Biomedical Engineering Reference
In-Depth Information
Bone fill 2 weeks
60.000%
50.000%
40.000%
30.000%
20.000%
10.000%
0.000%
FIGURE 19.6
Bone fill in rat calvarial defects. Rat calvarial defects were filled with either GEM21
s
(300
g/mL PDGF in
sterile water mixed 1 to 1 with solid TCP), DFDBA, Capset
s
(medical-grade CS), BMP (1500
μ
μ
g BMP-2/mL
deposited on a collagenous sponge matrix), nCS alone, nCS
A10 (nCS with 10% alginate), nA10
B
1
1
(nCS
10% alginate
BMP-2 [900
μ
g/g nCS]) and nA10
P (nCS
10% alginate
PDGF-BB[180
μ
g/g
1
1
1
1
1
nCS]), nA50
B (nCS
50% alginate
BMP-2 [900
μ
g/g nCS]), nA50
P (nCS
50% alginate
PDGF-BB
1
1
1
1
1
1
[180
g/g nCS]). The controls were nonfilled defect. There were four animals/treatment group. The mixtures
of alginate and nCS increased the bone fill compared to nCS alone. The bone fill was significantly greater with
the combination of nCS
μ
alginate and BMP-2 compared to GEM21
s
, DFDBA, but was not significantly
different than with BMP-2 applied on a collagenous sponge.
1
significant differences between control and Capset
s
, GEM21
s
and nCS. However, there were
significant increases compared to control with DFDBA, BMP-2 alone and all nCS samples that
included BMP-2. It is also interesting to note that the combination of nCS with alginate resulted in
greater bone fill than nCS alone and comparison of the samples treated with nCS to those with
Capset
s
did show a greater fill with nCS although at this time period, neither resulted in signifi-
cantly greater effects compared to untreated controls. It can also be observed that under these
conditions, PDGF-BB either added as a part of the GEM21
s
treatment or with the nCS did not pro-
duce increases in bone fill. This experiment suggested that a combination of nCS with alginate
might enhance the bone-filling properties of the material at least with respect to some critical bone
defects sites and lead to further studies on the manner in which alginate might be modifying the
properties of the nanomaterial.
Alginate, a natural polysaccharide extracted from brown sea algae, has been extensively used in
various aspects of tissue engineering because it is biocompatible, hydrophilic, and biodegradable
under normal physiological conditions
[58]
. It forms stable hydrogels in the presence of certain
divalent cations (e.g., Ca
2
1
) in low concentrations
[59]
. When scaffolds containing alginate are
placed in a liquid milieu, there is uncontrolled degradation of ionically cross-linked alginate due to
loss of divalent cations. This leads to formation of pores inside the scaffold. In the in vivo experi-
ment described above, alginate was added to nCS powder to induce in situ pore formation and
