Benefits for Treatment and Clinical Outcomes
Cancer therapies are currently limited to surgery, radiation, and chemotherapy. All three methods risk damage to normal tissues or incomplete eradication of the cancer. Nanotechnology offers the means to aim therapies directly and selectively at cancerous cells.
Conventional chemotherapy employs drugs that are known to kill cancer cells effectively. But these cytotoxic drugs kill healthy cells in addition to tumor cells, leading to adverse side effects such as nausea, neuropathy, hair-loss, fatigue, and compromised immune function. Nanoparticles can be used as drug carriers for chemotherapeutics to deliver medication directly to the tumor while sparing healthy tissue. Nanocarriers have several advantages over conventional chemotherapy. They can:
- protect drugs from being degraded in the body before they reach their target.
- enhance the absorption of drugs into tumors and into the cancerous cells themselves.
- allow for better control over the timing and distribution of drugs to the tissue, making it easier for oncologists to assess how well they work.
- prevent drugs from interacting with normal cells, thus avoiding side effects.
There are now several nanocarrier-based drugs on the market, which rely on passive targeting through a process known as "enhanced permeability and retention." Because of their size and surface properties, certain nanoparticles can escape through blood vessel walls into tissues. In addition, tumors tend to have leaky blood vessels and defective lymphatic drainage, causing nanoparticles to accumulate in them, thereby concentrating the attached cytotoxic drug where it's needed, protecting healthy tissue and greatly reducing adverse side effects.
On the horizon are nanoparticles that will actively target drugs to cancerous cells, based on the molecules that they express on their cell surface. Molecules that bind particular cellular receptors can be attached to a nanoparticle to actively target cells expressing the receptor. Active targeting can even be used to bring drugs into the cancerous cell, by inducing the cell to absorb the nanocarrier. Active targeting can be combined with passive targeting to further reduce the interaction of carried drugs with healthy tissue. Nanotechnology-enabled active and passive targeting can also increase the efficacy of a chemotherapeutic, achieving greater tumor reduction with lower doses of the drug.
Destruction from within
Moving away from conventional chemotherapeutic agents that activate normal molecular mechanisms to induce cell death, researchers are exploring ways to physically destroy cancerous cells from within. One such technology—nanoshells—is being used in the laboratory to thermally destroy tumors from the inside. Nanoshells can be designed to absorb light of different frequencies, generating heat (hyperthermia). Once the cancer cells take up the nanoshells (via active targeting), scientists apply near-infrared light that is absorbed by the nanoshells, creating an intense heat inside the tumor that selectively kills tumor cells without disturbing neighboring healthy cells. Similarly, new targeted magnetic nanoparticles are in development that will both be visible through Magnetic Resonance Imaging (MRI) and can also destroy cells by hyperthermia.