U.S. patent application number 10/910696 was filed with the patent office on 2005-01-06 for compositions comprising a tissue glue and therapeutic agents.
Invention is credited to Filler, Aaron Gershon, Lindsay Lever, Andrew Michael.
Application Number | 20050002860 10/910696 |
Document ID | / |
Family ID | 27517252 |
Filed Date | 2005-01-06 |
United States Patent
Application |
20050002860 |
Kind Code |
A1 |
Filler, Aaron Gershon ; et
al. |
January 6, 2005 |
Compositions comprising a tissue glue and therapeutic agents
Abstract
The present invention concerns compositions comprising a
radiotherapeutic agent, or an agent which can be converted to a
radiotherapeutic, and a tissue glue. The compositions of the
present invention are particularly useful for providing local
radiotherapy. The present invention also concerns methods of using
the compositions of the invention, particularly for
radiotherapy.
Inventors: |
Filler, Aaron Gershon; (Los
Angeles, CA) ; Lindsay Lever, Andrew Michael;
(Cambridge, GB) |
Correspondence
Address: |
SALIWANCHIK LLOYD & SALIWANCHIK
A PROFESSIONAL ASSOCIATION
PO BOX 142950
GAINESVILLE
FL
32614-2950
US
|
Family ID: |
27517252 |
Appl. No.: |
10/910696 |
Filed: |
August 2, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10910696 |
Aug 2, 2004 |
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10015162 |
Dec 11, 2001 |
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10015162 |
Dec 11, 2001 |
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08776737 |
May 5, 1997 |
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08776737 |
May 5, 1997 |
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PCT/GB95/01330 |
Jun 7, 1995 |
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10015162 |
Dec 11, 2001 |
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08473697 |
Jun 7, 1995 |
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5948384 |
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08473697 |
Jun 7, 1995 |
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07988919 |
Apr 5, 1993 |
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Current U.S.
Class: |
424/1.11 |
Current CPC
Class: |
A61K 2121/00 20130101;
A61K 47/42 20130101; A61K 9/0024 20130101; A61L 24/0015 20130101;
A61L 2300/102 20130101; A61L 2300/44 20130101; A61K 51/1213
20130101; A61L 2300/414 20130101; A61K 9/0019 20130101 |
Class at
Publication: |
424/001.11 |
International
Class: |
A61K 051/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 21, 1994 |
GB |
9414684.2 |
Jul 25, 1994 |
GB |
9415405.1 |
Feb 6, 1995 |
GB |
9502246.3 |
Feb 21, 1995 |
GB |
9503357.7 |
Claims
We claim:
1. A composition comprising a precursor of an aqueous-based plastic
polymer and, in particulate form, a radiotherapeutic agent or an
agent convertible to a radiotherapeutic wherein said agent mediates
localised radiotherapeutic activity when immobilized in the plastic
polymer.
2. The composition according to claim 1, wherein said agent is in
the form of a chelate holding a radioactive atom.
3. The composition according to claim 1, wherein the agent is a
ferrite.
4. The composition according to claim 1 wherein the agent is a
.beta.-emitting ferrite.
5. The composition according to claim 1, which additionally
comprises a radiation sensitiser capable of leaching out and
augmenting the local radiotherapeutic effect.
6. The composition according to claim 1, which additionally
comprises a growth factor or other substance that mitigates the
anti-wound healing effect of radiation.
7. The composition according to claim 1, wherein the agent
comprises a zinc-substituted yttrium ferrite, or a
.sup.56Fe-enriched ferrite.
8. The composition according to claim 1, wherein the agent
comprises .sup.103Pd or .sup.90Y.
9. A method for the radiotherapy of a tumor, which comprises
applying to the tumor an effective amount of a composition as
defined in claim 1.
10. The method according to claim 9, wherein the radiotherapy of a
tumor comprises brachytherapy.
11. A method of radiation synovectomy which comprises administering
an effective amount of a composition of claim 1 to a patient to be
treated.
12. A method of radiotherapy in the treatment of arterio-venous
malformations in a blood vessel which comprises applying to the
blood vessel a composition as defined in claim 1.
13. A method for making a composition of claim 1 which comprises:
(i) preparing a particulate radionuclide; and (ii) mixing the
particulate radionuclide with the polymer precursor.
14. A method of using a composition according to claim 1, which
comprises applying the composition directly to tumor tissue.
15. A composition comprising a precursor of an aqueous-based
plastic polymer and, in particulate form, a radiotherapeutic
ferrite or a ferrite convertible to a radiotherapeutic, wherein
said ferrite mediates localised radiotherapeutic activity when
immobilized in the plastic polymer.
16. The composition according to claim 15, wherein the ferrite is a
.beta.-emitting ferrite.
17. A composition comprising a precursor of an aqueous-based
plastic polymer and, in particulate form, a radiotherapeutic agent
or an agent convertible to a radiotherapeutic, wherein the agent
comprises a zinc substituted yttrium ferrite or a
.sup.56Fe-enriched ferrite, wherein said agent mediates localised
radiotherapeutic activity when immobilized in the plastic
polymer.
18. A composition comprising a precursor of an aqueous-based
plastic polymer and, in particulate form, a radiotherapeutic agent
or an agent convertible to a radiotherapeutic, wherein the agent is
a ferrite comprising .sup.103Pd or .sup.90Y, and wherein said agent
mediates localised radiotherapeutic activity when immobilized in
the plastic polymer.
19. A composition comprising an aqueous-based plastic polymer and,
in particulate form, a radiotherapeutic agent or an agent
convertible to a radiotherapeutic wherein said agent mediates
localised radiotherapeutic activity when immobilized in the plastic
polymer.
20. A composition comprising an aqueous-based plastic polymer and,
in particulate form, a radiotherapeutic ferrite or a ferrite
convertible to a radiotherapeutic, wherein said ferrite mediates
localised radiotherapeutic activity when immobilized in the plastic
polymer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part of U.S. application Ser. No
07/988,919, filed May 4, 1993.
FIELD OF THE INVENTION
[0002] This invention is in the field of medical therapeutics and
concerns novel means of delivering therapeutic agents. In
particular, this concerns percutaneous or surgical application of
therapeutic agents which are intended to remain at or near the
location at which they are placed by the treating physician or
surgeon.
BACKGROUND OF THE INVENTION
[0003] There are a number of problems in medicine for which therapy
requires direct physical placement of a treating agent. However,
the means for achieving this end are extremely limited and this end
has seemed to be extraordinarily difficult to achieve.
[0004] It is often possible to deliver a drug to a specific
location, such as by the injection of local anaesthetic near a
nerve which must be numbed. However, most small molecules will
diffuse away from their injection site, or otherwise be removed and
dispersed by the actions of the bloodstream, lymphatics and other
movements of interstitial fluids. In a number of situations, it is
advantageous for the therapeutic agent to remain at the desired
location for a much greater length of time.
[0005] It is sometimes possible to place a bead, capsule or seed
with an agent at a given location, but it is very difficult to
apply such localised therapy over a surface rather than at a single
point. Ideally there should be a rapid and effective means for
coating certain surfaces in the human body with therapeutic
agents.
[0006] One such problem, well known to surgeons who specialise in
the treatment of brain cancer (e.g. gliomas), arises because tumour
cells infiltrate into the otherwise normal brain surrounding a
gross tumour. The gross bulk of tumour is removed surgically by
craniotomy, however the margins of apparently normal brain always
contain sufficient numbers of tumour cells as to make local
recurrence of the tumour a virtual certainty. These tumours do not
metastasise, so local recurrence is generally the only type of
recurrence to be expected.
[0007] To treat the small number of remaining cancer cells,
chemotherapy can be given. However, even very toxic agents which
cause severe toxic side-effects throughout the body have only a
very slight slowing effect on tumour cell growth of gliomas.
Radiation therapy may be given but, in young children, the
radiation causes grievous harm to the surrounding brain and, in
adults as well, there is risk of severe scarring from the radiation
which can cause swelling and mass effects in large regions of the
brain. Although radiation clearly slows the growth of the tumour,
it is virtually impossible to deliver enough radiation to slow the
tumour substantially without causing unacceptable damage to the
brain. Results for treatment of brain cancer remain dismal, and
life expectancy after diagnosis is measured in months with or
without surgery.
[0008] One significant recent advance comes from improved methods
of applying `brachytherapy`. In some brachytherapy approaches,
multiple hollow latex catheters with radioactive material in their
tips are inserted into the brain, generally with computer and
image-guided stereotactic methodology or by use of any one of a
number of computer and image-guided spatial position wands. These
catheters cause a risk of infection spreading along the catheter
and do not provide a uniform field of radiation and are not well
suited for treating the surface of the tumour resection bed in the
brain.
[0009] In one improvement which is currently the best state of the
art, the radioactive material, commonly an isotope of iodine, is
enclosed in small stainless steel or titanium `seeds` which are 0.8
mm.times.4.5 mm in size. Immediately after the surgeon resects the
tumour, and before any surgical closure is commenced, the surgeon
uses a tissue adhesive such as a cyanoacrylate-based glue to attach
the seeds to the brain surface along the plane of tumour resection.
A tumour which was 4 cm in diameter has a surface area of e.g.
30-40 cm.sup.2 of resection bed and may require some eighty or
ninety individual seeds to be glued in place, one by one, in a grid
pattern with as regular a spacing as possible. Each seed has a
radioactive source which treats a surrounding sphere with low
level, low penetration energy for use over a long period of time
until the radiation decays away over, e.g. 3-4 months. The seeds
are left in place.
[0010] The problem with this current method is that the painstaking
process of gluing on the seeds requires as much as an hour during
which time the full operating room team (surgeon, assistant
surgeon, radiation therapy treatment planner, radiation therapy
technician, anaesthesiologist, scrub nurse, circulating nurse) are
all required to be present and are all subject to unshielded
radiation exposure.
[0011] An alternative type of glue for surgical use is termed a
`tissue glue`. This is a natural biological material that takes
advantage of natural components of the human clotting system. The
clotting proteins and cofactors are either extracted from donor
blood, or extracted from the patient's own blood prior to surgery,
or, in many cases now, extracted from the patient's own blood
during the surgery itself. Typically, the glue is maintained in two
components, one with fibrin protein solution and the other with
e.g. the calcium solution which helps activate the clotting
cascade. The two components are loaded into two separate syringes
and the needle tips from the two syringes are bent to run parallel
to each other so that the two tips are closely apposed. The surgeon
uses a double syringe apparatus to apply the two fluids to the
surface of interest simultaneously. As the two fluids emerge from
the needle tips onto the tissue surface they mix and congeal. This
material is used for plugging leaks in the dura membranes around
the brain in order to prevent leakage of spinal fluid as well as
for a wide variety of other surgical applications including the
assistance of wound closure and haemostasis. Tissue glues have also
been proposed as means of achieving slow controlled release of
various growth factors and antibiotics.
[0012] It is not possible to suspend the seeds in either a liquid
cyanoacrylate glue or in either component of a tissue glue as
described above, because they would sink out of solution. It would
be possible to include a variety of radioactive metal cations in
chelate molecules and then dissolve these molecules in a tissue
glue component; however, even for very large proteins, the tissue
glue allows migration of the molecules through its interstices.
Thus from the point of view of most molecules, the glue is not a
glue at all, but only a matrix through which they can diffuse along
with the tissue water in which they are dissolved.
SUMMARY OF THE INVENTION
[0013] In a broad aspect of the invention, a ferrite or other
radiotherapeutic agent, in particulate form, is suspended in a
tissue glue, suitably in the pre-mix. If a colloidal solution of,
say, .beta.-emitting ferrite is prepared in a tissue glue, this can
be applied after surgical resection of a tumour, particularly near
an eloquent area of the brain, where a thin shell of tumour may
remain, minimising exposure to the surgeon and operating staff. The
particles are biodegradable, and so will be resorbed over weeks. A
cell adhesion moiety-coupled radionuclide may be used, if the agent
is not physically held in the matrix.
[0014] Further aspects of the invention are indicated below and are
also defined by the claims. Apparatus of the invention is
illustrated in the drawings, and comprises any combination of the
means illustrated for achieving the given purpose.
DESCRIPTION OF THE INVENTION
[0015] The radiotherapeutic agent may be any of a variety of
nuclides, depending on the energy, penetration or half-life that is
desired. Appropriate choice of such criteria is within the skill of
those knowledgeable in the art. It is preferably a ferrite, e.g. a
.beta.-emitting ferrite, and preferably comprises a chelate.
[0016] Suitable tissue glues are also known. This component may be,
for example, based on a clottable protein such as fibrinogen. For
example, a glue such as Tisseel (available from Immuno Danmark A/S
of Copenhagen) may be used. Tissue glues, including fibrin and
cyanoacrylates, are also described by, for example, Kottai et al,
Ann. Otol. Rhinol. Laryngol. (1983 January-February) 92(1 Pt
1):29-32; Ronis et al, Laryngoscope (1984 February) 94(2 Pt
1):210-3; Barnstable, Nature (1986 Jun. 19-25) 321 (6072):731-2;
Toriumi et al, Otolaryngol. Clin. North Am. (1994 February)
27(1):203-9; and Schlag et al, in Fibrin Sealant in Operative
Medicine Vo. 1, G. Schlag. 11. Redl (eds), Springer-Verlag
Berlin-Heidelberg (1986) 27-38.
[0017] The term "tissue glue" is used herein in its broad sense,
i.e. as any tissue-compatible matrix within which the active
component is retained, suitable for topical or other application to
the locus of treatment. It may therefore be a gel-like substance
comprising pores within which the agent is held. It will often be
proteinaceous, and usually it will be biodegradable.
[0018] According to one aspect of this invention, it has been
appreciated that larger particles can readily be immobilised in a
variety of gels such as the tissue glue. Further, these particles
are made in such a way that they can be fully and stably dissolved
in water or in e.g. the calcium fluid component of the tissue glue,
yet these particles are small enough to be sterilised by filtration
methods along with the solution in which they are dissolved. The
particles can be manufactured in such a way as to incorporate a
wide variety of different metal cations, including their
radioactive isotopes (to include emitters of .beta.-particles,
.alpha.-particles, .gamma.-rays, or X-rays from K-capture decay) in
the ferrite crystal matrix at their core. The nuclides are very
stably incorporated into the ceramic type core of 10-200 nanometers
in diameter and the core is coated in any one of a variety of
macromolecules such as dextran.
[0019] These particles can be made radioactive in several different
ways. It is only necessary to dissolve radioactive isotopes of
certain metals as soluble metal chlorides in the initial metal
chloride solution prior to the ferrite precipitation step disclosed
in WO-A-9305815 and U.S. application Ser. No. 08/211,041, filed
Mar. 16, 1994, the content of which is incorporated by
reference.
[0020] The isotope palladium-103 (t.sup.1/2=17 days, EC) is
extremely useful for brachytherapy with permanent implants because
of its useful half-life which allows treatment of a cancer as
various cells in the tumour pass into the radiosensitive cell
division process over the course of days and weeks. The X-rays
produced by its electron capture decay have low energy (half-value
thickness in water of 1.6 centimetres) and hence it is possible to
have exceedingly precise control over the area treated, as for
example in the post-excision area where invisibly small amounts of
tumour may have invaded surrounding normal tissue to a depth of a
few millimetres. It is also the case, as is disclosed in
WO-A-9211846 and U.S. application Ser. No. 08/087,781, filed Jul.
7, 1993 (the content of which is incorporated by reference) that
palladium is very readily incorporated into spinel ferrites in
stable fashion.
[0021] Two readily available methods exist for the production of
.sup.103Pd. The first is by the use of low energy neutrons from a
production reactor to irradiate the .sup.102Pd stable isotope. It
should be noted that this method has the disadvantage that
.sup.102Pd is only one of five different stable isotopes of
palladium (see Table 1) and makes up only 1% of naturally-occurring
palladium. For reasons discussed below, it is necessary to extract
the 102 isotope prior to irradiation because of the undesirable
qualities of the other resulting radioisotopes if the full mixture
of stable palladium isotopes is irradiated (see Table 2). The
second method for production of .sup.103Pd is to use a high energy
cyclotron capable of causing reactions with protons (conventional
cyclotrons use deuterons and alpha particles which have greater
mass/charge). Such an instrument can be used to irradiate rhodium
which occurs naturally as only a single isotope, .sup.103Rh, so
that all conversions are to .sup.103Pd which is then separated
chemically from the rhodium in carrier free form.
[0022] Another medically useful nuclide for delivery with ferrite
or other particles is yttrium-90 (t.sup.1/2=64 hours, .beta.-,
2.283 MeV). This is readily produced from low energy neutron
irradiation of .sup.89Y since 100% of natural yttrium occurs in
this form. The pure beta emission and half-life are suitable for
such tasks as radiation synovectomy and treatment of other very
thin layers of disordered tissue. The provision of .sup.90Y in an
appropriate liquid carrier has been a problem for many years since,
for intra-articular use, small molecule carriers and colloids tend
to leak out of the joint, while large particles do not distribute
properly because they do not remain in solution. It has been
suggested previously in WO-A-9211846 (see above) that various
lanthanides can be incorporated into garnet ferrite-type crystals.
For the inclusion of yttrium, a second period Group IIIB element,
it has been appreciated that the stability and efficiency of
incorporation can be improved by forcing the yttrium into a
modified spinel crystal.
[0023] The prototype mineral spinel (MgAl.sub.2O.sub.4) is based on
a close-packed, face-centred, cubic crystal of oxygen atoms with
metal ions placed at interstitial spaces in the crystal. There are
A spaces which accommodate ions of 0.3 to 0.6 angstroms (8
sites/subunit) and B spaces which accommodate ions of 0.6 to 1.0
angstroms (16 sites/subunit). In natural spinel, the divalent
magnesium ions are in the A spaces and the trivalent aluminum ions
are in the B spaces. Magnetite is an `inverse spinel` because the
crystal subunit of 32 O.sup.2- anions has trivalent Fe.sup.3+ in
the 8 A-sites, with 8 B-sites occupied by divalent Fe.sup.2+ and 8
B-sites occupied by trivalent Fe.sup.3+.
[0024] When Zn.sup.2+ cations are substituted for Fe.sup.2+ cations
in the initial mixture, they tend to enter the A-sites because they
are slightly smaller than the Fe.sup.2+ cations. This forces the
crystal into a `spinel` configuration. However, as the
concentration of Zn.sup.2+ approaches 50% of the divalent cation,
the crystal has steric problems because the Zn.sup.2+ cations are
still actually a bit too large for these A-sites. Above 50%
Zn.sup.2+, the crystal produced is again an inverse spinel and
these effects are well studied because of their impact upon the
magnetisation of bulk ferrites. An entirely unanticipated aspect of
this system has been discovered, i.e. that under these conditions
of flux in the crystal structure near a 50/50 mix of Zn.sup.2+ and
Fe.sup.2+, the large Y.sup.3+ cations are more readily accommodated
in the crystal and a more stable mixed ferrite results. This may
also reflect retention of partial inverse spinel structure with
smaller Zn.sup.2+ cations in enough of the B-sites to allow for
additional space to accommodate Y.sup.3+ in the B-matrix as
well.
[0025] An alternative manoeuvre is to use Li.sup.1+ cations to
balance the stoichiometry when replacing Fe.sup.2+ cations with
Y.sup.3+ cations. The Li and Y are added in equal amounts as the
Fe.sup.2+ is reduced. However, the
Fe.sup.3+/Y.sup.3+:Fe.sup.2+/Zn.sup.2+ system produces a stable
yttrium-carrying ferrite with medically useful qualities.
[0026] The incorporation of yttrium in particles for radiation
synovectomy also makes possible a solution to one of the principal
problems now limiting the use of this procedure. A needle is used
to inject the material into the joint, but when the needle is
withdrawn some of the radioactive material becomes subject to
leakage out of the joint. To minimize this problem, patients are
now required to remain motionless in bed in hospital for several
days.
[0027] The incorporation of the radioactive yttrium into ferrites
makes possible several methods of limiting the leakage and
subsequent spread of radioactivity. Firstly, the knee can be
wrapped in a magnetic coil which will prevent any leaked
radioactive ferrites from spreading out of the area. More simply,
however, tissue glues can be used to help seal the joint capsule.
Because the radioactivity is incorporated in a substance which does
not diffuse through tissue glue, the application of tissue glue to
the injection site will prevent leakage. The half-life of the
.sup.90Y is sufficiently short that most of the radioactivity will
have decayed before the tissue glue will have broken down. In this
aspect, the invention provides a system which inhibits unwanted
spread of synovectomy agent.
[0028] In a further modification, the .sup.90Y-ferrites may be
fully incorporated into the tissue glue at the time of injection
into the joint via a double-barrelled, double-needle syringe. The,
say, fibrin glue is allowed to set within the involved joint, but
its injection is accompanied by agents which help promote
fibrinolysis, such as tissue plasminogen activator, or it is
applied in a specially modified tissue glue preparation which is
compounded to hold a lower concentration of fibrinogen then is
usually used. In this fashion it can be assured that the
ferrite-containing gel will dissolve over 2-4 days during which
time much of the activity of the .sup.90Y will be retained. During
the breakdown process, macrophages are known to be actively
attracted into the matrix and will ingest radioactive particles as
well. This will thus serve as a means of both reducing leakage from
the joint and effectively loading macrophages with radioactive
ferrites so that when they subsequently distribute to the synovium
they will be highly active.
[0029] Most effectively, the technique will involve a three-stage
injection into the knee from a four-barrelled syringe. One barrel
contains low fibrinogen glue component mixed with radioactive
ferrites, another barrel contains the calcium solution, a third
barrel contains ferrite-free fibrinogen solution, and a fourth
contains radioactive ferrites in a suitable buffered aqueous medium
with an X-ray contrast agent such as iohexal. After introduction of
the double needle into the joint, the injection is commenced with
radioactive ferrites in aqueous medium. Next the needle is partly
withdrawn (under fluoroscopic guidance) to near the exit from the
joint capsule, and here an injection is done to mix radioactive low
fibrin glue component with the calcium solution. Finally, the
needle is withdrawn to just outside the joint and non-radioactive
tissue glue is then administered to fully seal the joint
capsule.
[0030] It has further now been appreciated that alternative means
of incorporating radioactivity in the ferrites will sometimes be
useful. One such alternative method is to include in the crystal
matrix an element or isotope which is the `parent` of the desired
isotope. The entire formed particle, in aqueous solution, is then
bombarded with neutrons in a reactor or with protons, deuterons, or
alpha particles from a cyclotron beam or nucleons from a linear
accelerator in order to render the parent nuclide into the desired
daughter isotope. This method has the disadvantage of causing some
of the carrier iron atoms and the carbon, hydrogen, and oxygen
atoms in a dextran coat to be converted to possibly undesirable
isotopes as well. However, the dextran atoms are present in far
lower concentration than the atoms in the particle, so the
situation of the ferrite alone can reasonably considered as the
greatly predominating source of post-irradiation nuclides.
[0031] There are however a variety of nuclear reactions involving
iron isotopes which would typically be considered as non-productive
or useless in that the resulting nuclides are themselves a mixture
of stable isotopes of no medical use. It has now been appreciated,
however, that in the setting of this type of ferrite carrier, the
objective is properly to change carrier atoms only into different
stable carrier atoms, while the therapeutic or diagnostic daughter
nuclide included in the matrix results from a selectively
introduced parent isotope incorporated chemically prior to the
irradiation.
[0032] Such primarily stable shifting takes place in the course of
low energy neutron bombardment in a reactor. Naturally-occurring
stable iron is 92% .sup.56Fe, 6% .sup.54Fe, 2% .sup.57Fe and 0.3%
58 Fe. After low energy neutron bombardment, the majority of atoms
(.sup.56Fe) will be changed to .sup.57Fe which is just a different
stable isotope and the existing .sup.57Fe converts to stable
.sup.58Fe. In this case however, the .sup.54Fe becomes .sup.55Fe
with 2.7 yr half-life and EC capture decay, and the small amount of
natural .sup.58Fe becomes .sup.59Fe with 45 day half-life and
.beta. and gamma decay. As shown in the attached Table 3, the
oxygen in the crystal as well as the carbon and oxygen in the
dextran are converted substantially to stable isotopes by this
reaction (n,.gamma.). If such particles are held in storage for
e.g. 10 half-lives of the .sup.59Fe, the very small starting amount
will be reduced to a negligible contribution, and the resulting
particles will remain as a long half-life EC capture emitter. Such
a material could be useful in the fabrication of temporary implants
for brachytherapy where the implant is cast in the form of seeds,
catheters, or reusable, pumpable liquid for catheter-based,
temporary brachytherapy.
[0033] To use low energy neutron bombardment (n,.gamma.) for
non-productive change, it would be necessary to prepare the
ferrites from .sup.56Fe-enriched iron to minimize undesired
radioactive products. However, any .sup.102Pd included in such a
.sup.56Fe-enriched ferrite would be converted to useful .sup.103Pd
(t.sup.1/2=17 days, EC). As shown in Table 2, it is important that
virtually no .sup.106Pd be included in the starting particle for
this treatment since it would be converted into a very long
half-life, low energy beta-emitter (.sup.107Pd, 6.5.times.10.sup.6
y, .beta.-, 0.033 MeV, decaying to stable .sup.107Ag). However, for
the preparation of permanent implants, this would be a desirable
effect, and natural, mixed isotope palladium could be used as a
starting material. The small amount of .sup.103Pd produced would
decay to negligible amounts after ten half-lives (170 days), after
which the material could be treated as an effectively permanent
source of low energy beta particles. In yet another aspect, because
of the extremely low energy of these beta particles, the use of a
plastic or silastic capsule or a titanium capsule around a seed
cast to include such ferrites, or a thin, e.g. 1 mm, layer of
ferrite-free tissue glue would provide nearly complete shielding of
the beta emissions. In this way, the natural palladium ferrite
could still be used as a permanent implant emitting effectively
only the desirable X-rays from electron capture decay of
.sup.103Pd. The .sup.109Pd (13h,.beta.-,1 MeV) produced from
natural .sup.108Pd would still make it necessary to hold the
particles for at least ten of these half-lives (130 hours) to
reduce this beta output if it was desired to use only EC X-rays.
However, in many therapeutic situations, inclusion of a 1 MeV beta
particle would be useful along with the EC X-rays.
[0034] Fast neutron bombardment of .sup.56Fe-enriched ferrites is
another feasible means of producing useful medical isotopes via the
(n,p) reaction. The various nuclides produced form the
dextran-coated ferrite carrier are all very short-lived (see Table
3).
[0035] Use of a high energy cyclotron to bombard .sup.56Fe-enriched
ferrites with protons results in .sup.56Co which is a relatively
long half-life (77 days) positron-emitter. In both these cases, the
advantage is in the ability to incorporate the radioactivity after
the chemical preparation, clean up, and concentration steps have
been completed. This avoids exposure to those involved in preparing
the material and is particularly helpful in preparing
positron-emitting ferrites since it is extremely difficult and
awkward to shield production workers from positron annihilation
photons due to their high energy.
[0036] In yet another aspect, the bombardment of .sup.56Fe-enriched
dextran-coated ferrites with alpha particles would produce
.sup.58Ni (.alpha.,2n) which is stable but would have the
advantageous effect of converting oxygen atoms in the ferrite
crystal as well as in the dextran into the short half-life (110
min) positron-emitter .sup.18F (.alpha.,pn) which has a wide
variety of medical uses; however, the side-reaction of (.alpha.,pn)
production of .sup.58Co (70d,.beta.+) limits the value of this
production method. Treatment of dissolved dextran by alpha
bombardment prior to the precipitation reaction would cause the
inclusion of .sup.18F in both the dextran coat and in the interior
of the crystal.
[0037] A completely different way of adding radioactivity after
manufacture of the ferrites or of any other useful particle of the
desired size range is to conjugate chelating groups such as EDTA,
NTA or DTPA to the dextran coat of the ferrite or surface group of
any other particle. In this fashion, all preparation steps are done
with non-radioactive materials. Finally, when the material is to be
shipped for use, or even at the site of use, the chelate-conjugated
particles are exposed to dissolved radioactive metals or other
chelatable elements. The elements need only have higher binding
affinity to the chelate than e.g. sodium used to fill the chelate
prior to radioactive uptake.
[0038] After exposure of an excess of the particles to the
radioactive material, it is optionally possible to use centrifugal
ultrafilters or simply passage through Sephadex columns to separate
the hot particle fraction from any unbound radioactive
elements.
[0039] It should also be noted that the considerations discussed
above concerning palladium isotopes also apply in this alternative
situation in which a reactor is used to irradiate natural mixed
palladium before preparation of the ferrites in which such
resulting palladium is dissolved and used to load chelator
molecules conjugated to the dextran or other coat of the ferrite
and additionally these considerations apply where the
post-irradiation palladium is used to make radioactive Fe--Pd
ferrites by precipitation from dissolved irradiated palladium
chloride.
[0040] It should additionally be noted that these considerations
are not restricted to the element palladium but can readily be
worked out as they apply to a wide variety of medically useful
nuclides when prepared for delivery in a ferrite-based
particle.
[0041] Choice of the coating type and e.g. the size of dextran
molecule to be used controls the final diameter of the particle. A
5,000 MW dextran coating will yield a particle more likely to
migrate in a loose gel which would be preferable for drug delivery,
while a 100,000 MW dextran coat would tend to produce a particle
which resides very stably in the matrix for e.g. radiotherapeutic
applications. Final particles can be converted to larger
conglomerates by use of various conjugation reactions to create
linkages between dextran molecules of multiple particles.
[0042] WO-A-9305815 and U.S. application Ser. No. 08/211,041
disclose that the particle preparation can be cleansed of any
unincorporated or easily soluble cations through treatment with a
chelation buffer. The buffer may comprise EDTA
(ethylenediaminetetraacetic acid), DTPA
(diethylenetriaminepentaacetic acid), NTA (nitrilotriacetic acid)
or various other metal cation chelating agent either with or
without e.g. meglumine as a counter-ion. These chelation buffers
act at least in part to dissolve metal hydroxide polymers without
dissolving the magnetite or other mixed metal crystal. The
dissolved, chelated ions which were not properly incorporated in
the particles at the time of the initial precipitation reaction are
then easily separated from the particles. Originally, it had been
appreciated that this manoeuvre greatly improved the simplicity of
manufacture of such ferrites.
[0043] It has now been appreciated that it is important to be able
to remove any radioactive nuclides which are not stably
incorporated in the particles when a brachytherapy product for
therapeutic use is to be made from the resulting preparation.
Application of tissue glue-borne nuclides relies on a very high
proportion of all the radioactive nuclide migrating stably with the
particle fraction during synthesis, since only the particle-bound
fraction will be held stably by the matrix in vivo. The chelation
buffer step was originally described in WO-A-9305815 and U.S.
application Ser. No. 08/211,041, as a means of improving the
behaviour of particle solutions during filter purifications. It has
now been found that this method results in a unique solution which
provides an entirely novel mechanism for stably holding a variety
of radionuclides stably in a matrix.
[0044] It should be appreciated that this innovation has uses not
limited to tissue glues but also provides a convenient means for
incorporating radionuclides into a wide variety of carriers of
various types and useful for various purposes. These uses all have
in common the need to hold a nuclide in place so that it is not
allowed to move or diffuse or dissolve freely through the medium or
carrier into which it has been introduced.
[0045] Any particle can contain a range of nuclide concentrations
ranging from one atom per crystal, up to e.g. 100,000 or more atoms
per crystal. This choice allows both for storage of the particles
over the long term and for a wider choice of possible isotopes to
be used depending upon the therapeutic task to hand. Groups of
particles can also be conjugated together with periodation
reactions or glutaraldehyde reactions in order to make them larger
in the aggregate so that they achieve greater stability in looser
gel matrices.
[0046] It should also be appreciated that this means of particle
application is not restricted to tissue glue alone, but also
applies to various other collagen matrices or other matrix or
gel-forming substances tolerable for biological use or foams or
gelfoam substances as well as with a wide variety of other adhesive
materials which can be used to hold particles and keep them at a
chosen proximity to a particular target.
[0047] When fibrin-based tissue glue is used as the matrix for
immobilizing the particles of whatever type, the function of the
invention will be greatly affected by the stability or rate of
breakdown of the tissue glue matrix. Fibrin tissue glue is subject
to breakdown from the action of natural fibrinolytic proteins. The
amounts and concentrations of these fibrinolytic proteins vary from
tissue to tissue within the body. On average, a tissue glue layer
in the human body would be expected to lose the greater part of its
physical integrity within a period of about 10 days from
application. In many cases this is desirable, however in other
cases it may be desirable to either extend or shorten the period of
stability of such a gel. In the case of fibrin glues, there is a
variety of proteins and other agents well known to affect the
natural metabolism of fibrin clots. These agents have been used for
a variety of purposes but have not been considered as a means of
manipulating the drug delivery properties of gels or as a means of
controlling radiotherapy or gene therapy.
[0048] One such agent is amicar (.epsilon.-aminocaproic acid). A
typical use is to slow the breakdown of clots which form on
ruptured cerebral aneurisms and so to inhibit their risk of repeat
haemorrhage. If amicar or similarly acting agents such as
aproteinin or various proteinase inhibitors are incorporated in the
gel matrix, either simply by mixing them into the initial solution
or by adhering or conjugating them to particulates intended to be
included in the matrix, then these will slow the breakdown of the
gel. Alternatively, the inclusion of agents such as tissue
plasminogen activator or streptokinase will speed the breakdown of
the gel.
[0049] Prolongation or shortening the stability period of gels has
not previously been considered in relation to the use of tissue
glues for drug delivery. This is because all previous descriptions
of the use of tissue glue for drug delivery have involved drugs
which diffuse out of the gel matrix fairly rapidly so that the
length of time of survival of the gel has little impact on the rate
of delivery. However, in the current invention, many of the aspects
of the drug delivery mechanism are closely dependent upon the rate
of tissue glue breakdown.
[0050] In one aspect, a locally active protein which would benefit
from slow release, such as bone matrix protein, is conjugated to a
particulate such as the dextran-coated ferrite. Many such proteins
will retain their physiologic activity even though they are
conjugated to a particle. The clinical problem is to provide slow
release of the protein from the gel. By immobilizing the
protein/particle conjugate in the gel, the physiologic activity is
delayed until the matrix is physically degraded. Here the particle
acts as an anchor and the breakdown of the gel releases the
anchor.
[0051] In another aspect where tissue glue is used to hold a
.sup.103Pd ferrite for brachytherapy, the half-life of the nuclide
requires a relatively long period of stability of the gel in order
to minimize spread from the site of application prior to the
passage of three to five half-lives. In tissues such as prostate
with high concentrations of fibrinolytic proteins this a particular
concern. Although a variety of longer-lasting synthetic and
semi-synthetic gels can be used, the addition of an
anti-fibrinolytic allows the use of fibrin tissue glue.
[0052] Yet another application is in the treatment of
arterio-venous malformations in the brain. Currently these are
treated non-surgically either by using intravascular catheters to
fill the vessels with an occluding matrix or by external beam
therapy. In this invention, a tissue glue may be injected with
radioactive ferrites (.sup.103Pd or .sup.90Y). This would allow for
simultaneous embolization and radiation sclerosis of the AVM
vascular walls. Prolonging the life of the tissue glue would help
assure focal delivery as well as prolonging the life of the embolic
vessel blockage. If the interventional radiologist found that too
much vessel had been blocked, then fibrinolytics could be applied
to rapidly dissolve the gel and allow the radiation to diffuse
through the body where it would be present in extremely low
concentration because of the large volume of distribution relative
to the amount of radioactive agent involved. The ferrites could
also be collected from the blood stream by a magnetic filter.
[0053] In order to localise therapeutic agents, various means
involve tissue glue. One is based on physically conjugating a
variety of carrier proteins directly onto the fibrin in the tissue
glue. The conjugation can be carried out through antibodies to the
fibrin or through the use of periodate conjugation. The carrier
proteins and dextran molecules incorporate chelate molecules in a
variety of arrangements all well known to those expert in the art
of therapeutic metal ion delivery. Additionally, this includes
non-metal therapeutic radionuclides attached in other ways. By way
of example, the radioactive iodine may be conjugated directly to
the fibrin by standard iodination reactions. In this fashion, the
radioactive iodine or other radioactive element can be rapidly
attached to the patient's own proteins for use in autologous tissue
glue.
[0054] It is also now appreciated that in addition to radiotherapy
applications, these particles applied by tissue glue may be used to
deliver a variety of other locally useful therapeutic agents. It is
possible to adhere nucleic acids onto these particles as disclosed
in WO-A-9305815 and U.S. application Ser. No. 08/211,041. It is now
also appreciated that in addition to genes, it is possible to
adhere anti-sense oligonucleotides.
[0055] It is now known that gliomas involve a defect in a gene
termed the p53 gene and that this defect can be corrected by gene
therapy, however there is no known way to deliver the therapeutic
genes to the glioma cells (abnormal astrocytes). It is now
disclosed that therapeutic genes for the treatment of brain tumours
may be adhered to the surface of the particles and the complex then
included in a liquid component of the tissue glue. The glue is then
applied at the time of surgery to the excision surface.
[0056] Astrocytes are phagocytic cells and have been demonstrated
to avidly take up these particles into their interior, while
neurons are far less phagocytic. By using smaller particles and a
looser matrix, the particles may be allowed to migrate slowly out
of the matrix into the nearby or surrounding brain and to there be
ingested by the actively phagocytic astrocytes. This may be further
promoted by the use of targeting proteins or antibodies which
adhere to the surface of astrocytes generally or which may be
targeted to markers expressed in excess amounts by cancerous
astrocytes. These targeting proteins may be adhered to the particle
surface by chemical conjugation by the periodate method, or by a
variety of other adhesion or conjugation methods well known to
those skilled in the art.
[0057] It is further appreciated that nucleic acids may simply be
incorporated into these glues by mixture without using these
particles as carriers. Where particles are used as carriers, a
variety of types of particles is suitable, including
cyanoacrylates, liposomes, albumin or other protein-based
materials, starburst dextran dendrimers, starches, pectins,
polylysine or other polymers.
[0058] Further, it has now been appreciated that viruses of sizes
similar to the particles can also be immobilised in tissue glues.
Thus, the therapeutic genes delivered by the glue can be carried in
retroviral vectors such as those described in WO-A-9317118 and U.S.
application Ser. No. 08/295,737, and also PCT/GB95/00663. The
admixture of retroviral and other viral vectors into one component
of a tissue glue or settable matrix has a wide variety of
applications where selected local gene therapy is desired. The
viruses gain access to cells either by slow release from a loose
matrix or by release associated with biodegradation of the gel
matrix.
[0059] Alternatively, a loose gel may be used to immobilise cells
infected with retroviral or other viral vectors or `producer` cell
lines containing all the genetic material needed to produce viral
particles and a vector molecule for encapsidation therein. The
cells are held in place by the matrix, but the viral particles pass
through the loose gel for the purpose of transfection or gene
therapy. These immobilised cells can be used for local delivery of
viral vectors or for delivery of vectors into the bloodstream for
action at a distant site. Genetically-modified cells trapped in a
tissue glue can also be used as sources of therapeutic proteins
which will then diffuse out of the gel after production in the
modified implanted cells as with various growth factors, hormones,
neurotransmitter modulating enzymes, antibodies, or cytokines.
[0060] In addition to the use of these particles for radiotherapy
and for the delivery of genes, they may be used as transducers for
the application of hyperthermy treatments. After placement of a
ferrite particle containing gel, the patient may be exposed to
oscillating electromagnetic fields tuned to the particle type of
particle used. Thus the particles can be caused to become hot and
so provide a controllable heat therapy either separate from or in
conjunction with their radiotherapeutic effect.
[0061] In addition to the potential for carriage of macromolecules,
emission of radiation and transduction for heating, these particles
can also be used as a means of delivering cation therapy, as
disclosed in WO-A-9211846 and U.S. application Ser. No. 08/087,781
(see also above). In this system, various non-physiological cations
are incorporated into the crystal matrix of the ferrite core. The
particles are then delivered in a tissue glue. Subsequently, as the
glue breaks down or as the particles slowly leach out and are
ingested by various cells, the cations are released through
intracellular metabolism of the iron oxide core. Delivery of
cations can be used for the treatment of viral illness and also for
cancer chemotherapy.
[0062] This antibiotic effect may also be exploited in a variety of
hard coatings into which these particles may be incorporated. Where
various cations offer anti-bacterial effects, these may used in
coatings on e.g. various implants.
[0063] Additionally, the radiotherapeutic tissue glue can be
augmented by the inclusion of synergistically acting diffusible
drugs, either loosely incorporated in the gel for free diffusion or
introduced in semi-soluble or insoluble form in order to achieve
slow release, or weakly adhered to the dextran or other polymer
coating of particles. Such particles serve to temporarily
immobilize and control the distribution of such drugs. Radiotherapy
can interfere with wound healing in some situations. It will
therefore often be advantageous to counter the anti-wound healing
effects of radiation by the inclusion of various growth factors in
the gel as disclosed in WO-A-9420133 and WO-A-9209301. Further, it
may be possible to assist the anti-cancer effect of the radiation
by inclusion of a variety of chemotherapeutic radio-sensitizer
drugs or actual chemotherapeutic agents in the gel along with the
radioactive source.
[0064] In addition to the various gels and glue carriers mentioned
above, it should be appreciated that the radiotherapeutic
particles, particularly the EDTA-insoluble particles, can be
dissolved in aqueous-based plastic polymers which can then be
caused to polymerize in the same fashion as described above for the
tissue glues. The additional feature of a plastic is that it would
allow for casting of a sealable shaped radiation carrier prior to
surgery or during surgery.
[0065] Yet another means of administration of the radiotherapeutic
particles is in liquid form in association with specialised
catheter systems which may or may not be further associated with
endoscopic equipment. This could be for a temporary application of
radiotherapy. For example, in the case of the need to treat a
localised lesion in a bronchus of the lung, the therapist would
endoscopically introduce a very thin catheter with a much larger
diameter balloon tip. At the time of introduction the catheter
would be completely collapsed by withdrawal of air and subsequent
turning of an external sealing valve. Once the tip was positioned
correctly, the radiotherapeutic liquid would be pumped into the
catheter. Where the catheter is very thin, there will be only a
very low dose of radiation to surrounding normal tissue, however, a
large amount of the agent would accumulate in the balloon tip and
administer large amounts of radiation at that site (see FIG. 1).
The volume of the catheter system and of the balloon tip can be
precisely known so that only enough radiotherapeutic agent to fill
the balloon tip is pumped in. Then an immiscible liquid (e.g.
paraffin oil) is pumped into the catheter as a chaser so that all
of the radioactivity will be in the balloon tip and only cold
chaser oil will be in the thin feeder catheter where it traverses
normal tissues. The catheter is fashioned of a plastics or other
non-wettable material on which water beads readily and hence the
oil is efficacious at substantially sweeping all the radioactive
aqueous material distally towards the balloon.
[0066] In some situations, it will be desirable simply to introduce
the liquid form of the brachytherapy agent (e.g. with
palladium-103) into the tissue around the site of tumor excision.
These particles are preferentially cleared into and concentrated in
lymph nodes. Similarly, an early stage in the spread of cancer away
from its initial site is along the lymphatics where it is initially
trapped in lymph nodes. The brachytherapy agent may be selectively
concentrated in local lymph nodes and provides an additional
selectively beneficial effect in preventing and treating any early
spread of tumour cells. This is particularly important immediately
after a surgical resection at which time numerous individual tumour
cells are spilled by the surgeon in the process of physically
mobilising and removing bulk tumour. These free floating tumour
cells in the excision site are often cleared to lymph nodes where
they can proliferate and to cause recurrence.
[0067] A solution of the particles may be aerosolized for spray
application to a surface in the body in a system in which the spray
forms part of a tissue glue which sets upon contact. Similarly, an
aerosol route can be used with the liquid agent without glue for
diffuse application in the bronchi or via the GI tract. An aerosol
spray of the particle-carrying liquid can also be used to apply a
thin layer of the particles in an even fashion to a sheet of
implantable material. That sheet may then be sealed with a thin
additional plastic layer. The inclusion of the elements in the
nanoparticles will assure that radioactive elements will not
diffuse through the pores of the plastic.
[0068] For applications such as cation therapy where containment is
less of a concern, the tissue glue may be applied by spray-on
application. An antibiotic fluid may be incorporated in the vehicle
against any airborne contamination. In the spray-on methods, the
fluid vehicle will either be so prepared as to polymerize in air,
or two separate sprays may be used, first a carrier for the fibrin
portion followed by the calcium and particle component. These
applications may be from a pressurised can or from a simple
standard nebulizer.
[0069] In order to apply the therapeutic tissue glue in
applications where a layer must be applied to a surface, several
specialized devices for this purpose may be used and are herein
disclosed. Instead of two needles ending in a point, the exits from
the two application syringes are so fashioned that at their termini
they widen into a flat applicator. The two channels are laid one
over the other and attached to each other so that both deliver a
sheet rather than a stream of glue components (see FIG. 2) and
these two sheets mix on exit, resulting in a sheet of controlled
depth on the tissue surface. Each applicator kit can be supplied
with several of these applicators so they may be readily replaced
if they become clogged through premature mixing of the two
components. These sets of applicators may be provided in a series
of widths including, e.g. 5, 10 or 20 mm, which may be selected
based on the size and shape of the surface to be coated.
[0070] Further, in order to control the depth of the layer of the
material, the applicator may be provided with paired wheels. The
wheels may either have latex rims or small feet so they do not
produce furrows in the layer of the glue. The applicator may also
be automated or semi-automated so that as the surgeon rolls the
applicator along the surface the device measures the rate of
progression from the wheel turning and then automatically drives
the two syringes to apply the layer of glue. Alternatively, as the
surgeon presses the syringe, the advance of the plunger may
mechanically cause the wheels to turn so that the device advances
over the tissue surface at the appropriate rate.
[0071] In addition to painting a layer of this therapeutic tissue
glue onto the brain surface or onto the surface of any body tissue
possibly invaded by cancer cells, it is also possible to inject a
column or deposit of the glue in a fashion similar to the catheter
arrays used for brachytherapy, but in which a column of tissue glue
incorporating radioactive nuclides in particles is incorporated.
Such administration can be monitored by concurrent imaging
techniques which take advantage of the inherent imagability of the
these particles (due to the density and magnetism of the iron core)
by ultrasound, magnetic resonance imaging, or X-ray based
techniques, or the gel can be supplemented by an additive contrast
agent.
[0072] Similarly, injection techniques can be used to inject
settable, ferrite or other particle-containing gel into the centre
of the tumour mass for purposes of brachytherapy, either with or
without the inclusion of chemical or biological agents capable of
causing either increased radiation sensitivity or capable of acting
as chemotherapeutic agents in their own right, to achieve a
multi-modal attack on the cancer cells. Administration in this
manner can also be achieved by injecting the glue with radioopaque
material but without the ferrite/particle solution, using two
barrels/needles from a three-part syringe system. Then, once the
position, shape, and setting of the glue are confirmed, the third
barrel/needle can be used to inject the particle solution into the
centre of the matrix/glue material which will hold the material
within its interstices. The needle is then very slowly withdrawn
along with the injection of additional glue, to seal the needle
tract.
[0073] Any such one, two, or three-barrel system for administration
of glue-based radiotherapy products may be equipped with a release
mechanism for detaching a plastic or silastic inside layer at the
tip of the needle. This is provided in case the column of glue
becomes adherent to the tip of the needle and allows the operator
to choose to leave the plastic behind in the needle tract to avoid
pulling out the column of glue as the needle is withdrawn.
Alternatively, this problem can be avoided with a more standard
glue application system as long as a `chaser` of cold glue is use
to follow the injection of radioactive glue.
[0074] In many situations, it will be desirable to inject the
radiotherapeutic glue in an array which distributes the therapeutic
material through the mass at a variety of locations. An example of
this occurs when a stereotactic system is used to allow a
neurosurgeon to place a needle or catheter into the middle of a
brain tumour by passing through a burr hole in the skull. Because
of the need to traverse brain tissue, it is undesirable to make
numerous needle passes in order to reach multiple sites in the
tumor. It has now been appreciated that a novel type of
administration device would solve this problem as well as similar
problems arising in other body regions where bulk tumor is to be
treated. The system (see FIG. 3) involves an outer sheath of a hard
material such as steel, titanium or plastics which carries a
plurality of internal flexible needle pairs which are prestressed
to spread outwards from the tip of the sheath. The needle pairs are
withdrawn within the sheath while the tip of the sheath is advanced
into the tumor. The internal set of needle pairs is then advanced,
upon which their tips emerge from the sheath and spread in various
directions and so puncture the tumor from inside towards the
outside in various directions. Once at their full extent, injection
is commenced as the needles are withdrawn back into the sheath. The
internal apparatus can then be rotated, e.g. 45.degree. and then
advanced a second time. After being withdrawn into the sheath
again, the sheath may then be advanced further into the tumor upon
which the internal needle are again advanced.
[0075] The following Example gives the steps to be taken in an
illustrative synthetic method for particles to be included in a
matrix.
EXAMPLE
[0076] Add 1.5 ml of 33% NH.sub.3 to 4.5 ml of hot dH.sub.2O (to
make up 7.5% NH.sub.4OH) and leave standing in a capped universal
tube in the water bath and bring to 60.degree. C.
[0077] Dissolve 1.25 grams of Dextran (MW 10,000) in 2.0 ml of
ddH.sub.2O then dissolve 225 mg FeCl.sub.3.6H.sub.2O in the dextran
solution. Other macromolecules such as proteins, fibrin, collagen,
starch, polylysine, or derivatized dextrans may also be used for
the coating. Alternatively, a trivalent lanthanide or Group IIIB
chloride may be substituted for 10-50% of the FeCl.sub.3. A variety
of unstable isotopes of various transition, lanthanide and actinide
elements can be introduced at this step as metal chlorides
dissolved in water or in an acidic solution of e.g. 0.1M HCl. The
amount of trivalent iron may be reduced where trivalent cations are
added.
[0078] Dissolve 100 mg FeCl.sub.2.4H.sub.2O in the Fe.sub.3/dextran
solution then place the mixture in a 60.degree. C. water bath for
two minutes. Some divalent cations may be added in place of Fe at
this step. Some metal chlorides such as, e.g. palladium chloride
will require an extended period of time up to e.g. one to two days
in concentrated HCl in order to become fully dissolved prior to
mixing with the other constituents. When trivalent lanthanides are
used, the crystal structure may be modified by the use of copper or
magnesium as the divalent cation instead of the FeCl.sub.2, or
other stable combination of cations such as FeCl.sub.2 with
ZnCl.sub.2 may be used to help accommodate Group IIIb elements such
as the yttrium.sup.90 isotope. Further, the reaction mixture may be
allowed to stand at room temperature or be cooled as low as
0-4.degree. C. prior to proceeding depending upon the desired size
distribution of the resultant particles where cooler reaction
temperatures tend to produce smaller particles.
[0079] Gradually add 6 ml of hot 7.5% NH.sub.3 solution (60.degree.
C.). The NH.sub.3 solution may also be added at lower temperatures,
e.g. 0-4.degree. C. or room temperature. Equivalence of temperature
and mixing to assure uniform concentration as well as more gradual
and dispersive addition of the NH.sub.3 solution will help reduce
the range of particle sizes. The product is left to stand in the
60.degree. C. water bath for fifteen minutes for Fe/Fe particles,
but the incubation may be extended up to four hours when
lanthanides or Group IIIB elements in substantial amount are used
in place of FeCl.sub.3.
[0080] The reaction product (dextran-coated ferrites) is spun at
1,000 g for 10 minutes and any precipitate is discarded. This
process is repeated to complete three spins and the supernatant
then applied to PD-10 columns equilibrated with 0.1M Na Acetate
buffer pH 6.8 with 5 mM EDTA.
[0081] The black eluted fraction is diluted 1:3 with EDTA/Acetate
buffer then concentrated to 1/10 of the initial volume with Amicon
Centriprep-100 ultrafilters. The retentate is then diluted 1:10
with EDTA/Acetate buffer then concentrated to a volume of 1.5 ml
with the C-100 ultrafilters.
[0082] At this point the preparation may be stored or further
concentrated. If it is to be used with a tissue glue, it can be
mixed with one component of the fibrinogen, fibrin, collagen,
acrylic, gelatin, resorcinol or other type of tissue glue, matrix,
or polymer precursor prior to application and mixing of the glue to
set on the tissue surface.
[0083] When it is desired to attach an additional ligand such as
for instance an antibody, lectin, or other agent which promotes
adherence to the glue matrix, the following steps as well as other
methods well known to those expert in the art of conjugation to
dextran may be used.
[0084] Add 0.30 ml of 20 mM NaIO.sub.4 to the dextran ferrite
solution (approx. 1.5 ml) while stirring then gently tumble or
shake for 60 minutes at room temperature in the dark.
[0085] At the end of the 60 minute periodate incubation, the
reaction is terminated by applying the reaction mixture to the
PD-10 columns equilibrated with 20 mM borate buffer (pH 8.5).
[0086] An active site blocking solution is prepared using 100 mM
MnCl.sub.2/CaCl.sub.2 for WGA binding reactions and appropriate
blocking agent for any other targeting protein to be conjugated to
the particle.
[0087] Dissolve 10 mg of the protein (e.g. cell targeting protein
or antibody) in 500 .mu.l of 20 mM NaBorate buffer pH 8.5 at room
temperature. The protein solution can be diluted to 12 ml with
borate buffer, then concentrated with Centriprep-10 concentrators
to remove DTT, glycerol, NaN.sub.3 and other undesirable storage
additives.
[0088] Add 10 .mu.l of the blocking solution to the protein/borate
solution then mix 2.0 ml of oxidized magnetite dextran with 500
.mu.l of the protein/borate solution. Pipette 20 .mu.l blocking
solution into the 2.5 ml protein-dextran-magnetite mixture and mix
well, then incubate for 6-18 hours at room temperature in a gentle
tumbling or shaking device.
[0089] After the incubation add 100 l of 0.5M glycine to the
reaction mixture and incubate an additional 2 hours. Then add 250
.mu.l of 0.25M NaBH.sub.4 to the magnetite-dextran-protein solution
and allow to stand for 60 minutes, shaking periodically to release
H.sub.2 gas. At the end of the incubation, pass the reaction
mixture through PD-10 columns equilibrated with 20 mM HEPES buffer,
pH 7.4. Dilute the eluant 1:5 with HEPES buffer then concentrate
with Centriprep-100 ultrafilters.
[0090] An affinity purification step is optional and detail is
given for use with a WGA(lectin) targeting protein by example.
Apply final retentate to affinity columns (20 mM HEPES), wash with
HEPES then carry out specific elution with 1M NAcGlu in HEPES
buffer pH 7.4. Pass the specific eluant through PD-10 columns
equilibrated with HEPES to remove NAcGlu, Mn and Ca.
[0091] The desalted output is then diluted to a volume of 24 ml
with HEPES buffer and concentrated with Centriprep-100
concentrators. The final retentate form is sterilized by spinning
at 500 g for one hour in 0.22 .mu.m centrifugal microfilters.
BRIEF DESCRIPTION OF THE DRAWINGS
[0092] FIG. 1 shows a balloon-tipped catheter system, for temporary
introduction of liquid brachytherapy agent, including a catheter 1,
collapsed balloon tip 2, stopcock 3, an adapter 4, radiotherapeutic
liquid 5 and an immiscible `chaser` fluid 6. FIG. 5A shows the
parts of the system; the four stages of its use are: B) the
assembled system with air evacuated from the catheter and balloon,
both being collapsed, the stopcock valve maintaining a seal, C) a
column of radiotherapeutic fluid being pumped into the catheter, D)
the fluid reaching and starting to fill the balloon tip, E) the
balloon tip fully filled with radiotherapeutic liquid and
non-radioactive immiscible chaser fluid filling the catheter up to
the balloon entry point. Optionally, a second tube may be used to
fill an internal balloon, or the first tube used to send down a
leading column of fluid to dilate an internal balloon with the
purpose of creating a thin shell of radioactive fluid against the
inner surface of the outer balloon.
[0093] FIG. 2 shows a lead-shielded double-syringe device for
applying a thin sheet of radiotherapeutic tissue glue. The syringes
include barrels, one indicated at 7, a wheel 8 placed between the
terminal portions of the dispenser plates to maintain a uniform
distance from the tissue surface, an optional wheel 9 with
penetrating feet, an optional wheel 10 with a thin silastic outer
rim, and two dispenser plates 11 seen in lateral view, one behind
the other. FIG. 2F is a lateral view of the system without the
spacing wheel; FIG. 2G is a lateral view of the system with one of
the optional wheels in place, and FIG. 2H is an anterior view of
the assembled double-syringe system showing the appearance of one
of the various widths and shapes of disposable dispenser plates
which may be affixed to the syringe system.
[0094] FIG. 3 shows a device for distributing therapeutic adhesive
within a tumor mass, including a sheath 12, a plunger shaft 13, a
plunger/manifold cover 14, needles 15 (at 15b, viewed from above
with four double-barrelled needles extended), double-barrelled
syringe 16, connecting tubing 17 for carrying glue components to a
manifold 18 dividing flow of glue components into four sets and
then pairing up the sets of double-barrelled needles, one pair of
needles shown at 19 emerging from manifold cover to enter the
plunger shaft, and, shown at 20, a fully-extended set of
double-barrelled needles spreading out from sheath tip to penetrate
tumor in various directions. FIG. 3J shows the plunger lifted to
withdraw needles back into the sheath. FIG. 3K shows the plunger
advanced to force the four double-barrelled needle sets out into
the tumor in various directions, and FIG. 3L shows the syringe
manifold system which allows distribution of the two component glue
into the double-barrelled needles after they are in place and while
they are being withdrawn.
1TABLE 1 Relevant Stable Nuclides .sub.6C 12(98.9%), 13(1.1%)
.sub.8O 16(99.76%), 17(0.04%), 18(0.2%) .sub.25Mn 55(100%)
.sub.26Fe 54(6%), 56(92%), 57(2%), 58(0.3%) .sub.27Co 59(100%)
.sub.28Ni 58(68%), 60(26%), 61(1%), 62(4%) .sub.38Sr 84(.6%),
86(10%), 87(7%), 88(82%) .sub.39Y 89(100%) .sub.40Zr 90(51%),
91(11%), 92(17%), 94(18%), 96(3%) .sub.44Ru 96(5%), 98(2%),
99(12%), 100(12%), 101(17%), 102(32%), 104(18%) .sub.45Rh 103(100%)
.sub.46Pd 102(1%), 105(22%), 106(27%), 108(26%), 110(11%) .sub.47Ag
107(52%), 109(48%)
[0095]
2TABLE 2 Pd n, .gamma. n, p .alpha., 2n 102 103Pd 102Rh 104Cd (17
d, EC) (2.9 y, EC) (58 m, EC) 105 106Pd 105Rh 107Cd (stable) (35 h,
.beta.-) (6 h, EC/.beta.+) 106 107Pd 106Rh 108Cd (10.sup.6 y,
.beta.-) (29 s, .beta.-) (stable) 108 109Pd 108Rh 110Cd (13 h,
.beta.-) (17 s, .beta.-) (stable) 110 110Pd 110Rh 112Cd (stable) (3
s, .beta.-) (stable)
[0096]
3 TABLE 3 Cyclotron Reactor (p, n) (n, .gamma.) .sup.56Fe ->
.sup.56Co (77 d, .beta.+) .sup.56Fe -> .sup.57Fe (stable)
.sup.16O -> .sup.16F (10.sup.-20 s, p) .sup.16O -> .sup.17O
(stable) .sup.12C -> .sup.12N (11 ms, .beta.+, .alpha.) .sup.12C
-> .sup.13C (stable) .sup.103Rh -> .sup.103Pd .sup.102Pd
-> .sup.103Pd (17.5 d, EC) .sup.89Y -> .sup.90Y (64 h,
.beta.-) (d, n) (n, p) .sup.56Fe -> .sup.57Co (271 d, EC)
.sup.56Fe -> .sup.56Mn (2.6 h, .beta.-) .sup.16O -> .sup.17F
(64 s, .beta.+) .sup.16O -> .sup.16N (7 s, .beta.-, .alpha.)
.sup.12C -> .sup.13N (9 min, .beta.+) .sup.12C -> .sup.12B
(.02 s, .beta.-, .alpha.) .sup.90Zr -> .sup.90Y (64 h, .beta.-)
(.alpha., pn) .sup.56Fe -> .sup.58Co (70 d, .beta.+) .sup.16O
-> .sup.18F (109 min, .beta.+) .sup.12C -> .sup.14N (stable)
.sup.88Sr -> .sup.90Y (64 h, .beta.-) (.alpha., 2n) .sup.58Fe
-> .sup.58Ni (stable) .sup.16O -> .sup.18Ne (1.7 s, .beta.+)
.sup.12C -> .sup.14O (70 s, .beta.+) .sup.101Ru ->
.sup.103Pd
* * * * *