Biomedical Engineering Reference
In-Depth Information
of this, few of the interesting morphogenetic signals involved in develop-
mentinteractwithfibrininaspecificmanner.However,fibringlueiswidely
used for wound closure and has been shown to be a suitable delivery vehi-
cle for exogenous growth factors that may in the future be used to accelerate
wound healing [85]. Although the regenerative capacity of the organism is
not activated in pure fibrin matrices the addition of heparin or engineered
adhesion and growth factors incorporated into the fibrin matrix during co-
agulation has been thoroughly studied as a promising means to modulate the
morphogenetic characteristics of this temporary matrix. Thus, fibrin received
a lot of attention in the design of engineered or biohybrid matrices distin-
guished by a rather high rate of turnover and a readily tuneable variety of
characteristics.
Altogether, a variety of ECM assemblies has been structurally elucidated
and some of those became available through in vitro reconstitution. Cell-free
reconstitution provided a wealth of supramolecular ECM mimics which, how-
ever, often base on one enzymatically processed biopolymer component—
such as collagen I—only while others may deviate in structure and compo-
sition in a unknown fashion from their natural templates (as, for instance
the basement membrane precipitates from laminin and collagen IV isolated
from the Engelbreth-Holm-Swarm tumor). Although successfully used in
different cell culture experiments, the model characteristics of biopolymer
assemblies obtained via cell-free reconstitution are limited with respect to
ECM occurring in living matter. The use of cell-driven ECM reconstitution in
vitro, in particular the formation of cell-secreted multicomponent assemblies,
and the detailed comparison of structures resulting from both cell-driven
and cell-free reconstitution with those present in living organisms may cer-
tainly open new options to further advance the model characteristics of ECM
assemblies.
4
Matrix Assembly and Functionality at Polymer Surfaces
Having considered the formation of supramolecular associations between
ECM biopolymers in vitro the question of factors influencing this process in
artificial settings is emerging. While the choice of the biopolymers to be com-
bined as well as the conditions of their precipitation (absolute and relative
concentrations, solution pH and electrolyte composition, temperature, shear
force, electrical fields and other physical factors) obviously trigger ECM re-
constitution another, often underestimated aspect, concerns the presence of
solid surfaces interacting with the ECM biopolymer prior to and/or during
assembly.
Several recent examples demonstrate the importance of the modulation of
ECM assemblies by their interaction with the surfaces of solid substrates. As
