With every heartbeat blood is carried through the arteries to provide organs with life-sustaining oxygen and nutrients. In patients suffering from diseases such as atherosclerosis, arterial blood flow can be severely restricted, limiting the delivery of oxygen and nutrients. To re-establish blood flow, surgeons may place a stent to mechanically re-expand and hold the damaged artery open. One of the potential complications with stents is that they are typically made of a non-degradable metal, which can lead to an immune response and impair vessel healing. In a recent Nature Materials research paper, biomedical engineers from 480 Biomedical, a Watertown, MA firm, developed a self-expanding and 100% bioresorbable stent as strong as metal.
To design an elastic and bioresorbable stent able to withstand arterial blood pressures, the engineers had to invent a new composite material. Ingeniously, they produced a design made from commonly used FDA approved biomaterials. First, they created a braided stent from poly(L-lactide-co-glycolide) (L-PLGA) fibers in a pattern that allowed bending and provided the underlying stent structure. To introduce elastic recoil strength, the mesh was spray coated with a novel thermoset polymer. After the elastomeric coating cures, it “locks” in the mesh at all points of intersection, and allows the original shape to “spring-back” after deformation. Mechanical tests showed the new composite stents were as strong as metal stent benchmarks and could self-expand to 95% of their original diameter after being compressed inside a catheter.
In vitro mechanical and degradation experiments combined with in vivo preclinical pig and sheep models guided the engineers in optimizing the polymer formulations. The engineers were able to tune the stent materials to find a ‘goldilocks zone’ in terms of elasticity, strength, and the rate of biodegradation. This resulted in excellent stent performance in a long-term sheep model.
This work is exciting because one day these stents may offer better treatment for patients suffering from peripheral artery disease, where conventional stents can fail due to kinking or fracturing. As the stent is biodegradable, drugs aimed at improving healing could potentially be incorporated for controlled local release. The conformal nature of this device makes it, in theory, applicable to a number of soft tissue disease therapies throughout the body.
Likely next steps for 480 Biomedical will include continued tests to compare the new stent against the gold standard in preclinical disease models and eventually move on to human testing.
Study in Nature Materials: The development of bioresorbable composite polymeric implants with high mechanical strength…
Via: 480 Biomedical…