Biomedical Engineering Reference
In-Depth Information
overcome the current challenges in cancer therapies. One such challenge, for instance, involves tar-
geting and site specificity. The development of functionalized and multifunctionalized drug deliv-
ery carriers allows for active and passive targeting. One common approach is normally based on
the pathophysiology of diseased sites, such as leaky vasculatures in cancer tissues (Ferrari 2005).
Owing to its nanosize, NMs can modify the biodistribution and pharmacokinetic characteristics of
the anticancer drug considerably as compared to the free drug. These nanoscale materials can rec-
ognize biomarkers or detect mutations in cancer cells and treat the abnormal cells by
1. Thermotherapy, including photothermal ablation therapy using silica nanoshells, carbon
nanotubes (CNTs), magnetic field-induced thermotherapy using magnetic NPs, photody-
namic therapy by QDs as photosensitizers, and carriers for controlled and targeted release
2. Nanostructured polymer NPs, dendrimers, and nanoshells for cancer chemotherapy
3. Radiotherapy using CNTs and dendrimers for boron neutron capture therapy
1.4.1.5 Local Anesthetic Toxicity
Local anesthetics can be very toxic, ranging from local neurotoxicity to cardiovascular collapse and
coma. Aside from conventional therapies, drug-scavenging NPs have been shown to considerably
enhance the survival in treated animals (Renehan et al. 2005, Weinberg et al. 2003).
1.4.1.6 Gene Therapy and Transfection
Gene therapy occurs when a normal gene is inserted in place of an abnormal, disease-causing
gene by using a carrier molecule. Conventional applications of viral vectors normally produce
adverse immunologic and inflammatory reactions, as well as diseases in the host. NMs have pres-
ently come forward as potential vectors of effective and promising tools in systemic gene therapy.
Different polymeric NPs, such as chitosan, gelatin, poly-l-lysine, and modified silica NPs, have
been researched to have an increased transfection efficiency and decreased cytotoxicity. It is well
noted that NMs provide feasible options as ideal vectors in gene therapies.
Surface-functionalized NPs can be used to infuse cell membranes at a much higher level than
NPs without surface functionalizations (Lewin et al. 2000). This property can be used to transport
genetic material into living cells through transfection. Silica nanospheres, tagged on their outer
surfaces with cationic ammonium groups, can bind anionic DNA through electrostatic interactions
(Kneuer et al. 2000). Subsequently, the NPs transport the DNA into cells.
1.4.1.7 Molecular Diagnostics and Imaging
Molecular imaging is the nanoscience that deals with demonstrating, characterizing, and quantify-
ing subcellular biological processes in intact organisms. These processes are composed of gene
expression, protein-protein interactions, signal transduction, cellular metabolism, and intracellular/
intercellular trafficking. Some NPs that have intrinsic diagnostic properties are QDs, iron oxide
nanocrystals, and metallic NPs. They have been effectively employed in magnetic resonance, opti-
cal, ultrasonic, and nuclear imagings (Wickline and Lanza 2002). Several other applications of
NPs in diagnostics include the selective labeling of cells and tissues, long-term imaging, multicolor
multiplexing, the dynamic imaging of subcellular structures, fluorescence resonance energy transfer
(FRET)-based analysis, and magnetic resonance imaging (MRI). FRET and MRI are two major
diagnostic approaches that have been developed for molecular-level diagnostics. Conventional MRI
contrast agents, such as paramagnetic and superparamagnetic materials, are now being replaced by
various novel nanocarriers, such as dendrimers, QDs, CNTs, and magnetic NPs. They are estab-
lished as very efficient contrast agents, offering more stable, intense, and clearer images of objects
due to a high-intensity photostability and resolution, and a resistance to photobleaching. A few
approved NP applications in imaging and as drug carriers are listed on Table 1.3.
In addition, different, “noninvasive” systems have been widely used for more than a quarter
of a century in the field of medical imaging. For example, superparamagnetic magnetite particles
