Düsseldorf, Germany — Nusil LLC presented a new in-situ cure LSR solution for implantable devices at the Compamed medical components fair in Düsseldorf. The Carpinteria, Calif.-based company claims to be the market leader in long-term implantable silicones that are molded and cured outside the body prior to implantation.
Its new solution involves dispensing uncured LSR components into the body via a double cartridge dispenser feeding with disposable syringes in five volume sizes between 5-75 ml.
The components mix with one another as they are injected and then cure at low temperature inside the body. This means implantation is less invasive than conventional pre-formed implants and the resulting implant can be customized to fit its location in the body.
Joel Wiliams, vice president and general manager, said "we can envisage, for example, rapid spinal vertebral repair, the material expanding to encompass available geometries."
The uncured LSR material components can be sterilized together with the dual-barrel cartridge dispenser by ethylene oxide (EtO) as the cartridge seals are permeable to EtO gas. This is the recommended method, as dry heat and autoclaving sterilization damage the packaging, adversely affecting workability, while gamma radiation and electron beam sterilization alternatives increase LSR cross-linking, significantly reducing flexibility.
In contrast, there is only minimal change in LSR key physical properties of rheology (flow), hardness, flexural modulus, cyclic fatigue resistance and cure rate under EtO sterilization.
Williams said Nusil has patented the package dispenser system, not the LSR materials used. He stressed, "Nusil builds its business around customized formulations. It is not a company producing hundreds of tons of product — it is more like batch chemistry. The patent on the dispensing system enables a host of different chemicals to be developed and used."
He also stressed that Nusil's solution is still at an early stage, as "we have got some active projects with a few customers, but it is all pretty new."
"Half of the projects are presently in the U.S.," he said, adding he expects implants to be applied with the new solution during the next three years. "But there are certainly also potentials in cosmetics and structural functional applications," he predicted.
Nusil also presented 12 conventional MED-4900 series LSR grades at Compamed, with Shore A hardnesses between Shore 7-80. The three self-lubrication grades have Shore A35-60 hardness. None of these materials requires post-cure, and they can be cured rapidly at elevated temperatures, typically 138° C.