Fundamental Advances in DNA Nanotechnology: Probes, Synthesis, Photonics, and 3D Printing

The focus of the 11th annual conference on the Foundations of Nanoscience (FNANO) held April 14-17, 2014 in Snowbird UT was self-assembled architectures and devices. The conference continues to be important in providing a comprehensive look at fundamental enabling technologies across a range of nanoscience fields and the eventual advent of molecular electronics.

The majority of the conference discussed self-assembled architectures and devices in the context of DNA nanotechnology (using DNA as a structural building block in nanomaterials construction). DNA is the material of choice for constructing nanoscale objects. It is a useful construction material because the interactions between complementary base pairs are understood, and can be designed and built to create frames and scaffolds that hold other molecules and create structures on their own.

The main technique in DNA nanotechnology is inducing self-assembly, where advances in different methods were discussed such as lithography, 3D printing, electro-chemicals, electronics, and photonics (controlled light interactions with matter).

The scale and required replicability of nanomaterials engenders a strong focus on tool development to determine and assess the progress and quality of self-assembly and other operations. New research was presented in tools related to working with DNA such as probes, detectors, samplers, nanopores, and nanochannels (i.e. waldoes). In silico modeling and prediction remains a crucial step, for example improving the prediction of DNA and RNA folding helps in targeting RNA interference.

Synthetic biology, biomedicine, energy, and basic materials continue to be the important application areas for DNA nanotechnology.

The future of computing – rotaxanes?

One of the great human endeavors at the moment is being able to work at the molecular scale (e.g.; 1-100 nm), using organic and inorganic materials for a variety of purposes ranging from basic materials to computing to electronics to life sciences therapeutics to energy. This includes the designed direction of existing molecular processes (e.g.; biology) and the synthesis of novel materials, structures and dynamic behavior.

Three of the most interesting advances in working at the molecular scale and examples of bio-infotech convergence are described below…

1) Hybrid organic-inorganic rotaxanes
First is the March 2009 work of David Leigh’s lab at the University of Edinburgh in creating hybrid organic-inorganic rotaxanes. A rotaxane (rota/wheel + axis) is a mechanically-interlocked molecular structure, essentially a dumbbell shape with a ring around its middle (Figure 1), often man-made but occasionally existing in nature. In this case, the dumbbell portion of the hybrid organic-inorganic rotaxane is an organic amine, the ring around the middle is a metal.

Figure 1: Rotaxane graphical schematic and crystal structure (source)

The benefit of metal-organic frameworks is that they have the properties of both organic and inorganic materials; structural and functional properties from organic materials and electronic, magnetic and catalytic properties from inorganic materials. This rotaxane molecule has directed shuttle-like behavior, where the metal ring around the center can be pushed to bind at either end, with its biggest potential application being in quantum computing.

2) Bio-inorganic interfaces
A second interesting example of molecular scale work and bio-infotech convergence is biocomposites/GEPIs (genetically-engineered peptides for inorganics) which regulate cell behavior and improve binding at bio-inorganic interfaces by modifying surface chemistry and immobilizing infection-causing bioactive molecules. Candan Tamerler’s lab at the University of Washington is doing some interesting work in this area. Improved bio-inorganic interfaces are needed for reduced infection and seamless interaction between human wetware and implants: heart, hip, prosthetics, eye, brain, etc.

3) DNA nanotechnology
The third interesting bio-infotech convergence example is DNA nanotechnology, the notion of using DNA as a structural building material (for example, for self-directed rapid templating) rather than as an information carrier. One key use is employing DNA as a programmable scaffolding for the self-assembly of nanoscale electronic components, meaning that scaffolds comprised of self-assembled DNA serve as templates for the targeted deposition of ordered nanoparticles and molecular arrays. DNA is formed into tubes and then metallized in solution to produce ultra-thin metal wires. John Reif’s lab at Duke University, Erik Winfree’s lab at Caltech and many other groups are working on DNA nanotechnology. Moving to the molecular scale for electronics manufacture is imperative for maintaining Moore’s Law computing performance improvements.

Future implications
It seems likely that working at the molecular scale and bio-infotech convergence will continue to grow. Organic-inorganic hybridization approaches could proliferate to exploit the full suite of properties afforded by organic and inorganic inputs, and as researchers suggest, lead to novel properties and the ability to harness molecular dynamics for human use.