Study On Totally Bioresorbable Composites As Cardiovascular Stent Material

Coronary stenting is largely used in percutaneous transluminal coronary interventions because of the minimal trauma and outpatient treatment. Bare metal stents present excellent mechanical performance, but may lead to restenosis due to the permanent existence of stents. Therefore, a new generation of stents prepared from biodegradable polymers has received growing attention due to their outstanding biocompatibility, degradability and mechanical properties.In this work, a series of bioresorbable copolymers were prepared by ring-opening polymerization of L-Lactide (L-LA) or DL-Lactide (DL-LA) with 1,3-trimethylene carbonate (TMC), using low toxic zinc lactate as catalyst. Totally bioresorbable composites were prepared by reinforcing the PTMC-LLA copolymer matrix with poly(L-lactide-co-glycolide) (PLGA) short fibers to compensate the strength loss of the copolymers compared to PLLA, a commonly used stent material. The surface of the fibers was previously treated by oxygen plasma, and the composites were heat treated at 100℃under vacuum for 2 h. The various copolymers and composites were characterized by using different analytical techniques such as proton nuclear magnetic resonance ('H NMR), size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), static tensile testing, etc. In-vivo and in-vitro degradation experiments were carried out to assess their degradation behaviors.The composites with plasma-treated-surface fibers exhibit better mechanical strength than the neat copolymers and the composites with untreated fibers. The tensile strength of the composites is very close to that of PLLA. The composites degrade faster than the copolymers due to the faster degradation of PLGA fibers, which is beneficial for the elimination of the stents after service. The in-vivo study shows that PTMC-LLA copolymers exhibit slower degradation rate compared to PLLA and PTMC-DLLA copolymer. Therefore, the composites with PTMC-LLA matrix and PLGA fibers present great potential as cardiovascular stent material due to their great mechanical performance, better flexibility and less crystallinity and less acidic degradation products.