DNA-based materials

Measurements on a different type of DNA-based material were reported by Rinaldi et al. [68] (see Fig. 13). In this experiment they deposited a few layers of deoxyguanosine ribbons in the gap between two planar metal electrodes, -100 nm apart. The current-voltage curves showed a gap followed by rise of the current beyond a threshold of a few volts. The curves depended strongly on the concentration of the deoxyguanosine in the solution. 

Research on DNA-based materials also depends on the facility of obtaining various DNA samples. Profiting from the life sciences, the automated synthesis method is virtually able to synthesize designed DNA, and the polymerase chain reaction (PCR) can amplify the DNA sequence. On the other hand, as a native substance widely existing in organisms, DNA has a broad source in the natural world, especially, from fisheries. A typical case is the salmon milt, which is mostly treated as feedstuff. The DNA content in salmon milt is over... 

Fig. 14). The DNA-immobilized columns effectively accumulated more DNA-intercalating materials than the planar DNA films. The DNA-immobilized columns bound endocrine disruptors with a planar structure, such as dioxins, and benzo[a]pyrene. Bisphenol A and diethylstilbestrol, which lack a planar structure, did not bind to the DNA-coated columns. Table 1 shows the selective adsorptions of the insoluble DNA-based materials. 

Fig. 15 Optical images of DNA-based materials for environmental purpose, a DNA-alginic acid hybrid matrix coagulated by Ca2+, in fiber, film, and gel form, b DNA-immobilized porous glass beads prepared by UV-irradiation. c DNA-polyacrylamide hydrogel beads synthesized by inverse suspension polymerization...

Despite the great findings, DNA based materials are not feasible for the development of sensors due to their environment reactivity, difficulties in the assembly, poor addressability and manipulation of single structures, and difficulties removing the structures from solutions. Thus, graphene sheets are considered as the main... 

Self-assembly is used to organize molecules into amazing and complex structures. Small molecular weight molecules can be assembled into structures of varying degrees from dimers and trimers all the way up to and including supramolecular polymers. Simple amphiphiles form micelles and vesicles. Dendrimers, DNA-based materials, peptides, and peptides amphiphiles have been assembled into nanostructured fibrals reminiscent of the extracellular matrix. Obviously, we cannot cover here even a fraction of the creative and functional assembled systems reported. In this section, we highlight selected symmetrical self-assembled systems to illustrate how different... 

Mirkin C A ef a/1996 A DNA-based method for rationally assembling nanopartioles into maorosoopio materials Nature 382 607... 

Mirkin C.A., Letsinger R.L., Mucic R.C., Storhoee J.J. A DNA-based method for rationally assembling nanoparticles into macroscopic materials. Nature 1996 382 607-609. 

The analogy drawn between -stacked solids and duplex DNA has provided a useful starting point for experiments to probe and understand DNA-medi-ated CT. As with the -stacked solids, the DNA base pair array can provide an effective medium for long range CT. Mechanistically, however, the differences between DNA and these solid state materials may be even more important to consider. Duplex DNA, as a molecular -stacked structure, undergoes dynamical motion in solution. The time-dependent and sequence-dependent structures that arise serve to modulate and gate CT. Indeed in probing DNA CT as a function of sequence and sequence-dependent structure, we may better understand mechanistically how CT proceeds and how DNA CT may be utilized. 

An additional opportunity that arises from applying polymer-based materials is the preparation of water-dispersible composites, which is an essential feature for biomedical purposes, as it is possible to attach bio-active molecules to the poly-mer/CNTs systems and specifically deliver them to cells. In this manner, plasmid DNA, siRNA (Fig. 3.11) and several anticancer agents have been successfully bound and delivered [61]. The stratagem to generate materials with good solubility in aqueous media usually involves the presence of water-soluble polar groups (e.g. phosphates, protonated amines etc.) embedded in the polymer chain. 

The development of new transducing materials for DNA analysis is a key issue in the current research efforts in electrochemical-based DNA analytical devices. The use of platinum, gold, indiiun-tin oxide, copper solid amalgam, mercury and other continuous conducting metal substrates has been reported [6]. However, this chapter is focused on carbon-based materials and their properties for immobihzing DNA by simple adsorption procedures. 

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