ABSTRACT
In this review, the nanobiohybrids formed by DNA/RNA and single-walled carbon nanotubes (SWNTs) have been considered focusing on the structures of the hybrids and the interaction energy between components. It discusses the influence of the polymer type, base sequence, oligomer length, polymer flexibility, and nanotube chirality on the hybrid stability in aqueous suspension. The condition for DNA encapsulation inside nanotube as well as the possibility of DNA sequencing by translocation through SWNT nanopores is viewed too. Considerable attention in this work is paid toward employing the unique DNA/RNA molecular-recognition properties for designing complex architectures from SWNTs, which can be effectively used in nanoelectronics and biosensorics. The state of the problem concerning separation of certain nanotube
species from the bulk material by choosing an appropriate DNA sequence is also presented in this review. 3.1 IntroductionSingle-walled carbon nanotubes (SWNTs) have attracted much attention due to their remarkable physical and chemical properties. Unique functionality makes this nanoscale material very attractive for applications in nanotechnology, electronics, optics, composite materials, as well as for solving a wide spectrum of biological and chemical problems [20, 33, 51, 61, 89]. However, all these applications have so far been limited by practical insolubility of SWNTs in aqueous and organic solvents because they form bundles, where several nanotubes are aligned parallel to each other due to essential van der Waals attraction. In addition, as-grown SWNTs are obtained as the mixture of different species that exhibit different chiralities, diameters and the length. This variety leads to differences in the electronic structure, while its alteration allows to tune electronic and optical properties in a wide range [20, 33, 51, 61, 89]. To overcome these problems, a solution-based processing can be used to disperse SWNTs [68] as well as for selection of certain nanotube species [26]. A noncovalent or supramolecular modification of SWNTs allows to solve this problem preserving the intrinsic electronical and mechanical properties of nanotubes. Noncovalent functionalization is achieved by adsorption of surfactants or small aromatic molecules on the nanotube surface, polymer wrapping, and interaction with biomolecules [83]. In particular, an SWNT forms a stable hybrid structure with single-stranded DNA (ssDNA), which is helically wrapped around the nanotube [106].The SWNT:DNA hybrids are intensively and successfully exploited during more than 10 years for solution of the indicated above problems (see reviews [12, 44, 60, 74] and references therein). In addition, due to DNA peculiarity, a range of these hybrid applications is essentially wider including a creation of new multifunctional nanoarchitecture and nanoassembly (using molecular recognition properties of DNA) [23, 49, 98], development of novel biosensors [47, 90, 84, 87], application in nanomedicine (imaging and drug delivery) [52, 54, 70, 101] and many others.
