The most precious of all minerals, diamonds are the ultimate dream of jewelers and jewelry lovers. In the past, they had wars fought over them, but today synthetic diamonds developed by researchers at the £ód¼ University of Technology have brought about a revolution in medicine. Doctors have used implants covered with a microscopic diamond layer and discovered that they are well tolerated by patients.

Work to synthesize diamond-like layers in a laboratory started in the 1950s, and the first such layers were obtained in 1971. Poles joined the research in the 1980s; a pioneering team of researchers headed by Prof. Stanis³aw Mitura worked at the £ód¼ University of Technology. Poland also hosted the world's first Diamond Conference in 1985, organized by Prof. Aleksandra Soko³owska from the Warsaw University of Technology. The conference sparked off a lot of interest in diamond layers, and scientists sought diverse applications for them, from electronics to tool making to medicine. However, before long the researchers faced a serious obstacle as carbon layers adhered very poorly to their metal base. As a result, many research centers around the world gave up and the late 1990s brought a considerable slowdown in the research endeavor.

The situation changed thanks to Mitura and his team's publications on diamond layers in medicine. An important part was also played by a Ph.D. thesis written by Piotr Niedzielski of the Materials Engineering Department of the £ód¼ University of Technology. It was probably the world's first doctoral thesis to deal with medical research on nanodiamonds.

The researchers at the £ód¼ University of Technology developed a new technology of diamond production in laboratory conditions, and they also succeeded in creating the tiniest diamonds in the world. The effects of that discovery cannot be overestimated. The crystals, a few nanometers in size (1 nm is one-millionth of 1 mm), can be used to form an ultra-thin film on medical implants. This marks a turning point in medicine because the diamond layer has once and for all eliminated the problem of implants being rejected by the human body.

"Diamond is carbon, and carbon is the core component of human tissue," said Niedzielski, one of the creators of the nanocrystal diamond technology. "When the carbon layer covers stainless steel or titanium, of which implants are made, it separates the implant from the tissue, which recognizes the layer as the body's own and will not fight the implant. We simply cheat the patient's body, and very successfully so. So far there have been no reports of any instances of rejecting a diamond-coated implant."

Saving a leg
The £ód¼ researchers were the first ones in the world to use diamond layers in medicine-quite by accident. In 1993, they got a phone call from Pawe³ Witkowski, a physician working in a hospital in Pabianice. He had a patient with a complicated femur bone fracture. The patient's body had rejected two typical implants made of stainless steel, and amputation seemed to be the only option left. An implant covered with nanodiamonds was the man's last hope, and so the hospital asked the researchers to prepare one. The researchers agreed even though they had only just published their first papers on the subject, after a few years of laboratory research. They had not conducted any clinical tests. "To a large extent, it was a 'forced' application," Niedzielski says jokingly. "But faced with the amputation-vs.-experiment alternative, we went for the latter. The patient's body accepted the carbon-layer implant without any problems, and the patient remains in perfect shape to this day. His leg was saved and we were powerfully encouraged by that. The surgery in Pabianice was a turning point and we entered a new phase of close cooperation with doctors."

The only ones to succeed
Nanodiamond layers could only be applied in medicine after the researchers solved the adhesion problem. Niedzielski used his own method of producing diamond layers in a plasmochemical reactor chamber, which he had designed as part of his doctoral research. He called the method Radio Frequency Plasma Activated Chemical Vapor Deposition, or RF PACVD. The high temperature in the chamber causes methane particles to disintegrate and release carbon atoms which then permeate the implant placed inside the chamber. Other carbon atoms crystallize on the surface. In this way the implant becomes covered in a diffusion layer that spreads over the surface and inside the implant. The entire layer is a few micrometers thick; the external coating is only 300-500 nm thick, depending on the duration of the procedure. Numerous tests on different bases (stainless steel and titanium used in the production of implants) have shown that such diamond layers display perfect adhesion. The implant surface is durable, and there is no risk that the layer could be removed during the implantation. It is also resistant to abrasion and dissolution once it is placed inside the body. Instead, the coating separates human tissue from the metal completely.

"Many scientists dream of obtaining the largest possible diamond in a lab, with properties as close to a natural diamond as possible," said Mitura. "The real challenge, however, are the tiniest crystals with some extra properties. Such diamonds can be applied in medicine to save human health and lives. Implant rejections were a huge challenge because an estimated 20-30 percent of the population are allergic to chromium and nickel. Nickel is a component of stainless steel from which implants are made. In allergic patients, the implant instantly causes an allergic reaction, and doctors must remove it. The problem is that usually there is no alternative method to help such a patient."

Implant rejection is not the only problem. Sometimes, implants begin to corrode in the human body, which leads to metalosis, or a process whereby metal ions and other corrosion products penetrate tissue, causing toxic reactions in the body. The diamond layer prevents that.

Medicine needs them
Some types of diamond implants have been certified for use in medical treatment. For a year, hospitals across Poland have been using diamond-coated intramedullar nails. So far 200 such nails have been implanted, and no incidence of intolerance has been reported. Polish orthopedists have also implanted dozens of diamond-coated screws.

Improved nanodiamond implants are especially popular in orthopedic and trauma surgery, neurosurgery and dentistry. In all these branches of medicine, clinical tests have been successful. Excellent results have been obtained in dentistry after selected patients received diamond-coated bridgework and implants. However, implants cannot be used on a widespread basis because there are no producers.

A unique device has been designed for cardiology. It is a diamond heart valve that is undergoing tests at Prof. Zbigniew Religa's Foundation for the Development of Heart Surgery in Zabrze. The valve was designed by Prof. Jacek Mol, MD, an engineer and graduate of the £ód¼ University of Technology who heads the heart surgery department at the Mother and Child Institute in £ód¼. In cooperation with his former university, Mol modified the valve's surface, providing it with a diamond coating. At the current research phase, it seems the procedure will radically increase human tolerance to the valve and improve its durability.

All diamond-coated implants currently in use in medical treatment or undergoing tests were produced at the Materials Engineering Institute of the £ód¼ University of Technology. But as demand grew, the institute found it increasingly difficult to keep up with orders. "The school is not a factory, while we have been forced to develop production on a semi-industrial scale," Niedzielski says. "In reality, what we should be doing is conduct research, develop new technologies rather than actually produce what we have invented. From now on, diamond implant production will be handled by the Be³chatów-Kleszczów Industry and Technology Park, in operation since the end of 2003."
Ewa Dereń


How Diamond Layers Are Formed
A new technology developed by the £ód¼ University of Technology does not yet have a good Polish name. In English, it is known as Radio Frequency Plasma Activated Chemical Vapor Deposition, or RF PACVD. The method is based on the decomposition of plasma methane under high frequency (13.56MHz) and at a pressure of 20-400 Pa. Diamonds are made from methane, a gas that contains carbon atoms. If the carbon atoms from methane become ionized and immediately bond in such a way that they form a specific molecular structure of carbon, diamond is made. The entire process takes place in the chamber of a plasmochemical reactor that contains an implant coated with a nanodiamond layer. Carbon atoms freed from methane molecules settle on the implant's surface. The atoms may also settle elsewhere; as a result of high-energy phenomena that occur in the chamber, the carbon atoms may also penetrate to the inside of the implant, which creates a diffusion layer, an integral part of the implant that is resistant to abrasion. The process is short, taking only 10 minutes. The presence of diamond layers on the implant is indicated by a change in its color. Nanodiamonds themselves, not visible to the naked eye, can be seen through the use of an atomic force microscope (AFM) with a very high resolution.