Magnetic crystals hold drug delivery potential

Chinese researchers have discovered a way to control microscopic crystals using magnetism, leading to hopes that it could be used to apply cancer treatments directly to tumours.

When magnetised, these minute crystals are able to reverse their magnetic field as the temperature changes – known as superparamagnetism. The scientists have succeeded in creating crystals large enough to be manipulated using magnetism.

Kezheng Chan, from Quingdou University and co-author, said: “The largest superparamagnetic materials that we have been able to make before now were clusters of nanocrystals that were together about a thousand times smaller than these. These larger crystals are easier to control using external magnetic fields, and they will not aggregate when those fields are removed, which will make them much more useful in practical applications, including drug delivery.”

During the creation of these magnetite crystals, high temperature and pressure cause tiny micro particles of magnetite to escape. This leads to an unusual pock-marked surface on the crystal, inducing a high degree of stress and strain into the growing crystals’ lattice.

This method of creating large superparamagnetic crystals could lead to the development of bulk materials controllable by external magnetic forces. Forming irregularities are they are grown; it is these that are responsible for superparamagnetism. Similar crystals grown at a lower temperature and lesser pressure were only weakly magnetic.

Applications may not be linked to just biology, these crystals could be used in engineering projects that need ‘smart fluids’ which change their properties when a magnetic field is applied. For example, vehicle suspension systems could adjust automatically as road terrain changes. It could also be used to build prosthetics that are both more comfortable and realistic.

Assisted by Dr Ji Ma, also from Quingdou University, the research is published in Physics Letters A.