"Halloysite nanotubes are natural and biocompatible and have already been used in some screening studies," Kurt Geckeler of the Gwangju Institute of Science and Technology (GIST) told nanotechweb.org. "They are fascinating materials not only for drug delivery but also as versatile composites."

The process involves ball-milling equal amounts of halloysite (a clay mineral) and DNA to form a fine power, which is then dissolved in water and centrifuged. The supernatant was found to contain as much as 22% halloysite, according to TEM, FTIR and UV-vis-NIR analysis.

Milling the HNT-DNA mixture for 20–30 min gives a product that is stable in water for up to 6 weeks. The processing time is critical as milling for an extended period (40–60 min) can damage and even totally destroy the clay mineral's tubular structure.

After 20–30 minutes of ball milling, the length distribution of the HNTs is as follows:

200–400 nm (30–40%)
400–600 nm (15–25%)
600–800 nm (15–25%)

"We are currently studying several applications such as the tailored delivery of drugs and are working on several patents in this area," said Geckeler. "Work is underway in collaboration with Clemson University, US, where I am currently spending my sabbatical with one student from my group in Korea, to manipulate the tubes on the nanoscale."

The researchers presented their work in Nanotechnology.