The Behavior of Poly(amino acids) Containing L-Cysteine and Their Block Copolymers with Poly(ethylene glycol) on Gold Surfaces

Poly(ethylene glycol) (PEG) is often used to biocompatibilize surfaces of implantable biomedical devices. Here, block copolymers consisting of PEG and l-cysteine-containing poly(amino acid)s (PAA's) were synthesized as polymeric multianchor systems for the covalent attachment to gold surfaces or surfaces decorated with gold nanoparticles. Amino-terminated PEG was used as macroinitiator in the ring-opening polymerization, (ROP), of respective amino acid N-carboxyanhydrides (NCA's) of l-cysteine (l-Cys), l-glutamate (l-Glu), and l-lysine (l-Lys). The resulting block copolymers formed either diblock copolymers, PEG-b-p(l-Glu(x)-co-l-Cys(y)) or triblock copolymers, PEG-b-p(l-Glu)(x)-b-p(l-Cys)(y). The monomer feed ratio matches the actual copolymer composition, which, together with high yields and a low polydispersity, indicates that the NCA ROP follows a living mechanism. The l-Cys repeat units act as anchors to the gold surface or the gold nanoparticles and the l-Glu repeat units act as spacers for the reactive l-Cys units. Surface analysis by atomic force microscopy revealed that all block copolymers formed homogenous and pin-hole free surface coatings and the phase separation of mutually immiscible PEG and PAA blocks was observed. A different concept for the biocompatibilization of surfaces was followed when thiol-terminated p(l-Lys) homopolymer was first grafted to the surface and then covalently decorated with HOOC-CH2-PEG-b-p(Bz-l-Glu) polymeric micelles. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 248-257