The new study, led by Lily Peng at UCSF, shows that TiO2 nanotubes can control the long-term delivery of both small molecules and protein therapeutics. This is in contrast to previous approaches that employed a polymer coating on top of a metal stent or ceramic implant to control the release of drugs, explains team leader Tejal Desai of the University of California, San Francisco.

"Our approach builds an inorganic nanostructure (TiO2 nanotubes) on the implant surface so that drug elution can be controlled without using polymers," she told Polymers can often cause an inflammatory reaction as they degrade in the body, especially in stent applications.

The researchers say that they can grow the nanotubes directly off an implant surface, so it can be of any shape. Moreover, many nanotubes can be assembled onto a large surface area and all of them can be filled with drug molecules at the same time.

The nanotubes diffuse small drug molecules for several weeks, and larger ones for a month. The drug eluted is also bioactive and the rate at which it is eluted depends on the diameter of the tube.

According to the researchers, TiO2 nanotubes might be used in drug-eluting stents and for the local release of antibiotics, drugs or growth factors from orthopaedic and dental implants. They now plan to conduct in vivo studies, particularly for vascular stent applications.

The work was reported in Nano Letters.