The Project: Specify a polymer for high performance in a range of devices, diagnostic equipment, and packaging.
The Solution: Use COC in products for hospitals, medical laboratories, and other critical settings.
LabCD system from Tecan Group Ltd., a disposable CD-sized disk made from COC, performs 48 drug assays simultaneously.
Thomas Petzel and Bernd Sparenberg can be reached at Ticona Engineering Polymers, 8040 Dixie Hwy., Florence, KY 41042 or 800-833-4882. Ticona uses advanced polymer technology to produce high-performance plastic materials for a wide spectrum of applications. Petzel is the global marketing manager for injection molding; Sparenberg, who has a diploma in polymer engineering from Germany’s University of Applied Science, is the global marketing manager for packaging and film.
By Thomas Petzel and Bernd Sparenberg
Medical designers are increasingly turning to a new polymer, cyclic olefin copolymer (COC), for high performance in devices, diagnostic equipment, and packaging. The plastic is proving to be a versatile material that works as well in prefilled syringes and drug blister packaging as in microtiter plates and microfluidic assemblies.
COC’s attributes, which are outlined in Table 1, provide substantial room for innovation and cost savings. It has excellent optical clarity and a high barrier to water vapor. It molds fine features with great fidelity, withstands all common sterilization methods, and resists hydrolysis and a wide range of chemicals.
It also has good heat resistance, mechanical properties, hardness, dimensional stability, and electrical insulating properties. Because it is very low in extractables and has excellent in-vivo and in-vitro biocompatibility, it meets USP Class VI and ISO 10993 requirements and has received FDA Drug and Device Master File numbers.
In addition, COC offers many benefits in use. It reduces breakage in devices and packaging compared to glass, extends medication shelf life, allows diagnostic readings at UV wavelengths, and enables smaller and faster diagnostic equipment. Following is a summary of nine ways Ticona’s Topas COC has been used in medical applications in just the last year or so.
1. COC is serving diagnostic and device producers in many ways. A microfluidic platform designed and made by the Tecan Group Ltd. is a good example of what this material can do. This disposable CD-sized disk performs 48 drug-screening assays at once. As the disk spins, test compounds and reactants travel outward through channels having dimensions as small as 50 micrometers. Reactions occur in the channels, which end in detection cuvettes where the reaction products are measured by light detection techniques. COC was chosen in part because of its low autofluorescence and because it forms the minute channels with great accuracy and resists the organic compounds used in the assays.
2. Light transmission has been key in other applications. One concerned shatter-resistant diagnostic tubes that replaced glass in critical tuberculosis testing. Becton Dickinson and Co. selected COC over polycarbonate to build a higher moisture barrier and extend the nutrient media’s shelf life to a year or more. The tube had to transmit light at 365 nm—the wavelength at which bacteria fluoresce after incubation. It also had to be steam sterilizable and inert to the bacteria and silicone gel that affixes the reagent in the test tube.
3. In another application that involved light transmission, especially in the near UV range, COC replaced expensive and fragile quartz glass in 96- and 384-well microtiter plates. The plates, which are used for high-throughput screening, are made by Greiner Bio-One International AG. Their optical windows allow them to measure DNA and protein concentrations at 260 and 280 nm, respectively.
TopPac prefillable syringes by Schott Pharmaceutical Packaging, shown undergoing pressure testing, are molded of COC.
4. Although medical devices can place strong demands on plastics, COC is also finding its place in this arena. When Boston Scientific Corp. redesigned its single-use Ultrasonic Imaging Catheter, it chose COC for the manifold that ties key elements together rather than the urethanes, nylons, and other polyolefins it had considered. Of these materials, COC was the only stiff and strong medical material that would not damage the insert-molded lumen tube. The COC part consolidated five nylon elements into one, reducing cost 80 percent in the process. It also allowed for e-beam sterilization, and its low coefficient of friction lets the guide wire pass through easily.
5. Another application involved a device that mixes and applies polymethyl-methacrylate bone cement during surgery. The manufacturer, Stryker Instruments, chose COC for its clarity and strength and because, unlike other clear resins, it does not react with the adhesive.
6. Given its transparency, low moisture permeability, stiffness, low weight, chemical resistance, and lack of halogens, COC is also finding increasing use packaging dry and liquid medications and medical devices. In pharmaceutical primary packaging, Schott Pharmaceutical Packaging selected COC for its TopPac prefillable syringes. These are molded in sterile facilities and then sterilized and sent to pharmaceutical companies for filling. Since they are sterile, the syringes eliminate the cost and time involved in washing and sterilization before filling as is needed with glass. The syringes keep drugs safe to use for several years.
7. In another primary package, COC forms the moisture barrier layer in the multi-layer, injection-blow-molded plastic bottles and vials Owens-Illinois developed for drugs, diluents, and other pharmaceutical products. These distinctive 3- to 250-cc bottles are a shatter-resistant alternative to Type 1 pharmaceutical glass. Unlike glass, they contain no traces of metals or free alkali-oxides and do not chip or craze in production.
8. COC has become an accepted barrier in multilayer drug blister packs because it is transparent and relatively impermeable to water vapor. COC-based films thermoform much like those based on polyvinyl chloride-based (PVC), the most common blister pack material, but have many times PVC’s water vapor barrier. A good example is the Actonel once-a-week tablet blister card from Procter & Gamble Pharmaceuticals Inc., which uses a film having 30µ polypropylene outer layers and a 240µ COC core. This film-drug combination received FDA New Drug Application approval.9. A variety of evaluations demonstrate COC’s effectiveness as a blister film. One study done on formed blisters by Tekni-Plex, a major packaging film supplier, found that COC-based films (COC/PCTFE) give equal or better moisture protection than commonly used PVC-based films having barrier layers of polyvinylidene chloride (PVDC) or polychlorotrifluoroethylene (PCTFE). Another study by four drug companies looked at blister pack permeation for various films (PVC, PET, PP, PVC/PVDC, and COC) at intervals to 196 days. Measurements were done at 25°C and 60 percent relative humidity and either 40°C and 75 percent RH or 38°C and 90 percent RH. COC had the lowest water vapor transmission under stress-test conditions. In a recent development, a Topas COC formulation was introduced that withstands steam sterilization at 121°C for 20 minutes without distortion. Blister packs using this formulation can be formed into blisters, filled, and then steam sterilized without harming the dimensional stability and integrity of the blister.
In conclusion, COC is fast becoming a staple in medical device, equipment, and package design because it offers a wealth of desirable properties from clarity, stiffness, biocompatibility, and dimensional stability to moisture barrier, moldability, and heat and chemical resistance. These properties have opened doors to applications for COC that let manufacturers gain the performance they need in products for hospitals, medical laboratories, doctor offices, and other critical settings.
For additional information on the products and technologies discussed in this article, see Medical Design Technology online at www.mdtmag.com and the following websites:
• Ticona at www.ticona.com
• Tecan Group at www.tecan.com
• Becton Dickinson at www.bd.com
• Greiner Bio-One at www.gbo.com
• Boston Scientific at www.bostonscientific.com
• Stryker Instruments at www.strykercorp.com
• Schott at www.schott.com
• Owens-Illinois at www.o-i.com
• Procter & Gamble at www.pg.com
• Tekni-Plex at www.tekni-plex.com