Absorbable Medical Devices as Implantable Tissue Scaffolds

Bioresorbable Medical Device Overview:

Bioresorbable medical devices are implantable materials designed for a particular treatment and degrade over time once the scaffold is no longer necessary. Bioresorbable polymer materials may be synthetic or naturally-derived, exhibit high biocompatibility, and may degrade through mechanisms including but not limited to bulk hydrolysis, surface erosion, or enzymatic degradation depending on the material. Typically, degradable medical devices are produced with off-the-shelf traditional homopolymers or random co-polymers such polyglycolide (PGA), polylactide acid (PLA), polydioxanone (PDO), polycaprolactone (PCL), poly(lactide-co-glycolide) (PLGA), or poly(L-lactide-co-ε-caprolactone) (PLCL). Although readily available from multiple bioresorbable polymer suppliers, often these materials lack ideal characteristics for implantable medical devices due to their mechanical properties or degradation profiles for intended applications. In addition to manufacturing bioresorbable polymers in-house, Poly-Med can also transform off-the-shelf polymers and co-polymers, as well as our high-performance polymers through several manufacturing processes including but not limited to extrusion, braiding, knitting, electrospinning, and 3D printing. Poly-Med has extensive experience working with injection molding vendors that have successfully used our performance bioresorbable polymer resins.

Figure 1: Poly-Med offers a catalog bioresorbable polymers with different architectures, mechanical properties, and degradation profiles that may be selected based on a specific bioresorbable medical device application. A) Off-the-shelf bioresorbable polymers are typically homopolymers or random co-polymers that have non-segmented degradation profiles, such as Poly-Med’s Max-Prene® 955 PGLA co-polymer (95% glycolide / 5% lactide) and Dioxaprene® 100M polydioxanone homopolymer. B) Poly-Med’s Glycoprene® and Strataprene® polymer series exhibit polyaxial architectures and segmented degradation profiles. Here, flexible trimethylene carbonate (TMC) substituents are located within the polymer core and rigid glycolide/lactide constituents are located within the arms of the polymer creating a triadic design. C) Poly-Med’s Lactoprene® polymer series exhibit linear block co-polymer architectures with segmented degradation.

Bioresorbable Fibers, Yarns, & Films:

Bioresorbable polymer materials may be extruded into a variety of formats that include but are not limited to fibers, yarns, and films. In addition to typical mechanical requirements for fibers & yarns, extruded resorbable materials require careful material characterization including but not limited to molecular weight (often measured via inherent viscosity), residual monomer, identity testing, and moisture content. Melt extrusion requires a careful balance three (3) main process settings of 1) moisture management, 2) optimizing the polymer melt profile, and 3) the appropriate mechanical shear. Bioresorbable monofilament fibers are commonly used for in mesh & graft implants or braided into hollow tube structures, whereas multifilament yarns are commonly used in braided suture materials in addition to mesh & graft implants. These extruded bioresorbable polymer-based materials may be utilized at Poly-Med for downstream biomedical textile manufacturing within our vertically integrated supply chain or may handed off to an additional partner for processing outside of Poly-Med’s core service offerings.

Figure 2: Example monofilament extrusion line at Poly-Med, Inc.

Bioresorbable Biomedical Textiles:

Biomedical textiles are fiber-based medical devices that can be implanted in patients to restore tissue properties, provide mechanical support, as well as facilitate the healing process for a variety of indications. Textile-based implantable medical devices include but are not limited to sutures, meshes, vascular grafts, and heart valves. Although not melt-based processes, care still must be taken to limit moisture exposure of bioresorbable materials through the general production cycle as well as through heat setting of fabric materials. Poly-Med offers custom warp & weft knitting, and braiding for fiber-based textile applications as well as electrospinning for manufacturing non-woven fabric that may utilized as tissue scaffolds or wound matrices. These biomedical textiles may used as components for a final implantable medical device or as components in more complex constructs.

Figure 3: Examples of warp knitted absorbable mesh constructions.

Figure 4: Poly-Med’s advanced absorbable materials can be electrospun into nanofiber sheets (Panels A and B) that may be incorporated with an active pharmaceutical ingredient (API) of interest.

Bioresorbable 3D Printed Implants:

3D printing (additive manufacturing) processes produce three-dimensional parts through addition of material layer by layer. 3D printing technologies relevant to the bioresorbable polymer market include fused deposition modeling (FDM), selective laser sintering (SLS), and resin-based methods such as stereolithography (SLA) & dynamic light processing (DLP). FDM produces parts by melting a continuous thermoplastic filament via extrusion through a heated printer head, whereas SLA produces parts in a layer-by-layer fashion through a photopolymerization process where a UV laser is focused on a photopolymer vat. Poly-Med offers off-the-shelf 1.75 mm monofilament FDM filaments in fifty (50) grams quantities for developing your next prototype at your facility, in addition to offering design consulting and manufacturing services for 3D printing at Poly-Med’s facilities. Recently, Poly-Med has launched our first-in-class short-acting Photoset® bioresorbable resin for SLA and DLP printing applications. Our Photoset® resin can be customized to meet most mechanical and degradation design requirements for your next bioresorbable medical device implant. Poly-Med also offers design consulting and manufacturing services for developing Photoset® resin-based medical devices.

Figure 5: Example of model part printed with Poly-Med’s Photoset® bioabsorbable resin. The Photoset® resin is available in three (3) formulations with varying degradation profiles and tensile moduli.

Bioresorbable Injection Molded Implants:

Injection molding is a common approach for manufacturing bioresorbable medical devices as this technique is often the most cost-effective for solid devices to be sold in large volumes. Poly-Med’s bioresorbable polymer catalog may be processed via injection molding, although Poly-Med does not currently offer these services in-house. Poly-Med has extensive experience working with injection molding vendors that possess the ability to process bioresorbable materials into high-quality parts while maintaining material integrity. Our team would be happy to provide recommended vendors for processing our high-performance bioresorbable Glycoprene®, Strataprene®, and Lactoprene® polymer series.

Bioresorbable Medical Device Product Development with a Vertically Integrated Partner:

Manufacturing bioabsorbable medical devices is hard. Controlling moisture levels and material degradation through the production cycle requires specialized equipment and process controls to ensure quality of finished devices. In contrast to other contract manufacturers that produce advanced bioresorbable materials, Poly-Med produces polymer, extrudes this material to desired monofilament or multifilament formats, and is able process this material via warp knitting, weft knitting, or braiding processes to produce a custom biomedical textile. Additionally, we can process our bioresorbable polymers into non-woven formats through electrospinning via our state-of-the-art electrospinning facility or 3D print your next prototype & finished bioresorbable medical device. In addition to accessing Poly-Med’s almost thirty (30) years of experience with bioresorbable polymer materials, partnering with Poly-Med simplifies your bioresorbable medical device manufacturing supply chain. Of note, Poly-Med facilities are certified to meet ISO: 13485:2016 standards for quality management of its design, development, and manufacturing of bioresorbable polymers, fibers, sutures, medical textiles, and biomedical products. Contact us to today to begin developing your next generation absorbable product line with a trusted partner for manufacturing advanced bioresorbable medical devices.

Figure 6: Poly-Med offers a catalog of manufacturing approaches for processing bioresorbable polymers that meet a variety of implantable medical device design requirements. Poly-Med can package these bioresorbable components or devices in simple and more complex arrangements that may include final device labeling to be utilized at healthcare providers.