Enzymatic, physicochemical and biological properties of
MMP-sensitive alginate hydrogels
Keila B. Fonseca,
F. Raquel Maia,
Filipe A. Cruz,
Maria A. Juliano,
Pedro L. Granja
and Cristina C. Barrias
Protease-sensitive hydrogels that recapitulate the mechanisms of cell-driven enzymatic remodelling of the
natural extracellular matrix (ECM) have been gaining popularity as arti
cial 3D cell-microenvironments.
Here, the matrix metalloproteinase (MMP)-sensitive peptide Pro-Val-Gly-Leu-Iso-Gly (PVGLIG) was
double-end grafted to alginate forming water-soluble PVGLIG
alginate conjugates. The PVGLIG peptide
was synthesized as a Fluorescence Resonance Energy Transfer (FRET) sensor and showed to be a good
substrate for MMP-2, MMP-9, MMP-13 and MMP-14. After demonstrating that human MSC (hMSC)
expressed both MMP-2 and MMP-14 under basal and osteogenic
conditions, the e
ect of 3D-
culture within MMP-sensitive alginate hydrogels on hMSC behaviour was addressed.
alginate hydrogels containing only cell-adhesive RGD peptides (RGD
alginate, MMP-insensitive) or both
alginate, MMP-sensitive) were used. Cell
matrix and cell
cell interactions were
enhanced in hMSC-laden MMP-sensitive alginate hydrogels, as compared to MMP-insensitive hydrogels
with identical viscoelastic and microstructural properties. hMSC underwent osteogenic di
both types of matrices. However, the presence of PVGLIG stimulated the secretion of proteases (most
likely MMP-2) by hMSC, in both undi
erentiated and di
erentiated cultures. By using the FRET sensor, it
was possible to demonstrate that the cocktail of hMSC-secreted MMPs was e
ectively active in cleaving
microenvironments and o
er promise as injectable carriers for therapeutic hMSC-delivery.
gel-forming hydrogels, such as alginate, o
not only as 3D models for
mechanistic studies but also
as injectable vehicles for the therapeutic delivery of cells and/or
Alginate hydrogels can be formed under cyto-
compatible conditions, giving rise to highly hydrated and
permeable 3D networks with tuneable viscoelastic properties.
Alginates are intrinsically non-fouling, lack cell-adhesion
signals and cannot be cleaved by mammalian enzymes, but
possess a number of reactive functional groups that can be
chemically derivatized to enhance their biological properties.
This, in turn, makes alginates excellent
for engineering biofunctional derivatives, namely through the
incorporation of cell-signalling moieties.
The incorporation of ECM-like peptides on the polymer
backbone is among the strategies most used to promote cell
interactions with hydrogels.