Programmed Materials Synthesis with DNA.

Learning how to control the formation and twoand three-dimensional assembly of molecular scale building blocks into well-defined mesoand macroscopic structures is the essence of nanotechnology and materials chemistry. DNA is arguably one of the most programmable “assemblers” available to the synthetic chemist and materials scientist, yet until recently, it has been an underutilized synthon in materials chemistry. The purpose of this review is to summarize advances made involving new strategies that rely on the use of both naturally occurring DNA and synthetic oligonucleotides to assemble nanoscale nonbiological building blocks into extended mesoand macroscopic structures. Although early in their development, some of these strategies already have been shown to be useful in generating novel nanostructured materials,1-4 arranging inorganic nanoparticles into “anatural” configurations,5,6 understanding interparticle electronic interactions,1 templating the growth of nanocircuitry,7 and developing a promising new detection technology for DNA.8,9 There are two basic types of building blocks that are applicable to a variety of assembly schemes: molecules with synthetically programmed recognition sites or bits of matter with nanoscale dimensions and well-defined surface chemistries. The latter type of building block is often referred to as a “nanoparticle” or “nanocrystal”. Assembly of such building blocks into extended, well-defined structures can provide a variety of functional materials with applications including ultrasmall electronic devices,10-13 spectroscopic enhancers,14,15 high-density information storage media,16,17 and highly sensitive and selective chemical detectors.8,9,18 The assembly of nanoparticle and molecular building blocks into functional structures has been accomplished through both physical and chemical methods.19 Physical methods include the use of scanning probe microscopy,20-22 electrophoretic strategies,23,24 LB films,25,26 or templatedriven sedimentation27 to position particles in a preconceived fashion within a matrix or on a substrate. Although effective for preparing certain types of nanoscale architectures, many of these physical methods are limited because they are often slow and do not lend themselves to preparing designed nanostructured architectures that canvas macroscopic dimensions. Chemical methods include ordering particles based upon interparticle electrostatic interactions,28-30 covalent assembly,31,32 template recognition,33,34 template recognition with subsequent covalent cross-linking reactions,35,36 crystallization based upon weak intermolecular interactions,37-41 or linking reactions involving designed organic or biological recognition sites.1,2,4,42 The advantages of chemical methods are that building block linking processes can occur in a massively parallel fashion and in some cases possess self-annealing or correcting properties. This makes them particularly attractive for constructing twoand three-dimensional structures on a faster time scale. The disadvantage is that at present chemical methods, when compared with some of the aforementioned physical deposition methods, are difficult to control. Recently, there has been substantial interest in utilizing biomolecules to direct the formation of extended mesoand macroscopic architectures.43,44 The advantage of using biomolecules is that molecular recognition is already built into the building block of interest (e.g., peptides, oligonucleotides, and proteins). In some cases, synthetic versions of the biomolecules are readily available and easily adaptable to both inorganic and organic building blocks and substrates.45 This review examines the use of one class of these biomolecules, DNA, to organize nanometer-sized structures into preconceived extended, functional structures and materials. It is divided into three categories; the use of (1) oligonucleotides (singlestranded DNA) to prepare mesoand macroscopic organic structures, (2) duplex DNA as a physical template for growing inorganic wires and organizing nonbiological building blocks into extended hybrid materials, and (3) oligonucleotide functionalized nanoparticles and sequence-specific hybridization reactions for organizing such particles into periodic, functional structures. 1849 Chem. Rev. 1999, 99, 1849−1862