Study on in Vitro Degradation of Sutures for Decomposable Esophageal Stent

Abstract

PLLA and PGLA sutures for decomposable esophageal stent were investigated in phosphate buffer solution (PBS) (pH=7.4) at 37°C for period of 8 weeks. The in vitro degradation was studied by determining the change of weight loss, pH value, intrinsic viscosity, tensile strength, orientation degree, degree of crystallinity, melting point and surface morphology of the suture samples. The results showed that all properties of PLLA sutures had no obvious changes, however, the properties of PGLA sutures all changed significantly. The pH value, intrinsic viscosity, tensile strength, orientation degree and degree of crystallinity decreased gradually, and the weight loss of PGLA sutures increased with the degradation time. At 6^th week, tensile strength of PGLA sutures nearly reached zero, and weight loss approached to 70% at 8^th week. The results of DSC showed that melting point of crystalline region of PGLA sutures substantially remained unchanged and melting heat enthalpy increased gradually during in vitro degradation, and the new ordered regions appeared in the amorphous area. The results of SEM showed that surface coating of PGLA sutures spalled initially, and then the sutures occured transverse rupture. Therefore PGLA suture is suitable to prepare decomposable esophageal stent to expand benign esophageal stenosis or stricture, but stent prepared by PLLA suture is not appropriate for treatment of benign esophageal stenosis because it is decomposed for more than 2 months.