bm3013692_si_001.pdf (1.05 MB)
Synthesis and Characterization of a Matrix-Metalloproteinase Responsive Silk–Elastinlike Protein Polymer
journal contribution
posted on 2013-03-11, 00:00 authored by Joshua
A. Gustafson, Robert
A. Price, Jordan Frandsen, Corinne R. Henak, Joseph Cappello, Hamidreza GhandehariSilk-elastinlike protein polymers
(SELPs) are recombinant
polymers
consisting of tandem repeats of silk (GAGAGS) and elastin (GVGVP)
units. By modification of the length and composition of these repeats,
the properties of SELP hydrogels can be controlled for specific applications
including nucleic acid and virus delivery and tissue engineering.
Here, the structure of SELPs is further modified to include a sequence
that
is sensitive to matrix-metalloproteinases (MMPs). MMPs are a ubiquitous
family of extracellular matrix-modifying enzymes that are commonly
associated with numerous vital processes. Increased levels of MMPs
are found at high levels locally in many types of solid tumors. By
modifying the SELP backbone with MMP-sensitive peptide sequences,
a hydrogel that is degradable by MMPs was produced. The MMP-sensitivity
of the polymer was examined by incubation with MMP-2 and MMP-9, which
yielded complete cleavage of all full-length polymers by 36 hours
and 48 hours, respectively, with no observable effect on unmodified
SELP. Hydrogel sensitivity was tested by exposure to MMP-2 or MMP-9
for 2 weeks, during which samples were taken to analyze protein loss
from the hydrogel and release of 100 nm fluorescent beads. Following
the incubation period, hydrogels were tested in mechanical compression
to examine the loss of hydrogel stiffness due to degradation. It was
found that MMP-2 and MMP-9 caused 63% and 44% increased protein loss
and 65% and 95% increased release from MMP-sensitive hydrogels, while
the compressive modulus decreased by 41% and 29%. These results suggest
the potential of MMP-responsive SELPs for localized delivery of bioactive
agents where MMPs are overexpressed.