Silicone Materials for Long-term Medical Implants: Innovate for the Future

By Feifei Lin, Ph.D., Business Development Manager, Healthcare, Elkem Silicones USA Corp.

With the growth of the aging population, the number of age-related diseases has increased. Every year millions of patients sustained or improved their lives through surgical procedures involving implanted devices. Medical implants such as orthopedics, pacemakers, cardiovascular stents, defibrillators, neural prosthetics or combinational devices like drug-eluting stents have become an indispensable part of modern medicine.

Long-term implantable devices used to improve and sustain life are highly regulated by regulatory bodies around the world to ensure safety and efficacy. Raw materials supplied to medical implants are subjected to the qualification of the devices makers.

Silicone elastomer advantages

Primarily due to the stability of the Si-O-Si bond, silicone elastomers are more suitable for medical implants than carbon-based plastics and rubber in many aspects:

• Unsurpassed biocompatibility and hypoallergenic
• Chemically inert, resistant to oil, solvent and stain
• Bacterial resistant, easy to clean and sterilize
• Long shelf life, maintain performance and integrity under harsh conditions, such as -80C to 300C
• Dielectric with superior insulating properties

Because silicone elastomers have these superior characteristics, silicones have been used in long-term implants for decades. The first published report of silicone elastomer for long term implantation was in 1946 by Dr. Franklin H Lahey, for bile duct repair[1].  By the late 1960s, the medical-grade silicone elastomer had found its way into many long-term implants such as joint arthroplasty, catheters, drains, and hydrocephalus shunts. For over half a century, silicone elastomers have proven to be a safe material that enables millions of patients to overcome debilitating conditions.

Today, as the market demands more efficient and effective care, long-term implantable devices are undergoing dramatic transformations due to advancement in the tech industry. The implants are becoming valuable biomedical control units for monitoring and responding on demand via wireless communication. Devices are getting smaller and are being integrated into electronics which require higher material performance to meet the requirements for integrity and durability; the integration of devices with Internet of Things (IOT) requires lower temperature fabrication.

With the future in mind, Elkem Silicones offers full lines of high-performance Silbione® Biomedical LSRs Silbione® Biomedical HCRs for LTI and drug delivery to meet the challenges of the industry. These offerings are based on the platinum-addition cure system and offer a full range of low to high durometer, higher physical properties, lot-to-lot consistency, and easy mold release.

Elkem Silicones has made significant investment in our manufacturing facility, quality system, and regulatory support to ensure we meet or exceed the standard for long-term implantable materials. Our state-of-the-art manufacturing site in York, SC is ISO 9001 certified with a certified ISO class 8 manufacturing environment and an ISO class 7 packaging environment. Material attestations, toxicology summaries, biocompatibility, MAF and DMF, are available upon request. Our on-staff toxicologists are available to provide regulatory support for these materials.

Elkem Silicones is advancing a robust innovation portfolio, covering high-performance silicone materials and process technologies that enable the future medical devices. In the upcoming MDM Minneapolis, Elkem Silicones will be launching a long term implantable grade, high performance, one-part, tin-free, ambient cure adhesive. This adhesive can bond to different surfaces such as silicone elastomers, polyurethane, polyester, aluminum, and titanium, etc. It offers significant productivity improvement and simplification in the manufacturing process because of fast cure without the need for heating and humidity. It is the first tin-free long-term implantable silicone adhesive in the market.

We have successfully demonstrated 3D printing with our LSRs, which not only enables rapid prototyping but also introduces the possibility of enhancing device physical properties through design. Unlike conventional injection molding, 3D printing LSRs makes it possible to print hollow scaffolds to increase elasticity, strength and decrease weight per part. Recently, Elkem Silicones launched the next generation LSR (liquid silicone rubber), LSR SELECT™, a patented, advanced system of LSR materials and dosing capabilities. This proven system gives you CONTROL to optimize your cure kinetics improving productivity and flexibility to achieve your precise results. In addition to controlling your cure profile, now you can create a repeatable, unique durometer blend. With this technology it is possible to over mold onto temperature sensitive components such as sensors or substrates, meeting the challenges of manufacture combinational drug delivery devices with heat sensitive active pharmaceutical ingredients.

Elkem is proud to be part of the long-term implantable material suppliers. Not only do we offer these materials, but also innovative solutions, expertise, and services to device makers, designers and fabricators. Together with our customers, we advance current and future implants to save people and better human lives.

Visit Elkem Silicones website for more product information. (https://silicones.elkem.com/EN/Our_offer/Market_And_Application/Pages/Long-term-medical-implants.aspx)

Contact Feifei.lin@elkem.com for further questions

LINKS:

LSR: https://resources.silicones.elkem.com/asset/29:elkemsiliconeslsrltilinecardna2018
HCR: https://resources.silicones.elkem.com/asset/28:elkemsiliconeshcrltilinecardnajune2018

[1] Biomaterial Science, An introduction to Materials in Medicine, by ELSEVIER ACADEMIC PRESS, 2^nd edition, Chapter 7.19, p. 698, “Medical Application of Silicones”, Andre Colas and Jim Curtis