Microscopic crystals could soon be zipping drugs around patients’ bodies, taking the therapies to diseased organs. In the past, the crystals, which have magnetic properties, were so small that scientists couldn’t control their movement. But now a team of Chinese researchers has found the solution, and has opened new applications for the crystals that could save lives.
If some magnetic materials, such as iron oxides, are small enough––perhaps a few millionths of a millimeter across, smaller than most viruses––they have an unusual property: their magnetization randomly flips as the temperature changes.
By applying a magnetic field to these crystals, scientists can make them almost as strongly magnetic as ordinary refrigerator magnets. It might seem odd, but this is the strongest type of magnetism known. The phenomenon is called superparamagnetism.
Superparamagnetic particles could be ideal for drug delivery, as they can be directed to a tumor simply by using a magnetic field, the investigators said. Their tiny size, however, has made them difficult to guide precisely, until now. Scientists in Quingdou, China, have found a method of producing much-larger superparamagnetic crystals and have published their findings in Physics Letters A. These large crystals do not show the unwanted magnetic properties of smaller crystals.
“The largest superparamagnetic materials that we had been able to make before now were clusters of nanocrystals that were together about a thousand times smaller than these,” said lead investigator Dr. Kezheng Chen. The large crystals are about the width of a human hair.
This discovery paves the way for superparamagnetic bulk materials that could revolutionize drug delivery in the body, according to the investigators. And that could be just the beginning. Chen’s crystals might be useful, for example, in the many engineering projects that need “smart fluids” to build better human prostheses.