Biomedical Engineering Reference
In-Depth Information
electrons with molecular oxygen [142]. Further
in cellulo
studies of photo-
induced cytotoxicity toward A172 glioma cells in the presence of selective
ROS quenchers were consistent with these results [139]. Nanostructured
porous TiO
2
has been developed as a biocompatible nano-device for con-
stant chemotherapy drug release into the CNS [141]. A porous titania car-
rier uploaded with low concentrations of a cytostatic platinum complex was
capable of inducing DNA fragmentation, possibly via a strong interaction
between nitrogen atoms in nucleotides, and Lewis acid sites on both the ti-
tania surface, and the platinum complex coordination sphere. Application of
this material directly on to C6 glioma xenografted into Wistar rats resulted
in a significant decrease in tumor size and growth rate.
5.6 Magnetic nanoparticles
MRI is one of the most frequently-used, non-invasive imaging tools for dis-
ease diagnosis and monitoring, including cancer. Imaging techniques that can
selectively image proliferating cells in vivo, can provide critically important
insights into tumor growth rate, degree of tumor angiogenesis, effectiveness
of treatment, and vigor of normal cells. Contrast agents that are commonly
used in clinical practice for the brain and spinal cord MRI are based on
gadolinium. However, a major problem associated with MRI is its low sen-
sitivity. Utilization of nanotechnology to improve the sensitivity and efficacy
of MRI for cancer detection and imaging is an area that researchers have
focused on in the last several decades. Magnetic NPs, used in biomedical
applications mainly, have an inorganic nanoparticle core and in most cases
are coated by a suitable coating material. Suitable coatings not only increase
the stability and solubility of the nanoformulation, but can also be used to
incorporate a targeting moiety to increase the imaging sensitivity and to do
real-time monitoring. Enhanced proton relaxation is one of the most added-
value properties that make magnetic NPs one of the best contrast agents
for biomedical applications of MRI. Iron oxide and superparamagnetic iron
oxide-(SPIO) NPs exhibit magnetic properties, which are used for MRI
imaging and also provide an opportunity to control particle transport by
external magnets. Superparamagnetic iron oxide contrast agents either form
the core of magnetic NPs that have a polymeric coating, or are more ho-
mogeneously integrated into polymeric NPs [100]. The signal intensity of
these NPs is related to the size of the particle, its position, its concentration
within a given voxel, data acquisition parameters, the magnetic field, and
the dosage of the SPIO-NP [75]. SPIO-NP has been used as a bowel con-
trast agent (Lumerin, Gastromark) and for spleen/liver imaging (Endorem,
Feridex). Macrophage-specific uptake of SPIO-NPs increases the contrast
between healthy and diseased tissue because most liver tumors are devoid of
it. Negative enhancement effects of SPIO-NPs on T1/T2-weighted MRI
sequences, allowed increased lesion conspicuousness and increased lesion
detection as compared to non-enhanced imaging. It is well documented
