Synthesis and Cell Interaction of Statistical l‑Arginine–Glycine–l‑Aspartic Acid Terpolypeptides

Copolymerizations and terpolymerizations of N-carboxyanhydrides (NCAs) of glycine (Gly), N_δ-carbobenzyloxy-l-ornithine (Z-Orn), and β-benzyl-l-aspartate (Bz-Asp) were investigated. In situ ¹H NMR spectroscopy was used to monitor individual comonomer consumptions during binary and ternary copolymerizations. The six relevant reactivity ratios were determined from copolymerizations of the NCAs of amino acids via nonlinear least-squares curve fitting. The reactivity ratios were subsequently used to maximize the occurrence of the Asp–Gly–Orn (DGR′) sequence in the terpolymers. Terpolymers with variable probability of occurrence of DGR′ were prepared in the lab. Subsequently, the ornithine residues on the terpolymers were converted to l-arginine (R) residues via guanidination reaction after removal of the protecting groups. The resulting DGR terpolymers translate to traditional peptides and proteins with variable RGD content, due to the convention in nomenclature that peptides are depicted from N- to C-terminus, whereas the NCA ring-opening polymerization is conducted from C- to N-terminus. The l-arginine containing terpolymers were evaluated for cell interaction, where it was found that neuronal cells display enhanced adhesion and process formation when plated in the presence of statistical DGR terpolymers.