Biological and chemical decoration of peptide nanostructures via biotin-avidin interactions

Novel architectures with nanometric dimensions hold an immense promise as building blocks for future nanotechnological applications. Biological nanostructures are of special interest due to their biocompatibility and because they allow the utilization of biochemical recognition interfaces. The ability to decorate bio-nanostructures with functional groups is highly important in order to utilize them in several applications including ultrasensitive sensors, drug delivery systems, and tissue engineering. Peptide-based nanostructures have a distinct advantage over other assemblies because they can be easily modified with chemical and biological elements. Aromatic dipeptide nanotubes (ADNT) are formed by the self-assembly of a very simple building block, the diphenylalanine peptide. These nanotubes have remarkable chemical and mechanical properties and their utilization in various applications has previously been demonstrated. Here we report on the chemical modification of ADNT with biotin moieties, in order to enable the selective decoration of the tubes with avidin-labeled species. First, ADNT were prepared in aqueous solution by self-assembly of the dipeptide building blocks. Next, they were modified using N-hydroxysuccinimido-biotin. The level of biotinylation was assessed by the interaction of the tubes with gold-labeled strepavidin and ultrastructural analysis by electron microscopy. The ability of the modified assemblies to serve as a generic functional platform was demonstrated by avidin-mediated conjugation. Avidin was added as a molecular linker to allow the decoration with biotin-labeled quantum dots. The efficient decoration was again probed by the imaging of the modified tubes using laser confocal microscopy. Taken together, we demonstrated the ability to decorate ADNT using a generic avidin-biotin adaptor. This decoration should lead to the integration and utilization of the tubes in various applications.