Golden Medicine: Use of Plasmons for Cancer Therapy

Cancer is an immensely complex disease to treat. The number of mutations and combinations of mutations that can lead to its development make each “cure” more of a patch to a few specific cases. Couple that with the increasing rate of mutation within cancer cells, and it becomes difficult to even diagnose the issue. Plasmon therapy offers the potential for a broadly applicable treatment, and because it couples well with the bodies immune response, offers a therapy that could decrease the chance for metastatic tumor development.

Before we discuss this topic with greater specificity, a few terms should be defined. Plasmons, from the word plasma, are a material that has electrons that flow back and forth in a wave when light shines on them. Plasmas are just gaseous ions, like lightning or neon signs, and in the case of a plasmon, this plasma is confined to the surface of a nanoparticle. You can read more about plasmon theory here.

Nanoparticles abound in modern technologies and are defined by one dimension, the so called “critical dimension”, which is around two hundred nanometers. For reference, that’s roughly one hundred thousand times smaller than a human hair. This size can afford a variety of unique properties to a molecule: distinct colors, uncharacteristic electronic activities, and even the ability to move through a cellular membrane. All these attributes will come into play in how these molecules interact with cancer cells, so they’re important to keep in mind.  Plasmons are nanoparticles that are so small, that the plasma on the surface can be manipulated by light. This rapid movement of plasma gives rise to heat as it collides with surface particles just as your hands generate heat rubbing together. The type of light that does this can be visible or even radio waves, meaning that very low-energy and harmless beams can be used to generate this rapid heat.

The second bit of background knowledge necessary for this discussion is: how is cancer treated in the first place? Many current cancer therapies come from small molecules roughly the size of glucose. Whether they use metals or strictly carbon, small molecule cancer therapies usually rely on interrupting one or a few cellular pathways, like DNA replication or a checkpoint before mitosis (cell splitting). One of the first nanoparticles approved for cancer therapy have been gold nanorods, which are thousands of times larger than a small molecule and have used physical rather than chemical mechanisms for therapy. To clarify, instead of changing some pathway in a cell, these nanorods can selectively heat cancer cells until the cell dies. If you were to think about this in terms of pest control, nanoparticle therapy is like burning a nest of cockroaches. In that same case, using small molecules like cisplatin would be like spraying the cockroaches with the latest bugkiller.

Extending this analogy, it’s fairly obvious that setting a fire inside someone’s body is not a good medicinal practice, so it would be fair to question how plasmon therapy might be helpful. There are two strategies for plasmon cancer therapy: precision lasers and radio waves which can pass through a body. The earliest use of plasmon cancer therapy used a fiber optic that was inserted under the skin to a location near the tumor. Then, beams of light would hit only the tumor. This has the advantage of targeted dosing, but can still be considered fairly invasive. Others have begun using plasmons that generate that intense heat with radio waves so that no procedure is necessary: simply an injection or ingestion of nanoparticles and then stepping into a radio transmitter This can be impractical if the tumor is not in a confined space. Common gold plasmonic nanoparticles would go inside all cells so healthy cells would be damaged just as easily as cancerous ones. Recent work shows that the surface of the nanoparticle can be changed so that the majority of uptake occurs by cancer cells. Cancer cell metabolism makes the charge of cancer cell membranes different from the charge of normal cell membranes, so these nanoparticles can exploit that difference to target only cancer cells.

With this targeted dosing, plasmons show promise as a noninvasive form of therapy that do not harm the patient and would be applicable to most forms of cancer. Even though the safest and most effective nanoparticles will use gold, treatment costs are currently around  $1000, thereby promising a treatment that will not be prohibitively expensive for the future.

Peer edited by Kasey Skinner.

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Nanotechnology in Your Sunscreen: Doing More Harm than Good?

While soaking in the sunshine may feel good, and you may have heard about solar ultraviolet (UV) radiation harm, you may not be aware of what’s in your sunscreen. Lee Hong explored the benefits of sunscreen in his post on The Pipettepen, and today, we dive deeper into a smaller world – the nanotechnology in our sunscreen.

The two minerals available to sunscreen in form of nanosized particles (NPs) are zinc oxide (ZnO) and titanium dioxide (TiO2). They are less than 1/1000th the size of a human hair. Bulkier minerals in traditional sunscreen reflect visible light, making it opaque and cakey on your skin. NPs on the other side, scatter light instead of reflecting it, resulting in a disappearing and lighter feeling sunscreen.

Traditional sunscreens block out UV rays but many with ghostly white color. Nanotechnology make them disappear on your face!

While the resulting nanoproduct can be a big help, people have raised concerns over the safety of NPs-based cosmetic sunscreens. With their smaller size, NPs could in theory be absorbed into the skin at a higher level than their bulkier counterparts. The real question to ask is if these tiny particles are more harmful if absorbed, than good in protecting us from UV rays.

Studies are divided about whether NPs can pass through the skin. A few reassuring words from Paul Wright, a toxicology researcher at RMIT University, “There’s a negligible penetration of sunscreen particles,” as he told The Guardian, “They don’t get past the outermost dead layer of human skin cells.” In 2017, the Australian Therapeutic Goods Administration (TGA) published its review that NPs absorption is unlikely, based on both via in-vitro (i.e. studies using isolated skin cells) and in-vivo (i.e. studies on live skin tissue) studies. It appears that we are in a safe zone!

Other scientists have tested on the toxicity of these tiny metal oxides when exposed to UV light, simulating the real-life scenario for use of sunscreens. Their results indicated that the metal oxides may generate reactive free-radical species, leading to cancer due to DNA damage. However, this alarming impact on human health depends on whether NPs in sunscreen are absorbed into our skin. Providing some comfort, research associate Simon James at the Australian Synchrotron told to The Guardian that “Our study demonstrates that the human immune system has the right equipment to remove any nanoparticles that somehow make it through the skin, assuming some do at all.” Their work showed that human natural defenses can gather and destroy ZnO nanoparticles. Moreover, sunscreen manufacturers utilize surface coatings to improve transparent effect and as a result, the coated components can essentially reduce toxicity from lessen reactivity to UV lights.

It’s not a bad idea shielding your skin from burning sun with an umbrella’s shade whenever you are up for outdoor activities.

With the increased popularity of the nanotech-based products, another concern is noxious effects caused by inhalation of NPs. The Environmental Working Group (EWG), based out of Washington, D. C., announced a warning to refrain from spray sunscreen and loose powder cosmetics containing ZnO or TiO2 particles. The lungs have difficulty removing small particles and thus end up with organ damage possibly in the same way that air pollution is linked to lung cancer.

Evidence suggests there is more harm from skipping the sunscreen than exposing your skin to nanoparticles, but, if you’re not comfortable with these tiny oxides, UV protection umbrellas are another option!

Peer edited by Bailey DeBarmore.

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Nanomedicine: How Much Are We Willing to Pay?

In 2013, cancer affected approximately 14 million people in the United States, and its  direct medical costs were almost $75 billion, making cancer a devastating disease from both the human and financial perspectives. Nanotechnology may offer some relief, but at what cost?  

Source: Christina Parker

Comparing nanotechnology expectations and reality in cancer treatment.

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