Biomedical Engineering Reference
In-Depth Information
photosensitizers are exposed to this specific wavelength, they produce singlet oxygen, which destroys
cancer cells. Targeted cancer therapy uses target-specific drugs that invade cancer cells and block the
growth and metastasis of cancer cells by interfering with specific molecules involved in carcinogen-
esis and tumor growth
[13]
. To overcome the disadvantages of current cancer treatment techniques,
the scientific community has turned toward nanotechnology to develop newer and more effective drug
carrier systems to safely shepherd the anticancer drugs to the cancer cells.
19.3
MECHANISM OF ACTION OF CHEMOTHERAPEUTIC AGENTS
In general, anticarcinogenic chemotherapeutic agents can be divided into three main categories based
on their mechanism of action
[14]
.
19.3.1
Prevention of Synthesis of Pre-DNA Molecule Building Blocks
DNA building blocks are folic acid, heterocyclic bases, and nucleotides, which are formed naturally
within cells. All of these agents work to block some steps in the formation of nucleotides or deoxyri-
bonucleotides (necessary for making DNA). When these steps are blocked, the nucleotides, which are
the building blocks of DNA and RNA, cannot be synthesized. Thus, the cells cannot replicate due to
impaired DNA synthesis. Examples of drugs in this class include methotrexate, fluorouracil, hydroxy-
urea, and mercaptopurine.
19.3.2
Chemical Damage of DNA in the Cell Nuclei
Some chemotherapeutic agents destroy DNA and RNA of cancer cells. They disrupt the replication
of DNA and totally halt the replication of DNA or RNA, which may stimulate cancer cell formation.
A few examples of drugs in this class include cisplatin and antibiotics such as daunorubicin, doxo-
rubicin, and etoposide. Disruption of synthesis or breakdown of mitotic spindles serve as molecular
railroads with “north and south poles” in the cell when it starts to divide. These spindles are very
important because they help split the newly copied DNA such that a copy goes to each of the two new
cells during cell division. These drugs disrupt the formation of these spindles and therefore interrupt
cell division. Classic examples of drugs in this class of mitotic disrupters include vinblastine, vincris-
tine, and paclitaxel.
19.4
ORAL CANCER
Oral cancer or cancer of the mouth, a subtype of head and neck cancer, encompasses any cancerous
tissue or growth located within the oral cavity. It may arise as a primary lesion originating in any of
the oral tissues, by metastasis from a distant site of origin, or by extension from a neighboring ana-
tomic structure, such as the nasal cavity or the maxillary sinus. Oral cancer may originate in any of
the tissues of the mouth, and may be of varied histological types: teratoma (true neoplasms composed
of multiple tissues foreign to the site from which they originate), adenocarcinoma derived from a
major or minor salivary gland, lymphoma from tonsillar or other lymphoid tissue, or melanoma from
