Biomedical Engineering Reference
In-Depth Information
Figure 9.21.
Activation of carboxylic acid of DBC by employing DCC/NHS
andsynthesisofHA-DBCandreductionofitsdisulfidebondstoobtainHA-
BC-L-benzoyl-cysteine; DBC,
tetra-
butylammonium hydroxide (TBA-OH),
5,5-
di
-thio-bis(2-nitrobenzoicacid) (DTNB).
66
•
Oxidation-based
in situ
hydrogels
Another type of
in situ
HA hydrogel for tissue engineerings such as
regenerationofintervertebraldiskwasobtainedbyoxidation-based
auto-cross-linkingofHAbyusingsodiumperiodate. FabioSalvatore
Palumbo
et al.
synthesizedauto-cross-linkingHAhydrogelshavinga
fibril structure (Fig. 9.21).
66
The activation of the carboxylic groups
of
N
,
N
-dibenzoyl-L-cystine (DBC) was performed with the activa-
tors NHS and dicyclohexylcarbodimide. The solution of DBC-NHS
was reacted with HA-tetrabutyl ammonium (TBA) in the presence
of a catalyst (see Fig. 9.21). After reduction of the -S-S- bridges to
-SH groups with a reducing agent(DTT), HA-benzoylcysteine (HA-
BC)wasobtainedandsolutionsofHA-BCwereautomaticallyturned
into an HA gel viaoxidation mechanims.
66
,
67
•
Michael-type reaction method
Fabrication of
in situ
HA hydrogels via the Michael-type reaction
mechanism is well-known chemistry,
30
and it is carried out over
time by employing the end-group reaction between unstaurations
and thiol groups of HA (Fig. 9.22).
26
−
32
While the HA-NH
2
or HA-
acrylate has been obtained by using ADH by the cross-linking with
bis(sulfosuccinimidyl) suberate or methacrylated HA (HA-MA) or
acrylated HA, the HA with thiol groups (HA-SH) were synthesized
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