Biomedical Engineering Reference
In-Depth Information
tumor drug delivery exist owing to the heterogeneity of tumor vasculature,
particularly at the centre of poorly differentiated cancers, as well as particle
detection and uptake by the RES. PEGylation represents the most com-
mon method of reducing RES uptake, producing a hydrated barrier caus-
ing steric hindrance to the attachment of phagocytes. GNPs have also been
used for cancer cell imaging and targeting. In various clinical trials the 27-nm
citrate-coated GNPs bound with thiolated PEG and tumor necrosis factor-a
(TNF-a) (CYT-6091) (Aurimmune; CytImmune Sciences, Rockville, MD)
has shown an increase of tumor targeting [127]. An important feature of
GNPs is their capacity to absorb and scatter specific wavelengths of light
across the visible and near-infrared (NIR) spectrum. The most useful nano-
shells have a silica core diameter of around 120 nm, with a 10 nm layer
of gold shell, and they absorb NIR light (800 nm) and can create intense
heat lethal to cells. An in vivo study demonstrated that 100nm gold nano-
shells maximally accumulated in SK-BR-3 human breast tumors 24 h after
intravenous injection. When a laser tuned to the nanoshell resonance was
applied, average tumor temperatures increased by 9uC in control mice, and
37uC in nanoshell-treated mice, with irreversible tissue damage in the nano-
shell group. All mice in the nanoshell group survived 90 days with no evi-
dence of tumor recurrence [128]. Positive results in vivo, were also obtained
with photothermal ablation therapy in a mouse model for colon carcinoma
after intravenous administration of PEG coated gold nanoshells [78]. The
GA-GNPs (GNPs stabilized by gum arabic (GA) is used for diagnostic
and therapeutic applications, showing optimal in vitro and in vivo stabil-
ity. The compound is nontoxic, distributes minimally to non-target organs
in biodistribution studies, and produces contrast on CT imaging [129].
A study group has shown an approach for imaging and targeting cancer
cells using dendrimer entrapped GNPs (G-DENPs). G-DENPs, which
when covalently linked to folic acid and fluorescein isothiocyanate mol-
ecules are stable, hydrophilic, biocompatible, and able to specifically bind to
cancer cells that over-express high-affinity folate receptors. The folic acid-
conjugated nanoparticles are subsequently endocytosed into lysosomes
of cancer cells, providing a means for targeting and imaging of these cells
[130]. An interesting new therapeutic strategy foresees the connection of
antibodies-nanoshells is able to target cancer cells by interacting with specific
surface antigen expressed only by tumor cells. The benefit of the nanoshell-
mediated approach is that the energy can pass through the healthy tissue
and leave the neighboring cells intact while killing only the tumor cells that
have been targeted by the nanoshells.
Silver nanoparticles (SNPs) are part of the emerging nanotechnology
that have gained increasing interest in the field of nanomedicine due to their
particular properties and therapeutic potential in treating a large variety of
disease [131-132]. The biological activity of silver has been attributed to
the presence of the Ag+ ion. SNPs inhibit the vascular endothelial growth
