UBC Reports | Vol.
51 | No. 4 |
Apr. 7, 2005
Need a Joint Repair? Stick a Sponge in it
By Hilary Thomson
Tiny, full of holes, yet effective -- drug-filled implantable
sponges may be a new way to promote bone growth in orthopedic
surgeries, say a pair of UBC scientists.
Helen Burt, of the Faculty of Pharmaceutical Sciences, and
Tim Durance, of the Faculty of Agricultural Sciences, have
teamed up to create a biodegradable sponge that can be filled
with microspheres full of growth factors (proteins), antibiotics
and stem cells for use in joint repairs.
The research is part of a five-year project, funded by $1.5
million from the Canadian Institutes for Health Research,
that sees a team of UBC scientists working together to create
a new fixative material.
Small chips or beads of sponge could be inserted into spaces
at the site of bone defects and repairs, or at hip replacement
surgical sites. The sponge would release its contents at a
controlled rate to stimulate cells to produce bone material.
This bony matrix would help the prosthetic joint to fuse into
surrounding bone and tissue.
The two scientists connected in what Burt -- an expert in
drug delivery systems -- calls “a stunning piece of
She knew she needed a porous material and her research team
was attempting, for the first time, to make sponges from a
chemical recipe. It wasn’t going well.
Meanwhile, Durance was looking for new applications for a
technique used to dehydrate food. The technique produces porous
material such as sponge, and allows the organic structure
of the material to be maintained, even though it is completely
A colleague, who knew the work of both scientists, realized
they were destined to collaborate and made the introductions.
“I knew that the technique had more potential, especially
in the medical materials field, so this collaborative opportunity
really came at the right time,” says Durance, who directs
the Food, Nutrition and Health program.
The technique evaporates liquids from biological materials
via microwaves that are applied in a vacuum, which produces
a boiling point of about 30 degrees Celsius, much lower than
normal. The technique can create foams and sponges from all
sorts of moist biological materials such as proteins, carbohydrates,
gums and gels. However, the equipment was designed for batch
sizes up to 10 lbs. The expense of the pharmaceutical materials
Burt uses dictates an optimum batch size of less than a gram.
Durance is now miniaturizing his equipment to handle the amounts
required for the study.
“The ability to make sponge from almost any material
has expanded our research ten-fold,” says Burt, who
is associate dean, Research and Graduate Studies, in the Faculty
of Pharmaceutical Sciences. “We now have a staggering
array of possibilities to test different sponge materials
and see how they work with different drug-carrying microspheres.”
Sponge offers a multitude of spaces and surface areas for
chemical reactions to take place. The researchers will develop
a sponge that will allow stem cells to attach, proliferate
and migrate, as well as provide the open spaces needed for
cell movement and new blood vessel growth. Sponges may also
be useful for holding antibiotics, which could be released
slowly to prevent infections at orthopedic surgical sites.
Other properties, such as being biodegradable, compatible
with tissues and cells and having some mechanical strength
make sponge an excellent material for this application, says
She says scientists know lots about microsphere release of
drugs, but “absolutely zero” about how the release
might work after microspheres are embedded in sponge. Research
challenges include ensuring the molecular structural integrity
of drugs that are encapsulated, confirming that stem cells
can attach to sponge, and controlling the timed release of
the drugs in the sponge environment.