Although medical device engineers have been utilizingtextile structures for decades, their complexity is increasing as biomaterialand fabric-forming options become more abundant. Some well-known examples includewoven and knit polyester tubes that are used to bypass aneurysms in the aorta,and polypropylene warp knit meshes to repair most hernia types.

These versatile fabric structures have captured theattention of device engineers and enabled them to achieve unique resultsunattainable through the use of more rigid structures. As a result, deviceengineers are starting to realize the importance of defining the form andfunction of the end device by initially making an informed decision of the biomaterialsthat affect the component structure design and the development process.

Known BiocompatibleMaterials

Biomedical textile structures consistof an array of biocompatible materials, including polymers and metals ranging indimensions, mechanical and physical properties. The exponential combination of thesematerials and the textile forming processes results in components with highlycustomizable material characteristics, performance properties and drug deliverysubstrates. All of these options allow device engineers to developultra-sophisticated implantable devices across a range
of medical therapy areasincluding orthopedics, cardiology, tissue engineering and neurology.Biomaterial selection is a critical factor in engineering a device to functionas required for the remainder of the patient's life or the intended existenceof the device.

There are benefits to working withwell-known, established biomaterials such as polyester (polyethylene terephthalate)and polypropylene. Since these materials have been used for decades, there is awealth of information available to engineers to better understand the mechanicaland biological performance indicators to guide them in designing thefunctionality of a new device. Established materials can also offer devicemanufacturers a smoother and faster regulatory approval path due to theirhistorical use in implants.

The use of biomaterials that degradeor absorb within the body is increasing in popularity as they are becoming morereadily available to device manufacturers. Common bioabsorbable polymersinclude but are not limited to PGA (polyglycolides), PLLA (polylactides) andtheir copolymers. These materials are broken down inside the body by differentprocesses of which the most common are hydrolysis and enzymatic degradation.Bioabsorbable biomaterials have been used in applications associated with non-permanentor hybrid biologic/synthetic repairs. New textiles constructed from absorbableand bio-active polymers; for example, are ideal in tissue engineering andorthobiologic applications requiring short-term tissue support while the bodyrepairs itself, followed by long-term biologic integration.

In other medical therapy uses, the enhancedmechanical properties, abrasion resistance, chemical inertness, temperatureresistance and durability are important design criteria for the functionalityof the device. These therapies may require using advanced polymers such as polyetheretherketone(PEEK) and ultra high molecular weight polyethylene (UHMWPE). As thesematerials prove their effectiveness, they continue to attract attention amongbiomedical textile innovators in using these fiber forms to design new textilestructures.

Textile structures can alsoincorporate or be made entirely of metals for several added benefits. Nitinolis a common metal utilized in the medical device industry for its super elasticproperties. Utilizing nitinol within a braided structure provides deviceengineers the benefit of incorporating both the properties of braids and nitinolto allow a shape transformation to occur. The braid can easily be compacteddown to fit into a small cannula, and once placed into position, transform tothe desired shape. Device engineers can also design in all varieties of stainlesssteel, cobalt chromium alloys, and titanium based on their mechanicalproperties and historical use within certain parts of the body. There are alsoother metals that can be utilized for their radio opacity properties that allowthem to be seen under a fluoroscope to provide for easy placement duringimplantation.

New MaterialPossibilities

As biomaterial developers introduce new product grades andenhancements, additional material combinations will be available to fitincreasingly detailed design parameters. Combinations of resorbable andnon-resorbable materials are being used to control device properties over time.Some textile components can now be engineered from materials designed todegrade at varying rates over varying time periods; by synchronizing themodulation of fabric absorption with tissue healing, this multi-phasedstructural degradation promotes a more biologic repair.

With biomedical textiles, "off theshelf" solutions don't work very well. Every device application is uniqueand specialized. Identifying the most appropriate biomaterial andbiomaterial supplier is essential for maximizing the performance of the devicefunction. Likewise, the wide variety of therapeutic areas -- and themechanical and physiologic characteristics desired for the finished device --must be used to guide decisions about textile material composition.

Because material selection intersects the physical, chemical, andbiological sciences, a multi-disciplinary team of engineers from each of theseareas should be involved when evaluating the options, whether on the side
ofthe device manufacturer or the biomedical textile manufacturer (or acombination of both). Collaboration between the device engineers and theirtextile engineering counterparts early in the development process is the mosteffective way of identifying and securing material selection options.

Selection of appropriate biomaterials for use within devicesbenefits device manufacturers in leveraging these materials for theirsubmission to the FDA with less risk of delays in getting their devices tomarket. The combination of established and emerging substrates, along with acarefully structured material selection process, offers an effective pathtoward enhancing the performance of a finished device.

Click here for moreinformation.