Antibacterial Nanostructured Polyhydroxybutyrate Membranes for Guided Bone Regeneration.

The principle of guided bone regeneration (GBR) in orthopedic, cranio-maxillofacial and dental tissue engineering applications is to create a secluded space for the treatment of large bone defects while excluding fibrous connective tissue formation at the defect area. In dental surgeries, a GBR membrane is placed near the dental implant in post-extraction sockets to grow new bone at the implant site, along with inhibiting infection due to the microbial nature of the mouth flora. Poly[(R)-3-hydroxybutyric acid] (PHB) is a natural polyester synthesized by a wide variety of microorganisms which has been proposed for various biomedical applications. In this study, to improve the performance of PHB as a GBR, a NaOH based alkaline treatment was designed to create nanofeatured PHB membranes. The newly fabricated nanofeatured PHB membranes were investigated for GBR applications. The results showed that a quick, simple, and inexpensive sodium hydroxide treatment modified the nanostructured surface morphology and chemistry of the PHB membranes by inducing hydrolysis of the ester bonds in the PHB backbone creating carboxylic surface functional groups, which increased the hydrophilicity of the PHB surfaces. Cytocompatibility studies showed increased proliferation of human osteoblasts (bone forming cells) on the NaOH treated PHB membranes compared to the untreated ones. Importantly, in vitro bacterial studies with Staphylococcus aureus (S. aureus) indicated that the NaOH-treated PHB surfaces inhibited S. aureus growth more than 60% after 48 hours of culture compared to the untreated PHB membrane. Thus, this study, for the first time, showed that nanofeatured PHB membranes modified with a NaOH treatment may be a useful anti-bacterial, osteoconductive GBR membrane for numerous orthopedic, cranio-maxillofacial and dental tissue engineering applications.