The Investigation of ZnO/Poly(vinylidene fluoride) Nanocomposites with Improved Mechanical, Piezoelectric, and Antimicrobial Properties for Orthopedic Applications

Studies have shown that piezoelectric materials can be used as bioactively charged surfaces to induce tissue regeneration (like bone reconstruction). β-phase poly(vinylidene fluoride) (PVDF) and zinc oxide (ZnO) are regarded as potential bone tissue engineering materials because of their piezoelectricity and biocompatibility. Additionally, ZnO nanoparticles (NPs) are ideal materials to reduce infection. In this study, PVDF scaffolds doped with ZnO NPs (ZnO/PVDF) were prepared by electrospinning increasing ZnO concentrations and the ratio of the β-phase PVDF resulting in an enhanced the modulus, elongation to failure and load stress. In vitro osteoblast assays were also performed to determine material cytotoxicity and bone reconstruction potential. Results exhibited that the piezo-excited scaffolds had a 30% greater osteoblast density, compared to non-piezoelectric-excited groups after 3 days of culture. To evaluate the scaffold's antimicrobial properties, three common etiologic agents of orthopedic after-surgery infection, Staphylococcus aureus (SA), Methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli), were separately seeded and counted. Results of this in vitro study showed significantly reduced E. coli (45%), SA (48%) and MRSA (37%) density on the 1 mg/ml ZnO/PVDF scaffolds without piezo-excitation (compared to the control). Moreover, compared to the non-piezo-excited scaffolds, results showed for the first time that the density of the same bacteria on the piezo-excited scaffolds reduced by over 23%, 22%, and 33%, respectively. For the first time, the effects of novel ZnO/PVDF scaffolds on osteoblasts and bacteria were investigated here, and significantly decreased bacteria with increased osteoblast density on the piezo-excited scaffolds demonstrated that these scaffolds have a strong potential for numerous antibacterial orthopedic applications.