INTELLECTUAL MERIT: Living organisms use biomacromolecules to pattern inorganic materials into exquisite structures with nanoscale precision and specific physical function. The research proposed here utilizes biomolecules and bio-inspiration to develop and integrate novel bio-fabrication processes using genetic engineering tools for building functional multi-component nanostructures. This collaborative partnership between Duke University and the University of Washington aims to fabricate complex, plasmonically functional inorganic nanostructures using protein-directed immobilization on self-assembled 3D DNA templates. The study makes use of addressable DNA tile lattices, genetically selected and engineered peptides for nucleating and directed immobilization of specific inorganic materials, and DNA binding proteins (DBPs) to bridge between the two. Genetically engineered peptides for inorganics (GEPIs) are selected in vivo for their ability specifically to synthesize and/or immobilize nanoparticles of metals, semiconductors, and oxides from electrolyte solutions. These peptides will be fused genetically with DBPs designed to attach to the DNA tile lattice at specifically addressed binding sites. Once arrayed on the lattice the GEPIs will serve to precipitate desired inorganic materials under mild conditions at precise locations to produce functional nanostructures with interesting plasmatic properties.
BROADER IMPACTS: The proposed work will develop new bio-fabrication techniques to create a wide variety of nanophotonic, nanoelectronic, and nanomagnetic devices with high information density. The fabrication of biomedical devices is an obvious objective, but much broader applications can also be envisaged. The Duke team will offer summer lab positions to talented high school students from the North Carolina School of Science and Math. They will also mentor students from the American Chemical Society's Project SEED (Summer Educational Experience for the Disadvantaged). The Duke PI and Co-PI lead the Duke Nanoscience Seminar Series that disseminates nanoscience research across the campus. The University of Washington group participates in eight outreach programs on the Washington campus. These include a summer REU program, an academic year undergraduate research experience program for Native American students, and an NSF-NEU program for curriculum development for undergrads that includes a hands-on scanning probe microscopy lab.
The overarching goal of this multidisciplinary, collaborative biomaterials research project was to develop self-assembling molecular platforms for eventual use in bottom-up fabrication of nano-scale materials and devices. Particularly, we set out to create self-assembling DNA lattices in which genetically engineered peptides, linked to the DNA building blocks through specific interaction of DNA-binding proteins or via chemical coupling, could be used to immobilize and organize inorganic nanomaterials. We are working toward a general-purpose, artificial, programmable biomineralization system. That is, we are building a toolbox of materials and methods with which to mimic the incredible diversity and complexity of nano-scale materials constructed by biological systems. With such a toolbox, we will fabricate nanoparticle/biomolecular hybrid systems which promise great utility in nanophotonics, nanoelectronics, and nanomagnetics. The intellectual merit of the study stems from the creative, biomimetic strategy that has been developed. During this project we shown, for the first time, that only a single copy of the peptide molecule is required for organizing a metal nanoparticle. Our technical accomplishment is illustrated in the attached figure. In Panel A, rows of organized gold nanoparticles (AuNP) organized on peptide-labeled DNA lattice using 4:1 ratio of particles to peptides with 3 minute binding time. Boxed region depicts the magnified area shown in Panel C. The dense coverage of AuNP on DNA nanogrid shown in Panel B was achieved after 20 equivalents AuNP were allowed to bind for 30 minutes. Very few unbound AuNP were detectable on the exposed mica surface, as desired for a fabrication protocol with low background of unwanted side-products. In Panel C is a magnified AFM image of outlined region from Panel A. Comparison of the atomic force microscope image with the cartoon in Panel D shows that AuNP binding favors one peptide configuration (red) over the other (blue). The cartoon depicts peptides displayed on opposite sides of the grey-coloured 2D DNA lattice as red and blue circles. Predicted distances between rows of AuNP in Panel D correspond well with measured distances as shown in Panel C. Our advances here have provided encouragement to pursue the biomolecular templating of functional single-electron transistors, sensors, and other electronic devices. Reliable assembly of functional electronic devices using biomolecules, a long sought after goal, is now one step closer to implementation. The broader impacts of the completed project include the training of multiple post-doctoral fellows, post-graduate students, undergraduate students, and high school students from under-represented minorities in the emerging, interdisciplinary field of bionanotechnology.
