DNA Nanotechnology and Drug Delivery - DNA Nanotechnology: From Structure to Function - page 321

Fig. 15.10 DNA nanorobot for targeted drug delivery. To fabricate the nanorobot by DNA
origami, a long single-stranded DNA scaffold is folded into the shape of a hexagonal barrel by
short oligonucleotide “staple” strands. The assembled nanorobot consists of two aptamer-encoded
locks, a barrel-shaped body and a bound molecular cargo. The use of two different aptamers that
“unlock” when exposed to two antigens results in an AND logic gate, meaning that the nanorobot
opens in the presence of the correct combination of antigen keys. The molecular payload is then
released to bind to target cells and activate signaling pathways (Reprinted by permission from
Macmillan Publishers Ltd: Nature biotechnology, Ref. [ 20 ], copyright 2012)

release the inside payloads (Fig. 15.10 ,Ref.[ 20 ]). The payloads are loaded to the
inside of the barrel by covalently linked to the 5 0 end of the single DNA linker

strands at designed positions.
To examine the nanorobot's close and open function, they loaded fluorescently
labeled antibody Fab 0 fragments inside the barrel, which specifically bind to human
leukocyte antigen (HLA)-A/B/C. For the aptamer locks, six combinations of three
well-characterized aptamer sequences (41t, against platelet-derived growth factor
(PDGF); TE17; and sgc8c) were created. These nanorobots were incubated with
different cell types expressing human HLA-A/B/C. When a cell expresses the two
correct “key” protein antigens, the barrel will be opened, and the fluorescently
labeled antibody Fab´ fragments will bind to the cell, which can be monitored by
the increase of the fluorescence signals on the cell surface. Their results showed that
this barrel-shaped nanorobot with aptamer locks could be used for cell targeting.
They also investigated their nanorobot application on interfering with cell
signaling pathways. Nanorobots loaded with antibody to human CD33 and antibody
to human CDw328 Fab 0 fragments were used to induce growth arrest in leukemic
cells. The suppression of Jun N-terminal kinase (JNK) and Akt (protein kinase B)
signaling were observed. Another set of nanorobots with antibody to human CD3 ©

Fab 0 and antibody to flagellin Fab 0 as payloads were mixed with T cells and found

to induce activation.
This multifunctional DNA origami nanorobot structure represents big step along
the way to develop controllable targeting drug delivery systems, though it is still to
be proved that this nanorobot structure can be stable, and this aptamer-lock control
system can still work inside the cell environment.