Nano ni

Both Ni and TiO₂nanoparticles (Nano-Ni and Nano-TiO₂) were obtained fromInabata& Co., Ltd., Vacuum Metallurgical Co., Ltd., Japan. The detailed characterization of metal nanoparticles was described in our previous publications(Mo et al. 2019 (link); Wan et al. 2011 (link); Yuan et al. 2021 (link)). Briefly, the mean diameters of Nano-Ni and Nano-TiO₂ in the powder are 20nm and 28nm determined by transmission electron microscopy (TEM); the specific surface area is 43.8 m²/g for Nano-Ni, and 45.0 m²/g for Nano-TiO₂. The mean size of particles and agglomerates in the cell culture medium is 250 nm for Nano-Ni and 280 nm for Nano-TiO₂. The solubility of Nano-Ni is 16.48 ± 0.58 (ppm) in 1x PBS and 81.23 ± 3.76 (ppm) in the cell culture medium, and less than 1 ppm in both 1x PBS and cell culture medium for Nano-TiO₂. Nano-Ni and Nano-TiO₂ were prepared at 1 mg/mL in physiological saline, ultrasonicated for 10 min in an ultrasonic cleaner FS30 (Fisher Scientific, Pittsburg, PA), which has an operating frequency of 40kHz, and vortexed thoroughly prior to adding to the cells in each experiment.