Drug-loaded nanoparticles could fight infections and clots

Lund University researchers in Sweden have created magnetic nanoparticles that they have directed to metallic implants such as artificial knee joints, hip joints and stents in coronary arteries.

Associate professor Maria Kempe, her brother and colleague Dr Henrik Kempe and members of staff at Skåne University Hospital have shown that the principle works in animal experiments.

They have succeeded in attaching a clot-dissolving drug to the nanoparticles and, with the help of magnets, directed the particles to a blood clot in a stent in the heart to dissolve it.

A stent is a tube-shaped metal net used to treat narrowing of the coronary arteries. First the artery is expanded using a balloon catheter, then a stent is inserted to keep the artery open. However, the method is not without problems — depending on the type of stent inserted, the cells of the artery wall can grow and again obstruct the artery or a blood clot can develop in the stent.

In the Lund researchers’ experiments, the nanoparticles were coated with a drug used to treat blood clots. But the particles could also carry other drugs, such as drugs to stop the cell growth that makes an artery become narrower.

Prof Kempe said: ’They could also carry antibiotics to treat an infection developed after insertion of an implant. We have developed polymer materials that can be loaded with antibiotics too.’

Guiding drug-loaded magnetic particles using a magnet outside the body is not a new idea. However, previously it has only been possible to reach the body’s superficial tissue and the particles have often been obstructed by small blood vessels.

The Lund researchers’ attempt has succeeded partly because the particles are small enough to pass through the arteries and partly because the target has been a metallic stent. When the stent is placed in a magnetic field, the magnetic force becomes sufficiently strong to attract the magnetic nanoparticles. For the method to work the patient therefore has to have an implant containing a magnetic metal.

Prof Kempe added: ’It will take many years to develop a treatment method that can be used on patients. But the good initial results make us hopeful.’