Biomedical Engineering Reference
In-Depth Information
Histological analyses were performed on tissues obtained from the clearance
organs (kidney, spleen, and liver), in order to investigate the toxicity (if any) of
the nanoparticles. No apparent toxicity was reported in the tissues of animals
receiving the nanoprobes, when compared to normal mice receiving no injection.
The mice injected with nanoprobes were also tested for any physical and/or
neurological acute toxicity associated with nanoprobe administration. For this,
the accumulation and retention of the targeting nanoprobe in the tumor and
surrounding normal tissues were evaluated at intervals of 0, 0.3, 2, 12, and 24 h
post-injection, the aim being to quantify nanoprobe accumulation and to defi ne
the time window when animals could be imaged so as to achieve maximum
MRI contrast, as well as to gain an understanding of the pharmacokinetics of
the nanoprobe. A high targeting specifi city and a benign biological response, as
were established by this nanoprobe, might represent a potential platform to aid in
the diagnosis and treatment of gliomas and other tumors of neuroectodermal
origin.
Veiseh
et al
. [100] prepared magnetite nanoparticles with a PEG coating, and
subsequently functionalized these with CTX and the fl uorescent molecule, Cy5.5.
The nanoparticle-CTX conjugates were seen to target glioma tumor cells, with
internalization into the cells being visualized by confocal imaging. The reported
T
2
relaxation times (5 ms for CTX-coated particles, 95 ms for non-coated) showed
much promise for glioma detection, and also demonstrated an affi nity of these
nanocomposites for glioma cells over healthy tissues.
6.3.2
MNPs Used in Optical Imaging for Cancer Diagnosis
A number of magnetic nanoparticle preparations have been developed over the
past decade for cancer staging, angiogenesis imaging, and the tracking of immune
cells (monocyte/macrophage, T cells), and also for molecular and cellular targeting
[103], by utilizing MRI. However, increasing reports during the past few years have
shown that MNPs conjugated to optically active fl uorescent molecules (magneto-
fl uorescent) have become important tools for
in vitro
and
in vivo
imaging, using
magnetic resonance and fl uorescent optical methods. A combination of magnetic
and optical imaging into a nanostructured system would greatly benefi t the
in vivo
disease diagnosis, as well as the
in situ
monitoring of responses of living cells
[104 - 107] .
One of the major attractions of magnetic nanoparticles is they can be easily
functionalized to provide additional properties so as to form a multifunctional
platform or scaffold. These include drug molecules, fl uorescent compounds, and
various hydrophobic and hydrophilic coatings. Fluorescent organic dyes have been
used extensively in biology for labeling and staining various markers; examples
are DAPI, Mitotracker and Hoescht dyes, all of which have been used to label
cellular features. Although, the association of magnetic and fl uorescent fl uoro-
phore-linked MNPs has provided an attractive dual-imaging scaffold, the synthetic
procedure has required multistep chemical treatments in order to conjugate
