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     Volume 1 Issue 16 | November 26, 2006 |


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Medical Feature

The Golden Death of Cancer
Once you choose hope, anything's possible. -Christopher Reeve

Rim Sabrina Jahan Sarker

Science always seeks for hope. It never gives up. Everyday, science is getting closer to finding a cure for cancer. But treatment process often causes serious side effects. This urges for a side effect free cancer treatment. Recently in a case like this, nanotechnology turned out to be a cool solution. Nanotechnology has become an umbrella term these days. It covers many areas of research dealing with objects measured in nanometers. With the help of this brand new technology, scientists may now be able to destroy tumors without killing healthy cells at the same time.

Like a Trojan horse
Researchers at the Georgia Institute of Technology and the University of California, San Francisco have discovered a safe and effective way to detect and kill cancer cells. They choose gold as their nano weapon. Gold particles have been in medical use for fifty years. Colloidal gold was used in searching for cancerous lymph nodes. But our new age hi-tech nano gold is far more efficient than it used to be previously.

A nanometer (nm) is a billionth of a meter, or a millionth of a millimeter. Most animal cells are 10,000 to 20,000 nanometers in diameter. Researchers are using gold nanoparticle of 1/5000th thickness of a human hair. This means that it can enter cells and cell organelles inside them to interact with DNA and proteins. The system uses a light sensitive drug and gold nanoparticles. This drug-nanoparticle complex kills cancer cells in a process called “photodynamic therapy” (PDT). In many countries PDT is used in cancer treatment. When light strikes the drug, it damages only the cancerous cells.

But the latest version of PDT uses a drug named pthalocyanine. It is a dye involved in our daily life. The blue jeans we wear or the ballpoint pen we use, contain this common dye. But what is the catch in this apparently ordinary looking blue dye? Well, here is the thing, it is an agent that can be activated using light and has cell-destructive properties. It only acts inside the cell. Therefore, there is no harm in wearing blue jeans. So denim lovers, relax!

Lets know a bit more about Pthalocyanine. It is an aromatic compound and resembles porphyrin rings found in chloroplasts and hemes in hemoglobins. Like porphyrins, it can bind several metal ions in its central cavity. In recent days, gold nanoparticle is proved to be a good metal ion. This “Trojan horse” actually guides the dye. It is very small in size as mentioned earlier and this tinyness helps it to easily enter cells and pthalocyanine is taken up along with nano gold particle. When activated with laser light, the drug produces a highly reactive oxygen species (ROS), which causes massive oxidative damage in the targeted cancer cells. But illuminating the nano particles may seem a little hard because red light can travel only 5-6mm through the tissue. Fiber optic cable solves this problem. It can be used to shine the laser on the cancer cells so that the particles get activated and start killing tumors inside the body.

Capturing the culprits
Is there any way to distinguish between normal cells and cancerous ones? On the surface, cancer cells have a trademark protein known as epidermal growth factor (EGFR). In contrast, genes in healthy cells usually do not contain these proteins. On binding to an antibody of EFGR, the gold nano particles attach themselves to the cancer cells only. And unlike cancer cells, normal cells just excrete the drug. Exposing the cells to the optimum amount of light kills the cells and leaves the healthy cells alone. Scientists have found that to be killed, malignant cells need less than half of the energy needed by the benign cells. Plus there is no light driven destruction in absence of the nanoparticles. So definitely, nanotechnology rules!

Typical photodynamic therapies may trigger side effects in exposure to sunlight.

Pthalocyanine does not get into the skin. So it is unnecessary for the patient to stay out of the sun. It only acts inside the cell. Moreover, this compound is optimized for activation by red light.

Nano cure is knocking on the door
Gold may be an expensive metal but a few cents worth of gold makes the technique simple and inexpensive. A team of scientists in Italy has begun testing the technique in animal models of cancer. Researchers think it holds a big promise in detecting and curing cancer. Success came in oral cancers but in near future gold nano particle may turn out to be a valuable tool in curing stomach and skin cancers. Nanotechnology is currently in various stages of discovery and development but in a few years, it is going to have a revolutionary impact on cancer treatment, no doubt.

Rim Sabrina Jahan Sarker
3rd year , Genetic Engineering & Biotechnology , University of Dhaka




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