MTT assay to determine the cell cytotoxicity of Ni2+

Nickel chloride hexahydrate powder (2.376 g) was weighed and dissolved in 100 ml of complete RPMI-1640 medium to obtain 0.1 M Ni²⁺. Then, 0.1 ml of the stock solution was diluted 1000-fold and 500-fold with complete RPMI-1640 medium to obtain 100 μM and 200 μM Ni²⁺, respectively.

The in vitro cytotoxicity of 100 μM and 200 μM Ni²⁺ in L929 cells after 12, 24, 48 and 72 h of treatment was examined using a MTT assay as described in a previous study [5]. Cells that were not treated with Ni²⁺ served as a negative control, and cells that were treated with 0.7% acrylamide in complete RPMI-1640 medium served as a positive control. The sample size was six.