Self-assembling biomaterials: L-lysine-dendron-substituted cholesteryl-(L-lactic acid)_n̄

This report describes the synthesis and supramolecular organization of a novel class of linear-dendritic block copolymers. The molecules, which are termed rodcoil dendrons, consist of a cholesterol moiety that is attached to L-lysine dendrons of three different generations via a biodegradable oligo(L-lactic acid)_n̄ spacer. Whereas the molecules exhibit very poor ordering in the dry state, different supramolecular morphologies were observed in the hydrated state. Cholesteryl-(L-lactic acid)_23̄-(L-lysine)_G1 and cholesteryl-(L-lactic acid)_23̄-(L-lysine)_G2 self-assemble into lamellar structures with periodicities that depend on degree of hydration. At low degrees of hydration, lamellar ordering was also observed for cholesteryl-(L-lactic acid)_22̄-(L-lysine)_G3. However, at 50 wt%, water steric hindrance in the highly hydrated L-lysine dendrons no longer allows lamellar ordering, and discrete nanosized aggregates are formed. Evidence for the formation of such nanoaggregates was obtained from dynamic light scattering, electron microscopy, and atomic force microscopy. These rodcoil dendron biomaterials could be of potential interest as temporary molecular scaffolds for cell and tissue engineering.