Synthesis and Self-Assembly of RGD-Functionalized PEO-PB Amphiphiles

Amphiphilic block copolymer self-assembly provides a versatile means to prepare nanoscale micelles in solution. The utilization of these structures as targeted drug delivery vehicles has motivated efforts to prepare bioactive ligand-functionalized polymer micelles. The impact of ligand conjugation on micelle morphology was examined through use of well-characterized poly(ethylene oxide)-b-poly(butadiene) (OB) block copolymers functionalized to varying extents with a biologically relevant RGD-containing peptide sequence. Micelle morphology and dilute solution behavior of RGD-functionalized OB (RGD-OB) copolymers were examined using cryogenic transmission electron microscopy (cryo-TEM) and dynamic mechanical analysis. The direct dispersion of RGD-OB copolymers into deionized water yielded a variety of structures; the observed morphologies deviated from the canonical series predicted by the overall change in amphiphile composition due to peptide conjugation. RGD functionalized spherical micelles, cylindrical micelle networks, and annular multilayer vesicles were prepared. The morphological behavior was attributed to interactions between peptide moieties conjugated to the termini of coronal chains and has implications in the design of targeting micelles for drug delivery applications.