Production and evaluation of biodegradable composites based on PHB–PHV copolymer

In recent years, emphasis in biomaterials engineering has moved from materials that remain stable in the biological environment to materials that can degrade in the human body. Biodegradable materials are designed to degrade gradually and be replaced eventually by newly formed tissue in the body. In this investigation, two particulate bioactive ceramics, i.e., hydroxyapatite (HA) and tricalcium phosphate (TCP), were incorporated into polyhydroxybutyrate–polyhydroxyvalerate (PHB–PHV), which is a biodegradable copolymer, to produce new biomaterials for potential medical applications. All raw materials were commercially available and they were characterised prior to composite production. HA/PHB–PHV and TCP/PHB–PHV composites containing up to 30 vol% of the bioceramics were produced through an established procedure. Compounded and compression moulded materials were evaluated using various techniques including thermogravimatric analysis, scanning electron microscopy , differential scanning calorimetry and dynamic mechanical analysis. The results showed that intended compositions of composites had been achieved and bioceramic particles were well distributed in the polymer. The degradation temperature of PHB–PHV was significantly reduced by the incorporation of bioceramics, while the melting temperature was slightly affected by the addition of bioceramics. The crystallinity of PHB–PHV was also varied with the presence of HA or TCP particles. The storage modulus and loss modulus of the composites increased with the increase in HA or TCP content. Composites containing the highest percentage of bioceramics exhibited the highest stiffness. Preliminary in vitro study indicated enhanced ability of the composites to induce the formation of bone-like apatite on their surfaces.