Supersized micro-magnets made to measure for high-precision drug delivery
Some magnetic particles can take on certain attributes when they come in small enough packages, say a few millionths of a millimeter. These special magnetic properties have caught the eye of medical scientists, who have regarded them as potential high-precision tools for carrying drugs to tumor sites with the help of magnetic fields, but their diminutive nature has made them impossible to steer toward the target. Scientists have now found a way to scale up these particles while retaining their desirable magnetic properties, making it possible to commandeer them for the purposes of life-saving drug delivery, among other applications.
When certain magnetic nanoparticles are of a certain minute size they gain an unusual ability – their magnetization will randomly flip when influenced by temperature. This phenomenon, known as superparamagnetism, has actually held back data storage technologies in the past, where shrinking data bits beyond a certain threshold will bring some unwelcome instability to the mix.
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But another characteristic these particles possess is that when exposed to a magnetic field, they pick up the strongest form of magnetism known to science. The thinking is that if these particles could be loaded up with drugs that require a very precise delivery – such as those directed toward a tumor – and then steered successfully toward that target, it would be a breakthrough that could save many lives. But scientists have been unable to control this movement.
Now researchers from China's Quingdou University of Science and Technology are claiming a big step forward in this area. The team came up with a method of manufacturing the particles that, perhaps counterintuitively, places them under a whole lot of stress to gain much-improved performance.
By preparing magnetite crystals at high temperature and under high pressure, tiny meteorite-like specks of the substance escape from the surface of the crystal. This in turn creates a large amount of stress on the crystals as they grow and leads to irregularities and defects in the finished product. Defects that, as it turns out, give them superparamagnetic properties despite their larger-than-superparamagnetic size.
"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," explains Kezheng Chen, from Quingdou University of Science and Technology, "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."
The team says that particles of this size with such a high degree of magnetism could open up all kinds of possibilities. These include more targeted drug delivery, along with the development of smart fluids that change in response to magnetic fields. These could be used for self-adjusting car suspensions that change in tune with road conditions and more comfortable prosthetic limbs. And with its supersized superparamagnets in hand, the team will now start to explore these possibilities.
The research was published in the journal Physics Letters A.