Assembly of Helical Nanostructures: Solvent-Induced Morphology Transition and Its Effect on Cell Adhesion

Being able to precisely manipulate both the morphology and chiroptical signals of supramolecular assemblies will help to better understand the natural biological self-assembly mechanism. Two simple l/d-phenylalanine-based derivatives (L/DPFM) have been designed, and their solvent-dependent morphology evolutions are illustrated. It was found that, as the content of H₂ O in aqueous ethanol solutions was increased, LPFM self-assembles first into right-handed nanofibers, then flat fibrous structures, and finally inversed left-handed nanofibers. Assemblies in ethanol and H₂ O exhibit opposite conformations and circular dichroism (CD) signals even though they are constructed from the same molecules. Thus, the morphology-dependent cell adhesion and proliferation behaviors are further characterized. Left-handed nanofibers are found to be more favorable for cell adhesion than right-handed nanostructures. Quantitative AFM analysis showed that the L929 cell adhesion force on left-handed LPFM fibers is much higher than that on structures with inversed handedness. Moreover, the value of cell Young's modulus is lower for left-handed nanofibrous films, which indicates better flexibility. The difference in cell-substrate interactions might lead to different effects on cell behavior.