Precious metals

PHOTO CREDIT: TANAKA PRECIOUS METAL TECHNOLOGIES

Materials and components made from high-quality precious metals are playing a growing role in medical devices for a wide variety of procedures including cardiovascular, peripheral vascular, neurovascular, and mammography. The following is a summary of precious metals and their characteristics and expectations in the medical industry.

Whereas polymers tend to break down with hydrolyzation and dissolve in human bodies throughout the years, precious metals and their alloys have proven more durable. Acids, alkalis, and oxidation tend to have limited negative effects on precious metals, making them especially valuable when used in medical devices intended to remain in the body for a long time, such as for remote monitoring.

But there are additional crucial questions the medical device industry must satisfy in choosing which precious metals to use in which instruments. What qualities make which metals suitable for existing and emerging medical processes, especially the minimally invasive and non-invasive procedures increasingly favored over traditional surgeries? For example, which metals are safest and most compatible with the human body? Which metals enhance the visibility of devices during X-rays? And what’s necessary to produce metals and alloys so they meet the medical device industry’s requirements in other areas, such as purity percentage?

Biocompatibility

Medical devices coming into contact with human tissue and fluids must be safe, nontoxic, non-irritating, and not encourage blood clotting, inflammation, or other postoperative complications. Consequently, the proven biocompatibility of precious metals such as platinum, iridium, and gold have made them preferred choices for more cardiovascular, dental, and orthopedic implants as well as other medical devices.

Platinum iridium rings, for example, are being used in electrophysiology (EP), ablation, irrigation, and intravascular ultrasound (IVUS) catheters, and platinum alloy wires are being used as coil tips for guidewires, embolic coils, and flow diverter stents. Many of today’s mammography filter applications leverage rhodium sheets of certain key qualities. Gold and platinum alloys in patient implants promise key breakthrough benefits and improvements for procedures such as magnetic resonance imaging (MRI).

Metals and MRI historically haven’t mixed well. The induced currents and heating from radio frequency (RF) magnetic fields related to some metals can harm patients. In addition, the images captured in MRIs can suffer from severe distortion and degradation when performed on patients with some metallic implants. Given the healthcare industry’s increased reliance on various forms of such implants, this is no small problem for a growing portion of the world’s population and their care providers.

However, the magnetic susceptibility and hardness of certain gold and platinum alloys have shown promise in terms of being used in artifact-free devices for biomedical applications. Consequently, research and development are vigorous across metals, devices, and procedures to boost the applicability of MRIs.

Radiopacity

Radiopaque properties vary widely among the different precious metals, and this is a huge factor in their viability as components of electrodes, sensors, and other devices that must be visible under X-ray imaging.

For example, radiopacity is one of the key factors making platinum alloy rings an increasingly common choice for marker bands in most catheters and stents. For the same reason, platinum wires have grown essential for the medical industry’s guidewires, embolic coils, and flow diverter stents. In more and more applications where the precise placement of devices in the body is of utmost importance, devices based on precious metals have grown more prominent because of their superior radiopaque properties.

However, it’s crucial the metals and alloys for these components and materials are produced at a four nines purity level (99.99%). Impurities in the metals and alloys can yield a variety of poor results, including issues with visibility under X-ray, device malfunctions, patient discomfort, and decreases in longevity and reliability.

Additional considerations

Controlling all operations across the rollout of precious metals – from bullion procurement to material processing, manufacturing, sales, and recycling – is key to delivering on device manufacturers’ critical requirements around a metal’s biocompatibility, radiopacity, purity, and alloy composition. It’s not uncommon for one or more of those processes to be outsourced in the development of some alloys, so device manufacturers increasingly demand meticulous recordkeeping around the origin and refinement of precious metals for their components and materials.

The precious metals industry is adapting to meet the medical device industry’s needs. ISO 13485, Medical devices – Quality management systems – Requirements for regulatory purposes, for example, is a crucial standard in the space, defining a widely cited framework designed to contribute to the consistent design, development, production, and delivery of medical devices that are safe for their specified purposes.

New customer requests take shape for particular mechanical properties (bendability, elongation, etc.) in metal wires, rods, rings, tubes, sheets, foil, and more, and drive innovation in alloys and processes. Though the time to achieve clinical trials and regulatory approval is lengthy, this innovation in the precious metals industry is already redefining imaginations across the medical device industry in terms of how the advances ultimately could contribute to procedures which extend patient quality and longevity of life. How might forthcoming improvements enable reductions in recovery time and burden on patients and increased success rates of treatments? Could they open new possibilities for treatment of patients conventionally believed to be too weak or old for certain surgical procedures? As the healthcare industry continues its shift toward more minimally and non-invasive procedures and remote, long-term patient monitoring, key unique properties of precious metals and ongoing innovation in their development stand to expand their role across the gamut of medical devices.

TANAKA Precious Metal Technologies
https://tanaka-preciousmetals.com

About the authors: Kunihiro Shima is head manager of R&D at the Isehara plant in Japan and has worked in the field of technology since joining TANAKA Precious Metal Technologies in 1995. He has been in the medical device field since 2010 and has developed several new precious metal alloys. Yusuke Minagawa is section manager of the sales department with TANAKA Precious Metal Technologies in charge of the hard disk field and the single crystal field. He has been the head of sales in the medical device sector since 2022. Both can be reached at tki-usa@ml.tanaka.jp.