Degradation Properties of Bioresorbable Material Candidates for Congenital Heart Defect Repair

Abstract

The goal of this project is to investigate the use of bioresorbable materials for congenital heart defect repair. This investigation focused on the in vitro degradation over eight weeks of several biodegradable polymers including: Poly (L-lactide) or PLLA, 70:30 Poly (L-lactide)-Polycaprolactone or PLLA/PCL and Polyglycolide or PGA. Since surface area can affect degradation rates several morphologies of these polymers were included in the study such as knits, films, felts, electrospun materials and sponges. The degradation was characterized by: tensile testing, scanning electron microscope (SEM) visualization, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). Results of these tests do not directly provide recommendation for specific materials for use as implantable, bioresorbable materials but they do confirm that the combination of chemical composition and material morphology significantly affect the degradation rate as measured by changes in molecular weight with time. This finding supports the possibility of fine tuning manufacturing processes of these materials to obtain a specific degradation profile. PLLA film material 3 was the only material tested that maintained its peak stress and peak strain behavior over the 8 week degradation time period. This does not necessarily rule out the other materials as long as they maintain mechanical integrity over the required time period. In addition, the changes in molecular weight (but not stress and strain behavior) over time were significantly affected by the type of degradation environment the material was placed in, static vs. agitated or dynamic. The importance of the degradation rate and mechanism for this application is extremely important so the inclusion of some form of agitation in future degradation experiments is recommended. Finally, the degradation environment in this experiment was relatively inert and testing with digestive enzymes or other blood components is also recommended.