Hydrolytic degradation of porous poly(hydroxybutyrate-co-hydroxyvalerate) scaffolds manufactured using selective laser sintering

Abstract

The long-term hydrolytic degradation of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) bone scaffolds manufactured using Selective Laser Sintering (SLS) process have yet to be explored. In this study, SLS PHBV scaffolds were incubated in phosphate-buffered saline (PBS) solution for up to 20 weeks. The result showed that degradation of the PHBV scaffolds occurred predominantly by bulk degradation. With increasing incubation time, the molecular weight and compressive stiffness of the scaffolds reduced while their crystallinity increased. In the first 8 weeks, the weight loss of the scaffolds was insignificant, indicating very limited amount of soluble product was produced by the hydrolysis process. Weight loss started to occur from Week 8; the average weight loss per fortnight was minimal and in the range of 0.33-0.51 %. The pristine PHBV scaffolds had a highly crystalline surface layer with low concentration of the hydrophilic carboxylic acid (COOH) end-groups. The concentration of COOH groups on the scaffold surface increased initially upon immersion in PBS due to the preferential chain rearrangement to expose hydrophilic segments. During immersion surface hydrolysis proceeded and the quantity of COOH groups declined from Week 2 to 6 due to erosion of the surface layer.