Polylysine is a type of polyamino acid that can take several forms depending on the stereochemistry of the molecule. Polyamino acids can aid in the attachment of many cell types to tissue culture surfaces by serving as an exogenous source for extracellular matrix. Polylysine coating helps facilitate growth, cell spreading, motility, and differentiation of cells. Typically, polylysine comes in two conformations: Poly-L-Lysine and Poly-D-Lysine. Depending on the cell culture application and other reagents, Poly-L-Lysine or Poly-D-Lysine may be preferred for certain cell types.