Biomedical Engineering Reference
In-Depth Information
It has been proven by Wang and co-workers
[35], that two high
molecular weight factors, brain-derived neurotrophic factor (BDNF)
and vascular endothelial growth factor (VEGF), can be loaded
by poly(lactic-
co
-glycolic acid) microspheres and then embedded
in HA hydrogels for controlling the release of the factors. In this
way the microspheres carrying different factors together with HA
hydrogel scaffolds act as a delivery system for the construction of
a desired environment for promoting the survival and growth of
NSC, both
in vitro
and
in vivo
. Also, Wang and co-workers have
created a hyaluronan/methyl cellulose hydrogel for the local release
of erythropoietin, and this has been injected into the brain to induce
endogenous neural stems or progenitor cells from the SVZ in rodent
stroke models [36].
1.3.2 Delivery of Antibody against Neurite Outgrowth
Inhibitor Receptor
It is well known that the lack of axonal regeneration in the CNS
is accounted for by the myelin-derived axon outgrowth inhibitors,
including Nogo, myelin-associated glycoprotein (MAG) and
oligodendrocyte myelin glycoprotein (OmGP), and these inhibitors
interact with the Nogo receptor (NgR) on the axon growth cone and
subsequent trigger growth cone collapse, and then lead to a significant
axonal outgrowth inhibition. It follows therefore, that the axonal
regeneration may be promoted after CNS injury, if the NgR is blocked
by using antibodies to block the interaction with the outgrowth
inhibitors, as reported by GrandPré and co-wokers [37, 38].
The NgR antibody can be covalently attached to a HA hydrogel by
a hydrolytically unstable hydrazone linkage, and this modified HA
hydrogel can serve as an antibody releasing system for grafting into
the injured brain [39]. By use of this system in rodent stroke models,
the distribution of the antibody and differentiation of neurons in
the injured area can be seen, accompanied by certain behavioral
recovery [40]. There has been a study by Wei and co-workers [41]
showing that HA hydrogels modified with poly(L-lysine) (PLL) and
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