Biomedical Engineering Reference
In-Depth Information
(a)
10 µm
(b)
10 µm
2 µm
Aperture size = 30.00 µm
Signal A = SE2
Keck SEM
WD = 8 mm
File name =106.tif
EHT = 2.00 KV
Date : 24 Mar 2009
Time : 21 : 27 : 47
Mag = 2.00 K X
FIGURE 5.5
Scanning electron microscopic images of two representative hybrid hydrogel fabricated from
(a) Phe-based unsaturated AA-UPEAs, and poly(ethylene glycol) diacrylate (PEGDA) and (b) Arg-based unsatu-
rated AA-UPEAs and pluronic acid diacrylate.
copolymer approach. Chu et al. recently reported two different copolymer means to provide pendant
functional groups via either l-lysine or other amino acid co-monomer (Jokhadze et al., 2007; Deng et al.,
2009, 2011). The first copolymer approach led to the AA-PEA copolymers having pendant-free carbox-
ylic acid (located in the Lys block) over a wide range of desirable concentrations (Jokhadze et al., 2007).
These free carboxylic acids provide the reactive sites for the attachment of biologically active agents,
such as nitric oxide derivative, and the resulting AA-PEA copolymers would have biological activity and
intelligence similar to that of nitric oxide (Lee and Chu, 1996, 1998).
The second copolymer approach used a new monomer of ε-(benzyloxycarbonyl)-amino acid-
N
-
carboxyanhydride (Z-amino acid-NCA) and its ring-opening reaction with the regular AA-PEA
O
O
CH
2
Ph
NH
R
1
O
R
2
+
O
N
H
HS
O
CH
2
Ph
O
n
FPB or F3EG
O
O
DMA
70°C, 24 h
CH
2
Ph
NH
R
1
O
O
N
H
S
O
CH
2
Ph
O
n
FIGURE 5.6
Chemical scheme to illustrate the synthesis of pendant functional AA-PEAs from the unsaturated
>C
∙
C< bonds in the AA-UPEA backbone. (Adapted from Guo, K. and Chu, C.C., 2010.
J. Appl. Polym. Sci
. 117(6):
3386-3394.)
