The biocompatible barriers with dual character for surface active agents like biosurfactants were made by reacting cationic polylysine(PL) with nonionic poly(ethylene glycol) (PEG) to give block and graft PL-PEG copolymers, PL-b-PEG and poly-L-lysine (PLL)-g-PEG. In particular, PL-b-PEG block copolymers were synthesized by a new method using an activated succinimidyl ester of carboxymethylated MPEG(SCM-MPEG) and a blocked poly-ε-CBZ-lysine (PLZ). One component, FL, adsorbs to a cell or a tissue surface, and the other, PEG, which has no strong interaction with the surface, dangles away from it, thus blocks the adhesion of the cells or tissues to the surface. The chemical structures of the intermediates and copolymers were confirmed by ¹H NMR, titration, and UV. The self-assembling PLL-g-PEG copolymers significantly reduced. the adhesion of human foreskin fibroblasts (HFFs) and red blood cells (RBCs) due to the nonadhesive property and chain mobility of PEG attached, whereas PL-b-PEG did not. It, therefore, suggests that graft copolymers are more desirable than block ones in prevention of cell-tissue interactions.