Researchers demonstrate shape memory alloys in medical implants

A European team has demonstrated that modern technological materials used in a wide range of medical devices and implants are entirely biocompatible and should not health problems as has previously been suggested.

Writing in the International Journal of Immunological Studies, Rebeka Rudolf of the University of Maribor, Slovenia, and colleagues there and at the University of Leoben, Austria, and the Military Medical Academy, in Belgrade, Serbia, explain how shape memory alloys (SMAs) are used increasingly in medical implants, guide wires for catheters, blood vessel stents, filters and actuators. Devices and components made from these materials can be bent and squeezed into a target body cavity or vessel after which they then revert to their original, working shape. Concerns about the toxicity of SMAs, which often contain nickel or copper, have been voiced despite earlier tests that show them to be entirely biocompatible.

Now, Rudolf and colleagues have used immune system cells, human peripheral blood mononuclear cells, to demonstrate that SMAs made from copper-aluminium-nickel (Cu-Al-Ni) and nickel-titanium (Ni-Ti) do not damage the body or trigger cell death.

The researchers prepared samples of SMAs as thin ribbons using melt spinning. They then cultured PB-MNCs from 20 donors in a solution containing a Cu-Al-Ni SMA and saw no significant changes in the production of immune system mediators, known as cytokines, in 18 of the 20 test cultures. However, for two of the donor cells there was a marked immune response thaws easily seen as inflammatory cytokines were released by the cells. The team suggests that their test could provide the medical profession with a quick and easy way to test a prospective patient for biocompatibility of a particular device.

"This is the first report showing the influence of SMA materials produced as thin ribbons by spin melting technology on human cells," the team says. "By using a simple screening test it should possible to identify those individuals who would develop an inflammatory response in contact with a biomaterial and so predict undesirable reactions before implantation," they add.