Amphoteric, Prevailingly Cationic L-Arginine Polymers of Poly(amidoamino acid) Structure: Synthesis, Acid/Base Properties and Preliminary Cytocompatibility and Cell-Permeating Characterizations.

A linear amphoteric poly(amidoamino acid), L-ARGO7, is prepared by Michael-type polyaddition of L-arginine with N,N0-methylenebisacrylamide. Chain extension of acrylamide end-capped L-ARGO7 oligomers with piperazine leads to high-molecular-weight copolymers in which L-arginine maintains its absolute configuration. Acid/base properties of L-ARGO7 polymers show isolectric points of 10 and positive net average charges per repeating unit at pH¼7.4 from 0.25 to 0.40. These arginine-rich synthetic polymers possibly share some of the unique biological properties of polyarginine cell-permeating peptides. In vitro tests with mouse embryo fibroblasts balb/3T3 clone A31 show that L-ARGO7 polymers are endowed with effective cell internalization ability combined with minimal cytotoxicity.