Life Science

Bio Brief: Poly-L-lysine Hydrobromide

Structure and functionality of Poly-L-lysine

Poly-L-lysine hydrobromide is a non-specific attachment factor useful for promoting cell adhesion to solid substrates, such as coverslips, slides, and microwell plates. Poly-L-lysine is a positively-charged amino acid polymer. The structure consists of approximately one lysine residue for every hydrobromide salt. Poly-L-lysine enhances electrostatic interaction between negatively charged ions of the cell membrane and the culture surface. When adsorbed to the culture surface, Poly-L-lysine increases the number of positively charged sites available for cell binding.

Sigma offers a full range of Poly-L-lysine products with varying molecular weight. The lower molecular weight Poly-L-lysine (30,000-70,000) is easier to use because it is less viscous in solution, but the higher molecular weight poly-lysine (>300,000) provides more attachment sites per molecule. The molecular weight range often preferred by researchers is 70,000-150,000.

Protocol for coating with Poly-L-lysine

Optimal conditions must be determined for each cell line and application.

  1. Add 50 mL of sterile tissue culture grade water to 5 mg of Poly-L-lysine.
  2. Aseptically coat culture surface with 1.0 mL/25 cm2 (only). Rock gently to ensure even coating of the culture surface.
  3. After 5 minutes, remove solution by aspiration and thoroughly rinse surface with sterile tissue culture grade water.
  4. Allow to dry at least 2 hours before introducing cells and medium.

*NOTE: Step 1 is not necessary for Poly-lysine Solution, (Cat. Nos. P4707 and P4832).