Biomedical Engineering Reference
In-Depth Information
logical adhesive and a space-filling scaffold [219]. The space-filling property
of chitosan is mainly attributed to its adhesive property [216, 219], ability
to accelerate wound healing [217, 219], and excellent immunological activ-
ity [220]. For instance, photocrosslinked chitosan hydrogels have been used
previously to seal pin holes in the small intestines, aorta, and trachea of
mice [219].
Matrigel : The matrigel matrix (commercially available from BD Bio-
sciences) is a soluble form of basement membrane extracted from mouse
tumors that contain several components of ECM proteins. The major compo-
nents of matrigel include laminin, collagen 1V, heparan sulfate proteoglycans,
and entactin. At room temperature, matrigel polymerizes to produce bio-
logically active hydrogel resembling the mammalian cellular basement mem-
brane. Cells are known to behave as they do in vivo when they are cultured in
matrigel matrix, and hence matrigel has been used as a model system to study
cell behavior in a 3D environment [221]. Matrigel indeed provides a phys-
iologically relevant environment for studying cell morphology, biochemical
function, cell migration and invasion, and gene expression. Therefore, ma-
trigel has been used to culture a wide variety of cells [72, 77]. In the case
of rhesus monkey ES cells, the use of matrigel has been shown to induce
cell growth and differentiation [222]. In another study, Xu et al. showed that
the presence of matrigel along with mouse fibroblast conditioned medium
maintains human ES cells in an undifferentiated state in a feeder-free culture
system [223].
Silk : In contrast to other natural materials, silk scaffolds are mechanically
robust, and have been used in the medical field as suture materials for cen-
turies. Silk obtained from both silkworm ( Bombyx mori ) and dragline spider
( Nephilia Clavipes ) has been extensively studied for decades. Spider silk has
drawn a lot of attention from various fields due to its exceptional mechani-
cal and thermal properties. The modulus and tensile strength of spider silk
fibers are very much comparable to some of the strongest man-made fibers
such as Kevlar [224]. An interesting aspect about silk fiber is that it is cre-
ated under mild conditions in contrast to the severe processing conditions
used to manufacture man-made strong fibers [224]. According to Lele et al.
the magnificent strength of the spider fiber is attributed to strong hydrogen
bonding between the protein chains [225]. Silk fibers differ in structure and
properties depending upon their source [226]. Silks are characterized by sec-
ondary structure such as
-sheets which renders good mechanical properties
to them. Because of the fact that we can now genetically manipulate the amino
acid sequence of silk to achieve targeted properties, several researchers have
attempted to exploit this material for various biomedical applications includ-
ing tissue engineering. The protein engineering techniques have also been
employed to scale up the production of silk and to also control its structural
organization [227].
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