Effects of metallic nickel particles on colony formation of JB6 P⁺ cells in soft agar assay.

<p>Metallic nickel nano- or fine particle-treated or untreated JB6 P⁺ cells (1×10⁴) were incubated on soft agar medium for 21 days. TPA (20 ng/ml) was set as a positive control. (A) Images of colony formation of JB6 P⁺ cells in soft agar assay. (a) Control. (b) TPA (20 ng/ml). (c) Metallic nickel fine particles. (d) Metallic nickel nanoparticles. (B) Number of colonies/10⁴ cells in soft agar assay. The cell colonies were scored by a computerized image analyzer. * <i>P</i><0.05 versus untreated control.