a
c
b
R
R
R
Cl
Cl
O O
O O
O
O
O
O
O
O
O
O
O O O
O
Cl
Cl
NH 3
NH 3
H 3 N
H 3 N
H 3 N
NH 3
NH 3
NH
3
NH 2
NH 2
NH 2
NH
NH 2 H 2 N
H 2 N
H 2 N
H 2 N
1 R = NH(C=NH 2
+
)NH 2 ,Cl
–
2 R = CH 2 NH 3
+ Cl –
H 3 N
NH
NH
NH HN
HN
HN
NH
HN
HN
Cl
Cl
Cl
Cl
Cl
Cl
Cl
HN
R
–
–
Cl
–
–
–
–
–
–
–
–
–
–
+
+
+
+
+
+
+
+
+
+
+
+
Fig. 12 (a) Structure of calix[4]arenes 1, 2, and 3. (b) AFM images showing DNA folding by
calixarene 1. (c) Transfection efficiency in various cell lines of calixarene 1 (red) compared with
calixarene 1 with DOPE (peak), calixarene 2 (blue), calixarene 2 with DOPE (cyan-blue),
Lipofectamine (gray), and PEI (light gray) [58]. (Reproduced from Ref. [58] with permission
from the Nature Publishing Group)
218
J. Gao and D.-S. Guo