Biomedical Engineering Reference
In-Depth Information
were, to a large extent, due to endocytosis via a receptor-mediated mechanism,
where the immobilized herceptin on the nanospheres targets the HER-2 receptors
on the cells. In order to investigate the competitive effects of free herceptin on the
endocytosis of herceptin-functionalized nanospheres, the seeded cells were fi rst
treated with a medium containing herceptin for 30 min, followed by replacement
with a medium containing herceptin-functionalized nanospheres and herceptin.
The results shown in Figure 10.6 indicate that, under such circumstances, the
uptake of herceptin-functionalized and nonfunctionalized nanospheres became
comparable. This in turn indicated that free herceptin in the medium would
bind to HER-2 receptors on the SK-Br-3 cells, and effectively prevent herceptin-
functionalized nanospheres from interacting with the receptors. TEM images of
SK-Br-3 cells cultured with herceptin-functionalized nanospheres, with or with-
out pretreatment and cotreatment with 200 mg ml
− 1
free herceptin, are shown in
Figure 10.7. For the former case, the image clearly shows the presence of endocy-
tosed herceptin-functionalized nanospheres (Figure 10.7a), whereas for cells pre-
treated and cotreated with herceptin (Figure 10.7b) only minimal nanospheres
were endocytosed. When cells were incubated with nonfunctionalized nano-
spheres, few or even no intracellular nanospheres were observed. Cytotoxicity
assays indicated an uptake-associated cytotoxic effect on the cancer cells, attribut-
able to a combined effect of bound herceptin and a higher uptake of herceptin-
functionalized PPY-MNPs nanospheres, with the consequence of a much higher
intracellular concentration of PPY as well as Fe
3
O
4
coated with sodium dodecyl
sulfate (which is used to aid the dispersion of MNPs in an aqueous medium for
the polymerization of pyrrole). While the herceptin- functionalized nanospheres
possess magnetic properties suffi cient to show promise as an agent for hyperther-
mia, the magnetization of the nanospheres was seen to be signifi cantly lower in
a fl uid medium than in the solid state. The diamagnetic nature of the cell environ-
ment also resulted in a diminished apparent magnetization.
(a)
(b)
3
µ
m
3
µ
m
Figure 10.7
Transmission electron microscopy images of cells
cultured with (a) NS-HER and (b) NS-HER pretreated and
cotreated with 200
μ
g ml
−
1
free herceptin for 4 h. Reprinted
with permission from Ref. [80]; © 2008, Elsevier.
