This totally depends on the Nucleofector® system you are working with.
While in the 100 µL reaction vessels usually 1 - 5 µg DNA is being used, for the 20 µL reaction vessels (e.g. X Unit, 96-well Unit and HT Nucleofector® System)
0.2 – 1 µg DNA is a good starting amount.
Working with the 4D-Nucleofector® LV Unit is scaleable and therefore per 1 mL reaction about 40 µg should be calculated.
Please ensure that the volume of substarte added should not exceed 10% of the total reaction volume to avoid significant dilution of the Nucleofector® Solution by substrate buffer. Alternatively, the substrate might be diluted by Nucleofector® Solution.
Furthermore, some cells might be sensitive to larger amounts of DNA. Please check the cell specific Optimized Protocol (OP) for the recommended total DNA amount of the cell type of interest.