Bioabsorbable sutures made of glycolide/lactide polymers, first developed in the 1970s, are strong and flexible enough to hold tissue together to promote healing.
But unlike synthetic sutures which stay in the patient long after a wound has healed, bioabsorbable sutures do not create a long-term risk of foreign-body reactions or require a second intervention to remove.
Johnson & Johnson MedTech’s Ethicon, Medtronic, Braun, Smith + Nephew and other medtech developers offer a variety of bioabsorbable sutures. Ethicon, Medtronic, Gore, Allergan, and Bard are among the makers of bioabsorbable surgical mesh.
Bioabsorbable materials have also allowed the development of devices that must be rigid when they are initially implanted, but become flexible as the natural tissue heals around them.
Elixir’s Dynamx bioadaptor is a drug-eluting stent with both metal and biodegradable elements. When it is first implanted, the scaffold is “locked” to establish maximum flow lumen. As the bioabsorbable parts disappear, the structure is “unlocked” to allow the vessel to maintain pulsatility and adaptive flow volume.
Bioabsorbable polymer materials can also create a scaffold to promote the regeneration of the patient’s own cells into new tissue, such as a living, growing heart valve that replaces a defective valve.
Bioabsorbability can also require a compromise on strength or weight.
In 2017, Abbott pulled its much-hyped Absorb BVS poly L-lactide coronary stent off the market after it failed to find a profitable niche in the market. Long-term studies showed Absorb BVS did not improve long-term outcomes compared to drug-eluting metal stents.
To provide enough radial strength to open a vessel, the Absorb BVS struts had to be thicker than that of a comparable metal drug-eluting stent. Investigators hypothesized that the thicker struts made it harder to deploy and could cause blood-flow alterations and thrombogenicity, especially when the stent was malapposed in the vessel.
Elixir Medical, REVA Medical, Biotronik and Amaranth Medical are among the companies that developed stents made entirely of bioabsorbable materials for the European market in the 2010s.
“[But] after the initial excessive enthusiasm around BVS stemming from the dream of disappearing stents, clinical trials brought a great disillusionment,” according to a review by Mateusz Jezewski, et al, in the 2019 Journal of Clinical Medicine.
Abbott won FDA Approval in April 2024 for the Esprit BTK, an everolimus-eluting, PLLA, peripheral stent to treat chronic limb-threatening ischemia.
However, drug-eluting coronary stent innovation has mostly shifted to metal stents eluting their anti-restenotic drug from a bioabsorbable coating.
Histological data shows that the polymer that binds the drug to the stent is the main cause of inflammation in vessels treated with metal drug-eluting stents. Metal stents with a bioabsorbable polymer coating can maintain radial strength without inhibiting healing in the vessel wall.
Boston Scientific’s Synergy everolimus-eluting stent is coated with Synchrony, the company’s name for a four micrometer-thick layer of poly(DL-lactide-co-glycolide) (PLGA). Each square millimeter holds 1 microgram of everolimus. As the polymer degrades, it releases the drug into the vessel wall to prevent hyperproliferation.
Read the rest of our guide to bioabsorbable polymers for implantable medical devices — including different polymers, applications and challenges — at Medical Design & Outsourcing.
