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The global medical-device market is valued at around USD200bn (GBP122.4bn) and the US accounts for about 45 per cent of this.

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.

Current healthcare trends include minimally invasive surgery: device developments include a silicone-access port for multiple instruments from Covidien; microendoscopes from Biovision Technologies; and remote handgrips from Novare Surgical Systems that simulate real hand feeling.

Biodegradable/bioabsorbable materials are increasing in usage, but can be difficult to process.

Materials and device development were discussed extensively at the AMI conference on Medical Grade Polymers 2009, which took place in the Hilton, Philadelphia, PA.

Demand for medical plastics is expected to reach USD6.55bn in the US in 2012.

The FDA has regulated medical devices in the US 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.

If a new device is a modification of an existing one, then approval is simpler, involving a 510(k) submission; completely new devices must undergo a full premarket approval (PMA) process.

There are currently around 30-50 of these submissions per year, compared with 3-4,000 510(k) applications, according to Laura Byrd, an engineer in the PMA office.

Sometimes applications arrive on pallets in trucks, as the paperwork is comprehensive.

Polymer manufacturers can submit a master file to the FDA and give written approval for manufacturers to access these reports.

Medical Murray is involved in developing and manufacturing new high-tech disposables and implants, and works with companies and physicians.

Tanner Hargens is a biomaterials expert with the company.

Material specification includes mechanical, chemical, biocompatibility, electrical and thermal properties, as well as processability.

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.

The company estimates a cost of around USD150,000 to USD1m and a one- to four-year time frame to take a device through the 510(k) level, and 2.5 to 10 years and USD1-80m for a PMA.

Current projects include a new polyurethane synthetic ear cartilage.

Polymers used in implants include polyethylene, PEEK, silicone, polysulfone, PTFE, polypropylene and polycarbonate, along with the bioabsorbables polylactide (PLA), polyglycolide (PGA) and copolymers of PLA/PGA.

Processing can build in material stresses or knit lines with lower strength and methods such as solvent casting can give issues with solvent removal.

Sterilisation affects materials in different ways depending on the technique, from ethylene oxide and gamma irradiation to autoclave.

The rewards are seeing a device operational and improving the quality of life for patients.

The company 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.

Cell retention can be an issue and is usually improved by modifying the scaffold surface; however in this case a gel composite containing fibrinogen, growth factors, thrombin and calcium chloride was used as a carrier for the cells, giving a high efficiency of seeding.

The scaffold is expected to last for between one and two years.

The company is also looking at scaffolds for bone and fat (for example in breast-tissue replacement).

Dr Vipul Dave at Cordis is involved in developing cardiac stents that also release drugs.

He is 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.

Long-term there is hope of creating healthy cardiac muscle patches to apply to failing hearts, as currently there are 20-40,000 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.

Solvay Advanced Polymers has a range of materials for medical applications, including polycarbonate, polyarylamide, polysulfone, polyphenylsulfone and PEEK.

These have been tested for compatibility with sterilisation methods and disinfectants, including hundreds of repeat cycles of use and cleaning.

The company has introduced the Solviva Biomaterials range, which has the potential for implant use, including PEEK, self-reinforcing polyphenylene, polyphenylsulfone and polysulfone.

Biological safety testing is carried out by NAMSA, based primarily on the ISO 10993 Part 1 standard.

Currently there is blurring between medical and pharmaceutical devices, as more are combined.

First an assessment plan is drawn up, then materials are selected for fitness for purpose, physicochemical and toxicological properties.

Other factors are then considered, such as the manufacturing processes, leachables and degradation products.

Eight principles are applied in all and these will be expanded in the new version of the standard, due for release around March 2010.

Currently tests are being carried out on bioabsorbable polymers to examine decomposition products.

Ciba Expert Services has recently evaluated a surgical mask containing antimicrobials in the polymer (either 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.

Companies such as Helvoet Pharma use halobutyl and other rubbers, minimising leaching of vulcanising components.

Another alternative is to coat rubber with Teflon.

The company has taken a risk-based approach to assess its manufacturing practices based on an FDA report from 2004, ‘Pharmaceutical CGMPS for the 21st Century’; the ISO 15378 standard and ICH Q9 from the European Medicines Agency Inspections (EMEA).

Critical process parameters are closely monitored during manufacturing.

The World Health Organization (WHO) has noted that: ‘The European (EP), Japanese (JP) and Unites States (USP) pharmacopoieas all describe materials of the same type, but there are considerable differences in classification and presentation.’ Michael Eakins specialises in pharmaceutical consultancy and has looked at control of plastics.

For example, in the USP 661, there are specific tests for polyethylene and polypropylene in plastic containers, in the EP 6.0 section 3.1.3 there is an alternative range of tests, with a further set for containers (rather than materials) in JP XV, section 7.02.

This is important for global businesses.

The International Pharmaceutical Aerosol Consortium on Regulation and Science (IPAC-RS) is a global association of companies that manufacture orally inhaled and nasal drug products (OINDP).

Its members include: 3M, Astrazeneca, Chiesi, Abbott, Boerhinger Ingelheim, Mannkind, Glaxosmithkline, Novartis, Pfizer, Schering Plough, Sanofi-Aventis, Teva and Vectura.

There is a materials working group, the aim of which is: ‘To improve materials quality and integrity, and reduce supply-chain problems by optimising control strategies.’ There have been issues due to variation in material composition, processing (or conditions) and finishing.

Patient safety and high quality are top priorities for the OINDP.

Dr Dennis Jenke of Baxter Healthcare is involved with materials in contact with drugs in delivery systems and packaging.

The definition of secondary packaging can become blurred; for example, an overbag is heated in an autoclave oven at 120C in direct contact with the primary bag and volatile substances have the opportunity to migrate between the two.

Both the drug and the packaging need to perform to the required standard, and key factors include: adsorption of drug onto packaging; degradation of drug or packaging, for example leaching of components or environmental stress cracking; change in pH or precipitation; and protection against exposure to light, loss of solvent, water-vapour adsorption or microbial contamination.

Dr Jenke highlighted several cases involving rubber: in one instance a new drug stabiliser caused a vulcanising agent to leach and increased the risk of red cell aplasia; in another instance, BHT leached from a rubber stopper in infusion pumps after the latex was replaced with chlorobutyl rubber.

Resmed makes around six million product units each year worldwide with a turnover of about USD1bn.

The company is looking for confidentiality of intellectual property from its material suppliers, uniform data presentation and consistent polymer to be supplied across the globe.

Expertise in medical injection moulding is supplied by Mack Molding: it works with designers to develop new devices.

Recent projects include a gas-assisted over-moulded handle.

Infection transfer is a big issue in healthcare.

Momentive Performance Materials has an antimicrobial silicone.

Silicones comprise three – five per cent of the USD20bn 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.

PVC has been used in medical applications for decades, but with the phthalate plasticizer controversy, replacement materials have been sought.

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.

The next AMI international conference on medical-grade polymers is planned for 14-15 September 2010 at The Hilton City Avenue, Philadelphia.

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