DNA Nanotechnology and Drug Delivery - DNA Nanotechnology: From Structure to Function - page 311

still have not made significant clinical impact on human health. Developing novel
biocompatible, multifunctional drug delivery nanocarriers remains the key for the
application of nanotechnology on drug delivery [ 1 ].
DNA 3D nanostructures [ 2 ] have the promising properties to be ideal targeted
drug delivery nanocarriers:

1. The biocompatibility of the DNA molecules
2. Robust self-assembly process through Watson and Crick base-pairing interac-
tions
3. Designable and controllable precise 3D structures with addressable modification
sites
4. Simple attachment methods for cell-targeting ligands, imaging agents, drugs, and
nucleic acids

Plus, the commercially available synthetic DNA oligonucleotides make the 3D DNA
nanostructures cost effective and suitable for scale-up process.
Recently, several research groups had done great exploratory works on utilizing
several DNA 3D nanostructures on drug delivery applications. Though some loose-
formed DNA structures, like Y-shape DNA-based structures [ 3 ], have also been
explored as drug delivery carriers, in this chapter, we will focus on DNA 3D
structures made from robust DNA motifs through structural DNA nanotechnology.

15.2 DNA Nanotube as Drug Delivery Nanocarrier

The first DNA 3D nanostructure was studied for drug delivery application is a
DNA nanotube by Mao's group [ 4 ]. The DNA nanotube they used has a diameter
of 50-200 nm and lengths up to 40 m, which is formed by a single 52-base

DNA strand, which consists of four palindromic segments. In their work, organic
fluorescence dye Cy3, chosen as a model drug, was chemically attached to some
of the DNA nanotube forming strands; and folate, using as cell-targeting ligands to
target folate receptors (FRs) overexpressed on the surface of various cancer cells
(including the nasopharyngeal epidermal carcinoma KB cells they used for their
experiment), also was conjugated to other separated DNA strands. After nanotube
formation and incubation with FR-overexpressing KB cells, the dual-functionalized
DNA nanotubes will bind to the cell through folate-FR interaction and transfect into
the cell (Fig. 15.1 ,Ref.[ 4 ]).
For cell uptaking measurement, after incubating their dual-functionalized DNA-
NTs with the FR-KB cells, they compared fluorescence images of the cells before
and after washing the cell surface and treating them with DNase I, those treatments
will remove any Cy3 molecules outside the cell surfaces. Their results clearly
showed that the DNA nanotubes bound to the targeted cell surfaces, and some of
them entered inside the cells. Cytotoxicity test proved that DNA nanotubes are
biocompatible, as no significant cell death was observed.