Scientists tout diamond-coated implants

A newly-developed coating for medical implants could help to reduce the number of MRSA infections, according to UK physicists.

The diamond-like carbon (DLC) coating, which makes implants harder wearing, reduces friction between components and protects them from corrosion, has several advantages over its rivals, according to researchers at Brunel University.

It is bio-compatible, and doesn't trigger coagulation of blood - a significant problem with some other coatings. The coating process can take place at relatively low temperatures, too, meaning that plastics as well as metals and ceramics can be coated with DLCs.

The researchers, led by Professor Joe Franks, report that DLC-coated knee implants have already been successfully used in two operations in arthritic patients who are allergic to the underlying metal.

Franks said: "We've also developed coatings that can be used for catheters and various medical implants that go through the skin. The coating is important because it prevents colonization of the tissue by bacteria, such as the superbug MRSA."

Speaking at an Institute of Physics conference today in Chester, the researchers from Brunel University said they can also use DLC to coat collagen.

Collagen, a protein that occurs naturally in the body, can be used to construct bypass arteries, or as a so-called patch graft in repair operations. Lining it with DLC means that when it is being used as an artery, the blood can flow more freely through it. When it is being used as a graft, it is chemically more inert, and less likely to degrade.

DLCs were first synthesised in 1971, using a process that involved spraying charged carbon atoms at the surface to be coated.

Franks and his team have developed a new technique called "plasma-assisted chemical vapour deposition" whereby a hydrocarbon gas is stripped of its electrons to produce a cloud of positively charged carbon ions. These are attracted to the negatively charged component, and hey presto! - you have a coated implant.

"The advantage of this method is that the ionised plasma surrounds the component, which means it does not need not to be manipulated inside the chamber to get an even and uniform coating," Franks explained.

He added that the ion energy can be varied, as can the composition of the gases in the chamber to vary the properties of the coating.

The next stage of the research is to work out how best the properties can be varied for different applications. ®