Nano-ZnO/ZnO–HAPw prepared via sol–gel method and antibacterial activities of inorganic agents on six bacteria associated with oral infections

The antibacterial activity of zinc oxide (ZnO) and the strengthening of hydroxylapatite whiskers (HAPws) have been widely studied and applied. However, the antibacterial properties of ZnO–HAPws have scarcely been researched. The aim of this study was to further investigate several types of nano-ZnO morphologies of ZnO–HAPws that were prepared using the sol–gel method at different pondus hydrogenii (pH) values and temperatures. The four morphologies of ZnO–HAPws that were investigated here were granule, triangle, short rod and disc type, and these morphologies were investigated at 70 °C at pH 6.4, 37 °C at pH 6.6, 70 °C at pH 6.6 and 70 °C at pH 6.6, respectively. Next, the antibacterial activity of ZnO–HAPw was compared to that of nano-ZnO, commercially available ZnO and tetrapod-like ZnO whiskers (T-ZnOw) with six bacteria that are associated with oral infections: Streptococcus mutans, Lactobacillus casei, Candida albicans, Actinomyces viscosus, Staphylococcus aureus and Escherichia coli. The results of examinations of the minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) showed that the antibacterial activity of ZnO–HAPw exceeded that of the commercially available ZnO and T-ZnOw. Additionally, analysis of variance (ANOVA) analysis of the MBCs revealed that the four tested antibacterial agents had significantly different effects on S. mutans (F = 8.940; P = 0.006), S. aureus (F = 6.924; P = 0.013) and E. coli (F = 4.468; P = 0.04). ANOVA analyses of the MICs revealed that the four tested antibacterial agents had significantly different effects on S. mutans (F = 6.183; P = 0.018), A. viscosus (F = 4.531; P = 0.039) and S. aureus (F = 18.976; P = 0.001).