Large hollow magnetic cage molecules could one day be used in medicine as a drug delivery system to non-invasively treat tumors, according to Virginia Commonwealth University (VCU) researchers.

About 25 years ago, scientists first made the discovery of C₆₀ fullerene — better known as Buckminster Fullerene — a molecule composed of 60 carbon atoms that formed a hollow cage.

Its unique hollow cage structure offers serious technological potential because it could hold other atoms or small molecules inside, so it could be used in applications such as drug delivery.

That potential has since spurred worldwide interest among scientists who have been searching for similar molecules. Although some hollow cage structures have been found, none of them is magnetic.

Magnetic properties of the structure are of particular interest because a hollow magnetic structure carrying an embedded atom or molecule (such as a drug) can be guided by an external magnetic field and may serve as an effective vehicle for targeted drug delivery. Current methods of delivering drugs using a magnetic cage with an external magnetic field are not precise.

In a new study, published on July 22 in The Journal of Chemical Physics, two VCU scientists employing state-of-the-art theoretical methods show that magnetic hollow cages — larger than the original C₆₀ fullerene — that carry giant magnetic moments are possible. A magnetic moment is a measure of the magnetic strength of a cluster.

“The potential benefit of this finding is that it provides a route to the synthesis of molecular magnets with colossal magnetic moments,” said co-lead investigator Puru Jena, Ph.D., distinguished professor of physics in the VCU College of Humanities and Sciences. “These molecules can be used for targeted non-invasive drug delivery. When assembled, the molecules can also form new high strength magnets for device application.”

Jena and Menghao Wu, Ph.D., co-author of the paper and a postdoctoral scholar in the VCU Department of Physics, demonstrated the magnetic moment of the molecule by focusing on hetero-atomic clusters consisting of transition metal atoms such as cobalt (Co), manganese (Mn), and carbon (C) atoms.*

According to Jena, the team is still early in its discovery process. “Ways must be found to synthesize large quantities of these molecules and study their magnetic properties once they are assembled. Finally, these molecules need to be functionalized by embedding desired atoms/molecules for practical applications.”

This research was supported in part by the U.S. Department of Energy.

* In particular, Co₁₂C₆, Mn₁₂C₆, and Mn₂₄C₁₈ clusters consisting of 12 cobalt and six carbon atoms, 12 manganese and six carbon atoms, and 24 manganese and 18 carbon atoms, respectively, carry magnetic moments as large as 14, 38 and 70 Bohr magnetons. In comparison, the magnetic moment of an iron (Fe) atom in crystalline iron is 2.2 Bohr magnetons.