NANOTECHNOLOGY
Current Research - Directed Bioassembly of Quantum Dots
Interest in the concept of self-assembled nanostructures led to the idea of using DNA as a scaffold or template for the programmed assembly of nanoscale arrays (see J. J. Storhoff, C. A. Mirkin, Chem. Rev. 99, 1849, 1999). Beginning in the 1980's, Seeman et al. experimented with combining DNA fragments to produce geometrical shapes, including cubes, triangles, two-dimensional arrays and various forms of DNA knots. Recently, LaBean, Seeman, et al. have continued this work with the construction of triple crossover Complexes. This work has pioneered the concept of using DNA as a structural molecule, which offers many advantages compared to other homopolymers. DNA can be easily synthesized in lengths up to 40 nm and double-stranded DNA can be joined end to end to produce longer linear molecules or more complex shapes. It can be modified with functional groups at predetermined sites to allow for the attachment of other molecules in a specific manner.
We have developed a new approach for binding nanoparticles to DNA. Functionalized nanoparticles are covalently bound to internal, chemically modified bases on double-stranded DNA without the presence of destabilizing "nicks" along the DNA backbone. Since DNA can be synthesized with a variety of chemical modifications, this technique allows great versatility in the attachment of nanoparticles with corresponding functional groups. This method potentially allows closer spacing of very small particles than hybridization based methods, and greater precision in the placement of particles than using a plasmid or the DNA backbone as a template. In addition, we developed an approach for thiolating one end of the DNA/nanoparticle product and attaching it to a gold surface. The ability to attach one or both ends of the DNA/gold complex, after generation of the desired pattern, to fixed contacts or electrodes is a necessary step in nanodevice fabrication.
In summary, this technique addresses a basic need to assemble nanometer-scale objects in a programmable manner and in a massively parallel fashion, from the bottom up.
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