Biomedical Engineering Reference
In-Depth Information
6.3.2
TGase-Catalyzed Systems
Transglutaminase (TGase) is a family of enzymes whose function is
to form an amide linkage between the
γ
-carboxamide group of cer-
tain peptidyl glutamine residues and primary amines, such as the
ε
-amino group of lysine (Fig. 6.5).
47
-
51
These calcium-dependent
enzymes are ubiquitous in fluids and the ECM throughout the body,
forming cross-links in the skin, liver, and blood clots. Therefore, the
procedurecanbeadaptedtohumantherapeuticusethroughthecor-
rect choiceof a human-derived enzyme.
Gri
th prepared enzymatically cross-linked hydrogels for the
first time based on a poly(ethylene glycol) (PEG)-glutamine conju-
gateandsyntheticpeptidescontainingalysineresidue,catalyzedby
TGase.
52
He confirmed that the ratio and total concentration of the
macromers determine hydrogel formation and the gel properties,
suchasswellingratioandentanglementratio.Healsoexaminedthe
gelation kinetics of the PEG hydrogel.
53
Various types of PEG were
used to predict the gelation kinetics, and the gelation time was con-
trolled by varying the macromer and enzyme concentrations within
∼
10-60 minutes. Thompson prepared fibrinogen-based hydrogels
in situ,
using an interesting strategy that uses phototriggerable lipo-
someandTGase.Heutilizedthephotosensitivereleaseofentrapped
liposomal Ca
2
+
as an initiator of the TGase-mediated formation
of fibrinogen hydrogels. The gelation arose from TGase-catalyzed
cross-linking of predominately
α
and
γ
chains of fibrinogen. Gelatin
was also applied to TGase-catalyzed systems by two groups. Payne
et al.
prepared gelatin hydrogels catalyzed by TGase and character-
ized the mechanical properties and cell entrapment, even though
they targeted the microfluidic biosensor system.
54
Kobayashi
et al.
Figure 6.5.
Schemeoftheglutamine-lysinereactioncatalyzedbycalcium-
dependent TGase.
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