Biomedical Engineering Reference
In-Depth Information
tumor cells. In this study, a drug release test showed that the amount of doxorubicin
released from nanoparticles decreased with increasing pH and the release profile exhib-
ited a sustained pattern. Therefore, this pH-responsiveness may benefit cancer treatment
via the RME mechanism.
6.6.3.3 Physical Targeting
As mentioned above, some environmental factors such as pH and temperature can be used
as signals for targeting application. Here, another interesting physical targeting signal,
magnetic signal, has attracted more and more attention recently. Magnetic nanoparticles,
composed of a magnetic (e.g., iron oxide) core and a biocompatible polymeric shell (e.g.,
chitosan), are an effective DDS of this kind. The particles encapsulate drugs and can be
targeted to a desired treatment location by externally localized magnetic steering [151].
For example, magnetic targeting chitosan nanoparticles were prepared through the elec-
trostatic interaction of cationic chitosan and the negatively charged core that was com-
posed of Fe
3
O
4
nanoparticles [151]. A photodynamic therapy (PDT) agent, namely the
photosensitizer, was physically entrapped in the magnetic chitosan particle by adsorption
in order to develop an
in vivo
chitosan-based magnetic DDS for magnetic resonance imag-
ing (MRI)-monitored targeting PDT. The magnetic particles were administered to tumor-
bearing mice followed by exposure to an externally localized magnetic field (1 T). The
results showed that the drug-loaded nanoparticles could be used in MRI-monitored tar-
geting PDT with excellent targeting and imaging ability. Moreover, it was shown that non-
toxicity and high photodynamic efficacy on SW480 carcinoma cells were achieved, and
localization of nanoparticles in skin and hepatic tissue was significantly less than in tumor
tissue due to the magnetic targeting effect.
The example above just shows the targeting ability of the chitosan-based magnetic DDS.
Drug release from this type of DDS has also been investigated. Shen and coworkers [152]
developed chitosan-coated magnetic nanoparticles containing 5-fluorouracil through a
reverse microemulsion method, as a potential DDS. The resulting nanoparticles released
their drugs in a sustained manner under
in vitro
conditions. After FITC labeling, the drug-
loaded chitosan-based magnetic nanoparticles were found to effectively gain entry into
the SPCA-1 cancer cells and induce cell apoptosis.
6 . 7 A p p l i c a t i o n
Chitosan-based hydrogels have been used to deliver a variety of drugs, including some
molecules, macromolecules, or even therapeutic cells, for treating special disease or regen-
erate tissues. The drugs have been loaded in chitosan gels to various sites in the human
body for oral, rectal, ocular, epidermal, subcutaneous, and other applications. The litera-
ture on hydrogel formulations for pharmaceutical applications is reviewed in this section,
according to the sites of administration of the drugs.
6.7.1 Drug Delivery in the Oral Cavity
Drug delivery to the oral cavity can have versatile applications in local treatment of dis-
eases of the mouth, such as fungal and viral infections, periodontal disease, stomatitis,
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