Nanoparticles: The golden (cancer) treatment

Amanda Edward
17 October 2013

Above: Human lymphoma tumor cells (Dr. Lance Liotta Laboratory)

Your image of a typical cancer patient might be someone who has lost all their hair. Indeed, conventional chemotherapy involves administering drugs that kill all rapidly dividing cells inside your body, including cancer, hair, and skin cells. It’s a bit like dropping dynamite into a river to catch a fish: everything in the area of the explosion is killed, even if all you really wanted was one small fish for dinner.

Did you know? Gold nanoparticles were originally studied as a treatment for heart disease.

The potential of gold nanoparticles as a treatment for lymphoma was discovered accidentally! As a result, researchers are looking into more precise treatments, ones that actively target cancer cells while leaving other cells unharmed. Nanotechnology is at the forefront of this search for better cancer treatments. For example, gold nanoparticles are currently being researched as a possible treatment for B-cell lymphoma, a type of blood cancer. Nanoparticles are extremely small, ranging in width from 1 to 100 nanometers (nm).

A nanometer is one billionth of a meter. If you took a strand of your hair and cut it lengthwise between 80,000 and 100,000 times, you would end up with something about the width of a nanometer. The period at the end of this sentence is about 1,000,000 nm wide. Most viruses are between 10 to 100 nm wide, and bacteria range in size from 100 to 1000 nm.

B-cell lymphocytes (or B-cells) are an important part of your immune system. They identify antigens, which include toxins or other foreign substances, and remember how to deal with antigens they’ve encountered before. B-cells “tag” antigens with specific antibodies that may simply deactivate them, causing the foreign invaders to clump together. B-cells may also tag antigens with antibodies that tell the “killer” T-cells in your blood to mount an attack.

For example, B-cells are the reason why most people only get chicken pox once in their lifetime. When the chicken pox virus tries to infect you a second time, your B-cells recognize it as a foreign threat and send T-cells, a type of white blood cell, to destroy it.

However, when B-cells start dividing uncontrollably, they become cancerous lymphoma cells. Lymphoma cells survive on a type of cholesterol known as high-density lipoprotein (or HDL). HDL is found naturally in our bloodstream. Depriving lymphoma cells of HDL causes them to starve to death.

Did you know? High-density lipoprotein (HDL) is known as “good” cholesterol.

High-density lipoprotein helps remove “bad” cholesterol—low-density lipoprotein (LDL)—from the bloodstream.This is exactly what the gold nanoparticle is engineered to do: it locates cancerous lymphoma cells, enters only those cells, removes all HDL already present, and prevents any additional HDL in the bloodstream from entering.

Researchers have designed the gold nanoparticle’s surface using polymers so it resembles HDL in terms of size, shape, and chemistry. That way, cancer cells readily absorb the nanoparticles as though they were HDL. The cancer cells have specific receptors for HDL, and the gold nanoparticles fit into the receptors like a key in a lock. Once inside, the nanoparticles absorb HDL just like a sponge absorbs water.

The nanoparticle’s golden core—a cluster of gold atoms approximately 5 nm in diameter—is what prevents additional HDL from being absorbed. The nanoparticle occupies the area where HDL would normally bind to the cell. In other words, it blocks the keyhole, preventing any more HDL from being absorbed. It is as if someone came into your home, ate all your food, and stood in the doorway to prevent any new food from ever entering again.

As a result, the lymphoma cells essentially starve to death. Gold is well suited to this task, since it is non-toxic to human cells and gold nanoparticles are relatively easy to synthesize (engineer in a lab).

Although researchers are still studying possible side effects, the beauty of this treatment is that it actively targets lymphoma cells without harming other kinds of cells. Many other new forms cancer treatment, such as polymer-based drug delivery systems, also aim to specifically target cancer cells. The days of non-specific chemotherapy treatments and their many side effects may very well be numbered.

References

General information

New Way to Kill Lymphoma Without Chemotherapy: Golden Nanoparticle Starves Cancer Cell to Death (Science Daily)

Scholarly publications

Baker C, Sternby S. 2013. Gold Nanoparticles in Cancer Treatment. University of Pittsburgh, Swanson School of Engineering, Paper # 3005. Serpe L. 2006. Conventional Chemotherapeutic Drug Nanoparticles for Cancer Treatment. Nanotechnologies for the Life Sciences. Volume 6, Section 1. Vilar G, et al. 2012. Polymers and Drug Delivery Systems. Current Drug Delivery. 9:1-28. Yang S, et al. 2012. Biomimetic, Synthetic HDL Nanostructures for Lymphoma. PNAS Early Edition.

Amanda Edward

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