UBC Reports | Vol.
51 | No. 1 | Jan.
Tiny Magnetic Couriers Deliver Drugs
The use of magnets to draw capsules directly to cancer tumours
and diabetic ulcers holds enormous potential, says researcher
By Hilary Thomson
Tiny drug couriers with magnetic personalities could offer
new solutions for patients who need drugs delivered directly
to tumours, diabetic ulcers and other disease sites.
Urs Hafeli, a UBC assistant professor of pharmaceutical
sciences, is an expert in targeted therapies that use magnetism
to get drugs where they need to go.
“I really want to get more magnetic therapies to patients,”
he says. “The theory is deceptively simple but we know
using magnets to concentrate drugs in the body has enormous
Tiny magnetic particles -- magnetic microspheres -- can
be filled with drugs or radioactive materials to treat a variety
of illnesses. Magnets applied outside the body attract the
spheres to the disease site where they deliver therapeutics
in a targeted way.
One of only a handful of investigators in Canada to work
with magnetic microspheres, Hafeli is the only researcher
in the world to explore how radioactive magnetic microspheres
can be used to treat several types of cancer.
One of Hafeli’s ideas -- which has not yet been approved
for funding -- is a magnetic bandage, which may offer a new
solution for thousands of Canadians who face foot or leg amputation
because of diabetic skin ulcers that won’t heal.
Diabetic foot ulcers are sores that occur in 15 per cent
of diabetic patients some time during their lifetime. The
risk of lower-extremity amputation increases eight-fold in
these patients once an ulcer develops, usually because of
nerve and blood vessel complications of the disease.
Hafeli’s idea has two steps. First, the wound site
would be covered with thin but strong magnets embedded in
a bandage. The next step involves injecting microspheres into
blood vessels near the wound that are filled with slow-release,
healing growth factors.
The magnets attract the microspheres to the immediate area
of the wound site and stop them there. The spheres gradually
break down and release growth factors over a period of weeks,
allowing blood vessels and damaged tissues to re-grow and
Hafeli, who arrived at UBC in July 2004, has recently applied
for funding to support the investigation.
The beauty of magnetic microspheres, he says, is that they
can carry highly active and sometimes toxic drugs that normally
could not be tolerated within the body.
Small amounts of drug targeted magnetically to localized
sites can replace large doses of drug that, using traditional
administration methods, freely circulate in the blood and
hit the target site in a generalized way only. Also, drugs
within the sphere are protected from breaking down during
transport and, because they are targeted instead of distributed
in blood, don’t harm some sensitive organs such as bone
Hafeli is exploring magnetic microspheres as an alternative
to traditional radiation methods which use highly penetrating
radiation that is absorbed throughout the body. Its use is
limited by toxicity and side effects. Hafeli loads his microspheres
with radioactive tracers that emit beta radiation. Beta radiation
consists of electrons that interact with cells within a one-centimetre
range only, virtually eliminating side effects.
Spheres can be made of a variety of materials. Some -- like
albumin or gelatin -- are biodegradable and others, such as
glass, can reside in the body without negative effect.
Magnetic radioactive microspheres are applied in methods
similar to non-radioactive spheres. A magnet, placed outside
the body, is directed to the target site. The magnet can be
a rod-shaped permanent magnet of any size or can be contained
in equipment that looks like an open magnetic resonance imaging
The loaded microspheres are introduced into a blood vessel,
and in as little as half an hour, they gather at the target
site to emit radiation that kills surrounding cancer cells.
The therapeutic action lasts until the radioactive material
has decayed, usually a couple of days or weeks, depending
on the material used. If necessary, the treatment can be repeated.
Specializing in biodegradable spheres, Hafeli works primarily
He is exploring a number of factors that affect the therapeutic
value of the technology. In this tiny treatment world, size
matters. One challenge is to find new ways to make uniform-sized
microspheres. In addition, the spheres need to be small enough
to not clog the narrow blood capillaries.
In addition, spheres need to be peppered with microscopic
magnetic particles, such as iron, so they will be attracted
to the magnet. Hafeli is evaluating the toxicity of these
magnetic nanoparticles as one part of his work.
Although magnetic microsphere research is in an early stage,
scientists have been exploring how the spheres can treat liver
and brain tumours, and first results appear promising. Hafeli
is also focused on improving magnetic microspheres so they
can be used in a greater variety of treatments. He plans to
investigate magnetic treatment of head, neck and lung tumours
as well as finding ways to improve delivery of rheumatoid
arthritis drugs to affected joints.
Determining optimum sphere size, effective magnetic forces
and other factors takes the expertise of scientists in disciplines
that include physics, chemistry, biology and medicine. Hafeli
works with UBC collaborators at TRIUMF -- Canada’s national
laboratory for particle and nuclear physics -- and the departments
of chemistry and chemical engineering. He also organizes international
conferences of researchers and clinicians interested in magnetic
drug carriers. The next meeting is in Austria in May 2006.