U.S. patent application number 12/675329 was filed with the patent office on 2010-11-18 for surgical hydrogel.
Invention is credited to Theodore Athanasiadis, Lyall Robert Hanton, Stephen Carl Moratti, Brian Harford Robinson, Simon Rae Robinson, Zheng Shi, James Simpson, Peter John Wormald.
Application Number | 20100291055 12/675329 |
Document ID | / |
Family ID | 40387519 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100291055 |
Kind Code |
A1 |
Athanasiadis; Theodore ; et
al. |
November 18, 2010 |
SURGICAL HYDROGEL
Abstract
The invention provides a hydrogel suitable for use in wound
healing, particularly for reducing post-surgical adhesions. The
hydrogel comprises cross-linked derivatives of chitosan and dextran
polymers. The hydrogel forms when solutions of the polymers are
combined.
Inventors: |
Athanasiadis; Theodore;
(South Australia, AU) ; Hanton; Lyall Robert;
(Dunedin, NZ) ; Moratti; Stephen Carl; (Dunedin,
NZ) ; Robinson; Brian Harford; (Dunedin, NZ) ;
Robinson; Simon Rae; (Wellington, NZ) ; Shi;
Zheng; (Dunedin, NZ) ; Simpson; James;
(Dunedin, NZ) ; Wormald; Peter John; (South
Australia, AU) |
Correspondence
Address: |
BORSON LAW GROUP, PC
1078 CAROL LANE, #200
LAFAYETTE
CA
94549
US
|
Family ID: |
40387519 |
Appl. No.: |
12/675329 |
Filed: |
August 26, 2008 |
PCT Filed: |
August 26, 2008 |
PCT NO: |
PCT/NZ2008/000219 |
371 Date: |
August 4, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60968414 |
Aug 28, 2007 |
|
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|
Current U.S.
Class: |
424/94.1 ;
514/15.3; 514/169; 514/9.4; 536/20 |
Current CPC
Class: |
A61L 31/041 20130101;
C08B 37/0063 20130101; C08L 5/08 20130101; A61L 26/0052 20130101;
A61K 31/738 20130101; A61L 2400/04 20130101; C08L 5/08 20130101;
A61P 41/00 20180101; A61K 45/06 20130101; A61P 9/06 20180101; A61L
26/008 20130101; A61L 26/0052 20130101; A61L 31/041 20130101; A61P
17/02 20180101; A61L 31/145 20130101 |
Class at
Publication: |
424/94.1 ;
514/15.3; 514/9.4; 514/169; 536/20 |
International
Class: |
A61K 38/43 20060101
A61K038/43; A61K 38/17 20060101 A61K038/17; A61K 38/18 20060101
A61K038/18; A61K 31/56 20060101 A61K031/56; C08B 37/08 20060101
C08B037/08; A61P 17/02 20060101 A61P017/02; A61P 41/00 20060101
A61P041/00 |
Claims
1. A composition comprising a dicarboxy-derivatised chitosan
polymer cross-linked to an aldehyde-derivatized dextran
polymer.
2. The composition as claimed in claim 1 wherein the
dicarboxy-derivatised chitosan polymer is cross-linked to the
aldehyde-derivatised dextran polymer through the amine group of the
dicarboxy-derivatised chitosan polymer and the aldehyde group of
the aldehyde-derivatised dextran polymer.
3. The composition as claimed in claim 1 or claim 2 wherein the
polymer network forms a hydrogel within about 1 sec to about 5
minutes of mixing the dicarboxy-derivatised chitosan polymer and
the aldehyde-derivatised dextran polymer in aqueous solution.
4. The composition as claimed in claim 3 wherein the polymer
network forms a hydrogel within about 1 sec to about 30 sec of
mixing the dicarboxy-derivatised chitosan polymer and the
aldehyde-derivatised dextran polymer in aqueous solution.
5. The composition as claimed in claim 1 wherein the
dicarboxy-derivatised chitosan polymer is N-succinyl chitosan.
6. The composition of claim 1, further comprising an aqueous
solution.
7. The composition of claim 6 wherein the composition comprises
between about 2% to 10% w/v dicarboxy-derivatised chitosan polymer
and between about 2% to 10% w/v aldehyde-derivatised dextran
polymer.
8-10. (canceled)
11. The composition of claim 7 comprising between about 2% to about
8% w/v dicarboxy-derivatised chitosan polymer and about 2% to about
8% w/v aldehyde-derivatised dextran polymer.
12. The composition of claim 7 comprising about 5% w/v
dicarboxy-derivatised chitosan polymer and about 5% w/v
aldehyde-derivatised dextran polymer.
13. (canceled)
14. A method of producing composition of a dicarboxy-derivatised
chitosan polymer cross-linked to an aldehyde-derivatised dextran
polymer, comprising: mixing an aqueous solution of a
dicarbosy-derivatised chitosan polymer with an aqueous solution of
an aldehyde-derivatised aldehyde dextran polymer.
15. A The method of claim 14 wherein the aqueous solution of a
dicarboxy-derivatised chitosan polymer is between about 2% to about
10% w/v and the aqueous solution of dicarboxy-derivatised dextran
polymer is between about 2% to about 10% w/v.
16-17. (canceled)
18. The method of claim 14 wherein the pH of each aqueous solution
is between about 6 to about 8.
19. (canceled)
20. The method of claim 14 wherein the dicarboxy-derivatised
chitosan polymer is N-succinyl chitosan.
21. The composition of claim 1, further comprising one or more
biologically active agents.
22. The composition of claim 21 wherein said one or more
biologically active agents are selected from the group consisting
of plasma proteins, hormones, enzymes, antibiotics, antiseptic
agents, antineoplastic agents, antifungal agents, antiviral agents,
anti-inflammatory agents, growth factors, steroids, cell
suspensions, cytotoxins, and cell proliferation inhibitors.
23. A method of preventing or reducing adhesion of tissue
susceptible to adhesion formation comprising treating the tissue
with a composition of claim 1.
24. The method of claim 23 wherein the adhesion is a post-surgical
adhesion.
25. A method of accelerating or promoting wound healing comprising
treating the wound with a composition of claim 1.
26. A method of reducing or stopping bleeding of a wound comprising
treating the wound with a composition of claim 1.
27-28. (canceled)
29. A method of treating a tissue comprising applying to said
tissue: (a) an aqueous solution of a dicarboxy-derivatised chitosan
polymer; and (b) an aqueous solution of an aldehyde-derivatised
dextran polymer, such that (a) and (b) combine to form a
cross-linked composition on said tissue.
30. The method of claim 29, wherein said tissue has been
injured.
31. The method of claim 30, wherein said injury is selected from
the group consisting of wound, surgery or results in bleeding.
32. The method of claim 29, wherein said step of applying is
selected from the group consisting of spraying, squirting or
pouring.
33. The method of claim 29 wherein (a) and (b) are simultaneously
applied to said tissue.
34. (canceled)
35. The method of claim 29 wherein cross-linked composition forms
within about 1 sec to about 5 minutes of combining (a) and (b).
36. (canceled)
37. The method of claim 29 wherein the dicarboxy-derivatised
chitosan polymer is N-succinyl chitosan.
38. A wound dressing comprising the composition of claim 1.
39. A kit comprising: (a) dicarboxy-derivatised chitosan polymer,
and (b) an aldehyde-derivatized dextran polymer.
40. The kit as claimed in claim 39 wherein (a) and (b) are
freeze-dried.
41. The kit as claimed in claim 39 wherein either or both of (a)
and (b) are provided in separate aqueous solutions.
42. The kit of claim 41 wherein the aqueous solution of (a) is
between about 2% to about 10% w/v and the aqueous solution of (b)
is between about 2% to about 10% w/v.
43. A The kit of claim 42 wherein the aqueous solutions comprise
between about 0.1% to about 2% w/v NaCl.
44. The kit of claim 39 additionally comprising an aqueous solution
in which (a) and (b) can be dissolved to allow cross-linking to
occur.
45. The kit of claim 39 wherein (a) is N-succinyl chitosan.
Description
BACKGROUND OF THE INVENTION
[0001] The formation of adhesions is a frequent and unfortunate
result of many surgeries. Adhesions are fibrous bands connecting
tissue surfaces that are normally separated. Adhesions are
particularly common following abdominal and pelvic surgeries such
as hernia repair, gynaecological surgeries and colorectal
surgeries.
[0002] Trauma to the tissue caused by handling and drying during
surgery causes a fibrinous exudate to be released. If the exudate
is not absorbed or lysed, it may collect in the peritoneal or
pelvic cavity where it is converted into an adhesion. The exudate
becomes ingrown with fibroblasts, collogen is deposited and blood
vessels begin to form, allowing organisation of the adhesion.
[0003] The formation of adhesions can lead to serious complications
such as small bowel obstruction, female infertility and chronic
pain. Patients may need to undergo further surgery to dissect
adhesions, with no guarantees that new adhesions will not form.
[0004] Techniques to reduce adhesion formation include lavage of
the peritoneal cavity, administration of pharmacological agents and
mechanical separation of the tissues. Post-operative hemostasis,
the physiologic process whereby bleeding is halted, can also
decrease the risk of adhesion formation, as well as conferring
other benefits.
[0005] Unfortunately, current procedures for reducing adhesions
and/or achieving hemostasis are not particularly effective and can
be unpleasant for the patient. In addition, in some circumstances
treatments aimed at hemostasis may increase the risk of adhesion
formation.
[0006] For, example, following endoscopic sinus surgery (ESS) used
to treat chronic sinusitis, patients must endure uncomfortable
nasal packing to control bleeding. However, removal of the nasal
packs can cause mucosal trauma which increases the likelihood that
adhesions will form. Studies have shown that even dressings
incorporating known topical hemostatic agents such as thrombin,
fibrin, fibrinogen and collagen can cause a significant increase in
the formation of adhesions (see for example, Chandra R. K., Kern R.
C., Advantages and disadvantages of topical packing in endoscopic
sinus surgery, Curr Opin Otolaryngol Head Neck Sung 2004, 12,
21-26). Adhesion formation requiring further surgery occurs in
10-30% of patients undergoing ESS.
[0007] Polymer solutions and gels have been applied to target areas
to reduce adhesions. For example, gels have been used to coat
surgically exposed tissues before closing the surgical site. Some
approaches allow for the polymers to be added to the patient in
situ, in a solution and then chemically reacted to form covalent
cross-links so as to create a polymer network. For example,
SprayGel.TM. is a PEG-based material that forms an adhesion barrier
when applied to tissue.
[0008] Polysaccharide polymers such as chitosan are also well known
as gel forming medicinal agents. Chitosan is recognised to have
wound healing properties. For example, U.S. Pat. No. 5,836,970
discloses chitosan and alginate wound dressings that may be
prepared as fibers, powders, films, foams, or water-swellable
hydrocolloids. U.S. Pat. No. 5,599,916 discloses a water-swellable,
water-insoluble chitosan salt that can be used in wound dressings,
and U.S. Pat. No. 6,444,797 discloses a chitosan microflake that
can be used as a wound dressing or skin coating.
[0009] Chitosan has also been shown to have a preventative effect
on peritoneal adhesion in rats (Preventive effects of chitosan on
peritoneal adhesion in rats, Zhang, Zhi-Liang et al., World J
Gastroenterol, 2006, 12(28) 4572-4577.
[0010] Derivatives of chitosan have also been investigated for
their effects on wound-healing and adhesion prevention. For
example, PCT publication WO 96/35433 describes the use of
N,O-carboxymethylchitosan for the prevention of surgical adhesions.
N,O-carboxymethylchitosan has also been discussed in: [0011] (i)
Kennedy R et al., Prevention of experimental postoperative
adhesions by N,O-carboxymethyl chitosan, Surgery, 1996, 120,
866-70; [0012] (ii) Costain D J et al., Prevention of postsurgical
adhesions with N,O-carboxymethylchitosan: Examination of the most
efficacious preparation and the effect of N,O-carboxymethyl
chitosan on postsurgical healing, Surgery, 1997; 121, 314-9; [0013]
(iii) Krause T J et al., Prevention of pericardial adhesions with
N,O-carboxymethylchitosan in the Rat Model, Journal of
Investigative Surgery, 2001, 14; 93-97; [0014] (iv) Diamond,
Michael P. et al., Reduction of postoperative adhesions by
N,O-carboxymethylchitosan: a pilot study, Fertil Steril 2003, 80,
631-636; [0015] (v) Diamond Michael P et al., Reduction of post
operative adhesions by N,O-carboxymethylchitosan: A Pilot Study,
The Journal of the American Association of Gynecologic
Laparoscopists, 2004, 11(1), 127; and [0016] (vii) Lee, Timothy D.
G et al., Reduction in postoperative adhesion formation and
re-formation after an abdominal operation with the use of
N,O-carboxymethyl chitosan, Surgery, 2004, 135, 307-312.
[0017] PCT publication WO 98/22114 discusses the use of chitosan
combined with sulphated mono-, di-, or oligo-saccharides for
enhancing wound healing in collagen-containing tissues. PCT
publication WO 96/02260 describes chitosan in combination with
heparin, heparin sulphate or dextran sulphate. This combination is
said to promote healing of dermal wounds.
[0018] PCT publication WO 04/006961 describes a gel for
immobilizing and encapsulating cells formed by cross-linking
neutral chitosan with a bifunctional multifunctional aldehyde or
aldehyde-treated hydroxyl-containing polymer.
[0019] Despite these efforts, adhesion formation still commonly
occurs in many areas of surgery. Therefore, there is still a need a
great need for new polymeric materials with medical efficacy for
hemostasis and adhesion prevention that can be used to improve
surgical outcomes.
[0020] Accordingly, it is an object of the invention to provide a
hydrogel that can be applied to a wound to assist wound healing, or
to provide the public with a useful choice.
SUMMARY OF THE INVENTION
[0021] The invention relates to a hydrogel that can be applied to
surgical and other wounds. The hydrogel can be made by combining
aqueous solutions of two polymers which cross-link to foam a
polymer network when mixed. As cross-linking occurs, the resulting
polymer network forms a hydrogel in aqueous solution. The hydrogel
can be formed in situ, for example, by spraying, squirting or
pouring the polymer solutions onto the target area. Alternatively,
the hydrogel can be pre-formed, then applied to the target area. In
another embodiment, the hydrogel can be formed when a wound
dressing incorporating the polymer components is moistened.
[0022] Hydrogels of the invention assist in wound healing and may
help prevent adhesions forming between neighbouring tissues that
have been damaged so as to make them susceptible to adhesion
formation. Hydrogels of the invention may also affect haemostasis
by reducing or stopping bleeding of a wound. The hydrogels are
biodegradable under surgical conditions and will break down
gradually over a period of days or weeks.
[0023] In one aspect the invention provides a polymer network
comprising a dicarboxy-derivatised chitosan polymer cross-linked to
an aldehyde-derivatised dextran polymer.
[0024] In another aspect the invention provides a polymer network
consisting of a dicarboxy-derivatised chitosan polymer cross-linked
to an aldehyde-derivatised dextran polymer.
[0025] In one embodiment of the above aspects the
dicarboxy-derivatised chitosan polymer is cross-linked to the
aldehyde-derivatised dextran polymer through the amine group of the
dicarboxy-derivatised chitosan polymer and the aldehyde group of
the aldehyde-derivatised dextran polymer.
[0026] In one embodiment of the above aspects the
dicarboxy-derivatised chitosan polymer is an N-succinyl chitosan
polymer.
[0027] In another aspect the invention provides a polymer network
comprising N-succinyl chitosan cross-linked to an
aldehyde-derivatised dextran polymer.
[0028] In another aspect the invention provides a polymer network
consisting of N-succinyl chitosan cross-linked to an
aldehyde-derivatised dextran polymer.
[0029] In one embodiment of the above aspects the N-succinyl
chitosan is cross-linked to the aldehyde-derivatised dextran
polymer through the amine group of the N-succinyl chitosan and the
aldehyde group of the aldehyde-derivatised dextran polymer.
[0030] In another aspect the invention provides a polymer network
comprising a dicarboxy-derivatised chitosan polymer cross-linked to
an aldehyde-derivatised dextran polymer, wherein the polymer
network forms a hydrogel within about 1 sec to about 5 minutes of
mixing the dicarboxy-derivatised chitosan polymer and the
aldehyde-derivatised dextran polymer in aqueous solution.
[0031] In another aspect the invention provides a polymer network
comprising N-succinyl chitosan cross-linked to an
aldehyde-derivatised dextran polymer, wherein the polymer network
forms a hydrogel within about 1 sec to about 5 minutes of mixing
the N-succinyl chitosan and the aldehyde-derivatised dextran
polymer in aqueous solution.
[0032] In one embodiment the hydrogel forms within about 1 sec to
about 30 sec, preferably within about 1 sec to about 20 sec, more
preferably within about 1 sec to about 10 sec. In another
embodiment the hydrogel forms within about 30 sec to about 5
minutes. In another embodiment, the hydrogel forms within about 5
sec to about 1 min.
[0033] In another aspect the invention provides a polymer network
comprising a dicarboxy-derivatised chitosan polymer cross-linked to
an aldehyde-derivatised dextran polymer, wherein the polymer
network forms a hydrogel within about 5 minutes to about 20 minutes
of mixing the dicarboxy-derivatised chitosan polymer and the
aldehyde-derivatised dextran polymer in aqueous solution.
[0034] In another aspect the invention provides a polymer network
comprising N-succinyl chitosan cross-linked to an
aldehyde-derivatised dextran polymer, wherein the polymer network
forms a hydrogel within about 5 minutes to about 20 minutes of
mixing the N-succinyl chitosan and the aldehyde-derivatised dextran
polymer in aqueous solution.
[0035] In one embodiment the hydrogel forms within about 5 minutes
to about 10 minutes.
[0036] In another embodiment the hydrogel forms within about 10
minutes to about 20 minutes.
[0037] In another aspect the invention provides a polymer network
comprising a dicarboxy-derivatised chitosan polymer cross-linked to
an aldehyde-derivatised dextran polymer, wherein the polymer
network forms a hydrogel within about 20 minutes to about 2 hours
of mixing the dicarboxy-derivatised chitosan polymer and the
aldehyde-derivatised dextran polymer in aqueous solution.
[0038] In another aspect the invention provides a polymer network
comprising N-succinyl chitosan cross-linked to an
aldehyde-derivatised dextran polymer, wherein the polymer network
forms a hydrogel within about 20 minutes to about 2 hours of mixing
the N-succinyl chitosan and the aldehyde-derivatised dextran
polymer in aqueous solution.
[0039] In one embodiment the hydrogel forms within about 20 minutes
to about 2 hours, preferably within about 30 minutes to about 1
hour.
[0040] In one aspect the invention provides a wound healing
composition comprising a dicarboxy-derivatised chitosan polymer and
an aldehyde-derivatised dextran polymer in aqueous solution.
[0041] In one embodiment the dicarboxy-derivative is N-succinyl
chitosan.
[0042] In one embodiment the composition comprises between about 2%
to 10% w/v dicarboxy-derivatised chitosan polymer. In one
embodiment, the composition comprises between about 2% to 10% w/v
aldehyde-derivatised dextran polymer.
[0043] In another aspect the invention provides a hydrogel
comprising a dicarboxy-derivatised chitosan polymer cross-linked to
an aldehyde-derivatised dextran polymer in aqueous solution.
[0044] In one embodiment the hydrogel comprises between about 2% to
about 10% w/v dicarboxy-derivatised chitosan polymer. In one
embodiment the hydrogel comprises between about 2% to about 10% w/v
aldehyde-derivatised dextran polymer.
[0045] Preferably, the hydrogel comprises between about 2% to about
8% w/v, more preferably between about 2% to about 6% w/v
dicarboxy-derivatised chitosan polymer. Most preferably, the
hydrogel comprises about 5% w/v dicarboxy-derivatised chitosan
polymer.
[0046] Preferably, the hydrogel comprises between about 2% to about
8% w/v, more preferably between about 2% to about 6% w/v
aldehyde-derivatised dextran polymer. Most preferably, the hydrogel
comprises about 5% w/v aldehyde-derivatised dextran polymer.
[0047] In one embodiment the dicarboxy-derivatised chitosan polymer
is N-succinyl chitosan.
[0048] In one embodiment, the aqueous solution is selected from the
group comprising water, saline, buffer and mixtures thereof.
Preferably, the aqueous solution is about 0.9% w/v saline
solution.
[0049] In another aspect the invention provides a method of
producing a polymer network comprising a dicarboxy-derivatised
chitosan polymer cross-linked to an aldehyde-derivatised dextran
polymer, wherein the method comprises mixing an aqueous solution of
a dicarboxy-derivatised chitosan polymer with an aqueous solution
of an aldehyde-derivatised dextran polymer.
[0050] In one embodiment the aqueous solution of
dicarboxy-derivatised chitosan polymer comprises between about 2%
to about 10% w/v of a dicarboxy-derivatised chitosan polymer.
Preferably, the aqueous solution comprises between about 2% to
about 8% w/v, more preferably about 5% w/v of a
dicarboxy-derivatised chitosan polymer.
[0051] In one embodiment the aqueous solution of
dicarboxy-derivatised chitosan polymer has a pH of between about 6
to 8. Preferably, the aqueous solution of dicarboxy-derivatised
chitosan polymer has a pH between about 6.5 to 7.5.
[0052] In one embodiment the dicarboxy-derivatised chitosan is
N-succinyl chitosan.
[0053] In one embodiment the aqueous solution of
aldehyde-derivatised dextran polymer comprises between about 2% to
about 10% w/v of an aldehyde-derivatised dextran polymer.
Preferably, the aqueous solution comprises between about 2% to
about 8% w/v, more preferably, about 5% w/v of an
aldehyde-derivatised dextran polymer.
[0054] In one embodiment the aqueous solution of
aldehyde-derivatised dextran polymer has a pH of between about 6 to
8. Preferably, the aqueous solution of aldehyde-derivatised dextran
polymer has a pH of between about 6.5 to 7.5.
[0055] In one embodiment the aldehyde-derivatised dextran polymer
is 50-100% aldehyde-derivatised, preferably 70-100%
aldehyde-derivatised, more preferably 80-100%
aldehyde-derivatised.
[0056] In one embodiment the method comprises mixing equal volumes
of aqueous solutions of (a) a dicarboxy-derivatised chitosan
polymer, and (b) an aldehyde-derivatised dextran polymer.
[0057] In one embodiment the polymer network and aqueous solution
together comprise a hydrogel.
[0058] In one embodiment the aqueous solutions of polymers are
mixed by stirring the solutions together. In another embodiment,
the aqueous solutions of polymers are mixed as they are applied to
a target area, such as by simultaneously spraying, squirting or
pouring the solutions onto the target area.
[0059] In one embodiment, the aqueous solution is selected from the
group comprising water, saline, buffer and mixtures thereof.
Preferably, the aqueous solution is about 0.9% w/v saline
solution.
[0060] In one embodiment, the aqueous solutions of polymers may
contain one or more pharmaceutically acceptable excipients.
[0061] In one aspect the invention provides a hydrogel comprising a
dicarboxy-derivatised chitosan polymer cross-linked to an
aldehyde-derivatised dextran polymer wherein the hydrogel comprises
one or more biologically active agents.
[0062] In one embodiment the one or more biologically active agents
are selected from the group comprising plasma proteins, hormones,
enzymes, antibiotics, antiseptic agents, antineoplastic agents,
antifungal agents, antiviral agents, antiinflammatory agents, local
anesthetics, growth factors, steroids, cell suspensions,
cytotoxins, and cell proliferation inhibitors.
[0063] In one aspect the invention provides a hydrogel comprising a
dicarboxy-derivatised chitosan polymer cross-linked to an
aldehyde-derivatised dextran polymer wherein the hydrogel comprises
one or more non-biologically active agents.
[0064] In one embodiment the one or more non-biologically active
agents are selected from the group comprising thickeners and
dyes.
[0065] In one aspect the invention provides a method of preventing
or reducing adhesion of tissue susceptible to adhesion formation,
comprising treating the tissue with a hydrogel of the
invention.
[0066] In one embodiment the adhesion is post-surgical
adhesion.
[0067] In one embodiment the method comprises applying to the
tissue a hydrogel of the invention. Preferably, a layer of the
hydrogel is spread over the surface of the tissue.
[0068] In one embodiment the method comprises applying to the
tissue (a) an aqueous solution of a dicarboxy-derivatised chitosan
polymer and (b) an aqueous solution of an aldehyde-derivatised
dextran polymer such that (a) and (b) combine to form the hydrogel
on the surface of the tissue.
[0069] In one embodiment (a) and (b) are simultaneously applied to
the tissue.
[0070] In one embodiment (a) and (b) are simultaneously sprayed
onto the tissue. In one embodiment (a) and (b) are simultaneously
squirted onto the tissue. In another embodiment (a) and (b) are
simultaneously poured onto the tissue.
[0071] In another aspect the invention provides a method of
preventing or reducing post-surgical adhesion of tissue susceptible
to adhesion formation comprising treating the tissue with a
hydrogel of the invention, wherein the method comprises applying to
the tissue (a) an aqueous solution of an dicarboxy-derivatised
chitosan polymer and (b) an aqueous solution of an
aldehyde-derivatised dextran polymer such that (a) and (b) combine
to form the hydrogel on the surface of the tissue.
[0072] In another aspect the invention provides a method of
accelerating or promoting wound healing comprising treating the
wound with a hydrogel of the invention.
[0073] In one embodiment the method comprises applying to the wound
a hydrogel of the invention. Preferably, a layer of the hydrogel is
spread over the surface of the wound.
[0074] In one embodiment the method comprises applying to the wound
(a) an aqueous solution of an dicarboxy-derivatised chitosan
polymer and (b) an aqueous solution of an aldehyde-derivatised
dextran polymer such that (a) and (b) combine to form the
hydrogel.
[0075] In one embodiment (a) and (b) are simultaneously applied to
the wound.
[0076] In one embodiment (a) and (b) are simultaneously sprayed
onto the wound. In one embodiment (a) and (b) are simultaneously
squirted onto the wound. In another embodiment (a) and (b) are
simultaneously poured onto the wound.
[0077] In another aspect the invention provides a method of
accelerating or promoting wound healing comprising treating the
wound with a hydrogel of the invention, wherein the method
comprises applying to the wound (a) an aqueous solution of an
dicarboxy-derivatised chitosan polymer and (b) an aqueous solution
of an aldehyde-derivatised dextran polymer such that (a) and (b)
combine to form the hydrogel on the surface of the wound.
[0078] In another aspect the invention provides a method of
reducing or stopping bleeding of a wound comprising treating the
wound with a hydrogel of the invention.
[0079] In one embodiment the method comprises applying to the wound
a hydrogel of the invention. Preferably, a layer of the hydrogel is
spread over the surface of the wound.
[0080] In one embodiment the method comprises applying to the wound
(a) an aqueous solution of an dicarboxy-derivatised chitosan
polymer and (b) an aqueous solution of an aldehyde-derivatised
dextran polymer such that (a) and (b) combine to form the
hydrogel.
[0081] In one embodiment (a) and (b) are simultaneously applied to
the wound.
[0082] In one embodiment (a) and (b) are simultaneously sprayed
onto the wound. In one embodiment (a) and (b) are simultaneously
squirted onto the wound. In another embodiment (a) and (b) are
simultaneously poured onto the wound.
[0083] In another aspect the invention provides a method of
reducing or stopping bleeding of a wound comprising treating the
wound with a hydrogel of the invention, wherein the method
comprises applying to the wound (a) an aqueous solution of an
dicarboxy-derivatised chitosan polymer and (b) an aqueous solution
of an aldehyde-derivatised dextran polymer such that (a) and (b)
combine to form the hydrogel on the surface of the wound.
[0084] In another aspect the invention provides a method of
delivering one or more biologically active agents to a tissue
comprising treating the tissue with a hydrogel of the invention,
wherein the hydrogel comprises one or more biologically active
agents.
[0085] In one embodiment the method comprises applying to the
tissue a hydrogel of the invention, wherein the hydrogel comprises
one or more biologically active agents. Preferably, a layer of the
hydrogel is spread over the surface of the tissue.
[0086] In one embodiment the method comprises applying to the
tissue (a) an aqueous solution of a dicarboxy-derivtised chitosan
polymer and (b) an aqueous solution of an aldehyde-derivatised
dextran polymer such that (a) and (b) combine to form the hydrogel
on the surface of the tissue, wherein one or both of (a) and (b)
include one or more biologically active agents.
[0087] In one aspect the invention provides a use of a hydrogel of
the invention in the manufacture of a medicament for preventing or
reducing post-surgical adhesion of tissue susceptible to adhesion
formation.
[0088] In another aspect the invention provides a use of (a) an
aqueous solution of a dicarboxy-derivatised chitosan polymer and
(b) an aqueous solution of an aldehyde-derivatised dextran polymer
in the manufacture of a medicament for preventing or reducing
adhesion of tissue susceptible to adhesion formation, wherein (a)
and (b) combine to form a hydrogel of the invention.
[0089] In another aspect the invention provides a use of a hydrogel
of the invention in the manufacture of a medicament for
accelerating or promoting wound healing.
[0090] In another aspect the invention provides a use of (a) an
aqueous solution of a dicarboxy-derivatised chitosan polymer and
(b) an aqueous solution of an aldehyde-derivatised dextran polymer
in the manufacture of a medicament for accelerating or promoting
wound healing, wherein (a) and (b) combine to form a hydrogel of
the invention.
[0091] In another aspect the invention provides a use of a hydrogel
of the invention in the manufacture of a medicament for reducing or
stopping bleeding of a wound.
[0092] In another aspect the invention provides a use of (a) an
aqueous solution of a dicarboxy-derivatised chitosan polymer and
(b) an aqueous solution of an aldehyde-derivatised dextran polymer
in the manufacture of a medicament for reducing or stopping
bleeding of a wound, wherein (a) and (b) combine to form a hydrogel
of the invention.
[0093] In another aspect the invention provides a use of a hydrogel
of the invention in the manufacture of a medicament for delivering
one or more biologically active agents to a tissue, wherein the
medicament comprises one or more biologically active agents.
[0094] In another aspect the invention provides the use of (a) an
aqueous solution of an dicarboxy-derivatised chitosan polymer and
(b) an aqueous solution of an aldehyde-derivatised dextran polymer
in the manufacture of a medicament for delivering one or more
biologically active agents to a tissue, wherein (a) and (b) combine
to form a hydrogel of the invention and wherein one or both of (a)
and (b) include one or more biologically active agents.
[0095] In the methods and uses of the invention described
above:
[0096] In one embodiment the hydrogel forms within about 1 sec to
about 5 minutes of combining (a) and (b) to produce the
medicament.
[0097] In one embodiment the hydrogel forms within about 1 sec to
about 30 sec, preferably within about 1 sec to about 20 sec, more
preferably within about 1 sec to about 10 sec. In another
embodiment the hydrogel forms within about 30 sec to about 5
minutes. In another embodiment, the hydrogel forms within about 5
sec to about 1 min.
[0098] In one embodiment the hydrogel forms within about 5 minutes
to about 20 minutes of combining (a) and (b) to produce the
medicament.
[0099] In one embodiment the hydrogel forms within about 5 minutes
to about 10 minutes. In another embodiment the hydrogel forms
within about 10 minutes to about 20 minutes.
[0100] In one embodiment the hydrogel forms within about 20 minutes
to about 2 hours of combining (a) and (b) to produce the
medicament.
[0101] In one embodiment the hydrogel forms within about 30 minutes
to about 2 hours, preferably within about 30 minutes to about 1
hour.
[0102] In one embodiment (a) comprises between about 2% to about
10% w/v dicarboxy-derivatised chitosan polymer, preferably between
about 2% to about 8% w/v, more preferably about 5% w/v. In one
embodiment (b) comprises between about 2% to about 10% w/v
aldehyde-derivatised dextran polymer, preferably between about 2%
to about 8% w/v, more preferably about 5% w/v.
[0103] In one embodiment (a) has a pH of between about 6 to 8,
preferably between about 6.5 to 7.5.
[0104] In one embodiment (b) has a pH of between about 6 to 8,
preferably between about 6.5 to 7.5.
[0105] In one embodiment the dicarboxy-derivatised chitosan is
N-succinyl chitosan.
[0106] In another aspect the invention provides a wound dressing
capable of releasing a hydrogel of the invention when
moistened.
[0107] In one embodiment the wound dressing comprises a
dicarboxy-derivatised chitosan polymer and an aldehyde-derivatised
dextran polymer. In one embodiment the dicarboxy-derivatised
chitosan polymer is N-succinyl chitosan.
[0108] In one embodiment the wound dressing is selected from the
group comprising a bandage, strip, pad, gauze, film, stocking and
tape.
[0109] In another aspect the invention provides a kit for use in
the methods of the invention wherein the kit comprises: [0110] (a)
a dicarboxyl-derivatised chitosan polymer, and [0111] (b) an
aldehyde-derivatised dextran polymer.
[0112] In one embodiment the kit also comprises an aqueous solution
in which (a) and (b) can be dissolved to allow cross-linking to
occur. In another embodiment, the kit also comprises an aqueous
solution of either or both of (a) and (b).
[0113] In another aspect the invention provides a kit for use in
the methods of the invention wherein the kit comprises in separate
containers: [0114] (a) a dicarboxyl-derivatised chitosan polymer,
and [0115] (b) an aldehyde-derivatised dextran polymer.
[0116] In one embodiment the kit also comprises an aqueous solution
in which (a) and (b) can be dissolved to allow cross-linking to
occur. In another embodiment, the kit also comprises an aqueous
solution of either or both of (a) and (b).
[0117] In the kits of the invention described above:
[0118] In one embodiment the kit of the invention also comprises
instructions for use in a method of preventing or reducing
post-surgical adhesion of tissue that is susceptible to adhesion
formation.
[0119] In one embodiment the kit of the invention also comprises
instructions for use in a method of accelerating or promoting wound
healing.
[0120] In one embodiment the kit of the invention also comprises
instructions for use in a method of reducing or stopping bleeding
of a wound.
[0121] In one embodiment, the dicarboxyl-derivatised chitosan
polymer and the aldehyde-derivatised dextran polymer provided in
the kit of the invention are freeze-dried. In one embodiment the
kit also comprises an aqueous solution in which to dissolve the
dicarboxyl-derivatised chitosan polymer and the
aldehyde-derivatised dextran polymer.
[0122] In one embodiment, at least one of, preferably both of the
dicarboxyl-derivatised chitosan polymer and the
aldehyde-derivatised dextran polymer are separately provided in an
aqueous solution. In one embodiment the aqueous solutions are
frozen.
[0123] In one embodiment the aqueous solution of
dicarboxy-derivatised chitosan polymer comprises between about 2%
to about 10% w/v of a dicarboxy-derivatised chitosan polymer.
Preferably, the aqueous solution comprises between about 2% to
about 8% w/v, more preferably about 5% w/v of a
dicarboxy-derivatised chitosan polymer.
[0124] In one embodiment the aqueous solution of
dicarboxy-derivatised chitosan polymer has a pH of between about 6
to 8. Preferably, the aqueous solution of dicarboxy-derivatised
polymer has a pH between about 6.5 to 7.5.
[0125] In one embodiment the dicarboxy-derivatised chitosan is
N-succinyl chitosan.
[0126] In one embodiment the aqueous solution of
aldehyde-derivatised dextran polymer comprises between about 2% to
about 10% w/v of an aldehyde-derivatised dextran polymer.
Preferably, the aqueous solution comprises between about 2% to
about 8% w/v, more preferably, about 5% w/v of an
aldehyde-derivatised dextran polymer.
[0127] In one embodiment the aqueous solution of
aldehyde-derivatised dextran polymer has a pH of between about 6 to
8. Preferably, the aqueous solution of aldehyde-derivatised dextran
has a pH of between about 6.5 to 7.5.
[0128] Optionally, either or both of the aqueous solutions may
contain one or more pharmaceutically acceptable excipients.
[0129] In one embodiment, the aqueous solution is selected from the
group comprising water, saline, buffer and mixtures thereof.
Preferably, the aqueous solution is about 0.9% w/v saline
solution.
[0130] In one embodiment either or both of the aqueous solutions
may contain one or more biologically active agents and/or one or
more non-biologically active agents.
[0131] In one embodiment one or more of (a) and (b) also
incorporates one or more biological active agents.
[0132] It is intended that reference to a range of numbers
disclosed herein (for example, 1 to 10) also incorporates reference
to all rational numbers within that range (for example, 1, 1.1, 2,
3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of
rational numbers within that range (for example, 2 to 8, 1.5 to 5.5
and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges
expressly disclosed herein are hereby expressly disclosed. These
are only examples of what is specifically intended and all possible
combinations of numerical values between the lowest value and the
highest value enumerated are to be considered to be expressly
stated in this application in a similar manner.
[0133] In this specification where reference has been made to
patent specifications, other external documents, or other sources
of information, this is generally for the purpose of providing a
context for discussing the features of the invention. Unless
specifically stated otherwise, reference to such external documents
is not to be construed as an admission that such documents, or such
sources of information, in any jurisdiction, are prior art, or form
part of the common general knowledge in the art.
[0134] The invention may also be said broadly to consist in the
parts, elements and features referred to or indicated in the
specification of the application, individually or collectively, in
any or all combinations of two or more of said parts, elements or
features, and where specific integers are mentioned herein which
have known equivalents in the art to which the invention relates,
such known equivalents are deemed to be incorporated herein as if
individually set forth.
BRIEF DESCRIPTION OF THE DRAWINGS
[0135] FIG. 1 is a graph showing the percentage of sheep in each
group of the trial described in Example 6 with adhesions on the
lateral nasal wall following treatment.
[0136] FIG. 2 is a graph showing the mean grade of adhesions on the
lateral nasal wall (Example 6).
[0137] FIG. 3 is a graph showing the percentage of sheep in each
group with ethmoidal adhesions (Example 6).
[0138] FIG. 4 is a graph showing the mean ethmoidal adhesion grade
for all treatments compared to matched controls (Example 6).
[0139] FIG. 5 is a graph showing a light microscopy comparison of
epithelial height over time (Example 6).
[0140] FIG. 6 is a graph showing a light microscopy comparison of
the percentage re-epithelialisation (Example 6).
[0141] FIG. 7 is a graph showing a scanning electron microscopy
comparison of the percentage surface area that was re-ciliated
(Example 6).
[0142] FIG. 8 is a graph showing a scanning electron microscopy
comparison of cilial grade (Example 6).
[0143] FIG. 9 is a graph showing the mean cilliary beat frequency
(CBF) for each of the groups (Example 6).
[0144] FIG. 10 is a graph showing the active vs placebo surgical
field grade score using the Boezaart grading scale (Example 7).
[0145] FIG. 11 is a graph showing the active vs placebo surgical
field grading score using the Wormald grading scale (Example
7).
[0146] FIG. 12 is a graph showing the active vs control surgical
field grading score using the Wormald grading scale (Example
8).
[0147] FIG. 13 is a graph showing the time to complete hemostasis
for the active vs control (Example 8)
[0148] FIG. 14 is a graph comparing crust scores over time for
active vs control (Example 8)
DETAILED DESCRIPTION OF THE INVENTION
1. Definitions
[0149] As used herein the term "chitosan" means a linear
polysaccharide composed of randomly distributed .beta.-(1,4) linked
D-glucosamine and N-acetyl-D-glucosamine. Chitosan can be produced
by deacetylation of chitin. Both .alpha.- and .beta.-chitosan are
suitable for use in the invention. The degree of deacetylation (%
DA) influences the solubility and other properties of the chitosan.
Commercially available chitosan typically has a degree of
deacetylation of between about 50 to 100%. A monomer unit of fully
deacetylated chitosan is shown in formula I below.
##STR00001##
[0150] As used herein the term "dicarboxy-derivatised chitosan
polymer" means a chitosan polymer that has been derivatised by
reaction of a cyclic anhydride with the amine group of some of the
D-glucosamine residues of the chitosan polymer. Examples of
dicarboxy groups include N-succinyl, N-maloyl and N-phthaloyl.
N-succinyl is preferred.
[0151] The "dicarboxy-derivatised chitosan polymer" may also be
partially derivatised with other functional groups. This secondary
derivatisation can occur either at amine positions that are not
derivatised with a dicarboxy group or at the hydroxy groups of the
D-glucosamine residues. For example, reaction of the cyclic
anhydride with an OH group of the chitosan may lead to some
monomers containing ester groups rather than, or in addition to the
amide substituent.
[0152] If secondary derivatisation is present at the amine position
of the dicarboxy-derivatised chitosan polymer, the polymer must
retain sufficient free amine groups to be able to form cross-links
with the aldehyde-derivatised dextran polymer. Preferably, the
dicarboxy-derivatised chitosan polymer is only derivatised by
reaction of the cyclic anhydride with the amine group of some of
the D-glucosamine residues.
[0153] As used herein the term "N-succinyl chitosan polymer" means
chitosan that has been derivatised by addition of an N-succinyl
group on the amine group of some of the D-glucosamine residues of
the chitosan polymer. A monomer unit of an N-succinyl chitosan
polymer is shown in formula II below.
##STR00002##
[0154] The degree of succinylation may vary. Typically, it is
between about 30 to 70%, but the N-succinyl chitosan polymer must
retain sufficient free amine groups to be able to form cross-links
with the aldehyde-derivatised dextran. The N-succinyl chitosan
polymer may also include secondary derivatisation as discussed for
the "dicarboxy-derivatised chitosan polymer" (above).
[0155] The term "N-succinyl chitosan" as used herein, means an
N-succinyl chitosan polymer that is only derivatised with
N-succinyl groups at the amine positions and does not include
secondary derivatisation with other functional groups.
[0156] As used herein the term "dextran" means a glucose
polysaccharide composed of .alpha.-(1,6) glycosidic linkages with
short .alpha.-(1,3) side chains. A monomer unit of dextran is shown
in formula III below.
##STR00003##
[0157] Dextran can be obtained by fermentation of
sucrose-containing media by Leuconostoc mesenteroides B512F.
Dextrans of molecular weights from 1 KDa to 2000 KDa are
commerically available.
[0158] As used herein the term "aldehyde-derivatised dextran
polymer" means a dextran polymer in which some vicinal secondary
alcohol groups have been oxidised to give a reactive bisaldehyde
functionality. Aldehyde-derivatised dextran polymers may also be
derivatised at other positions with other functional groups.
Preferably, the aldehyde-derivatised dextran polymer is only
derivatised at vicinal secondary alcohol groups. A representative
monomer unit of aldehyde-derivatised dextran polymer is shown in
formula IV below.
##STR00004##
[0159] As used herein the term "controlled release" in the context
of controlled release of a biologically active agent means longer
than expected delivery of a biologically active agent compared to
what would be expected based on diffusion only.
[0160] As used herein the term "hydrogel" means a two- or
multicomponent system consisting of a three-dimensional network of
polymer chains and water that fills the spaces between the
macromolecules.
[0161] As used herein the term "tissue" means an aggregate of
morphologically similar cells with associated intercellular matter
that acts together to perform one or more specific functions in the
body of an organism including a human. Examples of tissues include
but are not limited to muscle, epidermal, nerve and connective
tissue.
[0162] The term "tissue" also encompasses organs comprising one or
more tissue types including but not limited to the chest tissues
such as the aorta, the heart, the pleural cavity, the trachea, the
lungs, the pericardium and pericardial cavity; the abdominal and
retroperitoneal tissues such as the stomach, the small and large
intestines, the liver, the pancreas, the gall bladder, the kidneys
and the adrenal glands; pelvic cavity tissues including the tissues
of the male and female reproductive and urinary tracts; central and
peripheral nervous system tissues such as the spinal column and
nerves, dura and peripheral nerves; musculoskeletal system tissues
such as skeletal muscle, tendons, bones and cartilage; head and
neck tissues such as the eye, ear, neck, larynx, nose and paranasal
sinuses.
[0163] As used herein the term "adhesion" means an abnormal
attachment between tissues or organs or between tissues and
implants that form after an inflammatory stimulus, such as
surgery.
[0164] Tissues that are susceptible to adhesion formation are
tissues that have been exposed to an inflammatory stimulus. For
example, tissues which have been involved in surgical procedures
such as but not limited to endoscopic sinus surgery, abdominal
surgery, gynaecological surgery, musculoskeletal surgery,
ophthalmic surgery, orthopaedic surgery and cardiovascular surgery.
Tissues may also be susceptible to adhesion formation following
other events such as mechanical injury, disease, for example,
pelvic inflammatory disease, radiation treatment and the presence
of foreign material, for example, a surgical implant.
[0165] As used herein the term "wound" means any damage to a tissue
in a living organism including human organisms. The tissue may be
an internal tissue such as an internal organ or an external tissue
such as the skin. The damage may have resulted from a surgical
incision or the unintended application of force to the tissue.
Wounds include damage caused by mechanical injuries such as
abrasions, lacerations, penetrations and the like, as well as burns
and chemical injuries. The damage may also have arisen gradually
such as occurs in an ulcer, lesion, sore, or infection. Examples of
wounds include, but are not limited to, contused wounds, incised
wounds, penetrating wounds, perforating wounds, puncture wounds and
subcutaneous wounds.
[0166] As used herein the term "comprising" as used in this
specification means "consisting at least in part of". When
interpreting each statement in this specification that includes the
term "comprising", features other than that or those prefaced by
the term may also be present. Related terms such as "comprise" and
"comprises" are to be interpreted in the same manner.
2. The Polymer Network
[0167] The invention relates to a novel polymer network formed by
derivatisation and cross-linking of two well-known polymers;
chitosan and dextran. The polymer rapidly forms a three-dimensional
polymer network, creating a hydrogel in aqueous solution. The
properties of the hydrogel can be tailored for specific
applications by modifying the derivatisation and cross-linking of
the two polymer components.
[0168] In its broadest aspect the invention provides a polymer
network comprising a dicarboxy-derivatised chitosan cross-linked to
an aldehyde-derivatised dextran.
[0169] 2.1 The Chitosan Component
[0170] Chitosan is widely available and can be obtained
commercially from a range of sources, for example, Sigma-Aldrich
(www.sigma-aldrich.com).
[0171] Alternatively, chitosan can be prepared by deacetylation of
chitin. Many deacetylation methods are known in the art, for
example, hydrolysing chitin in a concentrated solution of sodium
hydroxide on heating and then recovering chitosan by filtering and
washing with water. Chitin exists as either .alpha.-chitin or
.beta.-chitin, depending on whether the linkage between the
glucosamine units is .alpha. or .beta.. Chitin is found in
crustaceans, insets, fungi, algae and yeasts. .alpha.-chitin is
obtained predominantly from the shells of crustaceans such as
lobster, crab and shrimp, whereas .beta.-chitin is derived from
squid pens. Both types of chitin can be used to prepare the
dicarboxy-derivatised chitosan for use in the invention.
[0172] Generally, the average molecular weight (MW.sub.av) of
commercially available chitosan is between about 1 to 1000 kDa. Low
molecular weight chitosan has a MW.sub.av of about 1 to 50 kDa.
High molecular weight chitosan has a MW.sub.av of about 250 to 800
kDa. Chitosan of any MW.sub.av can be used in the invention.
[0173] Deacetylation of chitin means that the resulting chitosan
has a majority of free, primary amine groups along its polymeric
backbone. The degree of deacylation of the chitosan may influence
the properties of the polymer network of the invention because only
those glucosamine units that are deacetylated are available for
derivatisation or cross-linking. In addition, the solubility of the
chitosan depends on the degree of deacylation.
[0174] Chitosan polymers most suitable for use in the invention
have a degree of deacetylation of between about 40% to 100%.
Preferably, the degree of deacylation is between about 60% to 95%,
more preferably, between about 70% to 95%.
[0175] Chitosans for use in the invention are dicarboxy-derivatised
at the amine made free by deacetylation of the chitin.
Dicarboxy-derivatised chitosan polymers can be made by reacting
chitosan with a cyclic acid anhydride. Cyclic acid anhydrides
suitable for use in the invention include succinic anhydride,
maleic anhydride, phthalic anhydride, glutaric anhydride,
citraconic anhydride, methylglutaconic anhydride, methylsuccinic
anhydride and the like.
[0176] Preferably, the dicarboxy-derivatised chitosan polymer is
made from the reaction of chitosan and one or more of succinyl
anhydride, phthalic anhydride, or glutaric anhydride. More
preferably, the dicarboxy-derivatised chitosan polymer is made from
the reaction of chitosan and succinyl anhydride.
[0177] Derivatisation can be achieved by any method known in the
art. For example, the solid chitosan can be heated in a solution of
cyclic anhydride in DMF or solubilised in a methanol/water mixture
and then reacted with the anhydride. Other solvents suitable for
use in the derivatisation process include dimethylacetamide. Acids
such as lactic acid, HCl or acetic acid can be added to improve the
solubility of the chitosan. A base such as NaOH is typically added
to deacetylate some of the acetylated amine groups.
[0178] Typical methods are provided in Example 1. The method used
can be selected depending on the cyclic anhydride used and/or the
average molecular weight of the chitosan. Both the chitosan and the
cyclic anhydride should be able to substantially dissolve or swell
in the solvent used.
[0179] In a preferred embodiment, the dicarboxy-derivatised
chitosan is N-succinyl chitosan. Methods of preparing N-succinyl
chitosan are well known in the art. See for example, "Preparation
of N-succinyl chitosan and their physical-chemical properties", J
Pharm Pharmacol. 2006, 58, 1177-1181.
[0180] The reaction of the cyclic anhydride with the chitosan
acylates some of the free amine positions with dicarboxy groups.
For example, when the cyclic anhydride used is succinic anhydride,
some of the amine groups are N-succinylated. The NaOH treatment
following N-succinylation removes some of the acyl groups from the
amine groups in the chitosan. Increasing the temperature of the
NaOH treatment increases the percentage of free amine groups
present, as demonstrated in Example 4.
[0181] The degree of acylation is indicated by the ratio of C:N in
the product. The degree of acylation can also be determined by 'H
nmr. An N-succinyl chitosan polymer is represented below. Formula V
shows the three types of D-glucosamine units present in the
polymer--the N-succinylated-D-glucosamine, the free D-glucosamine,
and the N-acetyl-D-glucosamine.
##STR00005##
[0182] In one embodiment, x is between about 60 to 80%, y is
between about 1 to 15% and z is between about 10 to 25%.
[0183] In another embodiment, x is between about 60 to 80%, y is
between about 1 to 30% and z and between about 2 to 25%.
[0184] High degrees of anhydride substitution render the
dicarboxy-derivatised chitosan polymer more soluble but may hinder
cross-linking to the aldehyde-derivatised dextran polymer.
[0185] In one embodiment, the dicarboxy-derivatised chitosan
polymer is between about 20% and 80% dicarboxy derivatised.
Preferably, the dicarboxy-derivatised chitosan polymer is between
about 30% and 60% dicarboxy derivatised. More preferably,
dicarboxy-derivatised chitosan polymer is between about 45% and 50%
dicarboxy derivatised.
[0186] In one embodiment, the dicarboxy-derivatised chitosan
polymer is between about 50% and 90% dicarboxy derivatised.
Preferably, the dicarboxy-derivatised chitosan polymer is between
about 60% and 80% dicarboxy derivatised.
[0187] 2.2 The Dextran Component
[0188] Dextran is a polysaccharide made of D-glucose units linked
predominantly by .alpha.-1,6 linkages. Crude, high molecular weight
dextran is commercially obtained by growing Leuconostoc
mesenteroies on sucrose. The resulting polysaccharide is hydrolysed
to yield low molecular weight dextrans.
[0189] Before dextran can be cross-linked to the
dicarboxy-derivatised chitosan polymer, it must be activated.
Reactive bisaldehyde functionalities can be generated from the
vicinal secondary alcohol groups on dextran by oxidation. Typical
methods are provided in Example 2. The resulting
aldehyde-derivatised dextran polymer can then be reductively
coupled to the primary amine groups of the dicarboxy-derivatised
chitosan to form a cross-linked polymer network of the
invention.
[0190] In one embodiment, the oxidising agent is sodium periodate.
Other suitable oxidising agents include potassium periodate and the
like.
[0191] The oxidised product, the aldehyde-derivatised dextran
polymer, actually only contains a small amount of free aldehyde
groups. Most of the aldehyde groups are masked as acetals and
hemiacetals, which are in equilibrium with the free aldehyde form
of the dextran. Reaction of some of the free aldehyde groups causes
the equilibrium to shift from the acetal and hemiacetal form,
towards the formation of more free aldehyde groups.
[0192] The degree of oxidation can be influenced by the molar ratio
of oxidising agent used. A higher degree of oxidation will provide
an aldehyde-derivatised dextran polymer with more sites available
for cross-linking. However, a lower degree of oxidation will result
in a more soluble aldehyde-derivatised dextran polymer. The
periodate reaction also dramatically decreases the molecular weight
of the dextran polymer.
[0193] In one embodiment, the degree of oxidation is between about
30% to about 100%, more preferably between about 50% to about 100%.
Most preferably, the degree of oxidation is between about 80 to
about 100%.
[0194] Example 5 compares gelling times for polymer networks of the
invention prepared using aldehyde-derivatised dextran polymers with
different degrees of aldehyde-derivatisation (or oxidation). More
highly aldehyde-derivatised dextran polymers have lower molecular
weights and form gels faster, when combined in solution with
solutions of N-succinyl chitosan.
[0195] The degree of derivatisation can be measured using the
extended reaction with hydroxylamine hydrochloride and then
titration of the liberated protons (Zhao, Huiru, Heindel, Ned D,
"Determination of degree of substitution of formyl groups in
polyaldehyde dextran by the hydroxylamine hydrochloride method,"
Pharmaceutical Research (1991), 8, page 400-401).
[0196] 2.3 Cross-Linking the Chitosan Component with the Dextran
Component
[0197] The invention provides a polymer network comprising a
dicarboxy-derivatised chitosan polymer cross-linked to an
aldehyde-derivatised dextran polymer. In one embodiment the
dicarboxy-derivated chitosan polymer is an N-succinyl chitosan
polymer. In one embodiment the N-succinyl chitosan polymer is
cross-linked to the aldehyde-derivatised dextran polymer through
the amine group of the N-succinyl chitosan polymer and the aldehyde
group of the aldehyde-derivatised dextran polymer. Preferably, the
N-succinyl chitosan polymer is N-succinyl chitosan.
[0198] The invention also provides a method of producing a polymer
network as described above.
[0199] To make a polymer network of the invention, the
dicarboxy-derivatised chitosan polymer is cross-linked to the
aldehyde-derivatised dextran polymer. This can be achieved by
mixing aqueous solutions of the two polymers. For example, see
Example 3.
[0200] Once made, aqueous solutions of each polymer component can
either remain in solution, or can be dried, for example by
freeze-drying, to product a solid product. The solid polymer
components can then be redissolved in aqueous solution before being
mixed together to form the hydrogel of the invention.
[0201] In one embodiment, it is desirable that the aqueous solution
in which the polymer matrix forms has a pH of about 6 to 8,
preferably between about 6.5 to 7.5. This can be achieved by
adjusting the pH of the separate aqueous solutions of the polymer
components to within this range before mixing the two solutions.
Alternatively, the pH of the aqueous solutions of the individual
polymer components can be adjusted following dialysis, prior to
freeze drying. The pH can be adjusted using any suitable base or
acid. Generally, the pH will be adjusted using NaOH.
[0202] In one embodiment either or both of the aqueous solutions
may independently contain one or more pharmaceutically acceptable
excipients. In one embodiment the aqueous solutions may
independently contain NaCl. Preferably, the concentration of NaCl
is between about 0.5 to 5% w/v. More preferably, the concentration
of NaCl is between about 0.5% to 2% w/v, most preferably about 0.9%
w/v.
[0203] In one embodiment the aqueous solutions may independently
contain one or more buffers including but not limited to phosphate
buffers such as Na.sub.2HPO.sub.4, acetate buffers, carbonate
buffers, lactate buffers, citrate buffers and bicarbonate
buffers.
[0204] 2.4 The Hydrogels of the Invention
[0205] The dicarboxy-derivatised chitosan polymer reacts with the
aldehyde-derivative dextran polymer, to produce a three-dimensional
cross-linked polymer network. This polymer network forms a hydrogel
with the aqueous solution in which it is formed. The hydrogel of
the invention has properties that make it suitable for use in
medicinal applications, in particular, wound healing, prevention of
surgical adhesions, and reducing bleeding (haemostasis).
[0206] Without being bound by theory, it is believed that
application of the hydrogel of the invention to a wound surface
prevents the formation of fibrin and blood clots within this space
thereby preventing subsequent formation of adhesions.
[0207] The properties of the hydrogel can be tailored for specific
applications by modifying the derivatisation and cross-linking of
the two polymers.
[0208] In the polymer networks of the invention, the amine groups
of the D-glucosamine residues of chitosan may be [0209] (a)
cross-linked to the aldehyde-derivatised dextran polymer, [0210]
(b) acylated with a dicarboxy group, or [0211] (c) acetylated (from
the original chitin material).
[0212] High degrees of acetylation and/or dicarboxy acylation will
leave less free amine groups to cross-link with the
aldehyde-derivatised dextran polymer. Consequently, when the
aqueous solutions of the two polymers are mixed, the amount of
polymerisation that occurs will be affected by the acylation and
acetylation patterns of the dicarboxy-derivatised chitosan polymer.
This in turn will affect how quickly, if at all, the hydrogel is
formed. If very little polymerisation occurs in a dilute solution
of the polymers, no hydrogel will be formed.
[0213] The aqueous solutions of dicarboxy-derivatised chitosan
polymer and aldehyde-derivatised dextran polymer comprise between
about 2% to about 10% w/v of each component.
[0214] Generally, aqueous solutions of equal concentrations of the
two polymers are mixed to form the hydrogel of the invention.
However, different ratios of dicarboxy-derivatised chitosan polymer
and aldehyde-derivatised dextran polymer can be used, provided the
properties of the two polymers are such that they cross-link to
form a hydrogel of the invention when mixed together.
[0215] A person skilled in the art can manipulate the parameters of
[0216] (a) degree of deacetylation of chitosan, [0217] (b) degree
of dicarboxy-derivatisation of chitosan, [0218] (c) degree of
oxidation of aldehyde-derivatised dextran, and [0219] (d)
concentration in aqueous solution,
[0220] so that the component polymer solutions rapidly cross-link
to form a hydrogel when mixed.
[0221] Alternatively, the person skilled in the art can manipulate
these parameters to ensure that the hydrogel forms slowly, or
within a given time period, if this is desirable.
[0222] Factors such as secondary derivatisation of the polymers,
the nature of the aqueous solutions and the addition of
biologically active or non-biologically active agents should also
be taken into consideration. For example, a hydrogel of the
invention may form more rapidly when the pH of the aqueous solution
comprising the mixed polymer components is between about 6 to
8.
[0223] Using the methods described herein by manipulating the
parameters discussed above, the inventors have made hydrogels of
the invention that form within a second or two of mixing the
solutions of the polymer components. Other hydrogels of the
invention form over a period of minutes, or even hours once the two
solutions have been mixed.
[0224] The dicarboxy-derivatised chitosan polymer and
aldehyde-derivatised dextran polymer solutions may be sterilised
before use, to ensure their application to a tissue does not
introduce microorganisms into the tissue. Alternatively, the
freeze-dried solid dicarboxy-derivatised chitosan polymer and
aldehyde-derivatised dextran polymer can be sterilised then
dissolved in sterilised aqueous solutions.
[0225] The solutions can be sterilised using any technique known in
the art. For example, by radiation sterlisation using gamma rays
from a radioisotope source (usually cobalt-60), or electron beam or
x-ray irradiation.
[0226] Exposure to radiation may cause chemical changes that can
affect the functioning of the dicarboxy-derivatised chitosan and
aldehyde-derivatised dextran polymers. For example, if free amine
groups are oxidised, less will be available for cross-linking
between the polymer components and it may take longer for a gel to
form. Radiation may also decrease the molecular weight of the
polymer components. These factors should be taken into account when
preparing dicarboxy-derivatised chitosan and aldehyde-derivatised
dextran components that are intended to form a hydrogel in a
certain time frame when mixed together in solution.
[0227] The hydrogel of the invention can also contain one or more
biologically active agents, and/or one or more non-biologically
active agents.
[0228] In one embodiment the one or more biologically active agents
are selected from the group comprising plasma proteins, hormones,
enzymes, antibiotics, antiseptic agents, antineoplastic agents,
antifungal agents, antiviral agents, antiinflammatory agents,
growth factors, steroids, cell suspensions, cytotoxins, and cell
proliferation inhibitors.
[0229] Biologically active agents incorporated into the hydrogel
matrix will be released when the hydrogel breaks down. In this way,
the hydrogel of the invention can be used to deliver biologically
active agents to a target area.
[0230] Non-biologically active agents can also be incorporated into
the hydrogel matrix. For example, polysaccharide thickeners such as
hydroxyethyl cellulose, carboxymethyl cellulose, guar gum, locust
bean gum, xanthan gum and the like, or polymer thickeners such as
polyacrylic acids and copolymers, polyacrylamides and copolymers,
alcohols, maleic anhydride copolymers and the like can be added to
produce a stiffer hydrogel.
[0231] Polysaccharide thickeners may also be added to the aqueous
solutions of the polymer components to ensure that the solutions
are of suitable viscosity for application. For example, if the
hydrogel is to be formed in situ on a target area such as a wound
or tissue, the aqueous solutions of the polymer components should
be sufficiently viscous that they do not drain away from before
cross-linking can occur. Therefore, if the particular
dicarboxy-derivatised chitosan polymer and/or aldehyde-derivatised
dextran polymer used form very non-viscous aqueous solutions, a
thickener may be used to increase the viscosity. In other
embodiments, the aqueous solutions of the polymer components will
be sufficiently viscous without the addition of a thickener.
[0232] Similarly, dyes such as fluoroscein and methylene blue can
be incorporated into the hydrogel matrix so that the precise
location and amount of the hydrogel applied can be ascertained.
[0233] These additional agents can be incorporated into the
hydrogel by any method known in the art. For example, if the agent
is a solid substance it can be blended with one of the dried
polymer components. The combined dried material is then dissolved
in the aqueous solution which is then mixed with the aqueous
solution of the second polymer component.
[0234] If the agent to be incorporated is a liquid, it can be
directly combined with one of the aqueous polymer solutions and
then freeze dried for storage. Alternatively, it can be added
directly to the mixture of aqueous polymer solutions before the
solutions are mixed to form the hydrogel of the invention.
[0235] It is also possible for an agent to covalently react with
one of the polymer components. If large amounts of agent are
present and an agent reacts with the free amine groups of the
N-succinyl chitosan, the resulting hydrogel may take longer to
form. However, any covalent reaction between the agent and the
polymer components must prevent cross-linking to the extent that
the hydrogel cannot form.
[0236] When the hydrogel degrades, the agent will be hydrolysed
from the polymer.
3. Using the Hydrogels of the Invention
[0237] In one aspect the invention provides a method of preventing
or reducing adhesion of tissue susceptible to adhesion formation
comprising treating the tissue with a hydrogel of the
invention.
[0238] In one embodiment the adhesion is post-surgical
adhesion.
[0239] In another aspect the invention provides a method of
reducing or stopping bleeding of a wound comprising treating the
wound with a hydrogel of the invention.
[0240] In one aspect the invention provides a method of
accelerating or promoting wound healing comprising treating the
wound with a hydrogel of the invention.
[0241] For the methods of the invention described above:
[0242] In one embodiment the hydrogels of the invention are
produced in situ. Aqueous solutions of the dicarboxy-derivatised
chitosan polymer and aldehyde-derivatised dextran polymer can be
simultaneously applied by, for example, spraying, squirting or
pouring the solutions onto the target area. The target area may be
a wound, in particular a surgical wound, or a tissue.
[0243] The two components meet and mix in the air, or on the
surface of the wound or tissue and react to produce a cross-linked
polymer network. Formation of the polymer network in aqueous
solution creates a hydrogel.
[0244] The solutions can be sprayed, squirted or poured onto the
target area using any means known in the art. When sprayed, the
aqueous solutions are simultaneously expelled from separate
containers in a mass of dispersed droplets. The containers may be
pressured. For example, PCT publication WO 00/09199 describes an
apparatus that permits spraying of two polymerisable fluids. The
apparatus sprays fluids stored in separate chambers so that the
fluids mix only in the emergent spray.
[0245] When squirted, the polymer-containing aqueous solutions are
simultaneously ejected from separate containers in a liquid stream.
For example, the aqueous solutions can be squirted onto a target
area using separate syringes and an applicator that allows the
solutions to mix at its tip as they are being applied to the target
area. Alternatively; the solutions can be simply poured onto the
target area.
[0246] The two polymer solutions should be applied simultaneously
but need not reach the target area in exactly the same quantities
at exactly the same time, provided that sufficient cross-linking
occurs to form a hydrogel.
[0247] The various methodologies and devices for performing in situ
gelation developed for other adhesive or sealant systems may be
used to apply the aqueous solutions of polymer to form the hydrogel
of the invention.
[0248] In another embodiment the hydrogel of the invention is used
by first mixing the dicarboxy-derivatised chitosan polymer with the
aldehyde-derivatised dextran polymer to form the polymer network in
aqueous solution and then applying the hydrogel that forms to the
area to be treated. The time taken between mixing the polymers and
applying the hydrogel depends on the speed at which the gel forms.
Any method known in the art can be used to apply the hydrogel to
the target area. For example, the hydrogel can be applied using a
wide-bore syringe.
[0249] In one embodiment, the amount of hydrogel used should be
sufficient to (a) reduce or minimise the number of adhesions in the
treatment area, (b) accelerate or promote healing of the wound to
which it is applied, or (c) reduce or stop bleeding of the wound to
which it is applied.
[0250] While the hydrogels of the invention can be used to reduce
or minimise tissue adhesions caused by any adhesion-forming event,
they are particularly useful for preventing or reducing
post-surgical adhesions.
[0251] The methods of the invention can be applied to treat any
organism. In one embodiment, the methods are applied to humans.
[0252] The ability of the hydrogels to reduce both bleeding and
adhesions, makes them a valuable tool in practically any surgical
procedure. Examples of surgical procedures in which the hydrogels
of the invention can be used include but are not limited to
abdominal procedures such as bowel surgery, thoracic procedures,
neurosurgical procedures including intercranial and spinal surgery,
nerve releasing procedures and procedures on the lining of the
brain, pelvic procedures such as ovarian cystectomy and
hysterectomy, sinus surgery, ophthalmic procedures, otologic
procedures, neck and laryngeal procedures such as vocal fold and
cord procedures, orthopaedic procedures such as division of
adhesions on flexor and extensor tendons and burns procedures.
[0253] The hydrogel of the invention is particularly suited for use
in ear, nose and throat surgery. A weakness of gel formation in
sinuses is that mucociliary clearance will slowly clear gels from
the surface of the sinus. The ciliary beating of the nasal
mucociliary clearance system acts to transport the mucus layer that
covers the nasal epithelium towards the nasopharynx. In doing so,
any substances applied to the surface of the sinuses will be
similarly expelled. The hydrogels of the invention become quite
firm soon after application and therefore resist being cleared away
by the nasal mucociliary clearance system.
[0254] Once applied, the hydrogel of the invention maintains a
physical barrier between internal tissues to prevent adhesions. As
the tissue surfaces heal, the hydrogel degrades and is eliminated
from the site.
[0255] The hydrogels of the invention can also be applied to
dermatological and cutaneous wounds, either directly, or by using a
wound dressing incorporating the hydrogel.
[0256] 3.1 Delivery of Biologically Active Agents Using the
Hydrogels of the Invention
[0257] The hydrogels of the invention can be used as site-directed
controlled release carriers for biologically active agents.
Accordingly, one aspect the invention provides a method of
delivering one or more biologically active agents to a tissue
comprising treating the tissue with a hydrogel of the invention
wherein the hydrogel contains one or more biologically active
agents.
[0258] Site-directed delivery of the biologically active agent can
reduce the side-effects associated with conventional systemic
administration and ensure that a therapeutically effective amount
of the biologically active agent reaches the affected area. For
example, the polymer network of the invention can be used to treat
chronic venous insufficiency and leg ulcers. Pro-angiogenic and
epithelial growth factors incorporated into the polymer network can
assist in healing ulcers. The polymer network of the invention may
be applied directly to the wound as a gel, or incorporated into a
wound healing dressing, for application to the wound.
[0259] Biologically active agents that can be incorporated into the
polymer network of the invention include but are not limited to
plasma proteins, hormones, enzymes, antibiotics, antiseptic agents,
antineoplastic agents, antifungal agents, antiviral agents, anti
inflammatory agents, growth factors, anesthetics, steroids, cell
suspensions, cytotoxins and cell proliferation inhibitors.
[0260] The biologically active agent may act in conjunction with
the polymer of the invention to contribute to wound healing. For
example, antibiotics such as tetracycline, ciprofloxacin and the
like; growth factors such as heparin binding growth factors,
including the fibroblast growth factors; platelet-derivated growth
factors, insulin-binding growth factor-1, insulin-binding growth
factor-2, epidermal growth factor, transforming growth
factor-alpha, transforming growth factor-beta, platelet factor 4
and heparin binding factors 1 and 2, can all be incorporated into
the polymer network of the invention.
[0261] Other biologically active agents that can be used include
but are not limited to antifungal agents such as nystatin,
diflucan, ketaconizole and the like; antivirals such as
gangcyclovir, zidovudine, amantidine, vidarabine, ribaravin,
trifluridine, acyclovir, didexoyuridine and the like;
anti-inflammatory agents such as alpha-1-antitrypsin,
alpha-1-antichymotrypsin and the like; cytotoxins or cell
proliferation inhibitors such as 5-fluorouracil, taxol, taxotere,
actinomycin D, andriamycin, azaribine, bleomycin, busulfan, butyric
acid, carmustine, chlorambucil, cis-platin, cytarabine, cytarabine,
dacarbazine, estrogen, lomustine, emlphalan, mercaptopurine,
methotrexate, mitomycin C, prednisilone, prednisone, procarbazine,
streptozotocin, thioguanine, thiotepa, tributyrin, vinblastine,
vincristine, gentamycin, carboplatin, cyclophosphamide,
ifosphamide, maphosphamide, retinoic acid, ricin, diphtheria toxin,
venoms and the like; hormones such as estrogen, testosterone,
insulin and the like; steroids such as beclomethasone,
betamethasone, budesonide, cortisone, dexamethasone, fluticasone,
hyudrocortisone, methylprednisolone, memetasone,
prednisone/prednisolone, triamcinolone and the like; plasma
proteins such as albumin; immunoglobulins, including immunoglobulin
A, M and G; fibrinogen; coagulation factors, including Factors II,
VII, VIII, IX, X and XIII; lasmoinogen; protein C; protein S;
plasma proteinase inhibitors, including anti-thrombin III,
.alpha.1-antitrypsin, .alpha.2-macroglobulin, and C1 esterase
inhibitor; .alpha.1-acid glycoprotein; ceruloplasmin; haptoglobin;
transferring; complement components C1 through C9l C4b binding
protein; interalpha-trypsin inhibitor; apolipoproteins, including
A-1, A-11, B, C and E; fibronectin and angiostatin.
[0262] The hydrogels of the invention may also include nutritional
supplements such as peptides, proteins, simple carbohydrates,
complex carbohydrates, lipids, glycolipids, glycoproteins, vitamins
and minerals.
[0263] Incorporation of the biologically active agent into the
hydrogels allows site-directed delivery of the agent. The rate of
release can also be controlled by tailoring the degradation rate of
the hydrogel.
[0264] The biologically active agent can be added to the hydrogel
of the invention by any means known in the art. For example, by
adding the agent to one polymer component solution before mixing
the solutions together. The means of incorporation will depend on
the nature of the biologically active agent.
[0265] The concentration of the biologically active agent to be
added will vary depending on the nature of the agent, the site to
which it is to be applied and the physical characteristics of the
hydrogel. The concentration should be sufficient such that a
therapeutically effective amount of the biologically active agent
is delivered to the target site. In one embodiment the
concentration of the biologically active agent is between about 1
ng/ml to about 1 mg/ml of the hydrogel. Preferably, the
concentration of the biologically active agent is between about 1
ug/ml to about 100 ug/ml of the hydrogel. The appropriate amount of
the biologically active agent to be added can be calculated by one
of skill in the art by testing hydrogels containing various
concentrations of biologically active agents and selecting the
hydrogel that is most effective for the particular purpose.
[0266] The physical properties of the hydrogel of the invention
ensure it will remain substantially in the same location as it is
applied and will not quickly be flushed away by liquids in the body
or sink due to gravity. The hydrogel will mould itself around the
tissue to which it is applied, ensuring contact with the entire
surface of the tissue.
4. Kits
[0267] In another aspect the invention provides a kit for use in
the methods of the invention wherein the kit comprises: [0268] (a)
a dicarboxyl-derivatised chitosan polymer, and [0269] (b) an
aldehyde-derivatised dextran polymer.
[0270] The kits of the invention conveniently provide the polymer
components that cross-link to form the hydrogel of the invention in
aqueous solution.
[0271] In one embodiment the kits of the invention also comprise an
aqueous solution into which polymers (a) and (b) can be dissolved
to cross-link and form the hydrogel. Alternatively, the kits of the
invention may provide (a) and/or (b) pre-dissolved in aqueous
solution, ready for mixing with the second polymer component. The
aqueous solutions can be provided in liquid or frozen form.
[0272] In one embodiment, the kits of the invention provide polymer
components (a) and (b) as freeze-dried powders. To use the kits of
the invention, the freeze-dried polymers are dissolved in a
suitable aqueous solution and then mixed together. Alternatively,
both (a) and (b) can be added to a suitable aqueous solution and
mixed until dissolved and cross-linked. In one embodiment the
aqueous solution is selected from the group comprising water,
saline, buffer and mixtures thereof.
[0273] In one embodiment the kits of the invention may also
comprise one or more biologically active agents. For example, the
one or more biologically active agents can be incorporated into one
or both of the polymer components (a) and (b). Alternatively, the
one or more biologically active agents may be present in the
aqueous solution in which (a) and/or (b) are to be dissolved.
5. Wound Dressings
[0274] The invention also provides wound dressings capable of
releasing a hydrogel of the invention when moistened. The wound
dressing can be any suitable dressing known in the art. Examples
include bandages, strips, pads, gauzes, films, stockings and
tape.
[0275] In one aspect the wound dressing comprises a
dicarboxy-derivatised chitosan polymer and an aldehyde-derivatised
dextran polymer. Preferably the dicarboxy-derivatised chitosan is
N-succinyl chitosan.
[0276] To prepare a wound dressing of the invention, the dried
solid dicarboxy-derivatised chitosan polymer and the
aldehyde-derivatised dextran polymer are blended into the structure
of the dressing. Alternatively, the wound dressing can be soaked in
an aqueous solution of one polymer and then dried, with the second
polymer being introduced as a matt. The matt can be held together
by a third component, for example, a water soluble glue. As another
alternative, the two polymers can be dried and mixed, then placed
between two pieces of very porous tissue as part of the structure
of the wound healing dressing.
[0277] When the wound dressing is moistened, the two polymer
components cross-link and form a hydrogel in the aqueous component
of the wound dressing. The wound dressing can be moistened either
by external or internal fluids. For example, when placed on the
wound the wound dressing may be moistened by contact with blood
from the wound or wound exudate. If the wound is not sufficiently
moist, the wound dressing can be moistened by contact with a
suitable physiologically-acceptable liquid such as water or saline
solution.
[0278] The rate at which the hydrogel forms can be altered by
altering the component polymers. Different applications of the
wound dressing may require different rates of hydrogel
formation.
[0279] Pressure applied to the wound dressing may assist in
hydrogel formation.
[0280] The wound dressing may contain additional agents such as
antiseptics and other biologically active agents, as discussed
above. These agents can be incorporated into the dressing materials
using standard methods known in the art, or may be incorporated
into the polymer solutions that are blended into the structure of
the dressing.
[0281] Various aspects of the invention will now be illustrated in
non-limiting ways be reference to the following examples.
EXAMPLES
Example 1
N-Succinyl Chitosan Polymer
DMF Method
[0282] Batch A. Succinic anhydride (2.15 g, 0.0215 mol) was added
to chitosan (1.5 g, 0.007 mol) in 100 ml N,N-dimethylformamide
(DMF). The mixture was heated to 150.degree. C. under nitrogen for
3 hrs.
[0283] On cooling the solid was collected from the mixture and
washed with methanol then acetone. The dried solid was dissolved in
sodium hydroxide (400 ml, 2M) and the solution stirred overnight.
Not all of the solid dissolved. The undissolved solid was filtered
and the solution evaporated to about 30-50 ml.
[0284] The solution was dialysed in a 3 L beaker by dialysis bag
for 48-60 hours with the water changed periodically. The solution
was then concentrated and freeze-dried. The N-succinyl-chitosan
product was obtained as a cotton-like solid.
[0285] Batch B. Chitosan (from squid pens) (30 g) and succinic
anhydride (42 g) in DMF (500 ml) was heated to 140.degree. C. for
20 hrs. The resulting N-succinyl chitosan was recovered by
filtration and washed with ethanol and then diethyl ether and dried
at the pump. The dried solid was added to a solution of sodium
hydroxide (10 g in 800 ml water) and stirred overnight. The
solution was filtered through celite and dialysed for 3 days with
the water changed every 12 hrs. Lyophilization produced 14 g of
N-succinyl chitosan (analysed C, 39.2%; H, 5.9%; N, 5.1%)
[0286] Batch C. Chitosan (30 g, practical grade Aldrich, medium
molecular weight) and succinic anhydride (42 g) were heated to
130.degree. C. in DMF (1 L) for 3 hours. The chitosan swelled but
did not dissolve. On cooling the chitosan was filtered off, and
washed with methanol on the filter. The chitosan was then added to
a solution of NaOH (50 g in 1.5 L of water) and mixed with a high
speed overhead stirrer until homogenous (usually 30 minutes).
Occasionally the chitosan is not all soluble in which case any
remaining gel is removed by filtration through celite. The solution
was heated to 50.degree. C. for 14 h and was dialysed in cellulose
tubing for 3 days in distilled water (4 changes of 50 L). The pH
was adjusted to 8.0 with a little sodium hydroxide. The solution
was then reduced in volume to ca. 700 mL under reduced pressure on
a rotory evaporator to give a very thick solution, and then freeze
dried to yield ca. 35 g product.
[0287] N-Succinyl Chitosan (Methanol Method)
[0288] Chitosan (Aldrich, practical grade) (20 g) was dissolved in
lactic acid (20 ml) and water (650 ml) by stirring for 3 hr.
Methanol (650 ml) was added and the mixture was warmed to
35.degree. C. Succinic anhydride (29 g) was added and the mixture
stirred vigorously for 4 hr at 35.degree. C. The succinic anhydride
took a few hours to dissolve. A solution of sodium hydroxide (35 g
in 300 ml water) was added and the mixture stirred vigorously for 1
hr. The cloudy partially gelled mixture that resulted was dialysed
for 1 day to remove the methanol, then vigorously stirred to break
up the remaining final gel and dialysed in distilled water for a
further 3 days (with a change of water every 12 hr) and filtered.
Lyophilization gave the product (16.5 g).
Example 2
Aldehyde-Derivatised Dextran
[0289] Batch A. Dextran (1 g, MW 60,000-90,000) was dissolved in 20
ml distilled water. Sodium periodate (2 g) was added to the
solution which was stirred for 3 hours at room temperature. The
solution was dialysed in a 3 L beaker overnight with the water
changed periodically. The solution was then concentrated and
freeze-dried to give aldehyde-derivatised dextran as a white
powder.
[0290] Batch B. Dextran (20 g, Aldrich, Mn 21,500, MW 142,000) was
dissolved in water (200 ml) and then added to a stirring mixture of
sodium periodate (40 g in 200 ml). The temperature of the
exothermic reaction was kept at below 35.degree. C. by external
cooling and the reaction was performed under nitrogen. After 3 hr,
the solution was dialyzed for 3 days (water changed every 12 hr),
filtered and lyophilized to give aldehyde-derivatised dextran as a
white powder (14.7 g, found C, 39.8%; H, 5.9%). The final molecular
weight was M.sub.n 2570, MW 4700.
[0291] Batch C. Dextran (36 g, Aldrich food grade, mw 80,000) was
stirred vigorously in water (800 mL) while solid sodium periodate
(50 g) was added. The exothermic reaction was controlled by
external cooling so that the temperature stayed under 30.degree. C.
After 2 h the solution was filtered, and dialysed in cellulose
tubing for 3 days (4 changes of 50 L distilled water). The pH was
adjusted to 8.0 with a little sodium hydroxide, and the solution
reduced in volume under reduced pressure to ca. 300 mL, and freeze
dried. The yield was ca. 30 g.
Example 3
Polymer Network Comprising N-Succinyl Chitosan Cross-Linked with
Aldehyde-Derivatised Dextran Polymer in Aqueous Solution
[0292] N-succinyl chitosan from Example 1 (30 mg) was dissolved in
0.6 ml distilled water to make a 5% w/v aqueous solution (Solution
A). Aldehyde-derivatized dextran polymer (30 mg) was dissolved in
0.6 ml distilled water to make a 5% w/v aqueous solution (Solution
B).
[0293] Solution A and Solution B were mixed together until a
hydrogel formed (approximately 2 minutes). The hydrogel is the
polymer network comprising N-succinyl-chitosan cross-linked with
aldehyde-derivatised dextran polymer in aqueous solution.
Example 4
Effect of Base Treatment on Functional Group Levels of N-Succinyl
Chitosan and Gel Time of Hydrogel
[0294] N-succinyl chitosan was prepared in accordance with Example
1 (DMF method-Batch C), but the solution of chitosan and NaOH was
heated for 14 hours at the temperatures shown in Table 1 below.
Table 1 shows that higher temperatures result in greater
deacylation and hence a higher proportion of free amine groups. The
relative properties of free amine groups to acetyl and N-succinyl
groups was determined by 'H nmr.
[0295] Hydrogels prepared by cross-linking of the N-succinyl
chitosan and aldehyde-derivatised dextran in accordance with
Example 3 were formed faster where the N-succinyl chitosan has a
higher proportion of free amines.
TABLE-US-00001 TABLE 1 Effect of base treatment on functional group
levels of N-succinyl chitosan and gel formation of hydrogel time
Mol % acetyl Mol % succ Mol % free Gel time Temp groups groups
amine (s) no base 16 93 0 -- treatment 35.degree. C. 15 91 trace --
55.degree. C. 11 81 12 35 65.degree. C. 5 75 22 5
Example 5
Effect of Mol % Periodate on Aldehyde Derivatisation of Dextran and
Gel Formation Time for Hydrogel
[0296] Aldehyde-derivatised dextrans were prepared in accordance
with Example 2, but different mol % of periodate were used. The
reactions took place at room temperature for two hours. Table 2
shows the molecular weight of the resulting aldehyde-derivatised
dextran, the mol % of aldehyde groups, and the time taken to form a
hydrogel when a solution of the aldehyde-derivatised dextran is
mixed with a solution of N-succinyl chitosan.
TABLE-US-00002 TABLE 2 Mol % Periodate Mol % aldehyde (2 h, rt) MW
dextran (Mn) groups Gel time (s) 0 95,500 0 -- 26 20,270 32 220 52
14,059 75 70 78 10,010 118 45 105 3700 165 35
[0297] The theoretical maximum mol % of aldehyde groups present per
chitosan residue is 200 which would be achieved if every mol of
periodate reacted with one chitosan residue. A mol % of 200
represents 100% oxidation (or 100% aldehyde-derivatisation).
Example 6
Effect of Hydrogel on Adhesions Following Endoscopic Sinus Surgery
in Sheep
[0298] Standardised full thickness mucosal wounds were made in 20
sheep (merino cross wethers) using a well established endoscopic
sinus surgery wound healing protocol. Each sheep was given two
lateral nasal wall injuries and one ethmoidal injury on each side.
The injured regions were randomized to 4 treatment groups and
treated with one of (a) control (no treatment), (b) SprayGel.TM.,
(c) recombinant tissue factor, and (d) the hydrogel of the
invention.
[0299] For groups (b), (c) and (d) 5 ml of active agent was sprayed
onto the surface of the wound using a mucosal atomization device.
SprayGel.TM. and the hydrogel of the invention were each sprayed as
two separate liquid components which combined in the spray
instantly to form a mucoadhesive gel.
[0300] The sheep were assessed at day 28, 56, 84 and 112. At each
review the sheep were moderately sedated using an intramuscular
injection of 4 mg xylazine. The nasal cavity was inspected at each
of these 4 weekly visits with the presence of adhesions noted,
their location recorded and each adhesion graded by an independent
observer (animal lab technician) according to a previously
published grading scheme (Table 3).
TABLE-US-00003 TABLE 3 Grading scheme for sheep nasal adhesions
Grade 1 Less than 25% of middle turbinate height Grade 2 25-50% of
middle turbinate height Grade 3 More than 50% of middle turbinate
size
[0301] Brushings of ciliated cells were collected from four regions
in each sheep under endoscopic vision at a site distant from biopsy
using a cytobrush plus cell collector (Medscand Medical, Sweden)
without local anesthetic. Sites of brushings were carefully ordered
and recorded during the 16 week period in order to sample untouched
areas.
[0302] Four sprays of a combination anesthetic and decongestant
spray (co-phenylcaine--ENT technologies) were applied to each nasal
cavity prior to biopsy of the lateral nasal wall injury sites. An
incision was made and a small flap raised using a sharpened Freer
elevator and two biopsy specimens taken from each injury site using
punch biopsy forceps. Biopsies were taken at each four week
interval with biopsy sites carefully ordered and recorded during
the sixteen week period in order to sample untouched areas.
Following the final biopsy, euthanasia was performed by intravenous
injection of sodium pentobarbitone (>100 mg/kg).
[0303] Specimens for light microscopy were fixed in formalin for 4
hours, then placed in 70% ethanol and processed. Specimens were
embedded in paraffin blocks, sectioned at 4 .mu.m thickness and six
to eight sections mounted on 2 glass slides for each biopsy
specimen. They were then stained with Hematoxylin and Eosin
(H&E). Each specimen was examined under light microscopy using
image capture software (Image Master Pro). The percentage
re-epithelialisation was calculated by measuring the length of the
nasal mucosal surface area with lamina propria and the length of
this surface that had an epithelial covering. Four random sections
were measured for each biopsy specimen. Epithelial height was also
measured using these same digital images. Four random areas of
epithelium from one section were measured for each specimen using
the basement membrane and apical surface of the epithelium as
markers.
[0304] Specimens for scanning electron microscopy (SEM) were placed
in phosphate buffered saline and then washed for 20 minutes using
an ultrasonic cleaner in order to remove blood clot, mucous, debris
and biofilm. The specimens were then fixed in a solution of 4%
paraformaldehyde/1.25% gluteraldehyde in phosphate buffered saline
+4% sucrose, pH 7.2, and stored at 4.degree. C. until processed.
Processing involved progressive dehydration of the specimen using
osmium tetraoxide, followed by increasing concentrations of ethanol
(70&, 90%, 95%, 100% & 100%) using microwave technology
(PELCO BioWave.RTM.) for more rapid processing. After this the
specimens were dried using a carbon dioxide critical point dryer
and then mounted on EM stubs. Finally specimens were coated with
gold and carbon. Each specimen was examined by SEM (Phillips XL30
Field Emission Scanning Electron Microscope) and four surface
images taken at 500.times. magnification. Specimens were graded
according to a previously published grading scale. If clarification
was required specimens were also examined at higher magnification
of 2000.times. and 5000.times.). Four pictures for each specimen
(at 500.times. magnification) were used to calculate the percentage
surface area covered by cilia using image analysis software and a
previously validated technique. (Macintosh D, Cowin A, Adams D,
Wormald P J, Am. J. Rhinol. 2005, 19(6), 557-81).
[0305] Cells from brushings were suspended in 1 ml of Dulbecco's
culture medium and agitated to release cells into the culture
medium. This was kept at 36.5.degree. C. until CBF analysis was
performed. Twenty .mu.l from each specimen was placed on a
microscope slide warmed to 36.5.degree. C. and phase contrast
microscopy was used. Ten cells per specimen were individually
analyzed and the average of these taken as the CBF.
[0306] The well being of the sheep participating in this study was
monitored by animal house veterinary staff experienced in handling
sheep. Sheep were monitored four times a day for 2 days after the
application of the agents for temperature, heart rate, mobility and
oral intake. Following this they were monitored twice daily for the
remainder of the study for mobility and oral intake.
[0307] Statistical Analysis
[0308] Two way ANOVA with Bonferroni correction post tests were
conducted for analyzing epithelial height, re-epithelialisation,
re-ciliation, cilial grade and lateral nasal wall adhesion
percentage and grade. Wilcoxon signed ranks test was used to
analyze matched pairs in ethmoidal adhesion rates. Statistical
significance was set at p<0.05.
[0309] The results are shown in FIGS. 1-5.
[0310] Results
[0311] The percentage of sheep in each group with adhesions on the
lateral nasal wall over time is shown in FIG. 1. With the full
thickness injury methods used the control group had an adhesion
rate of 15%, the tissue factor group had an adhesion rate of 25%,
while the SprayGel.TM. group had a rate of 10%. The hydrogel group
had an adhesion rate of 10%, however this reduced to 5% at day 56
and remained at this level throughout the study. The hydrogel group
had a significantly lower percentage of adhesions than the tissue
factor group at day 56, 84 and 112 (5% vs 25%, p<0.05).
[0312] The mean grade of adhesions trended to less severe in the
SprayGel.TM. group and even less severe in the hydrogel group,
however these differences were not significant (FIG. 2).
[0313] Ethmoidal adhesion rates for each group over time are shown
in FIG. 3. With the method described above a 40% ethmoidal adhesion
formation rate was established in the control groups. This
increased to 50% in the tissue factor group. The SprayGel.TM. group
had a lower adhesion rate of 14%, however the hydrogel group
experienced no ethmoidal adhesions. Despite the small numbers in
this matched pairs study the hydrogel group experienced
significantly less adhesions than the tissue factor group (0% vs
50%, p<0.05), see FIG. 4.
[0314] When analyzing epithelial height over time with light
microscopy, no significant difference was seen between the four
groups (FIG. 5).
[0315] The percentage of mucosa which had re-epithelialised for
each group can be seen in FIG. 6. The hydrogel group had a
significantly greater percentage of re-epithelialisation at day 28
compared to the tissue factor group (70% vs 33%, p<0.001). In
addition, the SprayGel.TM. group had significantly greater
re-epithelialisation at day 84 than the tissue factor group (89% vs
61%, p<0.05).
[0316] FIG. 7 shows the percentage surface area (mean.+-.standard
deviation) that was re-ciliated over time for each of the four
groups. At day 28 the hydrogel group was significantly more
ciliated than control (62% vs 31%, p<0.01) and than tissue
factor (62% vs 23%, p<0.001) while the SprayGel.TM. group also
had significantly greater ciliated surface area than tissue factor
(47% vs 23%, p<0.05). At day 56 the hydrogel group remained
significantly more ciliated than the tissue factor group (67% vs
40%, p<0.05). Overall the hydrogel group trended towards
improved re-ciliation, although this was not significant at all
time points.
[0317] On average 1-2 specimens per group at each time point were
unusable and given a grade of 5. Table 4 below shows the grading
scale for scanning electron microscopy (SEM) images of sheep nasal
cilia.
TABLE-US-00004 TABLE 4 Grading scale for scanning electron
microscopy (SEM) images of sheep nasal cilia Grade Appearance on
SEM I Normal cilia with normal orientation II Ciliated epithelium
but disoriented III Stumps of cilia, regenerating cilia IV No
identifiable cilia V Unusable (crust or clot covering
epithelium)
[0318] Two-way ANOVA revealed no significant difference between the
numbers of unusable specimens for each group at each time point
therefore these were excluded from the subsequent analysis (data
not shown). FIG. 8 shows the mean.+-.SD cilial grade for each group
at each time point. At day 84 the mean cilial grade for
SprayGel.TM. was significantly better than for tissue factor (1.8
vs 2.6, p<0.05) and at day 112 the mean grade for hydrogel was
significantly better than control (1.9 vs 2.7, p<0.05).
[0319] Mean CBF was not significantly different between any of the
four groups over time (FIG. 9). The hydrogel group trended towards
improved ciliary function at all time points, however this was
non-significant.
[0320] Importantly, none of the sheep experienced any adverse
events during this study. There were no reports of fever,
tachycardia, poor mobility or poor oral intake during the study
period.
[0321] Discussion
[0322] Both SprayGel.TM. and the hydrogel of the invention
exhibited some adhesion prevention properties. Hydrogel in
particular showed significantly decreased adhesion formation both
on the lateral nasal wall and the anterior ethmoids compared to
tissue factor.
[0323] In terms of wound healing the results followed a similar
pattern with both hydrogel and SprayGel.TM. having improved rates
of re-epithelialisation, re-ciliation and cilial grade compared to
control and especially compared to tissue factor. The most striking
feature of wound healing was the speedy recovery of the hydrogel
groups epithelium, reflected in the significantly greater
re-epithelialisation and percentage surface area which was
re-ciliated at day 28. Early on in this study the cilial grades of
all four groups were not significantly different, however in the
latter part of the study the hydrogel group had a significantly
improved grade of cilia compared to tissue factor and control.
Example 7
Human Trials
[0324] A prospective randomised controlled pilot trial was
performed. Six patients undergoing full house endoscopic sinus
surgery were randomised to receive 20 ml of hydrogel while the
contralateral side received no treatment. The solution was applied
under endoscopic vision as a spray at the conclusion of the
operating on each side. Bleeding after application was documented
using standardised videoendoscopy and graded on 2 previously
validated scales every 2 minutes up to a maximum of 10 minutes.
[0325] Results
[0326] The hydrogel showed a clinically significant improvement in
the surgical field at 4, 6, 8 and 10 minutes after application (see
Table 5 and FIGS. 10 and 11).
TABLE-US-00005 TABLE 5 Bleeding scores of placebo vs active sides
for 6 patients using surgical field bleeding scales Time Boezaart
bleeding scale Wormald bleeding scale (mins) Placebo Active p value
Placebo Active p value Baseline 2.33 2.17 0.71 4.17 4 0.71 2 1.83
0.83 0.096 3.67 1.17 0.093 4 1.83 0.67 *0.037 3.5 1 0.058 6 1.83
0.33 *0.041 3.17 0.67 0.041 8 1.67 0.33 *0.039 2.67 0.5 0.039 10
1.67 0.33 *0.039 2.5 0.5 0.041
[0327] Further, the hydrogel of the invention was regarded by the
surgeon as being more effective than placebo in 5 out of 6 cases,
with one case regarded as no different. Other parameters known to
affect haemostasis such as mean arterial pressure, heart rate and
end tidal CO.sub.2 were not significantly different between placebo
and active sides.
Example 8
Effect of Hydrogel on Hemostatis Following Endoscopic Sinus Surgery
in Sheep
[0328] Twenty one sheep (merino cross wethers) infested with the
nasal bot fly Oestrus ovus participated in this study. Nasal bot
fly infection was visually confirmed by nasal endoscopy and
eosinophilic sinusitis documented with nasal swabs stained with
Leishman stain. General anaesthesia was induced via injection of
sodium thiopentone (19 mg/kg body weight) into the jugular vein.
Endotracheal intubation then followed with anaesthesia maintained
by inhalation of 1.5-2.0% halothane. The middle turbinate was
removed prior to a standardized mucosal injury being created
between the anterior ethmoid complex and the walls of the nasal
cavity by the use of a microdebrider (Medtronic ENT, Jacksonville,
Fla.). The duration of performance of the injuries on both sides
were timed for a period of 30 seconds using a stopwatch.
Immediately following mucosal injury a baseline surgical field
grade was determined by an independent observer using the Boezaart
Surgical Field Grading Scale (Boezaart A P; Van Der Merne J,
Coetzee A, Comparison on sodium nitroprusside and esmolol induced
controlled hypertension for functional endoscopic sinus surgery.
(Can J Anaesth 1995, 42, page 373-376) (Table 6).
TABLE-US-00006 TABLE 6 Boezaart surgical field grading scale Grade
Assessment 0 No Bleeding (cadaveric conditions) 1 Slight Bleeding -
no suctioning required 2 Slight Bleeding - occasional suctioning
required. 3 Slight Bleeding - frequent suctioning required.
Bleeding threatens surgical field a few seconds after suction is
removed. 4 Moderate Bleeding - frequent suctioning required and
bleeding threatens surgical field directly after suction is
removed. 5 Severe Bleeding - constant suctioning required. Bleeding
appears faster than can be removed by suction. Surgical field
severely threatened and surgery usually not possible.
[0329] Each nasal cavity was computer randomized to receive either
no treatment (control) or 5 ml of the hydrogel of the invention
applied to the ethmoid region immediately following baseline
surgical field grade calculation. The hydrogel of the invention was
stained with Flourescein to aid in visualisation. A surgical field
grade was calculated for each side every two minutes following
baseline grading until bleeding ceased or up to a maximum of ten
minutes observation.
[0330] Sheep were extubated and returned to their individual pens.
Sheep were monitored three times daily, with variables such as food
intact, nasal discharge and temperature observed. Trained animal
handlers documented ongoing blood stained nasal discharge for the
following 2 post-operative weeks. Each post-operative day all sheep
were sedated and videoendoscopy performed documenting the presence
of crusts/gel in wound site. This was then graded on a 3 point
graduated scale from 0-2 (Table 7). Daily observation was continued
for a period of 14 post-operative days.
TABLE-US-00007 TABLE 7 Ethmoid complex crust/gel dissolution Grade
Assessment 0 No crust/gel presence between ethmoid surfaces. 1 Less
than 50% surface area of ethmoid complex covered by crust/gel. 2
More than 50% surface area of ethmoid complex covered by
crust/gel.
[0331] Results
[0332] The surgical field grade scores were analysed using GraphPad
Prism and SPSS 11.0. As the data was not normally distributed,
paired tests for non-parametric data using the Wilcoxon Signed
Ranks Test were used to analyse the difference in surgical grade
between sides. Bonferroni correction for multiple testing was
applied to all analyses of surgical grade and statistical
significance was set at p<0.05. Students T-test was used to
compare means of time to complete hemostasis.
[0333] Comparison of Hemostasis with Control Vs Hydrogel of the
Invention Over Time
[0334] Twenty one sheep (merino cross wethers) participated in this
part of the study. There was no significant difference in the
baseline bleeding times between control vs hydrogel (2.4.+-.0.67 vs
2.4.+-.0.74). The hydrogel side was significantly more hemostatic
at 2, 4 and 6 minutes after application. The Mean grading scores
and 95% confidence intervals with control vs hydrogel were at 2
minutes--1.6(.+-.0.92) vs 0.9(.+-.0.53), at 4
minutes--1.0(.+-.0.66) vs 0.24(.+-.0.43) and at 6
minutes--0.4(.+-.0.59) vs 0.048(.+-.0.21) (p<0.05) (FIG.
12).
[0335] Time to Complete Hemostasis
[0336] All the hydrogel sides had complete hemostasis by 6 minutes.
Average time to hemostasis was significantly better for the
hydrogel side at 4.09 (.+-.1.61) vs 6.57 (.+-.2.20) for the control
sides (p=0.049) (FIG. 13). Ongoing bleeding on the control side was
noted on 3 sides at 8 minutes and 1 at 10 minutes. This compares to
no further bleeding past 6 minutes on the hydrogel side.
[0337] One sheep died on the 5.sup.th post-operative day. This was
found to be from aspiration of stomach contents at post-mortem.
There was no evidence of bleeding in this sheep. In the remaining
sheep there was no ongoing blood stained nasal discharge past the
first post-operative day, and no sheep was noted to have excessive
ongoing bleeding requiring intervention.
[0338] Crust/Hydrogel Dissolution Scores
[0339] Twenty sheep participated in this part of the study. There
was no significant difference between mean crust on the control
side and the hydrogel dissolution scores on post operative day 1,
3, 7 and 14. The mean crust/hydrogel dissolution scores and 95%
confidence intervals with control vs hydrogel were at day
1--2.0(.+-.0.00) vs 1.9(.+-.0.31), at day 3--1.6(.+-.0.60) vs
1.65(.+-.0.59), at day 7--0.47(.+-.0.61) vs 0.53(.+-.0.70) and at
day 14--0.00(.+-.0.00) vs 0.05(.+-.0.22) (FIG. 14).
CONCLUSION
[0340] In the sheep model of chronic sinusitis, the hydrogel of the
invention significantly improves hemostasis compared to control at
2, 4 and 6 minutes following mucosal injury. It also displays
similar crust dissolution characteristics when compared to control.
Combining the known positive effects on wound healing, with its
significant hemostatic effects, the hydrogel of the invention shows
great potential as a post operative wound dressing following ESS in
patients undergoing ESS.
INDUSTRIAL APPLICABILITY
[0341] The invention provides a water-based biodegradable hydrogel
that can be applied to wounds to assist wound healing and
prevention of adhesions. The hydrogels also have a positive effect
on haemostasis and can be applied to bandages and field dressings
to help stop bleeding in hemorrhaging trauma wounds, and post
surgery.
[0342] The hydrogels of the invention are suitable for application
during surgical procedures. Their use can improve the outcome of
patients undergoing surgery.
[0343] The hydrogels of the invention can be easily prepared by
non-medically trained people and can be used in emergency
situations to prevent excessive blood loss in a victim until the
victim can be transported to a medical facility.
* * * * *