Ex Parte Sawhney et al

Patent Trial and Appeal Board

Dec 14, 2012

11465791 (P.T.A.B. Dec. 14, 2012)

UNITED STATES PATENT AND TRADEMARKOFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
11/465,791 08/18/2006 Amarpreet S. SAWHNEY 3516.24US02 1874
62274 7590 12/14/2012
DARDI & HERBERT, PLLC
Moore Lake Plaza, Suite 205
1250 East Moore Lake Drive
Fridley, MN 55432
EXAMINER
BECKHARDT, LYNDSEY MARIE
ART UNIT PAPER NUMBER
1613
MAIL DATE DELIVERY MODE
12/14/2012 PAPER
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
__________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
__________

Ex parte AMARPREET S. SAWHNEY, STEVEN L. BENNETT,
SURESH S. PAI, SCOTT R. SERSHEN, and FRED H. CO
__________

Appeal 2012-001501
Application 11/465,791
Technology Center 1600
__________

Before MELANIE L. McCOLLUM, JEFFREY N. FREDMAN, and
STEPHEN WALSH, Administrative Patent Judges.

McCOLLUM, Administrative Patent Judge.

DECISION ON APPEAL
This is an appeal under 35 U.S.C. § 134 involving claims to a method
for making a hydrogel. The Examiner has rejected the claims as obvious.
We have jurisdiction under 35 U.S.C. § 6(b). We affirm-in-part.
STATEMENT OF THE CASE
Claims 1, 2, 4-9, 11, 13-16, and 46-56 are pending and on appeal
(App. Br. 3). Claims 1, 6, and 11 are illustrative and read as follows:
1. A method for making superabsorbent hydrogel, comprising:
forming a mixture by combining precursor components to initiate
covalent crosslinking of the precursor components;
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freezing the mixture before the covalent crosslinking is complete; and
freeze drying the frozen mixture to form the hydrogel,
wherein the precursor components comprise a first electrophilic
precursor that comprises electrophilic functional groups and a second
nucleophilic precursor that comprises nucleophilic functional groups chosen
from the group consisting of amines and thiols, with the electrophilic
functional groups and nucleophilic functional groups chemically reacting
with each other to form covalent bonds to crosslink the precursor
components.
6. The method of claim 1, further comprising placing the combined
precursor components onto a chilled tray or container before freezing the
mixture.
11. The method of claim 1, wherein crosslinking of the precursor
components is initiated in an aqueous phase.
Claims 1, 2, 4-9, 11, 13-16, 46-51, 55, and 56 stand rejected under
35 U.S.C. § 103(a) as obvious over Pathak et al. (US 2003/0012734 A1,
Jan. 16, 2003) in view of Chang et al. (US 5,955,549, Sep. 21, 1999),
Unger et al. (US 5,541,234, Jul. 30, 1996), and Delmotte (US 6,599,515 B1,
Jul. 29, 2003) (Ans. 4).
Claims 52-54 stand rejected under 35 U.S.C. § 103(a) as obvious over
Pathak in view of Chang, Unger, Delmotte, and Maa et al. (US
2002/0120228 A1, Aug. 29, 2002) (Ans. 9-10).
I
The Examiner relies on Pathak for teaching
a hydrogel made by forming a mixture by combining precursor
components to initiate covalent crosslinking of the precursor
components . . . wherein the precursor components comprise a
first electrophilic precursor that comprises electrophilic
functional groups and a second nucleophilic precursor that
comprises nucleophilic groups chosen from the group
consisting of amines and thiols, with the electrophilic functional
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groups and the nucleophilic functional groups chemically
reacting with each other to form . . . covalent bonds to crosslink
the precursor components (4 arm succinimidyl glutarate PEG
with di, tri or tetra lysine . . . ).
(Ans. 4-5.)
The Examiner relies on Chang for teaching “a method for making a
superabsorbent hydrogel . . . comprising forming a mixture by combin[in]g
precursor components to initiate covalent crosslinking of the precursor
components, freezing the mixture before the covalent cross-linking is
complete and freeze drying the frozen mixture to form the hydrogel” (id. at
5).
The Examiner relies on Unger for teaching “placing the freeze dried
hydrogel in cross-linking solvent” (id. at 7). The Examiner also relies on
Unger for teaching “that porous bodies exhibiting properties such as low
density and high surface volume, high pore volume as well as excellent
strength were known properties . . . and made by processes including
gelling, freeze drying, followed by subsequent cross-linking” (id. at 11).
The Examiner relies on Delmotte for teaching “making a porous
structure having good resistance to compression and a porosity formed by
large cells . . . made by a process of partially cross-linking followed by
freeze drying” (id.).
The Examiner concludes:
It would have been obvious to one of ordinary skill in the art at
the time the invention was made to subject the precursor
hydrogel materials taught by [Pathak] to freeze drying after
brief agitation as taught by [Chang] in order to obtain a
superabsorbent hydrogel containing porosity . . . because
[Pathak] teaches the hydrogel [is] used for devices such as
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wound dressing, scaffold for cellular growth for tissue
engineering and drug release . . . and [Delmotte] teaches larger
pores can be used to support a skin layer and for the suitable
attachment of cells on the structure. . . . One of ordinary skill in
the art at the time the invention was made would have a
reasonable expectation of success in using the process of freeze
drying followed by further cross-linking . . . because [Chang,
Unger, and Delmotte] . . . are all directed to hydrogels which
are subjected to the freeze drying process.
(Id. at 8-9.) The Examiner finds that “when the hydrogel taught by [Pathak]
is subjected to the method steps taught by [Chang] superabsorbancy would
result” (id. at 12).
Findings of Fact
1. Pathak discloses “a hydrogel for use on a substrate such as a
patient’s tissue,” wherein the “hydrogel has water . . . and reactive
hydrophilic polymers that form a crosslinked hydrogel after contact with the
tissue” (Pathak, ¶ [0009]).
2. In particular, Pathak discloses that “[m]ethods for using the
polymeric compositions to coat a tissue include mixing hydrophilic
precursor polymers with chemically distinct reactive functional groups such
that they form crosslinks via nucleophilic-electrophilic reaction after mixing
and contact with the tissue” (id. at ¶ [0012]).
3. Pathak also discloses:
Preferably, each precursor comprises only nucleophilic or only
electrophilic functional groups, so long as both nucleophilic and
electrophilic precursors are used in the crosslinking reaction.
Thus, for example, if a crosslinker has nucleophilic functional
groups such as amines, the functional polymer may have
electrophilic functional groups such as N-hydroxysuccinimides.
On the other hand, if a crosslinker has electrophilic functional
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groups such as sulfosuccinimides, then the functional polymer
may have nucleophilic functional groups such as amines or
thiols.
(Id. at ¶ [0057].)
4. In addition, Pathak discloses “methods for using biocompatible
crosslinked polymers to form medically useful devices or implants for use as
surgical adhesion prevention barriers, as implantable wound dressings, as
scaffolds for cellular growth for tissue engineering or as surgical tissue
adhesives or sealants” (id. at ¶ [0021]).
5. Pathak also discloses that the “biocompatible crosslinked
polymers and their precursors described above may be used in a variety of
applications, such as components of tissue adhesives, tissue sealants, drug
delivery vehicles, wound covering agents, barriers in preventing
postoperative adhesions, and others” (id. at ¶ [0133]).
6. Chang “relates to crosslinked poly(amino acids),” specifically
“to the use of polyaziridines and polyepoxides as crosslinkers for poly
(amino acids) to produce superabsorbent polymers under aqueous conditions
without handling hydrogel intermediates” (Chang, col. 1, ll. 8-14).
7. To prepare the crosslinked poly(amino acids), Chang discloses:
An aqueous solution of one or more poly(amino acid)
backbone polymers, adjusted to the desired pH range, is placed
in a reaction vessel and an aqueous solution of the crosslinking
agent is added to the reaction mixture with agitation at ambient
temperature . . . up to about 80° C. (step (a)). After brief
agitation, the reaction mixture is then transferred to a drying
apparatus, for example an oven or freeze-drying system, to
remove volatile components (step (b)).
Typically, the reaction mixture is frozen with an acetone-
solid carbon dioxide (dry ice) mixture . . . and subjected to
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vacuum . . . for 2 to 24 hours to remove volatiles during which
the temperature starts to approach ambient temperature. The
solid reaction product is then broken into small particulates,
preferably to a powder, and heat treated at 100 to 200° C.,
preferably from 100 to 180° C., for 15 to 90 minutes to
complete the crosslinking reaction (step (c)).
(Id. at col. 3, l. 64, to col. 4, l. 15.)
8. Chang also discloses that the “crosslinking reaction occurs
between the side chain carboxylate groups of the backbone polymer and the
reactive endgroups of the crosslinking agent” (id. at col. 3, ll. 21-24).
9. In addition, Chang discloses:
The absorbency properties and degree of crosslinking are
controlled by proper selection of the temperature, time and pH
parameters used in the preparation of the crosslinked
poly(amino acids). . . .While not wishing to be bound by theory,
we believe that . . . the disclosed pH range allows protonation
of the heteroatom in the 3-membered ring of the crosslinker,
thus activating the ring towards ring-opening nucleophilic
attack by the side chain carboxylate group of the backbone
amino acid polymer; in addition, the disclosed pH range
provides an environment where a sufficient fraction of the side
chain carboxylic acid group exists in the carboxylate form
which is required for the nucleophilic ring-opening reaction
with the crosslinker while at the same time minimizing
competing hydrolysis of the 3-membered ring in the aqueous
environment.
(Id. at col. 3, ll. 30-61.)
10. Unger discloses
porous bodies which possess a low density and a high surface
area as well as one or more other beneficial properties such as
pore volume and strength characteristics, which makes them
suitable for many industrial applications, such as insulating
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materials, fibers, absorbents, adsorbents, ion-exchange resins,
membranes and support materials for a wide variety of uses.
(Unger, col. 1, ll. 14-21.)
11. Unger also discloses
a process for making a crosslinked, highly porous body
comprising the steps of dissolving a hydrogel polymer in a
gelling solvent, forming a gel from the dissolved polymer
solution into a desired configuration, gradually replacing the
gelling solvent with a crosslinking solvent . . . , adding a
crosslinking agent to crosslink the gel, and isolating the
crosslinked gel from the crosslinking solvent.
(Id. at col. 2, ll. 25-33.)
12. In addition, Unger discloses: “Other techniques may be used to
prepare the gel for crosslinking. . . . Illustrative of such alternate techniques
are freeze-drying and supercritical fluid extraction.” (Id. at col. 9, ll. 15-22.)
13. Unger also discloses: “Freeze-drying is a well-known
procedure. . . . The material to be freeze-dried is first cooled to below the
freezing point of the solvent, followed by vacuum drying, as known in the
art.” (Id. at col. 9, ll. 26-30.)
14. In addition, Unger discloses that, “[f]ollowing freeze-drying or
supercritical extraction, the dried material is exposed to a crosslinking agent,
which can be provided in solution or in the gas phase, to form a crosslinked
porous body” (id. at col. 9, ll. 45-49).
15. Unger also discloses that “polymers suitable for [its] invention
are hydroxyl group-containing natural and synthetic polymers and other
synthetic polymers that form hydrogels when solubilized in water or other
aqueous solvents” (id. at col. 4, ll. 56-59).
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16. Delmotte is directed to “a fibrin porous structure having good
resistance to compression and a porosity formed by large cells” (Delmotte,
col. 1, ll. 12-14).
17. Delmotte discloses that “[t]hese large pores are suitable for the
attachment of cells of the structure” (id. at col. 1, ll. 62-64).
18. Delmotte also discloses that its structure “can be used as
support for a skin layer” (id. at col. 2, ll. 19-22).
19. In addition, Delmotte discloses a process for preparing the
porous structure, comprising: “(1) providing a solution containing fibrin or
fibrinogen materials . . . , (2) polymerizing the fibrin or fibrinogen,
preferably a polymerization with at least partial cross-linking of the fibrin or
fibrinogen materials in the presence of a calcium blocking or inhibiting
agent (preferably an anticoagulant), and (3) lyophilizing the polymerized
fibrin or fibrinogen.” (Id. at col. 2, ll. 30-38.)
20. Delmotte also discloses that, “after the partial polymerization
with at least partial cross-linking of the fibrin or fibrinogen materials, but
before the lyophilization step, the polymerized material . . . advantageously
forms a hydrogel” (id. at col. 11, ll. 26-29).
21. In addition, Delmotte discloses that the polymerization is
conducted in the presence of thrombin, which acts as a catalyst (id. at
col. 14, ll. 47-49, & col. 1, ll. 25-26).
Analysis
Claim 1 is directed to a method for making superabsorbent hydrogel.
However, the body of the claim suggests that this is merely the intended
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result of performing the claimed steps. Thus, we agree with the Examiner’s
conclusion to give the preamble no patentable weight (Ans. 12).
Pathak discloses a method for making a hydrogel comprising forming
a mixture by combining precursor components comprising an electrophilic
precursor that comprises electrophilic functional groups and a nucleophilic
precursor that comprises nucleophilic functional groups chosen from amines
and thiols, with the electrophilic functional groups and nucleophilic
functional groups chemically reacting with each other to form covalent
bonds to crosslink the precursor (Finding of Fact (FF) 1-3). Chang, Unger,
and Delmotte each disclose freeze drying a hydrogel before crosslinking is
complete (FF 6-7, 11-14, & 19-20). In addition, Unger and Delmotte both
teach the use of freeze drying to form a porous structure (FF 10 & 16). We
conclude that the Examiner has set forth a prima facie case that it would
have been obvious to freeze Pathak’s mixture before the covalent
crosslinking is complete and freeze dry the frozen mixture in order to form a
porous structure.
Appellants argue:
[T]he Examiner merely assumes that the [Pathak] materials will
be mixed to initiate crosslinking and then be frozen before
crosslinking is complete. For instance, the Examiner assumes
that, if precursors are chosen from [Pathak], and, if a freezing
step is desired, then the freezing step would be performed not
before, not after, but during crosslinking. Nothing in the
references, however, leads the artisan to such a process.
(App. Br. 14.) Appellants also argue that Chang “does not teach and thus
does not motivate stopping cross-linking by freezing” (Reply Br. 10). We
are not persuaded.
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We agree with Appellants that Chang does not specifically recite that
crosslinking occurs before freezing. However, Chang does state that the
reaction product is heat treated in step (c) “to complete the crosslinking
reaction” (FF 7 (emphasis added)), implying that some crosslinking occurs
before step (c). Moreover, Delmotte clearly discloses freeze drying after
partial crosslinking (FF 19).
In addition, Appellants argue: Chang “teaches oven/freeze-drying to
remove water because of [Chang]’s particular chemistry. The [Pathak]
materials do not require oven/freeze-drying to remove water. Freezing at
just the right time in the process is . . . even more gratuitous.” (App. Br. 14.)
Appellants also argue that “the freeze-drying has no purpose when the
chemistry of [Chang] is discarded” (id. at 15). We are not persuaded.
As noted by the Examiner (Ans. 13), Unger and Delmotte provide the
reason to freeze dry Pathak’s mixture, namely to provide a porous structure
(FF 10 & 16). In addition, Delmotte specifically teaches freeze drying after
partial crosslinking (FF 19).
Furthermore, Appellants argue that the Examiner’s “re-engineering is
. . . not found in the prior art but is merely hindsight reconstruction of the
claimed method using the claims as a template” (App. Br. 16). Appellants
also argue that “the idea that [Delmotte] motivates engineering the [Pathak]
materials to be highly porous is purely speculative and does not meet the
Patent Office’s burden of showing obviousness” (Reply Br. 7). We are not
persuaded.
As noted by the Examiner (Ans. 8), Pathak discloses a hydrogel
having various uses, including as wound dressings, scaffolds for cellular
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growth for tissue engineering, and drug delivery vehicles (FF 1, 4, & 5).
Delmotte, as well as Unger, teaches the use of hydrogel materials to form
porous structures and that these structures have various uses (FF 16-20 &
10-11). Specifically, Delmotte discloses that its “pores are suitable for the
attachment of cells of the structure” and that the structure “can be used as
support for a skin layer” (FF 17-18). We agree with the Examiner that these
teachings provide sufficient basis to freeze dry Pathak’s materials, as
disclosed in Delmotte, Chang, and Unger.
In addition, Appellants argue that Delmotte does not teach cross-
linking after lyophilization (Reply Br. 7). We are not persuaded.
We note initially that claim 1 does not require crosslinking after
lyophilization. Moreover, both Chang and Unger teach crosslinking after
lyophilization (FF 7 & 14).
Appellants also argue that “the enzymatic processes of [Delmotte] are
not even remotely suggestive of how to suitably manipulate the claimed
electrophilic-nucleophilic covalent crosslinking chemical reactions” (Reply
Br. 8). We are not persuaded.
We recognize that Delmotte is specifically directed to the catalytic
polymerization of a fibrin or fibrinogen material (FF 19 & 21). However,
Unger discloses the use of freeze drying on a broad range of hydrogels to
provide a porous material (FF 11 & 15). In addition, Chang specifically
discloses freeze drying a hydrogel that undergoes crosslinking via
carboxylate groups, which are nucleophilic (FF 8-9). Thus, we agree with
the Examiner that it would have been obvious to utilize the known method
of freezing the mixture before the covalent crosslinking is complete and
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freeze drying the frozen mixture on Pathak’s composition in order to form a
porous material.
With regard to claims 6 and 16, Appellants additionally argue that the
Examiner has not set forth a prima facie case that the applied references, in
particular, Chang, which is relied on by the Examiner (Ans. 5), “does not
teach or suggest contact with a chilled tray or container” (App. Br. 17; see
also id. at 18-19). We agree. In particular, we are not persuaded by the
Examiner’s conclusory argument that the “selection of steps is prima facie
obvious in the absence of new or unexpected results” (Ans. 16).
With regard to claim 11, Appellants additionally argue that Chang
teaches “mixing the crosslinker in an aqueous phase, not actually cross-
linking in the aqueous phase” (App. Br. 18). We are not persuaded. As
discussed above, we agree with Appellants that Chang does not specifically
recite that crosslinking occurs (in the aqueous phase) before freezing, but
that Delmotte clearly discloses freeze drying after partial crosslinking
(FF 19). In addition, it is undisputed that Pathak discloses crosslinking in an
aqueous solution (Ans. 17).
Conclusion
The evidence supports the Examiner’s conclusion that claims 1 and 11
would have been obvious. We therefore affirm the obviousness rejection of
claims 1 and 11. Claims 2, 4, 5, and 13-15 are not separately argued and
therefore fall with claim 1. 37 C.F.R. § 41.37(c)(1)(vii).
However, the Examiner has not set forth a prima facie case that
claims 6 and 16 would have been obvious. We therefore reverse the
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obviousness rejection of claims 6 and 16 and of claims 7-9, 46-51, 55, and
56, which depend from claims 6 or 16.
II
In the second rejection, the Examiner additionally relies on Maa for
teaching the features of claims 52-54 (Ans. 10). However, the Examiner
does not find that Maa overcomes the deficiencies discussed above with
regard to claim 16, on which claims 52-54 depend. Thus, we conclude that
the Examiner has not set forth a prima facie case that claims 52-54 would
have been obvious. We therefore reverse the obviousness rejection of
claims 52-54.
SUMMARY
We affirm the rejection of claims 1, 2, 4, 5, 11, and 13-15. However,
we reverse the rejections of claims 6-9, 16, and 46-56.
TIME PERIOD FOR RESPONSE
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a).

AFFIRMED-IN-PART

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