Biomedical Engineering Reference
In-Depth Information
Fig. 10 Preparation of antigen-encapsulating nanoparticles by w/o/w emulsion method
the protein phase. Protein stability may also be enhanced if the protein is
encapsulated as a solid rather than in solution.
We have recently found that nanoparticles consisting of amphiphilic poly(amino
acid)s can efficiently and stably encapsulate various types of protein into the
nanoparticles. Protein-loaded
g
-PGA-Phe nanoparticles were prepared by encapsula-
tion, covalent immobilization, or physical adsorption methods in order to study their
potential applications as protein carriers [
96
,
97
]. To prepare the protein-encapsulating
g
-PGA-Phe nanoparticles, proteins with various molecular weights and isoelectric
points were dissolved in saline, and the
g
-PGA-Phe dissolved in DMSO was added to
the protein solutions. The resulting solutions were then centrifuged and repeatedly
rinsed (Fig.
11
). The encapsulation of proteins into the nanoparticles was successfully
achieved. All proteins used in this experiment were successfully encapsulated into the
nanoparticles. The encapsulation efficiency was found to be in the range of 30-60%
for most samples. For all samples tested, it was observed that the encapsulation
efficiency for a given protein was not markedly influenced by the physical properties
of that protein. Ovalbumin (OVA) encapsulated into the nanoparticles was not
released (less than 10%) over the pH range of 4-8, even after 10 days. Moreover, it
was found that the
g
-PGA-Phe nanoparticles have some excellent properties.
The enzyme-encapsulating nanoparticles showed high enzymatic activity. In the
case of protein-encapsulating nanoparticles prepared by the self-assembly of
g
-PGA-Phe, the encapsulated protein may be more stable than via the emulsion
method. Proteins encapsulated into the nanoparticles appear to be adequate in terms
