UBC Reports | Vol. 51 | No. 1 | Jan. 10, 2005

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 potential.”

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 repair.

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 marrow.

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 scanner.

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 with polymers.

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.