Biocompatability demands steer medical device developments

A taste of what awaits processors at the upcoming Medtec 2007 show next month in Stuttgart, Germany (organized by MPW’s parent, Canon Communications), was offered at the recent Medica/ComPaMED exhibitions.

New trends in nanomedicine highlighted the event held by Messe Düsseldorf, organizer of the upcoming K 2007 show, with plastics the preferred material for many medical devices. In medical engineering, the annual Innovation Monitor report, developed by the Assn. for Electrical, Electronic & Information Technologies (Frankfurt, Germany), says German industry remains in the forefront but adds that Asia is catching up.

Medical developments using existing polymers, refined for medical use, are a noticeable trend. Markus Krieter, manager, medical polycarbonate (PC) business unit at Bayer MaterialScience (BMS; Leverkusen, Germany), says, “Unlike the...electronics sector, the focus in medical technology is not so much on constantly developing new materials as ensuring long-term availability and reliable supply of various materials. It is not so much a question of using completely new materials as of further exploiting the application potential of existing [resins].”

He points to a new technology such as DALI (Direct Adsorption of LIpoproteins), developed by Fresenius Medical Care (Bad Homburg, Germany), to remove harmful substances such as LDL cholesterol from the blood while outside the body. The processor developed the housing using BMS’s Makrolon 2458 PC grade. Krieter says it is fracture resistant, and sufficiently tough and stiff to protect the medical device from rough hospital treatment. Another reason for choosing this grade, which is less expensive than polysulfone, was that it withstands 1 bar pressurized hot-steam sterilization of the DALI adsorber, where temperatures reach 121°C/20 min.

GE Plastics (Bergen op Zoom, Netherlands) demonstrated two grades (1944 and 1914) of Lexan HPM PC that it says reflect the changing needs of the healthcare industry. According to the company, the materials provide improved hemocompatibility in regard to platelet retention, leukocyte and C3a protein activation, and reduced fibrinogen protein surface binding characteristics. These medium- and high-flow materials are said not to compromise existing mechanical properties.

Blood contact with foreign materials such as injection molded medical equipment can trigger platelet response, which is a clotting mechanism. Therefore the polymer selected for a device needs to reduce this activity, which GE Plastics says these grades do.

Thermoplastic elastomer (TPE) producer GLS (McHenry, IL) has come up with a new line of TPE alloys that provide moisture and gas barrier, said to be the only such materials currently on the market. Walter S. Ripple, sales/marketing director, says the line targets medical applications requiring package barrier integrity such as vial stoppers, medical films for IV bags without coextrusion, use of thermoset rubbers, or lamination. The material has a low haze and a Shore A hardness ranging from 40-90.

DIBA Industries (Danbury, CT) demonstrated its 3D thermoformed tubing assemblies for tight-fitting spaces in analytical devices. Available in a wide range of commodity and engineering resins, the tubing prevents kinking and ensures a controlled volume of fluid passing through the tubing, says Antonio Mendes, sales manager.

Offering an advantage to the processor that produces individualized hearing aid shells with an exact fit rather than injection molded, high-volume standardized units, is a development from Electro Optical Systems (EOS; Krailling, Germany). Medical device manufacturer Phonak (Stäfa, Switzerland) is using EOS technology to laser sinter these in nylon 12. Martin Bullemer, EOS key account manager, says processors can offer a more value-added end product and thus expect to charge more for this application than standard-dimension units. Laser sintering offers individualized solutions for other medical applications such as implants, dental restorations, and body-part replacements, says Bullemer.

Polimoon Medical Packaging (Langeskov, Denmark) presented its latest innovation, the Safe-T-Mix connection device, which mixes fluids between vials and IV containers. Codeveloped with a Danish hospital group, the T-shaped piece fits horizontally onto an IV bag. —[email protected]