Biomedical Textiles in Implantable Medical Devices

By Stephanie Lietz, Development Engineer, Secant Medical LLC

Because material selection intersects the physical, chemical and biological sciences, a multi-disciplinary team of engineers from each of these areas should be involved when evaluating device design and manufacturing options. Although medical device engineers have been using textile structures for decades, their complexity is increasing as biomaterial and fabric-forming options become more abundant. Some well-known examples include woven 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 the attention of device engineers and enabled them to achieve unique results unattainable through the use of more rigid structures. As a result, device engineers are starting to realize the importance of defining the form and function of the end device by initially making an informed decision of the biomaterials that affect the component structure design and the development process.

Known Biocompatible Materials

Biomedical textile structures consist of an array of biocompatible materials, including polymers and metals ranging in dimensions, mechanical and physical properties. The exponential combination of these materials and the textile forming processes results in components with highly customizable material characteristics, performance properties and drug-delivery substrates.

PET and Gold braided tube to be used as a component in an electrically active cardiovascular or neurovascular device.  Source : Secant Medical LLC
PET and Gold braided tube to be used as a component in an electrically active cardiovascular or neurovascular device. Source : Secant Medical LLC
Nitinol circular weft knit mesh can be used for containment (orthopaedics), filtration (cardiovascular) and radial support (delivery system). Source: Secant Medical LLC
Nitinol circular weft knit mesh can be used for containment (orthopaedics), filtration (cardiovascular) and radial support (delivery system). Source: Secant Medical LLC

All of these options allow device engineers to develop ultra-sophisticated implantable devices across a range of medical therapy areas including orthopedics, cardiology, tissue engineering and neurology. Biomaterial selection is a critical factor in engineering a device to function as required for the remainder of the patient’s life or the intended existence of the device.

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

The use of biomaterials that degrade or absorb within the body is increasing in popularity as they are becoming more readily available to device manufacturers.

Common bioabsorbable polymers include but are not limited to PGA (polyglycolides), PLLA (polylacti-des) and their copolymers. These materials are broken down inside the body by different processes of which the most common are hydrolysis and enzymatic degradation.

Bioabsorbable biomaterials have been used in applications associated with nonpermanent or hybrid biologic/synthetic repairs. New textiles constructed from absorbable and bio-active polymers; for example, are ideal in tissue engineering and orthobiologic applications requiring short-term tissue support while the body repairs itself, followed by long-term biologic integration.

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