Peptide Nanotechnology for Device Building Blocks, 3D Assembly, and Sensing

Here the fabrication of various nano-structures and complex patterns was demonstrated by combining technologies of peptide self-assembly, biomineralization, and lithography. Our strategy is to use the molecular recognition of peptides and proteins to program the assembly of nanoscale building blocks at uniquely defined positions. After configuring device geometries with these nanotubes, we turned on the biomineralization function of peptides to develop various material coatings such as metals and semiconductors for electronics, sensors, and solar cell applications. Another strategy is to write these mineralizing peptides directly on substrates by lithography and metal/semiconductor patterns are generated in nanoscale via biomineralization on these peptides.

The ability to control the self-assembly of nanoscale materials into complex three-dimensional (3D) architectures from functional building blocks could allow further development of complex device configurations. DNA bionanotechnology has recently been used to precisely assemble 3D shapes from DNAs in small scale, however peptides are another of natures building blocks with even more specificity, robustness, and versatility for assembly that can be exploited to design new 3D architectures. Here, nanoscale peptides and ligand-functionalized nanoparticle hubs were self-assembled into micron scale 3D cube-shaped crystals, creating a physical framework for the proposed biomimetic assembly strategy. In this approach we took advantage of the naturally robust assembly of collagen triple helix peptides and used them as nanowire building blocks for the 3D crystal generation. Using streptavidin-functionalized Au nanoparticles and the a1 chain of type I wild type collagen specifically modified with a biotin moiety in vivo, we created micro-sized cubes with peptide nanowires as spokes and Au NPs as hubs. SAXS measurement reveals the position of NPs in peptide cage in these cubes, and the change of angle between the peptide nanowire and the NP in the unit cell by tethering the size and the shape of the hub NPs created various shapes of crystals. This simple, rapid fabrication protocol produces high yields of 3D materials in controlled shapes, dependent on the design of the NP junctions, with extremely high yields, promising ease and flexibility in manufacturing future functional devices in memory and solar cells.

The 2D peptide assemblies can be applied to biosensor chips for detecting pathogens, heavy metals, and cancer cells. When the peptide nanotubes coated by the antibody of target pathogen were bridged between a pair of electrodes, the detection was made by the capacitance change via the binding events of viruses on the nanotube. The advantage of this chip sensor as compared to conventional nanoscale chip sensor is that the characteristic capacitance values for pathogens could be used to identify the stains of viruses in addition to the antibody recognition of the nanotube. The sensing with the peptide nanotube sensor chip was fairly robust and the detection limit was on the order of 100 virus or bacteria particles/mL. Recently we demonstrated that this chip can be applied to detect heavy metals for environmental monitoring. Cancer cells can also be detected sensitively in label-free by probing the difference in membrane mechanics; cancer cells are more elastic than normal cells. As these cells were swollen under hyposmotic pressure, elastic cancer cells swell and this change is detected by the impedimetric transducer on the order of 10 cancer cells in 10,000 normal cells. This sensing platform is reusable by simple washing process, an important practical aspect of this sensor chip.