USA holds 45% share in global medical device market valued at US$200 bln

USA holds a 45% share in the global medical device market currently valued at US$200 bln as per materials and device development discussed at the AMI conference on Medical Grade Polymers 2009. Demand for medical plastics is expected to reach US$6.55 bln in the US in 2012. Biodegradable/bioabsorbable materials are increasing in usage, but can be difficult to process. Markets are growing in East Europe, Brazil, Russia, India and China, according to the consultant Len Czuba. The Middle East and Africa have potential for growth, but there are limitations of infrastructure and political instability. he FDA has regulated medical devices in USA since 1976 and its standards are recognised worldwide. The process is risk and data-based; benefit must outweigh risk. Approvals include good manufacturing practice and control of materials supplies to ensure consistent products. Tests vary with category - implants are highest risk. It is expensive to take a new device to market because of the cost of design and tests to obtain performance data, as well as FDA approval. Polymaterials aims to develop biocompatible and biodegradable polymer scaffolds using rapid tooling techniques to model each implant to the patient. The objective is to form a temporary structure that acts as a mould for a new body-part using host cells. In one study, the company has used biodegradable polyurethane to model an ear cartilage, which was then seeded with cartilage cells. Cordis is involved in developing cardiac stents that also release drugs, using supercritical carbon dioxide to purify poly(lactide-co-glycolide). After loading with the drug, solvent removal cannot use high temperatures or the drug will degrade, so alternative techniques must be employed. The rate of drug release can be controlled by factors such as the crystallinity of the polymer. Smart heart patches are being developed by Dr Wakatsuki of the Medical College of Wisconsin. Cardiomyocytes are mixed with a polymer suspension and moulded into a band shape, then grown with a current applied to simulate the heart beating. This generates a pulsating band of material. Currently there are 20000-40000 US patients waiting for heart transplants and only 2,500 hearts are available each year. Dr Guangyu Lu is the manager for plastics at Teleflex Medical in the critical-care research and development department. He has reviewed the factors in selecting a material from physicochemical properties to cost. Blood contact polymers should not: adsorb protein, release additives into the bloodstream, carry infection, cause clots or cancer, or provoke an immune response or irritation. Coatings are used on medical devices for protection and to improve biocompatibility. Hydrophilic/lubricious polymers include polyvinyl pyrrolidone (PVP), polyethylene oxide (PEO) and polyvinyl alcohol (PVA). Coatings are applied by dip coating, spray coating, brush, roll or blade. Key performance measures include substrate adhesion, durability and mechanical properties, thickness and swelling in body fluids, particle and leachables release, biocompatibility and degradation of implants. Bayer Material Science has been studying polyurethane hydrophilic coatings. An aqueous dispersion can be used or a low boiling solvent, permitting low temperature or ambient curing. The resulting film has extensive entanglement during curing and gives a uniform, transparent, insoluble film that does not require external crosslinking. The coating has been tested for biocompatibility. Ciba Expert Services has recently evaluated a surgical mask containing antimicrobials in the polymer (silver/zinc or triclosan). Tests were developed to simulate breathing through the mask and exposure to saliva, and analytical techniques were honed to detect the key components. Inhalation exposure of 10 hours or leaching exposure to 10 masks gave acceptable safety margins for exposure to triclosan, silver and zinc. Rubber is a key component in the pharmaceutical industry, including seals for many vials and lids. Momentive Performance Materials has an antimicrobial silicone. Silicones comprise 3-5% of the US$20 bln of medical polymers and are used in applications varying from catheters to surgical instruments. Silver ions are incorporated, which are toxic to the bacteria, by destabilising the cell membrane, deactivating sulphur-containing proteins and blocking oxygen-transport enzymes. Teknor Apex has developed medical thermoplastic elastomers: these are easy to process, approach the clarity of PVC, retain natural colour on gamma sterilisation and have lower specific gravity (lighter weight parts). The cost is higher, but less material is used by weight and TPE is very good in over-moulding. The company also supplies flexible PVC and is examining alternative plasticisers in PVC.