DNA Nanotubes

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Made almost entirely of DNA, tubes might be useful for gene therapy

The first layered nanotubes composed almost entirely of DNA have been

created. Layers of DNA in the nanotubes are held together by

hybridization of a series of DNA strands. The nanotubes fall apart

when heated, releasing single-stranded DNA.

The nanotubes were synthesized and characterized by chemistry

professor R. and coworkers Shifeng Hou and Jiahai Wang

at the University of Florida, Gainesville (J. Am. Chem. Soc.,

published online May 25, dx.doi.org/10.1021/ja042343t). " These

nanotubes might prove to be the ultimate DNA delivery vehicles--for

treatment of genetic-based disorders, for example--because the

nanotubes are essentially all DNA, " says.

DNA TUBE Cross-sectional view of DNA nanotube with exploded view of

nanotube wall.

The DNA nanotubes are constructed in the 100-nm-diameter pores of

alumina membranes. A diorganophosphonate " skin " is deposited in the

pores, and Zr(IV) is used to link the diorganophosphonates to

phosphonate groups on the end of a single-stranded DNA strand. The

strand's sequence is partially complementary to that of a second

single-stranded DNA, and thus the two strands can hybridize.

Similarly, the second DNA strand hybridizes with a third DNA strand.

The resulting cylindrical assemblies--three layers of DNA plus the

linkers and skin--are then released by dissolution of the template,

yielding nanotubes made almost entirely of DNA.

The paper focuses primarily on nanotubes made from 15-base DNA

strands, but and coworkers also can prepare nanotubes from 8-

and 12-base DNAs. " The DNA molecules composing these tubes can be

varied at will, " they note.

" I have not seen similar approaches based on template construction of

DNA nanotubes in which the DNA can eventually be liberated from the

support, " comments associate researcher Alberto Bianco of the

Institute of Molecular & Cellular Biology at the French National

Center for Scientific Research in Strasbourg.

In previous work, researchers have made DNA-containing nanotubes by

depositing DNA on a substrate and then functionalizing the DNA in

various ways. But in the new nanotubes, the DNA content is more

predominant, and 's approach " allows better control of the DNA

nanotube structure, " says Bianco, whose research interests include

carbon nanotube biofunctionalization.

The new nanotubes " could act as vehicles to deliver the DNA of which

they are composed, " Bianco says. " In general, DNA does not cross cell

membranes easily, and as a result, rates of transfection

[incorporation of DNA into genes] are very low. Methods to improve

transfection are based on the formation of complexes between DNA and

suitable carriers, such as liposomes, dendrimers, cationic polymers,

and, more recently, carbon nanotubes. "

The new DNA nanotubes could make it possible to transfer DNA without

separate carriers, but this would necessitate " that these tubes are

able to cross the cell membrane and reach the nucleus, " which has yet

to be demonstrated, Bianco notes.

http://pubs.acs.org/cen/news/83/i23/8323notw8.html