based
on a redox system of components with the result that free radical
polymerisation occurs to cure the prepolymer composition.
[0092] The selection of the initiator for the purpose of triggering
free radical curing is dependant on the method of initiation
selected. Initiation may be thermal, photolytic or based on a redox
system of components and is preferably by an external source. For
example, camphorquinone, phosphine oxide based initiators such as
(2,4,6-trimethyl benzoyl)diphenyl phosphine oxide are suitable and
redox initiators such as ammonium persulfate and sodium
metabisulfite, gamma radiation or ultrasound are also suitable. For
in-vivo applications photolytic initiators or redox based systems
are preferred. More preferable is a system that cures the polymer
using a wave length that is either in the UV or visible region of
electromagnetic radiation. Of the two, visible light initiation is
more desirable in biomedical applications. In one embodiment of the
invention, visible light source having a maximum wave length of
450.+-.30 nm is used. Examples of photoinitiators include but are
not limited to 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651),
hydroxyalkyl phenones (1-hydroxycyclohexyl phenyl ketone (Irgacure
184),
2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone
(Irgacure 907),
2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Darocur
2959), Darocur 4265, Darocur TPO, Darocur 1173, Irgacure 500, 784,
907, 2959, 819, 2020, 2022, 1000, 369, 651, 1300, 819/819W, 2005
and 2010W, Dragacure 1173, polysilanes, Esacure KP150
(hydroxyalkylphenylketone), camphorquinone, Rosebengal,
ethyl-4-N,N-dimethylamino-benzoate(4EDMAB)/triethanolamine, .alpha.
alkoxydeoxybenzoins, .alpha.,.alpha.-dialkoxy-acetophenone (DEAP),
(1-hydroxy-cyclohexyl-phenylketone), dibenzoyl disulphide, S-phenyl
thio-benzoates, acylphosphine oxide, dibenzoylmethanes, O-acyl
.alpha.-oximinoketones, phenylazo-4-diphenyl sulphone,
benzophenones, flourenones, xanthones, thioxanthones, benzils,
ketals (2,2-dimethoxy-2-phenylacetophenone DMP),
.alpha.-ketocoumarines, anthraquinone, ethyl eosin and
terephthalophenones. Examples of free radical initiators include
benzoyl peroxide and cumyl peroxide.
[0093] The amount of initiator (c) is preferably 0.125% to 5%, more
preferably 0.25% to 2% based on the total weight of the gel.
Chemical Definitions
[0094] The term "C.sub.1-6alkylene" is a divalent radical
equivalent of the term "C.sub.1-6 alkyl". The two bonds connecting
the alkylene to the adjacent groups may come from the same carbon
atom or difference carbon atoms in the divalent radical.
[0095] The term "C.sub.1-6alkyl" denotes straight chain, branched
or mono- or poly-cyclic alkyl having 1 to 6 carbon atoms,
preferably C.sub.1-4 alkyl. Examples of straight chain and branched
alkyl include methyl, ethyl, propyl, isopropyl, butyl, isobutyl,
sec-butyl, tert-butyl, amyl, isoamyl, sec-amyl, 1,2-dimethylpropyl,
1,1-dimethylpropyl, pentyl, neopentyl, hexyl, 4-methylpentyl,
1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1,1-dimethylbutyl,
2,2-dimethylbutyl, 3,3-dimethylbutyl, 1,2-dimethylbutyl,
1,3-dimethylbutyl, 1,2,2-trimethylpropyl, 1,1,2-trimethylpropyl and
the like. Examples of cyclic alkyl include cyclopropyl, cyclobutyl,
cyclopentyl, cyclohexyl and the like.
[0096] The term "C.sub.2-6alkenyl" denotes groups formed from
straight chain, branched or mono- or poly-cyclic hydrocarbon groups
having at least one double bond. The alkenyl group may have E or Z
stereochemistry where applicable. Examples of alkenyl include
vinyl, allyl, 1-methylvinyl, butenyl, iso-butenyl,
3-methyl-2-butenyl, 1-pentenyl, cyclopentenyl,
1-methyl-cyclopentenyl, 1-hexenyl, 3-hexenyl, cyclohexenyl) and the
like.
[0097] The term "C.sub.2-6alkynyl" denotes groups formed from
straight chain, branched, or mono- or poly-cyclic hydrocarbon
groups having at least one triple bond. Examples of alkynyl include
ethynyl, 1-propynyl, 1- and 2-butynyl, 2-methyl-2-propynyl,
2-pentynyl, 3-pentynyl, 4-pentynyl, 2-hexynyl, 3-hexynyl,
4-hexynyl, 5-hexynyl and the like.
[0098] The term "C.sub.1-6 alkoxy" denotes linear or branched
oxy-containing radicals each having alkyl portions of 1 to 6 carbon
atoms. Examples of alkoxy include methoxy, ethoxy, n-propoxy,
iso-propoxy, n-butoxy, n-pentoxy t-butoxy and the like.
[0099] The term "arylene" denotes single, polynuclear, conjugated
and fused divalent residues of aromatic hydrocarbons. Examples of
aryl include phenyl, biphenyl, terphenyl, quaterphenyl,
phenoxyphenyl, naphthyl, tetrahydronaphthyl, anthracenyl,
dihydroanthracenyl, benzanthracenyl, dibenzanthracenyl,
phenanthrenyl and the like.
[0100] The term "heterocyclyl" denotes mono- or poly-cyclic
heterocyclyl groups containing at least one heteroatom selected
from nitrogen, sulphur and oxygen. Suitable heterocyclyl groups
include N-containing heterocyclic groups, such as, unsaturated 3 to
6 membered heteromonocyclic groups containing 1 to 4 nitrogen
atoms, for example, pyrrolyl, pyrrolinyl, imidazolyl, pyrazolyl,
pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazolyl or
tetrazolyl; saturated 3 to 6 membered heteromonocyclic groups
containing 1 to 4 nitrogen atoms, such as pyrrolidinyl,
imidazolidinyl, piperidino or piperazinyl; unsaturated condensed
heterocyclic groups containing 1 to nitrogen atoms, such as,
indolyl, isoindolyl, indolizinyl, benzimidazolyl, quinolyl,
isoquinolyl, indazolyl, benzotriazolyl or tetrazolopyridazinyl;
unsaturated 3 to 6-membered heteromonocyclic group containing an
oxygen atom, such as, pyranyl or furyl; unsaturated 3 to 6-membered
heteromonocyclic group containing 1 to 2 sulphur atoms, such as,
thienyl; unsaturated 3 to 6-membered heteromonocyclic group
containing 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms, such as,
oxazolyl, isoazolyl or oxadiazolyl; saturated 3 to 6-membered
heteromonocyclic group containing 1 to 2 oxygen atoms and 1 to 3
nitrogen atoms, such as, morpholinyl; unsaturated condensed
heterocyclic group containing 1 to 2 oxygen atoms and 1 to 3
nitrogen atoms, such as, benzoxazolyl or benzoxadiazolyl;
unsaturated 3 to 6-membered heteromonocyclic group containing 1 to
2 sulphur atoms and 1 to 3 nitrogen atoms, such as thiazolyl or
thiadiazolyl; saturated 3 to 6-membered heteromonocyclic group
containing 1 to 2 sulphur atoms and to 3 nitrogen atoms, such as,
thiadiazolyl; and unsaturated condensed heterocyclic group
containing 1 to 2 sulphur atoms and 1 to 3 nitrogen atoms, such as
benzothiazolyl or benzothiadiazolyl.
[0101] The term "optionally substituted" denotes a group that may
or may not be further substituted with one or more groups selected
from oxygen, nitrogen, sulphur, C.sub.1-4 alkyl, C.sub.2-6 alkenyl,
C.sub.2-4 alkynyl, aryl, halo, halo C.sub.1-4 alkyl,
haloC.sub.2-4alkenyl, haloC.sub.2-4alkynyl, haloaryl, hydroxy,
C.sub.1-4 alkoxy, C.sub.2-4alkenyloxy, C.sub.2-4alkynyloxy,
aryloxy, carboxy, benzyloxy, haloC.sub.1-4alkoxy,
haloC.sub.2-4alkenyloxy, haloalkynyloxy, haloaryloxy, nitro,
nitroC.sub.1-4alkyl, nitroC.sub.2-4alkenyl, nitroC.sub.2-4alkynyl,
nitroaryl, nit roheterocyclyl, azido, amino, C.sub.1-4alkylamino,
C.sub.2-4alkenylamino, C.sub.2-4alkynylamino, arylamino,
benzylamino, acyl, C.sub.2-4alkenylacyl, C.sub.2-4alkynylacyl,
arylacyl, acylamino, acyloxy, aldehydo, C.sub.1-6alkylsulphonyl,
arylsulphonyl, C.sub.1-6alkylsulphonylamino, aryl sulphonylamino,
alkylsulphonyloxy, arylsulphonyloxy, heterocyclyl, heterocycloxy,
heterocyclylamino, haloheterocyclyl, C.sub.1-4alkylsulphenyl,
arylsulphenyl, carboC.sub.1-6alkoxy, carboaryloxy, mercapto,
C.sub.1-4alkylthio, arylthio, acylthio and the like.
Process
[0102] The polyurethanes of the present invention may be prepared
by any technique familiar to those skilled in the manufacture of
polyurethanes. These include one or two step procedures. The
polymerisation can be carried out in conventional apparatus or
within the confines of a reactive injection moulding or mixing
machines.
[0103] In a one step procedure, the appropriate amounts of
components (a) and (b) or (c) are mixed. The mixture is then cured.
As described above, the mixture of components (a) and (c) may
require the application of an external energy source such as UV
radiation depending on the initiator employed.
[0104] The polyurethanes can also be prepared by a two step
procedure where a prepolymer having terminally reactive
polyisocyanate groups is prepared from component (b). The
prepolymer is then reacted with component (a).
Additives
[0105] If desired, conventional polyurethane processing additives
such as catalysts for example dibutyl tin dilaurate (DBTD),
stannous oxide (SO), 1,8-diazabicyclo[5,4,0]undec-7-ene (DABU),
1,3-diacetoxy-1,1,3,3-tetrabutyldistannoxane (DTDS),
1,4-diaza-(2,2,2)-bicyclooctane (DABCO),
N,N,N',N'-tetramethylbutanediamine (TMBD) and dimethyltin dilaurate
(DMTD); antioxidants for example Irganox (Registered Trade Mark);
radical inhibitors for example trisnonylphenyl phosphite (TNPP);
stabilisers; lubricants for example Irgawax (Registered Trade
Mark); dyes; pigments; inorganic and/or organic fillers; and
reinforcing materials can be incorporated into the biostable
polymer during preparation. Such additives are preferably added in
step (i) of the processes of the present invention up to 10% based
on the total weight of gel, preferably up to 5%, more preferably 2%
or less.
Medical Applications
[0106] The polyurethanes of the present invention are particularly
useful in preparing biomaterials and medical devices, articles or
implants.
[0107] The term "biomaterial" refers to a material which is used in
situations where it comes into contact with the cells and/or bodily
fluids of living animals or humans.
[0108] The medical devices, articles or implants may include soft
tissue implants designed to replace and augment tissues including
breast tissue, testicular tissue, cartilage, muscle and any
connective tissue apart from teeth and bone such as the soft tissue
implants disclosed in PCT/AU2006/001488; orthopaedic joints or
parts thereof including spinal discs and small joints; bone suture
anchors; reconstructive facial surgery; controlled drug release
devices; components in key hole surgery; biosensors; tools and
accessories for insertion of medical devices, infusion and flow
control devices; and urethral, neurological or vascular bulking
agents.
[0109] When the gel is used as a soft tissue implant it may be
implantedusing the method disclosed in PCT/AU2006/001488.
[0110] In the description of the invention, except where the
context requires otherwise due to express language or necessary
implication, the words "comprise" or variations such as "comprises"
or "comprising" are used in an inclusive sense, i.e. to specify the
presence of the stated features but not to preclude the presence or
addition of further features in various embodiments of the
invention.
EXAMPLES
[0111] The invention will now be described with reference to the
following non-limiting examples.
Physical Property Tests
[0112] Biological Stability:
[0113] The biological stability of the gels is achieved by the
incorporation of large amount of silicon.
[0114] Rheology:
[0115] Both the natural feel and the form stability can be related
to rheological factors. A good creep-recovery performance describes
the feel or the elasticity. The parameters of storage modulus (G')
and loss modulus (G'') as measured in frequency sweep measurement
on a rheometer describe the form stability. G'>G'' at low
frequencies (0.01 s.sup.-1 to 1 s.sup.-1) implies form
stability.
[0116] Procedure for Creep Recovery & Frequency Sweep
Analysis:
[0117] The Creep Recovery is tested using Haake RheoStress 1
Rheometer. After the initialisation process under compressed air
atmosphere, the parallel plates are subjected to zero point
measurement. The sample is loaded and the gap position set. The
excess sample is trimmed and is ready for the experiment.
[0118] The creep recovery analysis is carried out at 37.degree. C.
The sample is thermostated for 300 s before the actual experiment
starts to ensure temperature equilibrium. The experiment is carried
at a force of 10 Pa for a duration of 60 s and from the plot of J
(1/Pa, compliance) Vs t(s), the creep recovery results can be
obtained.
[0119] For frequency sweep measurement, after trimming the sample,
the experiment was conducted at 37.degree. C., with similar
temperature equilibrating conditions. It is carried out in the
frequency range of 0.01 Hz to 10 Hz. The frequency sweep provides
about the structural conditions of the sample. It is possible to
distinguish between a particle solution, an entangled solution
(paste) and a three dimensional network (gel) simply by the shape
of G', G'' (Pa) and .eta.* (Pa s) Vs f (Hz) curves.
[0120] Extractables:
[0121] The extractables in hexane as measured in the Soxhlet
extraction technique over 24 hours shows an average value of around
50% for the silicone gels.
Extraction Procedure
[0122] The extraction procedure involved five pieces of apparatus:
condenser, soxhlet extractor tube, extraction thimble, 250 mL
round-bottom flask and a heating mantle. The procedure was carried
out as follow: [0123] Accurately weighed the 250 mL round bottom
(R.B.) flask. [0124] Poured approximately 160 mL of Hexane into the
R.B. flask [0125] Placed a known amount of gel sample into the
thimble and the thimble was placed in the soxhlet extractor tube.
[0126] The R.B. flask was adapted to the lower end of the soxhlet
extractor tube and the condenser was adapted the top end of the
tube. [0127] The gel sample was allowed to reflux in Hexane for 22
hours. [0128] At the end of the extraction period, the extractables
in Hexane were collected in the R.B. flask. [0129] Hexane was
removed using rotary evaporator. [0130] The R.B. flask containing
the extractable residue was accurately weighed [0131] The amount of
extractable residue was calculated from the weight of the gel used
for extraction. [0132] The results were report as % weight
loss.
Basic Strategy
[0133] The approaches used in the formulation of gels involve
initiation of cross-linking by the use of various functionalities
of the reactants including unsaturated or double bonds in the PDMS
molecule and then making the double bond reactive by using a
ultraviolet light source or other techniques.
Reactants used for Gel Synthesis
[0134] The reactants used for synthesising the gels include a
di-isocyanate in the form of MDI and different hydroxyl terminated
polyols of functionalities varying from 1 to 3. The reactants are
set out in Table 1 below:
TABLE-US-00001 TABLE 1 Isocyanate Methylene diphenylene isocyanate
(MDI) Silicon containing bi- bis(6-hydroxyethoxypropyl) functional
macro-diol polydimethylsiloxane (PDMS) of number average molecular
weight (Mn) between 900-2100 Tri-functional Polyols A mixture of
silicon containing polyols of different functionalities with an
effective functionality of 3 A silicon containing polyol having an
actual functionality of 3
[0135] Some of the above reactants are available commercially,
however, the silicon-containing multifunctional polyols or
polyisocyanates that are not available commercially have been
synthesised in Examples A to F below.
Example A
T-Shape Triol
[0136] This example illustrates the preparation of
hydroxyethoxypropyl terminated 9.09%-(hydroxyethoxypropyl methyl
siloxane)(dimethyl siloxane) copolymer (Ia).
[0137] 498.04 g of octamethylcyclotetrasiloxane (D.sub.4), 0.62 g
of 1,3,5,7-tetramethylcyclotetrasiloxane, and 1.34 g of TMDS were
mixed in a glass bottle containing a magnetic stirrer bar. 0.64 g
of trifluoromethanesulfonic acid was added to the mixture and the
bottle sealed with an air tight cap. The mixture was stirred
vigorously for 18 hours at room temperature after which 10 g of
sodium carbonate was added. The bottle was resealed and stirred for
6 hours, after which the sodium bicarbonate was filtered off to
give 500 g of hydride terminated (methylhydrosiloxane)
(dimethylsiloxane) copolymer intermediate.
[0138] In a three-neck 2 L round bottomed flask equipped with a
water cooled condenser equipped with a silica gel drying tube and a
thermometer were placed with 500 g of the hydride terminated
poly(methylhydrosiloxane) (dimethylsiloxane) copolymer and 357 mL
of dry toluene. The mixture was heated, while stirring, to
60.degree. C. 0.0015 g of Karstedt's catalyst was added to the
mixture. 4.07 g of 2-allyloxyethanol was added drop wise to the
mixture during which time the temperature of the mixture rose to
114.degree. C. after which the reaction mixture was maintained at
70.degree. C. for 1 hour. Silanic hydrogen content was checked by
infrared spectroscopy. When no trace was detectable, the reaction
was considered to be complete. The reaction mixture was allowed to
cool to room temperature and treated with 20 g of activated carbon
for 18 hours while stirring. The reaction mixture was filtered
through celite to remove the carbon. The toluene was removed by
rotary evaporator at 80.degree. C. under a reduced pressure of 20
torr. The mixture was transferred to a Kugelrohr distillation
apparatus and stripped of low molecular weight species at
100.degree. C. under a reduced of 1.times.10.sup.-1 torr to give
504.07 of hydroxyethoxypropyl terminated 9.09%-(hydroxyethoxypropyl
methyl siloxane)(dimethyl siloxane) copolymer (Ia) as a colourless
oil (MW 50001.07).
Example B
Tripod Triol
[0139] This example illustrates the preparation of
.alpha.,.alpha.',.alpha.''-(methylsilylidyne)tris-[.omega.[(hydroxyethoxy-
propyl-dimethylsilyl)oxy]poly(dimethylsilyene)]](9Cl) (IIa).
[0140] 138.28 g of D.sub.4 and 1.70 g of
methyltris(dimethylsiloxy)silane were mixed in a glass bottle
containing a magnetic stirrer bar. 0.006 g of
trifluoromethanesulfonic acid was added to the mixture and the
bottle sealed with an air tight cap. The mixture was stirred
vigorously for 7 hours at room temperature after which 10 g of
sodium bicarbonate was added. The bottle was resealed and stirred
overnight, after which the sodium carbonate was filtered off to
give 139.9 g of hydride terminated
.alpha.,.alpha.',.alpha.''-(methylsilylidyne)tris-[.omega.[(dimethylhydro-
silyl)oxy]poly(dimethylsilyene)]](9Cl) intermediate.
[0141] In a three-neck 1 L round bottomed flask equipped with a
water cooled condenser equipped with a silica gel drying tube, a
250-mL pressure compensating dropping funnel, and a thermometer
were placed 139.9 g of the
.alpha.,.alpha.',.alpha.''-(methylsilylidyne)tris-[.omega.[(dimethylhydro-
silyl)oxy]poly(dimethylsilyene)]](9Cl) intermediate and 250 mL of
dry toluene. The mixture was heated, while stirring, to 70.degree.
C. 0.5 mL of a toluene solution of Karstedt's catalyst (containing
0.1 mmoles Pt/mL) was added to the mixture. 2.10 g of
2-allyloxyethanol was added drop wise to the mixture from the
dropping funnel. The addition was made over a 45 minute period
during which time the temperature of the mixture rose to 95.degree.
C. after which the reaction mixture was maintained at 70.degree. C.
for 1 hour. Silanic hydrogen content was checked by infrared
spectroscopy. When no trace was detectable the reaction was
considered to be complete. The reaction mixture was allowed to cool
to room temperature and treated with 20 g of activated carbon for
18 hours whilst stirring. The reaction mixture was filtered through
celite to remove the carbon. The toluene was removed by rotary
evaporator at 80.degree. C. under a reduced pressure of 20 torr.
The pale yellow product was treated with 10 g of activated carbon
for 3 days to remove the residual colour. The oil was filtered
through celite to remove the carbon and then transferred to a
Kugelrohr distillation apparatus and stripped of low molecular
weight species at 140.degree. C. under a reduced pressure of
1.times.10.sup.-1 for to give 142 g
.alpha.,.alpha.',.alpha.''-(methylsilylidyne)tris-[.omega.[(hydroxyethoxy-
propyldimethylsilyl)oxy]poly(dimethylsily ene)]](9Cl) (IIa) as a
colourless oil (MW 50000).
Example C
T-Shape Acrylate Macrodiol
[0142] This example illustrates the preparation of
hydroxyethoxypropyl terminated 3.55%-(methylmethacryloxypropyl
methyl siloxane)(dimethyl siloxane) copolymer (Ib).
[0143] 246.61 g of 1,3,5,7-tetramethylcyclotetrasiloxane, 0.37 g of
D.sub.4 and 3.01 g of
.alpha.,.omega.-bis(hydroxyethoxypropyl)polydimethylsiloxane (MW
1943) were mixed in a glass bottle containing a magnetic stirrer
bar. 0.314 g of trifluoromethanesulfonic acid was added to the
mixture and the bottle sealed with an air tight cap. The mixture
was stirred vigorously for 3.5 hours at room temperature after
which 20 g of sodium bicarbonate was added. The bottle was resealed
and stirred for overnight, after which the sodium carbonate was
filtered off to give 250 g of hydroxyethoxypropyl terminated
(methylhydrosiloxane) (dimethyl siloxane) copolymer
intermediate.
[0144] In a three-neck 3 L round bottomed flask equipped with a
water cooled condensed equipped with a silica gel drying tube and a
thermometer were placed with 250 g of hydroxyethoxypropyl
terminated (methylhydrosiloxane) (dimethyl siloxane) copolymer
intermediate given above and 178.57 mL of dry toluene. The mixture
was heated, while stirring, to 60.degree. C. 0.0003 g of Karstedt's
catalyst was added to the mixture. 0.9782 g of allylmethacrylate
was added drop wise to the mixture. During the addition, the
temperature of the mixture rose to 72.degree. C. after which the
reaction mixture was maintained at 70.degree. C. for 18 hours.
Silanic hydrogen content was checked by infrared spectroscopy. When
no trace was detectable, the reaction was considered to be
complete. The reaction mixture was allowed to cool to room
temperature and treated with 20 g of activated carbon for 18 hours
while stirring. The reaction mixture was filtered through celite to
remove the carbon followed by filtration through a 0.2 .mu.m Teflon
filter. 0.0577 g of MEHQ was added to the toluene solution and then
the toluene was removed by rotary evaporator at 60.degree. C. under
a reduced pressure of 20 torr. The mixture was transferred to a
Kugelrohr distillation apparatus and stripped of low molecular
weight species at 50.degree. C. under a reduced pressure of
1.times.10.sup.-1 torr for 20 minutes. This process was repeated 3
times to give 200.86 g of hydroxyethoxypropyl terminated
3.55%-(methylmethacryloxypropyl methyl siloxane)(dimethyl siloxane)
copolymer (Ib) as a pale yellow oil (MW 161851.72).
Example D
T-Shape Triisocyanate
[0145] This example illustrates the preparation of isocyanate
terminated (propyl methyl siloxane)(dimethyl siloxane) copolymer
(Ic).
[0146] 149.41 g of D.sub.4, 0.18 g of
1,3,5,7-tetramethylcyclotetrasiloxane, and 0.40 g of TMDS were
mixed in a glass bottle containing a magnetic stirrer bar. 0.1907 g
of trifluoromethanesulfonic acid was added to the mixture and the
bottle sealed with an air tight cap. The mixture was stirred
vigorously for 24 hours at room temperature after which 5 g of
sodium bicarbonate was added. The bottle was resealed and stirred
for 24 hours, after which the sodium carbonate was filtered off
through 0.5 .mu.m filter paper under vacuum at room temperature to
give 150 g of hydride terminated (methylhydrosiloxane)
(dimethylsiloxane) copolymer intermediate.
[0147] In a three-neck 1 L round bottomed flask equipped with a
water cooled condensed equipped with a silica gel drying tube and a
thermometer were placed with 150 g of the hydride terminated
poly(methylhydrosiloxane) (dimethyl-siloxane) copolymer and 107.14
mL of dry toluene. The mixture was heated, while stirring, to
60.degree. C. 0.0005 g of Karstedt's catalyst was added to the
mixture. 0.99 g of allylisocyanate was added in drops. The reaction
mixture was maintained at 60.degree. C. for 2 hours. Absence of
silanic hydrogen and intactness of isocyanate group were checked by
infrared spectroscopy. When no trace of silanic hydrogen was
detectable the reaction was considered to be complete. The reaction
mixture was allowed to cool to room temperature. The reaction
mixture was filtered through 0.2 .mu.m filter paper under vacuum at
room temperature. The toluene was removed by rotary evaporator at
80.degree. C. under a reduced pressure of 20 torr to give 150.99 g
of isocyanate terminated (propyl methyl siloxane) (dimethyl
siloxane) copolymer (Ic) as a colourless oil (MW 25170.54).
Example E
Vinyl Siloxane Prepolymers
[0148] Vinyl siloxane prepolymers (Id)-(If) were prepared via
acid-catalysed ring opening polymerization of either
tetravinyl-tetramethyl cyclo tetra siloxane (D.sup.V.sub.4) or a
mixture of tetravinyl-tetramethyl cyclo tetra siloxane
(D.sup.V.sub.4) and octamethyl cyclo tetra siloxane (D.sub.4) or a
mixture of tetravinyl-tetramethyl cyclo tetra siloxane
(D.sup.V.sub.4), octamethyl cyclo tetra siloxane (D.sub.4) and
hexamethyl disiloxane to prepare poly vinyl-methyl siloxane
prepolymers.
[0149] The following examples illustrate the preparation of vinyl
siloxane prepolymers.
[0150] The raw materials used in the following examples are:
##STR00012##
Example E1
[0151] 50 g of D.sup.V.sub.4 was taken in glass bottle and mixed
with 0.05 g of trifluoro sulfonic acid. The bottle was sealed with
airtight cap and the mixture was stirred vigorously for 24 hours at
room temperature, after which the reaction mixture was neutralized
with 5 g of sodium bicarbonate and then kept for stirring for
another .about.16 hours. The sodium bicarbonate was then filtered
off through 0.45 .mu.filter paper under vacuum at room temperature.
This was followed by a stripping step to remove the low molecular
weight siloxane species from the vinyl siloxane prepolymers
(Id).
Example E2
[0152] 1.89 g of D.sup.V.sub.4 and 8.11 g of D.sub.4 were taken in
glass bottle and mixed with 0.01 g of trifluoro sulfonic acid. The
bottle was sealed with airtight cap and the mixture was stirred
vigorously for 24 hours at room temperature, after which the
reaction mixture was neutralized with 5 g of Sodium bicarbonate and
then kept for stirring for another .about.16 hours. The sodium
bicarbonate was then filtered off through 0.45.mu. filter paper
under vacuum at room temperature. This was followed by a stripping
step to remove the low molecular weight siloxane species from the
vinyl siloxane prepolymers (Ie).
Example E3
[0153] 22.44 g of D.sup.V.sub.4 and 18.46 g of D.sub.4 and 10.10 g
HMDS were taken in glass bottle and mixed with 0.07 g of trifluoro
sulfonic acid. The bottle was sealed with airtight cap and the
mixture was stirred vigorously for 24 hours at room temperature,
after which the reaction mixture was neutralized with 5 g of Sodium
bicarbonate and then kept for stirring for another .about.16 hours.
The sodium bicarbonate was filtered off through 0.45 .mu.filter
paper under vacuum at room temperature. This was followed by a
stripping step to remove the low molecular weight siloxane species
from the vinyl siloxane prepolymers (If).
Example F
T-Shape Triepoxysiloxane
[0154] This example illustrates the preparation of epoxy terminated
(propoxy methyl siloxane) (dimethyl siloxane) copolymer (Ig).
[0155] 248 g of D.sub.4, 0.30 g of
1,3,5,7-tetramethylcyclotetrasiloxane, and 1.70 g of TMDS were
mixed in a glass bottle containing a magnetic stirrer bar. 0.3194 g
of trifluoromethanesulfonic acid was added to the mixture and the
bottle sealed with an air tight cap. The mixture was stirred
vigorously for 24 hours at room temperature after which 5 g of
sodium bicarbonate was added. The bottle was resealed and stirred
for 24 hours, after which the sodium carbonate was filtered off
through 0.5 .mu.m filter paper under vacuum at room temperature to
give 250 g of hydride terminated (methylhydrosiloxane)
(dimethylsiloxane) copolymer intermediate.
[0156] In a three-neck 1 L round bottomed flask equipped with a
water cooled condenser equipped with a silica gel drying tube, a
250 mL pressure compensating dropping funnel and a thermometer were
placed 250 g of the hydride terminated poly(methylhydrosiloxane)
(dimethyl-siloxane) copolymer and 178.57 mL of dry toluene. The
mixture was heated, while stirring, to 60.degree. C. 0.0017 g of
Karstedt's catalyst was added to the mixture. 5.1771 g of allyl
gycidyl ether was added in drops. During the addition, the
temperature of the mixture rose to 72.degree. C. after which the
reaction mixture was maintained at 70.degree. C. for 3.5 hours.
Absence of silanic hydrogen and intactness of isocyanate group were
checked by infrared spectroscopy. When no trace of silanic hydrogen
was detectable, the reaction was considered to be complete. The
reaction mixture was allowed to cool to room temperature and
treated with 20 g of activated carbon for 18 hours while stirring.
The reaction mixture was filtered through celite to remove the
carbon followed by filtration through a 0.2 .mu.m Teflon filter.
The reaction mixture was allowed to cool to room temperature. The
reaction mixture was filtered through 0.2 .mu.m filter paper under
vacuum at room temperature. The toluene was removed by rotary
evaporator at 60.degree. C. under a reduced pressure of 20 torr.
The mixture was then transferred to a Kugelrohr distillation
apparatus and stripped of low molecular weight species at
75.degree. C. under a reduced pressure of 1.times.10.sup.-1 torr
for 2 hours. This process was repeated 3 times to give 255.18 g
epoxy terminated (propoxy methyl siloxane) (dimethyl siloxane)
copolymer (Ig) as a colourless oil (MW 20046.98). Similarly, the
above synthesis can be modified to prepare different possible end
terminated disiloxane copolymers. Examples include, epoxy
terminated (propoxy methyl siloxane) (pendant hydroxyethoxypropyl
methyl siloxane) (dimethyl siloxane) copolymer (Ih),
hydroxyethoxypropyl siloxane (pendant epoxy terminated (propoxy
methyl siloxane)) (dimethyl siloxane) copolymer (Ii) and epoxy
terminated (propoxy methyl siloxane) (pendant
methylmethacryloxypropyl methyl siloxane) (dimethyl siloxane)
copolymer (Ij).
##STR00013## ##STR00014## ##STR00015##
Gel Synthesis
[0157] The gels were synthesised using different processes: One
Shot Process--All reactants of the gel were added and mixed
together.
[0158] Two Stage Slow Additive Process--The gel synthesis in this
process occurred with the formation of a difunctional isocyanate
terminated pre-polymer in the first stage followed by the addition
of the hydroxyl terminated multifunctional polyols.
[0159] UV Curing--For the process of curing with ultra-violet
light, a formulation containing an unsaturation in the polyol
segment was prepared. A photoinitiator was added to the mixture and
this in the presence of an externally supplied, long wavelength,
ultraviolet radiation resulted in the formation of a cross linked
gel.
Example 1
[0160] 4,4'-Diphenylmethane diisocyanate (MDI) and synthesised
hydroxyethoxypropyl terminated 9.09%-(hydroxyethoxypropyl methyl
siloxane) (dimethyl siloxane) copolymer (T-Triol) (Ia) prepared in
Example A were stirred for 5 min and cured.
[0161] The formulations of the components, stoichiometries are
tabulated below.
TABLE-US-00002 MDI MW of Triol NCO/OH (g) T-Triol (g) 1.0 0.40 20
000 21.59
[0162] A gel with good rheological properties was obtained.
Example 2
[0163] The synthesised T-shape trisiocyanate (Ic) prepared in
Example D and siloxane polyols of varying molecular weight (1000,
2000) were stirred mechanically with and without catalyst for 5 min
at room temperature and cured.
TABLE-US-00003 T Tri- isocyanate MW of T-tri- PDMS PDMS NCO/OH (g)
isocyanate MW (g) 1.0 10 50000 2000 0.28 1.0 10 50000 1000 0.61
[0164] The synthesised gel was very elastic and had good
rheological properties.
Example 3
[0165] The synthesised T-shape trisiocyanate (Ic) prepared in
Example D and short chain diols (eg. butane diol) were stirred
mechanically with and without catalyst for 5 min at room
temperature and cured. In one example, 10 g of the T-shape
triisocyanate was reacted with 0.027 g of BDO, the mixture stirred
mechanically at room temperature for 5 minutes. The mixture cured
at room temperature to a good elastic gel.
Example 4
[0166] Appropriate amount of synthesised T-shape acrylate macrodiol
(Ib) prepared in Example C of varying MW (20,000-100,000) was
accurately weighed in a Petri dish and mixed thoroughly using a
spatula with required weight percentage (w/w) of different
photoinitiators such as Irgacure 819, Irgacure 2022 (varying
percentage from 0.25%-2% w/w) in .about.1 ml of toluene and placed
in the UV chamber (UV lamp, varying wavelength) to cure in few
minutes. A good gel with softness varying as a function of the
acrylate molecular weight was obtained.
Example 5
[0167] The gels were prepared in two steps; preparation of
prepolymer by reacting a difunctional polyol with a diisocyanate to
get desired NCO index (NCO/OH) followed by reaction of pre-polymer
with synthesised hydroxyethoxypropyl terminated
9.09%-(hydroxyethoxypropyl methyl siloxane) (dimethyl siloxane)
copolymer (T-shape Triol)(Ia) (MW 20,000-50,000) prepared in
Example A.
Preparation of Prepolymer
[0168] The PDMS (MW 1000) was degassed at 70.degree. C. under
vacuum prior to synthesis. Molten MDI was placed in a three necked
round bottom flask which was fitted with a mechanical stirrer and
nitrogen inlet. The flask was placed in an oil bath set at
70.degree. C. The degassed PDMS was added to MDI and was stirred by
mechanical stirrer under a nitrogen atmosphere for 2 hours.
[0169] After completion of the addition of PDMS, the temperature of
the oil bath was increased to 80.degree. C. The prepolymer stirred
at 100 rpm under nitrogen atmosphere for 2 h. The prepolymer was
degassed for 1 hour under vacuum.
Reaction with Multifunctional Polyol
[0170] The prepolymer and T-shape triol (Ia) were stirred
mechanically with and without catalyst for 5 min at room
temperature and allowed to cure.
TABLE-US-00004 Pre- T- polymer Triol T-Triol Catalyst (g) Mwt. (g)
(drops) 2.75 20000 27.25 -- 1.89 30000 28.11 1 1.44 40000 28.56 1
1.16 50000 28.84 1
Example 6
[0171] In another example using UV curing, the molten MDI was
placed in a three necked round bottom flask which was fitted with a
mechanical stirrer and nitrogen inlet. The flask was placed in an
oil bath set at 60.degree. C. The synthesised T-shape acrylate
macrodiol (Ib) prepared in Example C of varying Mw 1000-100000) was
added to MDI and stirred by mechanical stirrer under a nitrogen
atmosphere for 2 h and was degassed for 1 h under vacuum. The chain
extended polymer accurately weighed in a pedri dish and mixed
thoroughly using a spatula with required weight percentage (w/w) of
different photoinitiators such as Irgacure 819, Irgacure 2022
(varying percentage from 0.25%-2% w/w) in .about.1 ml of toluene
and placed in the UV chamber (UV lamp, varying wavelength) to cure
in few minutes.
Example 7
[0172] Using one step procedure, 5 g of vinyl siloxane prepolymers
I(d), I(e) and/or I(f) prepared in Example E are mixed with an
initiator and cured with an external energy source such as UV
radiation, thermal energy depending on the initiator employed. The
photoinitiators employed include Irgacure 819, Irgacure 2020,
Irgacure 2022 and Dragacure 1173. Free radical initiators employed
include benzoyl peroxide and cumyl peroxide.
[0173] UV Curing:
[0174] For the process of curing with ultra-violet light, to 5 g of
vinyl siloxane prepolymers a photoinitiator was added, mixed
thoroughly and this in the presence of an externally supplied, long
wavelength, ultraviolet radiation cured to a cross linked gel.
[0175] Thermal curing:
[0176] For the process of temperature curing, to 5 g of vinyl
siloxane prepolymers a free radical initiator was added, mixed
thoroughly and this when cured in the oven maintained at 70.degree.
C. yielded a cross linked gel.
Example 8
[0177] The synthesised T-shape triepoxy siloxane (Id) prepared in
Example F and diamine/HMWt. siloxane diamine were mechanically
mixed for .about.5 min at room temperature and cured in the oven at
70.degree. C. A soft elastic gel with good rheological properties
was obtained.
TABLE-US-00005 T Tri- Ethylene Ethylene MW of T- epoxy
diamine/HMWt. diamine/HMWt. tri-epoxy siloxane Aminosiloxane
Aminosiloxane siloxane (Moles) MW (Moles) 20000 2 60.1 3 20000 2
248.52 3 20000 2 603.91 3
Example 9
Cytotoxicity Study Using the Iso-Elution Method
Purpose
[0178] To evaluate the biocompatibility of a test article extract
using an in vitro mammalian cell culture test. This study is based
on the requirements of the International Organization for
Standardization 10993; Biological Evaluation of Medical Devices,
Part 5: Tests for Cytotoxicity: in vitro Methods.
Ratio of Test Material to Extraction Vehicle:
[0179] Material thickness less than 0.5 mm-ratio of 60 cm.sup.2:1O
ml (based on the USP ratio 120 cm.sup.2:20 ml)
Extraction Vehicles:
[0180] Single strength Minimum Essential Medium supplemented with
5% serum and 2% antibiotics (lx MEM)
Extraction Conditions:
[0181] The extraction conditions shall attempt to exaggerate the
clinical use conditions so as to define the potential toxicological
hazard; however, they should not in any instance cause physical
changes such as fusion or melting, which results in a decrease in
the available surface area. A slight adherence of the pieces can be
tolerated.
Control Articles:
[0182] Negative Control: high density polyethylene, will be
prepared based on a ratio of 60 cm.sup.2:20 ml extraction vehicle.
A single preparation of the material will be made, and will be
extracted using the same conditions as described for the test
article.
[0183] Reagent Control: A single aliquot of the extraction vehicle
without test material will be prepared using the same conditions as
described for the test article.
[0184] Positive Control: Current positive control material*, tin
stabilized at polyvinylchoride, will be prepared based on a ratio
of 60 cm.sup.2:20 ml extraction vehicle. A single preparation of
the material will be made and extracted at 37.degree. C. for. 24
hours. Serial dilutions will be prepared for an end-point titration
procedure. [0185] *NOTE: The current positive control material has
been qualified as an acceptable replacement for the USP recommended
control material.
Test System and Justification:
[0186] Mammalian cell culture monolayer, L-929, mouse fibroblast
cells, (ATCC CCL 1, NCTC Clone 929, of strain L, or equivalent
source), will be used. In vitro mammalian cell culture studies have
been used historically to evaluate cytotoxicity of biomaterials and
medical devices (Wilsnack, et al., 1973).
Test System Management:
[0187] L-929, mouse fibroblast cells, (ATCC CCL 1, NCTC
[0188] Clone 929, of strain L, or equivalent source) will be
propagated and maintained in open wells containing single strength
Minimum Essential Medium supplemented with 5% serum and 2%
antibiotics (lx MEM) in a gaseous environment of 5% carbon dioxide
(CO.sub.2). For this study, 10 cm.sup.2 wells will be seeded,
labelled with passage number and date, and incubated at 37.degree.
C. in 5% CO to obtain confluent monolayers of cells prior to use.
Aseptic procedures will be used in the handling of the cell
cultures following approved Standard Operating Procedures.
Methods and Route of Administration:
[0189] Each culture well will be selected which contains a
confluent cell monolayer. The growth medium in triplicate cultures
will be replaced with 2 ml of the test extract. Similarly,
triplicate cultures will be replaced with 2 ml of the reagent
control, negative control extract and the undiluted and each titer
of the positive control. Each well will be incubated at 37.degree.
C. in 5% CO.sub.2 for 48 hours.
[0190] Following incubation, the cultures will be examined
microscopically (100.times.) to evaluate cellular characteristics
and percent lysis.
Evaluation Criteria and Statistics:
[0191] The confluency of the monolayer will be recorded as (+) if
present and (-) if absent. In addition, the color of the test
medium will be observed and compared to the negative control
medium. Each culture well will be evaluated for percent lysis and
cellular characteristics using the following criteria:
TABLE-US-00006 Grade Reactivity Observations 0 None Discrete
intracytoplasmic granules No lysis 1 Slight Not more than 20% of
the cells are round, Not more than 20% lysis loosely attached, and
without intracytoplasmic granules 2 Mild Not more than 50% of the
cells are round Not more than 50% lysis. and devoid of
intracytoplasmic granules 3 Moderate Not more than 70% of the cell
monolayer Not more than 70% lysis contains rounded cells 4 Severe
Nearly complete destruction of the cell Greater than 70% lysis
monolayer
[0192] For the test to be valid, the reagent control and the
negative control must have a reactivity of none (grade 0) and the
positive control must be a grade 3 or 4. The test sample meets the
requirements of the test if the biological response is less than or
equal to grade 2 (mild). The test will be repeated if the controls
do not perform as anticipated and/or if all three test wells do not
yield the same conclusion.
REFERENCES FOR EXAMPLE 9
[0193] 21 CFR 58 (GLP Regulations). [0194] International
Organization for Standardization 10993: Biological Evaluation of
Medical Devices, Part 5: Tests for Cytotoxicity: in vitro Methods.
[0195] United States Pharmacopeia (USP), current edition. [0196]
Wilsnack, R. E., "Quantitative Cell Culture Biocompatibility
Testing of Medical Devices and Correlation to Animal Tests" Rio
materials, Medical Devices and Art/Icfal Organs 4 (1976): 235-261.
[0197] Wilsnack R. B., P. S. Meyer and 3.0. Smith, `Human Cell
Culture Toxicity Testing of Medical Devices and Correlation to
Animal Tests,` Biomaterials, Medical Devices and Artificial Organs
1(1973): 543-562.
Example 10
Sensitization Study in the Guinea Pig
(Maximization Method)
Purpose of the Study:
[0198] The objective of the maximization test in the guinea pig is
to identify the potential for dermal sensitization. The Magnusson
and Kligman method has been effective in identifying a variety of
allergies. This study will be based on the requirements of the
International Organization for Stanardization 10993: biological
Evaluation of Medical Devides, Part 10: Tests for Irritation and
Sensization.
Test Article:
[0199] The sample will be prepared as follows: [0200] 1. Ratio of
test article extraction vehicle: [0201] Material thickness less
than 0.5 mm-ratio of 120 cm.sup.2 20 ml [0202] 2. Extraction
vehicle: [0203] 0.9% sodium chloride USP solution (SC) cottonseed
oil, NF (CSO) [0204] 3. Extraction condition: [0205] 37.degree. C.,
72 hours (.+-.2 hours)
Control Article:
[0206] The vehicle used to prepare the extract will be prepared in
the same manner as the extract (but without test article) serve as
the control measure. Untreated skin will serve as an additional
control reference for scoring dermal reactions during the challenge
phase.
Test System:
[0207] Species: Guinea pig (Cavia porcellus) [0208] Strain:
Crl:(HA) BR [0209] Source: Charles River Laboratories [0210] Sex:
No particular gender is prescribed for this test. If females are
used) they will be nulliparous and not pregnant. [0211] Body Weight
Range: 300-500 grams at identification [0212] Age: Young adults
[0213] Acclimation Period: Minimum 5 days [0214] Number of Animals:
15 (per extract) [0215] Identification Method: Ear punch
Justification of Test System:
[0216] The Hartley albino guinea pig has been used historically for
sensitization studies (Magnusson and Kilgman, 1970). The guinea pig
is believed to be the most sensitive animal model for this type of
study. The susceptibility of the Hartley strain to a known
sensitizing agent, 1-chloro-2,4-dinitrobenzene (DNCB) has been
substantiated with this method.
Test and Control Article Preparation:
[0217] Fresh extracts will be prepared at each phase of the study
as previously indicated (see Test Article). If the test material is
suitable for patching, a topical application of the test sample (2
cm.times.2 cm patch) will be used at the challenge. The vehicle
used to prepare the extract will be prepared in the same manner as
the extract (but without test article) to serve as the control
measure.
Methods and Route of Administration:
[0218] The day prior to treatment, 15 guinea pigs per extract (10
test, 5 control) will be weighed and identified. The fur from the
dorsoscapular area of the animals will be removed with an electric
clipper.
Induction I:
[0219] Three pair of intradermal injections will be administered to
the animals within an approximate 2 cm.times.4 cm area the
dorsoscapular region as follows:
[0220] Control Animals: [0221] a. 0.1 ml of 50:50 (v/v) mixture of
Freund's Complete Adjuvant (FCA) and the chosen vehicle [0222] b.
0.1 ml of vehicle [0223] c. 0.1 ml of a 1:1 mixture of the 50:50
(v/v) FCA and the vehicle
Test Animals:
[0223] [0224] a. 0.1 ml of 50:50 (v/v) mixture of FCA and the
chosen vehicle [0225] b. 0.1 ml of test extract [0226] c. 0.1 ml of
a 1:1 mixture of the 50:50 (v/v) FCA and the test extract
[0227] To minimize tissue sloughing the "a" and "c" injections will
be slightly deeper than "b". Site "c" will be injected slightly
more caudal than site "b".
Induction II:
[0228] Six days later, the injection sites will be clipped free of
fur again and treated with 0.5 to 1 g of a 10% (w/w) sodium lauryl
sulfate (SLS) suspension prepared by mixing the powdered SLS with
petrolatum. The day following the SLS treatment, any remaining SLS
residue will be gently wiped from the area with gauze.
[0229] A 2 cm.times.4 cm filter paper patch (3MM, Whatman),
saturated with 0.3 ml of the extract preparation or vehicle, will
be applied over the same injection area and secured with a
nonreactive tape. The trunk of each animal will then be wrapped
snugly with an elastic band for 48 hours (.+-.2 hours).
Challenge:
[0230] At 13 days after unwrapping induction II wraps, the fur will
be clipped from the sides and flanks of all guinea pigs. On the
following day, a nonwoven cotton disk backed by a flexible chamber
(e.g. Hill Top Chamber.RTM.) and semiocclusive hypoallergenic tape,
will be saturated with 0.3 ml of freshly prepared test material
extract and applied to the right flank or dorsum of each animal. In
addition, the vehicle control will be patched to the left flank or
dorsum of each animal. An approximate 2 cm.times.2 cm section of
test material itself (if appropriate) will be applied to the right
flank.
[0231] The trunk of each animal will be wrapped for 24 hours (.+-.2
hours). At patch removal the sites will be wiped with gauze. At 24
hours (.+-.2 hours) after patch removal, the challenged sites and
surrounding area will be shaved. The sites will be examined for
signs of ahy irritation or sensitization reaction, as indicated by
erythema and edema at a minimum of 2 hours and a maximum of 4 hours
following the shave and at 48 (.+-.2 hours) and 72 (.+-.2 hours)
hours after removal of the dressings. Prior to scoring, each site
will be wiped gently with a 35% isopropyl alcohol gauze sponge.
[0232] Should the original challenge results prove to be equivocal,
the animals may be rechallenged with a fresh test extract and
vehicle control approximately 7 days after the first challenge
patch application. The rechallenge will be conducted in the same
manner as the challenge but at virgin sites on the opposite flank.
After the test is completed, all animals will be handled in
accordance with approved procedures.
Evaluations and Statistics:
[0233] Daily challenge scores for reactions will be recorded at 24,
48 and 72 hours after patch removal in accordance with the
following Table:
TABLE-US-00007 ERYTHEMA (ER) EDEMA (ED) Numerical Numerical
Reaction Grading Reaction Grading No erythema 0 No edema 0 Slight
erythema 1 Slight edema 1 Well-definded erythema 2 Well-defined
edema 2 Moderate erythema 3 Moderate edema 3 Severe erythema to 4
Severe edema 4 slight eschar formulation
[0234] Any other observation relating to the site will be
footnoted.
[0235] The responses will be compared within the test animal group
and between test and control conditions. Control conditions are (1)
the vehicle control solution on the test animals and (2) the test
extract, control solution and biomaterial (if applied) on the
control animals.
[0236] In the final analysis of data, consideration will be given
to the overall pattern, intensity, duration, and character of
reactions of the test as compared to the control conditions.
Statistical manipulation of data is not applicable to this study.
An effect interpreted as "irritation" is generally observed at 24
hours, but diminishes thereafter, and is also concurrently present
as a transient response in the control animals. Closed patches
typically show maximal sensitization readings 48 to 72 hours after
patch removal in the test condition but not in the control
condition. Grades of 1 or greater in the test group generally
indicate sensitization, provided that grades of less than 1 are
observed on the control animals. If grades of 1 or greater are
noted on control animal then the reactions of test animals which
exceed the most severe control reaction are considered to be due to
sensitization.
[0237] Background or artifactual reactions (e.g., from fur
clipping, patch chamber edge, nonspecific FCA effects) will not be
considered as evidence of a sensitization response. The treatment
with FCA and occlusive dressings may lower the threshold level for
skin irritation.
[0238] If the test group has a greater number of animals showing
responses that are not greater than the control animals, a
rechallenge may be conducted. The rechallenge will be conducted
approximately 7 days after the first challenge at virgin sites on
the opposite flank of the animals. Absence of dermal response at
rechallenge may nullify earlier findings. Recurring observations in
at least one of the same animals verify earlier findings.
REFERENCES FOR EXAMPLE 10
[0239] 21 CFR 58 (GLP Regulations). [0240] Guide for the Care and
Use of Laboratory Animals, Institute for Laboratory Animal
Research, National Academy of Sciences (Washington: National
Academy Press, 1996). [0241] International Organization for
Standardization 10993: Biological Evaluation of Medical Devices,
Part 10: Tests for Irritation and Sensitization. [0242] Magnusson,
B. and A. Kligman, Allergic Contact Dermatitis in the Guinea Pig
(Springfield: C. H. Thomas, 192Q) [0243] OLAW, Public Health
Service Policy on Humane Care and Use of Laboratory Animals (NIH
Publication) [0244] United States Code of Federal Regulation (CFR)
9: The Animal Welfare Act.
Example 11
Acute Intracutaneous Reactivity Study in the Rabbit
Purpose:
[0245] The objective of this study is to evaluate the local dermal
irritant effects of leachables extracted from the test article
following intracutaneous injection in rabbits. This study will be
based on the requirements of the International Organization for
Standardisation 10993: Biological Evaluation of Medical Devices,
Part 30: Tests for Irritation and Sensitization.
[0246] This study will be conducted in accordance with the Detailed
information of the FDA Good Laboratory Practice (GLP) Regulations,
21CFR 58.
Test Article:
[0247] The sample will be prepared as follows: [0248] 1. Ratio of
test article to extraction vehicle: Material thickness less than
0.5 mm-ratio of 120 cm.sup.2;20 ml. [0249] 3. Extraction vehicle:
0.9% sodium chloride USP solution (SC). [0250] 4. Extraction
conditions: 37.degree. C., 72 hours (.+-.2 hours)
Control Article:
[0251] Reagent controls (extraction vehicle without test material)
will be prepared in the same way and at the same time as the test
extracts.
Test System:
[0252] Species: Rabbit (Oryctolagus cuniculus) [0253] Strain: New
Zealand White [0254] Source: Single USDA licensed supplier [0255]
Sex: No particular gender is prescribed in this test [0256] Body
Weight Range: 2.0 kg or greater at selection [0257] Age: Young
adults [0258] Acclimation Period: Minimum 5 days [0259] Number of
Animals: Three per pair of extracts [0260] Identification Method:
Ear tag
Justification of Test System:
[0261] The intracutaneous injection test in rabbits is specified in
the current ISO testing standards and has been used historically to
evaluate biomaterial extracts.
Methods and Route of Administration:
[0262] The day prior to treatment, each rabbit will be weighed and
clipped free of fur from the back and both sides of the spinal
column to yield a sufficient injection area. The clipped area of
the back will be wiped with a 70% alcohol soaked gauze pad just
before injection and allowed to dry. Due to concern with the
crowding and subsequent obscuring of injection sites, the test and
control sites will not be cranial and caudal on the same side of
the back as defined in the ISO standards. Each test extract will be
administered in five intracutaneous injections of 0.2 ml each on
the right side of each rabbit's back. Five reagent control
injections will be injected similarly on the left side of the back.
No more than two test extracts and the corresponding reagent
controls will be injected into each animal. Injections will be
about 2 cm apart. The appearance of the injection sites will be
noted immediately after injection.
[0263] Observations for erythema and edema will be noted for each
injection site at 24 (.+-.2 hours), 48 (.+-.2 hours) and 72 (.+-.2
hours) hours after injection. Reactions will be scored on a 0 to 4
basis. Other adverse changes at the injection sites will also be
noted. After the test is completed, all animals will be handled in
accordance with approved procedures. The reactions will be
evaluated according to the subjective rating scale as shown
below:
TABLE-US-00008 ERYTHEMA (ER) EDEMA (ED) 0 No erythema 0 No edema 1
Very-slight erythema (barely 1 Very-slight edema (barely
perceptible) perceptible) 2 Well-defined erythema 2 Well-defined
edema (edges of area well- defined by definite raising) 3 Moderate
erythema 3 Moderate edema (raised approximately 1 mm) 4 Severe
erythema (beet redness) to 4 Severe edema (raised approximately 1
mm, eschar formation preventing grading and extending beyond
exposure area) of erythema)
Evaluations and Statistics:
[0264] No statistical analysis of the data will be performed. For
each animal, the erythema and edema scores obtained at each time
interval will be added together and divided by the total number of
observations. This calculation will be conducted separately for
each test extract and reagent control. The score for the reagent
control will be subtracted from the score for the test extract to
obtain the Primary Irritation Score. The Primary Irritation Score
of each animal will be added together and divided by the total
number of animals. The value obtained is the Primary Irritation
Index (PII). The Primary Irritation Index is characterized by
number and description as follows: 0-0.4 (negligible), 0.5-1.9
(slight), 2.0-4.9 (moderate), 5.0-8.0 (severe). If the response in
the initial test is equivocal, additional testing may be necessary.
Any adverse reaction noted in the test extract will be compared to
the corresponding reagent control.
Report:
[0265] The final report will include a description of the methods
employed, individual dermal scores for each test and control
injection site, and the assessment of the results (Primary
Irritation Scores and the Primary Irritation Index).
Records:
[0266] Test article and reagent control preparation data, dates of
relevant activities (such as the study initiation and completion),
the appearance of each injection site immediately after injection,
individual dermal scores at 24, 48 and 72 hours, the Primary
Irritation Score, and the Primary Irritation Index will be
recorded.
REFERENCES FOR EXAMPLE 11
[0267] 21 CFR 58 (GLP Regulations). [0268] Guide for the Care and
Use of Laboratory Animals, Institute for Laboratory Animal
Research, National Academy or Sciences (Washington: National
Academy Press, 1996). [0269] International Organization for
Standardization 10993: Biological Evaluation of Medical Devices,
Part 10: Tests for Irritation and Sensitization. [0270] OLAW,
Public Health Service Policy on Humane Care and Use of Laboratory
Animals. [0271] United States Code of Federal Regulation (CFR) 9:
The Animal Welfare Act. [0272] United States Pharmacopeia (USP),
current edition.
Example 12
USP and ISO Systemic Toxicity Study Extract
Purpose:
[0273] The objective of this study is to evaluate acute systemic
toxicity of leachables extracted from the test article following a
single intravenous or intraperitoneal injection in mice. This study
will be conducted in accordance with the methods recommended by the
International Organization for Standardization 10993: Biological
Evaluation of Medical Devices, Part II: Tests for Systemic
Toxicity.
Test Article:
[0274] The sample will be prepared as follows: [0275] 1. Ratio of
test article to extraction vehicle: [0276] Material thickness less
than 0.5 mm-ratio of 120 cm.sup.2:20 ml [0277] Material thickness
greater than or equal to 0.5 mm ratio of 60 cm.sup.2:20 ml [0278]
Irregularly shaped objects and/or sponsor option-ratio of 4 g:20 ml
[0279] 2. Extraction vehicles: [0280] 0.9% sodium chloride USP
solution (SC) [0281] alcohol in saline 1:20 solution (AS) [0282]
polyethylene glycol 400 (PEG)* [0283] vegetable oil [0284] Note:
Due to the known pH of these vehicles, the pH of the test article
extracts will not be determined. *If PEG is used, the PEG test
extract and reagent control will be diluted with saline to obtain
200 mg of PEG/mI. [0285] 3. Extraction conditions: [0286]
121.degree. C., 1 hour [0287] 70.degree. C., 24 hours [0288]
50.degree. C., 72 hours [0289] 37.degree. C., 72 hours
Control Article:
[0290] Blank controls (extraction vehicle without test material)
will be prepared in the same way and at the same time as the test
extracts.
Test System:
[0291] Species: Mouse (Mus musculus) [0292] Strain: Outbred albino
[0293] Source: approved supplier [0294] Sex: No particular gender
is prescribed for this test [0295] Body Weight Range: 17-23 grams
at injection [0296] Age: No particular age is prescribed for this
test [0297] Acclimation Period: Minimum 1 day [0298] Number of
Animals: Five per extract and control [0299] Identification Method:
Ear punch
Justification of Test System:
[0300] Mice have historically been used to evaluate biomaterial
extracts. The use of albino mice injected with a single intravenous
(iV) or intraperitoneal (IP) dose of test article extract or
control blank have been suggested by the current USP and ISO for
evaluation of medical plastics.
Methods and Route of Administration:
[0301] Prior to dosing, the mice will be identified and weighed.
Five animals will each be injected with the appropriate test
extract at a dose of 50 ml/kg (SC, AS, vegetable oil) or 10 g/kg
(PEG). Five mice will be similarly injected with the corresponding
extraction vehicles. The SC and AS will be injected intravenously
via the lateral tail vein while the PEG and vegetable oil will be
injected intraperitoneally.
[0302] Mice will be observed for adverse reactions immediately
after dosing, and at 4, 24, 48 and 72 hours after injection.
Following the 72 hour observation, the animals will be weighed. Any
animal found dead will be subjected to a gross necropsy of the
viscera. After the test is completed, all animals will be handled
in accordance with approved procedures.
Evaluations and Statistics:
[0303] No statistical analysis of the data will be performed. If
during the observation period none of the mice treated with the
test extract show a significantly greater reaction than the
corresponding control mice, then the test sample meets the test
requirements. If two or more mice die, or if abnormal behavior such
as convulsions or prostration occurs in two or more mice, or if
body weight loss greater than 2 grams occurs in three or more mice,
the test sample does not meet the test requirements.
[0304] If any mice treated with the test extract show only slight
signs of toxicity and not more than one mouse shows gross signs of
toxicity or dies, a ten mouse retest may be required. If all ten
mice treated with the test extract on the repeat test show no
significant reaction greater than the control mice, then the test
sample meets the current test requirements.
Report:
[0305] The final report will include a description of the methods
employed, individual body weights, and any observations.
Records:
[0306] Test article preparation, dates of relevant activities (such
as the study initiation and completion), initial and final body
weights, and observations will be recorded.
REFERENCES FOR EXAMPLE 12
[0307] 21 CFR 58 (GLP Regulations). [0308] Guide for the Care and
Use of Laboratory Animals, Institute for Laboratory Animal
Research, National Academy of Sciences (Washington: National
Academy Press, 1996). [0309] International Organization for
Standardization 10993: Biological Evaluation of Medical Devices,
Part 11: Tests for Systemic Toxicity. [0310] OLAW, Public Health
Service Policy on Humane Care and Use of Laboratory Animals (NIH
Publication). [0311] United States Pharmacopeia (USP), current
edition.
Example 13
Rat Subchronic Intraveneous Toxicity Study
Purpose:
[0312] The objective of this study is to evaluate the subchronic
systemic toxicity of leachables extracted from the test article
following repeated intravenous injections in rats for a period of
14 consecutive days.
Test Article:
[0313] 1. Ratio of test article to extraction vehicle: [0314]
Material thickness less than 0.5 mm-ratio of 120 cm.sup.2:20 ml
[0315] Material thickness greater than or equal to 0.5 mm-ratio of
60 cm.sup.2:20 ml [0316] Irregularly shaped objects and/or sponsor
option-ratio of 4 g:20 ml [0317] 2. Extraction conditions: [0318]
121.degree. C., 1 hour [0319] 70.degree. C., 24 hours [0320]
50.degree. C., 72 hours
[0321] The extracts will be used within 24 hours of completion of
the extraction process or as directed by the sponsor.
Control Article:
[0322] A vehicle control (SC without test article) will be prepared
in the same way and at the same time as the test extract. A single
group of common control animals may be dosed when multiple test
articles are evaluated at the same time.
Test System:
[0323] Species: Rat (Rat us norvigicus) [0324] Strain:
Hla@:(SD)CVF.RTM. [0325] Source: Hilltop Lab Animals, Inc. [0326]
Sex: Ten male, ten female [0327] Body Weight Range: No particular
weight range is prescribed for this study, however, individual
pretreatment body weights will be within 20% of the group mean for
each sex [0328] Age: Approximately 6 to 8 weeks old at first
treatment [0329] Acclimation Period: Minimum 5 days [0330] Number
of Animals: Twenty [0331] Identification Method: Ear punch or
tag
Methods and Route of Administration:
[0332] No more than one day prior to the first dose, rats will be
weighed and randomly assigned to each treatment group. Ten rats
(five male, five female) will receive an injection of the test
article extract once each day for 14 consecutive days. The test
extract will be injected via the lateral tail vein at a dose of
10.0 ml/kg. The individual daily dose will be based on the weight
of each animal on the first dose day of each week. The appropriate
dose volume will be calculated to the nearest 0.1 ml. An
appropriate gauge needle attached to a disposable syringe will be
used to deliver the injection. The injection rate will be
approximately 1.0 ml/10 seconds. Animals will be dosed at
approximately the same time each day. Ten rats (five male, five
female) will be similarly injected with the control blank. The
first day of dosing will be designated as day 1.
Laboratory Observations:
[0333] 1. Animals will be observed daily for general health. Rats
will also be observed for any adverse reactions immediately after
injection. [0334] 2. Detailed examinations for clinical signs of
disease or abnormality will be conducted at randomization and on
days 8 and 15. [0335] 3. Body weights will be recorded to the
nearest whole gram prior to the first dose, on day 8, 14
(pre-fasted weight) and 15 (fasted weight). [0336] 4. In the event
of mortality, the following contingencies will apply: [0337] a.
Should any animal die during the study, a macroscopic examination
of the viscera will be conducted. Because of rapid postmortem
tissue changes in small rodents, no final body weight or blood
collection will be attempted. The organs and tissues designated in
the Terminal Procedures portion of this protocol will be collected
and fixed for histopathologic evaluation. The number of days the
animal was on test will be considered in the final evaluation.
[0338] b. Should any animal exhibit adverse clinical signs or
suffer from cage injury that for humane reasons necessitates
euthanasia, it will be subject to the Terminal Procedures. The
number of days the animal was on test will be considered in the
final evaluation.
Terminal Procedures:
[0339] At the end of the workday on day 14, the animals will be
weighed and food will be withheld for a maximum of 20 hours. On day
15, the animals will be weighed and then anesthetized by
intraperitoneal injection of ketamine hydrochloride and xylazine
(88 mg/kg+12 mg/kg) dosed at 3.0 ml/kg. The abdomen will be opened
and a blood specimen will be collected from the posterior vena
cava. The blood specimens will be forwarded to a contract
laboratory for complete blood cell count with differential and
clinical chemistry analyses. Rats will be euthanized by
exsanguination while anesthetized.
[0340] Following exsanguination, a macroscopic observation of the
viscera will be conducted. The following organs will be removed:
heart, lungs, liver, spleen, thymus, kidneys (2), adrenal glands
(2), mesenteric lymph nodes, submandibular lymph nodes, gonads (2)
and any tissue with visible gross lesions. The liver, spleen,
thyrnus, kidneys, adrenal glands and gonads will be weighed. Paired
organs will be weighed together. The tissues will be preserved in
10% neutral buffered forrnalin (NBF) until further processing. The
carcasses will be discarded.
[0341] After fixation, the tissues will be histologically processed
(embedded, sectioned and stained in hematoxylin and eosin) for
microscopic evaluation by a qualified pathologist.
Evaluation and Statistics:
[0342] Body weight data, organ weight data, organ/body weight
ratios, hematology and clinical chemistry data will be evaluated
statistically. Pre-fasted body weights will be used to determine
weight gain and the fasted body weights will be used to determine
anesthetic dosages at termination and organ/body weight ratios.
Descriptive statistics and group comparisons of data will be
accomplished using a validated statistical software package. After
screening the data for normality and equal variance, the
appropriate parametric or nonparametric tests will be performed.
Normally distributed data with equal variance will be considered
parametric and evaluated using an `unpaired t-test" for comparison
of two groups. Jf data is nonparametric, the "Mann-Whitney Rank Sum
Test" is used for two group comparisons. The data to be analyzed
will include: body weight, organ weight and hematological
parameters. The treatment groups will be used as variables.
Calculations resulting in probability (p) values less than 0.05
will be considered statistically significant. If directed by the
evaluating pathologist, statistical evaluation of pathologic
findings may be conducted.
[0343] Clinical signs of systemic illness or death will not be
analyzed statistically unless a rationale (such as frequently
observed clinical signs or emergence of a pattern) for such
analysis is apparent from these data. If the incidence of
occurrence of any one or more observations is sufficient to warrant
analysis, a chisquare test will be employed.
[0344] Data from male and female rats for body weights will be
analyzed separately until and unless a rationale exists for
combining the sexes. Body weight data will be expressed as absolute
values. Data from male and female rats for hematology parameters
will be analyzed separately unless a rationale exists for combining
the sexes. In the event of statistical significance for any
hematologic parameter, the results will be compared to a reference
range to aid in determining biological significance.
Report:
[0345] The final report will include a description of the methods
employed, clinical observations, body weight data, hematology and
clinical chemistry data, organ weight data, organ/body weight
ratios, necropsy findings, the microscopic evaluation in the
histopathology report, the statistical analyses and
conclusions.
REFERENCES FOR EXAMPLE 13
[0346] 21 CFR 58 (GLP Regulations). [0347] Guide for the Care and
Use of Laboratory Animals, Institute for Laboratory Animal
Research, National Academy of Sciences (Washington: National
Academy Press, 1996). [0348] ISO 10993-11. Biological Evaluation of
Medical Devices, Part 11: Tests for Systemic Toxicity. [0349] OECD
Guideline for Testing of Chemicals, Repeated Dose Oral
Toxicity--Rodent: 28-day or 14-day Study, Document Number 407.
[0350] OLAW, Public Health Service Policy on Humane Care and use of
Laboratory Animals (NIH Publication).
Example 14
Genotoxicity: Bacterial Reverse Mutation Study
Purpose of the Study:
[0351] The purpose of the study is to evaluate whether an extract
of the test material or a solubilized material will cause mutagenic
changes in a tryptophan-dependent strain of Escherichia coli or in
one or more strains of histidine-dependent Salmonella typhimurium
in the presence or absence of 59 metabolic activation. The
Bacterial Reverse Mutation Study will be used as a rapid screening
procedure for the determination of inutagenic and potential
carcinogenic hazards and should be used in conjunction with other
tests that characterize potential genotoxicity properties. This
study will be based on OECD guidelines and the requirements of the
International Organization for Standardization: Biological
Evaluation of Medical Devices--Part 3: Tests for Genotoxicity,
Carcinogenicity and Reproductive Toxicity.
Test Article:
[0352] The sample will be prepared as follows:
Test Article Form:
[0353] Soluble material (solid or liquid)--complete "Preparation of
Soluble Material" [0354] Insoluble material--complete "Preparation
of Extract" Preparation of Extract (for insoluble materials):
[0355] 1. Ratio of test material to vehicle: [0356] Material
thickness less than 0.5 mm, use ratio of 120 cm.sup.2:20 ml [0357]
Material thickness greater than or equal to 0.5 nun, use ratio of
60 cm.sup.2:20 ml [0358] Irregularly shaped objects and/or sponsor
option, use ratio of 4 g:20 ml [0359] 2. Vehicle: [0360] 0.9%
Sodium Chloride for Injection, USP [0361] Dimethyl sulfoxide
(DMSO)* [0362] 95% ethanol (EtOH)** *Dimethyl sulfoxide can be
extracted at 37.degree. C. for 72 hours, 70.degree. C. for 24 hours
or 50.degree. C. for 72 hours. **95% ethanol can only be extracted
at room temperature (various times can be used). [0363] 3.
Conditions (use highest temperature that will not degrade
material); [0364] 121.degree. C., 1 hour [0365] 70.degree. C., 24
hours [0366] 50.degree. C., 72 hours [0367] 37.degree. C., 24 hours
[0368] room temperature, 72 hours
Preparation of Soluble Material:
[0368] [0369] 1.--Solid: [0370] One gram of the sample will be
transferred to a 10 ml volumetric flask. Various sized flasks may
be used to accommodate nature of test material utilizing 100 mg/ml
or 10% w/v. Appropriate vehicle (specified below) will be added
(q.s.) to the 10 ml (or appropriate) demarcation to achieve 100
mg/ml or a 10% (w/v) solution of the material. [0371] 2.--Liquid:
[0372] One milliliter of the sample will be transferred to a 10 ml
volumetric flask. Various sized flasks may be used to accommodate
nature of test material utilizing 100 mg/ml or 10% v/v. Appropriate
vehicle (specified below) will be added (q.s.) to the 10 ml (or
appropriate) demarcation to achieve 100 mg/ml or a 10% (v/v)
solution of the material. [0373] NOTE: GLP regulations 21 CFR
58.113 requires concentration analysis and stability determination
for mixtures with carriers.
Vehicles:
[0373] [0374] 0.9% Sodium Chloride for Injection, USP [0375]
Dimethyl sulfoxide (DMSO) [0376] 95% ethanol (EtOH)
[0377] All preparations of soluble materials will be performed the
day of test. In the event the material does not completely dissolve
at these concentrations, serial dilutions will be prepared. The
highest possible concentration that achieves complete dissolution
of the material will be used for testing purposes.
Test System:
[0378] Each S. typhimurium tester strain contains a specific
mutation in the histidine operon and other mutations that increase
their ability to detect mutagens. The E. coli strain contains a
mutation in the tryptophan operon and a deletion in the uvrA gene.
These genetically altered S. typhimurium strains (TA9S, TA100,
TA1535, and TA1537) and E. coli strain (WP2uvrA) cannot grow in the
absence of histidine or tryptophan, respectively. When placed in a
histidine-free (for S. typhimurium) or tryptophan-free (for E coli)
medium, only those cells which mutate spontaneously back to their
wild type state (histidine independent by manufacturing their own
histidine, or tryptophan independent by manufacturing their own
iryptophan) are able to form colonies. The spontaneous mutation
rate (or reversion rate) for any one strain is relatively constant,
but if a mutagen is added to the test system, the mutation rate is
significantly increased.
Tester Strain Mutations/Genotypic Relevance
[0379] S. typhimurium TA98 hisD3O52, rfa, uvrB, frameshift, pKM101
[0380] S. typhimurium TA 100 hisG46, rfa, uvrB, missense, pKM101
[0381] S. typhimurium TA 1535 hisG46, rfa, uvrB, missense [0382] S.
typhimurium TA 1537 hisC3O76, rfa, uvrB, frameshift [0383] E. coli
WP2uvrA trpE65, uvrA, missense [0384] rfa=causes partial loss of
the lipopolysaccharide wall which increases permeability of the
cell to large molecules (i.e., crystal violet inhibition) [0385]
uvrB or uvrA=deficient DNA excision--repair system (i.e.,
ultraviolet sensitivity) [0386] frameshift=base-pair
addition/deletion [0387] missense=base-pair substitution [0388]
pKM101=plasmid confers ampicillin resistance (R-factor) and
enhances sensitivity to mutagens
Metabolic Activation:
[0389] Aroclor 1254--induced rat liver (s9 homogenate) will be used
as metabolic activation. The material is prepared from male,
Sprague Dawley rats. The rats are induced with one intraperitoneal
injection of Aroclor 1254 (500 mg/ml) 5 days prior to sacrifice.
The S9 homogenate is purchased from Organon Teknika Corporation,
Box 15969, Durham, N.C. 27704-0969. Just prior to use, the S9
homogenate will be mixed with a buffer containing 0.4 M
MgCl.sub.2/65 M KCl, 1.0 M Glucose-6-phosphate, 0.1 M NADP, 0.2 M
sodium phosphate buffer and sterile water.
Preparation of Tester Strains:
[0390] Cultures of Salmonella typhimurium, TA98, TA100,
[0391] TA1535 and TA1537, and Escherichia coli, WP2uvrA, will be
inoculated to individual Erlenmeyer flasks containing oxoid broth.
The inoculated broth cultures will be incubated at 37.+-.2.degree.
C. in an incubator shaker operating at 115-125 rpm for 10-12
hours.
Preparation of Negative Control:
[0392] Negative control (vehicle without test material) will be
utilized for each tester strain with and without S9 activation.
Preparation of Positive Controls:
[0393] A known mutagen, Dexon (paradimethylaminobenzene
diazosulfonic acid sodium salt), will be used as a positive control
to demonstrate that tester strains TA98, TA100, and TA1537 are
sensitive to mutation to the wild type state. For tester strain TA
1535, sodium azide will be used as a positive control. For tester
strain TA100, 2-aminofluorene will be used as a positive control.
For tester strain WP2uvrA, 2-aminoanthracene and
methylmethane-sulfonate will be used as positive controls. Although
metabolic activation is only required with 2-aminofluorene and
2-aminoanthracene to induce mutagenic results, all positive
controls will be tested with and without S9 homogenate.
Strain Characteristics and Strain Standard Plate Counts:
[0394] Strain characteristics will be verified and viable counts
will be determined.
Spot Plate Inhibition Screen:
[0395] The extract(s) or solubilized material(s) and negative
control(s) will be evaluated by a spot plate technique modeled
after the antimicrobial zone of inhibition test. This screen is
used to evaluate extract or solution concentrations for toxicity
which are noninhibitory to the Salmonella strains and the E. coli
strain.
[0396] Separate tubes containing 2 ml of molten top agar
supplemented with histidine-biotin (for S. typhimurium) or with
tryptophan (for E. coli) will be inoculated with 0.1 ml of culture
for each of the five tester strains. After mixing, the agar will be
poured across the surface of separate Minimal E plates labeled with
lab number, appropriate tester strain, and dose level (when
necessary). Once the agar solidifies, sterile filter discs will be
placed in the center of the plates. A 0.1 ml aliquot of the extract
or solubilized material will be added to the filter discs on each
of the labeled plates. Parallel testing will be conducted with a
negative control. To demonstrate a positive zone of inhibition,
10.times. stock Dexon will be used.
[0397] The plates will be incubated at 37.+-.2.degree. C. for 2-3
days. Following the incubation period, the zone of growth
inhibition will be recorded. If significant inhibition of the
background lawn occurs, the extract or solubilized material
concentration will be adjusted by preparing one or more dilutions
and repeating the inhibition screen to find a nontoxic level.
Standard Plate Incorporation Assay:
[0398] Separate tubes containing 2 ml of molten top agar
supplemented with histidine-biotin solution (for S. typhimurium) or
tryptophan (for E. coli) will be inoculated with 0.1 ml of culture
for each of the five tester strains, and 0.1 ml of the test
material. A 0.5 ml aliquot of SWI or S9 homogenate, simulating
metabolic activation, will be added when necessary. The mixture
will be poured across triplicate Minimal B plates labeled with lab
number, appropriate tester strain, and S9 metabolic activation
(when applicable). Parallel testing will be conducted on a negative
control and five positive controls.
[0399] Histidine-free media plates (for S. typhimurium) and
tryptophan-free media plates (for E. coli) will be prepared in
triplicate as follows: [0400] 1. Extract or solubilized material
with and without S9 activation [0401] 2. Negative control with and
without S9 activation [0402] 3. 1.times. Dexon (known mutagen) with
and without S9 activation with strains TA9S, TA100, and TA1 537
[0403] 4. 1.times. 2-aminofluorene (known mutagen) with and without
S9 activation with strain TA 100 [0404] 5. 1.times. Sodium azide
(known mutagen) with and without S9 activation with strain TA1535
[0405] 6. 1.times. 2-aminoanthracene (known mutagen) with and
without S9 activation with strain WP2uvrA [0406] 7. 1.times.
Methylmethane-sulfonate (known mutagen) with and without S9
activation with strain WP2uvrA
[0407] The plates will be incubated at 37.+-.2.degree. C. for 2-3
days. After the incubation period, the revertant colonies on each
plate (test, negative and positive) will be counted and recorded.
The mean number of revertants will be calculated.
Evaluation of Test Results:
[0408] The mean number of revertants of the triplicate test plates
will be compared to the mean number of revertants of the triplicate
negative control plates for each of the five tester strains
employed. The means obtained for the positive controls are used as
points of reference. For a test material to be identified as a test
failure or "potential mutagen" there must be a 2-fold or greater
increase in the number of mean revertants over the means obtained
from the negative control, for any/all five tester strains. If no
2-fold increase is present, the test material is considered
nonmutagenic.
[0409] Any apparent "positive response" will be confirmed by
demonstrating a dose-response relationship using three nontoxic
dose levels of the test material. There should be a range of
concentrations that produce a linear dose response. In the event
linearity cannot be established, the assay will be repeated with an
appropriate change in dose levels. A test material will be judged
mutagenic if it causes a dose-related increase in the number of
revertants over a minimum of two increasing dose
concentrations.
Test Validity:
[0410] For any assay to be considered valid, it must meet the
following criteria: [0411] 1. Strain characteristics: All S
typhimurium tester strains (TA98, TA100, TA1535, and TA1537) must
exhibit sensitivity to crystal violet (rfa mutation), and
ultraviolet light (uvrB), and must exhibit no growth on biotin
plates, and growth on histidine-biotin plates. Tester strains TA98
and TA 100 must exhibit resistance to ampicillin (R-factor); tester
strains TA1535 and TA1537 must exhibit sensitivity to ampicillin.
Tester strain WP2uvrA must exhibit sensitivity to ultraviolet
light, no growth on tryptophan deficient plates, growth on
tryptophan supplemented media and sensitivity to ampicillin. [0412]
2. Strain Standard Plate Counts: A viable count on the working
culture suspensions for each tester strain (TA98, TA100, TA1535,
TA1537 and WP2uvrA) should not be less than 1.times.10 CFU/ml.
[0413] 3. Spot Plate Inhibition Screen: Each prepared extract or
solubilized material will be evaluated for inhibition or toxicity
to the cells. A test sample that is noninhibitory to moderately
noninhibitory to the tester strains will be tested by the standard
plate incorporation method. In the event a test material is
inhibitory, dilutions will be required to find a nontoxic level.
[0414] 4. Standard Plate Incorporation Assay: Each positive control
mean must exhibit at least a 3-fold increase over the respective
negative control mean of the Salmonella tester strain employed, and
at least a 2-fold increase over the respective negative control
mean of the E. coli tester strain. Exceptions include conditions
not intended to provoke a mutagenic response (e.g.
2-aminoanthracene and 2-aminofluorene without metabolic
activation). The negative control results of each tester strain
will exhibit a characteristic number of spontaneous revertants.
Spontaneous reversion rates may vary, but should be consistent with
the ranges specified (see Table below). The Table is meant as a
guideline only. Negative control results for tester strains may
fall outside of the range listed. In such an instance, the results
should be evaluated with caution.
TABLE-US-00009 [0414] Number of Spontaneous Species Tester Strain
Revertants S. typhimurium TA98 15-50 TA100 120-240 TA1537 3-28
TA1535 10-35 E. coli WP2uvrA 20-125
REFERENCES FOR EXAMPLE 14
[0415] Ames, B. N., McCann, 3., and Yamasaki, E., "Methods for
Detecting Carcinogens and Mutagens with the [0416]
Salmonella/Mammalian-Microsome Mutagenicity Test" Mutation Research
31, (1975): 347-364. [0417] Brusick, D. J., V. F. Simmon, H. S.
Rosenlcranz, V. A. Ray, and KS. Stafford, "An Evaluation of the
Escherichia coli WP2 and WP2uvrA Reverse Mutation Assay," Mutation
Research 76, (1980): 169-190. [0418] Maron, Dorothy M., Ames, Bruce
N., "Revised Methods for the Salmonella Mutagenicity Test,"
Mutation Research, 113 (1983): 175-215. [0419] ISO 10993-3.
Biological Evaluation of Medical Devices, Part 3: Tests for
Genotoxicity, Carcinogenicity and Reproductive Toxicity. [0420]
OECD Guideline for the Testing of Chemicals, Proposal for
Replacement of Guidelines 471 Bacterial Reverse Mutation Test,
Document Number 471. [0421] Ortiz, A. J., M. T. Pollastrini, M.
Barea, and D. Ordahez, "Bacterial Mutagenic Evaluation of
Luxabendazole, a New Broad Spectrum Antihelminic, with the
Salmonella typhimurium Histidine and the Escherichia coli
Tryptophan Reversions Tests," Mutagenesis 11(1996): 27-31. [0422]
Test validation, Bacterial Mutagenicity Test: NAMSA lab number
98T-00785-00.
[0423] It will be appreciated by persons skilled in the art that
numerous variations and/or modifications may be made to the
invention as shown in the specific embodiments without departing
from the spirit or scope of the invention as broadly described. The
present embodiments are, therefore, to be considered in all
respects as illustrative and not restrictive.
* * * * *