Bacterial polyesters for biomedical applications: In vitro and in vivo assessments of sterilization, degradation rate and biocompatibility of poly (β-hydroxyoctanoate) (PHO)

Poly (β-hydroxyalkanoates) (PHAs) are bacterial polyesters with chemical and physical properties that make them suitable for medical applications. They are obtained by fermentation techniques, are biodegradable and may be metabolized into normal constituents of the body. A PHA produced by Pseudomonas oleovorans has generated a random copolymer called poly (β-hydroxyoctanoate) (PHO) having elastomeric properties and displaying lower crystallinity and less rigidity than poly (β-hydroxybutyrate) (PHB). As part of an extensive study, we compared the effects of two methods of sterilization on the physical and structural characteristics of PHO, studied the mechanism and degradation rate of PHO in vitro over a 24-month period in physiological media and finally, investigated the biocompatibility and degradation rate of PHO in vivo as a new sealant for the polyester arterial prosthesis. Results have shown that the physical and structural properties of PHO were well-preserved after ethylene oxide sterilization, whereas gamma radiation caused random chain scission and physical cross-linking. In vitro incubation studies demonstrated that the degradation rate of PHO films in water or isoosmotic PBS is a very slow hydrolytic process exceeding two years. In vivo, PHO showed good biocompatibility in terms of tissue enzymatic activity and cellular reactions. Degradation was slow and exhibited similar rate as that observed in vitro. As a sealant in a polyester arterial prosthesis, PHO contributed to the impermeabilization of the graft wall and to the development of an internal collagenous capsule with a confluent endothelium secreting prostacyclin.