In Vivo and In Vitro Degradation Studies for Poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyhexanoate) Biopolymer

Studies have shown that the copolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(HB-co-HHx)] possesses favorable mechanical properties for use in medical supplies and products (e.g., sutures, scaffolds, bone plates). One of the major under-addressed issues associated with the use of biodegradable, bio-based PHA polymers in resorbable medical products is the correlation between the mechanical properties and the in vivo material degradation over time. In this study, P(HB-co-17 mol% HHx) matrices were mechanically tested after either incubation in cultures of human embryonic kidney cells (HEK) for in vitro degradation studies for up to 4 weeks, or inserted into Danio rerio (zebrafish) tissues for in vivo degradation studies for up to 7 weeks. The mechanical properties and scanning electron microscopy (SEM) images of the degraded materials were examined and later correlated to understand the degradation phenomenon. Our results show that Young’s modulus of P(HB-co-17 mol%HHx) during in vitro studies decreased from 3.26 to 2.42 GPa within 4 weeks, and in vivo breakdown resulted in a significant decrease in Young’s modulus with a decrease from 3.26 to 0.51 GPa and a mass loss of 59 % within 7 weeks. SEM images showed the development of pores and cracks on the surface of the material over time. Plasticization and recrystallization were observed and likely play a role in the alteration of mechanical properties.