Nanotechnology is a young and rapidly growing field that offers novel and promising solutions for a variety of scientific areas. In particular, metal and semiconductor nanoparticles possess unique, size-dependent magnetic, optical, and electronic properties. The directed assembly of nanoparticles by means of biomolecules is of great current interest to the materials science and medical technology ﬁelds due to their potential use in sensing and cell targeting. In particular, peptides comprise diverse functional groups that enable fine-tuning of the structural and electrostatic properties of the resulting materials.
Figure 5. Peptide-directed organization of nanoparticles by means of pH switch.
We are investigating the suitability of the α-helical coiled coil folding motif for the organization of gold nanoparticles. We were able to demonstrate the superiority of this motif not only as a deﬁned structural template but also as a self-organizing system for the assembly of gold nanoparticles. The general coiled coil design was modified such that the peptides are able to undergo electrostatically attractive interactions with anionic nanoparticles. A key feature of the system is that the organization of the nanoparticles into deﬁned networks can be directed by the external factor of pH, and that the organization is reversible and repeatable. The assembly of nanoparticles causes a subsequent change in the quarternary structure of the peptides to α-helical rich fibers (Wagner, Org. Biomol. Chem., 2009). On the other hand, model peptides can undergo a nanoparticle-induced folding transition into β-sheets, followed by a subsequent aggregation process into ﬁbrils (Wagner, Small, 2010).