You don’t have to be a historian to grasp the significant impact gold has made in the world. From a sought-out treasure to a method of currency, there’s no doubt that this element is one of the most influential metals in human history. Yet, a much less known aspect of gold is its incredible potential in biomedicine. This is especially true of gold nanoparticles in the context of cancer.
Cancer is a condition wherein cells proliferate and divide in an uncontrolled manner. [1] While cancer can often be treated, the side effects of those treatments can be severe and can include possibly hurting non-cancer cells and the immune system. Inducing hyperthermia, or causing a part of the body to heat up, has been shown to have an anticancer potential as it can lead to programmed cell death as well as make tumors more susceptible to radiotherapy. Yet, a central issue arises: unless the heat is localized, other parts of the body can be harmed. This is where gold nanoparticles come in. [2]
In the simplest terms, gold nanoparticles are small pieces of gold. Very small pieces of gold. As a result, gold nanoparticles have a lot of different properties compared to, say, a block of gold that we often think about when talking about the element. For instance, gold nanoparticles are not yellow: particles less than 100 nm are red while bigger particles are blue/purple. [3] These nanoparticles have amazing properties which allow them to act as a contrast in CT scans or assist with drug delivery. [4] Yet, one of the most fascinating applications of these gold nanoparticles is their use in photothermal therapy. Because the blood vessels near the tumor site are often leaky, gold nanoparticles that have been placed in a cancer patient's body will passively concentrate near a tumor. Once they have concentrated, they can be activated by near-infrared light, a special type of light which can easily pass through human tissues. The gold nanoparticles will absorb the light energy and convert it to heat energy near the tumor, essentially stimulating the cancer cells’ deaths. [2]
Has this technique been tested in humans? In fact, yes–a clinical trial done at Mt. Sinai hospital which used gold-silica nanoparticles to treat prostate cancer patients revealed no severe side effects from the treatment. After the gold nanoparticles had concentrated at the tumor site of the patients, they were irradiated by near-infrared light from optical fibers. These nanoparticles absorbed the light and heated the tumor site, essentially destroying it. [5]
The promise of such a localized treatment strategy is encouraging. Hopefully, further research can be done to explore this opportunity that is, indeed, worth its weight in gold.
References
[1] Gupta, N.; Malviya, R. Understanding and advancement in gold nanoparticle targeted photothermal therapy of cancer. Biochimica et Biophysica Acta (BBA) - Reviews on Cancer [Online] 2021. 1875, 188532. https://www.sciencedirect.com/science/article/pii/S0304419X21000305?via%3Dihub (accessed November 2021)
[2] Vines, J.B.; Yoon, J.-H.; Ryu, N.-E.; Lim, D.-J.; Park, H. Gold nanoparticles for photothermal cancer therapy. Front. Chem. [Online] 2019. 7, 167. https://www.frontiersin.org/articles/10.3389/fchem.2019.00167/full (accessed November 2021)
[3] Sztandera, K.; Gorzkiewicz, M.; Klajnert-Maculewicz, B. Gold Nanoparticles in Cancer Treatment. Mol. Pharmaceutics [Online] 2019. 16, 1-23. https://pubs.acs.org/doi/10.1021/acs.molpharmaceut.8b00810 (accessed November 2021)
[4] Wang, S.; Lu, G. Noble and Precious Metals - Properties, Nanoscale Effects and Applications. In Applications of gold nanoparticles in cancer imaging and treatment; Intechopen: Online, 2017.
[5] Stephens, M. PhysicsWorld. https://physicsworld.com/a/gold-nanoshell-based-cancer-treatment-is-safe-for-the-clinic/ (accessed November 2021)
[6] Pxfuel. https://p1.pxfuel.com/preview/830/131/627/cancer-cells-cells-scan-electron-microscope-scan.jpg (accessed November 2021)
