Over the past few decades, the landscape of materials used in implantable medical devices has changed. Permanent implants have fallen out of favor due to their biocompatibility issues over the long term, and bioresorbable materials have taken their place in many different applications. Doctors prefer to avoid situations where revision surgeries are necessary, and patients are excited at the “regenerative” solutions.

What’s defined as a bioresorbable material? Polymers with the ability to break down within the body have been defined using many buzzwords including bio-absorbable, bio-degradable, and dissolvable – the list goes on.

To keep things simple, we have chosen to term these materials as bioresorbable. The bioresorption of these polymers occur either enzymatically or hydrolytically. You might recall from your biology classes that your body produces and consumes a wide variety of natural polymers such as proteins, amino acids, and polysaccharides like glucose, sucrose, etc. These polymers all undergo a process in the body that breaks them down using enzymes.

Synthetic polymers such as poly-lactides, poly-caprolactones, poly-glycolides, etc. are all primarily broken down via hydrolytic reactions. Many new types and combinations are being explored in a variety of applications. The physical properties of these polymers, such as flexibility, strength, shape and degradation rates, can all be customized through adjustments in the chemistry of the material and the way they are processed.

Once a recipe for a particular synthetic polymer has been developed, it is easy to scale up the production and have consistent reproducibility. In general, applications that require batch-to-batch uniformity and patient-to-patient implant response will find better solutions with synthetic polymers.

At Poly-Med, we specialize in the development and production of medical grade synthetic bioresorbable polymers. Our team has the capability of providing customized solutions using our portfolio of polymers. With a design process that has been refined for decades, Poly-Med produces consistent results that help innovative organizations accelerate the delivery of their products.

We welcome you to contact us for more information, and look forward to forming successful partnerships.

Synthetic polymer-based textiles have been used for medical applications for decades and represent a staple production technique on par with injection molding and machining. Textiles are provided in a number of techniques, such as knits, braids, woven fabrics, monofilaments, films, and various nonwovens. For many medical applications, however, traditional textiles do not meet performance requirements. Melt blown nonwovens, for example, require heating a polymer to high temperatures which can damage the polymer chains and prevent inclusion of heat sensitive drugs. A solution to this issue, first developed in the early 1900s but which has gained considerable interest in the last several years, is a dry-spinning technique called electrospinning.

Electrospinning (typically) involves the injection of a polymer solution into a high voltage static electric field, which draws the injection stream into fibers with very small diameters on the scale of nanometers (10-9 meters) to micrometers (10-6 meters), which is similar to human cell types such as fibroblasts. The resulting fabric can be up to 90% free volume with low pore size and high surface area. The small fiber dimensions also create unique mechanical behavior.

Textiles created from electrospinning have potential medical applications for active and directed wound healing applications, stent grafts, surgical mesh, adhesion prevention, and tissue separation. Also, because the process is most often performed at room temperature, drugs and other heat sensitive materials can be included in the spinning solution and dispersed throughout the fibers.

Poly-Med has been creating electrospun textiles for various medical applications for more than 10 years, and has developed the equipment and in-house expertise to meet the most stringent product demands. We have produced fabrics utilizing hazardous organic solvents such as hexafluoroisopropanol (HFIP) and many polymers including polyglycolide, polylactide, polydioxanone, polycaprolactone, and various copolymers.

To support our customers, Poly-Med has scaled our capabilities to include tight environmental controls and significant production throughput. This coupled with our ISO 13485/9001 quality system and vertically integrated contract development and manufacturing services, gives our partners the advantage of unique materials and processes created in a compliant atmosphere.

Let us know how our experience and capabilities can help you develop your product. Please contact us or visit us at www.poly-med.com

M. Scott Taylor, Ph.D.

A wide variety of implantable medical devices are created using plastic components, which involve the use of more “traditional” polymers such as polypropylene and polyethylene terephthalate (PET) as well as advanced and tailored materials like polyetheretherkeytone (PEEK) and polyvinylidene fluoride (PVFD). A segment of the implantable device market utilizes an increasingly specialized polymer subset that is designed to degrade in the body after the functional life of the implant, known as bioresorbable polymers. Devices created from bioresorbable components include sutures, surgical mesh, staples, clips, pins, bone screws, and a host of other devices. It is important to note that bioresorbable polymers are intentionally designed for instability and are more expensive than traditional industrial polymers, making a focus on process control an even greater priority.

A common requirement to all of these products is that raw materials (in this case polymers) need to be converted and later stored in some way to create a finished device. While each material has unique process requirements, bioresorbable polymers have very stringent needs for storage and processing to make a device functional.

Common conversion techniques include melt processing, and implantable devices must be supplied sterile, both of which can be detrimental to the performance and storage stability of the product. Bioresorbable polymers degrade due to a number of process-induced factors, primarily including hydrolysis (caused by absorbed moisture), heat and mechanical stress (shear).

Melt extrusion is a very common conversion technique, and is particularly useful in creating fibers, films, tubing, and nonwovens. As the name suggests, you cannot avoid heating the polymer above the melting temperature, imparting significant potential for degradation. Additionally, material is typically metered using a screw, introducing shear forces that can further damage the polymer. This is secondary to moisture, though, and we focus on drying polymers to less than 50ppm before extrusion. Dry, inert gas atmospheres are also utilized to minimize risk of moisture absorption for best results.

While a device is intended to degrade in the body, packaged devices need to remain unaltered through shelf storage. For this, high barrier foil pouches with very low moisture vapor transmission rates (MVTR) are recommended, and devices need to be dried to a very low moisture level and backfilled with a dry, inert gas for a best chance at long term stability. We typically recommend foils with a metal (not metallized plastic) foil layer and total moisture within the device of at least less than 500ppm. Drying is commonly performed using active reduced pressure (vacuum), with or without heat, at well less than 1 Torr. Alternatively, low humidity desiccators may be used. It is important to note that each material and construct dries at different rates, from a few hours to several days, but all absorb moisture to an unstable level in a very short timeframe.

Processing bioresorbable polymers can be a challenge, even to companies with a wealth of experience with engineering plastics. At Poly-Med, we have been processing these materials for almost 20 years and have built a significant capability in processing and preserving bioresorbable materials for maximum utility and stability, as well as assisting clients with building their own in-house capability. If you are designing a device with an absorbable component, let us know if you need help with material or process selection, packaging, drying, stability studies, or analytical support.

For additional information about this topic or other Poly-Med materials and capabilities, visit our solutions page or contact us today!

M. Scott Taylor, PhD

CTO