3,3′Diaminobenzidine (DAB) Staining Solution

• 1. Per five wells from a 12-well plate used during the DAB staining: Dissolve one 10-mg DAB tablet (e.g., Sigma-Aldrich D5905) in 20 mL phosphate-buffered saline (PBS; 1×).

• 2. Add 40 µL nickel chloride (NiCl₂; 1% [w/v] in distilled H₂O) and 40 µL of cobalt sulfate (CoSO₄; 1% [w/v] in distilled H₂O) to the DAB mixture.

• 3. Finally add 20 µL of hydrogen peroxide (H₂O₂; 0.1%) right before filling the well plates with the staining solution.

  • Nickel chloride and cobalt sulfate solutions can be made ahead of time and stored for up to 2 yr at 4°C.

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