Peptide Nano-Assemblies as Novel Materials for Bionanotechnology

Formation of nanotubes, nanospheres, and other nano-assemblies by peptides

Nanostructures that are being formed by the self-assembly of peptides, small fragments of proteins composed of few amino-acids, are proven to be key novel materials for many nanobiotechnological applications. The useful applications of these structures as novel antibacterial agents, components of highly sensitive biosensors and diagnosis tools, drug delivery vehicles, and scaffolds for tissue engineering and regeneration, was already demonstrated. Several groups around the world had revealed the ability of very simple peptide building blocks to assemble into well-ordered nanotubes, nanospheres, nanotapes, and nanoscale-ordered hydrogels. All these structures are being built by the hierarchical process of molecular recognition and self-association which constitutes the basic principles of "bottom-up" assembly, a key principle for nanotechnological applications.

The technological advantage of peptide building blocks

Peptide assemblies are very attractive building blocks. Their inherent biocompatibility and the easy ability to modify them chemically or biologically make these building blocks very unique components in future nanotechnological applications. These peptides combine the advantages of biologically-derived components on the one hand and the chemical properties of advanced functional materials of the other. These biomolecular blocks could be chemically synthesized in large amounts, from milligrams to kilograms or even tons. Peptides are also quite inexpensive materials when their large-scale synthesis is being optimized. One dipeptide (a peptide composed of two amino-acids) that is routinely being synthesized in large amounts is L-alpha-aspartyl-L-phenylalanine methyl ester. This compound that is better known as the sweetener Aspartame is being annually synthesized in ton-scale. The price of one gram of Aspartame is only few cents. A quite similar peptide, diphenylalanine, was shown to form peptide nanotubes in high efficiency. Therefore, this peptide could allow the assembly of functional nanotubes for a price of cents per gram as compared to tens of dollars per gram for carbon nanotubes, the current major building blocks for nanotechnology.

Demonstrated applications of peptide nanostructures

Since the last twelve years since peptide nanotubes were first engineered, their usefulness was already proven. Peptide nanotubes were demonstrated to serve as novel antibacterial agents that exert their activity by forming nano-channels in the bacterial membrane. This property is highly desirable due to the large increase in the incidences of antibiotic-resistant bacteria. Other studies had demonstrated the value of biologically-modified nanotubes for high-sensitivity analysis of chemicals and biological-agents such as bacteria and viruses. Their application should lead the design of ultrasenstive biosensors and diagnostic tools for medical, environmental and security applications. Peptide hydrogels with nano-scale order were shown to be key elements in tissue engineering and regeneration by supplying both an excellent physical support as well as guided matrix for the growth and proliferation of cells. These applications, most intriguing their support of nerve cells growth, may provide a solution for the devastating consequences of spinal cord and other nervous system injuries.

Future prospect for the applications of peptide nanostructures