Synthesis of Zinc Oxide Nanoparticles and Kinetic Analysis of Their Antibacterial Activity against Staphylococcus aureus

摘要

和文要旨 酸化亜鉛（ZnO)は医療、化粧品、工業材料等として幅広く使用されており、近年はナノ 粒子の抗菌活性が注目を集めている。本研究ではZnOナノ粒子を液相法により合成し、市販 のマイクロ粒子（粒径3-10μm)と抗菌活性を比較した。合成したZnOナノ粒子の粒径は 50-250 nmであり、黄色ブドウ球菌、大腸菌、サルモネラ属菌に対する抗菌活性をインダイ レクト·コンダクタンス法により評価した。マイクロ粒子と比較して、ナノ粒子はグラム陽 性菌およびグラム陰性に対して強い抗菌活性を示した。得られたコンダクタンスカーブを用 いて、Takahashiらのgrowth inhibition kinetic modelによる速度論的解析を行つた。速度論的解析は、ZnO粒子は黄色ブドウ球菌の細胞に対する親和性が他の菌より強く、ナノ粒子 の方がマイクロ粒子よりその親和性が高いことを明らかにした。また、ナノ粒子はマイクロ 粒子よりも多くの過酸化水素のような活性酸素種(ROS)を生成した。これらの結果は、ZnO マイクロ粒子に対するZnOナノ粒子の抗菌活性の優位性は、ZnO粒子と細菌細胞の親和性 の増大とROS発生量の増加に起因していることを示唆していた。%Zinc oxide (ZnO) is widely used as a medical, cosmetic, and industrial material, and in recent years, the antibacterial activity of ZnO nanoparticles (NPs) has attracted attention. We synthesized ZnO-NPs by a solution synthesis process and compared their antibacterial activity to that of commercial ZnO microparticles (MPs) with a diameter of 3-10 μm. The synthesized ZnO-NPs, with a diameter of approximately 50-250 nm, were used against Staphylococcus aureus, Escherichia coli, and Salmonella Typhimurium and their antibacterial activities were evaluated by the indirect conductimetric assay. Compared to the ZnO-MPs, the ZnO-NPs were more strongly antibacterial against both Gram-positive and Gram-negative bacteria. The obtained conductivity curves were analyzed using the growth-inhibition kinetic model proposed by Takahashi for calorimetric evaluation. The kinetic analysis revealed that ZnO particles have a stronger affinity to S. aureus than the other bacteria; and compared to ZnO-MPs, ZnO-NPs have a higher affinity for bacterial cells. Also, the amount of reactive oxygen species (ROS) such as hydrogen peroxide generated by ZnO-NPs was more than that by ZnO-MPs. These results suggest that the antibacterial activity of the ZnO-NPs is superior to that of the ZnOMPs because of the increase in the affinity between particles and bacterial cells and the increase in the amount of ROS generated.