A Biodegradable Balloon-expandable Stent for Interventional Applications in the Peripheral Vasculature — In vitro Feasibility

Abstract

Biodegradable polymeric stents represent an attractive approach to overcome the limitations of permanent metallic stents and current drug-eluting stents. The particular appeal of polymeric stents results from their potential for controlled biodegradation and drug incorporation. Recently, we have reported on the development and successful in vivo testing of a PLLA-based anastomotic support stent for surgical use in the porcine aorto-iliac graft model. The present study reports on the adaptation of this stent concept towards interventional application in the peripheral vasculature.

Biodegradable polymeric mini tubes (I.D. = 2.2/2.8 mm, d = 250 µm) were fabricated by solution casting of a high molecular weight polymer blend based on Poly-L-lactide (PLLA). Peripheral stent prototypes (nominal dimensions: 5.0/6.0 × 20 mm) were manufactured from the mini tubes using a CO₂ laser cutting process. The stent prototypes were mounted on 5.0/6.0 × 20 mm angioplasty catheters. In vitro, the prototypes were bench tested regarding expansion behavior, elastic recoil and collapse pressure. Interventional deliverability of the stent systems was tested in a mock vessel setup. Radio-opacity was assessed by fluoroscopy after stent coating with a contrast agent.

All prototypes could be expanded without strut ruptures, and with low elastic recoil. Elastic recoil (3.9 – 4.7 %), foreshortening (2.9 – 3.4 %) and collapse pressure (0.6 – 1.0 bar) of the prototypes were dependent on initial and expanded stent diameter. The stent/catheter systems could be maneuvered at a low force (< 5 N) through the mock setup of a contralateral iliac artery stent delivery. Radio-opacity of the otherwise translucent stent was improved with the application of contrast agent, but remained inferior to the stainless steel control.

The performed in vitro tests indicate the mechanical competence and deliverability of the stent prototypes. Altogether, the results encourage in vivo testing in a porcine interventional endovascular model, such as the renal, iliac or femoral artery.