Biomedical Engineering Reference
In-Depth Information
Fig. 6 Encapsulation of hydrophobic nanoparticles in micelles
micelles. With this elegantly simple procedure, one obtains a water-soluble particle
of small size, which can easily be functionalized by just mixing the appropriate lipids.
A representation of the encapsulating procedure for hydrophobic nanoparticles in
micelles is shown in Fig.
6
.
Lipids are mixed with the nanoparticles in an apolar solvent. The mixed film
obtained is hydrated. Thereafter, the nanoparticle-containing micelles and empty
micelles are separated by centrifugation.
6.1.2 Peptide-Conjugated Nanoparticles
Several peptide-conjugated nanoparticles have been synthesized by researchers for
targeted delivery into the cell and cellular organelles. Inspired by viruses,
Tkachenko and coworkers conjugated peptides to bovine serum albumin (BSA)
via an ester linker, and then conjugated the BSA to gold nanoparticles [
45
]. The
four peptides they used were from viral cell entry or targeting proteins, and they
were able to achieve targeted entry of the gold nanoparticles into the nucleus of
HepG2 cells. Furthermore, it should be noted that the cells were still viable after
entry of the gold nanoparticles. Nitin et al. developed a similar approach for
solubilizing iron oxide [
46
]. They conjugated TAT peptides and a fluorescent
label to the distal end of the PEG chains of the phospholipids to coat the iron
oxide particles. The TAT peptide has been shown to deliver nanoparticles into cells,
making it attractive for intracellular labeling. The uptake of this conjugate was
demonstrated in vitro with both MRI and fluorescence microscopy. Another study
showed the intracellular delivery of peptide-conjugated QDs. The authors selected
an insect neuropeptide, allatostatin (AST1; APSGAQRLYG FGL-NH
2
), conju-
gated it to CdSe
ZnS QDs, and investigated the intracellular delivery of the
conjugate in living cells such as human epidermoid ovarian carcinoma cells
(A431) and mouse embryonic fibroblast cells (3T3) [
47
], as shown in Fig.
7
.
Figure
7
a shows a fluorescence image of A431 cells incubated with a 5
m
M
