A Biodegradable Slotted Tube Stent Based on Poly(l-lactide) and Poly(4-hydroxybutyrate) for Rapid Balloon-Expansion
Safe vascular stent application requires rapid expansion of the stent to minimize the risk of procedural ischemia. While high expansion speeds can be achieved with metallic stents, they are not necessarily feasible with biodegradable polymeric stents due to the viscoelastic material behavior. This study reports on a novel biodegradable polymer blend material based on poly(l-lactide) (PLLA) and poly(4-hydroxybutyrate) (P4HB), and describes the mechanical properties and in vitro degradation behavior of a balloon-expandable slotted tube stent concept. The stent prototypes with nominal dimensions of 6.0 × 25 mm were manufactured by laser machining of solution cast PLLA/P4HB tubes (I.D. = 2.8 mm, d = 300 μm). The stents were expanded within 1 min by balloon inflation to 8 bar, after 5 min preconditioning in 37 °C water. Recoil and collapse pressure were 4.2% and 1.1 bar, respectively. During in vitro degradation collapse pressure initially increased to a maximum at 4 w and then decreased thereafter. After 48 w, molecular weight was decreased by 82%. In summary, the PLLA/P4HB slotted tube stents allowed for rapid balloon-expansion and exhibited adequate mechanical scaffolding properties suitable for a broad range of vascular and non-vascular applications.
KeywordsPLLA P4HB Recoil Collapse Laser machining Mechanical properties Degradation
The authors wish to express their appreciation to Dipl.-Ing. Peter Behrens and Dr.-Ing. Wolfram Schmidt, Institute for Biomedical Engineering, University of Rostock, for sharing their expertise in stent testing. Dipl.-Ing. Steffen Mews, Institute for Biomedical Engineering, University of Rostock, is gratefully acknowledged for his technical support during the stent degradation study.
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