Biomedical Engineering Reference
In-Depth Information
Degradation
Possible intermolecular intraction between carrier matrix and growth factor
Electrostatic
Carrier matrix
Growth factor
Hydrogen bond
Hydrophobic
FIGURE 14.3
Mechanism on the controlled release of growth factor.
subcutaneous implantation of the gelatin hydrogels incorporating BMP-2 into the back of mice, the
in vivo
release of BMP-2 was prolonged by decreasing the water content of the hydrogels used,
however, regardless of the water content the gel preparations provided a prolonged release, unlike
the BMP-2 solution injection. Thus, ectopic bone formation studies have demonstrated that alka-
line phosphates activity (ALP) and osteocalcin content (OCN) around the implanted site of BMP-2-
incorporated gelatin hydrogels were significantly high compared with those around the injected site
of BMP-2 solution. The values reached maximum for the gelatin hydrogel incorporating BMP-2 with
a middle period of BMP-2 retention, while bone formation was histologically observed around the
hydrogel incorporating BMP-2. Controlling the release of BMP-2 over a certain period of time may
be essential to induce the potential activity for bone formation
[46]
. Same materials have been used
to regenerate bone at a skull defect of nonhuman primates. A critical-sized defect (6 mm in diameter)
was prepared at the skull bone of cynomolgus monkeys skeletally matured while gelatin hydrogels
incorporating various doses of BMP-2 were applied into the defects. When the bone regeneration was
evaluated by soft X-ray examinations, the gelatin hydrogel incorporating BMP-2 exhibited signifi-
cantly high osteoinduction activity. The gelatin hydrogel enabled BMP-2 to induce the bone regen-
eration in nonhuman primates
[47]
.
Table 14.2
summarizes research reports of BMP-2 release for
ectopic bone formation.
Our recent study has indicated that a three-dimensional network of self-assembled nanofibers was
formed by mixing of bFGF suspension with aqueous solution of peptide amphiphile as an injectable
carrier for controlled release of the growth factors to study the feasibility of prevascularization in
improving the efficiency of tissue regeneration
[48]
. The bFGF incorporated in self-assembled pep-
tide could be delivered to living tissues by simply injecting a liquid (i.e., peptide amphiphile solu-
tions) and bFGF solution. The injected solutions would form a solid scaffold at the injected site of
