Biomedical Engineering Reference
In-Depth Information
Gellan gum based microparticles reinforced with acryl solution, form hy-
drogels capable of proliferating the growth of nucleus pulposus (structure
which undergoes initial degradation of the intervertebral disc) in vitro
.
Hence, it is proposed to be a candidate strategy for inter vertebral disc
regeneration [31].
Recently, two EPS extracted from marine bacteria; HE800 (an acety-
lated EPS produced by
Vibrio diabolicus
)
or GY785 (a sulfated EPS pro-
duced by
Alteromonas infernus
) were used to prepare injectable hydro-
gels with silylated hydroxypropylmethycellulose (sHPMC) [70]. These
hydrogels showed proliferative activity in osteoblast cell line (MC3T3-1)
and chondrocyte cell line (C28/l2) in two and three-dimensional matrices
suggesting their use as scaffold for bone materials. This property is at-
tributed to the negatively charged groups like sulfate and acetyl on the
EPS which can react with the cationic proteins associated with growth
factors, cytokines and cell adhesion molecules [70]. The EPS, HE800 EPS
is functionally comparable to hyaluronic acid and shows strong bone heal-
ing properties in experimental rats [71]. It also shows proliferative activity
on nonmineralised connective tissues like skin, gum, cartilage and tendon
[72].
Chemical sulfation of EPS produced by
Alteromonas infernus
favors
bone resorption by inhibiting osteoclastogenesis and accelerating differ-
entiation of osteoblasts in vitro
in bone marrow stem cell (BMSC) and
murine RAW 264.7 cell lines. The activity is due to the sulfate groups
incorporated in the EPS, which enable the formation of a heteromolecu-
lar complexation with necrotic factor (NF-κB). This sulfated EPS depo-
lymerised by free radical depolymerization shows proliferative effects on
human umbilical vein endothelial cells (HUVEC) in vitro. It also shows
low anticoagulant activity and hence can be used to accelerate vascular
wound healing [16]. It is patented as a wound healing material for the con-
nective tissues, particularly skin and gum tissues [73].
8.2.6 EXOPOLYSACCHARIDES IN DRUG DELIVERY
Certain polysaccharides can form three-dimensional, hydrophilic, poly-
meric networks by chemical or physical cross-link to form structures
called hydrogel. Hydrogels are capable of imbibing large amounts of wa-
ter or biological fluids. This property together with the poor solubility of
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