A gradient-driven methodology has been developed to manipulate the movement of dendritic macromolecules. Poly(propyleneimine) dendrimers, labeled with rhodamine B, are attached to glass substrates via multiple imine bonds. The dendrimers are able to move on the surface by the hydrolysis and re-formation of these imine bonds. In the absence of an external stimulus, this random movement results in a two-dimensional diffusion on the substrate. We are able to bias the movement of these nanoparticles by means of an aldehyde gradient on the glass substrate.
Chang, T., Rozkiewicz, D. I., Ravoo, B. J., Meijer, E. W., & Reinhoudt, D. (2007). Directional movement of dendritic marcomolecules on gradient surfaces. Nano letters, 7(4), 978-980. https://doi.org/10.1021/nl070005v